716
FXAK68 PAFC 270005
AFDAFC
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
405 PM AKDT Fri Jul 26 2024
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Sunday night)...
A deep negatively tilted upper level trough continues to push
steady light to moderate rain through Southcentral Alaska.
Precipitation will continue to taper off through Saturday from
southwest to northeast as the upper low and trough exit to the
north and east. Conditions will clear out and clouds will decrease
under drier westerly flow aloft leading to relatively warmer
temperatures and some sunshine on Saturday.
Strong zonal flow aloft will steer a shortwave trough quickly
eastward from the Bering into the Gulf on Sunday. There is still
model spread with regards to the track and timing of of the
shortwave and whether it clips Southcentral or remains mostly
south over Kodiak Island and the Gulf. Regardless, there is
another chance of a quick-hitting rain event on Sunday as this
shortwave moves through. There is higher confidence in another
upper level low and trough crossing the Bering Sea and into
southern Alaska Sunday night into Monday. This is expected to
bring another round of widespread light to moderate rain across
Southcentral Alaska.
-ME/SEB
&&
.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days
1 through 3: Tonight through Sunday Night)...
Discussion:
The occluded upper low has lifted up towards the Yukon Delta and
Norton Sound region this afternoon with associated frontal boundary
pushing northeastwards across interior Alaska. More widespread
precipitation has transitioned over to more showery conditions as
the 500 mb low center and cooler temperatures aloft have steepened
lapse rates over the Kuskokwim Delta. Showers should diminish from
southwest to northeast this evening as the upper low continues to
track inland tonight. Weak shortwave ridging moving in behind this
system will allow for continued onshore flow, and possibly resulting
in some areas of fog developing by Saturday morning.
Another disturbance is currently moving across the central Aleutians
bringing moderate to heavy rain, some gusty winds, and low ceilings.
This system is starting to weaken as cloud tops are gradually
warming, and will push east of the southern AKPen by Saturday
morning. However, several more disturbances will quickly move in on
nearly zonal flow behind the aforementioned system keeping the
Aleutians and Southwest in an unsettled pattern. Will likely see a
brief lull in rain and maybe see some peeks of sun between systems.
More widespread rainfall returns to Southwest Sunday morning and
into early next workweek with a Bering low pushing towards the
Kuskokwim Delta.
&&
.LONG TERM FORECAST (Days 4 through 7: Tuesday to Friday)...
An upper level trough digging across Southwest Alaska Monday will
continue to push east through late Monday into Tuesday. This
feature, while slightly different with each forecast model, looks
to bring widespread rain to Southwest Alaska late Sunday through
Monday and to Southcentral Alaska early Monday through early
Tuesday.
Unsettled conditions with periods of showers are then expected to
persist for Southern Alaska Tuesday and Wednesday as the upper
level low remains situated over mainland Alaska. Gusty
northwesterly gap winds are possible across the Alaska Peninsula
on Tuesday as the low departs to the east over the Northern Gulf
and a weak transient surface high builds in over the central
Aleutians. Another system emerges from the North Pacific and
impacts the Aleutians with periods of rain on Wednesday. Overall,
temperatures will remain below average for the long term period
with persistent cloud cover and rain.
-DD
&&
.AVIATION...
PANC...Showers will linger through the evening hours as a series
of shortwaves moves through the region. Expect mainly VFR
conditions this afternoon and evening with the occasional and
brief MVFR period in any lingering showers. VFR conditions will
then return as the primary trough axis crosses through the area
between 00Z and 06Z tonight. Gusty south winds will prevail for
much of the afternoon and early evening. Winds will diminish by
08z tonight.
CCC
&&
$$
189
FXAK69 PAFG 262101
AFDAFG
Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
101 PM AKDT Fri Jul 26 2024
.SYNOPSIS...
Is summer over? Not technically, but it will feel like it as a
cold front sweeps east, bringing rain and cooler weather to the
remainder of the Mainland this weekend. Snow will also fall to the
surface over parts of the Arctic Coast and N Slope this weekend.
&&
.DISCUSSION...
Upper Levels and Analysis...
There is a 547 dam low over Southwest Alaska with a departing
upper level ridge, now over the Yukon and NW Territory, with
heights around 572 dam. A cold front is tracking east, with that
front currently over the Central Interior. There is another
separate cold front over the Arctic, with moderate rainfall
extending W-E along that front. A thermal low persists over the E
Brooks Range.
Model and Forecast Discussion...
The models are fairly well clustered over the next few days, but
there are some uncertainties regarding the strength of a
wraparound band of rainfall on Saturday arcing from the Central
Brooks Range down to the S Interior around Fairbanks. The ECMWF
and Canadian models are notably stronger with that feature, with
heavier rainfall extending all the way down to Fairbanks. Given
the current strength of this low, this seems reasonable, so this
forecast will trend wetter. Also, it looks fairly reasonable that
the same feature will cause sufficient height falls/surface
pressure falls for a switch to all snow over parts of the N Slope
and Arctic coast Sat and Sat night, which we will also trend
towards.
Central and Eastern Interior...
Rainfall will shift east tonight along a cold front, with
southwest winds behind this front bringing in much cooler air
with it. There will be some breaks in rainfall early Saturday,
then it will fill back in as showers in the afternoon over most of
the Interior, with showers continuing into Sunday morning. It will
be briefly drying out Sunday evening with more rainfall moving in
Monday. Saturday looks like a fairly "raw" day with blustery
southwest winds to go along with the afternoon showers and temps
struggling out of the 50s. Isolated thunderstorms will be possible
through this weekend right along the ALCAN border, but right now,
it looks pretty meagre.
West Coast and Western Interior...
Rain and showers will wrap around a departing low, favoring the
Yukon Valley and the Norton Sound region, as well as the Upper
Kobuk and Noatak Valleys, through Saturday. High elevation snow
above a couple thousand feet in the Brooks Range can also be
expected as colder air wraps around the low center. It will be
briefly drying out Saturday night and Sunday as the low shifts
east, but more rainfall shifts inland Sunday night and early
Monday, along with near gale force north winds down the Bering
Strait Sunday night and Monday.
North Slope and Brooks Range...
Rainfall will be turning into accumulating snowfall for parts of
the Arctic Coast and N Slope this weekend, with the best chance
for snowfall from Prudhoe Bay to Toolik Field Station to the
Central Brooks Range. Several inches of snowfall is likely over
the higher passes, with a skiff to 2 inches for lower elevations
near the coast. Moderate to heavy rainfall of 1-2 inches is
likely, as well, before the turnover to mixed snowfall later on
Saturday. Snow and rain is tapering off Sunday night, with high
pressure persisting along with northeast winds.
Extended Forecast Days 4-7...
Broad upper level troughing will be in place Monday night and
Tuesday with cooler temps and showers persisting into Wednesday.
The latter half of the week will see more wet weather moving into
the West Coast as Bering fronts shift inland, which will keep
temps running slightly below seasonal norms.
Coastal Hazard Potential Days 3 and 4...None.
&&
.FIRE WEATHER...
A cold front sweeping east will shift all warm air into Canada
with wetting rains moving across the final dry spots of the
Interior, the Yukon Flats and SE Interior, this evening and
tonight. Showers and rainfall will persist through the weekend
along with temps below seasonal norms. The only slight chance for
thunderstorms will be along the ALCAN this weekend, with no
thunderstorms forecast early next week. Expect general southwest
winds and blustery conditions for Saturday.
&&
.HYDROLOGY...
1-2 inches of rainfall is expected over the Central Brooks Range
through this weekend, which will push some rivers draining into
the arctic to near action-stage this weekend, including the Sag
River. All rivers draining the Brooks Range will see rapid rises,
however, including the Koyukuk and Alatna.
&&
.AFG WATCHES/WARNINGS/ADVISORIES...
AK...None.
PK...Small Craft Advisory for PKZ806.
Small Craft Advisory for PKZ807.
Small Craft Advisory for PKZ810.
Small Craft Advisory for PKZ811-857.
Small Craft Advisory for PKZ812-858.
Small Craft Advisory for PKZ813.
Small Craft Advisory for PKZ814-815.
Small Craft Advisory for PKZ854.
Small Craft Advisory for PKZ856.
Brisk Wind Advisory for PKZ859.
Brisk Wind Advisory for PKZ860.
Small Craft Advisory for PKZ861.
&&
$$
Ahsenmacher
931
FXAK67 PAJK 262224
AFDAJK
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
224 PM AKDT Fri Jul 26 2024
.SHORT TERM... The current ridge in the gulf will continue to push
inland as a front moves in from the west. The first impacts with
the front will bring strong breezes to the northern gulf this
afternoon into the morning. The front is then expected to reach
the inside waters early Saturday morning increasing winds in Lynn
Canal into strong breezes to 20-25kts. Other inner channels will
also see a wind increase to southerly moderate to fresh breezes.
As this front reaches the panhandle it will dissipate leaving
likely chances of precipitation throughout the period.
.LONG TERM.../Sunday through midweek/...
Quick hits:
-Lingering onshore flow will keep lower chances (20-50%) of rain
in the forecast Sunday.
-Approaching 500mb low and associated surface low will cause
increasing chances of rain from north to south with high chances
(>80%) of rain for most of SE AK by Tuesday.
-Strongest winds on Sunday will be in northern Lynn Canal at
around 15 to 20 knots. Lighter wind speeds elsewhere.
-The approaching system will cause marine wind speeds to increase
everywhere late Monday into Tuesday.
Details: 500mb low with associated surface low over central Alaska
will slide southeast early next week. This will be the source of the
next round of rain and wind that will impact the area late Monday
into Wednesday.
Overall, 24 hour rainfall amounts aren`t looking all that impressive
with the hardest hit areas, the northern half of the panhandle,
getting around a half inch to one inch of rain Tuesday into
Wednesday. The higher percentiles, 75th to 90th, get closer to 1.5
to 2 inches. So higher amounts of rain are possible and will be
watched closely over the weekend.
As this next system approaches, wind speed will increase to upwards
of 15 to 20 knots. Higher wind speeds are expected in the gulf,
upwards of 25 knots, and in Lynn Canal, upwards of 20 to 30 knots.
The higher wind speeds in Lynn Canal are based on forecasted
pressure differences between Skagway and Juneau, where the
forecasted pressure difference is around -2.5mb, which historically
produces winds around 20 to 30 knots in July.
&&
.AVIATION... Currently conditions remain in VFR with a few
locations holding on to lower ceilings of around 2000ft. Late tonight
into tomorrow ceilings and visibilities are expected to drop with
a front that will create MVFR and IFR conditions.
&&
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ012-652-672.
&&
$$
SHORT TERM...EAB
LONG TERM....GJS
AVIATION...EAB
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