Scientific Forecaster Discussion
000 FXAK69 PAFG 162351 AFDAFG Northern Alaska Forecast Discussion National Weather Service Fairbanks AK 351 PM AKDT Tue Jul 16 2019 .SYNOPSIS... Highlights are: Temperatures and humidity will see little change through Thu, then cooling temps and rising RH on Fri and into the weekend. Isolated to widely scattered thunderstorms across all of Interior Alaska and the Seward Peninsula today, will decrease from the west to be over the Central and Eastern Interior on Wed, over the southeast Interior Thu, and then just southeast of Tok on Fri. Expect between 0.10 and 0.50 inch of rain across most of the Southern Interior and Brooks Range through Thu, while the northern Interior remains mainly dry through Thu. Smoke has thinned in most areas, but expect it to get thicker over the Northern Interior over the next few days, especially near Chalkytsik where conditions will remain mainly dry. Aloft... A weak ridge over the Northern Interior of Alaska will persist through Wed, then build over the southern Interior and South Central Alaska Thu and Fri, then rebuild over the Interior early next week. Conditions will remain near seasonal temperatures through Thu, then cool and become wetter on Fri and Sat, before warming again next week. A weak short wave trough from the YK Delta to Arctic Village will weaken in place tonight. There are isolated to widely scattered thunderstorms along much of this trough now that will diminish tonight. A second weak short wave from Delta Junction to Eagle will move to McGrath to Fairbanks by 4am Wed, then move south. This has a band of showers and isolated to widely scattered embedded thunderstorms associated with it. Widely scattered thunderstorms will develop southeast of the trough this evening. The areas of widely scattered thunderstorms across the southern and Central Interior will have gusty winds, brief heavy rain, and small hail associated with them. A third short wave now over the southern Yukon Territory will move to Delta Junction to Eagle by 4pm Wed, then to Delta Junction to Old Crow by 4am Thu. This will cause isolated to widely scattered thunderstorms along this trough as well. Surface... A 993 mb low 80 NM north of Utqiagvik will move to 120 NM north of Barter Island as as 995 mb low by 4am Wed, then move to 150 NM northeast of Barter Island as a 1000 MB low by 4pm Wed, then continue east. A cold front stretching west from this low will move to Nuiqsut to Point Hope by 4am Wed, to Barter Island to Kivalina by 4pm Wed, then weaken. Expect rain and fog along the front and West winds 10-20 kt. Winds and rain will diminish West of the front. A second and much stronger cold front will move to the Eastern Chukchi Sea by 4am Thu, to just east of Pt Barrow to Point Hope by 4pm Thu, to Nuiqsut to the Bering Strait by 4am Fri, and to Demarcation Point to Arctic Village to Norton Sound by 4pm Fri. Expect rain and fog and West winds 15-25kt along the front, and temperatures to fall about 10F behind the front. A thermal trough stretching from Bethel to Arctic Village will move to McGrath to Arctic Village by 4pm Wed, to Northway to Arctic Village by 4pm Thu, then dissipate along the Alcan Border Fri. Will see West winds increase to 10 mph along the trough Wed and Thu. && .DISCUSSION... Models all initialize about 10m too low on h500 heights over Northern AK at 12Z. Models show similar solutions through Thu, but after that the NAM is much deeper than the GFS and ECMF with a short wave moving over the West Coast and Northern Interior on Fri. Since models initialize the strength of the Ridge over Alaska too weak, we do not favor the deeper NAM with this feature on Fri. GFS solution is midway between the NAM and ECMF on the strength of this feature and is the favored solution at this time for Fri. Models differ on areal coverage. We prefer the broader areal coverage shown by the GFS and ECMF and using a blend of them. At the surface at 15Z, all models verify 3 mb too weak on the low just north of Utqiagvik. Expect this feature to remain 3 mb deeper through 4am Wed, and as a result expect winds in the vicinity of the low be 3-5kt stronger than models indicate over the Arctic Coast through tonight. Coastal Hazard Potential Days 3 and 4... Slightly elevated surf along the coast Fri and Sat. Much uncertainty on where this might occur and how strong, but will not be major event. && .FIRE WEATHER... Temperatures and humidity will see little change through Thu with highs 70 to 80, and RH 25 to 45 with the warmest temps and driest conditions today and Wed in the Northern Interior. Expect cooling temps and rising RH on Fri and into the weekend. Isolated thunderstorms across the Interior and Seward Peninsula today with widely scattered thunderstorms in the southern Interior today. Wed, expect Isolated PM thunderstorms in Central and Eastern Interior with widely scattered PM thunderstorms in zones 220 221 222 223 and north slopes of 225 and 226. Thu expect isolated thunderstorms Southeast of Denali to Old Crow. Fri isolated thunderstorms southeast of Tok. Expect between 0.10 and 0.50 inch of rain across most of the Southern Interior and Brooks Range through Thu, while the northern Interior remains mainly dry through Thu. Smoke has thinned most areas, but expect it to get thicker over the Northern Interior over the next few days, especially near Chalkytsik where conditions will remain mainly dry. && .HYDROLOGY... Freezing levels near 8000 ft and remaining steady through Thu, then beginning to fall. Expect glacial fed rivers to remain at current high levels through Fri, then begin to fall slowly. Clear rivers and streams will remain at or below normal levels. && .AFG WATCHES/WARNINGS/ADVISORIES... None.