000
FXAK68 PAFC 211314
AFDAFC
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
514 AM AKDT Tue May 21 2024
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...
A weak upper level ridge that currently dominates the eastern
Gulf of Alaska and Eastern Alaska will continue to slowly drift to
the east as a deep and cold for the season upper level trough
over the Eastern Bering Sea and Western Alaska slowly progresses
to the east. An anchoring low in the trough currently near the
Pribilof Islands will weaken as it pushes northeast to be located
near Nunivak Island by Wednesday morning. The upper level low
will continue to weaken and elongate and will stretch from near
the Gulf of Anadyr south and east to near Kodiak Island by
Wednesday night.
Several shortwaves will rotate around the upper level low and will
bring periods of rain for the AKPen, Kodiak Island and
Southcentral through the day today and tonight. A front rotating
around the low currently located in the eastern Bering, will
push north of Kodiak Island later this morning and will push into
the southern Portions of the Kenai Peninsula this afternoon.
Expect widespread rain and snow over much of the area, with some
locations receiving heavier rates of precipitation at times on the
Eastern Kenai Peninsula and into Prince William Sound.
Southwesterly flow aloft will allow the Anchorage Bowl to get some
precipitation Tuesday afternoon as the front passes.
Additionally, a building pressure gradient across much of the
Chugach and Kenai Mountains will produce southerly gap winds near
the Kamishak Gap, Turnagain and Knik Arms, and the Copper River
Basin starting this morning and extending into Wednesday.
As the upper low continues to move eastward into the mainland, a
secondary cold front will start extending out ahead of the low
Wednesday into Thursday. This will cause temperatures to drop
below normal for most locations, increasing the potential for snow
to occur at some lower elevations as snow levels decrease. Latest
model guidance continues to indicate a deformation band setting
up over Cook Inlet, the Anchorage Bowl and the MatSu which will
serve to increase precip totals in those areas. A chance for rain
and snow showers will persist through Thursday afternoon before
the low starts to weaken and move eastward towards Canada.
-CC
&&
.SHORT TERM FORECAST FOR SOUTHWEST ALASKA, THE BERING SEA AND THE
ALEUTIANS (Days 1 through 3: Today through Thursday)...
Active weather continues as two weather systems are poised to move
across the Bering Sea, Aleutian Islands, and Southwest Alaska
through Thursday. Forecast confidence is moderate to high due to
good model agreement, with precipitation type being the biggest
forecast challenge as cold air moves in aloft. No major hazards
are currently being monitored.
The first weather system features an occluding low near the
Pribilof Islands, with its front extending across Southwest
Alaska. A stout upper level shortwave rotating around the low has
led to an intensification of rain rates along the front this
morning, with radar showing moderate to heavy rainfall with
reflectivities as high as 50 dBZ. Up to another 0.5" of rain are
expected (with locally higher amounts possible) as the front
moves east across Southwest Alaska through today, with the
greatest amounts expected for Bristol Bay and Lower Kuskokwim
Valley. Winds have also picked up with the intensification of the
front; gusts of 30-35 kt are currently being observed as winds
channel through Kamishak Gap and across both interior Bristol Bay
and the Lower Kuskokwim Valley.
For the Bering Sea and Aleutian Islands, gusty winds are also
forecast as vorticity and cold air advection help enhance winds. A
wide swath of westerly winds sustained at small craft speed (25
kt), with a small area of gales (35 kt), will move across the area
through today. Scattered showers are also expected across the
Aleutian Islands, with more frequent showers expected for the
Pribilof Islands nearer the low center. Conditions gradually
improve through today for the Bering Sea and Aleutian Islands as
the low exits into Southwest Alaska. For Southwest Alaska, the
incoming occluded low will mean a continuation of precipitation
through Wednesday even as the front exits the area. Expect showers
to be widespread, especially as another shortwave moves in off
the Bering Sea and helps to enhance precipitation.
A second low and its front move into the Western Bering and
Aleutians by tonight, signaling a quick return to wetter weather.
Winds will be a bit stronger, with a broader swath of gales
wrapping around the low and moving across the Western and Central
Aleutians through Thursday. With cold air lingering in the Bering
Sea courtesy of today`s low, there is a chance for very light snow
accumulations for the Pribilof Islands and Kuskokwim Delta
coast/Nunivak Island as the front moves through. Precipitation
type is a little uncertain, but either way, no more than a light
dusting of snow is expected.
-KC
&&
.LONG TERM FORECAST (Days 4 through 7)...
Friday, an upper-level low over the eastern Bering drops across
Southwest Alaska and into the Gulf by Saturday afternoon. A
trough sets up over the western coastline bringing possibly mixed
rain and snow for the Western coastline and all rain elsewhere,
primarily to Kodiak and the eastern Kenai. A high pressure ridge
forms across the Bering before the next upper-level low
consolidates and moves eastward from the vicinity of Attu Island
on Monday.
&&
.AVIATION...
PANC...A trough arriving from Southwest Alaska this morning will
bring light rain and the potential for MVFR conditions through
much of the day. Winds are expected to increase out of the
southeast through the afternoon hours as the pressure gradient
over the region tightens and the Turnagain Arm wind becomes more
prominent. Southeast gusts as high as 40 knots over the Upper
Hillside and over Cook Inlet should be more manageable for PANC at
15 to 25 knots.
-BL
&&
$$
000
FXAK69 PAFG 211051
AFDAFG
Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
251 AM AKDT Tue May 21 2024
.SYNOPSIS...
A Bering Sea front is moving inland across the West Coast tonight,
and this will shift northeast today. Alaska Range gap winds will
increase as well and will peak late this afternoon and evening,
but it should become breezy across most of the Interior today with
that chinook flow. Temperatures remain above seasonal norms for
the Interior into Wednesday, then things cool down with chances
for rainfall on Thursday. Break-up continues over the Yukon Delta
and Lower Yukon, and breaking is beginning over parts of the N
Slope, as well. Snowmelt flooding will be a concern over the Yukon
Flats along the Porcupine River in the coming days.
&&
.DISCUSSION...
Upper Levels and Analysis...
There is a 522 dam mobile low over the Bering Sea with a leading
shortwave trough/front moving into the YK Delta this morning in
the form of widespread rain/rain showers. There is a shortwave
ridge aloft over the E Interior, with heights around 555 dam.
There is a departing mobile shortwave trough over the BC region of
Canada, with heights around 540 dam. There is a 991 mb low over
the Bering Sea and a 1029 mb high over the arctic waters. There is
a weak thermal trough over the S Interior.
Model Discussion...
Models are in very good agreement with the general pattern but
they continue to struggle with the way the Bering low transitions
into the Gulf of Alaska, which will then have a significant
influence on the precipitation pattern over the Interior Wed night
and Thu. Overall, the models all show something semi-similar but
all different, so we will just favor a continued blend at this
time, which continues the theme of cooler by Thu with increased
chances for rain showers. Prior to that, we favored the hi-res
winds and we also increased winds today over the Interior due to
the chinook flow.
Central and Eastern Interior...
Another nice day today, with increased southerly winds and temps
pushing up to near or slightly above 70 once again. Gap winds in
the AK Range will peak today and this evening with gusts to near
50 mph then trend down Wednesday evening. Heavy rain showers will
develop Wed evening and into Thursday, but there is very low
confidence where those will occur, and right now, the best bet is
likely over the higher elevations, with less chances over the
lower elevation valleys. Showers persist into Friday along with
cooler temps from the recent string of above average readings.
West Coast and Western Interior...
A front with widespread rain/rain showers and easterly winds is
moving inland across the YK Delta and shifts across the Seward
Peninsula and Interior through tonight. Rain showers behind this
front will rotate in from the Bering Sea and will persist into
Wednesday. Another front brings more rain to the SW Coast and
Lower Yukon Thu night and Fri. Three day total rainfall amounts
will be rather light, with around 0.5 inches on the lower Yukon to
0.25 inches or less further north.
North Slope and Brooks Range...
Stratus, fog, periodic snow showers and east winds will dominate
for the next several days. Wind gusts to gale force will develop over
the W Arctic from Point Lay to Point Hope later today into early
Wednesday. There is a chance that snow showers may turn to mixed
precip after today as warmer air aloft moves in, with spotty ice
pellets or possibly freezing drizzle. The crest of the Brooks
Range will see increased chances for rain (snow above 2500 feet by
Wed night) showers midweek and beyond as an arctic front stalls
over the mountains.
Extended Forecast Days 4-7...
A progressive Bering sea flow continues in the extended period as
yet another Bering front is moving inland across SW AK early
Friday. This low takes the exact same path as the last and will
dive into the Gulf of AK and bring showers to the Interior. After
Monday, it looks fairly blase weather-wise with minimal
significant impacts, and no significant anomalies to note as the
Mainland finds itself sandwiched between several weak upper level
lows.
Coastal Hazard Potential Days 3 and 4...None.
&&
.FIRE WEATHER...
No changes to thinking with a minor chinook pattern today, but
strong enough to push AK Range gap winds to 30+ mph, which will
support red flag conditions down by Delta Junction. However, it
will be generally dry and breezy everywhere this afternoon in the
Interior with widespread min RH values in the teens and low 20s.
And with temps in the low 70s, it will be near critical weather
conditions across most of the E Interior and Tanana Valley today.
Wednesday the chinook is waning and temps come down, along with
weaker winds. Rain shower chances increase Thu with cooler temps
into Fri. Right now, no thunderstorm chances are anticipated,
although there is a less than 5 percent chance on Thu along the
ALCAN.
&&
.HYDROLOGY...
Lower Yukon break-up continues as running ice and high water
remain at St Mary`s, Pitkas Point and Mountain Village and a ice
jam flood watch remains for those areas through Tue. The break up
front is now downstream of Mountain Village and will likely get to
the Yukon Delta at Alakanuk, Emmonak, Nunam Iqua and Kotlik
sometime between late tonight and Fri, bringing the risk of ice
jam flooding to those areas tonight through Fri. Flood watches
are out for all these areas.
The water levels along the Porcupine River at the Border rose to
record levels over the weekend due to heavy snowmelt. This high
water is expected to reach Ft Yukon on Wed, where it will
gradually fills sloughs and swales east of Ft Yukon and eventually
bring high water into Ft Yukon late this week with high water
continuing into next week. A flood watch is valid front this Wed
through next week Wed.
There are no new reports about the Buckland River, but there was a
reported ice jam downstream of Buckland a couple days ago with
rising water levels. We will continue to monitor.
Rivers on the North Slope are beginning to flow with water
flowing over ice with some open water areas. Those area will
continue to see increasing melt this week.
&&
.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Flood Watch for AKZ825.
Flood Watch for AKZ826.
Flood Watch for AKZ833.
Red Flag Warning for AKZ937.
PK...Small Craft Advisory for PKZ803.
Small Craft Advisory for PKZ804-805-807.
Brisk Wind Advisory for PKZ806.
Brisk Wind Advisory for PKZ810.
Small Craft Advisory for PKZ811.
Small Craft Advisory for PKZ812.
Brisk Wind Advisory for PKZ814.
Brisk Wind Advisory for PKZ815.
Small Craft Advisory for PKZ816.
Small Craft Advisory for PKZ817.
Small Craft Advisory for PKZ850.
Small Craft Advisory for PKZ851.
Small Craft Advisory for PKZ852.
Brisk Wind Advisory for PKZ853.
Small Craft Advisory for PKZ854.
Brisk Wind Advisory for PKZ856.
Brisk Wind Advisory for PKZ857-858.
Brisk Wind Advisory for PKZ860-861.
&&
$$
Ahsenmacher
000
FXAK67 PAJK 211424
AFDAJK
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
624 AM AKDT Tue May 21 2024
.SHORT TERM.../Through Tonight/...There is some patchy radiation
fog over the Panhandle this morning, especially over the northern
half, due to decreasing clouds, light and variable winds, and
plenty of surface moisture in place. That fog will thin out
within just a few hours of sunrise. Conditions will generally
continue to improve through the period as a ridge of high pressure
continues to build in from the west and make its transit over the
entire eastern Gulf and southeast Alaska region. Generally partly
cloudy skies and dry conditions are expected through the period.
Winds and seas over the Panhandle, Inner Channels, and the eastern
Gulf will remain rather benign through the period. Fog is
possible once again over the Panhandle tonight as the majority of
the region will have decreased cloudiness, light winds, and enough
ground moisture in place from the recent rains. Another frontal
system will approach the Panhandle Wednesday morning.
.LONG TERM.../ Wednesday through Saturday night / Active pattern set
to continue for SE Alaska for the remainder of the week. The next
system will move into the northern Gulf on Wednesday, with a
weakening front making its way towards the panhandle Wednesday
afternoon and slowly push inland through Thursday. While not an
impressive system, tightening of the pressure gradient near shore
will still lead to winds of 25 to 30 kt for the Northern and NE gulf
coast for a time Wednesday afternoon into Wednesday night.
Consequently not expecting to see any significant wave height
increases.
Total precipitation from this system has been trending upwards
slightly, but overall is still expected to be light to moderate by
SE AK standards, with most rain coming Wednesday night into Thursday
morning. Storm total QPF for the panhandle ranges from around 0.75
inches for the northern Gulf coast to around 0.5 inches from the Icy
Strait Corridor southward. Once the rain moves through and
accompanying low diminishes into a weak open trough, skies are set
to clear later in the day Thursday and into Friday. This will allow
for potential fog development in areas which can see maximized
radiational cooling in the overnight hours along with light winds.
Clearing skies on Friday means warmer temperatures once more, with
daytime highs rebounding back to upper 50s and near 60 for the
majority of the panhandle heading into Saturday. Unfortunately
unsettled weather looks to move in once more for the second half of
the holiday weekend with increasing rain chances Saturday afternoon
into Sunday.
&&
.AVIATION...Some MVFR CIGS around the region this morning and
patches of fog becoming widespread VFR SKC by Tuesday late
morning. Overcast VFR skies develop Tuesday night as our next
system slides across the Gulf.
&&
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ652-672.
&&
$$
SHORT TERM...JLC
LONG TERM....Bezenek
AVIATION...AP
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