textproduct: Fairbanks

SYNOPSIS

A rinse and repeat pattern continues through Monday ahead of an unseasonably wet frontal system pivoting into the southeastern interior on Tuesday. Thunderstorm chances across the southern interior are the forecast challenge for Sunday and Monday, but they are expected in the same general area as the past two days. A frontal boundary pivoting from southeast to northwest focuses thunderstorm chances on Tuesday and shifts them over the Western Interior by Wednesday. Locally heavy rainfall is possible with storms on Tuesday and rising river levels are possible.

KEY WEATHER MESSAGES

Central and Eastern Interior...

- Warm temperatures continue through Tuesday, with widespread highs in the mid 70s to low 80s. The warmest temperatures continue to be across the Yukon Flats where temperatures around 80F continue today and Monday with warmer temps up to 85F on Tuesday.

- Scattered afternoon and evening thunderstorms are expected across the Southern Interior Sunday through Tuesday with isolated thunderstorms possible over the eastern Brooks Range this evening.

- A front tracking from east to west brings high rain chances from the White Mountains southward late Monday night through Tuesday night with locally heavy rain possible, especially near the Alaska Range.

West Coast and Western Interior...

- Temperatures remain seasonably cool along the West Coast, with temperatures in the 50s to 60s. In the Western Interior, highs in the mid to upper 70s are expected to continue.

- Scattered thunderstorms are expected in the Upper Kuskokwim and Lower Yukon Valleys Sunday afternoon and evening, with isolated thunderstorms in the Middle Yukon Valley. Storm chances become more isolated on Monday and continue through Wednesday afternoon.

North Slope and Brooks Range...

- Cooler conditions are expected today in the wake of yesterday's cold front with a warming trend starting on Tuesday.

- A frontal boundary brings rain chances to the central Arctic Coast and widespread clouds Monday morning before clearing by Tuesday morning.

- Northern Brooks Range valleys will see much cooler highs in the 50s or low 60s today, with temperatures quickly recovering into the upper 60s or low 70s by Tuesday. - Isolated thunderstorms will be possible over the Eastern Brooks Range today with a lull Monday and Tuesday before storm chances return on Wednesday.

FORECAST ANALYSIS AND DISCUSSION

Upper ridging dominates the pattern across Interior Alaska between Arctic troughing over the North Slope and a closed low centered near Kodiak Island. The Arctic trough is sending a cool front southeast across the interior that will limit the northwest extent of thunderstorm chances while also focusing afternoon thunderstorm development along its leading edge. A drier post-frontal air mass is also resulting in deeper mixing and near Red Flag Warning criteria conditions across the northern interior under crystal clear skies. The pre-frontal airmass has temperatures warming through the 70s and dew points in the 50s early this afternoon, which is already initiating thunderstorms across high elevation portions of the interior. This thunderstorm activity is expected to peak this afternoon then gradually diminish this evening.

By Monday morning the frontal boundary will have settled across the southern interior. However, the sensible weather affects will be very similar to Sunday with another day of scattered afternoon showers and thunderstorms across the southern interior. Upper level ridging begins to shift northward on Tuesday as a potent easterly wave tracks around the Gulf of Alaska low and over the southeast interior. As a result, warmer temperatures shift back across the northern/western interior and North Slope for the middle of the week. The more impactful weather associated with this frontal passage is the potential for heavy rainfall across the southern interior, mainly on Tuesday. More information is contained in the hydrology section below, but precipitable water values exceeding 1" and EFI/SoT values support unseasonably heavy rainfall mainly across the Alaska Range.

FIRE WEATHER

We have already begun to see lightning developing along a cold front from near Arctic Village southwest to near McGrath and ahead of the front over the Fortymile Country. We are expecting thunderstorms to continue throughout the Interior, Western Interior, and eastern Brooks Range through this evening. Scattered thunderstorms bringing frequent lightning prompted issuance of Red Flag Warnings Sunday and Monday afternoon/evenings. Winds are expected to be generally light except around thunderstorms where erratic gusts up to 40 mph are possible. Widespread high temperatures in the 70s and 80s are expected through Tuesday with cooler temperatures and higher RH on Wednesday east of the frontal boundary. The Yukon Flats and Western Interior are expected to stay dry with high temps around 80F and RH values as low as 25%.

By Tuesday morning, rain showers and embedded thunderstorms associated with a frontal system are expected to begin across the southeast interior and spread west across the southern interior. This frontal system is expected to bring a swath of wetting rains across the southern interior. As the front passes, cloud cover, and rainfall limits high temperatures and raises RH values. This front is expected to stall roughly between McGrath and Bettles for Wednesday into Thursday. This front brings potential for locally heavy rainfall amounts >1", especially across the north-facing slopes of the Alaska Range and the foothills.

HYDROLOGY

As we progress into the week, a front will be moving westward over the state. As this front progresses, we are expecting widespread rain showers and thunderstorms. Rain showers and thunderstorms are expected to begin Tuesday morning for the eastern Alaska Range and spread west through Tuesday night when the time of heaviest rainfall is forecast. Widespread rainfall totals of 0.5" to 1" and locally higher amounts >2" possible will combine with glacial runoff to result in rising mainstream river levels for the middle to end of this week. Rapid rises of smaller rivers are possible with the heaviest rain on Tuesday into Wednesday near the Alaska Range.

By Wednesday, this front will be set up over the Western Interior and become relatively stationary, allowing for more precipitation to fall through Thursday afternoon. Upwards of 1" or more is expected in the Upper Kuskokwim area near McGrath and Lake Minchumina for this event.

EXTENDED FORECAST DAYS 4-7

A upper level low situated in the eastern Gulf of Alaska will bring a series of shortwaves that move easterly across the state on Thursday and Friday. These shortwaves will bring convective preciptiation to the Central and Eastern Interior, with daily chances for thunderstorms along higher terrain in the Central Interior. Clouds and precipitation associated with these shortwaves will not reach far into the Northern Interior, keeping warm temperatures in the region. On Friday, a new upper level low moves into the Bering north of the Aleutians. Though there isn't consensus on the strength and extent of this low, there is agreement that it will bring troughing to at least the western portion of the state.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...Red Flag Warning for AKZ929-930-934>947-951>953. Red Flag Warning for AKZ935>945-947-951>953. Heat Advisory for AKZ833. PK...Small Craft Advisory for PKZ812. Brisk Wind Advisory for PKZ813. Brisk Wind Advisory for PKZ859.