textproduct: Fairbanks

SYNOPSIS

Today is another warm day across most of Northern Alaska, with widespread highs in the 70s and 80s except in coastal areas. Scattered to numerous thunderstorms are expected from the Middle Yukon Valley northward across the western Brooks Range and North Slope. Extensive rainfall is expected in parts of the southwestern Interior near the Alaska Range and in the Upper Tanana Valley and southern Fortymile areas. Cooler temperatures are expected in the southern Interior on Thursday, with sparser thunderstorm activity, mostly limited to the northern Interior and Brooks Range, with warm weather persisting elsewhere. Southern Interior valleys warm up again by Friday, with increasing rain chances heading into the weekend as another weather system moves in.

KEY WEATHER MESSAGES

Central and Eastern Interior... - Highs in the 70s and 80s are expected across the area, with a heat advisory in effect for the Yukon Flats. Temperatures cool in the southern Interior late today into Thursday.

- Heavier rain is expected in the southern Interior this evening into Thursday. Most of the Fortymile Country and Upper Tanana Valley may receive from a few quarters to near an inch of rain, with up to an inch or more in the Alaska Range.

- Isolated thunderstorms will be possible from the White Mountains to Tanana northward and northern Fortymile Country this evening, expanding to the AlCan Border on Thursday and Friday.

West Coast and Western Interior... - Scattered to isolated thunderstorms are expected this afternoon in the Western Interior from the Middle Yukon Valley to the Kobuk Valley.

- Heavy rainfall along the northern slopes of the Western AK Range and in the Upper Kuskokwim Valley could support rain totals ranging from around half an inch to an inch and a half.

- Temperatures cool slightly with highs in the mid to upper 70s in Interior valleys today dropping into the lower 70s Thursday. Along the coast, highs will be in the 50s/60s.

- Stronger southwesterly/westerly winds will develop this afternoon, and gusts up to 20 mph will be possible throughout the western Interior Valleys through Thursday night.

North Slope and Brooks Range.. - Warm temperatures persist through Thursday. Highs warm into the 50s near Utqiagvik to the low 80s in the Arctic Plains. A heat advisory is in effect for the Arctic Plains for Thursday.

- Max temperatures on the North Slope will be closer to 70 on Friday and Saturday, and into the 60s on Sunday.

- Scattered thunderstorms will be possible in the Brooks Range and Western Arctic Plains today. They will shift to the Central Brooks Range on Thursday and the eastern Range on Friday.

FORECAST ANALYSIS AND DISCUSSION

Ridging centered over Nunavut in Canada (where 500 mb heights cap out at around 570 dm) extends well to the west across most of Northern Alaska, where 850 mb temperatures range from the high single digits in Western Alaska to as high as nearly 17C over remote portions of the eastern Brooks Range. This will coincide with surface temperatures reaching into the 70s and 80s across the Interior and southern North Slope. A vertically-stacked low over the western Gulf of Alaska has helped bring plentiful moisture into southwest Alaska since yesterday; with a robust shortwave trough shifting westward just north of the Alaska Range, widespread showers and isolated thunderstorms will be possible from the Western Alaska Range to northwest of Takotna. With the showery nature of this precipitation, specific totals in single locations could range from around half of an inch to an inch and a half across these areas through Thursday morning.

Farther north in the Western Interior/Brooks Range and in the Arctic Plains, surface-based CAPE will broadly reach at least a few hundred J/kg; SBCAPE could exceed 1000 in the west-central Interior. LIs are forecast to range from 1C to 3C in most of these areas, with some areas approaching 4C. This coupled with the stronger shortwave in the southwestern Interior and a weaker one moving across the eastern Chukchi Sea will support scattered thunderstorms from the Middle Yukon Valley north, with more isolated storms possible in the northeastern Interior.

A second low over southeastern Alaska is pulling robust moisture into the southeastern Interior, including the Fortymile Country and the Upper Tanana Valley. This will allow for widespread rainshowers which could support rain accumulations of half an inch to an inch, with higher totals possible in the areas with the best upsloping effects, especially along the slopes of the eastern Alaska Range. Farther southeast toward Northway, rain totals are likely to be considerably lower, although some light accumulations are still possible.

Moving into Thursday, warm temperatures will continue across most of the area, with the southern Interior being cooler with scattered to numerous showers and extensive cloud cover spreading westward. The Yukon Flats will likely see another day in the low to mid 80s with the ridge directly overhead, with mid to upper 70s expected elsewhere in the northern Interior and Arctic Plains. Isolated thunderstorms will be possible from the White and Ray Mountains northward and in the higher terrain of the eastern Interior. Numerous showers will be possible in the Brooks Range, with southerly to southwesterly flow across the mountains. By Thursday night, showers in the southern Interior will dwindle. Westerly gradient winds will increase in Western Alaska and could gust to 20 to 25 mph in the valleys, with somewhat stronger southerly winds through the Bering Strait and in adjacent areas.

On Friday, better thunderstorm chances return to the Eastern Interior, especially from the Upper Yukon Valley/Fortymile Country northwestward to the Central and Eastern Brooks Range. Up to a few hundred J/kg of SBCAPE and LIs as low as about 2C will be possible in these areas. Cooler temperatures are expected on the North Slope Friday as the ridge shifts eastward and shower activity increases, but highs could still reach into the upper 60s or low 70s in the Arctic Plains. The westerly winds in Western Alaska will diminish as the pressure gradient falls off, with southerly to southwesterly winds expanding to the western Arctic Coast and Brooks Range.

FIRE WEATHER

Thursday, a longwave trough begins to dig south from the Russian coast, becoming firmly established over the Bering. This feature will be responsible for moist southerly flow across the west, bringing increased chances for wetting rains, and significantly moderating fire weather concerns from the lower Tanana into the coast, including the Seward Pen. Associated with this pattern will also be elevated west to northwest winds impacting much of the coast into the Tanana, with a focus of strongest winds in the Kobuk Valley. As the west cools down these breezy westerly winds push thunderstorms into the Central/Northern Interior, with storms becoming more isolated, shifting further into the Eastern Interior over the weekend. Focus for hot/dry over the weekend continues to be the Yukon Flats where temps in the mid 80s and min RH near 30 percent is forecasted, trending slightly cooler by next week.

All eyes on the long range pattern, with general troughing over the west and a low in the Gulf of Alaska. Main question is the location and extent of a ridge from Yukon/Northwest Territories and how it could shift west into the Interior. We will likely continue to see daily wet thunderstorms out east next week, with southerly flow likely helping to dry out the Tanana Valley.

EXTENDED FORECAST DAYS 4-7

Models have a general agreement that an upper-level low pressure system will make its way into the Bering Strait on Saturday morning, with weak ridging in the northeastern portion of the state extending towards the southwest. This ridging is expected to weaken and break down throughout the day as the Bering Strait low begins to push south. Where the low pressure system ultimately ends up is still highly uncertain between models, but an overall troughiness is expected to influence the weather throughout the remainder of the weekend. This pattern will bring scattered showers to the state through Tuesday with most of the showers predominantly in the YK Delta and across the West Coast/Western Interior. However, a round of precipitation is possible Monday afternoon across portions of the Upper Tanana Valley, Fortymile Country, and eastern Alaska Range as moisture from a lingering low in the Gulf wraps around the terrain. Uncertainty remains regarding specific precipitation timing, location, and intensity, but impacts are expected to remain low. Showers generally become more isolated through Tuesday.

Starting Tuesday, models begin to hint at a pattern change with some models showing a ridge building in across the eastern portion of the state. Model agreement for ridging potential remains poor at the moment but we will continue to monitor these changes for any potential impacts as confidence grows.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...Fire Weather Watch for AKZ916-918-919-928. Heat Advisory for AKZ833. Heat Advisory for AKZ806-808. PK...Small Craft Advisory for PKZ804. Small Craft Advisory for PKZ805. Small Craft Advisory for PKZ852.