textproduct: Fairbanks

SYNOPSIS

A more active pattern is looking to settle in as the beginning of the week progresses. Attention turns to a cold front that will be moving west from the SE portion of the Interior. Areas west of the front will see the best chances for thunderstorms over the next couple of days as it continues to shift west. In addition, the easterly flow will be tapping into a decent source of moisture that will be distributed across the southern portions of the Interior through Wednesday morning. Widespread 0.5" to 1" of rain is expected with higher amount possible along the western portions of the Alaska Range. High pressure will continue to linger over the Western portion of the state which will allow for conditions to be hot and dry through the end of the week.

KEY WEATHER MESSAGES

Central and Eastern Interior... - Warm temperatures continue through Tuesday ahead of a cold front, with widespread highs in the mid 70s to low 80s. The warmest temperatures will be across the Yukon Flats with values in the mid 80s expected.

- Scattered afternoon thunderstorms are expected across the Southern and Eastern Interior through Tuesday afternoon. Thunderstorm chances will lessen behind the front as it continues to move westward

- The front tracking from east to west brings high rain chances from the White Mountains southward late tonight through Tuesday night with locally heavy rain and gusty winds possible, especially near the Alaska Range. Heaviest precipitation expected along the western portion of the Alaska Range.

- As the front passes through on Tuesday evening, southerly winds across the Alaska Range will briefly swell, with gusts up to 45 mph through Isabel Pass and up to around 35 mph through Windy Pass.

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 through the latter half of the week.

- Scattered thunderstorms are expected in the Upper Kuskokwim Valley today, with isolated thunderstorms in the Middle and Lower Yukon Valley.

- The frontal boundary is expected to stall around the Central Interior, allowing isolated thunderstorm chances to continue across the Western Interior through the end of the week.

North Slope and Brooks Range... - A frontal boundary brings rain chances to the central Arctic Coast and widespread clouds, before clearing by Tuesday morning.

- Temperatures along the North Slope and in the Northern Brooks Range valleys will see highs in the 60s or low 70s today through Wednesday. Temperatures begin a cooling trend on Thursday. - There is a slight chance for isolated thunderstorms over the Eastern Brooks Range today and Tuesday. Thunderstorm chances increase for the same area on Wednesday with the stalling cold front.

FORECAST ANALYSIS AND DISCUSSION

Satellite imagery this morning shows much of the northern half of the state clear and calm. This is mostly due to a building E-W oriented ridge across the central portion of the state. The south side of the trough axis shows a swath of convective clouds slowly starting to build ahead of scattered shortwaves that are expected to move easterly across the southern half of the state, today. The main driver of this easterly flow is from a prominent low that has set up south of Kodiak Islands. This low has been able to hold its strength due to some entrainment of energy from a previous low in the Bering, who's energy will be moving across the Interior over the next couple of days. This shortwave will wrap around the main low and begin to move over the SE portion of the Interior late tonight into early Tuesday morning. The shortwave will continue to progress along the Interior throughout the day while the main low remains in place just south of Kodiak Island. This will result in an inverted shortwave moving across the Interior on Tuesday, which could result in some stronger, longer lived storms on the west side of the front. Latest model soundings around FNSB show CAPE potential to be 800-1000 J/kg and sfc-6km shear around 25 knots.

In addition to the stronger thunderstorm potential, this low in the gulf will be tapping into an anonymously wet atmospheric river from the North Pacific. This will bring good chances for wetting rains across the southern portions of the Interior with the heaviest amounts expected along the Western Alaska Range on Tuesday. Total rainfall is expected to be between 0.5" to 1.0" with locally higher amounts around 2" possible through the Alaska Range. As the front continues to moves east, an upper-level ridge will remain in place over the western portion of the state. This will cause the front to become more N-S oriented and stall around the Central Interior, which will allow for warmer and drier conditions to continue along the Western Interior through the later half of the week. In addition, majority of the Interior will have a chance to see a brief break in thunderstorm chances on Wednesday, depending on where the front stalls out. Areas on the west side of this boundary will continue to see chances for thunderstorms on Wednesday. Latest guidance shows the current potential to be along a line from Arctic Village to McGrath, westward toward the YK Delta.

Meanwhile, the low in the gulf will eventually begin to shift farther east toward the Alaska Panhandle. This will continue to allow easterly flow and daily thunderstorm chances across the Interior through the end of the week. In addition, another low will be working its way east along the Aleutians and eventually stall in the Bering with the ridge built up over the western portion of the state. This will set up a subtle blocking pattern by the end of the forecast period.

FIRE WEATHER

Following yesterday's active thunderstorms, we have already begun to see lightning in the SE Interior and Fortymile Country. We are expecting thunderstorms to continue throughout the southern and eastern Interior, prompting Red Flag Warnings to be issued for these areas. Winds are expected to be generally light except around thunderstorms where they may become gusty and erratic. Widespread high temperatures in the 70s and lower 80s are expected through Tuesday with the potential of a slightly cooler day on Wednesday with upper 60s and 70s expected for the Interior. The driest areas are expected in the Yukon Flats with min RHs as low as 20%. Elsewhere should see min RHs as low as the upper 20 to 30% range.

By Tuesday morning, rain showers and embedded thunderstorms associated with a front are expected to begin for the Eastern Interior and Alaska Range and spread west by Tuesday afternoon. This front is expected to bring steadier precipitation throughout the day for the Interior on Tuesday, especially for the Alaska Range. Rainfall totals are expected to range up to 1" with locally higher amounts for the western Alaska Range as high as 2". As the front passes, this cloud cover, precipitation, and thunderstorms will limit high temperatures and raise RHs for the area. This front is expected to stall over the Interior from Arctic Village to McGrath west towards the YK Delta, allowing for additional rainfall and thunderstorms Wednesday and Thursday afternoon before weakening, but the heaviest rainfall is expected on Tuesday. Once the front weakens, weak ridging will build back into the state, allowing for high temperatures to reach back into the upper 70s and low 80s with chances of isolated thunderstorms returning to the Interior.

HYDROLOGY

A front will move westward through the state this week. As this front progresses, it will produce widespread rain showers and isolated thunderstorms. Showers and thunderstorms are expected to begin Tuesday morning in the eastern Alaska Range and upper Tanana Valley and spread northwest through Tuesday night. The heaviest rainfall is expected to fall throughout the day Tuesday. 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 around the Alaska Range for the middle to end of this week. Rapid rises of smaller rivers are possible with the heaviest rain on Tuesday into Wednesday.

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.

Flooding remains unlikely for mainstream rivers in the affected areas.

EXTENDED FORECAST DAYS 4-7

On Thursday June 25th there will be ridging over the West Coast as well as North East Alaska, with a closed low over the Gulf of Alaska and troughing over the Western North Slope. As Sunday approaches the closed low will move eastward towards Alaskas coastline bringing a series of shortwaves embedded within southeasterly flow and increasing chances of showers and thunderstorms throughout the South and Central Region of our state. The primary feature focusing showers and thunderstorm chances will be a frontal system that is oriented roughly between McGrath and Bettles across Interior Alaska this upcoming Thursday to Friday. Continued warmth, and dry weather is expected west of the front, with temperatures ranging in the low to mid 70s. East of the front more cloudy and mild temperatures are expected as rounds of precipitation brought on by a series of shortwaves results in a cooler atmosphere. Northerly winds strengthen west of the front on Friday and Saturday with the strongest winds reaching about 35 mph between Cape Lisburne and the Bering Strait. Heavier precipitation is possible as the next closed low moves east from the Bering Sea to South Central Alaska towards the end of this weekend or early next week. Farther north across the North Slope temperatures start warm around 60 degrees Thursday to Friday and likely to cool as the frontal passes through by Saturday night.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...Red Flag Warning for AKZ935>945-947-951>953. PK...None.