Area Forecast Discussion
Issued by NWS Fairbanks, AK
Issued by NWS Fairbanks, AK
654 FXAK69 PAFG 100023 CCA AFDAFG Northern Alaska Forecast Discussion...CORRECTED National Weather Service Fairbanks AK 423 PM AKDT Thu May 9 2024 .SYNOPSIS... Shower chances will persist over the next several days. A combination of rain and snow showers are expected over the Yukon Delta, Seward Peninsula, and areas along the Arctic Coast. Locations farther inland and at lower elevations can expect mainly rain showers. There is a small chance of thunderstorms over portions of the Interior both north and south of the White Mountains through this evening. Storm chances for Friday will push a little farther north, primarily over the Yukon Flats. Strong southerly winds aloft will translate to strong southerly gap winds of 15 to 30 mph with gusts to 45 mph expected near Delta Junction and the eastern Alaska Range Friday night and Saturday morning. && .DISCUSSION... Model Analysis... 12Z deterministic models appear to have initialized better than the 00Z set. At 500mb GFS, NAM, and ECMWF were still 2 dam (decameter) too low over northwest Alaska compared to the 12Z radiosonde flights and matched up well with the upper-level low over the eastern Aleutians. Inverted trough arced from the eastern Aleutian upper low over the Bering Sea west of the Yukon Delta to northeast Russia. A trough of low pressure, remnant of an filling upper low, jutted northward over the Seward Peninsula into northwest Alaska. Lobes of vorticity were noted near Utqiagvik and over the Alaskan Panhandle which will continue to propagate cyclonically around the state, which will lead to enhanced forcing for ascent. At the surface at 12Z, several areas of low pressure were identified. A broad area of low pressure stretched from near Norton Sound eastward across the Interior. Satellite imagery revealed several focused circulations near Galena, Rampart, and near Fort Greely. Expect those areas of low pressure to slowly strengthen today and rotate cyclonically north and eastward. Look for enhanced shower potential and a few thunderstorms this afternoon. Today through Saturday... Diurnal showers and a few thunderstorms will continue to percolate through this evening over the Interior. Mixed layer CAPE values a high as 100-150 J/kg is forecast from the north slope of the Alaska Range as far north as the White Mountains and Yukon Flats. Hodographs over that area are straight in the lowest 3 km with around 30-35 knots of 0-3km shear. Tall skinny CAPE profile in conjunction with falling heights aloft should be sufficient for a few thunderstorms. A heavy shower passed over our office a few hours ago and produced very small hail. Expect a few of the stronger cells to be capable of small hail in addition to a few lightning strikes. As sun angle lowers later this evening, instability will diminish and showers will gradually weaken. Portions of Northwest Alaska, generally south of Utqiagvik to Nome and Unalakleet will be under the northern lobe of vorticity and should continue to see overcast skies and light snow. Snow accumulations of 1 to 4 inches are expected. In the wake of the upper trough from Utqiagvik east along the Arctic Coast have seen forcing for ascent and clearing skies. Lower snow totals are expected over the Yukon Delta as temperatures will trend warmer. A few spots may pick up an inch or two, particularly in the higher elevation areas. The broad upper level pattern will continue to see cyclonic flow aloft. The light snow over Northwest Alaska will push out over the Chukchi Sea and the Bering Straight. Diurnal showers are forecast again for the Interior Friday. A few thunderstorms are forecast again, although the focus will be farther north, generally north of the White Mountains and across the Yukon Flats. South of the White Mountains, isolated to scattered showers are expected. Another surge of stronger winds aloft will arrive over the Alaska Range Friday afternoon and evening which will generate gap flow through the passes. The strongest winds will be found from Isabell Pass to Fort Greely and Delta Junction where south winds of 15 to 30 mph and gusts to 45 mph are forecast Friday night into Saturday morning. An upper-level trough will accompany those stronger winds and will arrive over the eastern Interior and the ALCAN border Saturday afternoon. Another day of showers and perhaps a few thunderstorms are forecast for the Yukon Flats. Extended Forecast Days 4-7... Model guidance continues to indicate persistent broad upper level troughing over most of the forecast area throughout the extended forecast period. Periodic intrusions of ridging from Canada into the eastern Interior are also suggested. This pattern will continue to support scattered showers across much of northern Alaska. Model solutions gradually disperse Sunday and beyond, suggesting lower than average overall confidence in the forecast beyond Day 3 Saturday. Coastal Hazard Potential Days 3 and 4...None. .FIRE WEATHER... High temperatures in the 50s to near 60 through Friday. Scattered to numerous showers this evening throughout the Interior as a disturbance moves through the region tonight. Slight chance of thunderstorms this afternoon and early this evening over the Fairbanks area and the Yukon Flats north of the White Mountains. The thunderstorm threat will shift north for Friday with areas in the Yukon Flats seeing the greatest potential for storms, around 5 to 10 percent. Isolated to scattered showers will remain throughout the weekend as more disturbances move through the area. Southerly gap winds of 15 to 30 mph with gusts to 45 mph are forecast Friday night and Saturday morning from Isabell Pass to Delta Junction areas. Near-critical fire weather conditions are possible with RH values of 35 to 25 percent. && .HYDROLOGY... The breakup front on the Yukon river is approaching Circle and expected to reach Circle in the near future. As of 2 pm Thursday, an ice jam was in place 12 miles upriver from Circle with some overbank flooding of low areas although no water over higher banks. The ice continued to deteriorate since Wednesday afternoon and there is a clear path through the south channel at Circle. Downstream of Circle, small sloughs and streams are clearing of ice, but the main channel of the Yukon still has ice in-place. The Tanana and Upper Kuskokwim River are mostly open. Rivers north of the Yukon River have mostly intact ice. && .AFG WATCHES/WARNINGS/ADVISORIES... AK...Flood Watch for AKZ833. PK...Heavy Freezing Spray Warning for PKZ806. && $$ Huyck