Scientific Forecaster Discussion
fxak68 pafc 221245
Southcentral and southwest Alaska forecast discussion
National Weather Service Anchorage Alaska
445 am akdt sun Sep 22 2019
Analysis and upper levels...
Currently an upper level trough over the eastern Gulf continues to
track east towards Southeast Alaska while broader weak troughing
persists over southcentral Alaska. A small but better defined
upper low is currently moving inland over the Yukon Kuskokwim
Delta with southwesterly flow persisting over the remainder of
southwest Alaska. A broad upper level trough extends over much of
the much of the Bering with another upper low centered just south
of the central Aleutians tracking to the east along with an
associated surface frontal system beginning to spin up and
While models remain in good larger scale synoptic agreement
through the short term, significant finer scale details regarding
the location and strength of potential triple point lows spinning
up in association with the low tracking from west to east from
just south of the Alaska Peninsula on Sunday and across the Gulf
Sunday night and Monday. Confidence is good for this overall
being a gale force system, however uncertainty is high regarding
if and where localized storm force winds might be possible.
panc...VFR conditions and light winds will persist.
Short term forecast southcentral Alaska (days 1 through 3)...
High pressure will be over the Cook Inlet area today with dry
conditions expected, although cloud cover will increase during the
day as a weak vort-Max in southwesterly flow aloft crosses the
area. Lingering moisture over Prince William Sound northward into
the Copper River valley will keep some showers over that area, and
these will generally be light. Another system will move into the
western Gulf tonight, and then race eastward across the Gulf on
Monday. Precipitation with this system will generally be confined
to the coast and coastal mountains, with dry but somewhat cloudy
conditions inland. The surface low associated with this system
will be fairly strong, with gale force winds over much of the
Gulf. An upper level trough will move into southcentral from the
west on Tuesday brining some showers into most of the area,
including inland locations.
Short term forecast southwest Alaska (days 1 and 2)...
Cloudy conditions and gusty winds remain across the Kuskokwim
Delta and Bristol Bay this morning, while the Kuskokwim valley has
seen near freezing temperatures with clear skies overnight. The
cloud cover and a few showers will remain across southwest Alaska
today as the low over the Aleutians progresses eastward towards
the Gulf. Gusty conditions will also be present in the greater
Bristol Bay region, which will diminish through Monday afternoon.
Monday will also see a decrease in the amount of shower activity
across the region, with temperatures in the mid to upper 50s. The
best chance for precipitation on Monday will be along the akpen,
with interior location remaining on the dry side. Slight ridging
will return early Tuesday over the southwest, before a shortwave
moves in over the Kuskokwim Delta on Tuesday afternoon. This will
lead to another shot of rain to the coast and moving inland
through the day.
Short term forecast Bering Sea/Aleutians (days 1 and 2)...
A low centered south of the central Aleutians this morning,
bringing Small Craft Advisory winds, will continue its trek
eastward over the eastern Bering and akpen this afternoon as winds
increase to gale force. Strong north-northwesterly winds will
even allow for some storm force wind gusts out of bays and passes
south of the chain, stretching from False Pass and King Cove to
Sand Point. Winds will begin to weaken through Monday afternoon as
the low moves into the Gulf for Tuesday.
Behind this low, strong westerly flow will move in over the
north-central and eastern Bering Tuesday morning, moving into
Bristol Bay by Wednesday morning as a weak surface low moves
across the region.
Over the western Bering and Aleutians, another strong system
moves into the area by Tuesday afternoon. This deep system could
possibly bring storm force winds as it moves eastward. There is
still uncertainty in the models as to how strong this system will
be, so stay tuned to future forecasts to see how this low plays
Marine (days 3 through 5)...
A tight pressure gradient will exist with an area of low pressure
in Prince William Sound butted against high pressure west of the
akpen. Confidence remains high that the Barren Islands area will
see gale force northwesterly winds Tuesday afternoon and into the
evening hours. Across the Bering, the remnants of typhoon ta pah
will be sliding north and near the Kamchatka peninsula. A strong
front will accompany this low and sweep across the the western
coastal and offshore zones. Early indications are that 12 to 15
mb pressure drops within a 3 hour period are possible. There is
high confidence that southerly storm force winds will accompany
this front (moving across Shemya Tuesday afternoon) through Attu,
become high end gales as it slides east. There is a lower chance
that winds could meet or exceed low end hurricane force. Resultant
seas with the front are expected to exceed 25 to 30 feet at the
Long term forecast (days 3 through 7)...
There is high confidence moving into the end of the week of high
pressure building in over Mainland Alaska. This pattern change
will help to clear out the rain that's been over the southern
Mainland. However, as the ridge axis tracks east through the
southern Mainland, the western side will see southwest flow and
rain returning. There is some disagreement amongst the models on
the timing of the movement of the ridge axis.
Marine...Gale Warning 119 131 132 138 150 155 160 165 170 171