textproduct: Fairbanks

SYNOPSIS

Warm weather continues in the northern half of Alaska with isolated to scattered thunderstorms expected in the northwest on Wednesday. In the southern half of Alaska it will be cooler and wetter, with between a quarter and a half an inch of rain possible for a large swath of the southern Interior through Thursday. Westerly winds in the West Coast and Western Interior will strengthen Wednesday evening through Thursday evening. Friday and Saturday, the Interior will warm back up ahead of a new system arriving on the West Coast.

KEY WEATHER MESSAGES

Central and Eastern Interior... - Warm and dry conditions persist in the northern Interior through Saturday. Daytime temperatures in the mid 70s and low 80s are expected. A heat advisory is in effect for the Yukon Flats for highs near 85F again Wednesday. Temperatures cool in the southern Interior late Wednesday into Thursday.

- Heavier rain is expected in the southern Interior Wednesday evening into Thursday. A swath from Fortymile Country to the Tanana Valley to the Kuskokwim Valley may receive up to a few quarters of an inch of rain and up to an inch or more in the Alaska Range.

- Isolated thunderstorms will be possible across much of the Central Interior Wednesday afternoon. They are expected to develop mostly over the Ray Mountains and northern White Mountains, but may also form over high terrain farther east.

- Southerly winds gusting up to 50 mph through the Alaska Range passes will die down by Wednesday afternoon.

West Coast and Western Interior... - Scattered to isolated thunderstorms are expected Wednesday 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 a quarter of an inch to over an inch.

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

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

North Slope and Brooks Range.. - Hot temperatures will continue through Thursday. Daytime temperatures warm into the 50s near Utqiagvik to the low 80s on the eastern 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 Wednesday. Then they will shift to the Central Brooks Range on Thursday and the eastern Range on Friday.

FORECAST ANALYSIS AND DISCUSSION

A pair of lows, a 544 decameter in Bristol Bay and a 549 dam over the Panhandle, are responsible for cooler and wetter conditions in the Southern Interior Wednesday and Thursday. A ridge positioned over Canada but extending over Northern Alaska, is keeping the North Slope and Yukon Flats hot and dry. Between them, thunderstorms will develop. There are two main swaths of precipitation, one for each low. The first will arrive in the Western Alaska Range/Kuskokwim Valley Wednesday morning and rain through Wednesday evening. NBM 25th and 75th percentile create a range between 0.25-0.50" at the low end and 0.75 to 1.00" at the high end. Using McGrath as a sample point, many ensemble model members are forecasting between 0.5 and 0.75 inches with a few model runs at an inch or more. I expect a widespread area in the Kuskokwim Valley of between a quarter and three quarters of an inch of rain with some areas where it is heavier seeing up to an inch on Wednesday. The second band of precipitation is associated with the low over the panhandle. It comes in from the east over Fortymile Country a bit later on Wednesday afternoon and continues to wrap around west into the Tanana Valley and Alaska Range on Thursday. Rain totals range between a quarter of an inch to an inch for much of the Interior south of Circle in a 24 hour period. The eastern Alaska Range could see around 2 inches due to upslope flow. Apart from the two main bands of precipitation, showers and thunderstorms will develop in the afternoon. The best chance for scattered thunderstorms on Wednesday will be in the Western Interior, from the Middle Yukon Valley, near Galena, and north into the Western Brooks Range. Isolated thunderstorms will have a chance to develop over the higher terrain in the rest of the northern Interior as well. The Yukon Flats and Eastern North Slope will remain dry and hot again today with temperatures peaking near 85F in the Yukon Flats and near 80 north of the Brooks Range.

Thursday, as the Bristol Bay low moves east into the Gulf of Alaska, a ridge builds in from the Bering which will connect with the ridge over the Northeast. Weather will continue to be warm in the northern parts of the Interior, reaching the upper 70s and low 80s. Isolated thunderstorms will develop southeast of the new ridge axis, in the Central Interior. Widespread rain in the Southern Interior will dissipate through throughout the day as the low in the Gulf moves away, but it will mean cooler temperatures in the southern Interior on Thursday, likely below 70F.

Friday, thunderstorm coverage shifts eastward along with the low in the Gulf and ridge which is becoming more established over the State. Isolated thunderstorms will develop in the eastern Interior and eastern Brooks Range Friday afternoon. Temperatures will begin to increase for the majority of the Interior, back into the upper 70s/low 80s. Broad scale troughing over the West Coast and Western Interior will keep temperatures cooler, in the 60s.

FIRE WEATHER

As a low pressure system centered over Bristol Bay this morning tracks east towards the Gulf of Alaska, cooler temperatures and ample moisture will continue to advect north as gap winds ramp up through Alaska Range passes first followed by a broad increase in synoptic winds later today into Thursday regionwide. Following another active thunderstorm day across Western Alaska yesterday with over 3,000 lightning strikes, another unsettled day is on tap today with another round of scattered thunderstorms extending from the Lower/Middle Yukon north through the Brooks Range and onto the Southern Arctic Plains. Cooler temperatures and cloudier conditions building in farther south will work to limit convection, with onshore winds along the West Coast limiting thunderstorm development out that direction.

A Fire Weather Watch remains in effect for the Interior Kotzebue Sound and Northwest Interior north of Galena to Ambler, which will be coordinated with AICC later today on a potential upgrade to a Red Flag Warning. At this time, isolated to scattered coverage looks more likely farther inland up through the western North Slope region. While temperatures will see some relief over the southern half of our CWA, highs in the 70s to low 80s will continue for the Northern Interior north onto the Southern Arctic Plains. While the North Slope sees temperatures moderate later in the week, the warmest conditions across our region are expected to continue for the Yukon Flats.

As the aforementioned low tracks east into the Gulf on Thursday, a northeast oriented upper level ridge will quickly fill in behind. This setup will allow for northeasterly flow to develop across the Southern Interior Wednesday night into Thursday, supporting more scattered to widespread light rain showers. With this precipitation will be a large cloud shield, further limiting convection and pushing best chances north of the Tanana to around the Fortymile, North-Central Interior, and Brooks Range. By Friday, the ridge axis will shift to being directly overhead and will lead to warming and drying conditions across Northern Alaska, with any isolated thunderstorms over the Central/Eastern Interior and Brooks Range trending more isolated. Looking ahead, there is increasing confidence towards another upper level trough working east from Siberia Friday into the weekend, with more widespread precipitation chance and cooler temperatures expected regionwide as thunderstorm coverage becomes increasingly isolated.

EXTENDED FORECAST DAYS 4-7

Saturday through Tuesday. Generally, models are in agreement that there will be an upper-level low near the Bering Strait on Saturday morning, though the ECMWF has weak ridging over the SE portions of the state while the GFS has ridging over the NE. Both models have the ridging weakening throughout the day and the GFS has a weaker low being pushed into the Gulf of Alaska Saturday night while the ECMWF doesn't. However the ECMWF does have the low that was near the Bering Strait going into the Gulf on Monday morning while the GFS keeps it over the Bering Sea and eventually move of mainland Alaska. This differs from what earlier model runs were hinting at, so it is possible that this forecast may change once again.

Limited impacts are expected for either of these solutions, both producing scattered showers over the state throughout the period. Uncertainty remains regarding precipitation timing, location, and amount. Cooler, but relatively seasonal temperatures are still expected.

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.