FXAK68 PAFC 161207
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
407 AM AKDT Sun Jun 16 2019
.ANALYSIS AND UPPER LEVELS...
Our upper level pattern continues to be defined by a large area of
low pressure to the south of our state. Over the past day, the low
has shifted northeast to be located in the western Gulf of Alaska,
south of Kodiak. The backside of this low continues to pull air from
the Arctic down through the Bering Sea which is merging into the
jet stream that is moving along the southern side of the low in the
gulf. This in turn is reinforcing the upper level synoptic low
and keeping our forecast area under the influence of low pressure.
In the upper levels and on the broad scale, models are in good
agreement through the short term. However, on the surface they
begin to struggle with low placement in the Gulf of Alaska by
Monday. Models are also struggling to pick up on easterly waves
embedded within the low pressure spinning in the gulf, as they
often do. This will make forecasting somewhat tricky for
southcentral AK, as it will be difficult to identify when and
where precipitation associated with these waves will move through.
PANC...VFR conditions will persist. Turnagain Arm winds are
expected to pick up again late tomorrow afternoon and possibly
bend over the airfield.
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The front that moved through the region yesterday has stalled out
and weakened along the Alaska Range. This has entrenched the area in
the new pattern which is keeping the region in moist and cooler
air and in easterly flow aloft. The easterly flow aloft will also
allow some upper level disturbances (easterly waves) to bring
periods of rainfall to the area through the first half of the
week. In general, the showery cool weather will continue for a
few more days.
.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...
A vertically stacked low south of the eastern Aleutians continues
to bring cloud cover and scattered showers to Southwest this
morning, a trend that will continue through early next week. As
the low decays, it will gradually move northeastward and
eventually spawn a triple point low over the Gulf by Monday
morning. Meanwhile, several upper level waves will move over
Southwest from the north, bringing warmer and relatively drier air
to the Middle Kuskokwim Valley and Kuskokwim Delta coast Monday
afternoon. This will enhance the opportunity for convection, thus
increasing chances for thunderstorms to form Monday afternoon and
evening over the Middle Kuskokwim Valley, Kuskokwim Delta, and
Kilbuck/Wood-Tikchik Mountains. By Tuesday, onshore flow will
allow for generally cooler temperatures.
.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...
A low south of the eastern Aleutians will weaken and move eastward
into the Gulf Monday. Northerly flow and generally calm conditions
will persist over the Bering through Monday. By Tuesday morning, a
front approaches the western Aleutians, bringing rain and
.MARINE (Days 3 through 5)...
Confidence is very high that there will be no gale force winds
from Tuesday through Thursday. It is indeed likely that winds and
seas will remain below Small Craft Advisory criteria.
.LONG TERM FORECAST (Days 4 through 7)...
The forecast period begins on Wednesday with a weak upper low
over western Alaska, and a weak upper high over the southern
mainland. Another weak upper low will be sitting over the western
Bering Sea. This pattern is expected to change very little. With
very weak flow aloft and in the lower levels, a relatively quiet
weather pattern is expected for the middle and later portions of
next week, with no significant events on the horizon. Temperatures
will generally be above normal, with some showers possible.
SYNOPSIS AND MODEL DISCUSSION...BJB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KO
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