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FXAK69 PAFG 152122
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
122 PM AKDT Sat Jun 15 2019

.SYNOPSIS...
Highlights are:
Isolated thunderstorms over the southern Interior today and Sun.
Significant rain over the Southeast Interior and Alaska Range Sun
through Tuesday. Snow possible eastern Brooks Range Sun night and
Mon. North wind increasing to 25 mph along the West Coast and
through the Brooks Range Sun night and Mon. Low clouds and fog
returning to the North Slope early Sun.

Aloft...
Long wave trough now setting up over AK and the Gulf of AK as as
series of short wave trough drop south from the high Arctic across
Western Alaska. This long wave trough will progress east over NW
Canada and Eastern AK by the middle of next week.

For the Northern AK expect this to mean near normal temps and
showery conditions south of the Brooks Range, but possible
significant precip on the north side of the Brooks Range as short
waves drop south over the area.

One short wave over the Western Interior will move west to St
Matthew Island and St Lawrence Island by 4am Sun. Isolated to scattered
showers will move west with this trough.

A second short wave near 80N, will move to just north of the
Arctic Coast of Alaska by 4am Sun, to 200 NM notrh of Demarcation
Point to Point Hope by 4pm Sun, to Barter Island to Nome by 4am
Mon, to Barter Island to Bettles to the YK Delta by 4pm Mon, to
Anaktuvuk Pass to Golovin to Bethel by 4am Tue, then dissipating
in place. Expect rain and snow with this trough over the North
Slope Sun night and Mon. Expect mainly north winds gusting 25 mph
to spread south with the trough over the Brooks Range and West
Coast Sun night and Mon.

A third short wave trough over the St Elias Mtns will move over
the SE Interior tonight. This will cause scattered showers over
the SE INterior through tonight.

A fourth short wave in the NE Gulf of Alaska will move over the SE
Interior Sun and then slowly weaken in place through Tue. This
will bring additional moisture and widespread showers to the SE
Interior and Alaska Range Sun through Tue.

Surface....
A Cold front that stretches from Central to Galena to Gambell
will weaken tonight. NE winds 15g20 mph along this front will
diminish this evening as the front weakens. Conditions are cooler
and drier north of the front.

A thermal trough that lies from Anvik to Fairbanks to Eagle will
remain fairly stationary through Mon. Convection will be focused
along this trough, with scattered showers and isolated PM
thunderstorms mainly along and south of this feature. With LI of
zero to -1 and CAPE values of 100-200 Joules, expect isolated and
weak thunderstorms.

A 1013 mb low 300 NM north of Utqiagvik will move to 300 NM north
of Barter Island as a 1011 mb low by 4am Sun, to 300 NM northeast
of Barter Island as a 1009 MB low by 4pm Sun, and then to Banks
Island by 4am Mon. A warm front stretching south from this low to
Utqiagvik will move to Deadhorse by 4am Sun, and then move east of
Barter Island Sun afternoon. Stratus clouds and fog will spread
east across the Arctic Coast with the warm front.

An Arctic cold front trailing this low will move to just north of
the Arctic Coast of Alaska by 4pm Sun, to along the Brooks Range
Crest by 4am Mon, and to Old Crow to Ambler to the Bering Strait
by 4pm Mon, then to Old Crow to Kotzebue to the YK Delta by 4am
Tue, then weakening. Expect a rain snow mix over the Eastern North
Slope with this front Sun night and Mon, with 1-2 inches above
2000 ft in the Eastern Brooks Range from late Sun night to Mon.
South of the Brooks range expect mainly winds conditions to
accompany the front with north winds 15g25 mph along and following
the front, with stronger winds along the West Coast and in the
Brooks Range Passes. Surface temperatures will fall about 5-10F
with the front, but conditions will remain mainly dry south of the
Brooks Range.

On Tue the thermal trough along with the warm unstable air will
push north over the Northern Interior to bring and isolated
thunderstorms to most of the Interior, while the scattered showers
remain of the Southern Interior where the highest moisture levels
remain.

&&

.DISCUSSION...
At 12Z at h500, models all initialize 10-20m too low on h500
heights over Fairbanks, McGrath, Nome and Barrow RAOBS. This
results in the h500 low centered over Central Interior Alaska to
be initialized a bit too deep on models. This weaker feature may
result in less convection today in the Central and Western
Interior than models indicate, but then this low moves west over
the Bering Sea tonight. After tonight, the models show a similar
pattern aloft with a series of short wave troughs making their way
south over the Western Interior and West Coast of Alaska, but
models differ slightly on timing and placement of short wave
troughs. The GFS is slightly faster and slightly further west in
it movement of the short waves than the ECMF and NAM. At this time
favor the faster GFS solution as this dynamic pattern would favor
faster movement. That being said, we will indicate more
uncertainty on Mon and Tue due to the differences between models,
and since these short waves are coming from the data sparse high
Arctic.

Models verify well at surface at 15Z. Models show similar
solutions through 4pm Sun. After that the GFS has a bit stronger
winds along the West Coast which fits with its stronger and faster
short waves aloft, so we will use the GFS winds for the most
part, taking account of the stronger gap winds throughout he
Alaska Ran Brooks Range that are not resolved by models.

With Precip, the GFS and ECMF have a broader areal coverage than
the NAM. Considering the uncertainty of short wave location and
timing, the broader coverage is warranted, so we prefer the GFS
areal precip coverage. All models indicate significant precip
amounts the SE Interior and Alaska Range Sun through Tue. At this
time we will go with GFS amounts, but need to be alert for heavier
amounts indicated by the NAM. The GFS does indicate 0.50-1.50 inch
of rain through Tue SE of Minchumina to Salcha to Eagle.

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

&&

.FIRE WEATHER...
RH should remain above 25% most areas the next several days, with
the exception of the NE Interior and West Coast from the the
Seward Peninsula north, where RH could reach down to 20% today.
Those areas also have winds of 15g20 mph today.

Isolated thunderstorms over the southern Interior today,Sun and
spreading slightly more north on Mon.

Dry and windy conditions expected along the West Coast and
Northern Interior Sun night through Mon night. Temps should remain
below 75 those areas though.

&&

.HYDROLOGY...
Expect high water on North Slope rivers East of the Colville River
to continue for the next several days.

Models indicate 0.50-1.50 inch of rain Sun through Tue SE of
Minchumina to Salcha to Eagle. Right now it looks like the precip
will be over a 48hr period so will not cause flooding, but will
need to be alert for heavier rainfall occurrence and the
possibility of high water and mudslides in steep terrain in the
Alaska Range and the Fortymile country Mon and Tue.


&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory for PKZ210-PKZ220-PKZ225.
&&

$$

JB JUN 19
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