Small Craft Advisory 191, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
508 PM AKST Tue Feb 25 2020

.ANALYSIS AND UPPER LEVELS...
There is a closed upper level ridge over the northern Bering Sea
that nudges into southwest Alaska. There is a strong vertically
stacked low over the southwest Gulf, moving northeastward.
There is a large vertically stacked low south of the western
Aleutians and slowly moving east. A frontal boundary stretches
west to east across the southern Bering, then across the eastern
Aleutians and western Alaska Peninsula into the southwestern Gulf.
A warm/occluded front associated with the Gulf low extends from
Kodiak northeast through the Valdez area into the Copper River
Basin, bringing snow to much of the Gulf coastal areas and Prince
William Sound. With surface high pressure to the north and low
pressure to the south, winds generally remain northerly over the
southern mainland and east-northeasterly over the Bering and
Aleutians.

&&

.MODEL DISCUSSION...
The numerical models are in good agreement through Thursday
afternoon. There are still some differences in the location of
the low in the Gulf. Models have continued to trend significantly
further east with this system. Thus, we now expect precipitation
to end much sooner in the week for the Prince William Sound area.
Forecast confidence is a little above normal today.

&&

.AVIATION...
PANC...VFR conditions and light north winds will persist.
Occasional gusty winds and/or a snow flurry are possible this
evening.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2...Wed and
Thu)...

Snow will continue to develop over the Gulf and coastal locations
through Wednesday as a storm centered over the southern Gulf
slowly moves north and weakens. Gusty winds are expected to
continue through late tonight and then taper down early Wednesday.
Gusty winds may ease through channeled terrain, however they
will continue through the end of the work week as a cold pool
remains over the Copper River Basin while the Gulf low tracks
toward the Northeastern Gulf. Inland locations will see scattered
showers this evening as the storm system sends upper level waves
across Southcentral.

The storm system weakens significantly late Wednesday into
Thursday as the low fills on an eastward track. A trough pattern
lingers over the northern Gulf on Thursday and Friday with a ridge
over the interior. The pattern will mainly be dry during this
period; however, a few showers are possible across eastern Copper
River Valley on Friday on as a weak boundary extends north from
the Gulf low.

&&

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 2...Wed and
Thu)...

As the low south of Kodiak continues to move to the northwest and
the high remains over the northern Bering: winds will relax over
the southwest tonight. Areas of blowing snow across Bethel and
surrounding areas will continue to weaken before ending Wednesday
morning. Drier conditions should prevail with temperatures
beginning to cool tomorrow as northwesterly flow brings in colder,
Arctic air.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 2...Wed
and Thu)...

As an area of low pressure continues to move east across the
Aleutian Chain, it will interact with an area of high pressure in
the northern Bering. This interaction will slow the progression
of the front, as the low weakens through Thursday afternoon. This
will propagate a showery pattern across the Aleutians and the
Bering. There is model inconsistency as to whether precipitation
makes it's way as far north as Saint Paul with this front.

&&

.MARINE (Days 3 through 5 Fri through Sun)...
On Friday a strong system will move into the Aleutians, and into
the Bering Sea Friday night and Saturday. This system will bring
widespread gales across the Aleutians, spreading northward across
the Bering through Sunday. Storm force winds are also expected
Friday night and Saturday across the central and western Aleutians
and the Bering Sea west of the Pribilofs. On Friday night into
Saturday there is also a chance of some westerly gales through
the Barren Islands area.

&&

.LONG TERM FORECAST (Days 4 through 7 Sat through Tue)...
On Saturday morning a strong low pressure system will be centered
over the western Aleutians, with a ridge over the southern Alaskan
mainland. This low will move north into the central Bering by
Sunday morning, and the ridge will move east into Canada. This
will open up moist southwesterly flow aloft over the southern
mainland, producing active weather Sunday and Monday. By Tuesday
things become considerably more uncertain. The current forecast is
for the upper low to open up into a trough and slide eastward
across the mainland. However, there is a large spread in the
possible solutions and forecast confidence by Tuesday is low.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Blizzard Warning 131 (Thompson Pass).
 		 Winter Weather Advisory 171.
MARINE...Heavy Freezing Spray Warning 179 414 185.
		 Gale Warning 185 411 412 119 120 127 128 130
				      131 132 138 139 352.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...BL
SOUTHCENTRAL ALASKA...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CK
MARINE/LONG TERM...BL