####018006955#### FXUS66 KMTR 040408 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 908 PM PDT Fri May 3 2024 ...New UPDATE, MARINE... .SYNOPSIS... Issued at 1237 PM PDT Fri May 3 2024 Cold front on track to bring widespread rain, cooler temperatures, and gusty winds this weekend. Dry weather returns Sunday with a gradual warming trend through next week. && .UPDATE... Issued at 907 PM PDT Fri May 3 2024 The forecast for the incoming low pressure system remains largely on track with minimal changes. HRRR guidance shows the low slowing down slightly with rain arrival times pushes back by an hour or two. Rain will arrive during the early to late morning hours moving north to south. Based on HRRR guidance, the most likely arrival times are 3AM- 5AM for the North Bay, 7AM-10AM for the East Bay and South Bay, and 8AM-11AM for the Central Coast. Rainfall totals look largely the same with between 0.5-1.0 inches expected in the Bay Area and 0.2- 0.5 inches expected in portions of the Central Coast. Locally higher precipitation totals are expected in the coastal North Bay mountains and the Santa Cruz mountains. Gusty winds will extend inland from the coast as the system passes with gusts between 25-30 mph possible. Trend for below average daytime and overnight temperatures tomorrow through the early work week remains on track. && .SHORT TERM... (This evening through Saturday) Issued at 1237 PM PDT Fri May 3 2024 Mostly clear skies over the region today ahead of the next cold front. Ample cloud cover associated with the front now moving into the northern portions of the state will continue to move southward through tonight. Areas of light rainfall are expected to begin early Saturday morning along favored west-facing upslope areas in the coastal ranges as moist low-level westerly flow increases ahead of the front. Much of the surface front should be through the Bay Area by mid-morning, and late morning for areas further south along the Central Coast. Aided by a robust 150 kt NW-SE oriented jet on the back side of the low, this will be a rather quick-moving front with little-to-no chance of stalling. However, this jet and continued support of an enhanced northwesterly Eastern Pacific jet along the West Coast will support gusty northwest winds to 25-35 mph along coastal areas and NW-SE oriented valleys through the weekend. Rainfall amounts Saturday will be in the ball park of 0.4-0.75" for most locations, with a few seeing upwards of 1-1.25" in the coastal ranges of the North Bay and the Santa Cruz Mtns. Behind the cold front Saturday afternoon and evening, there is a slight chance for isolated thunderstorms across the area. Scattered showers will persist into Saturday evening, but conditions appear favorable for a few locally strong updrafts that would support a rumble of thunder or two, as well as small hail. Deep convection would not be supported, given limited cooling aloft, promoting a more stable environment aloft. Thus, any storms that do develop would be relatively short-lived. Really nothing out of the ordinary for us during these typical cold core systems, just more resemblant of a system we'd see in January rather than May. && .LONG TERM... (Sunday through next Thursday) Issued at 1237 PM PDT Fri May 3 2024 Sunday looks to be on the drier side with the low departing. Temperatures the next few days will be on the cool side with afternoon high temps dropping by as much as 18 degrees for inland locations. Low temps Sunday morning will be in the 40s for most, with a few pockets of upper 30s for inland and high elevation areas. Otherwise, a warm up is on tap for the rest of next week as the pattern becomes more ridge-dominant. By Wednesday, expect afternoon highs in the 70s to near 80, and the mid-to-upper 60s along the coast. && .AVIATION... (18Z TAFS) Issued at 1126 AM PDT Fri May 3 2024 VFR lasts until the early to mid evening for most terminals before IFR/LIFR level clouds move inland. Winds stay W/NW and remain gusty through the evening. As stratus approaches in the evening, winds become light to moderate, and slowly turn to become more S/SW ahead of the approaching low pressure system. By the mid morning hours of Saturday, most terminals will see winds increase once more to become breezy and gusty out of the SW, and rain begins, lowering visibilities at terminals. Cloud decks are expected to improve to become IFR/MVFR as the rain approaches. Rain continues into Saturday afternoon before dissipating, with winds turning to become N/NW and breezy. Vicinity of SFO...VFR conditions last through the evening, with strong wings gusting to around 35 knots expected. Stratus makes moves inland in the late evening, bringing IFR conditions as winds reduce. Winds reduce further into the night and turn southwesterly. These winds become gusty as the rain arrives early Saturday morning with MVFR CIGs and slight reductions in visibilty.Winds turn to become W/NW in the later morning, but rain lasts through the afternoon. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...IFR/LIFR CIGs push inland in the early evening. IFR/LIFR CIGs last through the majority of the overnight hours with lighter winds. As the rain band arrives, expect CIGs lift to become IFR/MVFR late Saturday morning. Gusty westerly winds build along the rain band. && .MARINE... (Tonight through next Thursday) Issued at 907 PM PDT Fri May 3 2024 Expect breezy to gusty northwest winds to continue with gale force gusts possible over the southernmost zones. This evening, a low pressure system and associated cold front will arrive from the north, bringing rain and moderate to fresh breezes across the waters. Winds will turn briefly southwesterly ahead of the system early Saturday morning, but turn to become northwesterly once more in the late part of Saturday morning. Rain ceases late in the day Saturday, and winds ease to become moderate into the new workweek. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...Small Craft Advisory from 9 AM to 9 PM PDT Saturday for Pigeon Pt to Pt Pinos 0-10 nm. Gale Warning until 9 AM PDT Saturday for Pt Pinos to Pt Piedras Blancas 0-10 nm. Small Craft Advisory from 3 AM to 9 AM PDT Saturday for Pt Arena to Pt Reyes 10-60 NM. && $$ UPDATE...Kennedy SHORT TERM...Behringer LONG TERM....Behringer AVIATION...Murdock MARINE...Murdock Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea ####018005605#### FXAK68 PAFC 040409 AFDAFC Southcentral and Southwest Alaska Forecast Discussion National Weather Service Anchorage AK 809 PM AKDT Fri May 3 2024 .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)... Southeasterly flow and weak upsloping continues areas of light precipitation mainly across Kodiak Island up through the eastern Kenai Peninsula, with some light drizzle expected to occasionally spill over the mountains into the western Kenai and Anchorage Bowl through early tonight. A front associated with a large mature low over the Bering will then push into Southcentral through tomorrow. Strong southeasterly flow will result in downsloping, dry conditions for much of the western Kenai Peninsula north through Anchorage and much of the Mat-Su Valley. However, this second system will bring rain a bit farther north than the previous, with locations along the Prince William Sound expected to receive periods of moderate to locally heavy rain (high elevation snow) throughout much of the weekend. As this front pushes into the area, a strengthening pressure gradient will also allow strong southeast gap winds to increase in intensity through tomorrow, particularly out of the Turnagain Arm and Knik Arms and Copper River Basin. A few higher gusts are also possible up on the Anchorage Hillside. Temperatures will remain near climatological averages, with highs in the 50s for most of the region and lows in the mid/upper 30s to low 40s. The associated large upper level low with this system crosses the Alaska Peninsula into the Gulf later on Sunday, with a weak ridge building over interior Alaska. When combined with some weak upper level shortwaves and marginal instability, a few weak/light convective showers and/or thunderstorms may develop along the foothills of the Wrangell Mountains/Alaska Range in the northern Copper River Basin late Sunday afternoon into Sunday evening. -ME && .SHORT TERM FORECAST SOUTHWEST ALASKA, BERING SEA AND ALEUTIANS (Days 1 through 3)... Rain, snow and windy conditions to the Aleutians and Southwest Alaska through the weekend. A Bering low will move in a mostly westward direction reaching just south of the Pribilofs overnight and Bristol Bay late tomorrow morning. As the low's front progresses northeastward this evening, today's rain and mix of rain and snow are expected to change over to all snow showers as temperatures drop overnight. This switch to snow is aided by the low's placement just east of the Pribilofs by mid-morning tomorrow, continued cool 850mb temperatures and cold northwesterly air flowing into the region. Widespread light snowfall accumulations in the AK Pen, Eastern Aleutians and along the Southwest coast are possible. However, the precipitation will switch to a more rain/snow mix to rain quickly through the day tomorrow as temperatures rise. Cooler northwesterly to northerly flow will keep the precipitation in the Aleutians mainly a rain/snow mix this weekend. Winds in the Central Aleutians will remain strong into tomorrow afternoon before slowly decreasing. Northerly to northwesterly winds tomorrow evening and Sunday will bring continued cooler conditions to the northern side of the Aleutians, the AK Pen and Southwest Alaska as the aforementioned Bering low crosses into the North Pacific. Freezing spray returns for this weekend in response to the northerly and northwesterly wind flow. -DJ && .LONG TERM FORECAST (Days 4 through 7: Tuesday through Friday)... The upper level closed low near St Matthew Island weakens slowly and begins to move to the Eastern Aleutians and Alaska Peninsula before stalling briefly near Kodiak Island through the forecast period. The broad trough over the Bering makes inroads over most of Mainland Alaska with the jetstream support and North Pacific energy along the Southern portions continuing. Model confidence becomes more uncertain through the weekend with a number of troughs rotating through the pattern. The next significant weather producer moves over the Western Aleutians beginning Wednesday night as a North Pacific low and front moves across to the Eastern Aleutians by the weekend. Overall breezy conditions linger across the Aleutians and AKPEN through midweek, becoming gustier Wednesday night in the West, and spreading to the Eastern Aleutians for Friday. Gale force winds across the Southern edges of the low remain South of the Western Aleutians Wednesday and Thursday before diminishing. Rain spreads over the Aleutians through the forecast. Above average rainfall is expected to spread into Southwest Alaska, over the AKPEN into Cook Inlet and Kodiak Island for Wednesday and extends along the Eastern Kenai Peninsula across Prince William Sound to the Canadian Border. Heaviest precipitation will occur in the coastal zones, with lesser amounts spreading inland through Friday. -Kutz && .AVIATION... PANC...VFR conditions will persist. Confidence is higher today that the southeasterly Turnagain Arm wind will reach the ANC airport by late evening today.. However, the forecast challenge will be with regards to timing. The stronger southeasterly winds aloft have been staying in the 4000 to 5000 ft mountain top level and are expected to remain near this and not make it down to 2000 ft for true low level wind shear. && $$