####018007931#### FXUS61 KRLX 151940 AFDRLX AREA FORECAST DISCUSSION National Weather Service Charleston WV 340 PM EDT Thu May 15 2025 .SYNOPSIS... A warm front lifts north of the area this afternoon/evening bringing much warmer temperatures, along with the potential for several rounds of severe weather through Friday night, some of which could be significant. && .NEAR TERM /THROUGH FRIDAY/... As of 310 PM Thursday... Key Points: * Warm front lifts north of the area this afternoon/evening * Several rounds of strong to severe thunderstorms possible, with the greatest concern being late tonight into Friday morning, but especially late Friday afternoon into Friday night An active near term period is expected with multiple rounds of showers/storms possible. At present, a surface warm front is lifting north across the central CWA, and will continue to traverse the rest of the forecast area over the next few hours, resulting in a warm afternoon, with highs topping out in the low to mid 80s across the lowlands. Additionally, isolated showers/storms are possible through this afternoon/evening. While instability will be on the higher end (2,000-2,500 J/kg mixed-layer) following the passage of the front, forcing will be quite weak (differential heating/topographic effects) amid a noted cap. Activity has been quite muted this afternoon, but the potential for a strong to severe thunderstorm or two remains possible if storms are able to initiate despite the capping. The main hazards w/ convection today would be wind/hail. The overnight will begin on the quiet side with mainly dry conditions expected across the forecast area. While not anticipated to be nearly as widespread as last night, some patchy mountain valley fog is expected to develop given weaker boundary layer flow further south/east. Another round of showers/storms then approaches the region later tonight from the north/west in association with convection further west that has yet to initiate. Current thinking is that by the time this activity reaches the forecast area, it should be mainly elevated in nature and in a weakening trend, although the potential for some strong to isolated severe storms does remains possible, with wind/hail being the primary hazards, with the greatest risk across northwest portions of the CWA. This activity should exit the eastern portion of the forecast area by mid/late Friday morning. Lows tonight will be in the 60s across much of the forecast area. Friday will be another warm day across the region with highs progged for the low 80s across the lowlands, with 70s in the mountains. A period of mainly dry weather is progged for the late morning and afternoon, with another round of thunderstorms expected beginning sometime in the late afternoon or early evening in the form of a MCS. Some timing/location uncertainty does still exist, but confidence is increasing in this feature moving across the CWA late afternoon into Friday night. Given such, SPC has upgraded much of the forecast area into a Enhanced Risk for late Friday into Friday night. The main hazard will be strong to significant damaging winds, but large hail and isolated embedded tornadoes cannot be ruled out, especially given any discrete convection. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... As of 245 PM Thursday... Key Points: * Ongoing outbreak of severe weather Friday night that could pose concerns for all hazards * A succession of cold fronts will bring precipitation and severe weather to a close on Saturday * Dry weather to round out the weekend The forecast period opens up in the midst of severe weather brought forth by a bowing segment first originating in the Mississippi and Tennessee Valleys Friday afternoon. Ongoing uncertainty with this evolving system will dictate the severity factor Friday night, but as of this issuance, strong wording for damaging wind gusts and large hail were included through midnight Friday night. The risk for tornadoes and heavy downpours will also be probable in activity. The low pressure system orchestrating this severe weather will be progressing through the Great Lakes region at the start of the weekend, and will drive a cold front through the forecast area on Saturday. This will bring precipitation to a gradual end and will push the severe risk into the eastern seaboard on Saturday. A reinforcing cold front will yield dry weather to round out the weekend in addition to cooling temperatures. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... As of 245 PM Thursday... The start of the work week grows more active as shortwave energy rounding an upper level ridge ventures into the area starting late Monday. Guidance then enters into a realm of various solutions for next week, but all point towards a more active state as the ridge breaks down and low pressure blankets the area with showers and more potential for thunderstorms. Seasonable temperatures round out the extended period, with daytime highs ranging in the 60s and 70s, then toppling down into the 40s and 50s during the overnight periods. && .AVIATION /19Z THURSDAY THROUGH TUESDAY/... As of 200 PM Thursday... A few isolated showers/storms are possible this afternoon/evening as a warm front lifts through the region, potentially resulting in very brief MVFR/IFR VSBY restrictions. Otherwise, VFR prevails under a SCT-BKN Cu field. Dry weather prevails to start tonight, then a wave of SCT showers/storms moves in from the northwest later tonight, bringing the potential for MVFR/IFR VSBY restrictions, and perhaps some MVFR CIGs, primarily north/east. This round of showers exits the eastern portion of the forecast area by late Friday morning, with mainly dry conditions expected for the remainder of the TAF period. Some patchy fog is expected tonight across the VA/WV mountain valleys, with some restrictions coded in for EKN. Light S/SW flow is expected throughout the period, with gusts of 15-20kts possible during the day on Friday. Higher gusts are possible with any thunderstorms. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z FRIDAY... FORECAST CONFIDENCE: High today, medium late tonight into Friday. ALTERNATE SCENARIOS: Timing of flight category changes with showers/storms could vary. Fog coverage overnight may vary from the forecast. EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. UTC 1HRLY 19 20 21 22 23 00 01 02 03 04 05 06 EDT 1HRLY 15 16 17 18 19 20 21 22 23 00 01 02 CRW CONSISTENCY H H H H H H H H H H H H HTS CONSISTENCY H H H H H H H H H H H H BKW CONSISTENCY H H H H H H H H H H H H EKN CONSISTENCY H H H H H H H H H H H H PKB CONSISTENCY H H H H H H H H H H H H CKB CONSISTENCY H H H H H H H H H H H H AFTER 18Z FRIDAY... IFR conditions are possible under convection Friday evening and Friday night, and then again Saturday afternoon. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...MEK/GW NEAR TERM...GW SHORT TERM...MEK LONG TERM...MEK AVIATION...GW ####018005729#### FXUS63 KTOP 151941 AFDTOP Area Forecast Discussion National Weather Service Topeka KS 241 PM CDT Thu May 15 2025 .KEY MESSAGES... - Warm, breezy and dry through Saturday. - Rain/storm chances return Sunday and into early next week. - Increasing chances for severe storms Sunday afternoon and Monday afternoon with all hazards possible with storms that develop. See discussion for further details. && .DISCUSSION... Issued at 234 PM CDT Thu May 15 2025 Mid-level water vapor imagery this afternoon shows a stout upper low across the northern Plains with southwest flow extending across much of the central CONUS. Weak zonal flow and troughing exists across the western US with a streak of upper-level moisture pushing in from Baja California within a sub-tropical jet streak. Across northeastern Kansas, a tight pressure gradient following a cold front last night remains laid out across the area with gusty westerly winds keeping conditions this afternoon much less muggy and slightly cooler than yesterday. Expect temperatures to top out in the low 80s this afternoon with winds decreasing around sunset this evening. Overnight tonight, a mid-level perturbation associated with the aforementioned upper low advects over Kansas and should help to push a secondary cold front/surface low through the area. This could bring some gusty winds to east-central Kansas early Friday morning with winds shifting towards the northwest as the frontal boundary slides through the area by mid Friday morning. Similar conditions will persist for the afternoon Friday as highs again top out in the low 80s with mostly sunny skies. The forecast area should remain dry through Saturday afternoon before moisture advection begins to return to the area Saturday evening and into Sunday. A weak mid-level wave will begin to work its way across the southern Plains Saturday afternoon that could help to bring some showers and a few rumbles of thunder to southeast portions of the CWA, but best chances for any precipitation remains south of the area until Sunday. By Sunday morning, southwest flow begins to increase aloft as a deepening trough axis advects in from the central Rockies. Lee cyclogenesis will further deepen a surface low in eastern Colorado further helping to push moisture north across Kansas. By Sunday afternoon, deterministic guidance is hinting at a warm front lifting north into central Kansas with a very ripe warm sector to its south. A dry line setting up somewhere across south-central Kansas also seems likely as the surface low begins to eject into western Kansas. With MLCIN decreasing into the afternoon, MLCAPE ranging from 2000- 3000 J/kg, 40-50 knots of 0-6 km shear and looping hodographs should set up across the warm sector pointing to a great set up for supercells and severe weather in the late afternoon and evening Sunday. Any storms that can develop along the dry line to our west or on the warm front will be capable of all hazards including large hail, damaging winds and tornadoes. All that said, there is still a fair amount of variability between guidance this far out...mainly with where surface features set up. Currently, the GFS and SREF keeps the warm front the furthest north with the NAM and EURO keeping the frontal boundaries south of I-70. Some guidance even tries to bring the dry line as far east as Salina indicating the potential for dry line storms in the late afternoon. As previously mentioned, confidence is low in where severe weather will occur, but at this point, the parameters needed for severe storms should be in place across the region. Monday will see another chance for severe weather across the area as the main trough axis begins to slide east across the area. Current thinking is that how things play out Sunday will largely impact how the severe threat on Monday plays out. If storms from Sunday evening linger into Monday morning and insulate the area for much of the day, it may be hard for us to regenerate much instability needed for severe storms. There are also chances that a frontal boundary associated with the main upper low shifts across the area Monday in the morning, limiting chances for storms in the afternoon. Will need to keep an eye on trends in the coming days to see how things continue to set up. Storm chances persist into the mid week next week as the upper low hangs across the central Plains. That said, following the frontal boundary Monday, most surface moisture needed for severe weather will be shunted east of the area so severe chances at this point in time remain low. With lots of cloud cover and rain chances, expect temperatures Tuesday into Thursday to be cooler, topping out in the 60s and 70s. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1222 PM CDT Thu May 15 2025 VFR conditions will persist through the TAF at all sites with the main aviation hazards being winds. Expect winds this afternoon to prevail out of the west, gusting upwards of 25-30 mph at times. Winds decrease under 10 mph around sunset this evening, shifting back towards the south/southwest through the night. A weak surface low looks to track across the terminals Friday morning around sunrise that could bring some gusty conditions for a few hours after sunrise, before winds increase area wide and shift out of the west/northwest. && .TOP WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Griesemer AVIATION...Griesemer ####018006563#### FXUS66 KMTR 151941 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1241 PM PDT Thu May 15 2025 ...New SYNOPSIS, SHORT TERM, LONG TERM... .SYNOPSIS... Issued at 1241 PM PDT Thu May 15 2025 Warm conditions continue today and Friday before a slight cooldown over the weekend. Gusty winds will develop late Friday into Sunday. Warm conditions return early next week. && .SHORT TERM... (This evening through Friday) Issued at 1241 PM PDT Thu May 15 2025 Satellite imagery shows lingering stratus at the immediate coast of the San Mateo Peninsula and the Big Sur Coast. With an upper level ridge across the West Coast, overall conditions remain dry and seasonably warm throughout the region with highs ranging from the middle 70s to the lower 80s inland and the middle 60s to lower 70s along the Bayshore, while onshore flow keeps the coastal regions cool with highs in the upper 50s to lower 60s. Friday's forecast is quite similar in the inland areas, but a stronger onshore flow should result in slightly cooler conditions in the coastal valleys, such as the southern reaches of the SF Bay (Redwood City and Fremont southwards), the Santa Clara valley, and the northern Salinas Valley, where around 3 to 5 degrees of cooling are expected. Meanwhile, morning lows hover around the upper 40s to the middle 50s for most people, with pockets of lower to middle 40s in the highest peaks. && .LONG TERM... (Friday night through next Wednesday) Issued at 1241 PM PDT Thu May 15 2025 Later on Friday through Saturday, an upper level trough will develop off the Pacific Northwest and deepen as it travels into the Great Basin, causing a dip in temperatures for the upcoming weekend. The ensemble models are starting to converge on a more open trough to continue into the Intermountain West or perhaps the Great Plains, as opposed to the Great Basin cutoff low that we had anticipated at this time yesterday, but this is a distinction without a difference for Saturday's high temperatures, which will dip by around 10 degrees in the interior valleys, to around the middle 60s to lower 70s, while the Bayshore drops into the lower to middle 60s. Although the trough will continue to move eastwards, leaving a classic "inside slider" scenario less likely, the pressure gradient between the cutoff low and a ridge in the eastern Pacific will still result in gusty winds across the region later on Friday into Sunday. The current forecast continues to show wind gusts reaching 25 to 35 mph across the region with gusts up to 45 mph possible at the ridgelines, along the coast, and through favored gaps and passes. Warming temperatures will return for the early part of next week with high temperatures rising to the middle 80s to lower 90s inland, or around 5 to 10 degrees above seasonal averages. Low temperatures should remain relatively stable near the upper 40s to middle 50s for the lower elevations, which should help alleviate concerns for heat- related illnesses for all but the most sensitive populations. Late Sunday and Monday, northerly winds could develop on the backside of the trough in the interior regions, especially in Napa County and the interior East Bay, helping to reinforce the warmer and drier conditions in those areas. Towards, and beyond, the end of the 7 day forecast, ensemble model clusters begin to diverge on the upper level pattern, with around 20% of ensembles developing an upper level trough heading into the start of the Memorial Day weekend, another 20-30% anticipating more zonal flow, and the remaining 50- 60% holding onto the ridge. && .AVIATION... (18Z TAFS) Issued at 1031 AM PDT Thu May 15 2025 VFR conditions have returned to all TAF sites with low clouds having retreated to the coast. Onshore winds will increase this afternoon, similar to the past few days, before easing overnight and into early Friday morning. Moderate to high confidence for KMRY, KSNS, and KHAF to see a return of low ceilings early Friday morning (albeit later than previous days). Elsewhere, VFR conditions expected through the TAF period. Vicinity of SFO...Expecting moderate west-northwest winds by this afternoon with occasional gusts. Moderate to high confidence VFR conditions will prevail through the TAF period and winds to ease late tonight and into Friday morning. Onshore winds are expected to increase Friday by afternoon. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals... Expecting northwest winds to increase this afternoon before easing by this evening. Moderate to high confidence for MVFR/IFR conditions to return Friday morning (albeit later that previous days). && .MARINE... (Today through Tuesday) Issued at 830 AM PDT Thu May 15 2025 Strong, gale force northwesterly winds continue across the outer coastal waters as well as the northern inner waters while fresh to strong northwesterly winds continue across the rest of the waters. Moderate seas bringing steep, fresh swell will continue through Saturday with significant wave heights between 10 to 12 feet expected across the outer waters. Widespread Gale conditions are expected to build into the weekend. Hazardous conditions will continue through the end of the forecast period. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory from 3 PM Friday to 3 AM PDT Saturday for Mry Bay-SF Bay N of Bay Bridge. Small Craft Advisory until 9 PM PDT this evening for Mry Bay. Gale Warning until 3 AM PDT Saturday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM-Pt Reyes to Pigeon Pt 0-10 nm. Small Craft Advisory until 3 PM PDT Friday for Pigeon Pt to Pt Pinos 0-10 nm. Gale Warning from 3 PM Friday to 3 AM PDT Saturday for Pigeon Pt to Pt Pinos 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm. Small Craft Advisory until 3 PM PDT Friday for Pt Pinos to Pt Piedras Blancas 0-10 nm. && $$ SHORT TERM...DialH LONG TERM....DialH AVIATION...RGass MARINE...RGass Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, X, and YouTube at: www.facebook.com/nwsbayarea x.com/nwsbayarea www.youtube.com/nwsbayarea