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197
FXAK69 PAFG 232114
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
114 PM AKDT Sun Apr 23 2017

.DISCUSSION...
General model consistency with the upper level features through
Thursday with the upper level low moving eastward across the
Arctic with frontal feature moving northward across Interior
Alaska and extending towards Yukon Delta. A shortwave rotating
around the the upper level low near Adak will bring clouds and
precipitation to the Yukon Delta tonight as it spreads northward
toward Seward Peninsula by Tuesday.

Arctic Coast and Brooks Range: The main concern for the north
will be the dense fog that redevelops this evening into Monday
morning. Expect quarter mile visibility along the Arctic coast
line with areas of fog pushing up against the Brooks Range. Light
onshore flow will also continue across the Chukchi coast from
Point Lay up through Barrow with quarter mile visibility due to
the fog as well. However, fog should dissipate through the late
morning. There is a a low pressure trough in Eastern Chukchi Sea
that will move across the Chukchi Sea coast tonight and spread
across the Eastern North Slope area before dissipating. Stratus
along and west of this trough will spread east across the North
Slope tonight into Monday.

West Coast and western Interior: A frontal boundary will bring
isolated to scattered rain and snow showers tonight into Monday
across the Yukon Delta and Lower Yukon Valley. By Tuesday the
frontal boundary will move northward with scattered rain and snow
showers along and south of Seward Peninsula as showers also push
into the western Interior. Any precipitation accumulation will be
relatively light. It looks like it will remain colder for St
Lawrence Island for snow but will be rain along the west coast
during the day and evening with transition or mixture of rain and
snow overnight. Along the Northern Bering Sea and Bering Strait
the winds will remain from northeast with small craft and brisk
wind advisories extending from St Lawrence Island through Point
Hope. Although winds are not reaching strength for small craft
advisory in Norton Sound they are close. Expect the winds to
diminish in Norton Sound by Tuesday.

Central and eastern Interior: Mostly sunny skies across much of
the Interior with high clouds moving in from south. Continue to
have the warming trend through Monday. For Fairbanks, expecting
high temperatures in mid to upper 50s for Monday with overnight
lows around 30 Monday morning. The warming temperatures will allow
for the continued melt of area snowpack. Expect slightly cooler
temperatures across the Interior on Tuesday and Wednesday as a
weak front will bring increased cloud cover and at least a slight
chance for some rain or snow showers.The GFS and NAM bring much
more precipitation along the frontal boundary but likely a bit
overdone in the precipitation. Thus expect isolated showers
extending from Fort Yukon to Galena on Tuesday into Wednesday.

&&

.FIRE WEATHER...No red flag concerns. Dry and sunny conditions
will continue across the Interior today with only slight increase
of moisture for Monday. There will be an increase in moisture
resulting in increase in afternoon minimum RH values on Tuesday.
However, the gradual increase in downslope winds with southerly
flow and moisture will limit any precipitation in the Alaska Range
on Monday night into Tuesday.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory for PKZ210.

Brisk Wind Advisory for PKZ220-PKZ225.
&&

$$

APR 17



000
FXAK68 PAFC 240013
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
413 PM AKDT Sun Apr 23 2017

.ANALYSIS AND UPPER LEVELS...

An amplified ridge spreads from mainland Alaska southeastward
along the British Columbia Coast. While the ridge continues to
obstinately keep the Aleutian low from pushing too far east, an
upper level wave and weakening front are helping to bring in
clouds to much of the Southcentral mainland. However, there is
just enough perpendicular flow associated with this front, and
enough dry air in place at lower levels to limit precipitation.
Downsloping is also keeping places such as Iliamna dry and while
widespread mountain waves are evident across the Alaska Peninsula
in the IR satellite imagery. Meanwhile the low south of the
Central Aleutians continues to support unsettled weather across
the Bering.

&&

.MODEL DISCUSSION...
Models are in generally good agreement synoptically in the short
term, with some more evident divergence in the long term. In the
short term a blend of models was favored due to the strong
agreement, but the high resolution NAM was favored for local
effects in Southcentral.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist. Gusty
southeasterly Turnagain Arm winds are expected through this
evening and may develop again Monday afternoon.


&&

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

As high pressure continues to slide north this evening, a frontal
boundary currently draped across Kodiak Island will begin to shift
north and east into the northern Gulf of Alaska. This will bring a
period of light to moderate rainfall to most coastal locations
through Tuesday as rainfall upslopes along the coastal mountains.
Inland locations will be hard-pressed to see any rainfall as the
upper level pattern doesn`t seem conducive to drive the front
inland and weak cross barrier flow should keep the lowest pretty
dry. Some gusty winds will develop across Turnagain Arm, the Knik
River Valley and the Copper River as the front nears the coast
Monday and Tuesday but will likely remain below 30 mph. Temperatures
will continue to be slightly above normal with overnight low
temperatures ranging from the lower 30s to lower 40s and highs
generally in the mid 40s to mid 50s.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
Conditions will remain largely unchanged through the beginning of
the week as moist southeasterly flow persists over the southwest
mainland on the eastern periphery of the Bering Sea trough. This
will yield continued cloudy and showery conditions as temperatures
run above seasonal normal values. Showers will continue to favor
western portions of Bristol Bay including upslope areas along the
Kilbuck Mountains, while remaining lower in coverage through the
typical downslope areas in the lee of the Alaska/Aleutian ranges.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The Bering region will remain locked in a benign showery regime
for the next several days under the influence of broad cyclonic
flow as a sprawling, vertically stacked low remains quasi-
stationary in the vicinity of the Central Aleutians. Winds will
mainly be southeasterly over the eastern Bering and northeasterly
over the western Bering, while generally remaining below Small
Craft Advisory criteria. Widespread marine stratus and patchy fog
will also persist over much of the region as warmer air moves over
the relatively cold waters of the Bering.

&&

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

The long range forecast continues with a drier pattern inland as
low pressure centers spin across waters of the Gulf and Bering.
However...at the end of next week the synoptic pattern slowly
shifts as the Bering low lifts northeast. Next Friday and Saturday
the closed Bering low becomes an open wave over the southwest
with a trough axis swinging over Southcentral which will bring
increased chances for rain across the southern mainland.

The biggest challenge in the extended range surrounds the next
storm system for the western Bering as a low organizes in the
North Pacific. Model agreement is good with the initial timing of
the front, pushing into the western Aleutians late Thursday, but
they differ in the track and strength of the low as it progresses
east through Saturday. Overall, the main impacts of gale force
winds and rain are expected to remain over the Bering and
Aleutians.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...EN
SOUTHCENTRAL ALASKA...MC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
LONG TERM...KH


000
FXAK67 PAJK 232255
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
255 PM AKDT Sun Apr 23 2017

.SYNOPSIS...Broad area of low pressure centered along the central
Aleutians impacts the Gulf of Alaska with a trough extending over
gulf to the British Columbia coast. Higher pressure over northern
Canada will weaken as the center moves east towards Hudson Bay.


&&

.SHORT TERM.../ Sunday night to Tuesday night / An old trough
extending over the gulf and Haida Gwaii has clouds and light
rain/showers moving north and west across the southern panhandle
Sunday afternoon. Expect to see the light rain to continue to
work its way northward through the panhandle tonight. It isn`t
until during the early day Monday when the trough has moved north
to the northern gulf that PoP get more than low chance levels.
Winds over the northern coastal marine zones also increase up to
20 kt, as the through approaches.

Another short wave/surface will be developing and increasing in
strength as the feature moves east northeast of the Pacific
towards the Haida Gwaii region later Monday with a closed surface
low pattern go be about 200 nm southwest of the island midday
Tuesday. The operational models are generally agreeing on the
feature although have presently favored the more eastern/weaker
solution pair of the NAM/EC. The low should be curving north into
the southeast gulf west of Prince of Wales Island by early
Wednesday morning. This track and strength seems to be a new path
for the solutions from previous thinking, so blended into the
Wednesday forecast periods.

The new low will spread a new front north into the southern
panhandle and help to dry out the precipitation from the northern
areas Tuesday, and then that front will start to spread the rain
northward.

.LONG TERM.../Tuesday morning through Saturday/ Issued 5 am Sunday
- There is not much change in the overall synoptic pattern
through next week. The polar jet will remain over the central
Pacific and this will keep the storm track south of the forecast
area through mid week. There will be a stronger low pressure
system that will lift north out of the north Pacific on Wednesday
and move into the eastern gulf. There are some differences with
the track of this low but the latest few model runs seem to be
picking up on this feature. As the low slowly lifts northeast
through Thursday the threat of precip will increase for the
southern half of the forecast area. The northern areas right now
will see a chance of rain. For late week into the early next
weekend there is increased onshore flow from the southwest and
with that a chance of rain with cloudy skies seems likely.

Wind wise...the inner channels will see relatively light winds
from the north through Wednesday night with weak northernly
pressure gradient. As the low moves into the eastern gulf winds
will increase to 20 kt over marine waters with 15 mph over land
from Fredrick Sound south. The winds will come around to the
south late in the week as a ridge builds over the northern panhandle
as the low moves into Canada on Friday.

Overall there is average forecaster confidence for Tuesday and
Wednesday but lower confidence after that due to the differences
with the low moving out of the north Pacific and spread in the
ensembles. Changes in the long term were modified using the 00z
nam and 12z ec through day 4 then WPC for late in the week into
the weekend.

&&

.AVIATION...We began the periods with vcsh in the southern zones,
and only added change groups where ceilings fluctuated through the
night and into Monday. The northern sites we added evening change
groups as channel breezes fall and then even though vcsh may occur
late tonight, we delayed adding until mvmc conditions arrived
later Monday. No IMC conditions are forecast through the next 24
hours.

&&

.MARINE...Winds primarily 20 kt or lest through the part of next
week though will need to watch the low development Tuesday for
the southeast gulf. Seas and swells for the coastal areas 5 to 7
feet tonight and into Monday. A localized buoy is reporting 8
feet, however I suspect those will subside through the evening.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...None.

&&

$$

Bezenek/JWA/ABJ

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