textproduct: Fairbanks

SYNOPSIS

While high pressure is building across Northern Alaska, thunderstorm activity will begin to ramp up across the Interior today. Scattered to Numerous thunderstorms will be possible in the Western Interior south of the Galena. Temperatures will continue to rise through Tuesday with temperatures in the 80s across most of the Interior Valleys and Arctic Plains. We have a heat advisory in effect for the Arctic Plains and the Yukon Flats. These areas have the best chance to see temperatures upwards of 85F. Along the coastline temperatures will be in the 50s/60s. Low pressure will make a return on Wednesday bringing cloud cover, rain showers, and lower temperatures.

KEY WEATHER MESSAGES

Central and Eastern Interior... - A warming and drying trend will occur across the Interior through Tuesday with daytime temperatures rising into the 70s and lower 80s. A heat advisory is in effect for the Yukon Flats for highs near 85 Tuesday and Wednesday. Temperatures cool late Wednesday into Thursday.

- Isolated thunderstorms will be possible today across much of the Central and Eastern Interior with the exception being the Yukon Flats. Along the Alaska Range we could see scattered thunderstorms this afternoon. Most of these storms should be on be the northern slopes of the Range.

- Tuesday night and into Wednesday we will see a brief period of gaps winds develop in Isabel pass. These winds could gust up to 40 mph.

West Coast and Western Interior... - Temperatures will continue to rise across the region with daytime highs of 70s and low 80s in the Western Interior valleys. Along the coast highs will be in the 50s/60s. Temperatures will begin to cool across the region on Wednesday.

- Scattered to Numerous thunderstorms are expected today across the southern half of the Western Interior. The Kuskokwim mountains will see the brunt of the storms, but as those storms move southwest they could potentially move into the valleys. The thunderstorm threat will shift northward tomorrow across the whole Western Interior.

North Slope and Brooks Range.. - Warm temperatures expected. Daytime temperatures warm into the 50s near Utqiagvik to near 80 on the Arctic Plains. A heat advisory is in effect for the Arctic Plains Monday and Tuesday.

- Isolated thunderstorms will be possible in the Brooks Range and Central Arctic Plains today. These chances will continue on Tuesday, but will extend in coverage to the coastline.

FORECAST ANALYSIS AND DISCUSSION

A 570 decameter high pressure is continuing to move east across the North Slope. To our south in the Gulf a closed off 544 decameter low will continue to eject vorticity maximas into the Southern Interior. By midday today there is enough energy to attempt to organize this energy into a positively tilted trough. Accompanying this trough is a very weak 300 mb jetstreak that is going through the Central Interior. The 500 mb trough as well as being in the left exit region of the jetstreak will create an area of upper-level divergence in the southern portion of the Western Interior. At the surface with rising temperatures we are seeing a weak thermal trough develop. This trough will create an area of convergence which will help to accelerate vertical motion at the surface. CAPE values at McGrath are anticipated to be around 1200 J/kg and LI values of -4 to -6. These thermodynamics paired with upslope from the Kuskokwim and the thermal trough, should see rapid upward vertical motion in the southern half of the Western Interior. PWAT values are around an inch and slow storm motion will allow for any thunderstorm to produce heavy rainfall. DCAPE values steadily increase through the afternoon, so any thunderstorm that continues past 6PM could see wind gusts up to 45 mph from the outflow boundaries. Before 6PM storms could produce outflow boundaries with winds of 30 mph.

Tuesday another low pressure will be moving towards Bristol Bay which will eject a trough into the Western Interior during peak heating. This trough will interact with the top of the ridge axis that is steadily being pushed eastward into Canada. This trough will bring similar dynamics to Mondays thunderstorms to the region on Tuesday. This trough will help to extend the scattered thunderstorm threat northwards to include all of the Western Interior and potions of the Western Brooks Range.

As the low itself rotates southeast into the Gulf of Alaska we will see cooling temperatures across the Southern Interior as a cloud shield, widespread rain showers, and a weak cold front settles into the region. This will practically cut off the thunderstorm concerns for anywhere south of the front, but areas north of the front will continue to see thunderstorm development. With the low in the Gulf blocking the North Pacific Ridge from extending a ridge axis into Northern Alaska, we are expecting to move back into a troughing pattern. This change of pattern will be talked about in more detail in the Extended Forecast Discussion.

FIRE WEATHER

With a ridge of high pressure overhead and a series of low pressure systems in the Gulf of Alaska and Bering Sea, daily isolated to scattered showers and thunderstorms will continue across Northern Alaska early this week with a focus on the Interior. Following over 3,000 lightning strikes on Sunday (as of 9:30 PM Sunday), we are looking at several more active thunderstorm days across our region which will be capable of producing new fire starts. The best scattered coverage on Monday will exist from Southwest Alaska north up through the Western Interior to the Western Brooks Range, broadly expanding to include the Eastern Seward Peninsula and more of Yukon Delta, Brooks Range, and Arctic Plains on Tuesday. Scattered to at times numerous thunderstorms are expected in these corridors, with critical fire weather conditions possible due to the broad areal coverage of thunderstorms anticipated. Stronger thunderstorms will peak each afternoon and evening and will be capable of producing heavy rain, wind gusts up to 30 mph, small hail, and frequent lightning capable of starting new fires.

Highs across much of Northern Alaska will continue to be in the 70s to low 80s through Tuesday with locally cooler conditions along the coasts. Afternoon RHs will continue to drop to that 25-40% range overall, with the Yukon Flats seeing locally drier conditions around 20-30%. Increasing confidence supports that low pressure system in the Bering Sea tracking east late Tuesday into Wednesday towards the Gulf of Alaska, helping to moderate temperatures and RH while shifting best thunderstorm chances to the Northern Interior, Brooks Range, and Arctic Plains Wednesday through Friday. Synoptic winds will remain generally light outside of any thunderstorms, with the exception to this being the Upper Tanana Valley from Delta to Northway with gusts to around 15-25 mph possible during the afternoon hours through Tuesday. Stronger winds are also expected to build in through Alaska Range Passes on Wednesday, as winds broadly see an increase across much of our region on Thursday.

EXTENDED FORECAST DAYS 4-7

The upper-level low in the Gulf continues to move slowly to the east on Thursday while another upper-level low begins to approach from Siberia. A triple point low will be moving into the Bering Sea from Easter Russia on Friday. This low will bring a cold front swinging across the Western Interior. Ridging over the eastern portion of the state will continue to persist. Depending on the strength of the ridge axis will determine how far inland precipitation will be able make it. The ECMWF has a much stronger ridge, which will limit the amount of precipitation in the Western Interior, unlike the GFS solution which keeps it much weaker. By Sunday morning, the ECMWF has a trough stretching from Siberia to Southcentral Alaska and the GFS has the trough extending all the way to the Gulf of Alaska and to the panhandle. Overall, the models are in agreement regarding the features, but the strength and timing of the features remains uncertain.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...Heat Advisory for AKZ833. Heat Advisory for AKZ806-808. PK...None.