Scientific Forecaster Discussion
fxak68 pafc 111349
Southcentral and southwest Alaska forecast discussion
National Weather Service Anchorage Alaska
449 am akst Mon Nov 11 2019
Analysis and upper levels...
High pressure continues to hold in Mainland Alaska while a gale force
low has moved into the Gulf of Alaska. The interaction between the
two has induced offshore flow, with gaps and passes along the
coast having the most elevated winds. This low is also sending a
weak boundary through southwest AK, bringing some light rain showers
to that region. A weak low spins in the Bering today and continues
to decay. It isn't doing much outside of producing some small
craft advisories for today. Generally quiet weather again today.
Models continue to perform well through the short term. With the
consistency they have been displaying, we can have above average
confidence in the forecast. The only issue continues to be
precipitation type in southwest AK, but this is a known
shortcoming of numerical models.
Panc...VFR conditions and light winds will persist.
Short term forecast southcentral Alaska (days 1 and 2)...
Higher pressure over the Mainland will keep general offshore flow
and generally dry conditions and locally gusty outflow and gap
winds through Tuesday. A northward advancing occluded front
approaching the southern Gulf of Alaska this morning will bring
easterly gales across much of the Gulf through this evening then
weaken overnight and Tuesday as the front shears apart. The brunt
of the rain with this system will fall across the Gulf waters and
Kodiak Island through Tuesday. The northern Gulf/Kenai Peninsula
will see increasing chances of precipitation Tuesday night with
the weakening front.
Short term forecast southwest Alaska (days 1 and 2)...
a front over the eastern Bering is heading toward southwest
Alaska and will make it to the coast by this afternoon. Ridging
over Mainland Alaska will work to stall the front along the coast
as it dissipates. The front will primarily bring rain to the
Kuskokwim Delta coast but there is a chance some snow and a slight
chance of freezing rain could mix in a little more inland.
Tuesday will see ridging take over keeping precipitation at Bay
until Tuesday night when a front will approach from the south.
This front will primarily bring rain to areas around Bristol Bay
with a chance of snow to inland locations.
Short term forecast Bering Sea/Aleutians (days 1 and 2)...
a low in the central Bering will keep cyclonic flow and rain
showers over the area as it tracks to the northwest and weakens
into Tuesday. A stronger system will approach the eastern
Aleutians from the North Pacific today, first bringing rain to
the islands this evening. It will continue to bring rain to the
eastern Aleutians and Alaska Peninsula through Tuesday. This
system will also bring strong winds to the area with storm force
winds expected south of the eastern Aleutians Tuesday morning.
Marine (days 3 through 5)...
the strong low south of the Alaska Peninsula will primarily bring
gale to Small Craft Advisory level winds Tuesday night and
Wednesday to the waters along the Aleutians, Alaska Peninsula,
southeastern Bering, Bristol Bay and Gulf of Alaska with the
stronger storm force winds most likely remaining to the south of
the area. With the low filling and weakening as it lifts north
into the general winds in the Gulf will likely remain 30 knots or
less for Thursday and Friday with potential gales isolated to
favored channeled terrain and possibly along the barrier jet
region of the northern Gulf coastal waters. For the Bering,
increasing northeasterly flow will bring the potential for gales
to the northern waters Wednesday through Friday with Small Craft
Advisory or less winds further to the south.
Long term forecast (days 3 through 7)...
by Wednesday, a large vertically stacked low containing tropical
remnants will be centered south of the Alaska Peninsula and
tracking slowly east around 50n. An associated frontal system with
a deep southerly moisture tap will stretch north across the
central and eastern Gulf to the northern Gulf Coast. A weakening
portion of the front will extend to the west across the Bristol
Bay area and southeastern Bering with additional wraps of the
occlusion south of the eastern Aleutians and Alaska Peninsula
closer to and encircling the main low. Further to the north, an
Arctic low over the northern Canada coast will extend a cold
trough over the northern half of Mainland Alaska with an upper
level ridge extending south through the Bering Strait across the
northeastern Bering to the Yukon-Kuskokwim Delta coast.
With colder low level interior air entrenched in the Copper River
Basin, A rather moist easterly wave being propelled by an Arctic
trough digging to the southwest across interior Alaska to the y-k
Delta Wednesday and Thursday will bring the potential for heavy
snow to the Copper River basin and far northern Susitna Valley
and rain to the remainder of southcentral. For southwest Alaska,
precipitation will spread in from the east across the Alaska Range
Thursday primarily in the form of rain over the southeastern
valleys and transitioning to snow to the west.
Thursday night into Friday, the cold upper level low will rotate
to the south into Bristol Bay while the steadily filling low south
of the western Gulf lifts north into the central Gulf. Surface
troughs in between these two systems will continue to track from
east to west across southcentral and into southwest Alaska. The
Gulf low will dissipate Friday night into Saturday leaving a front
stalled across the Kenai Peninsula and northern Gulf Coast while
the western upper level low tracks back onshore over the Kuskokwim
Delta with the accompanying cold air aloft spreading inland
across southwest Alaska.
A more active westerly storm track will push into the Aleutians
for the weekend with a series of developing lows tracking up the
the chain and into the Bering. This evolution will push the upper
low over southwest Alaska off to the northeast through Sunday and
then bring progressively strong storm systems in from the west
through early next week.
Marine...gales: 120 131 132 138 150 155 165 170 173 174 176 351