####018004534#### FXUS65 KFGZ 161706 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 1006 AM MST Fri May 16 2025 .SYNOPSIS...Seasonable temperatures and light winds forecast for today, before cooler and windier conditions return over the weekend. Slight chances for precipitation also expected Sunday and Monday. Warm and dry conditions look to return by the middle of next week. && .UPDATE...A nice quiet morning across northern and central Arizona with clear skies and warming temperatures. Expect generally light winds around 5-15 mph with gusts around 20-25 mph in spots. Only minor updates needed as the forecast looks right on track. && .PREV DISCUSSION /416 AM MST/...Today will look and feel very similar to yesterday, with daytime highs near average for this time of year and winds 5-15 mph out of the southwest. Are you tired of the windy weekends? Well...bad news...more gusty conditions are expected this weekend as a deep trough begins to descend from the Great Basin region. There has been some mixed opinions with model guidance on how this low pressure system will ultimately shake out, but there has been a clear and consistent signal that winds will increase out of the southwest Saturday and Sunday. Look for winds this weekend to be 15-25 mph, gusting 30-40 mph. The element where models are differing in their solutions is mostly the trajectory of this trough, which is impacting the potential for precipitation this weekend and early next week. Recent model runs are showing a slower on-set of the core of this low pressure system reaching Arizona, so showers now look to enter our CWA by late Saturday night/early Sunday morning, primarily across far northern AZ. We could see a second closed low push into the state on Monday, bringing showers as far south as the White Mountains. But there is still wavering confidence on how Monday will turn out in terms of precipitation. Taking into account the elevated winds and drier conditions for our southern/eastern zones, a Fire Weather Watch has been issued for the Little Colorado River Valley and White Mountains for Saturday afternoon. For Sunday afternoon, this Fire Weather Watch becomes limited to the Little Colorado River Valley in Apache County. Tuesday Onward...As the previously mentioned trough heads east, we'll start to see a quick return of warm/dry May weather. Daytime highs are forecast to reach 5-15 degrees above normal by the end of next week, with typical spring-like breezes each afternoon. && .AVIATION...Friday 16/12Z through Saturday 17/12Z...VFR conditions, though smoke could reduce visibility locally near and downwind of Greer (in eastern Arizona) and Blind fire (SE of KLFG). Winds becoming SW 5-15 kts with gusts to 20 kts by 15-18Z. Becoming light and variable after 03Z Saturday. OUTLOOK...Saturday 17/12Z through Monday 19/12Z...VFR conditions prevailing, though smoke could reduce visibility near and downwind of wildfires. Isolated to scattered -SHRA and a slight chance of -TSRA after 06Z Sunday mainly north of I-40. Winds Saturday and Sunday afternoons SW 15-25 kts with gusts to 30-35 kts. Patchy blowing dust in northeast Arizona. && .FIRE WEATHER...Today through Saturday...Dry conditions will continue with minimum RH values mostly below 15%. Southwest to west afternoon winds 10 to 20 mph today. Southwest winds increase on Saturday to 15-25 mph gusting 30-40 mph. Critical fire weather possible Saturday in the Little Colorado River Valley and White Mountains where a Fire Weather Watch is in effect. Sunday through Tuesday...Windy and cooler Sunday and Monday. A 20- 40% chance of showers north of I-40 Sunday and over most of northern Arizona Monday. Southwest winds 15-25 mph gusting 30-40 mph on Sunday, then west-northwest 10-20 mph on Monday. Critical fire weather possible Sunday in the eastern Little Colorado River Valley where a Fire Weather Watch is in effect. Warmer, less wind, and drier on Tuesday. && .FGZ WATCHES/WARNINGS/ADVISORIES... Fire Weather Watch from Saturday morning through Saturday evening for AZZ112>114-117-140. Fire Weather Watch from Sunday morning through Sunday evening for AZZ114. && $$ PUBLIC...Meola/Konieczny AVIATION...JJ FIRE WEATHER...JJ For Northern Arizona weather information visit weather.gov/flagstaff ####018014006#### FXUS63 KLOT 161708 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 1208 PM CDT Fri May 16 2025 .KEY MESSAGES... - A threat of rapid fire spread exists this afternoon due to a combination of strong winds and low relative humidity. - A threat of severe thunderstorms exists late this afternoon and early evening (Threat level 1 to 2 out of 5). && .MESOSCALE... Issued at 1208 PM CDT Fri May 16 2025 Main focus for severe thunderstorms late this afternoon and early this evening continues to be across my southeastern counties of eastern central IL into northwestern IN. This includes areas generally along and east of I-55 and along and south of I-80. Prior to the severe storm threat, strong gusty winds and low afternoon RH's will promote a high fire danger for portions of northern IL. Mainly clear skies and a parched airmass overhead is fostering deep boundary layer mixing that is allowing temperatures to quickly warm through the lower 80s as of 11 AM. Continued mixing of this very warm and dry boundary layer is expected this afternoon, likely mixing in excess 8,000 ft. This deep mixing will promote steady (or even falling) surface dewpoints in the 40s as surface temperatures warm into the middle to upper 80s, and will also result in increasingly gusty south-southwest winds through the day. The strongest wind gusts this afternoon and evening are generally expected along and northwest of the I-55 corridor, where gusts of 45 to perhaps as high as 55 mph are anticipated. This has prompted the recent issuance of a wind advisory for this area, as well as a targeted Red Flag Warning within portions of this wind advisory. While a parched and very deeply mixed boundary layer is not typically associated with storm development, we are expecting a rather impressive northward surge of low-level moisture (surface dew points up around 60) along and east of the I-55 corridor very late this afternoon (after 4 PM) and into the evening just in advance of an eastward shifting cold front/dryline feature. This corridor of better low-level moisture currently resides across southern MO and IL, and is noted by a late morning uptick in CU development on regional Satellite imagery. This increasingly moist and unstable airmass is expected to foster isolated to widely scattered thunderstorm development across parts of eastern MO and southwestern IL into early this afternoon. Thereafter, storm coverage is expected increase as large scale forcing for ascent increases in response to a notable mid-level impulse over the mid-Missouri Valley quickly swinging eastward along the southern periphery of the upper low residing in the Upper Midwest. As storm coverage increases, severe storms will develop northward across IL through the afternoon ahead of the dry line feature within the northward surging airmass. The area we are most concerned with for these severe thunderstorms are in areas generally along and east of I-55 and along and south of I-80, with the main timeframe looking to be from 4 to 10 pm this evening. More isolated storm coverage is possible northwest of this area. The presence of very steep low-to-mid level lapse rates and inverted V-type soundings with high DCAPE (in excess of 1,000 j/kg) will foster very strong downdrafts and outflow with these storms. Accordingly, the primary severe weather threat with this activity looks to be damaging winds, some perhaps destructive (75+ mph). Some instances of large hail also cannot be ruled out. Expect the storm threat to wane by mid to late evening as the cold front/dry line shifts east of the area. KJB && .DISCUSSION... Issued at 247 AM CDT Fri May 16 2025 Through Saturday: Two primary forecast concerns through early this evening, severe weather potential and windy, dry conditions for possible wildfires. Please see the fire weather section below. Much drier air has spread across western and northern IL with dewpoints in the upper 40s. The models are in good agreement with low level moisture surging back north late this afternoon into early this evening, with dewpoints back into the upper 50s to possibly lower 60s along and east of I-55. A cold front will be approaching from the west and scattered thunderstorms are expected to develop east of I-55. Coverage further north into the Chicago Metro area is more uncertain with perhaps only isolated thunderstorms. Strong winds aloft along with ample instability will allow any storms that develop to quickly become severe with large hail and damaging winds the main threats. Given the wind profiles in the soundings, isolated damaging gusts into the 60-65kt range will be possible. Before the storms, southwesterly winds will steadily increase this morning with gusts into the 40-45 mph range expected. There is a narrow window this afternoon, where gusts could frequently be at or above 45 mph, which is wind advisory criteria. Confidence is too low to issue a windy advisory at this time, but trends will need to be monitored. Gusts will diminish a bit this evening, into the 25-30 mph range but will remain gusty through sunset Saturday evening. Another period of higher gusts in the 35-40 mph is possible as the colder air spreads into the area late this evening. Previous forecast included patchy blowing dust for today for the western cwa and made no changes. There were stripes of heavier rainfall from the storms Thursday afternoon that will limit this potential for those areas. High temperatures today are expected to reach into the middle, to perhaps upper 80s for most locations. Wind directions may remain southerly enough to keep temps cooler along the north lakeshore. Low temps will drop into the lower/mid 50s Saturday morning. High temps will be cooler on Saturday ranging from mid 60s north to around 70 south. cms Saturday Night through Thursday: A sprawling ~1030 mb high will build east across Ontario and the Hudson Bay on Sunday with mid-level shortwave ridging forecast to build in across the local forecast area. This high to our north with send a robust afternoon and evening lake breeze/backdoor front through the entire region. This will end up holding lakeside highs in the mid/upper 50s, while inland locales will likely warm into the 70s prior to the lake breeze push. While some guidance hints at the potential for some intermittent lower cloud cover on Sunday, most indications are that any morning cloud cover should scatter into the afternoon. On Sunday night into Monday, a sharpening warm frontal zone well to our south will slowly advance northward into southern Iowa, northeast Missouri, and southern Illinois. Increasing low-level warm advection in response to strengthening 925-850 mb southwesterlies overtopping this frontal zone will lead to the development of showers and thunderstorms, but given the current location of the aforementioned boundary and MUCAPE gradient, most/all of this activity through Sunday night looks to remain well to our south. Even into the day on Monday any activity locally currently looks like it should remain isolated to scattered, with deeper moisture still relegated to our south. Forecast soundings off the GFS in particular look like they'd be more supportive of intermittent drizzle/showers as opposed to thunderstorms. On Monday night into Tuesday, guidance pushes a modest surface low (near 1000 mb) towards northern Missouri/southern Iowa as a robust shortwave pivots across the central plains. During this time, the northward progress of the returning warm front is forecast to slow, with the boundary overall becoming quasistationary across central to downstate Illinois. Isentropic upglide will increase once again, likely leading to a nocturnal expansion of showers and storms which--depending on the precise location of the stalled front--may begin to push into our forecast area, particularly south of about I-80. Could end up being a locally heavy rainfall threat somewhere in the vicinity with this setup. Thereafter, guidance generally depicts a complex upper pattern developing, with a series of upper lows/gyres pinwheeling around one another into the middle of the week. This general evolution will keep the threat for intermittent periods of rain with embedded thunderstorms going in the vicinity, at least into Wednesday. There's a signal for things to dry out into the end of the week. Carlaw && .AVIATION /12Z TAFS THROUGH 18Z SATURDAY/... Issued at 624 AM CDT Fri May 16 2025 The key aviation messages are: - Increasingly gusty south-southwesterly winds this morning and afternoon. There is some potential for non-thunderstorm wind gusts nearing 45 knots for a brief period this afternoon (about 20-23z). - Scattered thunderstorms develop during the late afternoon and early evening. Any storms that develop could produce wind gusts over 50 knots. PROB30s have been converted to TEMPOs. - Winds shifting to the WSW this evening and will remain gusty, with some potential for 30+ knot gusts through the overnight. - Threat for MVFR cigs late tonight/Saturday morning, but too low for a mention at this time. Light south to southwest winds will become increasingly gusty this morning into the afternoon. By mid-late afternoon, concern is that model guidance is under-advertising wind gusts given extremely deep mixing into very strong flow aloft. Have continued to slightly boost wind gusts with the latest TAF issuance. There is a potential for a brief period of non- thunderstorm wind gusts around 45 knots during peak heating if the deepest mixing advertised on some guidance is realized (about 20-23z). Additional scattered thunderstorms are expected to develop this afternoon and evening. In coordination with the CWSU, have converted the PROB30 groups to TEMPOs at all Chicago-area terminals. Any storms that develop today will be capable of producing damaging downburst wind gusts given the very deeply- mixed environment. Large hail is also a threat, but seems secondary to the wind threat. While the TAF remains "precip free" at RFD, there is about a 20-30 percent chance that high- based showers/storms also develop in the vicinity in the 20-23z timeframe. If this occurred, there would also be a threat for strong-severe wind gusts. This evening, a cold front will sweep across the region. Non- zero potential for additional showers/storms developing on this front, but currently thinking this is a lower chance (under 30 percent). SSW winds will veer to the W/WSW with the front with routine gusts to around 30 knots expected through the overnight, with a brief window where gusts could exceed 35 knots right as the front pushes through. VFR cigs should develop around 045 and lower gradually through the night, with a potential for MVFR cigs around 025 by daybreak Saturday. Felt the MVFR chances were still a bit too marginal for an introduction in the TAFs, but something that will need to be considered in future updates. Carlaw && .MARINE... Issued at 245 AM CDT Fri May 16 2025 Southerly winds are expected to gust to gales to 35 kt this afternoon for mainly the IL nearshore waters and through Gary in the IN nearshore. Winds will shift westerly this evening as a cold front moves across southern Lake Michigan. Winds may continue to gust to near gale force with and just behind this cold front. Gusts will then diminish slightly, into the 25-30kt range which will continue through early Saturday evening. cms && .FIRE WEATHER... Issued at 245 AM CDT Fri May 16 2025 A fire weather watch remains in effect for all of northeast IL this afternoon. Much drier air has spread across western and northern IL and is expected to remain in place through mid afternoon. Dewpoints may lower a few more degrees, into the mid 40s and combined with high temperatures in the middle, to perhaps upper 80s, minimum relative humidity levels in the 20 to 25 percent range are possible this afternoon. Southwesterly winds will steadily increase this morning into this afternoon with gusts into the 40-45 mph range expected this afternoon. This combination of low relative humidity and strong winds will create the potential for rapid wildfire spread. A limiting factor is that some areas received heavier rainfall from the storms Thursday afternoon. Low level moisture is expected to surge back north late this afternoon into early this evening, with dewpoints in the upper 50s, perhaps lower 60s, east of I-55. There will also be a chance of thunderstorms late this afternoon into early this evening for areas along and east of I-55. The combination of rising relative humidity levels as well as possible rainfall will end the wildfire risk by early this evening. cms && .LOT WATCHES/WARNINGS/ADVISORIES... IL...Wind Advisory until midnight CDT tonight for ILZ003-ILZ004- ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ019- ILZ020-ILZ021-ILZ032-ILZ103-ILZ104-ILZ105-ILZ106-ILZ107. Red Flag Warning until 7 PM CDT this evening for ILZ010-ILZ011- ILZ012-ILZ019-ILZ020-ILZ021. IN...None. LM...Gale Warning until 10 PM CDT this evening for Winthrop Harbor IL to Gary IN. Small Craft Advisory until 10 PM CDT this evening for Gary to Burns Harbor IN-Burns Harbor to Michigan City IN. && $$ Visit us at weather.gov/chicago ####018010239#### FXUS63 KLMK 161709 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 109 PM EDT Fri May 16 2025 ...Updated Aviation Discussion... .KEY MESSAGES... * SIGNIFICANT SEVERE WEATHER OUTBREAK POSSIBLE LATE THIS AFTERNOON INTO THIS EVENING. * All severe weather hazards are on the table, including damaging winds, large hail, tornadoes, and torrential rainfall. A few strong tornadoes and instances of very large hail are possible. * Strong to severe thunderstorms are also possible this morning west of Interstate 65, with large hail as the main hazard. && .UPDATE... Issued at 1123 AM EDT Fri May 16 2025 A large area of convection continues to push through central and eastern Kentucky this morning. This rainfall is being forced by strong warm advection along with lift associated with a southwest low-level jet axis. While the surface layer is pretty stable from nocturnal cooling, we do have an EML aloft with fairly steep low-mid level lapse rates. There was capping overnight until the cap mixed out due to nocturnal cooling and convection has taken off. Storms have been on/off severe this morning with mainly marginally severe hail being reported in the storms. Given the near surface stability, gusty winds have been observed on occasion, but nothing near severe levels. With PWATs well above 1.50 inches, we're seeing torrential rainfall with these storms as well. Going forward, main area of severe convection will be from roughly south of a line from Butler County northeast to Harrison County. In this area storms capable of torrential rainfall, and hail up to 1 inch in diameter in the strongest cores will be possible. A more concentrated wind threat may emerge with a small scale bow/MCS that is trying to take shape near Hopkinsville. This activity will surge eastward along the KY/TN border this morning. Have done a local extension of WW259 through noon EDT. We did cut off the northern area of that watch where additional severe weather is not anticipated. Rainfall amounts have been impressive with an inch to an inch and three quarters falling along a line from Mayfield northeast through the Elizabethtown area. We expect portions of the Bluegrass and southern KY to pickup on similar rainfall through the morning, most likely an inch to an inch and a half. Given recent rains from this morning and expected additional rainfall this afternoon/evening, have coordinated with JKL and hoisted a Flood Watch for the southern half/two-thirds of the LMK forecast area. As for the afternoon hours...Somewhat of a complicated forecast here as ongoing clouds and convection is likely to linger over central and eastern KY into the afternoon. Recent satellite imagery does show back edge of the clouds clearing the Paducah area and working eastward. The overall theme that we have been messaging seems to OK at the moment. That is, we expected additional thunderstorms to fire out across eastern MO/NE AR/W KY/S IL in the next few hours. Parameter space out that way will support discrete supercells with very large hail, damaging winds, and strong tornadoes (some long track possible). This activity will move eastward toward central KY while growing up scale into a large or a couple of MCS/QLCS's resulting in widespread damaging winds and spinup tornadoes within the line. The actual evolution of this afternoon/evening's activity remains the most challenging. It appears that a two pronged scenario could develop across the region. First, ongoing convection across southern KY may end up stalling out and leaving some sort of baroclinic boundary in place. As skies clear out, this boundary will become the focus for convective development this afternoon. It is possible that we could see isolated-scattered supercells develop along this boundary from roughly Paducah eastward to Bowling Green and toward Somerset. This boundary could then lift north/northeast into the evening hours. Parameter space across KY would support all modes of severe weather. However, given ongoing cloud cover and shorter time of insolation, not overly confident how unstable we could become. Meanwhile back to the west, expected supercell development should be ongoing while developing upscale into 1 or more lines. These QLCSs should then plow eastward resulting in damaging winds, spin up tornadoes within the line, along with some isolated-scattered large hail. This scenario has support from many of the 12Z CAMs though though the question is how far north could the baroclinic boundary lift prior to the QLCS coming in from the west. The HRRR is most aggressive with its northward movement taking it as far north as I- 64. On the other hand the WRF ARW/NSSL WRF and the RRFS all keep the boundary more over southern KY while plowing the QLCS out to the west eastward rather quickly. MPAS runs are not in yet, but will evaluate them early this afternoon. && .SHORT TERM /THROUGH TONIGHT/... Issued at 407 AM EDT Fri May 16 2025 A significant severe weather outbreak is possible later this afternoon and this evening across the Ohio Valley. Storms developing ahead of an incoming cold front will quickly become severe in a very unstable and strongly sheared environment. All severe weather hazards, including widespread damaging winds, very large hail, and strong tornadoes are possible, as well as localized flash flooding. Main bust potential hinges on the evolution of storms this morning, which have developed over western Kentucky. These storms will have a large hail threat of their own, especially west of Interstate 65. While they will at least temporarily stabilize the atmosphere, strong warm advection is likely to win out, allowing a fairly quick recovery this afternoon. With around 3000 J/kg of mixed-layer CAPE, 1000 J/kg of downdraft CAPE, and 60 kt of effective shear, initially discrete storms will organize into at least bowing segments. A few of the discrete cells could produce very large hail and/or strong tornadoes, and line segments could produce hurricane-force wind gusts. Spin-up tornadoes will also be in play with any of the bowing structures as well. The peak severe threat could be slightly delayed depending on how quickly the atmosphere can reload after morning convection, but the threat will mainly be focused on the evening hours. Initial discrete cells could develop in the late afternoon. It's also worth noting that in the late evening, the line will become more east-west oriented, opening the door for excessive rainfall especially over south-central Kentucky. Confidence in the exact placement is low at this time, but it bears watching as the event unfolds. Bottom line, significant severe weather is possible late this afternoon and this evening. Make sure you have multiple ways to receive warnings and a plan in place should a warning be issued! && .LONG TERM /SATURDAY THROUGH THURSDAY/... Issued at 352 PM EDT Thu May 15 2025 By Saturday morning, the actual cold front will be pushing through the area with most of the showers and storms exiting to our east. The associated upper low will be over the Great Lakes with the longwave trough axis extending south over the OH and TN Valleys before flattening out against the subtropical ridge over the Gulf. Weak CAA behind the front will result in climatological normal temperatures for the weekend with highs in the mid to upper 70s to lower 80s accompanied by breezy WSW winds on Saturday. Overall, most will experience a fair weather weekend. Southern KY will see a slight chance of showers on Sunday as the southern edge of the new airmass begins to lift northward due to the next low pressure system strengthening over the Central Plains. This will begin another period of unsettled weather as we enter the beginning of the new work week. By Monday, a warm front will begin lifting across the region resulting in warm and moist air advection, as PWATs surge into the upper percentiles of SPC's sounding climatology. Models tend to agree on convection from our west moving into our area by Monday morning with another round Monday evening. The warm front appears to stall over the region, prolonging our shower and storm chances into Tuesday and Wednesday before the occluded low pushes through on Wednesday. With model soundings advertising sufficient instability and ML guidance also showing enhanced severe probabilities, severe weather can not be ruled out. Details remain hazy this far out, but will continue to monitor closely with subsequent forecast packages. Stay tuned. && .AVIATION /18Z TAFS THROUGH 00Z SUNDAY/... Issued at 109 PM EDT Fri May 16 2025 Early morning convection is finally pushing to the east of the region. VFR conditions are expected this afternoon with a period of sun/clouds with gusty southwest winds. Next wave of vigorous storms is expected to arrive this evening. The overall convective evolution remains challenging as scattered supercells will be possible across central KY while a large squall line moving in from the west. For now, have largely updated the previous TAF to keep storms in the region beginning around 23Z with the bulk of it occurring between 16/23Z-17/05Z. Given the extensive squall line and expected wind field, have opted to use VRB25G50 in the TAF as the squall line passes through. Most convection should be east of the terminals by 17/06Z, with light SW winds and high cigs for Saturday morning. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...Flood Watch through late tonight for KYZ026>028-039>041- 045>049-053>057-061>067-070>078-081-082. IN...None. && $$ UPDATE.......MJ SHORT TERM...RAS LONG TERM....CG AVIATION.....MJ