Small Craft Advisory 376, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
311 PM AKDT Sun May 3 2020

.ANALYSIS AND UPPER LEVELS...
Weak surface lows and fronts, associated with broad westerly flow
aloft over the Gulf, moved westward and spread clouds across the
Gulf and Southcentral Alaska. Afternoon radar data showed
rain/showers spreading west across the Gulf Coast and to the Kenai
Peninsula. Locally gusty northeast winds were observed over the
Matanuska Valley. With the exception of a brief period of stratus
along the Delta coast this morning, much of Southwest Alaska has
fair skies with broad offshore flow. Cloudy conditions with areas
of showers/rain and patchy fog were evident across the Aleutians
and Bering Sea.

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.MODEL DISCUSSION...
Models are in generally good synoptic agreement. Adjustments due
to local wind effects across Southcentral will be the main
challenge.

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.AVIATION...
PANC...VFR conditions will persist into Monday afternoon. Ceiling
however may drop to around 5000 ft tonight with rain showers.
Gusty southeasterly winds are expected late Monday afternoon into
the evening.

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.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
A low in the northern Gulf has started to bring cloud cover
across the coastal regions and inland. An upper level easterly
wave will move across the Copper River Basin tonight and into the
Susitna Valley by tomorrow morning.

Chances for precipitation will increase with the propagation of
this wave through tomorrow. The abundance of precipitation will
fall in the higher elevations and across the coastal locations.
However, there is only a chance of rain for Anchorage due to the
downsloping associated with the southeasterly flow pattern.

Winds will increase along the Turnagain Arm, the Knik River Valley
and in the Copper River Basin with the passage of this feature.
Winds should diminish Monday night with calmer and drier
conditions becoming prevalent Tuesday.

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.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3):
Looking at the latest CIMSS Natural Color satellite image most of
SW AK is under clear skies which extends into Bristol Bay and
Kuskokwim Bay. Offshore flow will continue overnight. Above normal
temperatures will continue this forecast period and its very
feasible that portions of SW AK will reach 60 degrees Fahrenheit
this week. In the past 24 hrs, the minimum RH observed was 20
percent at Sleetmute and the inland locations varied from 27-35
percent with higher values of relative humidity observed along the
coastal communities. Monday the highlight will be an upper level
disturbance moving from east to west over SW AK, the combination
of instability and lift gives it a convective look. Isolated
thunderstorms are possible. As each run of the models come in, the
position and the orientation adjust a little but still confident
that the ingredients will be there for showers and isolated
thunderstorms Monday afternoon and evening.

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.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3):
A front is moving into the Western Aleutians, bringing gusty
winds, enhanced seas, and precipitation with it. This system is
going to move eastward and the surface low will dive south of the
chain Monday night. There is an interesting gradient that has set
up over the eastern Aleutians with the enhanced northerly flow
over the Eastern Bering, the high resolution models are pinging
into gusty winds in the breaks between the islands that make up
the eastern chain. By Tuesday night, the next gale force low will
be impacting the Western Aleutians.

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.MARINE (Days 3-5: Wednesday through Friday)...
Gulf of Alaska: Potential for small craft advisory level winds
across the North Gulf Coast on Wednesday afternoon increases in
confidence with better model agreement today before the next,
stronger system enters the Gulf on Thursday morning. The front
associated with a North Pacific low will spread across the Gulf
through Thursday afternoon, with the potential to bring sustained
gale force winds along with it. Models are hinting at a stronger
solution today than yesterday's model runs, which leads to higher
confidence of at least small craft advisory level winds persisting
across the Gulf and coastal waters through Friday.

Bering Sea: By Wednesday afternoon, models are in good agreement
that the active pattern over the western Bering will start to wind
down as a front continues to weaken over the central Aleutians
through early Thursday morning. Models are less certain heading
into Friday morning with timing and strength of the next system
that will enter the western Bering and Aleutians. The GFS is once
again the most aggressive model trying to bring gale force winds
to the region, while others remain a small craft advisory level.
This next system will bring a round of widespread precipitation
starting early Friday.

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.LONG TERM FORECAST (Days 4-7: Thursday through Monday)...
As the North Pacific low continues to lift northward in the Gulf
through the end of the week, a chance for rain showers will stay
in the forecast through the weekend for areas along the North Gulf
Coast. Chances for rain increase Thursday into Friday for Kodiak
Island and the Kenai Peninsula, northern areas of Southcentral
will see dry conditions while they are positioned under an upper
level ridge. This will help to keep above average temperatures in
the forecast through the start of next week.

Models are having more difficulty over Southwest Alaska as this
front moves towards the region. For now, kept a chance of rain
showers across interior Bristol Bay and the Alaska Peninsula from
Thursday afternoon through Friday to account for this
uncertainty. However, there is much better model agreement with
the next front approaching from the western Bering. This front is
on track to reach the Pribilofs late Saturday and the eastern
Aleutians by Sunday afternoon, which will bring the next round of
rain to these areas.

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.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Flood Warning 152 155.
 Flood Watch 155.
MARINE...Gale Warning 119.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...RC
SOUTHCENTRAL ALASKA...CK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PJS
MARINE/LONG TERM...AH