273
FXAK69 PAFG 210047
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
447 PM AKDT Mon May 20 2024


.SYNOPSIS...
Warm and dry conditions over the Eastern Interior will trend
wetter and cooler by Thu. The North Slope is cloudy and warmer
than normal with nocturnal coastal fog that will trend cooler and
wetter late this week. The cool and wet West Coast becomes warmer
and drier on the weekend.

Surface Pattern...
Strong high pressure north of the Arctic Coast will persist
through late this week. This is causing east winds along with
stratus and night time fog along the Arctic Coast that will
persist into Thu. There are scattered light snow showers or
flurries as well.

A thermal low pressure trough stretching from Northway to Fairbanks
to Bettles and remain in place through Tue, then move to Eagle to
Coldfoot on Wed and remain there into Thu. There will be isolated
showers along this trough today through Wed along with low RH and
warmer than normal temperatures, with a few thunderstorms
possible along the trough near the ALCAN Border on Thu. Afternoon
winds will gust blowing into this trough each day.

High pressure south of the Alaska Range is causing south winds to
blow into this thermal trough through Alaska Range Passes today
and Tue. Southerly Chinook winds of 25-30 mph gusting to 45 mph
will blow along the Alaska Range Tue afternoon through Wed
afternoon and will bring Red Flag conditions to Delta Junction to
Donnelly Dome area Tue PM, and near Red Flag conditions Wed PM.
Chinook winds will decrease Wed night and end Thu.

A low in the southern Bering Sea will move to the Kuskokwim Delta
by Wed night and then move inland and weaken. A weather front
stretching from this low to the YK Delta will move north to the
Bering Strait to Illiamna by 4pm Tue, and to Point Hope to Denali
by 4pm Wed, then to Point Hope to Northway by 4am Thu before
weakening. A significant amount of rain will accompany this front
over the West Coast and Western Interior tonight through Wed with
some drying over Western AK on Thu. . Rain is likely over the
Central Interior Wed night into Thu with 0.25-0.50 inch. A chance
over the Eastern Interior Wed PM will become likely rain on Thu.
Several inches of snow will fall above 3000-4000 ft Wed night and
Thu.

.DISCUSSION...
Models initialize well aloft at 12Z, and show similar solutions
aloft through 4pm Wed. After that time models start to diverge on
short wave details Wed night. The NAM is somewhat of an outlier
starting Wed night with lower 500 mb heights than all the other
models. At this time will use a blend of models for features aloft
through 4pm Wed, then use a blend of the ECMWF, GFS and Canadian
for features aloft Wed night into Thu. Models all develop a weak
to moderate Chinook blowing across the Alaska Range on Tue and Tue
night, with the NAM keeping the Chinook stronger later Wed night
than other models. As previously stated we will not use the NAM
solution on Wed night or Thu.

The long wave pattern consists of a trough over the Bering and
Chukchi Seas, a ridge over the NE Pacific north over central
Alaska, and another trough over NW Canada. This pattern is
progressive with the ridge shifting over Eastern AK on Tue and
the first trough over the Bering and Western Alaska. A series of
short wave troughs will move east across southern AK from Wed
through the weekend, eventually pulling the long wave east over
Mainland AK by the weekend. This will change the current warm
Eastern Interior and North Slope cooler and wetter late this
week, while the cool and wet West Coast becomes warmer and drier
on the weekend.

A short wave trough over the SE Interior will move east this
evening. This is causing scattered showers over the SE Interior
that will dissipate tonight.

A second short wave over the SE Bering Sea will move over SW AK
tonight, to the Seward Pen to Kenai Pen on Tue, to Point Hope to
Prince William Sound on Tue night, and to Point Hope to Yakutat
on Wed. A trailing low aloft will move over SW AK on Wed, then
over AK Range Wed night and over the SE Interior on Thu. This
second short wave will push an occluded front with mainly rain
and elevated snow east with it. This will cause a weak to moderate
Chinook to blow across the Alaska Range on Tue and Tue night, the
Chinook decreasing Wed night and ending Thu. A significant amount
of rain will accompany this first short wave over the West Coast
and Western Interior tonight through Wed. Expect significant rain
with the low aloft over the Eastern Interior on Wed night and Thu.

At 850 mb temperatures range from +4C over the SE Interior to 0C
along the Arctic Coast and -4C over the SW Coast. The The West
Coast will remain about the same temp Tue while the SW Interior
will cool 2-4C, and the North Slope and Eastern Interior will warm
several degrees C. Most of the Interior will cool a few degrees
on Wed, while the West Coast and North Slope remain about the
same. Most areas will cool on Thu.

With precipitation, the ECMWF is a but faster moving it north over
Western AK tonight and Tue, then models in better agreement Tue
night and Wed. Wed night and Thu the NAM has much higher amounts
in some areas and maintains the chinook shadow too long. Prefer a
blend of models for precip through Wed, then a blend of the ECMWF
and GFS for precip for Wed night and Thu. Highlights include:
rain spreading north over Western AK tonight and Tue, then
continuing on Tue night and diminishing on Wed. Expect 0.25-0.50
inch of rain over most of that area, with several inches of snow
above 2000 ft. Rain likely over the Central Interior Wed night
into Thu with 0.25-0.50 inch. Chance over the Eastern Interior Wed
PM becoming likely on Thu with 0.25-0.50 inch there. Several
inches of snow will be above 3000-4000 ft Wed night and Thu.

At the surface, models initialize well at 12Z. Models show similar
solutions at the surface through Thu. Will use a blend of the
GFS, Canadian and ECWMF at the surface since they are the
preferred solutions aloft. Siginifcant winds are: Easterly 25 kt
over the Northern Bering Sea tonight and Tue, spreading to the
Chukchi Sea on Tue then decreasing Wed. Southerly Chinook winds of
25 mph gusting to 45 mph along the Alaska Range Tue afternoon
through Wed afternoon will bring near Red Flag conditions to Delta
Junction to Donnelly Dome area Tue PM.

Coastal Hazard Potential Days 3 and 4...None.

&&

.FIRE WEATHER...
A thermal low pressure trough stretching from Northway to
Fairbanks to Bettles and remain in place through Tue, then move to
Eagle to Coldfoot on Wed and remain there into Thu. There will be
isolated showers along this trough today through Wed along with
warmer than normal temperatures, with a few thunderstorms
possible along the trough near the ALCAN Border on Thu. Afternoon
winds will gust blowing into this trough each day.

High pressure south of the Alaska Range is causing south winds to
blow into this thermal trough through Alaska Range Passes today
and Tue. A weather front moving over SW Alaska tonight will move
over the Western Interior on Tue, and then over the Central
Interior on Wed.

This will cause southerly Chinook winds of 25-30 mph gusting to
45 mph along the Alaska Range Tue afternoon through Wed afternoon
and will bring Red Flag conditions to Delta Junction to Donnelly
Dome area Tue PM and near Red Flag conditions Wed PM. Chinook
winds will decrease Wed night and end Thu.

A significant amount of wetting rain will accompany this first
short wave over the West Coast and Western Interior tonight
through Wed. Expect wetting rain over the Eastern Interior on Wed
night and Thu.

&&

.HYDROLOGY...
The ice jam on the Yukon at Pilot Station released Sunday
afternoon and water levels have now fallen 5 ft and flooding is
ending there. Downstream at Mountain Village ice started moving
Sun afternoon and the water level rose 5 ft Sun night. Running ice
and high water remain at St Mary`s, Pitkas Point and Mountain
Village and a ice jam flood watch remains for those areas through
Tue. The break up front is now downstream of Mountain Village and
will likely get to the Yukon Delta at Alakanuk, Emmonak, Nunam
Iqua and Kotlik sometime between late Tue night and Fri, bringing
the risk of ice jam flooding to those areas Tue night through Fri.
Watches are out for all these areas.

The water levels along the Porcupine River at the Border rose to
record levels over the weekend due to heavy snowmelt. This high
water is expected to reach Ft Yukon on Wed, where it will
gradually fills sloughs and swales east of Ft Yukon and eventually
bring high water into Ft Yukon late this week with high water
continuing into next week. A flood watch is valid front this Wed
through next week Wed.

There are no new reports about the Buckland River, but there was a
reported ice jam downstream of Buckland a couple days ago with
rising water levels. We will continue to monitor.

River on the North SLope are beginning to flow with water flowing over
ice with some open water areas. Those area will continue to see
increasing melt this week.


&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Flood Watch for AKZ825.
     Flood Watch for AKZ826.
     Flood Watch for AKZ833.
     Red Flag Warning for AKZ937.
PK...Small Craft Advisory for PKZ801.
     Brisk Wind Advisory for PKZ806.
     Small Craft Advisory for PKZ807.
     Small Craft Advisory for PKZ811.
     Small Craft Advisory for PKZ812.
     Small Craft Advisory for PKZ816.
     Small Craft Advisory for PKZ817.
     Small Craft Advisory for PKZ850.
     Small Craft Advisory for PKZ851.
     Small Craft Advisory for PKZ852.
     Brisk Wind Advisory for PKZ853.
     Brisk Wind Advisory for PKZ854.
     Brisk Wind Advisory for PKZ855.
     Brisk Wind Advisory for PKZ856.
     Brisk Wind Advisory for PKZ857-858.
&&

$$

JB