679
FXAK69 PAFG 242259
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
259 PM AKDT Sat May 24 2025

.SYNOPSIS...Heavy showers and thunderstorms across the Interior
will be the main weather hazard through Monday. An impressive
amount of thunderstorm activity is expected for this early in the
year. Little change in the overall pattern will keep lightning in
the forecast through the week. The area of biggest concern for
heavy rainfall is from Delta Junction to Tok along the Alaska
Highway on Sunday night into Monday morning. Areas of low stratus
persist through the weekend on the North Slope, with fog
increasing in coverage through next week. A shortwave will bring
showers to the Lower Yukon Valley, Yukon Delta, and southern
Seward Peninsula Coast through Sunday, though the rest of the West
Coast will be mainly dry. Breakup has begun on the Porcupine
River. See Hydrologic Outlook for details.

&&

.KEY WEATHER MESSAGES...
Central and Eastern Interior...
-Showers and thunderstorms will be the main concern in the
 forecast through this week. Expect a sharp increase in lightning
 activity with usually significant thunderstorm activity for the
 end of May.

-Showers and thunderstorms through Monday may produce very heavy
 rain. See Special Weather Statement for details. The area of
 biggest concern is from Delta Junction to Tok along the Alaska
 Highway on Sunday night into Monday morning.

-Temperatures remain mostly steady through next week with highs in
 the 60s and lows in the 40s.

West Coast and Western Interior...
-Warming trend through the weekend. Highs increase to near 70 by
 Monday for Interior Valleys. 30s and 40s near the coast today
 will increase to 40s and 50s by Monday.

-A shortwave will bring showers to the Lower Yukon Valley, Yukon
 Delta, and southern Seward Peninsula Coast through Sunday.

-Mostly dry conditions expected elsewhere through the holiday
 weekend except near thunderstorms in the southwest Interior
 northeast of Holy Cross.

North Slope and Brooks Range...
-Winds become westerly behind the arctic front passage on Sunday.

-Areas of low stratus persist through the weekend.

-Light snow accumulations from Atigun Pass northeast to Point
 Thomson and Kaktovik tonight through Monday morning.
 Accumulations will be less than 2 inches.

&&

.FORECAST ANALYSIS AND DISCUSSION...The large scale pattern aloft
consists of a low in the Arctic, a low in the western Bering Sea,
a low in the eastern Gulf of Alaska, and weak ridging pushing west
over the Interior from the Yukon Territory. Showers and
thunderstorms have developed this afternoon across most of the
Interior as the first of a series of shortwaves moves east to west
after being spun off of the low in the eastern Gulf of Alaska.
These storms are very slow movers and will drop heavy rain in
areas, with similar conditions expected Sunday. Models have
really caved to yesterday`s ECMWF solution of keeping the low in
the Arctic and associated trough and cold air much further north
than other models on Sunday and Monday. Yesterday`s forecast had
this trough swinging through the Interior through Monday,
stabilizing everything behind it and also dragging moisture north
to the Brooks Range and across the eastern Arctic Coast as snow.
With the trough also looking to remain further north now, this
will allow shortwaves from the east to continue to rotate through
the Interior uninhibited through at least the middle of next week.
This looks to keep conditions warmer and unstable with showers
and thunderstorms each afternoon. It also decreases the chance for
significant snow across the Brooks Range and eastern Arctic Coast.

This is still a very high uncertainty pattern, so the timing of
storms and precipitation for any given location will be very
difficult to nail down. However, the instability combined with
850 mb temperatures nearing 9 C across the eastern Interior on
Sunday afternoon and PWATs remaining 0.6" or higher (greater than
the 90th percentile for this time of year) through Tuesday
afternoon will bring a high probability of a number of significant
thunderstorm days and areas of very heavy rain. By Monday, storms
will have motion and move faster, so the heavy rain threat will be
limited to areas of training storms. It is possible that the
heaviest rain is overnight Sunday into Monday along the north
slopes of the Alaska Range east of Delta Junction. With synoptic
forcing overnight Sunday into Monday, thunderstorms will likely
continue through the night.

Other features include a weak shortwave associated with the low in
the Bering that may spark isolated thunderstorms across the Lower
Yukon Valley this afternoon, and another shortwave that will bring
showers there, to the southern Seward Peninsula Coast and to St.
Lawrence Island on Sunday. Tuesday also looks to be an active day
for showers and thunderstorms, especially out near McGrath.

&&

.FIRE WEATHER...With surface moisture levels and RH forecasted to
remain well above normal for this time of year, and temperatures
near normal, the main concern will continue to be lighting which
will ramp up significantly starting today. Easterly flow will
persist through the week, and a number of significant lightning
days are expected particularly in the eastern Interior, near
McGrath, and along the north side of the western Alaska Range.
Widely scattered thunderstorms are expected today from Fairbanks
east to the Alcan Border and north to the Yukon River with
isolated thunderstorms across the rest of the Interior. Widely
scattered thunderstorms expand west to Minchumina on Sunday and
to McGrath on Monday. Thunderstorms are not expected north of the
White Mountains on Monday as the Arctic trough to the north
provides a weak push of cold air to stabilize the area enough to
prevent thunderstorms. Thunderstorms will continue with
significant activity across the Interior and particularly the
eastern Interior through the week. All storms will be wet. Storms
may persist through the night Sunday night into Monday morning east
of Delta Junction.

&&

.HYDROLOGY...The Porcupine River at Old Crow (Yukon Territory) began
breakup last night. An ice jam remains in place just downstream
from Old Crow with minor flooding occurring. The Yukon River is
currently at below average flow for this time of year and snowmelt
flooding is not expected at Fort Yukon even once the Porcupine
breaks up. Expect water on the Porcupine at Fort Yukon to be
highest in 7 to 9 days, so sometime around June 1. On the Kobuk
River, satellite imagery shows the breakup front right at Ambler
with webcams showing ice sheets shifting and moving downstream in
front of town while consolidating some in main channels. Water
levels have also risen just upstream and are beginning to fill in
low lying sandbars. A local observer in Tanana reports that the
Yukon River is ice free past Tanana and that the first two barges
of the season have passed by running downstream.

Creeks and streams in the eastern Interior may rise rapidly under
areas of heavy rain through early next week. Rising freezing
levels on Sunday will allow snowmelt from high terrain above
Cathedral Rapids and Sheep Creek along the Alaska Highway to add
to rainfall in those streams. This may cause very high water in
these streams along the Alaska Highway. The Chena and Salcha
Rivers will also likely see rises. The Chena at the mile 40 CHSR
bridge is forecasted to rise to near action stage by Tuesday
morning, and may continue to rise if additional heavy rain is to
fall through the middle to end of next week. The local observer at
Lake Minchumina reports that the lake is now completely ice free.

&&

.EXTENDED FORECAST DAYS 4-7...The extended forecast period looks
cooler and wetter than normal for most of the area. The details
will be determined by the fate of the low currently in the Arctic.
Some models drop it south over the West Coast while others bring
it northeast away from the area toward the middle to end of next
week and form a second low over NE Russia and drop that south over
the West Coast. The first solution would be cooler for the west
coast and warmer for the eastern Interior, while the second
solution would keep conditions largely similar to what they are
now. Weak high pressure over the North Slope will make dense fog
increasingly likely late this week.

Coastal Hazard Potential Days 3 and 4...None

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...None.
PK...Small Craft Advisory for PKZ804-805-852.
     Small Craft Advisory for PKZ806-854.
     Small Craft Advisory for PKZ816-817-851.
&&

$$

Chriest