textproduct: Fairbanks

SYNOPSIS

Isolated thunderstorms continue over Fortymile Country, the Central/Eastern Brooks Range, and the northern portions of the Interior through Saturday night. A warming trend is expected across most of the Interior tomorrow with a shortwave moving northward across the Central Interior, allowing southerly flow to reestablish. A series of wind advisories have been issued for the strong winds expected to accompany the eastward progression of a Bering low. Broad troughing is looking to setup over western Alaska which will allow for multiple wetting rain opportunities through the start of next week.

KEY WEATHER MESSAGES

Central and Eastern Interior... - Highs in the 70s and 80s are expected in Interior valleys today and Saturday, with a heat advisory in effect for the Yukon Flats where temperatures will reach around 85F. Temperatures will begin a cooling trend from west to east beginning Sunday.

- Isolated thunderstorms are most likely to form over the White Mountains this afternoon, but could also develop the Yukon Flats and Fortymile Country. Saturday, coverage shifts back towards the Central Interior, over the Dalton Highway Summits and White Mountains north of Fairbanks.

- Southerly gap winds through the Alaska Range will strengthen Saturday afternoon, with potential gusts up to 50 and 60 mph respectively through Isabel and Windy Pass.

- A Wind Advisory is in effect for the western portion of FNSB on Saturday, including Fairbanks, for potential gusts up to 40 mph.

West Coast and Western Interior... - Highs are expected to reach the lower 70s in Western Interior valleys today. Along the coast, highs will be in the 50s/60s. Temperatures will cool as widespread rain sweeps across the region from south to north on Saturday.

- Widespread wetting rain will arrive in the YK Delta this afternoon and travel north through the region through Saturday. The current track of the low supports half an inch or more in the the YK Delta and Southern Seward Peninsula on Saturday, around a quarter in the lower to middle Yukon Valley, and less than a quarter in most other regions. - Winds lull tonight before strengthening again Saturday with the arrival of the next system from the Bering. Areas along the coast will see gusts up to 35 to 45 mph. Farther into the Interior, gusts will reach 25 to 35 mph. Winds will weaken slightly on Sunday, but remain gusty through the weekend. - A wind advisory is in effect on Saturday for southern portions of the Western Interior for potential gusts up to 40 mph.

- Fog and low stratus have moved in from the Bering along portions of the West Coast and will linger through the weekend.

North Slope and Brooks Range.. - Max temperatures on the North Slope will cool Friday, peaking closer to 70 through the weekend, and into the 60s on Monday. Temperatures along the coast will be cooler, in the 50s and low 60s, and in the 40s around Utqiagvik.

- Scattered thunderstorms are expected in the central and eastern Brooks Range this afternoon. The best chances will be in an area from Anaktuvuk Pass to Arctic Village.

- Widespread rain will reach the Western Brooks Range from the south on Saturday and may continue into the Western North Slope on Sunday.

FORECAST ANALYSIS AND DISCUSSION

A more active pattern is looking to settle in over the state as the week comes to a close. The upper-level pattern shows a broad ridge over the eastern half of the state. Looking west, a Bering low continues to move eastward and broad troughing is looking to settle in across western Alaska by the start of the weekend.

Attention turns to a shortwave associated with the Bering low, that will work its way E/NE across the Kuskokwim Valley Friday night into Saturday. This will help push the ridge over eastern Alaska farther east. It is expected to hold onto its strength, and this results in the shortwave deviating from its NE track, turning more northward. A southwest to northeast oriented low- level jet is expected to accompany this system, resulting in widespread between 35 and 45 mph across western Alaska through late Saturday night. Cold air advection (CAA) from this trough will also aid in mixing down these stronger winds to the surface. This system will also be tapping into a sufficient amount of moisture which will provide multiple days of widespread wetting rains across Western Alaska through the start of next week.

With the shortwave's track becoming more northward, this will result in southerly flow setting up across eastern Alaska. As the shortwave moves up the Central Interior on Saturday, strong winds are expected to pick up through the Alaska Range Passes and western portions of FNSB. Some of these winds could spread farther east depending on how far east the CAA is expected to travel. Generally, southerly flow keeps areas north of the Alaska Range dry, but given the strength and moisture content of the shortwave, an isolated shower cannot be ruled out. This is a textbook Chinooking pattern which will allow temperatures to warm a bit more on Saturday. One caveat to the strong winds and warmer temperatures across the southern Interior will be how much cloud cover moves in during the morning hours. CAMs and soundings show a sufficient amount of scattered to clear skies can be expected through the early afternoon.

Looking to the northern portion of the Interior, the shortwave will continue to allow for afternoon chances for thunderstorms. With the southerly flow aloft, some of these storms could be on the lighter side in regards to precipitation. Looking at some of the soundings, LCL heights are showing the potential to be between 8 and 10 kft. This would allow for a sufficient amount of DCAPE, which could lead to very strong outflows from any storms that form. This could lead to some fire weather concerns. More on this in the Fire Wx portion of the discussion.

Conditions will begin to cool down in the Central and Eastern Interior on Sunday as the trough gradually bumps the ridge off to the east. Only light showers will make it into the Central and Eastern Interior as most of the heavier precipitation stays to the West. The cloudier and cooler conditions will limit thunderstorm development to the Al-Can Border through the early parts of next week. Broad troughiness over the western portion of the state will continue into the middle parts of the week, with ridging shifting farther east into Canada.

FIRE WEATHER

Friday will likely be the last warm/dry day for much of the west as an extensive trough sets up across the Bering, pushing multiple waves across the west, responsible for widespread wetting rains, breezy southerly winds, cool temps, and high RH. Troughing continues through next week, bringing ample opportunity for wetter/cooler conditions, severely limiting fire weather.

As the west soaks, southerly flow becomes firmly established over the Central/Eastern Interior, where 850mb temperatures near 15C bring surface temps back into the 80s. Mid 80s, perhaps the upper 80s, in the Yukon Flats and low to mid 80s across much of Tanana Flats, upper 70s east to the ALCAN border. Gusty winds are a certainty in the AK Range passes, where 40 to 60 mph winds are forecasted. A Red Flag issuance is not likely for Delta Junction; record rains on Wed/Thursday have left their mark. One note, gusty southwesterly winds as high as 40 mph could make it as for north as Fairbanks on Saturday.

Now on to thunderstorms, the north/central Interior east thru the Flats look to see pretty strong thunderstorms Saturday, with some storm indices the strongest weve seen this season. Outflow winds look particularly strong, perhaps leaning into the 40 to 50 mph range. These storms will be prolific lightning producers with the main question on if these storms will be wet or dry. Likely dry in the afternoon with wetter cells Saturday evening.

HYDROLOGY

Water levels are expected to continue dropping along the Tanana River and its tributaries throughout the weekend.

EXTENDED FORECAST DAYS 4-7

The overall pattern becomes increasingly progressive through the extended period with a series of low pressure systems tracking through the Bering Sea. This maintains a broad cyclonic flow over Western Alaska and prevents meaningful ridging from reestablishing across mainland Alaska. While model guidance differs on the timing and strength of individual lows, ensemble guidance remains in good agreement on the larger scale pattern.

Each passing system will send embedded shortwaves across Alaska, providing periodic episodes of ascent and reinforcing a cooler and more unsettled pattern. Cloud coverage will remain high across the West Coast and Western Interior, gradually expanding eastward as each disturbance moves inland. This increased cloud cover will support slightly below seasonal norm temperatures across the West Coast and into the Western Interior throughout the period. Cloud cover is expected to increase into the Central and Eastern Interior throughout the week, helping moderate temperatures across the area. Expect multiple rounds of showers across Western and Northern Alaska, with precipitation becoming more scattered as it pushes into the central and eastern Interior. Afternoon heating could still support some afternoon thunderstorm development across portions of the Eastern Interior and Eastern Brooks Range, though this will depend on daytime cloud cover and instability development. Winds will generally be southerly to southwesterly, becoming locally stronger along the West Coast and through terrain as each low brings a tighter pressure gradient.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...Wind Advisory for AKZ849. Wind Advisory for AKZ830-852. Heat Advisory for AKZ833. Red Flag Warning for AKZ933. Wind Advisory for AKZ841-844-845. Wind Advisory for AKZ847. PK...Gale Warning for PKZ801. Small Craft Advisory for PKZ802. Small Craft Advisory for PKZ806-807-854-856. Small Craft Advisory for PKZ811-857-858. Small Craft Advisory for PKZ850.