textproduct: Fairbanks

SYNOPSIS

Warmer temperatures with chances for showers and thunderstorms will be possible across the Interior for the latter half of this week, with otherwise fairly light winds expected. Highs could rise from the upper 60s and 70s today into the low 70s to low 80s by late this week. The southern Arctic plains could see highs in the 60s and 70s, with the Arctic coast in the 40s and 50s during this time frame. Some additional rain will be possible in the Central Brooks Range from later this morning through tomorrow morning and could total up to a couple tenths of an inch. Thunderstorm chances will increase from Friday into the weekend in the Interior and on the North Slope.

KEY WEATHER MESSAGES

Central and Eastern Interior... - Temperatures will be a few degrees above normal today with a warming trend bringing highs into the upper 70s to near 80 by Friday. - Thunderstorms increase in coverage today and tomorrow, with the greatest potential from Friday into the weekend.

West Coast and Western Interior... - A warming trend begins today with highs in the 60s to near 70 in the Interior and 50s along the coast. Gradual warming by about 1 to 2 degrees a day continues through the week.

- Thunderstorm chances increase today and will be isolated over most of the Interior and northern Seward Peninsula. Isolated thunderstorms persist on Thursday in the Interior then track east on Friday.

- A low moves to the West Coast tonight and will provide an enhanced area of showers through Thursday, especially south of the Seward Peninsula.

North Slope and Brooks Range... - Other than some showers, the heaviest rain has ended. A Flood Advisory is in effect for the Colville River through Friday morning with Flood Watches elsewhere through at least this morning.

- Warming trend with temps ranging from the upper 40s/low 50s along the coast to the low to mid 70s in the Brooks Range valleys by Thursday.

- The warmer temps will also support chances for thunderstorms in the Brooks Range and North Slope from today through Saturday.

FORECAST ANALYSIS AND DISCUSSION

To start the period, ridging aloft dominates the Central/Eastern Aleutians and Bering Sea, with troughing across the Chukchi Sea and Northwest Arctic. Additional ridging is in place in northwestern Canada. Aside from some areas of fog and low stratus on the Arctic and West Coast, areas of clouds and isolated showers linger across the area this morning; more substantive rain will develop across the Central Brooks Range later this morning and afternoon and last through the night before diminishing. Elsewhere, periods of showers will be possible during the daytime with warm afternoons and evenings.

Temperatures at the 850 mb level will rise into the high single digits and low double digits Celsius in the Interior as ridging builds aloft from the east later this week, with highs gradually rising from the mid 70s into the 80s. Somewhat cooler temperatures in the low to mid 60s in near-coastal portions of Western Alaska (with 50s rights on the water) are likely for highs as the upper low drops southward. Highs on the North Slope are expected to be in the 60s and 70s in the Arctic plains, with 40s and 50s on the coast. Moving into later this week, while the ridge will remain generally focused near the eastern border, a few hundred J/kg of surface-based CAPE with LI values in the 1 to 3 range will be possible across much of the Interior and North SLope. This will combine with a few shortwave troughs and general diurnal heating to yield thunderstorms each day, especially from Friday onward when scattered thunderstorms will be possible.

FIRE WEATHER

Upper level ridging continues to build over the state today, with the pattern finally starting to resemble a typical summer-like set up. High temperatures will rise into the mid to upper 70s across the Central/Eastern Interior this week, with a few spots reaching as high as 80F to 85F possible. Temperatures across Western Alaska will follow a similar warming trend into the low to mid 70s in the Western Interior and 60s along the coast. The southern slopes of the Brooks Range may see temperatures exceed 75F as well by the weekend. Min RHs will mostly stay above 30% through the week with the exception of the Yukon Flats and Tanana Valley where min RH values may reach as low as 25% at times. Winds will remain fairly light and out of the west/southwest through the week, with gusty winds possible in the afternoons due to solar mixing. Isolated thunderstorms are possible for the Western Interior, Alaska Range, and Brooks Range through Thursday, with coverage expanding into the Central/Eastern Interior, Yukon Flats, and Fortymile Country by Friday. Wetting rains are expected with these storms and may produce heavy rainfall, small hail, gusty winds, and frequent lightning at times, especially this weekend. Due to moderate precipitation chances and light winds, critical fire weather conditions are not expected.

EXTENDED FORECAST DAYS 4-7

The extended period begins with upper level troughing along the West Coast and ridging over Canada's Yukon Territories. The west coast trough is composed of a closed low that tracks south across the Alaska Peninsula on Sunday and an arctic low pressure that pivots across the North Slope on Sunday too. A frontal boundary separates a warm summer-like air mass across the east and a cool maritime airmass over the west. This boundary focuses thunderstorm activity over the weekend and into next week, but confidence in how the frontal boundary moves across the interior remains low. Otherwise, warm temperatures with highs approaching 80F continue this weekend with a slight cooling trend back down to around 70F early next week. Lower relative humidity accompanies the warmer temperatures with locations that miss out on thunderstorms drying out quite a bit over the next week.

Coastal Hazard Potential Days 3 and 4...None

HYDROLOGY

Most of the rain is ending on the North Slope and Brooks Range but there are plenty of flood products issued including an Advisory along the Colville and Sag and a Warning in Wiseman/Coldfoot. Watches are issued for most of the North Slope, Brooks Range and the Koyukuk River to Allakaket.

See weather.gov/afg for the most updated flooding products and water.noaa.gov for the most updated river gauge forecasts.

Otherwise, we anticipate high water and river rises as the snowmelt continues and rain ends. Impacts may persist through the end of the week, especially on the North Slope as it takes a while for all of the water to pass through the system. The latest forecast for the Sag River along the Dalton Highway is, between mileposts 310-340, road washouts are possible especially in areas adjacent to the Sag River and in the vicinity of stream crossings if lingering ice results in culvert blockages. On the Colville from Umiat to Nuiqsut, minor flooding in low-lying areas due to rapid temperature rises and continuing rain on residual snowpack is possible. The flood crest should attenuate as it progresses downstream, but water levels are already high in Umiat and minor flooding should be expected elsewhere.

High water near Coldfoot and Wiseman will continue to recede today but it is flowing towards Bettles and Allakaket currently. The river gauge in Bettles is beginning to rise and will continue to do so through about midnight Wednesday night with a current forecasted crest around 22.70 feet. Allakaket will see their highest water about 24 hours later. Minor flooding will be possible as the water continues to rise.

AFG WATCHES/WARNINGS/ADVISORIES

AK...Flood Watch for AKZ804>810. PK...None.