####018007529#### FXUS63 KLOT 170112 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 812 PM CDT Fri May 16 2025 .KEY MESSAGES... - Breeze southwest to west winds will continue tonight and tomorrow. - Otherwise, a quiet weekend is expected. && .DISCUSSION... Issued at 308 PM CDT Fri May 16 2025 Through tonight: A large upper-level low over Minnesota has brought continued SW flow aloft into our region, ultimately resulting a relatively uncommon High-Plains pattern across northern Illinois today. Earlier today, a very dry airmass upstream per WV 12Z KSGF RAOB and WV imagery over Missouri has advected over the northwest half of Illinois amid deep diurnal mixing. This has pushed RH values as low as the upper teens over the western CWA as S/SSW winds gust 35 to 40 mph. This prompted an earlier issuance of a Red Flag Warning for critical fire wx conditions across portions of the forecast area where little to no rain fell on Thursday, though elevated fire wx conditions are occurring elsewhere (covered by a Special Weather Statement) this afternoon. Meanwhile, deep mixing into 40kt+ flow aloft should begin to generate sporadic surface gusts to 45 mph or briefly higher mid to late afternoon for areas around and northwest of I-55. Then, as a surface trough crosses the area late this afternoon into this evening, a favorable isallobaric component to an already strong synoptic gradient combined with modest residual mixing with CAA could yield SW gusts to 50 mph for a period this evening. Have therefore maintained a Wind Advisory for the aforementioned locations through midnight. While there is no headline specifically in effect for blowing dust, observations from gusty winds in rural areas on Thursday support maintaining a mention of patchy blowing dust in the forecast grids and Wind Advisory through this evening. No substantial changes have been made regarding the severe thunderstorm potential late this afternoon into early evening (see the latest Mesoscale discussion update for more detailed information). However, observational trends as of 3pm as well as near-term CAM guidance continue to favor areas south of a Pontiac to DeMotte line for the highest chances of severe convection as the northern edge of the discrete cells over southwest Illinois ride a northward-advacing plume of modest low-level moisture. Farther north, a gradual increase in high-based cumulus coverage will be a focus for at least isolated storm development across the remainder of the forecast area. Kluber Saturday through Friday: The big, vertically stacked, low pressure will be over northern Lake Michigan early Saturday morning with continued gusty westerly winds and extensive stratocumulus deck across our area to the south of the upper low. This system will move eastward away from the area during the day Saturday, which should allow cloudiness to scatter out some during the afternoon. Pressure gradient will begin to ease some Saturday afternoon, though deepening mixing of the boundary layer may offset the decreasing gradient and slow the decrease in winds during the afternoon. By sunset winds will quick subside as boundary layer decouples. 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. Izzi/Carlaw && .AVIATION /00Z TAFS THROUGH 06Z SUNDAY/... Issued at 627 PM CDT Fri May 16 2025 A dust storm will move over GYY/DPA/ORD/MDW with visibility below 1 mile and southerly wind gusts up to 45kt. A thunderstorm may occur at the Chicago terminals during the dust storm, as well. Thereafter, visibility should gradually improve especially after a westerly wind shift in the 02-03Z timeframe. Gusty west winds at or above 30 kt should continue through tomorrow morning before easing in the afternoon. Borchardt && .LOT WATCHES/WARNINGS/ADVISORIES... IL...Wind Advisory until midnight CDT tonight for ILZ003-ILZ004- ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ019- ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ103-ILZ104- ILZ105-ILZ106-ILZ107-ILZ108. Blowing Dust Advisory until 9 PM CDT this evening for ILZ003- ILZ004-ILZ005-ILZ008-ILZ010-ILZ011-ILZ012-ILZ019-ILZ020- ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ107. IN...Wind Advisory until midnight CDT /1 AM EDT/ tonight for INZ001- INZ002-INZ010-INZ011-INZ019. Blowing Dust Advisory until 9 PM CDT /10 PM EDT/ this evening for INZ010-INZ011-INZ019. 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 ####018005866#### FXUS64 KMRX 170113 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 913 PM EDT Fri May 16 2025 ...New UPDATE... .UPDATE... Issued at 845 PM EDT Fri May 16 2025 We are still expecting a line of storms to move through the region around or after midnight. Storms are slowly starting to come together near the IL/KY/IN border. Some discrete cells are ahead in Central Kentucky. I think the lull in activity will continue for 2 to 3 more hours before things get more active. CAMs are inconsistent with activity ahead of the main line. We have low confidence in storms developing ahead of the main line. The main line will move into the region around or after midnight and all hazards are still possible. A tornado watch is likely to be issued later tonight as the line moves closer. Wind shear is very high with effective shear around 55 kt and 0 to 1 km shear 35 kt. && .SHORT TERM... (This evening through Saturday) Issued at 308 PM EDT Fri May 16 2025 Key Messages: 2. Severe thunderstorms possible with threats of damaging winds, large hail, and a lower but still significant threat of tornados this afternoon into tonight. 2. Drier conditions for Saturday. Discussion: The atmosphere is primed for severe storms out ahead of the approaching short wave trough, as HRRR/RAP forecast continue to show MLCAPE this afternoon between 2000 and 2500 J/Kg with EBShear of around 50 to 60+ kts. A remnant outflow boundary near the northern Plateau into Southwest VA has the potential to be the focus for storms this afternoon out ahead of tonight's main event, and supercell structures would be likely along with the potential for hail, damaging winds, and an increased threat of a tornado near the boundary. This threat will be conditional on if the cap erodes enough for these additional storms to get going which is still uncertain, and the hi-res CAMS have had a poor handle on this daytime convection overall and unfortunately have added little to the confidence in this scenario so far. Despite the loss of heating after sunset, the instability will remain significant tonight out ahead of the main round of convection as lapse rates steepen with the shortwave trough moving in. The HRRR/RAP forecasts show MLCAPES still around 2000 to 2500 J/Kg as the convection approaches. The LLJ will also increase as the line approaches with 850 mb winds increasing to near 50 kts, and EBShear OF 60+ kts is indicated along with increasing low level shear (with 0-1km shear reaching 35+ kts). Hi-res CAMS and other models have been more consistent in showing a line of convection moving through overnight, with timing still looking most likely to fall between 03z and 09z. All severe hazards look possible, with damaging winds and large hail the primary threats along with a lower, but still significant (around 5 percent within 25 miles of a point), threat of tornadoes. In addition, forecast PW values of 1.6 to 1.8 will be near the climo max, and NAEFS IVT values are forecast to be near climo max as well. This is a strong signal for very heavy rain rates, which may result localized flooding especially in areas that see repeated rounds of rainfall. The highest risk for flooding would likely be across the north given the increased potential for storms there this afternoon. Saturday will turn drier behind this system, with plenty of sunshine and a warm afternoon. && .LONG TERM... (Saturday night through next Friday) Issued at 308 PM EDT Fri May 16 2025 Key Messages: 1. Warm with a some showers and storms around at times Sunday through Monday. 2. Precipitation chances increase for Tuesday into Wednesday, along with a chance for strong to severe storms. 3. Cooler late next week in the wake of a cold front. Discussion: Saturday night looks to be mainly dry, but despite low amplitude upper level ridging slowly building over our area during the Sunday/Monday time frame, weak ripples in the flow are expected to bring showers and thunderstorms to our area at times. By Tuesday, a stronger upper trough will approach the Mississippi Valley with increased chances for showers and thunderstorms Tuesday into Wednesday across portions of the Tennessee Valley and Southern Appalachians, and there is an uptick in the chances for strong to severe storms with this system. Low confidence on how models are handling the latter periods behind the cold front. It may be drier, but some models want to park a closed upper low nearby so at this point the forecast will keep lower chances for showers and storms Thursday and Friday. && .AVIATION... (00Z TAFS) Issued at 726 PM EDT Fri May 16 2025 Conditions will be mainly VFR outside of thunderstorms. The exception is MVFR CIGs in the morning likely at TRI. A line of storms will move through the region around and after midnight. Some storms may be severe with gusty winds being the main threat. Low level wind shear will be present in spots where surface winds are not gusty. The line should move through fairly quickly with clearing expected tomorrow morning with winds becoming more westerly. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 69 87 65 85 / 70 10 10 50 Knoxville McGhee Tyson Airport, TN 66 83 62 82 / 80 10 10 30 Oak Ridge, TN 66 84 62 82 / 90 10 10 30 Tri Cities Airport, TN 64 80 57 78 / 80 20 0 10 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM... AVIATION...McD ####018004622#### FXHW60 PHFO 170113 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 313 PM HST Fri May 16 2025 .SYNOPSIS... Seasonably wet and breezy trades prevail into next week. && .DISCUSSION... High stability prevails in the mid-levels as a typical breezy trade wind pattern remains established over the area. An upper low of low- latitude origin sits over the area bringing a slight reduction in stability as the inversion on this morning's observed soundings was rather soft and not as sharp as normal. As a consequence, the band of showers advancing through the state today has had no issue maintaining showers around 10-12kft deep even during the unfavorable peak heating period. This is in turn enhancing leeward shower penetration, especially over Oahu, and contributing to pockets of heavier showers over windward/mauka portions of all islands. The next 24-30 hours will be characterized by little overall change except for a subtle veering of the low level flow to a more ESE direction. Given adequate moisture availability in the boundary layer, this has caused several members of today's guidance suite to hint at potential for banding within convergent ESE flow (i.e. Molokai/Lanai plumes) both this afternoon and tomorrow afternoon. This type of setup generally remains highly uncertain until it is underway, though it tends to favor southern/central Oahu including the Honolulu area urban corridor. At present, a loosely organized plume of mostly light rain originating over leeward Molokai is indeed streaming over southern portions of Oahu. This band of rain will likely persist for the next few hours. Weak convergence observed within this band suggests limited prospects for strengthening. Upper-level flow maintains a cyclonic character well into next week aiding slightly lowered stability and providing a boost to trade wind showers. As surface high pressure remains established north of the islands, a breezy and seasonably wet trade wind pattern is forecast to prevail for the next several days. && .AVIATION... A moderate to locally breezy trade wind pattern of mostly windward showers and passing low clouds will continue into early next week. Currently, scattered showers favor windward sides of the island chain. As winds turn more southeast, plumes of moisture will funnel additional showers across leeward areas during the afternoon and early evening hours. MVFR or even brief IFR ceilings and visibilities can be expected within any showers. AIRMET Sierra remains in effect for mountain obscuration along windward sections across the island chain. These conditions will likely continue into the night. AIRMET Tango remains in effect for low level moderate turbulence over and immediately S through W of all island mountains. && .MARINE... Strong high pressure will remain anchored northeast of the state through tonight, keeping fresh to strong trades in place. A developing trough to the distant northwest is expected to ease the trades over the weekend into early next week. Light to moderate trades with localized sea breezes are expected over the western islands, while moderate to locally strong persist over the eastern end of the state. A Small Craft Advisory (SCA) remains in effect for most marine zones east of Oahu through 6 am Saturday, and for some of the windier zones around Maui and the Big Island through 6 pm Saturday. The SCA may need to be extended for the typically windy waters over the eastern end of the state through the weekend. Surf along north and west-facing shores will remain very small during the next 7 days. Surf along south-facing shores will hold at background levels through tonight. A series of small south and south-southwest swells will give a small boost to south shore surf over the weekend, with a further boost up to the seasonal average possible during the middle to latter part of next week. Surf along east-facing shores will hold close to seasonal normals during the next 7 days. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Saturday for Kaiwi Channel- Maui County Windward Waters. Small Craft Advisory until 6 PM HST Saturday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Windward Waters- Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...JVC AVIATION...Farris MARINE...TS