538
FXAK68 PAFC 201416
AFDAFC
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
516 AM AKST Mon Jan 20 2025
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Today
through Wednesday)...
Monday will bring a brief respite from the otherwise active weather
that`s been occurring across Southcentral Alaska in recent days.
Precipitation across the eastern half of the Copper River Basin,
primarily east of the Richardson Highway, will gradually clear out
this morning as the associated trough ejects eastward. Ridging will
then amplify across the area in wake of the system, leading to
generally quiescent weather. Low clouds and patchy fog may be a bit
slow to scour out this morning across the northern Cook Inlet,
portions of Anchorage, and the Mat-Su without a stronger mixing
mechanism, and as light southerly flow carries low-level moisture
into these areas.
Heading into tonight and tomorrow, attention turns towards an area
of low pressure moving towards the southern AK Peninsula, and the
associated front pivoting northward into the western Gulf of Alaska.
A tightening pressure gradient and down-inlet flow will help clear
out any remaining fog/stratus across the Kenai, Anchorage, and Mat-
Su. Simultaneously, widespread small-craft and then gale-force
winds will begin to spread across the Gulf. Model consensus
indicates the front should reach Kodiak Island late tonight and
then the Kenai Peninsula Tuesday afternoon and evening.
This front will bring about many of the same impacts as the last,
though perhaps a bit weaker and quicker moving. Ridgetop winds will
once again be rather strong, with gusts in excess of 60 mph not out
of the question of the Anchorage Hillside and other higher elevation
areas. Precipitation will largely be confined to the typical
windward locations of the eastern Kenai Peninsula and south slopes
of the Prince William Sound and Chugach Mountains. Cooler residual
air and short duration of return flow before the arrival of this front
will likely produce slightly lower snow levels than with the last
couple systems. At this point in time, snow levels look closer to
500 ft, though higher precipitation rates may occasionally drag
snow down to sea level. Turnagain and Thompson Passes will once
again be the `winners` of this system, with snow amounts expected
to be in the 6 to 12 inch range. Brief periods of 1"/hr rates may
be possible, which would ultimately lead to whiteout conditions /
reduced visibility at times in those locations.
Precipitation will taper off Tuesday night into Wednesday behind the
front, though upslope flow is likely to keep precipitation lingering
along coastal mountains, as well as the Valdez-Thompson Pass area.
The upper-level trough and associated weak surface low will quickly
move eastward across the northern Gulf on Wednesday, bringing
continued unsettled weather over the open water, though additional
impacts inland are not expected at this time.
-Brown
&&
.SHORT TERM FORECAST SOUTHWEST ALASKA AND THE BERING
SEA/ALEUTIANS (Monday morning to Thursday morning)...
An occluded front brings rain to the Aleutians/AKPen, reduced
visibility from snow across the Pribilofs this morning, and snow
for the Southwest mainland tonight into Tuesday. The responsible
low remains south of the eastern Aleutians before crossing the
AKPen Tuesday morning. Warm southerly, low-level flow behind the
front will limit snow to higher elevations, melting snow before it
reaches the ground for lower elevations. Below freezing
temperatures aloft should prevent freezing rain and sleet. This
warm airmass pushes inland toward Bethel, across Bristol Bay and
past Dillingham to Lake Iliamna on Tuesday.
As the main core of the former low passes over the Southwest by
Wednesday morning, cold air wrapping around the back of the system
will move in from the south, dropping temperatures below freezing
north of Dillingham by Wednesday afternoon. Lingering moisture
could produce snow showers north of Dillingham through Wednesday
afternoon.
Meanwhile, in the western Bering, a Kamchatka low is preparing to
send its front sweeping into the Southwest coast by Thursday
morning with widespread gales and areas of storm-force wind. This
may be followed by a long fetch of water vapor and an embedded
low streaming into the region from the North Pacific. This
tentatively appears to be the start a several-day period of
precipitation lasting into the weekend, followed by cold air
sweeping across the Bering Sea which will decisively switch
precipitation to snow by the end of the week. A pattern change
appears to be on the way.
&&
.LONG TERM FORECAST (Days 4 through 7: Thursday through
Sunday)...
Active weather will continue along the south central coast of
Alaska ahead of a large area of low pressure expected to move into
the state from the west around midweek. This low will transit
southwest and south central Alaska by Friday and Saturday and
bring much colder temperatures to most of the state for the
weekend. By Sunday, high pressure will bring drier conditions
gradually building east into the AKPEN and western Kenai by late
Sunday.
&&
.AVIATION...
Fog/mist and drizzle persists through later this morning resulting
in alternating MVFR to VFR conditions. Southerly to southeasterly
winds prevail in the afternoon leading to VFR conditions afterward
and into tomorrow morning. A front arrives tomorrow afternoon
bringing southwesterly wind gusts and VFR conditions.
$$
$$
087
FXAK69 PAFG 201542
AFDAFG
Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
642 AM AKST Mon Jan 20 2025
.SYNOPSIS...A series of storms will continue to impact the West
Coast, with the next storm arriving late tonight bringing heavy
snow and blowing snow. Winter Storm Watches and Warnings are in
effect. The Interior will be mostly dry with well above normal
temperatures through the rest of the week, along with periods of
strong south winds through Alaska Range passes and east winds at
Delta Junction. The North Slope will also have temperatures well
above normal through Tuesday, with cold air slowly filtering back
in from the west. A significant pattern shift will take place late
this week, likely bringing a number of strong storms to the West
Coast and precipitation into the Interior.
&&
.DISCUSSION...
Key Weather Messages:
Central and Eastern Interior...
- Fairbanks picked up 1-2" of snow overnight. Snowfall will
tapering off this morning.
- Heavy snow fell along the Richardson Highway in the eastern
Alaska Range overnight. Snow is tapering off this morning. The
Winter Weather Advisory has been cancelled.
- Mostly dry conditions expected until the end of the week with
high temperatures well above normal, mainly in the 20s above
zero.
- South winds gusting to around 50 mph through Alaska Range passes
and east winds gusting to around 40 mph at Delta Junction are
expected at times Tuesday and Wednesday.
West Coast and Western Interior...
- Monday there will be some brief calm conditions as another low
paired with a strong arctic front moves into the Bering by
Monday evening. This arctic front will potentially bring a
narrow band of long duration heavy snowfall from the Y-K Delta
to the Kobuk Valley. The exact location of the band is still
uncertain, however currently we are looking at it to be from
Hooper Bay to Unalakleet then to Ambler with it`s western edge
of the band being somewhere in between Elim and Nome. Snow
totals could be up to a foot in some spots depending on snow
ratios. Winter Storm Watches have been upgraded to Warnings for
most of the area, except for along where we expect the western
edge of the snow band to be. These have been left as Watches as
a lot of uncertainty still remains.
- Another low pressure system moving into Bristol Bay on Tuesday
morning looks to bring northeasterly wind gusts up to 35 mph
from the Seward Peninsula to the Y-K Delta. We could see
significant visibility restrictions in areas that are receiving
the heaviest snow as well as gusty winds.
- After this next system moves out of the area Wednesday morning,
there will be another system Thursday and Friday. This system
looks to be bring heavy snow initially, then mixed precipitation
as it moves northeast through Saturday. Expect this to be an
impactful system.
North Slope and Brooks Range...
- Well above normal temperatures continue today from the Brooks
Range to the Arctic Coast. Expect temperatures mainly in the
20s, with colder air filtering back in from west to east through
Wednesday.
- Falling snow along with southerly gap winds through the Brooks
Range passes up to 40 mph will cause blowing snow and low
visibility through Tuesday. A Winter Weather Advisory is in
effect.
Forecast Analysis and Confidence...Weak high pressure exists over
Interior Alaska with weak low pressure in the arctic and in the
Aleutians. Weak southwest flow persists aloft as a deep and cold
upper level low lies over Eastern Siberia. Ridging aloft will
build over the Interior today as a warm front spreads north along
the West Coast, bringing snow before halting from Savoonga to
Nome to Anaktuvuk Pass. Depending on where exactly this system
stops, areas beneath it will likely receive heavy snow of up to or
even slightly more than a foot through Wednesday afternoon. A
weaker low pressure system moves to the Western Bering Sea on
Wednesday night, bringing another round of light snow through
Thursday before a much stronger storm takes aim at the region on
Friday.
Models are not in good agreement on the placement of precipitation
with the first system. The ECMWF has been the most consistent, and
the forecast reflects that solution with a more SW/NE oriented
snow band. The NAM and GFS bring the precipitation further west
and orient the band more N/S. Opted to keep the western areas as
Winter Storm Watches in case daytime models runs begin to show
more precipitation than the ECMWF is showing there. Otherwise, we
used a general blend of models for the forecast overnight. We
blended the NAM and NAMNEST for winds and made some hand edits to
increase gap winds through Alaska Range passes and at Delta
Junction beginning Tuesday afternoon.
Extended Forecast Days 4-7...A major pattern shift is likely by
the end of the week as flow turns more southwesterly and a number
of strong low pressure systems enter the Bering Sea. While the
exact tracks of these lows are still uncertain, the overall
pattern is favorable to bring an abundance of warm air and
precipitation northward over western Alaska and possibly into the
central and eastern Interior. Expect a strong storm with high
winds across the West Coast on Thursday and Friday, with
increasing chances for heavy precipitation in the Interior Friday
through Sunday. Models indicate an increasing probability for very
cold temperatures early next week behind this system.
Coastal Hazard Potential Days 3 and 4...None.
&&
.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Winter Storm Warning for AKZ813-819.
Winter Storm Watch for AKZ816.
Winter Storm Watch for AKZ822-823.
Winter Storm Warning for AKZ824>826-829-830.
Winter Weather Advisory for AKZ809.
PK...Heavy Freezing Spray Warning for PKZ801-802.
Small Craft Advisory for PKZ801.
Gale Warning for PKZ802.
Brisk Wind Advisory for PKZ811.
Brisk Wind Advisory for PKZ812-858-859.
Brisk Wind Advisory for PKZ813.
Brisk Wind Advisory for PKZ814.
Brisk Wind Advisory for PKZ815-860-861.
Brisk Wind Advisory for PKZ850.
Brisk Wind Advisory for PKZ853.
Brisk Wind Advisory for PKZ857.
&&
$$
CHRIEST
418
FXAK67 PAJK 201441 CCA
AFDAJK
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
452 AM AKST Mon Jan 20 2025
.SHORT TERM...Key Points:
-A front moves through the panhandle on Monday, bringing with it
rain, wind, and accumulating snow for a few locations.
-By Monday night, diminishing showers give way to chances of fog.
-Break in precipitation on Tuesday, before another system arrives
late Tuesday night through Wed morning.
The active weather pattern looks set to continue through the day
on Monday, as a front pushes through the panhandle during the day,
Given the pre-existing warmer temperatures, along with the
resurgence of warm air advection, most locations will remain
largely rain during the system. A few locations, including Juneau,
have seen a brief period of snow as heavier rainfall rates
resulted in cooler wet bulb temperatures enabling a changeover.
However, the aforementioned WAA will swiftly overwhelm these
locations through the morning hours, and what little snow does
fall will likely be on the lower side of snow ratios - which is to
say, slush. The one exception to this is at areas of elevation,
and some minor snow accumulation is expected across the Highways
at elevation.
As the system departs Monday afternoon through evening, lingering
showers will bring continued chances of rain, though these will
diminish in coverage Monday night through Tuesday. Chances of fog
will arrive across much of the area Monday night as well, given
the collapsing pressure gradient and consequently significantly
lower wind speeds. Temperatures will dip into the low 30s Monday
night, and some areas near sea level could go below freezing,
especially if any breaks in the cloud deck emerge.
Tuesday will see some lingering showers, but will nevertheless
largely be a `break` day ahead of the next gale force front
arriving Tuesday night. For additional information, see the long
range forecast discussion.
.LONG TERM...Key Points:
-Brief break in widespread precipitation Tuesday.
-Gale force front pushes into the Gulf by Tuesday night, into the
Panhandle early Wednesday morning bringing widespread showers
across the area.
-Strong high pressure moves over the eastern Gulf of Alaska by
Thursday, keeps persistent on-shore showery regime into the
Northern Panhandle through the end of the week.
Discussion:
Kicking off the mid range on Tuesday with a brief break in
widespread precip across the area as ridging moves aloft then
eastward through the day. Weather break doesn`t last long as the
main weather story will be an approaching Gale force system from
the Gulf by Wednesday morning, overspreading SEAK through the day.
Forecast remains on track with highest 24hr rainfall totals coming
across the NE Gulf with Yakutat forecast around 1 to 2 inches
Wednesday through Thursday morning. As front pushes inland, have
current forecast temps in the mid 30s so will mostly likely see a
rain/snow mix during onset before gradually turning to predominate
rain as temperatures warm to the upper 30s through Wednesday
afternoon. Highest confidence in snowfall will be along the upper
elevations of the Haines and Klondike Highways with accumulations
ranging 2 to 4 inches over a 24hr period. Not anticipating
widespread hazards with this frontal system at this time.
Moving into the latter half of the extended, an anomalously
strong surface high and stout upper level ridging will shift into
the southern Gulf through Thursday. Main caveat will be the
accompanying persistent on-shore flow and scattered showers for
the northern panhandle into Saturday as a strong fetch of tropical
Pacific moisture rides the western periphery of the high.
&&
.AVIATION...The front continues to move east across the panhandle
keeping ceilings and visibilities MVFR with times of IFR. The
strongest part of the front is now to the east of Yakutat allowing
winds to diminish slightly and wind shear to reduce. These
diminishing winds will occur across the rest of the panhandle by
late this morning, as the front passes. Skagway and Haines will hold
on to these stronger winds longer than other areas, diminishing in
the afternoon. One impact, after the front leaves the panhandle, is
fog. This fog would occur due to diminishing winds, increasing dew
points, and breaks in the clouds.
&&
.MARINE...Winds in the inner channels will largely remain 20 to
25 kt through the morning hours (fresh to strong breeze) before
diminishing to 10 to 15 kt (light to moderate breeze) by Monday
night. Some areas could see localized stronger winds with the
front passing by. Waveheights in the outer coastal waters will
subside from upwards of 16 ft down to 7-8 ft by Monday night.
Winds and waves in the Gulf will be on the rise again on Tuesday
as another system approaches SE AK, with the inner channels
following suit Tuesday afternoon through night.
&&
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind until 3 PM AKST this afternoon for AKZ318.
Strong Wind until 9 AM AKST this morning for AKZ325.
MARINE...Small Craft Advisory for PKZ012-013-022-031>036-053-641>644-651-
652-661>664-671-672.
&&
$$
SHORT TERM...GFS
LONG TERM....NM
AVIATION...EAB
MARINE...GFS
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