Gale Warning 316, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
512 PM AKDT Wed Apr 11 2018

.ANALYSIS AND UPPER LEVELS...

Low pressure filling the Gulf of Alaska is the main player in the
Gulf of Alaska. Rain has been observed in many coastal regions of
Southcentral Alaska. With a low pressure system sitting just a
few miles east of Kodiak City this morning, the eastern coast of
the island has seen the most rainfall with 0.41 in of rain falling
over the last 24 hrs. Rainfall has begun to intensify with heavy
amounts reported in the METAR in Kodiak City. The low has shifted
southward bringing more widespread rain to the rest of Kodiak
Island and the AKPen. Easterly moving short waves continue to
pass over Southcentral Alaska. As they transit the region, they
continue to tighten up the pressure gradient and allow higher
winds to be noted across the eastern Kenai Peninsula, Barren
Islands and Kachemak Bay.

Looking to the west, the low that has been trailing the south side
of the Aleutians, combined with the jet stream, are bringing
higher winds to the Western Aleutians. The associated trough of
low pressure is making its way eastward as a ridge builds to the
west.

&&

.MODEL DISCUSSION...
Models are in good synoptic agreement for the first few days.
Minor details differences are met with the complex low pressure
system working through the Gulf. The overall picture remains the
same, with coastal rains and the usual areas seeing cross barrier
flow. Across the Bering, guidance also is in good agreement
through Saturday. The building ridge across the AKPen is well
handled, while timing and intensity differences exist with a low
dropping in from the Northwestern Pacific.

&&

.AVIATION...
PANC...VFR conditions. Gusty Southeast winds will continue over
the airport complex trough this evening.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
An upper level low situated over the Gulf of Alaska and the
Northern Pacific Ocean will continue to influence the weather over
Southcentral Alaska through the end of the work week. Several weak
waves will wrap around the upper low from east to west bringing
continued cloudy and wet conditions to the the Gulf Coast,
especially the Eastern Kenai Peninsula and Kodiak, which has taken
the brunt of the storm track so far this week.

For tonight, a lower end gale force low will continue tracking
west towards Kodiak bringing a quick shot of higher winds and
longer periods of precipitation before tracking further west and
dying out by tomorrow morning. There will be a brief break in the
cloud cover tonight and tomorrow north of the Gulf Coast leading
to noticeably colder overnight temps, while day time temps will
quickly rebound with abundant sunshine heating up the land. High
temps are expected to surpass 50 degrees for most inland
locations, with some spots in the southern Susitna Valley flirting
with the 60 degree mark, especially if the clouds stay at bay. By
Friday, another short wave wrapping around the top of the upper
level low will bring increased cloud cover to most of
Southcentral, keeping daytime temps a bit cooler than Thursday,
with another round of rain showers expected along the Gulf Coast
and into Kodiak.

&&

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

The continuation of the same general pattern remains in place this
evening as broad southeast flow aloft continues. Another shortwave
trough, moving from Kodiak into Bristol Bay this evening will
bring a round of light precipitation to Bristol Bay and the
Kuskokwim Delta. This low will rotate into the Bering Sea by
Thursday night with a general drying trend as weak northerly flow
and surface ridging develop over Southwest through Friday.

&&

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

Broad cyclonic flow and a remnant deformation zone over the
Eastern Aleutians will be the main story through Thursday. Showers
will be most prevalent over the Eastern Aleutians east of
Unalaska. Northwest winds will increase tonight and Thursday to as
high as 30 knots as a low moves into Bristol Bay. The next feature
of interest is a weak gale force front which moves into the
western Bering Sea Thursday night and Friday.

&&

.LONG TERM FORECAST (Days 3 through 7)...
Models are coming into agreement with upper level ridging over the
mainland and eastern Bering blocking the southerly progression of
an upper low tracking through the Bering Strait Friday, and
eventually tracking the ridge over the mainland and pushing the
upper low over the Gulf off to the southeast over the weekend.
This progression will allow a broad upper level trough to track
through the Bering through Monday, followed by another upper level
low tracking into the Bering on Tuesday. This ridging and
offshore flow pattern will likely keep much of the Mainland
protected from activity from the Bering through Tuesday, but
possibility not much longer into the week as the Bering trough
continues to deepen and progress eastward. If this trend
continues, active weather would begin to shift from the Bering
into the southern Mainland for the remainder of next week.

The EC and GEM have been consistent in keeping the bulk of the
energy and (more importantly) cold air well north of the area in
the Eastern Interior and the Yukon. As a result confidence is
beginning to improve that temperatures will stay generally near
normal with weak ridging in the area and little in the way of
significant precipitation chances for much of the South Mainland
through Tuesday. The one area where the EC seems to be the outlier
is with regards to a small closed upper low tracking through the
Copper River Basin and into the northern Gulf coast area
Sunday night into Monday. Chances for precipitation increase from
Tuesday onward as the Bering low and associated front push
further northeastward.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...None.

&&

SYNOPSIS AND MODEL DISCUSSION...SS
SOUTHCENTRAL ALASKA...KVP
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA
LONG TERM...TP