Small Craft Advisory 566, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
405 PM AKDT Tue Aug 1 2017

.ANALYSIS AND UPPER LEVELS...
Satellite imagery shows a low just to the north of the western
Bering Sea. This low will impact much of the forecast region over
the short term. Meanwhile, a front has been bringing steady rain
across the Kuskokwim Delta as it pushes eastward. A much weaker
front is bringing rain to portions of the north Gulf coast and is
gradually pushing inland.

&&

.MODEL DISCUSSION...
Models are in generally good agreement in the short term as a low
currently in the western Bering pushes rapidly to the Kuskokwim
Delta over the next two days. There is some disagreement among the
models in the intensity of the upper level forcing for rainfall
over the Anchorage Bowl and western Kenai Peninsula Wednesday
afternoon and evening. In contrast, all models still indicate
steady rain across the Susitna valley for much of the day.

&&

.AVIATION...
PANC...VFR conditions will persist. Southerly winds will diminish
tonight, then increase again Wednesday afternoon. Some light rain
is expected beginning Wednesday afternoon.

&&
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Cloudier skies and cooler temperatures will continue filtering
in this evening as a system over the Gulf and incoming upper level
shortwave from the Southwest begin to impact the region. Rain
showers will continue developing along the North Gulf Coast this
evening, while areas of Southcentral should remain mostly dry
until Wednesday morning as the shortwave approaches. The models
have all trended further north and weaker with the track of this
shortwave, so it now appears that the best chance for widespread
wetting rains should occur from Anchorage northward into the
Susitna Valley, while areas further south including the Kenai
Peninsula should see more spotty coverage. Afterwards on Thursday,
high pressure building northward from the Gulf will help push most
of the rainfall into the western Susitna Valley with only scattered
showers expected over most of the area.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
There are several upper level shortwaves moving from west to east
across the Southwest Alaska region accompanied by wetting rains
through the Thursday time-frame. One shortwave is pushing through
the Kuskokwim Delta eastward this evening, and the next shortwave
looks to track through the aforementioned region by midnight
tonight. By Wednesday afternoon a frontal boundary approaches the
Kuskokwim Delta coastline before spreading inland into the Southwest
Alaska region. This brings continued wetting rains to the
Kuskokwim Delta before spreading eastward into the Lower
Kuskokwim Valley, and the Bristol Bay area through Thursday.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The Western Aleutians/Bering has a 1007 mb low pressure system
just northeast of Shemya bring gusty southerly winds ahead of this
system. The associated weather front is draped through the Central
Aleutians/Bering this evening before tracking to the Eastern
Aleutians/Bering Sea by Wednesday afternoon. This synoptic feature
will bring gusty southerly winds out ahead of the low pressure.
Look for westerly winds on the backside of this system covering
the majority of the Bering/Aleutians. This develops into a showery
weather regime as we head into Thursday, and with marine layer
stratus/fog developing again over the Western Aleutians/Bering.

&&

.LONG TERM FORECAST (Days 3 through 7)...
The end of the week will first be characterized by high pressure
over the Gulf that will extend over Southcentral Alaska and
troughing to the west that will bring rain to the Eastern
Aleutians and southwest Alaska. This pattern will hold into the
weekend but will shift with a low moving south of the Alaska
Peninsula and ridging building in over the Bering and Aleutians by
Sunday. This will leave southern Alaska in unstable conditions
for early next week with afternoon convection possible.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EN
SOUTHCENTRAL ALASKA...DEK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PD
LONG TERM...DK