Storm Warning 103, NWS Anchorage, AK

273 
FZAK62 PAFC 062332
OFFALU

Offshore Waters Forecast
National Weather Service Anchorage AK
332 PM AKDT Tue Oct 6 2020

Offshore Waters Forecast for the Bering Sea

Wind forecasts reflect the predominant speed and direction
expected. Sea forecasts represent an average of the highest
one-third of the combined wind wave and swell height.

PKZ499-071300-
332 PM AKDT Tue Oct 6 2020
.SYNOPSIS FOR CENTRAL BERING SEA...

A 975 mb low near 56N 165E will move to 61N 176W at 966 mb Wed
afternoon and then remain nearly stationary and weaken to 972 mb
Thu afternoon. The front associated with this low will move from
the central Bering Sea Tue evening to the Southwest Alaska coast
Wed.

$$

PKZ411-071300-
Bering Sea Offshore West of 180 and East of the International
Dateline-
332 PM AKDT Tue Oct 6 2020

...GALE WARNING THROUGH WEDNESDAY NIGHT...

.TONIGHT...SW wind 25 to 40 kt. Seas 16 to 23 ft. Rain.
.WED...W wind 25 to 40 kt. Seas 16 to 24 ft. Rain.
.WED NIGHT...W wind 25 to 40 kt. Seas 14 to 22 ft. Rain.
.THU...NW wind 30 kt. Seas 15 to 19 ft.
.THU NIGHT...NW wind 20 to 30 kt. Seas 12 to 16 ft.
.FRI THROUGH SUN...NW wind 20 to 30 kt. Seas 9 to 15 ft.

$$

PKZ412-071300-
Bering Sea Offshore 171W to 180 and North of 56N-
332 PM AKDT Tue Oct 6 2020

...GALE WARNING THROUGH WEDNESDAY...

.TONIGHT...S wind 30 to 45 kt diminishing to 15 to 30 kt after
midnight. Seas 16 to 22 ft. Rain.
.WED...SW wind 20 to 35 kt. Seas 16 to 22 ft. Rain.
.WED NIGHT...W wind 15 to 30 kt. Seas 13 to 20 ft. Rain showers.
.THU...W wind 15 to 30 kt. Seas 13 to 18 ft.
.THU NIGHT...W wind 15 to 30 kt. Seas 10 to 18 ft.
.FRI...W wind 15 to 30 kt. Seas 9 to 14 ft.
.SAT THROUGH SUN...NW wind 15 to 25 kt. Seas 6 to 11 ft.

$$

PKZ413-071300-
Bering Sea Offshore 171W to 180 and South of 56N-
332 PM AKDT Tue Oct 6 2020

...GALE WARNING THROUGH WEDNESDAY NIGHT...

.TONIGHT...SW wind 30 to 45 kt. Seas 17 to 22 ft. Rain.
.WED...SW wind 30 to 40 kt. Seas 17 to 23 ft. Rain.
.WED NIGHT...W wind 30 to 40 kt. Seas 20 to 24 ft. Rain.
.THU...W wind 30 to 40 kt. Seas 17 to 22 ft.
.THU NIGHT...W wind 30 kt. Seas 17 ft.
.FRI THROUGH SUN...NW wind 15 to 30 kt. Seas 9 to 17 ft.

$$

PKZ414-071300-
Bering Sea Offshore East of 171W-
332 PM AKDT Tue Oct 6 2020

...GALE WARNING TONIGHT...

.TONIGHT...S wind 30 to 45 kt. Seas 11 to 19 ft. Rain.
.WED...SW wind 30 kt. Seas 13 to 18 ft.
.WED NIGHT...SW wind 15 to 30 kt. Seas 12 to 19 ft.
.THU...SW wind 15 to 30 kt. Seas 11 to 19 ft.
.THU NIGHT...SW wind 10 to 25 kt. Seas 10 to 17 ft.
.FRI...SW wind 15 to 30 kt. Seas 8 to 13 ft.
.SAT...E wind up to 15 kt. Seas 6 to 11 ft.
.SUN...NW wind 10 to 20 kt. Seas 4 to 8 ft.

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
515 PM AKDT Mon Oct 5 2020

.ANALYSIS AND UPPER LEVELS...

As seen on GOES-17 satellite, the low in the northeastern Gulf was
structured a little different this morning than expected at this
time yesterday. Instead of a secondary low developing near Prince
William Sound and being the main low, the low center near Yakutat
remained the stronger one. This caused the wrapped-up occluded
front to be farther east which resulted in rain over the Copper
River Basin (and snow in some passes) and clearing over the
Susitna Valley which then brought in freezing temperatures over a
good portion of that region this morning.

To the west of this low there is higher pressure and partial
clearing for Cook Inlet through the Kuskokwim Valley. The coastal
areas of Southwest Alaska remain susceptible to low clouds and
fog in the northwest flow.

The next Storm system can be seen entering the western Bering Sea
near Attu this afternoon. This storm will become the main one
that will impact the forecast area through the remainder of the
week.

&&

.MODEL DISCUSSION...
Models seem to have now caught up to the structure of the
northeast Gulf of Alaska low with the stronger low center being
farther to the east. This has been adjusted in the forecasts
which leaves the focus on the large low that will move into the
western Bering Sea tomorrow and then slowly move eastward. Models
are in good agreement with the movement of this low. The biggest
feature to watch will be the development of a triple point in the
vicinity of Kodiak Island Thursday. This is depicted on all the
major models, but there is some difference in how far east it will
develop and behave once it is in the Gulf of Alaska. There is a
bit of model spread on the placement on the low center in what
will be an elongated low. However, the models do have the low
trough in along the same northwest-to-southeast line so this
allows for a reasonable confidence in the forecast in spite of the
model differences.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Mon
afternoon through Thu afternoon)...

Weak cyclonic circulation remains in place along the northern Gulf
coast as the remnant low slowly dissipates. A broad upper level
trough in place over Southcentral will allow for scattered showers
to continue this evening across Prince William Sound and the
Copper River Basin. As cooler temperatures move in aloft, light
snowfall is likely across the higher terrain and elevated road
passes tonight. On Tuesday, conditions remain generally clear and
dry for much of the Susitna Valley and western Kenai Peninsula. A
weak low develops over the northern Gulf coast Tuesday morning,
keeping showers likely across Prince William Sound. By Tuesday
evening, an upper level shortwave moves in from the west, bringing
an increase in cloud cover and chances for precipitation over the
Susitna Valley for Wednesday. Toward the end of the week,
attention shifts to a large Bering low moving in from the west.
The leading front will approach the Southcentral area beginning
Wednesday afternoon, with southerly flow and rain expected across
Kodiak Island. As the front moves eastward, winds will strengthen
over the Gulf and precipitation will fill in across the northern
Gulf coast for Thursday.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3)...

Colder temperatures are in store for Southwest Alaska Tuesday as
brisk northwesterly flow will allow for cold Siberian air to reach
the area. 850mb temperatures will bottom out near -5C over the
Kuskokwim Delta early Tuesday morning. Due to this, overnight low
temperatures tonight will be colder than overnight low temperatures
last night. Patchy fog is expected tonight across the Kuskokwim
Delta and Bristol Bay due to light surface winds and little to no
dewpoint depressions. An occluded front (warm occlusion) will move
through the area on Wednesday. Due to there being cold air at the
onset of precipitation, a rain/snow mix is expected Tuesday night
into early Wednesday morning for the Kuskokwim Delta. However, the
warmer southwest winds behind the warm occlusion will allow for
the rain/snow mix to quickly change to rain Wednesday morning.
Higher elevations in the Kuskokwim, Ahklun and Kilbuck Mountains,
precipitation will remain as snow. With respect to the
placement/orientation of the front with respect to the 850mb
temperatures, a GFS/GEM blend was favored as the NAM showed a
significant cold bias compared to the rest of guidance. Thursday
will be a cloudy day with lingering showers throughout the area.
Temperatures will be slightly warmer on Thursday as the cold
Siberian air will have exited the region while southeasterly flow
prevailing.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3)...

A front will move into the western Bering/Aleutians this evening
and produce gale force south-southwesterly winds across the area.
Localized storm force winds are expected along the frontal
boundary across the western Bering/Aleutians tonight. The front
will continue to move eastward while gradually weakening on
Tuesday. Storm force winds are expected to cease Tuesday
afternoon, though gale force winds will continue. The front will
then move inland early Wednesday afternoon. Widespread gale force
west-northwesterly winds are expected behind the front across the
western and central Bering/Aleutians through Thursday. Seas will
build to 20-25ft during this time as these west-northwesterly gale
force winds will provide ample fetch for these seas to form. These
seas will also remain long in period. A GFS/GEM blend was favored
for the placement and orientation of the front as these solutions
showed a very high degree of consistency.

&&

.MARINE (Days 3 through 5: Thursday through Saturday)...

Bering/Aleutians

A low is expected to stall near Saint Matthew Island on Thursday.
Northerly and westerly gales are expected on its western and
southern sides, respectively. These will gradually weaken to sub-
gales through Friday.

Gulf of Alaska

Easterly gales are possible along the Gulf coast Thursday evening
under a front. Otherwise sub-gales and lower seas will persist
through the weekend.

&&

.LONG TERM FORECAST (Days 4 through 7: Thursday through
Sunday)...

An upper low will stall near Saint Matthew Island Thursday. The
associated broad surface low will bring widespread rain and gusty
winds to the entire Bering/Aleutians. It will slowly weaken and
again stall near Bristol Bay through the weekend. While there are
model discrepancies, all of them show generally northerly flow
and widespread showers continuing through the weekend. Farther
east, a weakening front will track across the Gulf Thursday
bringing gusty easterly winds along the coast. Both the GFS and
ECMWF indicate a stronger compact low tracking northward along
the Panhandle, though it appears to weaken as it approaches
Southcentral. These models remain in generally good agreement
through Sunday. Both show another low tracking well south in the
Gulf. The will not directly impact Southcentral, but will continue
to drive the overall showery pattern along the Gulf coast and
higher terrain in the Chugach Mountains. Temperatures are expected
to fall slightly into the weekend, however highs will remain
seasonal near 50.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Flood advisory 121.
MARINE...Storms 177 178 413.
         Gales 130 155 165 170 172-176 179-181 185 351 352
               411 412 414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...KO
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ED
MARINE/LONG TERM...AP