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295
FXAK69 PAFG 252136
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
136 PM AKDT Sat Mar 25 2017

.DISCUSSION...
The 12z model suite initialized well against the 12 surface
analysis and verified well against the 18z surface analysis. The
12z model suite continues to be in good agreement with previous
model run output as well a displaying minimal spread between mode
families in the short range as well as the mid range. Model spread
increases significantly by the end of the week.

Aloft at 500 hpa, a longwave trough currently over eastern and
central Alaska combined with a 500 hpa ridge currently over the
eastern Bering Sea will slowly retrograde to the west through the
upcoming week with the upper level trough moving over western
Alaska and the upper level ridge moving over the western Bering
Sea by late in the week. Weak southerly flow develops over eastern
and central Alaska by mid week and bringing warmer temperatures
to to areas that have had over three weeks of below normal
temperatures. Temperatures are expected to reach freezing by
around Wednesday or Thursday of next week for the first time in
the month of March in Fairbanks. The warmer and moist south to
southeast flow will bring the threat of light snow over the
eastern and central interior by mid week as week overunning flow
develops. Only minor snow accumulations are expected with this
system.

Areas of dense fog continue to move in and out of locations along
the the west coast under stable high pressure and will likely
continue through tonight. Reduced visibilities in blowing snow
will continue today along the north slope but will improve late
tonight as winds diminish.


&&

.AFG WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

CCC MAR 17



000
FXAK68 PAFC 260115
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
515 PM AKDT Sat Mar 25 2017

.ANALYSIS AND UPPER LEVELS...
At the surface the dominant high pressure remains over the
northern Bering Sea extending across interior Alaska. A strong low
and the associated gale force front extends along the Aleutians
to south of the Alaska Peninsula. An inverted trough extends from
the low over the panhandle to the North Gulf Coast. Aloft we
remain under the omega block as we have an upper low south of the
western Aleutians with the upper ridge extending from the north
Pacific across the western Alaska Peninsula into the Bering Sea
and the upper trough that extends from the Arctic low across the
mainland into the Gulf of Alaska.

The east flow along the North Gulf Coast is rotating showers
along the coast. Off shore flow and dry conditions persist across
south central Alaska to southwest Alaska. The stalled front along
the Aleutians is holding the gale force winds across the region
while keeping temperatures warm enough to keep the precipitation
liquid west of Unalaska.

&&

.MODEL DISCUSSION...
The models remain in generally good agreement in the short term
but continue to struggle with the placement of the low and
westward extend of the precipitation Monday night and Tuesday. We
have high confidence that snow will spread across Prince William
Sound beginning Sunday night, however, the models have been
limiting the westward extent of the precip area each successive
run for the past couple of days, thus lowering our confidence in
snow on the Cook Inlet side of the Kenai Peninsula.

&&

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

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
The Southcentral Alaska region remains under the influence of
an upper level trough. This synoptic feature will gradually swing
through the region, and is reflected at the surface with a weak
low pressure system in the northern Gulf. Therefore, look for a
showery regime with precipitation mainly along the northern Gulf
coastal communities. By Monday the aforementioned low pressure
system will have dissipated, but a 993 mb low in the lower
southeastern Gulf will start to track to the northern Gulf. By
Monday evening, the models have this system tracking onshore near
Seward. This feature bring snow showers to the Eastern Kenai
Peninsula, and the Prince William Sound region. Look for the
Anchorage Bowl to have a chance for snowfall to spill- over the
Chugach Mountains into the Bowl.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
Much of the same is in store for the Mainland for the next couple
days. The only real change in the overall pattern comes on Monday
morning when the Bering Sea blocking high retreats enough to allow
the upper trough back over the area, bringing some slightly colder
air with it. From a sensible weather perspective, not much will
change. Dry and clear conditions will continue with generally
light northerly winds. Expect some stronger winds and gusts during
the daylight hours. Temperatures will remain below normal,
especially at night as the clear sky promotes much cooler
temperatures, mainly in protected valleys.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
A decaying frontal boundary will remain in place for the next two
days. Light rain can be expected from Shemya through Atka as
easterly winds begin to relax. A new low pressure system will
bring a gale-force front south of the central Aleutians Sunday
afternoon. Currently it doesn`t look like the front will spread
over the chain. Otherwise general moderate easterly to
northeasterly can be expected over the Bering Sea.

&&

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

Little change to the longer range forecast for most of the region.
By the day three timeframe, guidance is still in agreement that a
surface low will spin into the Gulf as an upper level wave rides
south from the interior. Coastal locations will see precipitation,
but the question remains on the Anchorage area and how good of a
chance there will be for snow in the area. As each day passes
confidence increases and there is a decent chance that the
Anchorage will see some snowfall into Tuesday.

At this time, confidence remains too low to go any higher than a
chance of snow or to think about totals. The bottom line is that
the pattern is changing. The longwave pattern undergoes a bit of a
shift following this early week system and will set us up to be
in a little bit of a favorable patter to see systems beyond the
forecast timeframe reaching all of south central.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Gale 155 172-175 178.
Heavy Freezing Spray 139 179 185.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...SA
SOUTHCENTRAL ALASKA...PD
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MTL
LONG TERM...SS


000
FXAK67 PAJK 252317
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
317 PM AKDT Sat Mar 25 2017

.SHORT TERM...An upper trof will remain over the gulf through Sun.
A developing low SW of Haida Gwaii will move N to the far SE gulf
by late Sun afternoon. An occluded front will move N into the SE
gulf and southern panhandle Sun.

Main forecast concerns will be precip potential/ptype/amounts, and
winds. Scattered to locally numerous showers are over the eastern
gulf and much of SE AK late this afternoon. The showers will
decrease from the S this evening, with the far N area getting out
of the showers by Sun morning as low level flow becomes more
offshore ahead of approaching low and front. However, steadier
precip with the front will move into the S late tonight then try
to move further N Sun, but the offshore flow will tend to break
up the precip area as it reaches the N half. E mtn slopes will be
favored for precip over the S and central areas especially closer
to the outer coast. The N should dry out Sun afternoon although
there could be a few sprinkles around the Icy Strait area.

Ptype will be mainly diurnally driven. Warm boundary layer temps
in the afternoon will generally mean rain or a mix, except in the
heaviest showers where more snow may occur. As temps cool
tonight, precip will become more snow especially over the N half
of the area. Then on Sun, any snow should be mostly during the
early morning before temps warm well above freezing. Snowfall will
be highest around Yakutat where more frequent snow showers could
lead to an inch or 2 of snow by late tonight. Elsewhere over the
N, snowfall should be an inch or less, with most places getting
little accumulation.

Winds will be increasing over the SE gulf later tonight and Sun
as occluded front moves in. Expect strongest winds over the far SE
gulf Sun afternoon where gales can be expected. Much of the
remaining E gulf from Cross Sound southward will see winds pick
up to 25-30 KT by Sun morning. Over the inner channels, winds will
become more offshore and increase later tonight, with SCA level
winds likely out of Cross sound and parts of Clarence Strait. Rest
of the area should see winds pick up to the 15-20 KT range by
late tonight and continue into Sun.

.LONG TERM...At upper levels southwesterly flow will last through
mid week with a low extending down from the AK interior and
ridging off the western CONUS. Surface low mentioned in the short
term will continue its northwesterly track across the AK gulf with
associated occluded front moving over the panhandle. The low will
weaken by the time it reaches Prince William Sound Monday
evening. Onshore flow will keep chance of precip over the
panhandle, mainly for the northern half as ridging moves over the
southern panhandle resulting in drier more spring like conditions.
Next waves begin to move into the gulf mid week with first low
tracking northeastward toward Prince William Sound followed by a
more significant low and front moving over the gulf Thursday
evening into Friday. Better chance of more significant rainfall
with this later front. Began a trend to raise low temps due to
more southerly flow later in the week which will likely begin a
transition to more rain than snow.

Still fair amount of model spread for the Sunday night into
Monday low. Used a blend of GFS/NAM with were in better alignment
but did shift the low center further to the west and north. For
later time periods ensembles were still in line with previous
forecast so little change was made. Positive precipitable water
anomaly and 850 mb temps with the late week system add to
likelihood of a more significant rain event. Forecast confidence
is average.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Gale Warning for PKZ041-042.
Small Craft Advisory for PKZ021-022-036-043-051.
&&

$$

RWT/PRB

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