Area Forecast Discussion
Issued by NWS Fairbanks, AK
Issued by NWS Fairbanks, AK
771 FXAK69 PAFG 192322 AFDAFG Northern Alaska Forecast Discussion National Weather Service Fairbanks AK 322 PM AKDT Wed Jun 19 2024 .SYNOPSIS... Upper-level ridging will continue to bring generally warm temperatures and thunderstorm chances across northern Alaska. High temperatures will hover in the 70s across the Interior through Saturday, with cooler temperatures along the coast. Isolated to widely scattered thunderstorms are expected for the Interior each afternoon. A Dense Smoke Advisory is in effect for visibility one mile or less in smoke along the Richardson Highway between Salcha and Birch Lake. For the North Slope, high pressure will promote intermittent fog and stratus along the coast. && .DISCUSSION... Upper Level Analysis... A closed upper-level low is situated over the Gulf of Anadyr this afternoon, while broad ridging extends up from Western Canada, across Interior Alaska, into the Chukchi Sea. A shortwave trough is dipping southward over the Beaufort Sea on the east side of the ridge, with a weaker second shortwave lifting along its western periphery across the Central Interior, aiding the support of showers and thunderstorms in the area. Surface Analysis... A thermal trough extends northwest from Yukon along and south of the Brooks Range, aligning well with the upper level ridge. Surface high pressure is present in the Chukchi Sea with a ridge along the Arctic coast. Winds are generally much lighter across the forecast area today with the dissipation of the weak low in the Chukchi Sea. The exception is northeasterly winds which continue across much of the North Slope, advecting a layer of stratus and fog in off the ice. Warm conditions with temperatures in the 60s and 70s with dew points ranging from the 40s into the low 50s have allowed for the development of ongoing scattered to numerous rain showers and widely scattered thunderstorms across the Eastern and Central Interior. Central and Eastern Interior... Temperatures will peak broadly in the mid to upper 70s once again this afternoon, with locations on the Yukon Flats likely seeing temperatures reach 80 degrees again today. Widely scattered thunderstorms continue this evening primarily over the high terrain of the White Mountains and Fortymile Country, with storms also moving southward off the Central and Eastern Brooks Range. Elsewhere, isolated thunderstorms are possible. A potent shortwave lifting into Southcentral Alaska will shift the focus of convective activity further south for Thursday as another shortwave trough dips south of the Brooks Range. Expect slightly cooler temperatures, especially in the Upper Tanana Valley near Northway as quite a cloudy, wet day looks to shape up. High pressure builds along the Arctic coast, bringing a shift from southwesterly to northeasterly winds on Thursday. Some areas in the Yukon Flats could see winds gust up to 25 mph Thursday, Friday, and Saturday afternoon/evening. The upper-level trough digs south of the Brooks Range into the Eastern Interior on Friday, pinching off the ridge and relegating the best thunderstorm potential to a corridor along and just north of the Alaska Range, with some isolated storms remaining possible in the Central Interior. The pattern remains similar for Saturday, though convective potential looks to be even lower as the thermal trough dips south of the Alaska Range. West Coast and Western Interior... A cool, stable marine air mass is being drawn up along the western periphery of the ridge over Interior Alaska, covering much of the West Coast and Western Interior with stratus and dense fields of low-topped cumulus this afternoon. This will limit instability sufficient for thunderstorms to only allow isolated coverage for portions of the Western Interior today. The upper-low that had been bounding the upper-level ridge over the past few days continues westward over Chukotka tonight, allowing the ridge to extend west. Temperatures warm up, with highs in the 70s expected for the Kobuk and Noatak Valleys, as well as interior valleys of the Seward Peninsula beginning tomorrow and continuing through Saturday. Thunderstorm activity spreads west, with widely scattered storms expected on Thursday in the Western Interior. The Western Interior becomes the focus for convective activity by Friday and Saturday as the upper level ridge is pinched off to the east and centers over Western Alaska. North Slope and Brooks Range... High pressure will remain entrenched along the Arctic coast, allowing northeasterly onshore flow to persist. This will bring stratus and fog along and near the coast each night, with the greatest solar heating during midday contributing to lifting fog/clearing skies. Isolated to widely scattered thunderstorms are ongoing along the south side of the Brooks Range this afternoon and will push southward into the Interior this evening. A digging upper trough will bring less favorable conditions for thunderstorms the rest of the week, keeping coverage isolated and confined primarily to the Brooks Range through Saturday. Extended Forecast Days 4-7... A fairly blocky, stagnant pattern is expected with an upper-level low over the Arctic Ocean looking to drop southward into Northern Canada for midweek and a ridge, possibly closed off, somewhere over Western Alaska. As a result, there is potential for the upper low to bring wetter conditions to the Brooks Range next week, with the accompanying cooler air mass generally inhibiting thunderstorm potential for the Eastern Interior. There is significant uncertainty in the exact placement of features, such that if the upper low remains over the Arctic Ocean (as the 12z GFS depicts) instead of dropping south, drier conditions in the Brooks Range with greater thunderstorm coverage across the Interior is possible. Otherwise, generally drier and warmer than average conditions are expected, leading to continued fire weather concerns. Coastal Hazard Potential Days 3 and 4...None. && .FIRE WEATHER... Temperatures will peak broadly in the 70s across the lower elevations of the Interior through the end of the week. RHs generally remain above 25 percent through Friday. Widely scattered thunderstorms continue this evening primarily over the high terrain of the White Mountains and Fortymile Country, with storms also moving southward off the Central and Eastern Brooks Range. Elsewhere, isolated thunderstorms are possible. A potent shortwave lifting into Southcentral Alaska will shift the focus of convective activity further south and increase moisture over the Southeast Interior for Thursday. As a result, there will be increased chances for wetting rains in the area on Thursday, and to a lesser degree on Friday. High pressure builds along the Arctic coast, bringing a shift from southwesterly to northeasterly winds on Thursday. A shortwave trough dipping south of the Brooks Range at the same time will bring dry air aloft, which could mix down to the surface with the combination of warm temperatures and gusty northeasterly winds in the Yukon Flats. This could potentially drop RHs as low as 20 percent, though it will be dependent on the timing of the shortwave, which if it arrives later Thursday night, would not allow for RH to drop that low. Otherwise, some areas could approach red flag conditions, with temperatures in the 70s, RHs in the 20s, and northeasterly winds sustained at just below 15 mph. Gusty northeasterly winds continue for the Yukon Flats each afternoon through Saturday, though some recovery in moisture is expected. The upper-level trough digs south of the Brooks Range into the Eastern Interior on Friday, relegating the best thunderstorm potential to a corridor along and just north of the Alaska Range, with some isolated storms remaining possible in the Western and Central Interior. The pattern remains similar for Saturday, though convective potential looks to be even lower as the thermal trough dips south of the Alaska Range. However, RHs trend slightly downward for Saturday as the digging trough spreads drier air across the whole of the Interior. && .HYDROLOGY... River levels on the North Slope continue to fall. The main threat (though low) is flash flooding with slow moving thunderstorms across the Eastern Interior today over steep terrain. There is some increased risk on Thursday and Friday over the SE Interior and Alaska Range where ample moisture will lead to the potential for heavy rain-producing thunderstorms. && .AFG WATCHES/WARNINGS/ADVISORIES... AK...Dense Smoke Advisory for AKZ840. PK...Small Craft Advisory for PKZ812. Small Craft Advisory for PKZ858. && $$ CQ