####018004275#### FXHW60 PHFO 211300 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 300 AM HST Wed May 21 2025 .SYNOPSIS... Moderate to locally breezy trades will deliver clouds and showers to windward and mauka areas through the week, with some decaying showers reaching leeward areas as well. A few downpours and even a rumble or two of thunder will be possible Thursday and Friday as a disturbance aloft moves over the island chain. A steady decrease in shower coverage and intensity, along with progressively nicer weather, can be expected as we move through the Memorial Day weekend. && .DISCUSSION... Currently at the surface, a 1031 mb high is centered around 1300 miles north-northwest of Honolulu, with another 1027 mb high centered to the distant northeast. The resulting gradient is driving moderate trade winds across the island chain early this morning, although land breezes have developed in some of the more terrain sheltered leeward locales. Infrared satellite imagery shows mostly cloudy conditions over windward and mauka areas, with partly cloudy skies in leeward sections. Radar imagery shows scattered to numerous showers moving into windward slopes and coasts, with some of these showers pushing into leeward communities at times. Main short term focus revolves around rain chances and thunder potential. High pressure will persist to the north-northwest of the islands throughout the forecast period. This will maintain moderate to locally breezy trade winds, with only minor fluctuations in strength from day to day. A wetter than normal trade wind pattern will persist through the remainder of the work week, as a pair of disturbances aloft keep inversion heights elevated and conditions somewhat unstable. In fact, with H7-H5 lapse rates increasing to 6.5 - 7.0 C/km and surfaced based CAPE values climbing to around 1000-1500 J/KG, some locally heavy downpours and even a few rumbles of thunder will be possible across portions of the state late Wednesday night through Friday evening. The upper level disturbance will gradually weaken over the weekend into early next week, and precipitable waters values will also similarly decrease. This should bring a steady decrease in shower coverage and intensity with progressively nicer weather expected as we move through the Memorial Day weekend. && .AVIATION... Moderate to locally breezy trade winds will persist during the next 24 hours, strongest and most gusty from mid morning through late afternoon. Low clouds and showers will favor windward and mauka areas, particularly overnight and during the morning hours, with showers reaching leeward communities at times. AIRMET Sierra remains in effect for mountain obscuration across windward sections of Kauai, Oahu, Molokai, and Maui. Conditions should improve in most areas by late this morning. && .MARINE... Surface high pressure building in far north of the islands will maintain moderate to locally strong trades through at least Friday. A Small Craft Advisory (SCA) for the typically windy waters around the Big Island and Maui has been extended through late Thursday, but will likely need to be extended through this weekend as moderate to locally strong trade winds persist. Surf along south facing shores will remain just below seasonal average through Thursday. A small, long period, south southwest swell will filter into the area late Thursday and bring surf near the summer average along south facing shores through Saturday. Surf will then slowly decline Sunday through early next week. East shore surf will remain near seasonal average during the next couple of days. Tiny surf will prevail along north facing shores this week and into the weekend. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Thursday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel. Small Craft Advisory from 6 AM this morning to 6 PM HST Thursday for Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Jelsema AVIATION...Jelsema MARINE...Thomas ####018005206#### FXUS63 KJKL 211302 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 902 AM EDT Wed May 21 2025 .KEY MESSAGES... - A cooler air mass will arrive on Thursday, with below normal temperatures then lasting until early next week. - There will be possibilities for showers or a few thunderstorms at times from Thursday on, but no heavy rainfall is foreseen through at least Sunday. && .UPDATE... Issued at 902 AM EDT WED MAY 21 2025 A quick refresh of the grids using the latest surface observations. Also, updated PoP to reflect the light rain showers and drizzle across the CWA. Morning text and radio products have been updated to reflect these changes. Grids have been saved and sent. UPDATE Issued at 1235 AM EDT WED MAY 21 2025 Updated to end the watch early and take out the extra thunder wording in the grids. Did also adjust PoPs per radar and the latest CAMs guidance through the rest of the night. Also, added in the current obs and trends for the T/Td/Sky grids along with adding in some valley fog along with localized dense patches. Will also be dropping the flood watch shortly. These adjustments have been sent to the NDFD and web servers along with a freshening of the zones, SAFs, and HWO. UPDATE Issued at 925 PM EDT TUE MAY 20 2025 With the storms showing a tendency to continue strong in the north, have updated the forecast primarily to extend the tornado watch further northeast to include: Powell, Lee, Wolfe, and Estill counties affecting the weather attributes. Did also adjust PoPs per the latest radar and CAMs guidance along with an update to the T/Td grids on account of the obs and trends. These adjustments have been sent to the NDFD and web servers along with a freshening of the zones, SAFs, and HWO. && .SHORT TERM...(This evening through Wednesday night) Issued at 610 PM EDT TUE MAY 20 2025 A round of showers/thunderstorms is exiting the region to the east late today, while the next one grows over western KY and West TN just ahead of a cold front. Aloft, an upper low is centered over the norther plains with an elongated shortwave/vorticity lobe rotating around its southeast side. Thunderstorms will develop eastward into our area this evening as the cold front and shortwave approach. The atmosphere will work to recover in the wake of the afternoon convection. It's already near 80 in Wayne County, but only in the upper 60s where rain is exiting to the east. With the sun getting low in the sky, it's questionable how much recovery can occur in far east KY. Sufficient shear for severe weather is expected area wide, but the greatest severe weather risk this evening could end up being over our western counties due to more questionable recovery for instability in the east. Precip will begin to die down from west to east late tonight, but may linger into Thursday to some extent. The significant change in surface air mass should hold off until during the day, possibly allowing for a few more showers or even thundershowers. The forecast does turn dry area wide Wednesday evening, as any lingering showers should be to our northeast beneath the upper low transitioning eastward to the Great Lakes. .LONG TERM...(Thursday through Tuesday) Issued at 643 PM EDT TUE MAY 20 2025 A myriad of lows surface and aloft to our northeast will be our main influence at the start of the period. The surface lows will be continuing a flow of relatively cool air into our area from the west northwest. A shortwave trough rotating southeastward around the southwest side of the upper lows will pass over our area on Thursday. However, there is some model disagreement in the strength and southward extent of this feature, and changes to Thursday's POP may occur. The northeast CONUS system will depart eastward and surface high pressure will build eastward into our area, resulting in the likelihood of dry weather from Thursday night into Saturday. A warm air advection regime then returns late in the weekend once the surface ridge slips to our east. This will be followed by another upper trough dropping east southeast into the Midwest. This supports low pressure tracking northeast over either the Ohio Valley or the Tennessee Valley early in the new week, with models not locked in on a solution. This presents some forecast uncertainty, but certainly justifies having some decent probabilities of precip (currently mainly in the 50-60% range for each period Sunday-Tuesday). && .AVIATION...(For the 12Z TAFS through 12Z Thursday morning) ISSUED AT 710 AM EDT WED MAY 21 2025 Look for VFR conditions to make a comeback by midday. Winds will be light and variable into mid morning then pick up from the southwest at 5 to 10 kts with some higher gusts through the afternoon before diminishing back to light after dark. && .JKL WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...VORST SHORT TERM...HAL LONG TERM...HAL AVIATION...TITUS ####018005458#### FXAK67 PAJK 211302 AFDAJK Southeast Alaska Forecast Discussion National Weather Service Juneau AK 502 AM AKDT Wed May 21 2025 .SHORT TERM... As the ridge continues to weaken, chances of showers continue across SE AK through Wednesday night, before a brief period of drier weather sets in on Thursday, especially for the northern half of the panhandle. A remnant trough over the area the past few days has all but disintegrated. In its place, more southwesterly onshore flow is joining forces with an atmosphere saturated up to at least 500 mb to keep lingering chances of rain in the forecast. Somewhat cooler air aloft has also injected an element of instability, meaning that some of the rain will be more convective in nature. The remnants of a mid level short-wave will move through the panhandle late Wednesday night into Thursday morning, and given this and the continuing onshore flow, extended chances of rain across the area through Wednesday night, and into early Thursday morning though still anticipate drier conditions to emerge on Thursday. Past this point, a change in the weather pattern begins to dawn as a vertically stacked moves out of the Bering Sea and enters the Gulf of AK. .LONG TERM... Looking towards late week, guidance have begun to converge on a less progressive pattern, with increased cold air descending down from the Arctic. This cold air will intensify the trough, increasing the amplitude, and directing the moisture flow towards SE AK. The result will be multiple waves of moisture moving over the panhandle beginning this Saturday. Exact details of this evolving system are hazy, but what can be said is long duration moderate rain with periods of heavy rain will move into the southern panhandle. What is uncertain is how far this moderate to heavy rain producing moisture will move northward. Currently, the more likely solution is the heavier moisture will be directed at the southern panhandle with lighter precipitation from Petersburg up to Juneau. However, trends in ensemble guidance has probabilities increasing for these much higher than normal precipitation totals up into the Juneau area. In the southern panhandle, there is around an 80% chance for 2 inches of rainfall in 24 hours, while the same percentage chance exists for 1 inch of rainfall for areas like Juneau, Gustavus, Angoon, and Sitka. Regardless of either solution, with the current state of rivers, no flooding is currently expected. && .AVIATION.../Through 12z Thursday/... No widespread aviation hazards through the TAF period. VFR to upper- end MVFR flight conditions prevail across the panhandle as last bits of upper lvl energy shift eastward with isolated showers lingering through morning. By 18 to 21z, anticipate improving flight conditions to predominate VFR with SCT to BKN deck CIGS AoA 4000 to 6000ft with an underlying FEW to SCT deck. Heavier showers will continue to be isolated in nature through the afternoon as weak ridging moves in aloft, with main mechanisms of lift either being convective or orographic on shore flow. Not expecting widespread visibility issues, outside the aforementioned isolated heavier shower, but forecast confidence in airport impacts remains too low to include in TAFs at this time. Winds should remain near 10kts or less for majority of the panhandle, outside of Haines and Skagway, which will see sustained winds up to 15 to 20kts and isolated gust up to 25 to 30kts through 18 to 00z this afternoon as pressure gradient tightens. && .MARINE... Outside: Winds slowly shift from the SW to the SE through Wednesday across the outer coastal waters and the Gulf as a new system begins to approach the Gulf from the W. Winds for the outer coastal waters largely remain between 10 to 15 kt through Thursday, before a system arriving on Friday sees winds strengthen up to 20 - 25 kt for areas south of Cape Spencer. Winds across the central Gulf of AK will strengthen to 20 to 25 kt by Wednesday night. Wave heights across the outer coastal waters start Wednesday between 4 to 5 ft, slowly subsiding to 3 to 4 ft by Wednesday night, before increasing to 5 to 7 ft on Thursday. Higher wave heights of up to 8 - 9 ft are anticipated across parts of the central and northern Gulf by late Wednesday night. Inside: Inner channel wind speeds will continue to be pretty light overall through most of Friday - generally out of the south at around 5 to 10 knots. The main exception to this is Icy Strait and Lynn Canal, where speeds will be upwards of 15 to 20 knots at times on Wednesday, with speeds decreasing Wednesday night. Late Friday into the weekend, wind speeds will increase in response to the next approaching area of low pressure. While confidence in speeds greater than 20 kts is high, confidence is speeds greater than 35 knots is low. So for now, capped wind speeds at 25 to 30 knots. But as confidence in the track and strength of the low increases, gales may need to be introduced. Stay tuned. && .AJK WATCHES/WARNINGS/ADVISORIES... PUBLIC...None. MARINE...None. && $$ SHORT TERM...GFS LONG TERM....NC AVIATION...NM MARINE...GFS Visit us at http://www.weather.gov/Juneau