Gale Warning 305, NWS Anchorage, AK

889 
FZAK62 PAFC 122339
OFFALU

OFFSHORE WATERS FORECAST
NATIONAL WEATHER SERVICE ANCHORAGE AK
339 PM AKDT FRI MAY 12 2017

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.

PKZ499-131245-
339 PM AKDT FRI MAY 12 2017
.SYNOPSIS FOR CENTRAL BERING SEA...
A 998 MB LOW NEAR 57N 171W WILL WEAKEN TO 1004 MB AND MOVE ONSHORE
NEAR 60N 162W ON SATURDAY. A WEAK RIDGE OF HIGH PRESSURE WILL
FOLLOW THIS LOW ACROSS THE BERING SEA ON SATURDAY AFTERNOON. EARLY
SUNDAY...WINDS WILL BECOME EASTERLY ACROSS THE SOUTHERN BERING AHEAD
OF A FRONT ACROSS THE CENTRAL ALEUTIANS THAT IS ATTACHED TO A 997MB 
LOW NEAR 47N 176E.

$$

PKZ411-131245-
BERING SEA OFFSHORE WEST OF 180 AND EAST OF THE INTERNATIONAL
DATELINE-
339 PM AKDT FRI MAY 12 2017

.TONIGHT...NE WIND 10 TO 15 KT. SEAS 6 FT.
.SAT...NE WIND 10 TO 15 KT. SEAS 6 FT.
.SAT NIGHT...NE WIND 10 TO 20 KT. SEAS 5 FT.
.SUN...NE WIND 10 TO 25 KT. SEAS 3 TO 6 FT.
.SUN NIGHT...NE WIND 10 TO 25 KT. SEAS 3 TO 7 FT.
.MON THROUGH WED...NW WIND 10 TO 25 KT. SEAS 3 TO 7 FT.

$$

PKZ412-131245-
BERING SEA OFFSHORE 171W TO 180 AND NORTH OF 56N-
339 PM AKDT FRI MAY 12 2017

.TONIGHT...NW WIND 10 TO 20 KT. SEAS 7 FT.
.SAT...NW WIND 10 TO 15 KT. SEAS 5 FT.
.SAT NIGHT...N WIND 10 KT. SEAS 4 FT.
.SUN...NE WIND UP TO 15 KT. SEAS 3 FT.
.SUN NIGHT...NE WIND UP TO 20 KT. SEAS 3 TO 5 FT.
.MON...NE WIND 10 TO 20 KT. SEAS 3 TO 6 FT.
.TUE THROUGH WED...N WIND 15 TO 25 KT. SEAS 4 TO 9 FT.

$$

PKZ413-131245-
BERING SEA OFFSHORE 171W TO 180 AND SOUTH OF 56N-
339 PM AKDT FRI MAY 12 2017

.TONIGHT...W WIND 10 TO 25 KT. SEAS 4 TO 9 FT.
.SAT...NE WIND UP TO 15 KT. SEAS 5 FT.
.SAT NIGHT...E WIND 10 TO 20 KT. SEAS 4 FT.
.SUN...E WIND 10 TO 25 KT. SEAS 3 TO 7 FT.
.SUN NIGHT...NE WIND 15 TO 25 KT. SEAS 5 TO 8 FT.
.MON...NE WIND 15 TO 25 KT. SEAS 7 FT.
.TUE THROUGH WED...NW WIND 15 TO 25 KT. SEAS 7 TO 10 FT.

$$

PKZ414-131245-
BERING SEA OFFSHORE EAST OF 171W-
339 PM AKDT FRI MAY 12 2017

.TONIGHT...SW WIND 15 TO 30 KT EXCEPT VARIABLE 20 KT N OF 57N. 
SEAS 9 TO 14 FT. PATCHY FOG.
.SAT...W WIND 10 TO 25 KT. SEAS 5 TO 10 FT.
.SAT NIGHT...NW WIND 10 TO 15 KT. SEAS 5 FT.
.SUN...E WIND UP TO 15 KT. SEAS 3 FT.
.SUN NIGHT...E WIND UP TO 20 KT. SEAS 3 TO 5 FT.
.MON...E WIND 10 TO 20 KT. SEAS 3 TO 6 FT.
.TUE THROUGH WED...N WIND UP TO 20 KT. SEAS 3 TO 7 FT.

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
426 PM AKDT Thu May 11 2017

.ANALYSIS AND UPPER LEVELS...
Cold air aloft along the weak upper level trough extending out of
the Gulf of Alaska into the Susitna Valley. This is also causing
the atmosphere to be less stable in the Cook Inlet region than the
past few days which will lead to convection this afternoon and
evening. Details on how this has changed are in the model discussion
section. Areas over the Gulf of Alaska are too stable at lower
levels to have any convective activity.

Southwest mainland Alaska is unstable enough for some showers over
higher terrain, but there is not enough lift to produce any
thunderstorms.

The large low in the Aleutians was producing storm force winds
earlier today, but should be weakening as it heads eastward.

&&

.MODEL DISCUSSION...
There are two takeaways from the models worth discussing. The
biggest one is the significant increase in instability forecasted
for today and tomorrow for the Susitna Valley southward through
the Kenai Peninsula. Yesterday's models had a small amount of
instability with higher values closer to the Talkeetna mountains
and the Copper River Basin. Today's 12Z and 18Z NAM shows a large
area of cape values 200 J/Kg or higher the whole swath from North
of Talkeetna to north of Homer, including the Anchorage and
Palmer/Wasilla areas. While GFS values are not quite as high
(which is typically the case), the pattern is the same and is
showing a much more unstable atmosphere over much of Southcentral
the next two days than was being indicated previously.

Models have also increased the winds around the low in the Bering
Sea and current forecasts reflect that increase in current and
projected wind speeds.

&&

.AVIATION...
PANC...The biggest question for this afternoon and evening
revolves around the potential for shower and isolated
thunderstorms to develop. The atmosphere is more unstable this
afternoon and convection will develop over the mountains. Steering
flow is weak, so believe these will remain over/near the
mountains.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
Showers and thunderstorms will again be a possibility this
evening for much of Southcentral as a nearly stationary upper
level trough remains overhead. Most of these showers should
develop along the mountains and then drift southward into the
lower elevations. The greatest risk for thunderstorms looks to
be with the strongest instability over the Talkeetna mountains
southward into the Matanuska Valley, as well as throughout the
Copper River Basin. Then on Friday the focus for thunderstorms
will shift northward into the Copper River Basin as a weakening
front moves into the Gulf. This front will remain well to the
Southcentral for Friday, which should allow for sunny and warm
day with temperatures rising well into 60's in most locations.
This period of warm weather will then break down this weekend as
an upper level trough approaches from the west. This system will
bring cooler/cloudier conditions to most areas for the upcoming
weekend with chances of rain mainly on Saturday.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
A pattern change is in store for the southwestern mainland. While
sunny skies and warm temperatures have dominated the region
today, satellite imagery currently indicates a front moving
eastward across the Alaska Peninsula. Although a fairly weak
front, it will bring showers to the southwest mainland coast, and
spread clouds further inland throughout the day on Friday. This
will help to keep temperatures lower across the region on Friday.
A low pressure system will approach the coast early Saturday
morning. This will increase the chance for showers across the
region Saturday as the low progresses further inland.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
A 975 mb low is currently centered near the central Aleutians
where it is supporting gusty winds and showers across the western
Aleutians. Its associated front stretches across the Bering Sea
towards the Alaska Peninsula. This low will continue to bring
light showers and gusty winds as it drifts toward Bristol Bay and
moves inland on early Saturday morning. High Pressure will build
into the western Bering behind this low. This will help to stall
a front across the western Aleutians that is associated with a
north Pacific Low.

&&

.LONG TERM FORECAST (Days 3 through 7)...
The upper-low and attendant surface trough will continue its
eastward progress through the weekend. Confidence is increasing as
the majority of the models converge on a solution that brings the
low center from the western Gulf Saturday night to the southeastern
Gulf Sunday night. As the low moves out of Southcentral Alaska, a
brief drying trend will begin Sunday morning over the Mainland as
offshore flow sets up behind the low and a ridge of high pressure
builds in the upper-levels. Meanwhile behind the ridge, the next
longwave trough will dig through the north central Pacific,
encompassing the Aleutians as the next work week begins. A series
of surface low pressure systems will develop within the longwave
trough south of the western and central Aleutians, with eastward
progress limited by the downstream ridge. The net result at the
surface will be a continuation of the showery conditions over the
Aleutians and southern Bering Sunday through Tuesday. The ridge
that will build in over the southern Mainland is progged to shift
east Monday evening, allowing for the surface lows and associated
fronts over the Aleutians to move to the southwest Mainland Monday
night. This will bring a return of widespread rain chances for
the Mainland starting Monday night and continuing through the
middle of the week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning 173 174 175 176 177.
FIRE WEATHER...NONE.

&&

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