Small Craft Advisory 194, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
351 PM AKST Sat Mar 9 2019

.ANALYSIS AND UPPER LEVELS...
A southwest to northeast oriented jet stream is nosing into the
central Gulf of Alaska with 150-180 knots of Pacific punch today.
A stacked low is spinning in the eastern Bering Sea, with a
shortwave moving over Bristol Bay with split upper flow driving
to the north at 60-70 knots.

At the surface, an occluded front is moving into coastal areas of
Bristol Bay and approaching the southern end of Kodiak Island. The
triple-point is south of 50N. Widespread blowing snow is found in
the Kuskokwim Delta north of Bethel. Wet snow is falling in the
northern Nushagak Valley.

A dying occluded front is moving toward the northeastern Gulf
coast creating rain, snow, and gusts over Prince William Sound.
Snow and rain was falling around Homer and over the Kenai
Mountains, with the front driving wind over the Chugach
mountains. A High Wind Warning is in place for the Anchorage Upper
Hillside and Turnagain Arm. Gusts by midday were in the 70mph+
range along the Seward Highway corridor between Anchorage and
Girdwood.

&&

.MODEL DISCUSSION...
Models were in good, general agreement this morning through the
short-term. Discrepancies did not show until the mid-range early
next week.

The main vorticity maximum will pass over Southcentral and Prince
William Sound Sunday morning helping to quiet gusty winds over
the region. However, the parent low will elongate from North to
South along the Southwest Alaska coastline continuing the general
Southwesterly flow into the Gulf of Alaska with increasing
Northerly flow over a larger portion of the Bering until Monday.

&&

.AVIATION...

PANC...VFR conditions are expected to persist through the forecast
period. The main issue will be gusty southeasterly winds this
afternoon through early Sunday morning. Winds are expected to peak
between 00z and 06z before gradually diminishing thereafter.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2: tonight
through Monday afternoon)...
A strong weather front, extending east from a storm complex over
the eastern Bering Sea to the western Gulf, will move north
tonight and end up across the Anchorage Bowl and North Gulf Coast
early Sunday morning before moving into the interior and
weakening. Storm force winds are expected on the leading edge of
the front as it heads across the Gulf waters tonight. Strong gap
flow through channeled terrain is also expected. The most notable
is along Turnagain Arm and Portage Valley where winds will be in
excess of 60 mph. Winds in these areas will peak overnight just
prior to frontal passage. Though the winds are expected to be much
lighter across Southcentral on Sunday and Monday, a secondary
through moving in will keep locally gusty winds across much of the
forecast area. Winds and general warm advection will keep
precipitation in general toward rain or a mix in most coastal
locations and lower elevations inland west of the Copper River
Basin. Models though are hinting a weak Southwest cold advection
moving up Cook Inlet Monday with a through which could push
precipitation types more toward a mix. Coastal areas will likely
see the brunt of precipitation with inland areas largely
downsloped through tonight. Conditions will become more showery
Sunday and Monday with an approaching trough and broad cyclonic
flow aloft.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
A powerful front moving across the region will continue to shift
east tonight, with diminishing east-southeast winds. The flow will
become more south-southwest with stratiform rain/snow becoming
more showery, but a continued mix of precipitation as slightly
cooler air wraps around the main low center. The main low center
moves east through Sunday, with the coldest air wrapping inland
and a changeover to all snow. However, the showery nature of the
precip will likely keep snowfall accumulations on the lighter side
with this low as it moves east.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
A strong gale force low currently centered just east of the
Pribilof Islands will slowly move inland through Sunday with a
broad cyclonic flow remaining over the entire Bering Sea. Cold air
advection showers will switch rain to snow showers by Sun night
over a majority of the Bering Sea as 850 temps drop below -7 to
-10C.

Another fast moving low will clip the Aleutian Chain Sunday night
through Monday night as it moves west to east. Expect a mix of
rain and snow with this low.

&&

.MARINE (Days 3 through 5)...
The main midterm system to keep an eye on from a marine
perspective will be the low tracking through the Gulf in the
Tuesday night and Wednesday time period. Widespread Gales are
looking quite likely accompanying its associated frontal system
with the possibility of localized storm force winds through
favorably oriented terrain gaps if the stronger model solutions
verify. Following that another system tracks north into the Gulf
in the Thursday or Friday time period. While this second low looks
to be weaker, confidence is low in the any details regarding it.
For the Bering, the weather pattern shifts to a quieter one, with
winds expected to remain at Small Craft Advisory levels or lower
from the middle to end of the week.

&&

.LONG TERM FORECAST (Days 3 through 7)...
By Monday afternoon, the upper level pattern will have progressed
to have an upper level trough stretching across the central and
northern Bering to an upper level low centered over western
Mainland Alaska with a second upper low south of the central
Aleutians in phase with the Bering trough. To the east, a flat
upper level ridge centered south of the Alaska Peninsula will be
building east into the western Gulf, with broad troughing
extending over the remainder of the Gulf and swinging into
southeast Alaska. Another weak upper level ridge will be centered
over eastern interior Alaska and the Yukon Territory. At the
surface, a low pressure system in the eastern Aleutians will push
east across the Alaska Peninsula Monday night with the associated
front then lifting north into Southwest Alaska Tuesday. Over south
central Alaska, a trough with an accompanying surface low around
the eastern Kenai Peninsula and Prince William Sound area will
weaken and lift away to the northeast with ridging building in
Tuesday.

A developing North Pacific low pressure system will tracking into
the southern Gulf late Tuesday, continuing north into the central
Gulf Wednesday morning. The associated frontal system will move
into the Gulf coastal regions Wednesday afternoon bringing strong
winds and abundant precipitation with it. The track of the
surface low will then turn more to the northwest heading toward
Kenai Peninsula Wednesday night and continuing inland Thursday.

Another developing frontal wave will track north in the southern
Gulf Thursday or Thursday night although there is still
significant model disagreement on both its timing and track. The
18Z GFS is fastest and furthest east solution, bringing it to the
northern Gulf coast by Friday while the 12Z EC brings a slower
and more diffuse low into the Southwest Gulf Friday and Friday
night where it stalls through Saturday. The 12Z Canadian also has
a further west solution although resolves two separate surface
lows. The first paralleling the GFS low, although tracking it
across Kodiak Island Thursday night and the second low moving
into the Southwest Gulf around Friday night more similar to the EC
solution although further north and a little faster with it.

As we move into the weekend, model consistency further deteriorates,
with the only agreement being a general west to east storm track
south of the Aleutian chain and a generally northerly storm track
up into the Gulf. Confidence in the details associated any of
these systems is extremely low.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Storm Warning 119 120.
 Gale Warning 125 129 130>132 139 141 150 155 165 170 172>180 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...DS
SOUTHCENTRAL ALASKA...RC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA
MARINE/LONG TERM...JR

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE ANCHORAGE AK
1019 PM AKST SAT MAR 9 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1000 PM     NON-TSTM WND GST UPPER DE ARMOUN         61.10N 149.71W
03/09/2019  M77 MPH          ANCHORAGE          AK   MESONET

            30 SUSTAINED, GUST TO 77 MPH.

0653 PM     NON-TSTM WND GST PATO                    60.78N 148.83W
03/09/2019  M78 MPH          ANCHORAGE          AK   ASOS

            SUSTAINED OF 32 MPH GUST TO 78 MPH. SNOWING
            AT THE TIME OF THE OBSERVATION.

0350 PM     NON-TSTM WND GST SEWARD HWY @ MCHUGH CRE 61.02N 149.73W
03/09/2019  M92 MPH          ANCHORAGE          AK   DEPT OF HIGHWAYS

            SUSTAINED 71 MPH GUST TO 92 MPH.

0226 PM     NON-TSTM WND GST UPPER POTTER VALLEY     61.06N 149.76W
03/09/2019  M81 MPH          ANCHORAGE          AK   MESONET

            34 MPH SUSTAINED, GUST TO 81 MPH.

0220 PM     NON-TSTM WND GST SEWARD HWY @ MCHUGH CRE 61.02N 149.74W
03/09/2019  M76 MPH          ANCHORAGE          AK   DEPT OF HIGHWAYS

            SUSTAINED OF 57 MPH.

&&