Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/21/25
Area Forecast Discussion
National Weather Service Green Bay WI
509 PM CST Mon Jan 20 2025
Updated aviation portion for 00Z TAF issuance
.KEY MESSAGES...
- Dangerously cold weather is expected through Tuesday afternoon.
Wind chills will range from 25 to 45 below zero in central and
north central Wisconsin and 20 to 35 below zero elsewhere. The
coldest wind chills will be late tonight into early Tuesday
morning.
- An Extreme Cold Warning is in effect for north-central Wisconsin through
noon Tuesday.
- A Cold Weather Advisory is in effect for central and northeast Wisconsin
through midnight tonight. An Extreme Cold Warning is then in
effect from midnight tonight through noon Tuesday.
- A warming trend will begin on Wednesday, lasting into the
weekend.
&&
.DISCUSSION...
Issued at 153 PM CST Mon Jan 20 2025
Short Term...Tonight and Tuesday
The latest RAP analysis and satellite/radar imagery show arctic
high pressure centered from the northwest Great Plains to the
central Gulf Coast early this afternoon. The coldest air during
this arctic air outbreak so far lies from northern Minnesota to
the Dakotas where 32 below to 36 below temps at 850mb are analyzed
by 12z raobs at International Falls and Bismarck. Across northern
Wisconsin, surface temperatures have warmed to around 0 degrees
over the Fox Valley and from 5 below to 9 below zero over north-
central Wisconsin at 1 pm. Wind chills generally range from 15
below to 30 below zero.
The core of the coldest air will swing across the region tonight
into Tuesday morning. While there are scattered clouds upstream,
don`t think this will have a significant impact on temps if they
move into northern WI tonight.
Snow cover is playing a significant role with temp/wind chill
forecasting. Snow depths are analyzed to be greater than 2 inches
generally north and west of a Wausau to Iron Mountain line. Where
this minor snowpack exists, winds decoupled last night at times
which mitigated the impacts of the extremely cold wind chills. MOS
forecast guidance indicates similar wind speeds tonight, and
think will see winds drop off at times. This means that while low
temps will likely be colder than the NationalBlend guidance, wind
chills may not always fall into warning criteria. But of course
when there is even a slight wind, wind chills from 35 below to 45
below zero can be expected. Have therefore lowered min temps over
north- central WI closer to ECMWF statistical guidance.
Elsewhere, wind chills remain on track to fall into the 30 below
to 40 below range late tonight through Tuesday morning. No changes
to the extreme cold headlines appear warranted.
Highs on Tuesday afternoon will likely remain below at or below zero
away from Lake Michigan with wind chills ranging from 20 below to
25 below zero. A Cold Weather Advisory after the Extreme Cold
Warning expires will likely be needed through late in the
afternoon or late in the evening. Quite a bit of uncertainty how
long to run the subsequent advisory as wind chills hover right
near or just below criteria. So after coordinating with
surrounding offices, have refrained from an Advisory issuance.
This will likely be the coldest stretch of weather since the last
two days of January 2019. NWS La Crosse has a nice write up of
that event at weather.gov/arx/jan2019.
Long Term...Tuesday Night Through Monday
Focus in this part of the forecast remains on the tail end of the
arctic outbreak on Tuesday night followed by light snow chances at
times.
Temperatures/wind chills: Arctic high pressure will slide from the
Ohio Valley to the mid-Atlantic states as a warm front moves into
the northern Mississippi Valley on Tuesday night. As the surface
high departs, both warm advection and cloud cover will increase
through the night. Both these trends should lead to a warming trend
after low temps occur in the evening. As a result, it looks like a
Cold Weather Advisory will only be required through the end of the
evening.
Temperatures will moderate from Wednesday (middle teens to lower
20s) through the weekend (middle to upper 20s). Temps appear to
have trended colder this weekend, so the probability of reaching 30
degrees has decreased.
Light snow chances: Forecast soundings indicate sufficient
saturation will occur prior to 6 am Wed for a chance of light snow,
but think some of the upward motion will get lost to creating
saturation of a very dry arctic airmass. It also appears that
moisture profiles are disjointed. Therefore snow chances will
remain low on late Tue night into Wednesday night. Isolated
accumulations up to 1 inch appear possible but most locations will
see a dusting to a half inch.
Additional shortwave energy and a cold front will arrive this
weekend in a similar fashion (unfocused/disjointed). The chance of
light snow will be the highest during the late Friday night into
Saturday timeframe, but accumulation potential looks minor.
&&
.AVIATION...for 00Z TAF Issuance
Issued at 455 PM CST Mon Jan 20 2025
The arrival of a short-wave trough, combined with daytime mixing,
has resulted in a bit more low cloud cover in our western counties
than previously expected, so have increased sky cover a bit
tonight. Have seen a few reports of MVFR ceilings in parts of NC
and especially C WI late this afternoon, and even some light snow
showers or flurries in C WI. Expect the low clouds to decrease a
bit early this evening, with more widespread clearing occurring as
the short-wave departs later this evening. light to moderate west
winds will persist through the TAF period, along with continued
frigid temperatures and wind chills.
Looking ahead, strong WAA developing ahead of an approaching
clipper low pressure system will bring light snow to the region
later Tuesday night into Wednesday morning. Strong southwest winds
aloft will overspread the region Tuesday evening, leading to
LLWS.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Extreme Cold Warning until noon CST Tuesday for WIZ005-010>012-
018-019.
Cold Weather Advisory until midnight CST tonight for WIZ013-
020>022-030-031-035>040-045-048>050-073-074.
Extreme Cold Warning from midnight tonight to noon CST Tuesday
for WIZ013-020>022-030-031-035>040-045-048>050-073-074.
&&
$$
DISCUSSION.....MPC/MPC
AVIATION.......Kieckbusch
Area Forecast Discussion
National Weather Service Grand Rapids MI
1010 PM EST Mon Jan 20 2025
.KEY MESSAGES...
- Arctic Blast with Lake Effect Snow
- Clipper and Lake Enhanced Snow Late Week
&&
.UPDATE...
Issued at 1010 PM EST Mon Jan 20 2025
No changes to the ongoing winter/cold weather advisories.
An uptick in snow intensity has been taking place this evening
due to the approach of the upper trough axis and associated
stronger lift. GRR VAD wind profile indicates inversion heights
are running around 9K ft which is pretty impressive especially
given how cold the air mass is. Only limiting factor has been a
DGZ which is close to the ground, producing a finer/powdery type
of snow that does accumulate as efficiently as larger dendrites.
It`s been interesting watching a narrow intense snow band this
evening extending east through LAN and all the way to Port Huron.
This is related to an elongated zone of good low level
confluence, although confidence is low with respect to overnight
trends since the current clearing north of this zone may force a
southward shift. In that case the confluence zone may line up more
along I-94 by the morning commute.
Temps/wind chills thus far have been largely just shy of advisory
criteria and the HRRR is showing winds relaxing to 5-10 kts over
much of the area overnight. (Wind stay up higher at the
lakeshore.) Still, it`s close enough and colder temps/wind chills
are expected Tues afternoon/night once the winds pick up again.
&&
.DISCUSSION...
Issued at 330 PM EST Mon Jan 20 2025
- Arctic Blast with Lake Effect Snow
No changes to the going advisories for snow and cold at this
point. We may need to extend the Winter Weather Advisory for the
northwest forecast area through Wednesday night as forecast
guidance shows a bullseye of about 3 to 5 inches of snow from
Muskegon to Ludington in the classic southwest flow lake effect
regime.
The Cold Weather Advisory continues through Wednesday morning with
apparent temperatures, from the combination of wind and air
temperatures, bottoming out between midnight and 6 am Wednesday
near or even below -20F. A few of the colder spots away from the
influence of Lake Michigan could touch -25F but only briefly.
- Clipper and Lake Enhanced Snow Late Week
Flow goes southwest as the polar anticyclone moves east on
Wednesday, setting up an enhanced area of lake effect snow across
the northwest forecast area Wednesday into Thursday. Lighter
synoptic snow of an inch or two expected elsewhere as the
clippers moves through.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 652 PM EST Mon Jan 20 2025
Lake effect snow in frigid westerly flow producing IFR to LIFR
vsbys around MKG/GRR/AZO, pointed toward LAN. VFR likely for JXN
meanwhile being away from the lake effect, with BTL teetering
between VFR and IFR on the edge of the snow shower activity. West
or southwest sfc winds averaging around 10 kts but higher along
the lakeshore at MKG where some BLSN may also be a factor.
&&
.CLIMATE...
Issued at 330 PM EST Mon Jan 20 2025
- Coldest High Temperatures Recorded on January 21
Grand Rapids: 5 (1984)
Lansing: 0 (1984)
Muskegon: 5 (1924)
Kalamazoo: 5 (1924)
Battle Creek: 0 (1984)
Holland: 9 (1963)
- Snowfall Records for January 21
Grand Rapids: 6.1 (1958)
Lansing: 10.0 (1904)
Muskegon: 7.9 (1959)
Kalamazoo: 8.0 (1959)
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory until 1 AM EST Wednesday for MIZ037-043-
050-056-064-071.
Cold Weather Advisory until noon EST Wednesday for MIZ037>040-
043>046-050>052-056>059-064>067-071>074.
Winter Weather Advisory until 7 PM EST Tuesday for MIZ038-044-
057-058-065>067-072>074.
MARINE...Small Craft Advisory until 9 AM EST Thursday for LMZ844>849.
Heavy Freezing Spray Warning until 1 PM EST Wednesday for
LMZ844>849.
&&
$$
UPDATE...Meade
DISCUSSION...Ostuno
AVIATION...Meade
CLIMATE...CAS
Area Forecast Discussion
National Weather Service San Francisco CA
332 PM PST Mon Jan 20 2025
...New AVIATION, MARINE...
.SYNOPSIS...
Issued at 144 PM PST Mon Jan 20 2025
Strong, gusty winds continue over the North Bay and East Bay Hills
where Wind Advisories will be in effect through 1 AM Tuesday. Cold
mornings continue through late week with Frost and Freeze products
likely to be reissued throughout the week. Daytime temperatures
will see a slight warming trend Tuesday through Thursday before
another pattern change takes place late week.
&&
.SHORT TERM...
(This evening through Tuesday)
Issued at 144 PM PST Mon Jan 20 2025
Gusty winds have been observed across the Bay Area with peak gusts
ranging from 66 mph to 72 mph. These winds have largely been
concentrated over the interior North Bay Mountains where a Wind
Advisory went into effect at 4 AM and will expire at 1 AM Tuesday.
Gusty winds have additionally been observed in the East Bay Hills
where a few stations are hovering right around Wind Advisory
criteria. A few sites (PG914 and PG696) in the vicinity of Mt.
Diablo State Park have been gusting to between 45 to 50 mph. With
this in mind, a Wind Advisory has been issued beginning now through
1 AM Tuesday for the East Bay Hills with gusts between 35 to 50 mph
possible. Diving deeper into our winds, the SFO-WMC pressure
gradient was -12.40 hPa as of noon. This has weakened (slightly)
from earlier in the morning when the gradient was -12.70 hPa at 10
AM PST. WRF guidance shows the pressure gradient begins will begin
to weaken more significantly during the late evening hours which
should coincide with winds starting to weaken. There is some
uncertainty on when the gradient will switch from negative
(offshore) to positive (onshore). The WRF shows the switch happening
early to mid morning on Tuesday whereas the HRRR and GFS models both
show it happening later Tuesday morning. Regardless, as the pressure
gradient weakens winds will gradually ease over the Bay Area and
drop below Wind Advisory criteria by very early Tuesday morning.
Conditions are expected to remain clear overnight which brings us to
our second hazard, a combination of Freeze Warnings and Frost
Advisories. Frost Advisories have been issued for the interior Bay
Area and Central Coast except for the southern Salinas Valley where
a Freeze Warning has been issued instead. For the Frost Advisory,
overnight temperatures are expected to drop as low as 33 degrees
with particular emphasis on the Valleys and highest ridgelines.
Given the clear skies anticipated overnight, additional radiational
cooling is expected to occur overnight which will push more
locations across the CWA into Frost Advisory territory. A Freeze
Warning will be in effect overnight for the southern Salinas Valley
where temperatures will drop as low as 26 degrees. Portions of the
Fort Hunter Liggett area and far southeastern Monterey County may
see locally colder temperatures dropping as low as 29 degrees. These
areas are bordering the Southern Salinas Valley and Arroyo Seco
zone. Cold mornings will continue through the week ahead with high
confidence in the additional issuance of Frost Advisories and medium
confidence in the additional issuances of Freeze Warnings over the
upcoming week.
&&
.LONG TERM...
(Tuesday night through next Sunday)
Issued at 144 PM PST Mon Jan 20 2025
For those of you who would prefer slightly warmer daytime weather
and less breezy conditions, the next week is for you! The positively
tilted upper level trough that has been digging into the West Coast
(bringing our early week wind) continues to look fairly progressive
and is expected to move eastward, away from the West Coast, on
Tuesday. In its place a ridge of high pressure will build over the
West Coast and bring with it clear skies and a gradual warming trend
through the week ahead. Daytime temperatures will generally be in
the 60s while the warmest portions of southern Monterey county may
reach the low 70s. On the flip side, clear skies overnight will lead
to additional radiational cooling and will continue to necessitate
the issuance of Frost/Freeze products across the Bay Area and
Central Coast. The most likely locations will be in the North Bay
Valleys and the interior Central Coast.
The pattern will again change late week as an upper level low slides
into the western United States and deepens over CA, with the ECMWF
showing the upper level low becoming cut-off over the Bay Area
before moving southwards. While this system continues to trend
fairly dry, it does look as though it will produce strong, gusty
winds both over the marine environment and over the interior North
Bay Mountains and East Bay Hills. High end small craft warnings are
likely over the southern coastal waters while Gale Warnings are
likely over the northern coastal waters. The NBM continues to show
PoPs in the range of 30-40% along the Central Coast and lower PoP
values across the Bay Area. If any rain does develop with this
system, it is likely to be only drizzle directly along the coastline
with particular emphasis on coastal Monterey County. Any rainfall
that does accumulate on the Central Coast is likely to be less than
a tenth of an inch, not meeting wetting rain criteria. CPC guidance
highlights the weeks 3-4 outlook (February 1 - 14th) as when the
return of above average precipitation is likely.
&&
.AVIATION...
(00Z TAFS)
Issued at 331 PM PST Mon Jan 20 2025
Clear skies across the terminals. With the offshore pattern and dry
conditions, expect VFR through the TAF period for all terminals.
Gusty and breezy offshore winds will start to diminish after 02-03Z
to light winds and will remain light through the TAF period.
Vicinity of SFO...VFR through the TAF period. Moderate NE winds will
diminish to light this evening and expected to turn to NW by Tuesday
afternoon.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR through the TAF period. SE drainage
expected this evening with moderate speeds. Winds turn NW by Tuesday
afternoon.
&&
.MARINE...
(Tonight through next Saturday)
Issued at 331 PM PST Mon Jan 20 2025
Offshore breezes prevail across the waters through Tuesday, with
moderate to strong breezes within the San Pablo and San Francisco
Bays through early Tuesday morning. Winds calm after Tuesday
through Thursday. Moderate seas will persist through Thursday
with significant wave heights becoming rough by Friday. Gale force
winds are expected Friday and into the weekend.
&&
.BEACHES...
Issued at 334 AM PST Mon Jan 20 2025
A Beach Hazards Statement is in effect for all Pacific Coast beaches
through 7 PM as a long period westerly swell is resulting in a
moderate to high risk of sneaker waves and an increased risk of rip
currents. For beachgoers to remain safe it is vital to keep off of
jetties and rocks, keep pets on a leash, observe the ocean for 20
minutes before recreating on the beach or in the ocean, and never
turn your back on the ocean.
Sarment
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement until 7 PM PST this evening for CAZ006-
505-509-529-530.
Wind Advisory until 1 AM PST Tuesday for CAZ504-515.
Frost Advisory from 1 AM to 9 AM PST Tuesday for CAZ504-506-510-
513>515-517-518-528.
Freeze Warning from 1 AM to 9 AM PST Tuesday for CAZ516.
PZ...None.
&&
$$
SHORT TERM...Kennedy
LONG TERM....Kennedy
AVIATION...SO
MARINE...SO
Visit us at www.weather.gov/sanfrancisco
Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/nwsbayarea
www.twitter.com/nwsbayarea
www.youtube.com/nwsbayarea