High Wind Watch 4, NWS Anchorage, AK

650 
WWAK72 PAFC 010625
NPWALU

URGENT - WEATHER MESSAGE
National Weather Service Anchorage AK
1025 PM AKDT Sun Sep 30 2018

AKZ191-020015-
/O.UPG.PAFC.HW.A.0004.181001T2100Z-181002T0600Z/
/O.NEW.PAFC.HW.W.0006.181001T2100Z-181002T0600Z/
Western Aleutians-
Including the city of Shemya and Amchitka
1025 PM AKDT Sun Sep 30 2018

...HIGH WIND WARNING IN EFFECT FROM 1 PM TO 10 PM AKDT MONDAY FOR
THE WESTERN ALEUTIANS...

The National Weather Service in Anchorage has issued a High Wind
Warning, which is in effect from 1 PM to 10 PM AKDT Monday. The
High Wind Watch is no longer in effect. 

* WIND...South wind 25 to 35 mph increasing to 65 mph in the
  afternoon with gusts up to 80 mph. 

* TIMING...Monday afternoon through Monday evening.

* IMPACTS...High winds may move loose debris and may damage 
  property. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A high wind warning means a hazardous high wind event is expected
or occurring. People are urged to secure loose objects that could
be blown around or damaged by the wind.

&&

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
454 AM AKDT Sun Sep 30 2018

.ANALYSIS AND UPPER LEVELS...

A ridge of high pressure remains parked over the state today,
continuing the trend for fair weather across much of the Mainland.
The area of low pressure responsible for the gusty southeasterly
winds across the central and eastern Aleutians yesterday has now
moved into the northwestern Bering. A strong gradient between the
high over the mainland and the low pressure over the Bering Sea
is maintaining the strong south to southeast wind along the Bering
Sea coast and over the eastern Bering Sea. An upper level North
Pacific low is currently situated just south of Dutch Harbor. The
leading front associated with this low will continue to bring
southeasterly winds along the eastern Aleutians and AKPEN. Radar
imagery this morning indicates rain and low level stratus and fog
along the coastal areas of Southwest Alaska as the front
approaches.

&&

.MODEL DISCUSSION...

Overall, models remain in good synoptic agreement through the next
48 hours. Differences arise by Tue morning as the remnants of
typhoon Trami enter the western Bering. Models currently agree on
the phasing of the upper level low currently south of Dutch
Harbor with the upper level remnants of Trami beginning Mon
evening over the central Bering. At this time, the GFS/EC solution
shows a slightly faster track while the NAM keeps the low further
west. With large uncertainties in timing and position, GFS was
still preferred with this morning's forecast package.

&&

.AVIATION...
The main issue will be with the potential for stratus and fog
this morning and again overnight tonight. The latest satellite
imagery (nighttime microphysics) did not show any stratus in the
northern Inlet, although that was from around 1030Z. At this
point we will stick some IFR Cigs and Vsby in for this morning
then VCFG for the late night and morning hours again tonight and
Mon morning, though generally keeping the prevailing conditions
VFR with light wind.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...

High pressure will continue to dominate the weather over the
region for the next two days with the only exception being Kodiak
which will see a front move over that area tomorrow. With the high
pressure, the only real question will be the development of fog.
A nighttime microphysics pass from the VIIRS satellite taken
around 2:30 AM AKDT shows the development of fog in the river
valleys of the eastern Kenai Peninsula, eastern Turnagain Arm, as
well as in the Eagle River and Eklutna River valleys. The Copper
River Basin, which had some extensive fog and stratus yesterday is
almost completely clear of fog at this time. Fog should overall
be less than yesterday, with some areas developing again Sunday
night into Monday morning. Temperatures will remain well above
normal today and tomorrow for most of southcentral Alaska with a
cooling trend back toward normal after that.

A front will move over Kodiak Island from the southwest tomorrow
and bring back rain to the area as well as strong southeast
winds. This front will then slowly progress northward through
Tuesday.

&&

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

Winds will remain the focus across Southwest Alaska through
Monday as a tight pressure gradient lingers over the region. The
gradient is the result of a stationary ridge situated downstream
in the northern Gulf and a trough upstream extending across the
eastern Bering. As the next surface low begins to track northeast
toward the AKPEN today, the gradient will tighten and the
southeasterly winds will increase, especially across Bristol Bay
and the Kuskokwim Delta with the highest speeds along the coasts.
Scattered showers will also develop along the coast later today
and continue through Monday as the low dissipates and transitions
to an open wave. For upslope areas of the AKPEN, the persistent
southerly flow will bring periods of moderate to heavy rain. Any
lingering showers from the now dissipating trough will move inland
on Tuesday as an occluded front extending from a strong storm
system over the western Bering advances toward the Southwest with
another shot of rain and gusty southerly winds.

&&

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

A low well south of Atka will move toward Dutch Harbor today. The
rain and gusty southeasterly winds that developed overnight across
the eastern Bering will continue through early Monday before
diminishing as the low tracks north and fills in. Over the
central Bering, gusty northerly flow will increase tonight around
the back side of the low passing to the south and east. Then all
eyes turn to the remnants of typhoon Trami as it tracks quickly
toward the western Aleutians. This system will transition to a
powerful extratropical storm as it taps into a cold air mass over
the Kamchatka Peninsula. Storm-force winds will move over Shemya
and Attu Monday as its associated front sweeps across the western
Aleutians. There is still some uncertainty as to the exact track
of this low once it passes west of Attu; however, current guidance
continues to place the center of circulation well north and west
of the Aleutians. If this trend holds, it is looking more likely
that the core of strongest winds associated with the colder air
wrapping underneath the low will remain over the open waters of
the western and central Bering through Tuesday where gusts could
approach 70 kts.

&&

.LONG TERM FORECAST (Days 3 through 7)...
(Wednesday through Saturday)

A very unsettled pattern will persist for the middle to latter
part of the week, as the remnants of the former Super Typhoon
Trami, which is currently near Japan, move northeast towards the
western Bering Sea. It is expected to then turn eastward as it
merges with a trough coming off the Kamchatka Peninsula. The
numerical models all agree in this scenario, but they differ in
speed and strength as the system bumps into a persistent ridge
stretching from the North Slope through the Kenai Peninsula, and
into the Gulf. Initially, the models are in good agreement with
the pattern aloft on Wednesday, but they quickly begin to diverge
some 24 hours later, as the GFS looks to have a faster progression
with the system as the ridge slides off to the east while
weakening.

This storm will be unusually strong for the Bering Sea for this
time of year, as it will be 3 to 4 standard deviations above
normal. Most of the region along and north of the western
Aleutians will see storm force winds with hurricane force gusts
likely. An associated occluded front will cross into southwestern
parts of the state by evening, with widespread rainfall
accompanying it, with another low developing near Kodiak. This
rainfall will also spread northeast during the evening and into
Thursday for most of Southcentral and the Kenai/Prince William
Sound region.

Meanwhile, another north Pacific low will strengthen as it
crosses the central portions of the chain, lifting north towards
Saint Matthew Island on Friday, while sending another front
through the southwest with more rainfall developing. Similar to
its predecessor, another Kodiak low will form Friday evening,
reaching Prince William Sound late Saturday, spreading widespread
rainfall across all of Southcentral and into the Copper River
Basin. However, it's important to note that as we approach next
weekend, model diversity increases somewhat, which is typical
given its 5 to 7 days out. Added to the mix is that everything is
dependent on if the models handle the first extra-tropical system
correctly, so forecast changes are probable for the latter half
of the week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gale 150-170 172 174 177 180 181.
		 Storm 178.

&&

SYNOPSIS AND MODEL DISCUSSION...KO/SA
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...TM
LONG TERM...PD