textproduct: Fairbanks

SYNOPSIS

High pressure will begin to build across Northern Alaska this morning bringing us back to our regular scheduled summertime program. Temperatures across the region will rise Sunday and Monday before reaching 10 to 15 degrees above normal Tuesday. Ample moisture remaining in the Interior will allow daily afternoon chances for showers and thunderstorms to continue. With warming temperatures, the Interior valleys will dry out, leading to the potential of enhanced fire risk Monday and Tuesday.

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. Tuesday is expected to be the warmest day of the week.

- Isolated to Scattered thunderstorms will be possible in the White Mountains and Fortymile Country. These storms will develop and then move southwest into the valleys. Longer lived storms could produce heavy rainfall up to 3/4", frequent lightning, and pea size hail. West Coast and Western Interior... - Patchy fog in the Y-K Delta will continue this morning, and should begin to mix out and lift by 10 AM.

- A warming and drying trend will occur across the region through Tuesday with daytime temperatures rising into the 60s/70s. Tuesday is expected to be the warmest day of the week.

- Isolated thunderstorms will be possible across the southern half of the Western Interior today. Monday those chances increase across most of the Western Interior.

North Slope and Brooks Range.. - High pressure develops over Northern Alaska with a gradual warming and drying trend into Tuesday. Daytime temperatures will warm into the 50s near Utqiagvik to the 70s on the Arctic Plains.

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

FORECAST ANALYSIS AND DISCUSSION

A 544 decameter low in the Gulf of Alaska will be accompanied with a 570 decameter high moving east onto the Arctic Coast. This will create an area of upper level divergence in the Interior which will help to support showers and thunderstorms today. A trailing arctic trough will be the major factor in todays weather. This trough will not only move through the Central and Eastern Interior at peak heating, it will help to increase the intensity of divergence aloft. This will help to accelerate air upwards, once a parcel can reach 500 mbs. As the trough moves southeast we will see storms pop up in the higher terrain from air that is accelerated in orographic lift. Then once storms get going we will see a storm motion of northeast to southwest. So these storms have the potential to move into the valleys. Models soundings are very similar to yesterdays. This could lead to any of the stronger storms being able to produce heavy rain up to 3/4 of an inch, as well as pea size hail.

With the building high pressure, 850 mb temperatures will continue to rise. These temperatures will be 10C to 15C across Northern Alaska. This will help to support the 70s/80s across much of the Interior and North Slope. The coastlines will also be able to warm into the 50s/60s. By Tuesday we could see Interior valleys approach 85F. These however could be limited from cloud cover. An approaching Bering Sea low as well as the remnants of the low in the Gulf of Alaska, will bring in additional moisture and vorticity maximas. This will help to produce showers and thunderstorms, and widespread cloud cover. We could see a brief window on Tuesday to reach 85F depending on the extent of the cloud cover. This approaching low could bring a couple days of enhanced thunderstorms activity, as well as the potential to see another pattern shift by the weekend. This will be discussed more in detail in the Extended Forecast Discussion section.

FIRE WEATHER

An upper level ridge has started to build over Northern Alaska and is expected to support warmer temperatures, drier conditions, and higher chances for isolated and even scattered thunderstorms. Some models are depicting the center of the associated high pressure system to move directly over the North Slope. A Heat Advisory has been issued to be in effect for the Central and Western Arctic Plains for Monday morning through Monday night. High temperatures in this region are expected to reach the mid 80s through mid week. A gradual warming trend can be expected for much of Northern Alaska, as the Interior and portions of the West Coast are likely to climb into the upper 70s and even low 80s by Tuesday. Gradual drying will accompany the gradual warming, as minimum RHs are expected to drop into the 30s to 40s percent range Sunday and dry into the low 20s percent over the Central Arctic Plains, Yukon Flats, and the general Allakaket area on Monday and Tuesday. Min RHs are expected to begin recovering by Wednesday.

Isolated thunderstorms are expected for the Central and Eastern Interior as well as the Middle Yukon, Western Interior, and Norton Sound Coast by Sunday afternoon into the evening. By Monday afternoon, chances for storms become scattered over the Western Interior and Middle Yukon including McGrath, Nikolai, and Galena. Isolated chances are still expected for the Central and Eastern Interior with chances expanding to the north to include the majority of the Arctic Plains. By Tuesday afternoon, the area of scattered storms expands north through Ambler and the South Slopes of the Central Brooks Range. Isolated chances continue to include the Central and Eastern Interior with an expansion into the YK Delta. Scattered showers are expected to accompany storms. Winds are expected to stay light for most of Northern Alaska, but could become gusty and erratic near thunderstorms as outflow boundaries form. Starting Monday morning, models are showing northeast winds to pick up over the Upper Tanana Valley just southeast of Delta Junction. Gusts could reach 40 mph at times and increase fire weather concern in the area. The upcoming week, with high chances for thunderstorms, high temperatures, and upper level ridging, is very likely to support new fire starts as far north as the Arctic Plains.

EXTENDED FORECAST DAYS 4-7

Ridging will be shifting over Canada on Tuesday opening the door to a very active thunderstorm pattern over Northern Alaska. This will be aided by a low in the Gulf and Bering. The low in the Gulf would bring moist southeasterly flow to the Central/Eastern Interior while the low in the Bering would bring moist southerly flow to the West Coast and Western Interior. As this runs into the hot/dry Northern Alaska air, it becomes very unstable. Moving further into the week, the pattern becomes very messy with an arctic trough over northern Siberia moving towards NW Alaska, a ridge over the NW Territories and east/southeast flow over much of Northern Alaska with numerous shortwaves meandering throughout the flow. This could bring chances for very heavy rain, thunderstorms as well as hot temperatures in places where it doesn't rain. Oddly enough, the hottest temperatures by the middle of next week may end up being on the North Slope and in the Brooks Range depending on how much rain the Interior receives. Afterwards, we'll be monitoring the ridge and where it moves because there is a chance it keeps a presence over Alaska or in Canada which can prolong warm weather and chances for thunderstorms. There is an almost equal chance that troughing moves in late next week/weekend and brings cooler and wetter weather to Northern Alaska.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

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