Area Forecast Discussion
Issued by NWS Fairbanks, AK
Issued by NWS Fairbanks, AK
821 FXAK69 PAFG 222236 AFDAFG Northern Alaska Forecast Discussion National Weather Service Fairbanks AK 236 PM AKDT Sat Jun 22 2024 .SYNOPSIS... Broad upper-level high pressure extending across northern Alaska will continue to bring warmer than normal temperatures and thunderstorm activity. High temperatures in the 70s today for the Eastern and Central Interior reach into the lower 80s Sunday through at least Tuesday. Isolated to widely scattered thunderstorms across the Western Interior and along the Brooks Range today will slowly shift back into the Central and Eastern Interior over the coming days. Along the West Coast, onshore flow will contribute to increased fog and stratus through Monday. For the North Slope, a return to fog and stratus begins Sunday. && .DISCUSSION... Upper Level Analysis... An upper-level high is situated over the Western and Central Interior, with broad ridging otherwise extending across much of the state, leading to fairly warm and dry conditions for northern Alaska this afternoon. A weakening shortwave trough remains nearly stationary over the SE Interior and Yukon, providing upper-level support for isolated thunderstorms. Out west, a more potent shortwave extending from the Seward Peninsula to Southwest Alaska is pushing into the Western Interior with significant cloud cover and scattered to numerous rain showers. Additionally, weak troughing continues to slowly sink southward across the Brooks Range, bringing drier air into the Eastern and Central Interior. Surface Analysis... A thermal trough extends west from Yukon through the far SE Interior into Southcentral Alaska, with a weak extension northward into the Western and Central Interior. Weak surface high pressure extends across the marine areas of the Chukchi and Bering Seas, driving onshore winds and promoting cooler temperatures along the North Slope and West Coast. With the thermal trough over southern Alaska, northeasterly winds extend across the Eastern Interior, bringing in dry air which has dropped RHs into the 20s. An elevated unstable air mass moving in off the Arctic Ocean has brought a reprieve from fog and stratus, instead providing patchy altostratus/altocumulus which has largely remained out over the ice covered Arctic Ocean. Warm conditions with temperatures in the 70s with dew points in the upper 40s to lower 50s have allowed for the development of isolated to widely scattered thunderstorms from the Upper Kuskokwim Valley north to the Brooks Range where conditions have been clearer today east of the West Coast upper trough. Central and Eastern Interior... With the thermal trough axis situated to the south of the Alaska Range today, northeasterly winds have brought dry air across much of the Eastern Interior. Along with this dry air, another day with warm temperatures peaking in the mid to upper 70s is ongoing. Warm and dry conditions with modest northeasterly flow have increased smoke production with fires along the Tanana Flats, blowing the smoke off to the south and west. As high pressure remains over the Western and Central Interior this weekend, expecting convective potential to continue to be limited as a result. Despite generally stable/unfavorable conditions, a much weaker shortwave trough lingering over the far SE Interior is supporting some isolated thunderstorms this evening. For Sunday, a shortwave trough shifting east from the Seward Peninsula will support widely scattered thunderstorms over the north-central Interior. Thunderstorms make a return to the Eastern Interior early next week as the upper trough continues eastward. This will also be aided by the thermal trough which remains fairly broad but locates over the northeastern part of the state. This may lead to light southwesterly winds which could bring smoke back over the Richardson Highway from Monday onward. High temperatures in the low 80s also return tomorrow and remain likely through Tuesday as high pressure shifts back east into Yukon. West Coast and Western Interior... Upper-level high pressure centers over the Western Interior today, leading to another day with high temperatures in the 70s for the interior valleys of Western Alaska. Warm temperatures and increased instability will support isolated to widely scattered thunderstorms this evening across the Western Interior as a shortwave trough lingers across Western Alaska. An upper-level low dropping south from the high Arctic will entrain the northern half of the shortwave, pulling it northeast for Sunday, while the southern half digs and closes off over Southwest Alaska. This will lead to a split focus for thunderstorms on Sunday: a northern focus over the northwestern Interior and a southern one over the Upper Kuskokwim Valley, with more isolated activity in between. The upper-level high shifts back over the Eastern Interior as well, while high pressure builds over the Bering and Chukchi Seas. This will keep westerly flow bringing in cool, marine air along the West Coast and increase the potential for stratus/fog through Monday. Meanwhile, highs remain in the 70s over the Western Interior. For Tuesday, the upper high intensifies over Yukon, bringing south to southeasterly flow that spreads warmer temperatures to the north and west. North Slope and Brooks Range... An elevated unstable air mass moving in off the Arctic Ocean will continue to bring a reprieve from fog and stratus for the North Slope through Sunday. At the same time, a weakening surface high along the Arctic coast will mean northeasterly onshore flow relaxes somewhat this weekend. Tonight, an upper-level low drops south from the high Arctic, pushing its front to the Arctic coast. The air mass along and behind the front has exhibited low clouds, so anticipate a return of fog and stratus to parts of the coastline as early as Sunday morning. Fog/stratus is likely to lift or burn off each day, but return at night. Along the Brooks Range, isolated thunderstorms are likely to develop each day. Extended Forecast Days 4-7... The latter half of next week looks to be warm and dry for much of Interior Alaska and the North Slope as a strong upper-level ridge looks to establish over Eastern Alaska and Yukon. Temperatures could hover around 5 to 10 degrees above normal from Wednesday through next Saturday in the Eastern and Central Interior, with even larger departures from normal possible on the North Slope. This will enhance fire weather concerns, especially with the additional threat of thunderstorms present as a series of shortwave troughs rides up the western periphery of the ridge. To the west, a potentially gale-force low lifts into the Bering Sea mid-week. There is less model support for a continued push northward compared to yesterday, which suggests lower potential for an elevated surf threat. Regardless, low pressure over the Bering/Southwest Alaska will bring increased chances for precipitation to the West Coast and Western Interior, keeping temperatures near to slightly above normal. Coastal Hazard Potential Days 3 and 4...None. && .FIRE WEATHER... Warm and dry conditions continue this weekend with high temperatures in the 70s and RHs dipping to between 20 and 30 percent in the Eastern and Central Interior. Expect a warming trend as high pressure shifts back east and strengthens heading into next week. This evening, near red flag conditions are ongoing in portions of the Eastern Interior where temperatures in the 70s, RHs near 25 percent, and northeasterly winds around 10 mph are coincident in places. Widely scattered thunderstorm activity focuses over the Western Interior and Brooks Range this evening, with some isolated storms over the far SE Interior. This activity will shift into the Central Interior for Sunday and Monday and into the Eastern Interior for next week. There is some uncertainty in how dry conditions will remain over the Eastern Interior that depends on the strength and placement of the upper level ridge, which leads to decreased confidence in the coverage and intensity of thunderstorm activity for Monday and Tuesday. However, generally expecting some moisture recovery as westerly winds bring moisture currently located over Western Alaska into the Interior. && .HYDROLOGY... Recent heavy rains have led to higher water levels along the Fortymile River, but drier conditions expected over the next several days will allow water levels to fall this coming week. Glacial fed rivers may begin to rise as warming temperatures lead to increased high elevation snowmelt. && .AFG WATCHES/WARNINGS/ADVISORIES... AK...None. PK...None. && $$ Quesada