textproduct: Fairbanks

SYNOPSIS

Primary threats through the next 24 hours are heavy rain, thunderstorms, and some gusty winds through Delta Junction Tuesday night/Wednesday morning. We still anticipate up to 2 inches of rainfall Thursday for portions of the Alaska Range, with an ESF (Hydro outlook) issued going over further details and impacts. As a shortwave lifts north across the interior this afternoon, gusty southerly winds will impact mountain passes into Wednesday morning, with the strongest likely in Delta Junction; however, gusts should largely remain below 45 mph. Cooler temperatures and higher relative humidity continue across the interior Wednesday limiting fire weather potential before a warming trend Thursday. Fire weather concerns could shift to the north and west; more info below.

KEY WEATHER MESSAGES

Central and Eastern Interior...

- Strong thunderstorms continue across the Central Interior as a front moves west across the Tanana Valley. These storms are capable of producing prolific lightning, heavy rain, small hail, and outflow wind gusts of 40 mph.

- Moderate to heavy rain continues to impact the Alaska Range, with precipitation continuing to shift west overnight into Wednesday.

- Southerly winds gusting to 40 to 50 mph continue through the first part of tonight for Isabel Pass and near 35 mph for Windy Pass.

West Coast and Western Interior...

- Temperatures remain seasonably cool along the West Coast, with high 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.

- Isolated thunderstorms will remain possible in the Lower Yukon and Middle Kuskokwim Valleys through the week. - As winds in the Bering become southerly, we will likely see low stratus clouds and fog creep back towards St. Lawrence Island, the Norton Sound and Bering Strait.

North Slope and Brooks Range..

- Temperatures along the North Slope and in the Northern Brooks Range valleys will see highs in the 60s or low 70s into Wednesday. Temperatures begin a cooling trend on Thursday. - Isolated thunderstorm chances increase in the Central and Eastern Brooks range on Wednesday as a cold front stalls over the area.

- A trough brings strong southwesterly winds into the Western Arctic Coast on Wednesday. Winds will turn from westerly to northerly on Thursday as the trough exits to the northeast.

FORECAST ANALYSIS AND DISCUSSION

A 553 decameter low in the Gulf will be associated with a front that will be traveling westward over the state, bringing lots of rainfall to the Interior today and into tomorrow. Upwards of 0.5 to 0.75 inches have already fallen for the southern Interior with an additional 1 to 1.5 inches are expected for the Alaska Range and Upper Kuskokwim Valley, totaling up to 2 or more inches in some locations. Even though rivers and streams are expected to rise, there are no flooding concerns at this time, though people doing recreational activities outside, especially near the Alaska Range, should remain weather aware. Additionally, southerly winds will be gusting as high as 40 to 45 mph through the Alaska Range as the front passes. Ahead of the front, thunderstorms will be possible from the Yukon Flats to the Central and Eastern Interior due to weak ridging being pushed towards the West Coast.

By Wednesday, the front begins to stall and weaken due to another low approaching from the Bering Sea. This almost north to south oriented front will continue to bring light showers to the Upper Kuskokwim Valley as well as cooling temperatures to the Interior. Ridging in the West Coast will allow dry conditions and afternoon thunderstorm to continue, especially from the Lower Yukon to the Central and Eastern Brooks Range.

On Thursday, the low in the Bering Sea is expected to continue to slowly approach the West Coast along with the low in the Gulf will inhibit the ridge from building into the area. As the low in the Gulf is on its way east, it will likely bring another round of precipitation for the southeast Interior. Isolated thunderstorm chances will remain likely for areas across the Interior and West Coast. An upper-level low will dip south towards the North Slope on Thursday into Friday, dropping their temperatures beginning Thursday evening and persist through the weekend.

FIRE WEATHER

Keeping things simple, through the end of the week fire weather concerns for warm and dry conditions are shifting into the northern Interior, more likely north and west of the Yukon River corridor and into the eastern Brooks Range. For the remainder of the Interior, fire weather conditions are moderating as a swath of abnormally high moisture is shunted into the region from a potent low in the Gulf of Alaska. Expecting cooler temperatures and higher relative humidity helping with suppression efforts, especially across the AK Range and Upper Tanana Valley over the next few days. Here we will likely see rain totals near 2 inches; the highest amounts across the central AK Range. One note is the potential for isolated to scattered thunderstorms to continue, with a primary focus along a frontal boundary from McGrath/Bettles and into the Yukon. Thunderstorms will persist longer Tuesday evening from the White Mountains southwest toward McGrath associated with a shortwave lifting across the Interior; expect thunderstorms to move from the northeast to the southwest. Anticipate periods of heavy rain, small hail, wind gusts to 40 mph, and as the AICC put it so eloquently, prolific lightning.

Moving into the weekend a broad trough will lift into western Alaska, foreshadowing some rain, cooler temperatures, and higher relative humidity impacting most of the central and western Interior.

HYDROLOGY

Through Tuesday and Wednesday an inverted shortwave will lift out of Canada into the Central Interior, serving as the catalyst for thunderstorms and heavy rainfall. Touching on rain, anomalously high PWAT of 1 to 1.2 inches (well above the 90 th percentile for PAFA this time of year) is associated with this system, with northwesterly flow hitting the Alaska Range, helping to drive efficient rainfall. Given these factors, anticipate 1 to 2 inches of rainfall from Tuesday into Wednesday. As this system stalls out in the Western Interior, another inch or so of rain will fall through Thursday, mainly impacting the Upper Kuskokwim into McGrath.

Largest impact will be rapid rise in smaller rivers and creeks in prominent mountain drainages; however, the antecedent warm/dry conditions means that these rivers are starting low and will likely not exceed major flood stages. Expect an increase of trees/debris in rivers as well.

No major flooding of mainstream rivers is anticipated at this time.

EXTENDED FORECAST DAYS 4-7

A weakening ridge over mainland Alaska will give way to a cooling trend and widespread rain showers by the weekend as a strong low pressure system pushes eastward from the Bering Sea. From Friday through Saturday, moist and unstable air flowing from the east- southeast will maintain a persistent threat of daily afternoon and evening thunderstorms across the Interior and Brooks Range. This lightning activity will sustain an elevated wildfire risk for the region. Meanwhile, unseasonable warmth under the leftover ridge will bring unusually hot conditions to northwest Alaska through Saturday, with temperatures climbing to the mid to upper 70s before cooler air and cloud cover arrives. As the weekend progresses, an incoming low- pressure system tracks into southwest Alaska, bringing thicker cloud cover and a threat for heavy rainfall to the Alaska Range and Central Interior from Saturday through Sunday. Widespread cooler temperatures in the 60s will expand from the Brooks Range southward into early next week, while a second storm system entering the Bering Sea introduces an additional threat of rain and strengthening winds across western Alaska by Monday and Tuesday.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...None. PK...Small Craft Advisory for PKZ857-858.