Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/12/25
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
429 PM AKDT Tue Mar 11 2025
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3:
Tuesday through Thursday evening)...
This afternoon, a 990 mb occluded surface low is weakening and
picking up forward momentum as it moves eastward across the
Central Gulf and away from Kodiak Island. Kodiak Island is now
just seeing a gusty northerly wind as the deformation snow band
has moved offshore. The Southcentral coast from Eastern Kenai to
Cordova to Yakutat remains showery with rain and snow along with a
stout easterly wind, but should diminish as the low weakens
further. To the north toward Glennallen, some light snow has
developed as 500 mb shortwaves and vorticity maxima have rippled
their way across the area. As of now, a larger upper low/trough
complex has begun to retrograde away from the Al/Can border and
Yukon area, providing additional dynamic support by cooling the
upper levels and steepening the environmental lapse rates.
Things become rather interesting from this point on in the short
term. Diving into the details, by early to mid morning Wednesday,
the extent of the upper support affecting Glennallen also enhances
shower activity to the south along the coast. At the same time,
as the upper low continues to trek southwestward across Southcentral,
model guidance suggests a weak wave of low pressure and surface
trough develops somewhere between Seward and the Prince William
Sound that works in tandem with cold air advection spilling over
the Alaska Range. Uncertainty with placement and timing of this
low is above average, but overall impacts appear to be low at this
time. The NAM is the wettest of the global models and also brings
in precipitation the earliest, while the GFS has remained bullish
on being drier and bringing in precipitation later in the morning
to even early afternoon hours on Wednesday. The HRRR is sitting
somewhere in the middle of the GFS and NAM in regards to low
placement and timing. It must be noted that even subtle shifts in
the track of the low can make a significant difference in the
forecast for some areas. However, regardless of if the low forms
more so near Seward or just outside of the Prince William Sound,
models do agree that the first area of interest with any notable
QPF from this wave is the windward/eastern Kenai Mountains, where
easterly upsloping could enhance snowfall rates.
As precipitation spreads into the Prince William Sound Wednesday
morning, it also tries to spill over into Valdez and eventually
Glennallen, closer to the upper low. Going forward into the midday
to afternoon Wednesday, although there are timing issues, most
models continue or start precipitation for Kenai, Cook Inlet, and
possibly as far north and west as the Anchorage bowl and Wasilla,
with forecast outcomes ranging from flurries to a period of light
snow. There looks to be some degree of a Turnagain Arm jet
regardless of where the low placement will be, which will send
easterly winds through the channel and eventually bend them
southward towards lower pressure to result in a down-inlet
gradient flow. Combined with the aforementioned cold air
advection, there could be a convergence or weak deformation zone
setting up for Cook Inlet, Anchorage bowl, and northward to
Wasilla and Palmer resulting in light snowfall accumulations.
Heading into late Wednesday into Thursday, the wave of low
pressure stalls, continuing precipitation for the Prince William
Sound and Valdez locations, and perhaps pushing moisture as far
south as Homer as the upper level support continues to drift
southwestward across South-Central.
By early to mid Thursday, the overall consensus is that the
eastern Kenai Mountains could see 2-4"+ of snow out of this system
with flurries to a couple tenths of an inch of snow for the
Anchorage bowl, Wasilla, and Palmer. 2-4" of snow with the surface
low could extend as far northeast as Valdez (especially since
moisture hangs on longer) and also for parts of the Copper River
Basin, dependent on the track of the low.
-AM
&&
.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days
1 through 3: Tonight through Friday)...
Somewhat quieter conditions have returned to much of the Bering
Sea and Aleutians for the time being as an upper ridge briefly
builds into place from the North Pacific. Scattered rain and snow
showers affecting the Pribilofs, eastern Aleutians and southern
AKPen have also become weaker and less numerous as the marine
layer becomes less unstable with time. Almost entirely clear but
cool conditions are now in place across Southwest where dry
northerly flow is becoming established this afternoon. Out along
the central and western Aleutians, the outer reaches of a gale
force front are already beginning to spread gusty east winds into
place. Precipitation is thus far starting out as a rain-snow mix
near Adak and Atka, but still could change over to a wet snow as
more intense bands of precipitation move in ahead of the front
overnight tonight. Snow will fully transition to rain as
temperatures warm and as the front reaches the Aleutian Chain.
On Wednesday, the front will gradually weaken below gale force as
it heads northeast towards the eastern Aleutians and southern
AKPen. Low level temperatures will initially be cool enough for
light snow to spread into place from west to east through
Wednesday afternoon. The front will begin to stall out as it
reaches the southern AKPen and southern Bering Wednesday night as
a new low also develops along the boundary south of Sand Point.
Precipitation will become more showery and change back over to
snow along the Aleutian Chain through Friday morning as the new
low slowly heads towards the Gulf and as winds turn more
northerly.
Across Southwest, seasonably cool and mostly clear conditions
along with weak north to northeast winds will continue up through
early Thursday. From Thursday to Friday, a weak upper level low
will move from the western Alaska Range out to the Lower Kuskokwim
Valley. This low could draw enough moisture north from the Gulf to
produce at least increasing cloud cover through Friday, and
possibly even areas of light snow across parts of Bristol Bay and
the Lower Kuskokwim Valley on Friday. Any snowfall that does
develop will likely be fairly light.
-AS
&&
.LONG TERM FORECAST (Days 4 through 7 - Saturday through Tuesday)...
A generally unsettled weather pattern covers the Alaska Region
from Siberia to Canada. The main feature across the North serves
as a pathway for low centers to transit from West to East, with a
couple of upper level ridges pushing across the Southern portions.
It all smoothes out to a single extended trough by the end of the
forecast period. A cutoff low in the Gulf of Alaska exits along
the West Coast for Monday. Model guidance is good across the
domain, with some uncertainty with transitory lows South of the
Alaska Peninsula Sunday. The GFS pushes stronger and faster
systems for the new week.
Lingering areas of snow moves over Southwest Alaska through
Saturday. A well developed surface and front pushes locally
moderate rain and gusty winds into the Western Aleutians and
Bering beginning Saturday. Areas of gale force winds develop
closer to the low center as it slips into the Western Bering,
diminishing Sunday. Gusty Easterly winds continue across the
Bering through Tuesday. This system continues an Eastward track
into Southwest Alaska for Sunday, then spreads the locally
moderate rain across Kodiak Island and the Southcentral coastal
zones through Tuesday. Areas of locally heavy rain are expected
along the Eastern Kenai and Western Prince William Sound late
Monday into Tuesday. Back in the Far West, another well developed
low and front approaches the Western Aleutians and Bering late
Monday, repeating the moderate rain and gusty winds for Tuesday.
- Kutz
&&
.AVIATION...
PANC...VFR conditions and light winds out of the north will
persist. The chance for light snow ticks up tonight, with the most
likely chance for light snow occurring Wednesday afternoon into
the evening. Ceilings may drop below 5000 ft at times tomorrow,
but conditions are generally expected to remain VFR.
&&
$$
Area Forecast Discussion
National Weather Service Billings MT
150 PM MDT Tue Mar 11 2025
.KEY MESSAGES...
- Warm Wednesday and Thursday with highs in the 50s and 60s (near
70 possible); showers increase over mountains Thursday
afternoon.
- Turning colder, a period of rain and wet snow, and brisk north
winds Thursday night and Friday; greatest chance of snow
accumulations over the mountains and foothills.
- Unsettled weather pattern with seasonable temperatures for the
weekend.
&&
.DISCUSSION...
Tonight through Wednesday night...
More weak vorticity will move through N MT tonight, affecting the
far northern part of the forecast area. Thus, kept low PoPs across
the N thru 12Z Wednesday. With lower RH`s expected than last
night, HRRR did not show any fog. Lows will be in the upper 20s to
lower 30s. Airmass will moderate under the upper ridge on
Wednesday, and high temps will be in the 60s with 50s over the
western foothills. RAP soundings showed deep mixing over the area
which will support gusty winds from KBIL W. Winds will gust into
the 30s-40s mph in K6S0 and KLVM. Wednesday will have mainly dry
weather, with just a slight chance of snow in the highest
elevations of the Beartooths/Absarokas. Ridge will start to shift
E Wed. night as elongated N-S trough sets up along the Pacific
Coast. SW flow aloft will bring a chance of snow to the SW
mountains. Low temps will be in the 30s to lower 40s. Arthur
Thursday through Tuesday...
A Pacific trough will split, with the northern portion impacting
the region into Friday. With this system, incoming moisture will
increase PWATs to 120-150% of normal (~0.3-0.5"), allowing for
decent snow accumulations in the mountains. Currently, there is a
40-60% chance of at least 6 inches of snow in the mountains. Over
lower elevations, precipitation will begin as rain due to warm
daytime temperatures before transitioning to snow overnight into
Friday morning. As a result, snow accumulations are expected to
remain fairly light, with a 40-60% chance of at least 1 inch of
snow in the foothills. Outside of the foothills, if frontogenesis
is strong enough and precip heavy enough, some wet snow could
briefly accumulate on the grass, although the chance of more than
1 inch of snow remains less than 25%.
With this system, there is still disagreement on how much (if any)
precip falls in the southeastern corner of the region. Winds are
expected to increase Friday morning, so if snow does fall, this
may cause some reductions in visibility during the morning
commute.
Drying arrives by Friday afternoon but below normal heights linger
through Saturday, bringing at least a chance of snow showers over
the mountains. There may be enough diurnal instability for
afternoon snow showers over the western lower elevations Saturday
afternoon/evening. Then, brief ridging will bring drier and warmer
conditions to Sunday.
For Monday through midweek, another trough is expected to move
into the region, bringing another round of precipitation.
High temperatures Thursday will be in the 60s to near 70. Then,
highs will drop to the upper 30s to upper 40s for Friday and
Saturday. Sunday will warm slightly under the ridge, with highs in
the mid 40s to mid 50s, before temperatures dip back to upper 30s
to upper 40s by Tuesday. Archer
&&
.AVIATION...
VFR conditions will prevail. Surface winds will become mostly calm
by evening. Winds will begin to increase out of the
south/southwest late Wednesday morning. Archer
&&
.PRELIMINARY POINT TEMP/POPS...
Wed Thu Fri Sat Sun Mon Tue
-----------------------------------------------------------
BIL 033/064 040/065 036/047 028/047 031/054 038/054 030/043
10/B 02/T 74/S 12/S 22/R 34/R 46/S
LVM 034/055 039/053 028/039 024/040 026/046 032/045 025/037
10/N 15/T 83/S 14/S 24/O 66/O 56/S
HDN 030/066 034/066 033/046 024/046 026/055 035/055 028/044
10/B 01/B 75/S 12/S 21/B 33/R 46/O
MLS 032/063 035/067 034/042 019/039 023/053 035/053 027/043
20/B 00/B 34/O 00/U 10/B 11/B 22/S
4BQ 031/064 036/065 034/041 021/040 024/052 033/053 029/043
10/U 00/B 35/O 00/U 10/B 11/B 24/O
BHK 029/061 033/064 031/039 014/035 016/048 028/051 023/040
20/B 00/B 15/O 00/U 00/U 11/B 23/S
SHR 029/062 032/062 028/040 019/041 021/051 030/051 024/040
10/U 01/B 68/S 12/S 20/B 23/O 47/S
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.
&&
$$
weather.gov/billings
Area Forecast Discussion
National Weather Service Grand Rapids MI
937 PM EDT Tue Mar 11 2025
.KEY MESSAGES...
- Warming the rest of the work week
- Showers, thunderstorms, wind Friday Night into Saturday
- Cold and wet Sunday then dry and warmer
&&
.UPDATE...
Issued at 937 PM EDT Tue Mar 11 2025
No changes needed to the forecast tonight as high pressure slowly
slips away from the Great Lakes to the east into Ontario. Mid and
high clouds drifting through the zonal flow aloft will provide a
partly cloudy sky. Winds increase once again overnight
(SE 30-35kts) around 2,000 feet, but not to levels of the last
few nights. We should keep fairly tame winds at the surface, 5-10
knots. The increase in wind aloft should hold low temperatures in
check bottoming out in the lower 20s to around 30. These values
are close to normal for this time of year.
&&
.DISCUSSION...
Issued at 244 PM EDT Tue Mar 11 2025
- Warming the rest of the work week
No changes of note to the previous forecast. This is the time of
year when maximum temperatures can somewhat overperform relative
to model guidance. This is related to the tendency for model
guidance to over-forecast daytime dewpoints/relative humidities.
Knowing this, we have tried to adjust for these known biases
accordingly.
Also of note, winds will be offshore in direction over the next
couple days. This is when we often see our warmest maximum
temperatures occur just inland from the lakeshore. The 12Z HRRR
seems to have a good handle on this areal temperature distribution
(as well as on the lower dewpoints), so have leaned heavily on
this guidance source instead of the straight NBM.
- Showers, thunderstorms, wind Friday Night into Saturday
The previous forecast is basically unchanged. Showers with some
thunderstorms will move into the area Friday night. There is a
low, but certainly nonzero, chance for some storms to become
severe Friday night/Saturday morning. Winds will be seasonally
strong on Saturday, This, combined with extensive cloud cover and
persistent warm advection Friday through Saturday will keep
Saturday night/Friday morning minimum temperatures well in the 50s
for much of the area.
Models and clusters seem to be locking into a solution in which a
sharp upper trough/cutoff low undergoes a cyclonic wave break Friday
night just upstream over the Wisconsin area. This would keep best
upper dynamic forcing in a relatively concentrated area just to our
west. Nonetheless, isentropic ascent associated with a strong low
level jet combined with modest PV advection aloft should still be
realized as far east into Lower MI during this time. This will
provide enough lift for the area to aid convective destabilization
and forcing for thunderstorms.
Winds will be quite gusty Saturday, but per EFI/SoT guidance, this
should be a pretty typical March event overall with low chances for
overperforming. This makes sense given that this remains basically a
warm advection/isentropic ascent pattern that is less efficient with
downward wind momentum transport.
- Cold and wet Sunday then dry and warmer
No changes to thinking Sunday. The upper trough axis will be
traversing the area during this time and the atmospheric column
will be cold enough to support a mix of rain and snow. After this,
the upper pattern is considerably more phased with an upper
shortwave ridge entering the western Great Lakes region. All else
being equal, this transition to ridging should provide
considerably drier and warmer conditions Monday and Tuesday.
&&
.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 813 PM EDT Tue Mar 11 2025
VFR weather is expected the next 24 hours. As for the
details...high pressure is situated over the Great Lakes this
evening which will slide east tonight and Wednesday. A developing
warm front will be located to our south across IL/IN/OH. Winds
will shift from the northeast tonight to the east on Wednesday
given our location between the departing high and warm front.
Mid and high clouds will slide through the region tonight with
bases largely at or above 10,000 feet. Mid clouds may linger on
Wednesday in association with the warm front to the south.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
UPDATE...Duke
DISCUSSION...TJT
AVIATION...Duke