textproduct: Fairbanks

SYNOPSIS

Warm and dry continues across the central region Friday as a ridge builds aloft, driving temperatures into the upper 70s to mid 80s; warmest temperatures are expected across the Yukon Flats. Isolated thunderstorms will impact much of the Interior, with scattered thunderstorms for the Tanana Valley into southwestern interior, especially Saturday. The simple message is expecting hot and dry weather, and thunderstorms, to impact your weekend in the central region. For folks along the northwest coast, much cooler temperatures are expected as an Arctic front moves into the area Friday night into Saturday evening, bringing some rain and potential light snow to the western North Slope. Mariners navigating the coast Friday afternoon near Pt. Hope/Pt. Lay should be aware of southwesterly strong breezes to near- gale force conditions, think 25 to 30 knot sustained winds, with gusts to 40 knots. These southwesterly winds will quickly become northerly through Saturday morning.

KEY WEATHER MESSAGES

Central and Eastern Interior...

- Highs continue to increase across the area over the weekend with widespread upper 70s, to upper 80s. The warmest temperatures continue to be across the Yukon Flats with a Heat Advisory issued.

- Scattered thunderstorms are forecasted to impact much of the Tanana Valley, with an expansion likely to the western AK range including McGrath. Further north we will see isolated thunderstorm activity, with an uptick in the Yukon Flats Sunday.

West Coast and Western Interior...

- Temperatures remain seasonably cool along the western coast, with temperatures in the 50s to 60s. As you move further east into the Interior, anticipate much warmer temperatures, likely into the upper 70s by Saturday.

- Isolated thunderstorms are likely to continue across the western portion of the state.

North Slope and Brooks Range..

- An Arctic Front will slide south tonight starting in the North Slope, moving south into the western region by Saturday afternoon, helping to bring northwesterly winds to the west.

- Expect northern Brooks Range valleys to warm into the 70s and near 80 through Saturday, then drop on Sunday.

- Isolated thunderstorms will be possible each day through Saturday in the Plains and Brooks Range and will be more predominant in the southern Brooks Range on Sunday and into next week.

FORECAST ANALYSIS AND DISCUSSION

As of 230pm AKDT Friday afternoon thunderstorms continue to fire off higher terrain around the region, with the main conglomerate of strikes moving west across the Alcan border. These storms will continue to drift west across Fortymile following the Tanana River Valley, likely bringing an exciting evening to the Fairbanks area. Other portions of the central and northern regions are also seeing isolated thunderstorms. Scattered thunderstorms will increase in coverage and intensity Saturday, with a westward expansion into the lower Tanana Valley and western AK range. The primary threat with these storms remains in lightning and gusty outflow winds likely reaching near 40 mph.

Surface high temperatures will continue to rise into the upper 70s to mid 80s across much of the area with light winds and mostly clear and sunny conditions. The Western Interior and southern North Slope will be somewhat cooler but still in the low to mid 70s. Most of Northern Alaska will correspondingly be around 5 to 10 F above normal, but a cold Arctic trough/front northwest of Alaska will move in by late tonight. As it moves across the North Slope, it will bring with it a narrow band of precipitation, brisk southwest winds, and drop highs on the Arctic into the 30s and 40s, with the more inland areas falling into the 50s by Sunday. These effects will remain limited to the north side of the Brooks Range, with the trough/front exiting the area by early next week. South of the Brooks Range, save coastal areas which will remain in the 50s and 60s, most of the lower elevations will remain in the 70s and 80s for highs during this time frame, with lows in the 50s. Fort Yukon and the Yukon Flats could see highs in the upper 80s on Friday, with 850 mb temperatures around 14C.

FIRE WEATHER

Primary threats over the next 48 hours are:

- Increased thunderstorm activity across the central and eastern interior.

- Some of the warmest temperatures we have seen this summer.

- A dry arctic cold front impact areas north and west of Tanana.

Touching on thunderstorms first, expect scattered thunderstorms across much of the Tanana Valley Friday, with an expansion west toward McGrath/Western AK Range, especially on Saturday. These storms will favor formation over terrain and will be slow moving, offering ample opportunity for wetting rain underneath the parent storm. However, outflow winds from these storms could bring gusts to 35-45mph, helping flame up any holdovers or new starts from a plethora of lightning; this will be the heaviest lightning weekend so far this fire season.

Regarding warm/dry, the hottest temperatures of mid to upper 80s will favor the Yukon Flats, with RH in critical values of 20 to 25 percent. As you move west and south from the Yukon Flats temperatures will still reach into the upper 70s/low 80s, with RH likely down into the 25 to 30 percent range in favored areas. One positive note is that sustained winds should be light, below 15 mph, outside of any outflow from thunderstorms. Again, outflow could bring erratic gusts to 35 to 45mph. Keep a sharp lookout.

One item of concern is an arctic front moving down the western portions of the state Saturday. As this feature moves down the western Brooks Range Saturday afternoon, anticipate a west to northwest wind switch in the western region, with a slight cooling of temperatures but a decrease in relative humidity. There is a question on how far these dry northwest winds will make it, likely holding near the Yukon River corridor. However, this feature will shear apart and weaken as it moves southeast into the interior.

HYDROLOGY

Water levels in rivers continue to recede. We have cancelled or expired all flood hazards and flooding is no longer expected. Rivers will return to near normal levels through the week and into the weekend.

EXTENDED FORECAST DAYS 4-7

Upper level ridging persists over Northern Alaska, but is expected to gradually break down throughout the week as an Arctic trough digs down from the north. Thunderstorm potential will continue during the afternoons with chances moving northeast from the Eastern Interior to the Eastern Brooks Range/Northern Alcan Border through Wednesday afternoon. Lingering thunderstorm chances over the Western Interior and YK Delta through the week are also likely. By Thursday afternoon, thunderstorms will likely impact a large portion of the Western Interior, Eastern/Central Brooks Range, and White Mountains, with chances expanding to the Western North Slope by Friday afternoon.

As a result of the Arctic trough, high temperatures over the Tanana Valley are expected to cool to the low 70s/upper 60s by Wednesday. Accompanying the cooler temperatures will be rain showers, with the highest accumulations expected for the White Mountains and Fortymile Country. These showers are expected to last into next weekend.

Coastal Hazard Potential Days 3 and 4...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...Fire Weather Watch for AKZ934>945-947-953. Heat Advisory for AKZ833. PK...Small Craft Advisory for PKZ811. Small Craft Advisory for PKZ812. Small Craft Advisory for PKZ857. Small Craft Advisory for PKZ858.