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217
FXAK69 PAFG 221414 AAA
AFDAFG

Northern Alaska Forecast Discussion...UPDATED
National Weather Service Fairbanks AK
614 AM AKDT Mon May 22 2017

.DISCUSSION...
The models initialize well and are in good agreement in the short
term. An active pattern is expected for the upcoming week as
several systems move across the state.

Aloft, at 500 hpa, a 536 dam low currently situated near
Glennallen will move to near Eagle by this afternoon continuing
off to the northeast. A 523 dam low in the Chukchi Sea north of
Point Lay will remain roughly stationary today before moving off
to the northeast on Tuesday. A 514 dam low just east of the
Kamchatka Peninsula will push eastward over the next few days.
This low will push to just south of St. Lawrence Island by
Wednesday morning and will be over the west coast of Alaska by
early Thursday. This will bring much colder air aloft to western
Alaska as it approaches.

At the surface, A 998 mb low currently situated over Fairbanks
will track northward today and will be over Bettles by this
afternoon.

Central and Eastern Interior: Showers associated with the low are
expected today across the Interior, with the heaviest
precipitation falling right near the low center as it moves north.
Some areas north of Fairbanks could see a quarter to a half an
inch of rain today. Some morning snow mixing with rain is possible
along the Denali Park Road in places such as the Eielson Visitor
Center; however, any snow accumulation this morning along the park
road will be generally under an inch. Gusty southerly winds
expected today in the Eastern Alaska Range. A wind advisory has
been issued though this afternoon. Winds will die down the passes
this evening as the wind direction changes to become more
southwesterly. Cloud cover today will help to limit the potential
for thunderstorms today across much of the Interior. Scattered
showers will be seen across the Interior on Tuesday. A weather
front associated with a low in the Bering Sea will push across the
Interior Wednesday afternoon into Thursday. The models disagree
on some of the details; however, it looks like there is the
potential for a good soaking rain, particularly for areas west of
Fairbanks. This system will likely bring a couple of inches of
snow to areas along the park road in Denali National Park, such as
the Eielson Visitor Center. The cloudy skies and unsettled
conditions across the Interior will help to keep high temperatures
below normal this week.

West Coast and Western Interior: A strong upper level low pushing
eastward bring cold air aloft to western Alaska this week. This
will cause snow levels in the western half of the state to drop
significantly. By Wednesday snow levels will drop below 1000 feet
for some areas on the coast as well as on the Seward Peninsula. A
series of fronts will move around the low Tuesday and Wednesday
bringing precipitation to most of the West Coast and Western
Interior. The models differ some in QPF values as well as
exact placement of the heaviest precipitation; however, current
thinking is that many locations in the Western Interior could see
a quarter to a half inch of rain on Wednesday. Unsettled and
showery conditions will persist through the remainder of the week
as the upper level low remains parked over the Bering Sea. Below
normal maximum temperatures are expected this week

North Slope and Brooks Range: Some light snow showers today,
particularly west of Barrow. Chances for snow increase later in
the week particularly on Wednesday. There is the potential for
some decent accumulations in the higher elevations of the Brooks
Range with lesser accumulations in the passes; however, the models
differ on the details.

&&

.FIRE WEATHER...
A generally wet pattern is expected this week for most of northern
Alaska. This will limit fire weather concerns.

&&

.HYDROLOGY...
No known river issues at this time. North Slope starting to see
meltwater moving down rivers but seems to be contained within
riverbeds at this time and lacking a rapid warm up in the near
future expect this to remain the same.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Wind Advisory for AKZ223-AKZ226.
&&

$$

May 17



000
FXAK68 PAFC 221242
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
442 AM AKDT Mon May 22 2017

.ANALYSIS AND UPPER LEVELS...
A very dynamic pattern is on deck with broad troughing influencing
much of the region and sustaining two distinct systems. First,
there is a decaying occluded front that has pushed into the Kenai
Peninsula bringing a precipitation shield from Cook Inlet to
Cordova. Second, there is a mature cyclone impacting the western
Aleutians which has strong jet support.

&&

.MODEL DISCUSSION...
Good model consensus for the ensuing 96 hour forecast period as a
series of storms impact the region. The main event will be a
well-organized storm moves across the Aleutians and into
southcentral AK bringing a widespread batch of unsettled weather.
This is a high confidence event. The primary forecast challenge
will most likely prove to be the QPF.

&&

.AVIATION...

PANC...The remnants of a frontal boundary will bring rain and
reduced ceilings to PANC. The primary forecast challenge will be
pin-pointing the timing of the changes in cigs. Winds are
projected to be southerly today.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...
A brief break from steadier rain today and Tuesday with showers
before rain once again comes back on Wednesday. The previous upper
low is now pushing into the Interior. Lingering cold air aloft,
some clearing of clouds/surface heating today, and convergence
around Turnagain Arm will keep isolated to scattered showers in
the forecast. A weak trough also slides overhead tonight, so
we won`t likely be completely dry, but the widespread rain will be
over. As we lose clouds and wind Tuesday morning, recent low-
level moisture could promote fog development around Cook Inlet.
I`d like to see a bit more ridging aloft and subsidence, but
moisture and slack flow should be enough for patchy stuff.

Tuesday should be mostly dry, but middle and high clouds will
quickly be rolling in ahead of a pattern change for mid-week. A
strong jet stream will punch in from the west, bringing load of
moisture with it. Expect a return of steady rain and even some
wind on Wednesday.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
The weak frontal system along the coast will continue to shear
apart today as most of the energy from the associated upper level
trough crosses the Alaska Peninsula and tracks away to east
across the Gulf. Showery conditions will continue across Southwest
Alaska this afternoon through tonight as the remnants of the
trough swing across southwest Alaska. The next incoming frontal
system will reach the coast early Tuesday morning followed by
a stronger and rather wet system Tuesday night and Wednesday.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The frontal system currently pushing through the western Aleutians
will continue east into the central Bering today and eastern
Bering tonight. A developing wave along the front further to the
south will swing into the central Aleutians tonight, continue
east across the eastern Aleutians and Alaska Peninsula Tuesday and
then cross Bristol Bay Tuesday afternoon and evening. The large
vertically stacked parent low will track across the western Bering
today and tonight, into the northern Bering Tuesday and continue
east to the Y-K Delta through Wednesday night.

&&

.LONG TERM FORECAST (Days 4 through 7)...An amplifying trough
digging through the Bering sea and Aleutian chain will continue to
shift eastward Wednesday morning, with a blocking ridge building
over the Gulf of Alaska slowing the eastward progression of the
trough. This will keep a steady supply of wet and windy conditions
over much of the southern mainland through the end of the week.
Models continue to come into better agreement with bringing this
unseasonably moist airmass (based on forecasted precipitable water
values) to mainland Alaska.

One of the biggest struggles in the extended forecast will be the
timing of when high pressure builds back into the gulf and if/when
showers over the southern Mainland tapper off. Latest model runs
suggest this wet pattern will begin to dissipate during the
Memorial Day weekend, as models remain firm on bringing the ridge
of high pressure over the Northern gulf. However, there still
remains some uncertainty as these models are showing a chance of
some showers making it over the ridge and into the cook inlet
region Sunday. If this ridge builds into the area stronger than
currently progged, there remains some potential to bring warmer
and drier conditions to Southcentral Alaska over the weekend and
into Monday. Given the current model discrepancies, forecast
confidence remains low in a completely warm and dry scenario.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 155 172 174.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...PJS
SOUTHCENTRAL ALASKA...ML
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR
LONG TERM...TP


000
FXAK67 PAJK 221356
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
556 AM AKDT Mon May 22 2017

.SHORT TERM...Yesterday`s front has split into two factions. The
northern half of the region is seeing numerous showers associated
with the remnant low center that moved inland near PWS last night.
Majority of these showers are occurring along the outer coast
near Pelican and northward to Yakutat. The southern half of the
region is seeing widespread rain with rates of moderate to heavy
at times. Both areas with precip falling has low clouds or fog
with visibility around 3 miles. The interesting part of the
panhandle is a small portion of the central panhandle encompassing
Juneau/Gustavus/Hoonah/Angoon/Sitka. These towns have had little
shower activity overnight and have more of a mid-level cloud deck.
The overall thinking is that some of the showers to the north
will shift south through the day or more will fill in from the
gulf, but at this point the POP is looking on the high end for
this gap.

Winds remain strong out of the south through Lynn Canal this
morning. These came up yesterday afternoon post front with Eldred
Rock at gale force and Skagway getting persistent gusts of
40-50mph. Downtown Haines and the Juneau airport are also seeing
gusty winds. Expect winds to gradually ease through the afternoon
as the pressure gradient slackens.

Tonight a new weak low center looks to track E-NE across the
southern gulf. Latest models have shifted the low a bit north as
it moves into the SE gulf. Have adjusted the pressure/wind forecast
accordingly using the ECMWF and GFS for their good agreement on
placement. Expect winds to become light most places overnight,
then turn out of the north on the north side of the low by Tuesday
morning. The low will help to keep showers going over the central
and southern panhandle through tonight, then take the showers
with it as it shifts E-SE through Tuesday afternoon. High pressure
will build over the gulf behind the low and increase the NWLY
flow, which tends to be a drying pattern for us.

.LONG TERM.../Wednesday through Sunday/ As of 10 pm Sunday. For
the start of the long range, at upper levels main features will
be high pressure ridge over the eastern gulf with a low north of
the Bering sea with associated trough extending over the
Aleutians. As the upper low begins to shift to the east the gulf
ridge will narrow and sharpen. By Friday the upper level trough
will have moved over the central gulf with the ridge axis now
moved over British Columbia. For the rest of the weekend uncertain
if a wave will form over the northeast gulf.

At the surface the high pressure ridge will remain over the gulf
through the week. Main difference between previous forecasts is
indications that the trough from the Bering sea low will move a
short wave into the north central gulf and this wave may ride
over the surface ridge and impact at least the northeast gulf, if
not the north central panhandle. At most thinking this would be
scattered to isolated showers mid week but may just move in mid
level cloud cover. As this wave dissipates, a return to high
pressure being the dominant feature. Will be watching for marine
layer formation under this gulf high.

The other trend for the long range is warming temperatures aloft,
with 850 mb temps reaching 8 to 10 C by the weekend. Have
continued to keep warm surface temps in the forecast, but with
uncertainty of marine layer formation have held off on getting
above the upper 60`s, however 70 and higher is not out of the
question. Did drop Yakutat temps a bit due to the incoming short
waves and onshore flow from ridge axis position.

Small craft winds on lee side of the ridge will diminish as the
axis moves east. Indication of tip jet formation near Cross Sound
and Cape Decision so keeping winds at least in the 15 to 20 kt
range for these locations. For rest of the inner channels not
expecting winds to be much more than 15 kt.

Used a blend of GFS/NAM, which were in good agreement for the mid
week wave in the northeast gulf. Tempered down any pops from these
models due to initial uncertainty. Otherwise forecast confidence
is average.

&&

.AVIATION...Precip continues across the panhandle and will
diminish slowly from N to S today. Some breaks in the clouds has
resulted in some patchy fog/low stratus this morning. Meanwhile,
across the N, strong winds will slowly diminish through the
morning. Precip will maintain MVMC/tempo IMC conditions across
the S through the day. Overall, a gradually improving trend across
the region today. Held off on including FG in TAFs attm, but will
need to consider the potential as skies break overnight into Tue.

&&


.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind until 1 PM AKDT this afternoon for AKZ018.
MARINE...Gale Warning for PKZ012.
Small Craft Advisory for PKZ013-022.
Small Craft Advisory due to Seas for PKZ041>043-051>053.

&&

$$

BC/Ferrin/PRB

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