Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/05/24
Area Forecast Discussion
National Weather Service La Crosse WI
545 PM CST Wed Dec 4 2024
.KEY MESSAGES...
- Strong northwest winds gusting 45 to 55 mph will persist
through the evening and a Wind Advisory remains in effect.
- Cold start to Thu with -5 to -15 F wind chills.
- Above normal temps return for the weekend with highs into the
40s for many, Sunday looking like the warmest day.
&&
.DISCUSSION...
Issued at 210 PM CST Wed Dec 4 2024
- TONIGHT/THU MORNING: strong winds persisting through the evening,
cold start to the day Thursday.
The strong/gusty winds will persist through the evening hours, but as
the storm system shifts east overnight...the pressure gradient will
star to slacken, mixing in the near sfc layer won`t be as deep nor
as uni-directional farther a loft, and the strongest low level cold
air advection shifts south/east. So, a drop in wind speed is
expected - still blustery - but enough that the wind advisory should
not need to be extended past midnight.
RAP/HRRR bufkit soundings continue to point to weak instability,
with RAP 1000:850 C/km also still pegging 8-9 C/km through the rest
of the afternoon hours. Radar imagery shows numerous snow showers
over central MN, mostly parallel to the mean flow, with a mix bag in
visibilities. This will spread across the local area through the
afternoon hours, gradually diminishing in extent/intensity and
exiting southeast by early evening. Accumulations still look to be
minor.
Strong influx of cold air, comparatively to the season, flows in
tonight with lows still looking to bottom out in the single digits
for most. Add in the still blustery winds and wind chills from -5 to
-15 will greet those headed to work/school Thu morning. Bundle up!
- WEEKEND: much warmer! Highs into the 40s for most Sunday.
Shortwave ridging builds across the upper mississippi river valley
for the weekend, providing an avenue for more seasonable to mild air
to surge northward. The EPS and GEFS have been very consistent in
this warming with approx 75% of both their ensemble suites pushing
40+ highs for most of the local area Sunday. The upper 5-10% suggest
50 could be reached at a location or two. A few degrees cooler
Sat/Mon.
Pcpn chances could return for Sunday night/Mon as the ridge starts
to exit east and a shortwave trough scoots across the region. EPS
and GEFS members currently hold the bulk of related QPF to the north
and south, although low level thermodynamics will aid pcpn chances
locally.
- NEXT WEEK: trending seasonable with periodic pcpn chance
After a quick shot of colder (but not as cold as Thu) air with the
shortwave for Monday, the long range models currently favoring more
zonal to broad ridging to work back in for much of the new week.
Moderating temps more in line with the seasonable norms would
result. Not much for pcpn chances at this time.
&&
.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 541 PM CST Wed Dec 4 2024
Widespread snow showers, bringing periods of IFR to even LIFR
visibilities, shift east of the region by 02-03Z, with MVFR to
VFR ceilings lingering for the rest of the night. Confidence is
low in when these ceilings will clear, but the current
indications are possibly around mid to late morning. Strong and
gusty northwesterly winds of 20-30G30-40kts slowly subside
through the night and the morning hours, becoming 5-10kts from
the WNW at by Thursday afternoon.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Wind Advisory until midnight CST tonight for WIZ017-029-
032>034-041>044-053>055-061.
MN...Wind Advisory until midnight CST tonight for MNZ079-086>088-
094>096.
IA...Wind Advisory until midnight CST tonight for IAZ008>011-018-
019-029-030.
&&
$$
DISCUSSION...Rieck
AVIATION...Skow
Area Forecast Discussion
National Weather Service Bismarck ND
653 PM CST Wed Dec 4 2024
.KEY MESSAGES...
- Northwest winds gusting as high as 40 mph will produce areas
of blowing snow until early this evening. A Winter Weather
Advisory for blowing snow remains in effect for eastern and
portions of central North Dakota.
- After a brief period of cold temperatures today through
tonight with wind chills down to 25 below zero. Temperatures
will then increase through the weekend.
- Mainly dry conditions are expected Thursday through Saturday,
with widespread low to medium chances (20 to 60 percent) for
precipitation returning Sunday into early next week.
&&
.UPDATE...
Issued at 647 PM CST Wed Dec 4 2024
Winds continue to gradually diminish, and with that the end of
almost all blowing snow with only some patchy spots around the
Turtle Mountains. Therefore, have let Winter Weather Advisory
expire. Other than that, other change was for later tonight
adding some low snow chances over the southwest as a modest
short wave drops through and mid-level warm air advection starts
to develop.
UPDATE
Issued at 429 PM CST Wed Dec 4 2024
Have trimmed off another tier of counties on the western edge of
the Winter Weather Advisory, as winds have diminished some over
this area. With that said, can not rule out a little drifting
snow in spots as winds continue to gust in the 30 to 35 mph
range, but the threat for blowing snow has diminished.
&&
.DISCUSSION...
Issued at 202 PM CST Wed Dec 4 2024
Our main concern early on is the ongoing winter weather advisory in
effect until 6 PM for the Turtle Mountains area into the James River
Valley.
Latest observations have shown some improvement in visibilities
compared to this morning. However, we are still into the wind
advisory criteria and certainly not cancel a winter weather advisory
and issue a wind advisory for only a few hours. Most likely will let
the advisory ride through the afternoon. The next shift would be
able to cancel early if warranted. If we would do any cancellations,
it would again be the western tier counties.
Next in line is wind chill temperatures tonight and overnight lows
early Thursday morning. Wind chills currently bottom out around 25
below zero, which if this verifies, would be below Cold Advisory
criteria. Forecast lows early Thursday morning are expected to drop
below zero for many areas in northern and eastern portions of the
forecast area. The surface high pressure center behind the exiting
clipper system is quick moving but does propagate southeast across
the forecast area tonight and at 12 UTC Thursday is forecast to be
roughly along the ND/SD border between Bismarck and Aberdeen. This
is an excellent location for cold low temperatures over south
central ND, including Bismarck. A look at the RAP moisture profiles
shows there may be some lingering low level stratus over eastern ND
and possibly into the James River Valley. Mid level moisture (700mb)
has pushed into western ND, approaching the Missouri River. There
may be a short window around 12 UTC, where temperatures would be
able to bottom out. This is roughly along and just east of the
Highway 83 corridor. A fresh and plentiful snowpack would have
really helped temperatures bottom out, but the warm
temperatures yesterday ate up a lot of our latest fresh snow.
Still think there is enough of a snowpack to help a little. How
quickly and efficiently the low clouds exit to the east and how
quickly the mid clouds approach from the west will be the
determining factor. We did use a blend of some of the cooler
guidance to lower temperatures a bit over central ND.
The approaching mid clouds from the west is due to a southerly
return flow and warm advection on the back side of the Arctic High.
Latest NBM guidance has backed off a bit with the PoPs over
western and into south central ND. Will keep some slight chance
pops for consistency but overall, the threat for snow amounts
greater than a trace to a few tenths seems limited. The latest
NBM probabilities of 24 snow amounts of a tenth of an inch or
more, ending at 18Z Thursday are highest over west central into
southwest ND and max out only around 30 percent.
Although we start off cold on Thursday morning, and we will likely
remain mostly in the teens over eastern portions of central ND, the
western half of ND is forecast to see high temperatures climb into
the 20s with some mid and even upper 30s possible in the far
southwest.
We remain in a northwest upper air pattern late in the work
week and into the weekend. Strong west coast upper level ridging
will result in building heights pushing into the northern
Plains. This will push most of the waves propagating through the
upper level ridge to the north and east of the forecast area.
In addition, NBM ensemble temperatures indicate rather
significant warm-up over the forecast area, from Thursday
through Saturday. Although these is some spread, in both the
forecast highs and lows, it`s not all that large (5 to 7
degrees). Currently it looks like a nice period of moderating
temperatures and mostly precipitation free, from Thursday
through Saturday. It may be a little breezy on Saturday, but our
current forecast high temperatures range form the mid 30s
around the Turtle Mountains, to the middle 50s in the southwest.
We do see increasing ensemble spread Sunday and early next week as
the western North America ridge breaks down, at least temporarily. A
northeast Pacific upper low moves onshore and brings widespread low
to medium (30% to 60%) chances of precipitation to all of western
and central ND (based on the latest NBM guidance). Currently,
although the precipitation looks to be widespread across the
forecast area in the late Sunday through early Tuesday
timeframe, the latest long range ensemble guidance is indicating
mainly light precipitation amounts. The probability of over an
inch of snow in a 24 hour period is maxed out at around 25 to 35
percent. We`ll see if this changes as head into the upcoming
weekend.
&&
.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 647 PM CST Wed Dec 4 2024
Gusty northwest winds over the James River Valley will continue
to decrease this evening. Otherwise, mainly quiet weather is
expected, though localized light snow may develop late tonight
over southwest North Dakota. This may result in a spot or two of
MVFR visibility, but overall most locations should remain VFR.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...JJS
DISCUSSION...TWH
AVIATION...JJS
Area Forecast Discussion
National Weather Service Boston/Norton MA
712 PM EST Wed Dec 4 2024
.SYNOPSIS...
A quick hitting system will bring accumulating snow near and
northwest of I-495 tonight into Thursday morning especially in
the high terrain with mainly rain on the I-95 corridor. A strong
cold front will likely bring a few snow squalls Thursday and
also result in strong winds developing. Gusty conditions and
below normal temperatures Friday into Saturday with a low
chance of an isolated snow shower or snow squall. A weak clipper
system passes through northern New England early Sunday and
brings a light snow shower to areas mainly north of Route 2 in
northern Massachusetts. Then the first-half of next week
features mild temperatures and a more active weather pattern.
&&
.NEAR TERM /THROUGH THURSDAY/...
Update: 7PM
Clouds have moved in across southern New England ahead of an
approaching Alberta Clipper system. Out ahead of this system
southerly flow form a modest LLJ continues to advect "warmer"
air into the region. A couple of pesky light rain and snow
showers have been around but, the bulk of the moisture remains
out to the west. Widespread rain and snow will hold off until
the mid to late evening hours which we will discuss below.
&&
.SHORT TERM /THURSDAY NIGHT/...
Key messages...
* Accumulating Snow tonight into Thu AM near and NW of I-495
* Greatest impacts in the Berks/Worcester Hills & Hills of NE CT
* Ptype mainly rain near and especially southeast of I-95
* A few snow squalls late Thu AM/Thu afternoon with poor vsbys
* Becoming Windy & Turning Colder Thu into Thu night
Details...
1) Ptype & Expected Snow Accumulations...
The Alberta Clipper will be tracking to our north across Quebec
tonight and into northern New England Thu. As this happens...it will
induce a strong SSW low level jet of 45 to 55 knots tonight. This
will increase the forcing for ascent and allow widespread rain &
snow to overspread the region from west to east in the 7 pm to 11 pm
time frame this evening.
The biggest forecast challenge revolves around Ptype as well as snow
accumulations & impacts. Given the fact that the surface low will be
tracking north of our region...southwest flow will warm temps aloft
and in the boundary layer to result in mainly rain near and
southeast of the I-95 corridor. Ptype could end as a bit of snow or
mix in this region Thu morning...but think any impacts will be
northwest of I-95. The main concern for accumulating and plowable
snowfall near and especially northwest of I-495. Thermal
profiles/soundings indicate that temps should be cold enough in this
region for mainly snow or rain quickly changing to snow. Given
marginal boundary layer temps...greater impacts/snow accumulations
will be in the higher terrain. Strong low level southwest flow will
also result in some mesoscale enhancement along the western side of
the Berks, Worcester Hills and northeast CT Hills. This can be seen
in a lot of the high resolution model guidance QPF fields. So while
the snow amounts should be elevation dependent to some
degree...expect to see the higher snow accumulations on the
western/upslope side vs the eastern side at the same elevations.
We continued the Winter Weather Advisory for western and central MA
and also include Tolland county to account for their higher
elevation. We generally expect 2-6" of snow to fall within the
Winter Weather Advisory with the greater of those amounts in the
high terrain...particularly on the western upslope side.
However...some travel impacts are expected in the lower elevations
and this may coincide with the Thu AM commute even just northwest of
I-95. Thermal profiles very marginal in this region though...so a
lot will be dependent on intensity which will be more of a nowcast
situation.
In a nutshell...motorists planning travel overnight into Thu morning
should be prepared for slippery travel northwest of I-495 and
especially in the high terrain. Confidence is high in a plowable
snow above 500 feet in elevation...but more uncertain and rate
dependent on the lower elevations.
2) A Few Heavy Snow Squalls later Thu morning and afternoon...
The other big concern for Thursday will be the potential for a few
heavy snow squalls later Thu morning and afternoon behind the
widespread activity. Several parameters are quite impressive with a
potent shortwave/cold front...steep 1000-700 mb lapse rates along
with some MUCape. This coupled with left over low level moisture
should result in a few heavy snow squalls developing later Thu
morning into the afternoon. The main concern is across the
interior...where roads could quickly become snow covered with strong
wind gusts and very poor visibility. We certainly may need to issue
some snow squall warnings. While this activity may impact the I-95
corridor...warm boundary layer may result in possibly a mixture of
rain and snow showers but limited impact on roadways.
3) Strong Winds...
Lastly...the other concern will be for strong winds. The first
concern is tonight across the Cape and Islands. As the strong SSW
low level jet develops this evening into the overnight hours...it
still will be colder than the comparable SST. This will allow for
good mixing and Bufkit soundings indicate the potential for southwest
wind gusts of 40-50 mph across the Cape and Islands. The area around
Buzzards Bay is particularly vulnerable to strong winds in this
setup. Wind Advisory posted tonight for this region.
Across the rest of the region...the main concern for strong winds
will be later Thu morning into Thu evening in the strong cold
advection pattern behind the cold front. A westerly 45 to 55 knot
low level jet will develop at 850 mb and strong cold advection will
allow for excellent mixing. We are thinking this should generate
wind gusts on the order of 35-50 mph. We opted to go with a Wind
Advisory for western/central MA and northern CT. Good mixing on
westerly flow in the cold advection favors high terrain and areas
down wind. These winds may also be enhanced by any snow squalls etc.
Later shifts may need to consider extending
4) Turning Colder Later Thu into Thu night...
Strong cold advection will result in temps beginning to drop later
Thu and especially Thu night. Temperatures should fall into the 20s
Thu night under strong cold advection and will probably see some
upper teens in the high terrain by daybreak. The strong winds will
result in wind chills dropping into the single digits and teens by
early Fri morning.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Key Messages:
* Below normal temperatures and gusty wind on Friday and Saturday.
* Low confidence in a snow shower/squall late Friday night into
early Saturday.
* Weak clipper system passes to the north early Sunday with a snow
shower or two possible for far northern Massachusetts.
* First-half of next week features mild and unsettled conditions.
Friday and Saturday: The low pressure system deepens as it moves
toward the mouth of the Saint Lawrence River, while a surface high
pressure builds across the south/central CONUS. Pressure gradient
builds and leads to gusty west to northwest flow on Friday and
Saturday, gusting between 25 to 35 MPH, below advisory criteria. CAA
ushers an Arctic airmass, with 850mb temperatures crashing, between
-12C and -18C on Friday and then -15C and -20C on Saturday. No
surprise that temperatures remain well below normal with highs in
the 30s and nighttime lows in the teens to low 20s. This period is
largely dry, the west to northwest flow may pick up moisture from
the relatively warmer Great Lakes and cause an isolated snow shower,
similar to what was experienced Tuesday evening. FWIW, the CIPS Snow
Squall Parameter highlight moderate values for squalls late Friday
night or early Saturday morning. At this time have low confidence in
occurrence, but if were to occur may lead to travel impacts, will
have to wait and see what the higher resolution models show once it
begins to cover this period. At this point, did not introduce any
POPs to the forecast as confidence remains low, though could see
those added to the forecast once we are able to get the NAM3KM and
HRRR (models like this) to cover this period in question. Stay
tuned!
Sunday: The one wrinkle in the forecast during the second-half of
the weekend comes from a weak clipper system with limited moisture
passing to our north early to mid-morning. Bulk of the moisture will
be over Vermont and New Hampshire and the greatest forcing is
displaced a bit further north in Quebec. Still, cannot rule out a
snow shower or two for northern Massachusetts, areas along or north
of the Rt. 2 corridor. Temperatures moderate Sunday afternoon to the
upper 30s north and mid 40s south.
Monday to Wednesday: First-half of next week features a warm-up as
the surface high moves over Bermuda and brings deep southwest flow
to our region. Highs return to the low and middle 50s with nighttime
lows in the 30s and low 40s. Additionally, it is a more active
pattern with the next chance for rain late Monday through the
overnight and possibly again Wednesday, but confidence remains low
with the timing given the time frame.
&&
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00z TAF Update...
Tonight through Thursday AM...Moderate Confidence.
Precipitation overspreads the region from west to east this
evening in the 00-06z timeframe. Widespread low end MVFR- IFR
conditions developing with periods of LIFR conditions possible
across the interior overnight. Best chance for lower end
ceilings will be across the interior terminals where precip type
will likely be SN.
Ptype will mainly be snow northwest of I-495 with generally
rain southeast of that region overnight into Thu morning. Ptype
could mix with or change to snow towards the I-95 corridor for
a brief time before the bulk of the precipitation ends Thu
morning. Snow accumulations of 2-6" are expected across much of
the interior with the higher end amounts confined to the higher
elevations. Lower amounts as you go east from Worcester Hills.
Little if any snow accumulations on the I-95 corridor with
precipitation mainly in the form of rain.
SSW winds at 5-15 knots are expected tonight, increasing into
Thu AM with gusts up to 35 kts by 12z. Cape/Islands trend
higher with gusts up to 40 kts by Thu AM.
Thursday PM...Moderate Confidence.
Main batch of precip exits Thurs AM. Conditions should improve
to mainly MVFR with periods of VFR possible. A few rain/snow
showers through the afternoon. Potential for a couple snow
squalls in the afternoon with a brief vis reductions and briefly
higher precip rates.
Winds shift toward the W by afternoon with gusts of 30-40 knots
for the terminals.
Thursday Night...Moderate Confidence.
VFR, with MVFR CIGs across far NW MA and isolated snow shower.
West winds 15-20 knots with gusts 25 to 35 knots.
KBOS Terminal...Moderate confidence in TAF.
Tonight: Some wet snowflakes may occur briefly or mix in with
rain showers through 02z, but confidence is low. Mainly rain
after 02z continuing through early Thursday morning.
Thursday: Main batch of precip exits 13-16z with a few showers
possible behind it through the afternoon. Will see some
improvements in ceilings Thursday morning with periods of VFR
possible in between showers. Chance for brief RA/SN
showers/squalls in the afternoon. Timing/chances lower
confidence due to hit or miss nature of showers.
KBDL Terminal...Moderate confidence in TAF.
Tonight into Thursday: Light snow arrives between 01z/03z with
the main batch of precipitation exiting by 12-14z Thu AM. Brief
improvements in ceilings toward MVFR in the AM in between
showers, even brief VFR possible. Chance for brief
showers/squalls in the afternoon with brief vis reductions and
increased precip rates. Strong SW to W winds with gusts up to 40
kts.
Outlook /Friday through Monday/...
Friday: VFR. Windy with gusts up to 35 kt.
Friday Night through Saturday: VFR. Breezy.
Saturday Night: VFR.
Sunday through Sunday Night: VFR. Breezy.
Monday: Mainly VFR, with local IFR possible. Breezy. RA likely.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
* Gale Warnings tonight through Thu night with 45 knot gusts
Tonight through Thursday night...
Alberta Clipper tracking to our north will induce a strong southwest
LLJ tonight. This will allow SSW wind gusts of 30 to 45 knots to
develop later this evening and especially during the overnight
hours. The strongest of those winds tonight will be across the
southern waters.
This system will result in a strong cold frontal passage across the
region on Thu. Strong cold advection will result in westerly wind
gusts of 35 to 45 knots developing Thu and continuing Thu night.
Gale Warnings posted all waters though this time and seas will be
quite high and rough.
Outlook /Friday through Monday/...
Friday: Low risk for gale force winds with gusts up to 35 kt.
Rough seas up to 11 ft.
Friday Night: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Slight chance of snow.
Saturday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft.
Saturday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft.
Sunday through Sunday Night: Winds less than 25 kt. Local rough
seas.
Monday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Chance of rain, patchy fog. Local visibility 1 to 3 nm.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Wind Advisory from 10 AM to 10 PM EST Thursday for CTZ002>004.
Winter Weather Advisory until 10 AM EST Thursday for CTZ003.
MA...Wind Advisory from 10 AM to 10 PM EST Thursday for MAZ002>004-
008>012-026.
Winter Weather Advisory until 10 AM EST Thursday for
MAZ002>004-008>012-026.
Wind Advisory until 10 PM EST Thursday for MAZ022>024.
RI...Wind Advisory until 10 PM EST Thursday for RIZ008.
MARINE...Gale Warning from 7 AM Thursday to 7 AM EST Friday for ANZ230.
Gale Warning until 7 AM EST Friday for ANZ231>237-250-251-
254>256.
&&
$$
SYNOPSIS...Frank/Dooley
NEAR TERM...Frank/Dooley
SHORT TERM...Frank
LONG TERM...Dooley
AVIATION...Dooley/Mensch
MARINE...Frank/Dooley
Area Forecast Discussion
National Weather Service Cheyenne WY
433 PM MST Wed Dec 4 2024
.KEY MESSAGES...
- Above average temperatures will continue each day through the
end of the week with dry weather expected.
- High winds are increasingly likely for the wind prone areas
Saturday night into Sunday.
- A strong cold front will bring gusty winds, much colder
temperatures, and a chance for snowfall Sunday night into
Monday.
&&
.SHORT TERM /THROUGH FRIDAY/...
Issued at 240 PM MST Wed Dec 4 2024
The Stagnant pattern, that has been observed over the last several
days, continues to hang on another day with the latest upper air
analysis highlighting the upper level ridge slowly coming more
inland from the Western Seaboard to the Intermountain West. Much of
the influence for the limited movement of this ridge has been a
direct related to the upper level features observed off to the east
as the last of the series of upper level closed lows dig southward
from the Canadian provinces to the Great Lakes. Looking at the
surface, latest observations have placed a weak cool front mentioned
in the aviation discussion now across the Nebraska/South Dakota
border and starting to dig south into Northern Wyoming. Similar to
yesterday, conditions throughout the morning and early afternoon
have been relatively mild ahead of the boundary, with temperatures
in the mid 50s for most areas and around 10 degrees colder for the
far western portions of the CWA.
Main forecast concerns over the next 12 to 36 hours focus on the a
series of cool fronts expected to dig across the CWA late this
afternoon and into the early morning hours and again a second cool
front swinging through the area Thursday night into Friday. Focusing
on tonight and tomorrow morning, confidence has continued to
increase throughout the day for the boundary to stall along the
Rockies into the overnight hours, ultimately turning the winds
towards a more favorable direction for upslope flow for areas in
western Nebraska. HiRes models have begun latching onto onto this
solution with areas of patchy fog developing north of Morrill and
Scotts Bluff County and some northwestern extension into Niobrara
with forecast soundings indicating low level moisture across the
aforementioned zones. Went ahead and added patchy fog into the
forecast. However, will need to monitor for freezing fog potentials,
with forecast soundings being on the line for freezing fog.
Throughout the day tomorrow, should be another quieter day with the
daytime highs dropping a few degrees in the Panhandle due to the
stalled boundary. However, temperatures are expected to remain
relatively the same for areas along the I-25 corridor and westward
as another day of northwesterly flow aids in a warm downsloping flow
and some gusty to elevated winds along and east of the Laramie Range.
Next upper level shortwave, which is progged to undercut the main
southwesterly flow, will begin to digging to the southeast Thursday
night into Friday with the flow becoming somewhat split as a closed
low develops just to the south of the Four Corners. Little to no
precipitation is expected with the arrival and passing of the
shortwave as PWATs remain dry and having minimums around -1.5 sigmas
below climatology. Temperatures will also remain relatively the
same, with dry downsloping flow aiding in temperatures hovering
around the low to high 50s for areas along and east of the Laramie
Range and 10 to 15 degrees cooler for areas to the west. Fairly high
confidence for above average temperatures to continue through the
late week, with the NAEFS mean pushing 700mb temperatures in the
climatological 90th percentile further eastward into central and
east Wyoming late Friday afternoon.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 240 PM MST Wed Dec 4 2024
A strong Pacific trough will bring an end to the warm weather
pattern this weekend, but an impactful snow event is looking less
likely.
Warm and dry weather will continue into Saturday as a strong ridge
axis shifts over the Rockies. Downstream amplification of the ridge
ahead of the trough moving into the Pacific northwest and modest
downslope flow will support Saturday bringing likely the warmest
temperatures of the forecast period. Ensemble guidance depicts
average 700-mb temperatures reaching close to +6C, which is above
the 90th percentile of climatology and approaching the 97.5th
percentile. The warmth will be more pronounced east of the Laramie
Range, where widespread mid to upper 50s and possibly a few 60s can
be expected. The arrival of the Pacific trough will bring an abrupt
end to the warm pattern on Sunday. First, winds will increase as
height/pressure gradients build in advance of the trough. Strong
winds in the wind prone areas (Bordeaux in particular) may begin as
early as Saturday morning with considerable MSLP gradients resulting
from falling pressure over the High Plains. However, confidence is
higher for winds Saturday night into Sunday morning, with the
highest probabilities occurring with the maximum pressure gradient
just ahead of the surface cold frontal passage. In-house guidance
depicts a 50-70% chance of high winds during this period thanks to
700-mb winds in excess of 50-knots, surface gradients well above
typical criteria, and 700-mb height gradients sufficiently close.
Elsewhere, expect a morning high Sunday with most guidance showing
the front passing through between 12z and 18Z, and temperatures
dropping through the afternoon hours. Expect gusty northwest winds
behind the front that will likely continue through Monday. Monday
will be significantly colder. 700-mb temperatures plummeting to
around -13C will lead to highs struggling to reach freezing across
much of the area. This precipitation outcome with this system is
still fairly uncertain, but recent guidance has continued to trend
towards the drier scenario. Models have trended to a pseudo-split
trough scenario once again, where a southern vort-max tracks further
south towards the Four Corners while a northern vort-max remains
just to our northeast over the Dakotas. Such a scenario is an
unfavorable lifting profile for most of our area, mainly limited to
just orographics which is not very widespread in northwest flow.
Moisture also looks limited. Ensemble mean precipitable water
values are actually below average for this time of year (which is
already quite low), at less than 0.25" for the entire area. Ensemble
probabilities of 0.1" or greater of QPF are less than 20% for all
valley locations. The resulting most probable scenario would mean a
few light snow showers over the plains bringing a dusting to an inch
or so to some areas, but most accumulation limited to the mountains.
Even in the mountains, ensemble averages are only around 0.25" QPF
supporting a sub-advisory event in the most likely scenario. Current
guidance shows a 20% chance of advisory totals in the Snowy Range
and a 50% chance in the highest peaks of the Sierra Madre. Beyond
Monday, conditions will remain on the cool side. While the ridge
will try to expand again, another shortwave trough arriving around
Wednesday may bring another round of wind and light snow in addition
to replenishing the cold, but confidence is fairly low at this lead
time.
&&
.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 433 PM MST Wed Dec 4 2024
The main aviation concern this evening and overnight will be the
potential for low CIGs and fog across portions of the Nebraska
panhandle. The HREF currently shows about 30 percent probabilities
for MVFR CIGs in the northern Nebraska panhandle, including KCDR.
The HRRR is a bit more excited about fog developing in the southern
panhandle, possibly affecting KSNY. Even if MVFR CIGs do not occur,
expected low stratus to move into KCDR within the next few hours.
Southeast Wyoming terminals can expect a quiet overnight.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...MRD
LONG TERM...MN
AVIATION...SF
Area Forecast Discussion
National Weather Service Gray ME
1046 PM EST Wed Dec 4 2024
.SYNOPSIS...
A complex series of upper level troughs will cross the forecast area
tonight and Thursday with snowfall across the interior and a mix of
rain and snow closer to the coast. This system will be a followed by
a very cold airmass and gusty winds to finish up the workweek and to
start the weekend.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
1040 PM...One burst of precip, associated with the front of the
low level jet is moving through attm. There may be a little
break for an hour or two before the steadier precip moves back
in. Coastal areas from KPWM south, have bumped temps into the
mid to upper 30s with Tds mostly in the low 30s. I think these
may drop off a bit once the S jet exits after midnight, but I
think these does further limit the chance of accumulating in
these areas.
745 PM...Based on latest obs, specifically Td depressions, and
meso models, I`ve nudged back arrival time of the accumulating
snow by an hour or two across much of the CWA. Should work into
the NH mtns first then the ME mtns and the rest of NH by around
midnight, and then quickly over spread ME post-midnight. This
may reduce snow amounts by a hair, but unlikely will affect
overall impact.
Shortwave ridging is currently overhead per latest RAP analysis,
but this will shift to the east through tonight as low pressure
currently just north of the Great Lakes heads our way. This has
has given a mostly sunny day up to this point, but high clouds
are already pushing into western zones, and these will continue
to increase over the area while lowering and thickening as the
low pressure approaches.
Snow will begin to overspread the region this evening and
persist through the night and is expected to increase in
intensity after midnight as we`ll be in the left exit region of
a 250mb jet streak and forecast soundings also advertising a
small amount of CAPE. Precipitation type favors snow across the
interior with more of a rain/snow mix closer to the coast (even
a period of mostly rain). There is still uncertainty on where
this transition occurs and how far inland it will progress with
the increasing southerly flow. Still, what snow falls is
expected to accumulate, likely resulting in slick roadways and
poor visibility for the Thursday morning commute, even in the
lower amounts outside the Winter Weather Advisory.
All in all no major changes to the forecast with 3-6" across
the Advisory areas (a bit higher in the mountains), but
portions of some counties not in the Advisory could still
approach these totals, especially northern Androscoggin and
northern Kennebec county. However, the zone/county average does
not warrant the expansion at this time. Taking a glimpse at the
incoming 18Z HRRR and NAMnest indicates the rain/snow line may
not progress quite as far inland...and this will have to be
monitored further as amounts may need to be adjusted upward.
The last thing to mention is a period of strong, gusty winds
tonight and very early Thursday, especially along the coast but
moreso the Midcoast where a 45-50kt low-level jet could bring
gusts to around 45 mph for a brief period overnight. For this
reason, have put out a Wind Advisory for Knox and Coastal Waldo
counties.
Guidance continues to advertise precip rates coming down across
southern and central New Hampshire by mid-late morning and then
closer to the late morning or early afternoon hours across
western ME as the primary forcing shifts east. What falls after
is expected to be lighter in nature, but areas that do see
mostly rain or a mix could then see a switch back to light snow
as temperature profiles cool. One more thing to watch for is
that forecast soundings do depict some clearing and steepening
lapse rates across NH, and as the upper trough swings through,
additional snow showers or even a squall or two could develop.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
The region will transition more to upslope flow Thursday
evening/night as the low pressure deepens while lifting toward the
Canadian Maritimes. This will keep snow showers going in the
mountains with additional light accumulations, and steep low-
level lapse rates/high Froude numbers favor some of these making
it downwind of the mountains. Winds also become gusty with the
pressure gradient continuing to tighten with forecast soundings
supporting 25 to 35 mph, sending wind chills down into the
teens toward daybreak Friday.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
1040 PM update...Forecast looks reasonable through Sunday, but
models become very divergent, even withing own their own
ensemble members. The 12Z operational Euro shows a weak wave
moving through Mon or Mon night, with generally dry conditions
Tue/Wed, and because that`s proven to be the model of choice
will lean in that direction. The front lingers offshore until a
wave moves in later in the week, and with fast zonal WSW aloft
this suggests more in the way of subsidence on the NW side of
the front. Chance POPS were kept into Tue night, given that
there are enough EPS ensemble members showing some precip to
ignore the possible of of a wave traveling NE along the front
around midweek. 850 MB temps do bump up to around +5 C Tue-Wed,
o temps warm into the 40s with maybe some places hitting 50F.
3 PM...Low pressure continues to intensify and exit through the
Canadian Maritimes on Friday as high pressure builds towards
New England. A strong northwesterly gradient will be building
through a deep layer. With sufficient cold air advection and
ample mixing, expect very gusty winds to occur during the day
with a few 35 kt+ peak winds.
It will be chilly with quite a few upslope clouds and possibly a
flurry or two in the mountains. Temperatures will only make it into
the teens north to 20s south.
Over the weekend it will remain chilly across the region with below
normal temperatures for this time of the year. Most of the
clouds and precipitation will be hung up in the mountains on
Saturday with clouds across the entire region on Sunday as a
warm front crosses the region. Snow showers can be expected
despite a moderating regime.
12Z operational models and ensemble solutions suggest a slow moving
and complex weather system will approach the region on Monday with
pops increasing for snow during the day across much of the
region except the coastline. S second piece of energy will
track to our west, allowing a frontal system to become hung up
along the east coast until midweek. This may allow for
prolonged periods of rain and snow which will be very dependent
on the progressiveness of the boundary along and near the coast.
There is considerable uncertainty in this scenario as other
ensembles suggest more progressive solutions to the system.
&&
.AVIATION /04Z THURSDAY THROUGH MONDAY/...
Short Term...VFR for a little while longer, but conditions will
deteriorate to IFR this evening and tonight, possibly LIFR at
some terminals, as precipitation overspreads the area. This will
be mainly snow inland and more of a rain/snow mix or even
mainly rain for the coastal sites. These restrictions will be
primarily tonight through Thursday morning, and then improving
conditions are expected through Thursday afternoon with most
sites returning to VFR. Mostly VFR Thursday night with the
exception of HIE and maybe LEB, where snow showers will also
remain a possibility. There is also a low chance of snow showers
south of the mountains Thursday.
Winds: A period of southerly gusts to 25 to 30 kt is possible
for the coastal terminals tonight (up to 35 kt at RKD) and then
westerly winds will increase late Thursday into Thursday night
with gusts again 25 to 30 kt, possibly up to 35 kt.
Long Term...Mainly VFR conditions expected Friday and into the
weekend with the exception of upslope low cloudiness in the
mountains. On Sunday, all areas will lower to IFR and LIFR in
ceilings during the day with rain and snow. More mixed precipitation
with persistent IFR conditions during the period Monday through
Wednesday.
&&
.MARINE...
Short Term...There will be deteriorating conditions across the
waters this evening and tonight as southerly flow increases
ahead of a low pressure center that will pass just north of the
waters Thursday before lifting into the Canadian Maritimes
Thursday night. Southerly gales are likely ahead of the low
tonight and Thursday over the eastern waters/Penobscot and then
across all the waters Thursday evening and Thursday night as
westerly flow increases with the deepening low.
Long Term...Gale force conditions may remain over the waters as the
extended forecast starts on Friday. Winds back to the southwest and
diminish slightly over the weekend but still remain relatively
gusty.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Winter Weather Advisory until noon EST Thursday for MEZ007>009-
012>014-033.
Wind Advisory until 7 AM EST Thursday for MEZ027-028.
NH...Winter Weather Advisory until noon EST Thursday for NHZ001>009-
011-015.
MARINE...Gale Warning until 7 PM EST Friday for ANZ150>152.
Small Craft Advisory until 4 PM EST Thursday for ANZ153-154.
Gale Watch from Thursday afternoon through Friday evening for
ANZ153-154.
&&
$$
SYNOPSIS...
NEAR TERM...Cempa/Combs
SHORT TERM...Combs
LONG TERM...Cannon
AVIATION...
MARINE...
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
932 PM EST Wed Dec 4 2024
.SYNOPSIS...
Well below normal temperatures will continue through the end of
the week. A potent area of low pressure will drag a strong cold
front across the area tonight into Thursday. This brings
mountain snow, strong gusty winds, and colder temperatures to
the area. High pressure returns Friday into the weekend, which
will bring a gradual warming trend back towards normal
temperatures. Another frontal system approaches the area early
next week which brings increasing chances of rain.
&&
.NEAR TERM /THROUGH THURSDAY/...
Evening update: The main update to the forecast this evening
has been to introduce mixed snow/sleet showers to the forecast
across the West Virginia Panhandle, Shenandoah Valley, and
northern Maryland. Mixed sleet and snow has overspread those
locations over the last few hours as a push of warm advection
occurs aloft. The 00z IAD sounding shows a warm nose present
around 800 hPa that is responsible for the mixing. The sounding
also shows strong veering of winds and associated implied warm
advection in the 925-800 hPa layer. Model guidance indicates
that this push of warm advection should peak in the next hour or
so and then gradually subside through midnight. Current
expectation is for ongoing activity across the WV Panhandle,
Shenandoah Valley, and northern Maryland, to make a bit more
southeastward progress before dissipating as warm advection
starts to weaken. Such a progression would keep the
precipitation this evening out of the immediate DC area, but
some mixed sleet/snow may briefly make it into the northwestern
suburbs, and potentially Baltimore. Model guidance has really
struggled with the evolution of this activity, so we`ll need to
monitor trends and make further adjustments to the forecast
accordingly. In locations that do see precipitation, a quick
coating to a half of an inch of primarily sleet may be possible.
There should a brief lull to the east of the mountains for a few
hours after midnight, but precipitation will start to pick up in
the mountains. The heaviest precipitation in the mountains still
looks to be during the second half of the night, when snowfall
rates of 1-2 inches per hour may be possible at times.
The system`s cold front will sweep eastward across the area
during the second half of the night. The front should reach the
Alleghenies by around 2 AM, and eventually the Bay shortly
after sunrise. A narrow convective line with heavier
precipitation may form immediately along the front as it
progresses eastward. Such a line would progress from the
Alleghenies around 2 AM to the vicinity of the Blue Ridge
around 4 AM, and then toward the Bay around 6 AM. Showers may
linger for a few hours behind the front, but strong cold/dry
advection should dry the column out by mid-late morning,
bringing any leftover precipitation to the east of the mountains
to an end before noon.
A key forecast question that remains is whether the
precipitation to the east of the mountains along/ immediately
behind the front will fall in the form of rain or snow. The 00z
HRRR favors most of this precipitation falling in the form of
rain as the front moves through, with the potential exception
of higher elevations in Frederick and Carroll County, where a
Potential Winter Commuting Hazard Statement remains in effect
for tomorrow morning. The 00z 3 km NAM on the other hand, has
more of the precipitation falling as snow. Surface temperatures
should be in the in the high 30s to near 40 immediately ahead of
the front, but dewpoints will be near 20. If precipitation is
heavy enough, wet bulb effects may drive temperatures to down
near (but likely just above) freezing. The initial temperatures
near freezing will likely be hard to overcome, but there`s still
a potential (albeit unlikely) scenario where snow could
accumulate well east of the mountains tomorrow morning during
the morning commute. We`ll continue to monitor trends through
the night, and update the forecast accordingly. Previous
discussion follows...
Summary of headline changes...
Have held off on any upgrades to High Wind Warnings over some
of the higher elevations, as the highest probabilities for 58+
mph gusts are within the ongoing Blizzard Warning (which covers
the wind threat).
Winter Weather Advisories have been issued just east of the
Blizzard Warning for some of the other Allegheny/Potomac
Highland zones. After a lull Thursday afternoon, additional snow
shower activity is possible Thursday night (amounts generally 1
coating to 3 inches, though some 12z hi-res guidance indicates
potential 3-4 inch amounts). Despite the bulk of heavier snow
being done by early Thursday afternoon, lingering high winds
could result in reduced visibility and power outages well into
Thursday night, especially given the potential for a second
round of additional snowfall.
The potential also exists for snow showers/squalls during the
morning commute into the metro areas. Temperatures should be far
enough above freezing to limit accumulation in the immediate
I-95 corridor, but colder temperatures over the northwest
suburbs (especially some of the higher hills and into the
Catoctins) could prove treacherous. A Special Weather Statement
for a potential commuter hazard has been issued for Frederick
and Carroll Counties where the potential for slicks roads is
highest.
In the wake of the front, very windy conditions and much colder
temperatures will likely drop wind chills to around 10 to 20 below
zero Thursday night near and above 3000 feet elevation over the
Allegheny Front. A Cold Weather Advisory has been issued for
these areas from 7 AM Thursday to 7 AM Friday.
Meteorology overview...
By this evening, the parent upper trough will be tracking
eastward across Lake Michigan toward the Lower Great Lakes. At
the same time, the attendant cold front is forecast to push
across the Ohio Valley toward western Pennsylvania. Robust
ascent and rapid cooling of the column will ensure any mixed
precipitation over the mountains quickly turns over to snow.
However, a wave of weak warm advection could result in some
mixed precip or spotty freezing rain this evening over the
highest elevations of the Alleghenies.
Wind fields at the top of the mixed layer over the mountains
sit between 40 and 55 knots with much of this air being
convectively mixed down to the ground. Snow squalls, areas of
blowing snow, and near whiteout conditions are all expected
tonight into portions of Thursday. Travel is likely to be
very dangerous and not recommended. Timing the front from
upstream, the heaviest snowfall rates (perhaps 1 to 2 inches per
hour with ample CAPE/lift/moisture in the DGZ), look to cross
the Appalachians between 3 AM and 9 AM.
High-resolution models continue to support bringing some of
these squalls downstream toward the metros by daybreak Thursday.
Despite somewhat marginal surface temperatures that sit in the
upper 30s, dew points in the mid/upper 20s should support ample
wet-bulbing effects. These resultant wet-bulb temperatures
would sit in the low/mid 30s and support a changeover to snow
showers in many spots. A quick dusting of snow is possible
during the pre-dawn hours into rush hour on Thursday over the
northwest suburbs of DC/Baltimore, especially over the higher
hills of Frederick and Carroll County. However, all of this
will depend on if these squalls make it that far east, and
whether the intensity of showers would support any light
accumulations further south and east. The progressive nature of
this activity should help usher any residual showers out by the
mid/late morning. However, upslope-driven snow showers likely
persist over the Alleghenies through parts of the day.
The other aspect of this powerful system is the wind and
associated low wind chills. Model soundings continue to show
mixing up to around 850-800 mb which is where around 40 to 55
knots of wind sits. A blustery westerly wind should be rather
effective at mixing some of this higher momentum air down to the
surface. Thus, wind gusts during the mid-morning to afternoon
hours likely peak in the 45 to 55 mph range. A few gusts near 60
mph are possible (1) over higher elevations, and (2) north of
US-50/I-66, but confidence is not high enough in frequent or
persistent gusts to upgrade to a High Wind Warning just yet.
Considering the wind chills, the Allegheny Front should see
values in the negative teens most of the day and night. Across
the rest of the area, wind chills will be in the single digits
and teens heading into Thursday night. The actual high
temperature for Thursday may occur just after midnight with
mainly upper 20s to 30s expected during the day (teens to mid
20s for the mountains, and lower 40s near Fredericksburg/S MD).
&&
.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
Trailing vorticity maxima within the cyclonic flow aloft will
continue to push across the area into Thursday night. These
disturbances are likely to trigger additional snow shower
activity along the Allegheny Front. Recent trends have been
upward, but moisture is relatively shallow. West-northwesterly
winds stay elevated through the night with gusts up around 20 to
25 mph, locally a bit higher along the Alleghenies. This ushers
wind chill temperatures into the negative single digits and
negative teens in the mountains, to the single digits and teens
elsewhere.
Aside from some residual morning snow showers along the
Alleghenies, Friday will yield a dry day across the forecast
area. Well below average temperatures are likely with highs only
in the upper 20s to 30s, with teens to 20s for mountain
locations. Northwesterly winds are expected to be blustery
through the day given a tight gradient formed by a deep low near
Newfoundland and a strong high pressure system across the
Ozarks. Afternoon gusts could reach 20 to 30 mph which will
yield some colder wind chills. The mentioned dome of high
pressure eventually settles to the southwest of the Mid-Atlantic
states. Winds decrease into Friday night with another cold night
on tap. Forecast lows are in the teens to low 20s, perhaps a few
degrees higher around D.C., Baltimore, and over far southern
Maryland.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
A broad trough of low pressure will flatten during the day on
Saturday. High pressure will build overhead then move east later
Saturday and into Sunday. Dry conditions are expected on both
Saturday and Sunday. Temperatures will be below average Saturday
with highs near or around 40. Temperatures will be near average
Sunday with highs in the lower 50s for the most part. Lows
Saturday night will be in the lower to middle 20s, while lows
Sunday night will be several degrees milder and dropping down
into the middle 30s.
A return flow around the west side of the high will bring milder air
northward Sunday night through Tuesday. Along with the increase in
temperatures to above to much above average levels, rainfall
chances will also be on the increase through the period. Highs
Monday will be in the middle to upper 50s. Highs Tuesday will be
in the lower to middle 60s.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
VFR conditions are expected through this evening in advance of
a potent cold front which races through during the overnight
hours. Before this occurs, southerly winds pick up with gusts
up to 20 to 30 knots.
Any shower activity associated with the front is initially
confined to the Alleghenies where blizzard conditions become
likely overnight. There is a potential for squalls that push
eastward toward the area terminals between around 4 AM and 9 AM
Thursday. Depending on the intensity of these showers and
surface temperatures, a quick dusting of snow is not out of the
question, though the probability for accumulating snow on
runways in the metros looks low. Regardless, this would come
with brief restrictions. Then the focus shifts over to the
strong wind field which overspreads the region. A robust
westerly wind will likely raise Thursday`s gusts to around 35 to
45 knots, with some drop off into the night (20 to 25 knots). A
tight pressure gradient continues into Friday which supports
another day of elevated winds. Although conditions will be VFR,
northwesterly gusts of 20 to 30 knots are expected before waning
into the night.
VFR conditions are expected through late Sunday. MVFR
conditions could arise Sunday night with some light rain moving
in across the region. Winds northwest becoming southwest 5 to 10
knots Saturday and continuing southwest into Sunday.
&&
.MARINE...
A gusty southerly wind will raise gusts into the 20 to 30 knot
range through the evening. Further increases are tonight across
the southern half of the Chesapeake Bay down into the lower
tidal Potomac River. With the potent cold front crossing the
waters on Thursday morning, all waters will see gale conditions
with gusts up to around 45 knots. A few storm force gusts are
possible (1) with initial frontal passage around mid morning,
and (2) through the afternoon sporadically. Hazardous marine
conditions persist through Thursday evening. As such, Gale
Warnings may need to get extended in time by a few hours or so.
Winds remain elevated into Thursday night and Friday as winds
turn more northwesterly. Gusts will regularly top out in the 25
to 30 knot range, accompanied by a few random gale caliber
gusts. However, these should be more intermittent in nature.
Eventually winds return to below advisory levels by Friday night
as gradients weaken.
No marine hazards Saturday through Sunday night. Winds becoming
southwest around 10 knots gusts 15 knots Saturday through Sunday
night.
&&
.FIRE WEATHER...
Despite the cold temperatures, strong winds combined with
rapidly falling humidity and a lack of significant recent
precipitation could raise the threat of rapid fire spread on
Thursday, particularly during the midday into afternoon hours
from the Fredericksburg into southern Maryland. Limiting
factors would be potential morning precipitation in the form of
spotty and brief rain/snow showers, as well as cooler
temperatures generally in the 30s to around 40.
&&
.TIDES/COASTAL FLOODING...
The main period of interest for coastal flooding concerns will be on
Wednesday evening into Thursday as a powerful cold front pushes
across the area. Expect a marked increase in water levels ahead of
this system, which is likely to push the more sensitive locations
into Action around the time of high tide.
In the wake of this boundary, a blustery westerly wind will rapidly
move into the area on Thursday. This will result in a rapid decrease
in tidal anomalies Thursday into Friday. During this timeframe,
blowout tides will become a concern. Tidal anomalies of one to two
feet below normal are in the forecast at this time across most of
our forecast points.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Wind Advisory from 9 AM to 6 PM EST Thursday for DCZ001.
MD...Small Craft Advisory until 6 AM EST Thursday for MDZ008.
Gale Warning from 6 AM to 7 PM EST Thursday for MDZ008.
Wind Advisory from 9 AM to 6 PM EST Thursday for MDZ003>006-
008-011-013-014-016>018-501>508.
Blizzard Warning until 3 PM EST Thursday for MDZ001.
Winter Weather Advisory from midnight tonight to 3 PM EST
Thursday for MDZ501.
VA...Wind Advisory from 9 AM to 6 PM EST Thursday for VAZ025>031-
040-053-054-501-503>508-526-527.
Winter Weather Advisory from midnight tonight to 3 PM EST
Thursday for VAZ503.
Cold Weather Advisory from 7 AM Thursday to 7 AM EST Friday
for VAZ503.
WV...Wind Advisory from 9 AM to 6 PM EST Thursday for WVZ050>053-
055-502>504-506.
Blizzard Warning until 3 PM EST Thursday for WVZ501-505.
Winter Weather Advisory from midnight tonight to 3 PM EST
Thursday for WVZ503.
Cold Weather Advisory from 7 AM Thursday to 7 AM EST Friday
for WVZ501-505.
MARINE...Small Craft Advisory until 6 AM EST Thursday for ANZ530-531-
535-536-538-539-542.
Gale Warning from 6 AM to 7 PM EST Thursday for ANZ530-531-535-
536-538-539-542.
Wind Advisory from 9 AM to 6 PM EST Thursday for ANZ530.
Gale Warning until 7 PM EST Thursday for ANZ532>534-537-540-
541-543.
&&
$$
SYNOPSIS...BRO/DHOF
NEAR TERM...BRO/DHOF/KJP
SHORT TERM...BRO/DHOF
LONG TERM...KLW
AVIATION...BRO/KLW/DHOF
MARINE...BRO/KLW/DHOF
FIRE WEATHER...
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Marquette MI
652 PM EST Wed Dec 4 2024
.KEY MESSAGES...
- Heavy lake effect snow bands will continue in the northwest
belts this afternoon, shifting to the northerly belts late
tonight into Thursday. The combination of heavy snow and
blowing snow will lead to dangerous travel conditions and
near-zero visibility in heavy snow bands. Winter Storm
Warnings and Winter Weather Advisories are in effect.
- Blustery north-northwest winds, gusting up to 30-45 mph are
expected this evening into Thursday morning, especially near
Lake Superior and in the Keweenaw. During this period, wind
chills drop to near or just below zero for much of the central
and west.
- Storms to 50 knots develop across the entire lake this
afternoon through Thursday morning.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 248 PM EST Wed Dec 4 2024
RAP Analysis shows a closed 500mb low over northwest Ontario
embedded within large-scale troughing over eastern North America,
contrasted with ridging over the Pacific Northwest. This translates
at the surface to a 992mb clipper low just northeast of Lake
Superior and a 1035mb high over Saskatchewan. This is leading to a
tight pressure gradient forming, with 995mb over Sault Ste Marie and
1007mb over Duluth and tightening. Gales are already being observed
at the West Superior Buoy and the Rock of Ages Lighthouse near Isle
Royale. These winds will continue to build throughout the evening,
with the Euro ensemble showing over 60% probabilities of 50+ kt
gusts over much of Lake Superior tonight. This in conjunction with
the snowfall will lead to blowing snow threats especially near the
Lake Superior lakeshore, but also could penetrate further inland
(20%), reducing visibility and causing drifting snow on roadways.
Northwest to southeast bands of snowfall are beginning to set up as
shown on the KMQT radar. At 19Z, the cold front from the clipper low
was draped across Luce and Schoolcraft County, with winds continuing
to veer northwesterly and eventually northerly as the low pushes
east. Snowfall rates will be quite variable with this system, with
HREF probabilities of 1"/hr rates only locally 10-30% until around
07Z Thursday, when a subtle shortwave will provide further lift and
bring over 50% probabilities of 1"/hr snowfall rates over much of
the north-facing terrain aligned near Lake Superior before coming
back to lesser rates by 12Z. 6-hourly PMM QPF is between 0.1 and
0.25 inches throughout tonight, combining with snow ratios in the
upper teens to 1 will lead to snow totals in the 2-6 inch range
except for lower in the south-central and higher in local areas of
high terrain where snow totals could (25%) eclipse 8 inches.
&&
.LONG TERM /THURSDAY THROUGH WEDNESDAY/...
Issued at 333 PM EST Wed Dec 4 2024
By Thursday morning, the upper level wave will have translated
southeast into the lower Great Lakes, continuing strong northerly
CAA over Lake Superior. 850mb temps near -16 to -13C atop Lake
Superior surface temperatures averaging ~6C will create delta-T
values upwards of 20C and lake induced ELs near 5-7k ft, possibly
upwards of 10k ft in connection with Lake Nipigon preconditioning
and convergence banding. This will continue strong LES showers as
winds veer to the north wind snowbelts late Wednesday night into
Thursday morning. Combined with gusts upwards of 45-50 mph, the
morning commute could be quite dangerous, especially near the
lakeshores where visibility will drop to near zero under the
heaviest snowbands. The current CAM suite has a solid handle on a
heavy Nipigon connection band meandering eastward from the Keweenaw
into Marquette county between 15 to 18z. Under this band, snowfall
rates could push easily 1-1.5 in/hr (per 12z HREF).
Meanwhile, 1038mb high pressure descends southward into the High
Plains, nudging into western Lake Superior late Thursday afternoon.
With this, dry air will work to lower inversion heights from west to
east through Thursday evening. Winds will begin to lessen as the
parent low pressure continues departing east, reducing the blowing
snow threat across much of the central UP. Flow over Lake Superior
backs to the northwest, refocusing heaviest snowbands over the east
half of the UP through the evening. Come Friday morning, snow
accumulations across the central north snowbelts could reach 6-10
inches with isolated areas close to a foot where dominant snowbands
have the longest residence time. Given the blustery northerly
winds, lake effect snow is likely to reach portions of the
southern UP, reaching portions of Menominee county where 1-2
inches is possible.
A weak mid-level clipper within broad northwest flow aloft
turns winds back out of the west Friday, supporting a brief
period of west/nw lake effect snow where a few inches could
accumulate in the far east and Keweenaw.
Looking ahead, there is a brief pattern shift on Saturday to
quasi- zonal flow for Sunday into Monday with WAA throughout
brings a brief warm up to the region. Highs Saturday - Monday
increase to the 30s, potentially reaching 40 inland with lows
mainly in the 20s. Ensemble spread is still significant Sunday
into next week, but the active period is progged to continue
with multiple systems quickly moving into the Great Lakes
region. A return of some rain to the central and eastern UP is
possible with the early next week system before a colder airmass
returns.
&&
.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 630 PM EST Wed Dec 4 2024
Expect deteriorating conditions at all 3 TAF sites tonight in
lake effect snow and considerable blowing snow from n-nw winds
gusting to 35 knots or higher at times. Prevailing IFR to LIFR
flight conditions could at times be reduced to airport minimum
visibility in snow and blowing snow at CMX and possibly at SAW
later tonight. Look for improvement to MVFR conditions at IWD
and CMX by Thursday late morning/early afternoon as ridging and
drier air from the west begin to taper off the snow and winds
weaken, slightly reducing the blowing snow. Improvement to MVFR
will be delayed until probably mid to late Thursday afternoon
at KSAW as winds weaken and back more to the nw.
&&
.MARINE...
Issued at 333 PM EST Wed Dec 4 2024
A clipper low pressure northeast of Lake Superior is marching a cold
front across the east half of the lake this afternoon. Behind the
cold front northwest gales will increase to northerly storm force
gusts 45 to 50 knots across portions of the west lake and
further into the central and east-central lake overnight into
Thursday morning. Waves continue to build up to 10-16 ft. Wave
heights over the west hold steady tonight and increase up to
15-20 ft over the east by Thursday morning. Highest waves are
expected between Stannard Rock, Marquette, and Grand Marais.
Waves then fall below 4 ft in the west Thursday evening and
Friday morning in the east. Across the lake, waves between 3-6
ft are expected on Friday. Waves then remain at or below 4 ft
the rest of the weekend. With the cold airmass surging in
tonight and increasing wave heights, some freezing spray is
expected. The main area of concern for freezing spray is the
west half of the lake this afternoon through tonight. Storm
force gusts slacken to northwest gales Thursday afternoon,
weakening below 35 knots by 18z Thursday, and further below 25
knots through the evening into early Friday.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Storm Warning until 1 PM EST /noon CST/ Thursday for
MIZ001-003-010-013.
Winter Storm Warning until 7 AM EST /6 AM CST/ Thursday for
MIZ002-004-009-084.
Winter Storm Warning until 7 PM EST Thursday for MIZ005>007-
014-085.
Lakeshore Flood Advisory from 3 AM to 1 PM EST Thursday for
MIZ005-006.
Winter Weather Advisory until noon CST Thursday for MIZ011.
Lake Superior...
Gale Warning until 1 PM EST Thursday for LSZ251-267.
Storm Warning until 4 AM EST /3 AM CST/ Thursday for LSZ162-
241-242-263.
Heavy Freezing Spray Warning until 7 AM EST /6 AM CST/
Thursday for LSZ162-240>244-263-264.
Gale Warning until 7 AM EST /6 AM CST/ Thursday for LSZ240.
Gale Warning until 7 PM EST this evening for LSZ243>245-249-
250-264>266.
Storm Warning until 7 AM EST Thursday for LSZ243>245-249-250-
264>266.
Heavy Freezing Spray Warning until 7 AM EST Thursday for
LSZ245>248-265-266.
Gale Warning until noon EST Thursday for LSZ246>248.
Lake Michigan...
Gale Warning until 1 PM EST Thursday for LMZ221-248-250.
&&
$$
SHORT TERM...GS
LONG TERM...BW
AVIATION...Voss
MARINE...BW
Area Forecast Discussion
National Weather Service Pocatello ID
212 PM MST Wed Dec 4 2024
.SHORT TERM...TODAY THROUGH THURSDAY NIGHT...
High pressure and attendant quiet, low-impact weather continue.
While most guidance does not advertise fog Thursday morning, we did
see development in a few areas this past morning, and max RH values
look very similar tonight in this stagnant, stable pattern. Thus,
leaned on some hints of development in the HRRR (especially in the
lower and upper Snake Plain areas) and broadbrushed slightly to add
just patchy morning freezing fog to the forecast.
.LONG TERM...Friday through Wednesday. Models remain consistent
with portrayal of shortwave feature moving through for the
weekend. Weak dry shortwave on Friday helps to lead the way for
stronger trough to break down the blocking high Saturday into
Sunday. Models have slowed down onset of precipitation slightly,
trending later in the day Saturday, and ensemble blends reflect
this slower timing. Bulk of the precipitation falls Saturday night
through Sunday before decreasing over the eastern highlands Sunday
night or Monday morning at the latest per current GFS/ECMWF
timing. Moisture remains limited for the event, so 72-hr ensemble
means through mid-day Monday carry a meager 2-5" for higher
elevations mainly Sawtooths and Big Hole/Teton areas and a
trace-1" for the Snake Plain from American Falls north. Low end
25% probabilities (3 in 4 chance of exceedance) are far more
limited, only an inch or two for the higher elevations of the
central mountains and eastern highlands. High end 90th percentile
(1 in 10 chance of exceedance) are more generous with some of the
higher elevation mountain ranges, with 4-around 7" of snow. The
higher end probabilities also carry about an inch of snow for the
I-15 corridor from Pocatello to Idaho Falls. All that to say, this
is not expected to be an impactful event for East Idaho. Ridge
of high pressure returns for Monday/Tuesday. This should be a
colder pattern on the northerly flow side of the ridge. Model
blends support highs around freezing, some 10-15 degrees colder
than recent days. DMH
&&
.AVIATION...
High pressure and attendant quiet, low-impact weather continue, with
NBM and MOS guidance supporting some of the lightest winds you can
get in Idaho. Have kept all sites at 4kts or less in the TAFs,
except slightly higher at KSUN with their usual diurnal wind
evolution. While most guidance does not advertise fog Thursday
morning, we did see development in a few areas this past morning
(briefly affecting KPIH), and max RH values look very similar
tonight in this stagnant, stable pattern. Thus, leaned on some hints
of development in the HRRR and broadbrushed slightly to add just
patchy morning freezing fog to the forecast. Best chance for impacts
will be 11-18z/4-11am at KPIH similar to this morning, but
confidence in direct LIFR impacts at the airport is low for now
given a holistic look at our guidance sources. Will hint at this,
at least nearby potential for now via 6 SM BR VCFG with SCT002.
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Shreveport LA
930 PM CST Wed Dec 4 2024
...New UPDATE...
.UPDATE...
Issued at 914 PM CST Wed Dec 4 2024
Updated PoPs/WX and added areas/patchy fog to the overnight.
&&
.SHORT TERM...
(This evening) Issued at 914 PM CST Wed Dec 4 2024
The last of the measurable showers are easing out of east TX with
still widespread coverage east of I-49. This is a little faster
now as things will wrapping up shortly after midnight for our
eastern zones. Air temps remain chilly area wide with mid 40s
north and right around 60 on our southern tier of counties and
parishes. Most sites along I-20 are in the middle with low to mid
50s, and dew points within a degree or two. As the rain areas
continue to slide eastward, we can expect fog development to
continue well past midnight. Areas to our west are experiencing
such fog at a mile to a few with no expectation for dense fog. In
fact, the models are showing an increase in the the northerly
winds before daybreak and this will help to thin the fog early in
the day for a change. The HRRR depicts this likelihood very well
as the last of the showers to develop along the front which will
be moving southward and not east like most of this overrunning
activity has all day. Overall, the morning commute should be
mostly cloudy skies and cool temps with a northerly wind chill.
/24/
&&
.LONG TERM...
(Friday through next Tuesday)
Issued at 252 PM CST Wed Dec 4 2024
Upper level steering ahead of a cutoff low over northern Mexico and
the Desert Southwest will sustain an unsettled and deeply soggy
pattern to continue through the weekend and into early next week,
with near-areawide PoPs persisting through the early hours Monday.
The latest guidance looks to keep the ArkLaTex dry through the
daylight hours Friday, returning showers to our east Texas zones
shortly after sundown. These showers will overtake the region
overnight, continuing into the day Saturday while increasing in
coverage and confidence and persisting through the weekend and into
early next week. Some guidance has hinted at surface temperatures
being cold enough overnight Friday into Saturday to support brief,
isolated non-liquid precip in our elevated northern zones, but
confidence in timing is not yet high enough to allow these
conditions to prevail. Will monitor closely through the coming days.
As the aforementioned low begins to open up into a longwave trough
and push eastward, Monday looks to see gradual clearing from
northwest to southeast, through a renewed impulse of moisture will
maintain rainfall for our central Louisiana parishes to close out
this extended forecast period. The latest QPF values for the week
ahead depict totals ranging from an inch and a half northwest to
between 3 and 5 inches along and south of the I-20 corridor in Texas
and Louisiana. Temperatures will remain cool to close out this week
with a warm up late this weekend continuing into early next week
before another cold front returns us to seasonable temperatures by
the middle of the week.
SP
&&
.AVIATION...
(00Z TAFS)
Issued at 542 PM CST Wed Dec 4 2024
Showers remain draped across the region, where they will decrease
in coverage over the next six-ish hours. However, skies will
remain reduced, with IFR CIGS likely to continue into the morning
hours. However, skies should begin to mix out between 12-15z, with
VFR skies returning past 05/21z.
/44/
&&
.SPOTTER INFORMATION STATEMENT...
Issued at 153 AM CST Wed Dec 4 2024
Spotter activation is not expected at this time.
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 47 57 31 50 / 80 0 0 0
MLU 46 53 26 47 / 100 0 0 0
DEQ 35 52 24 48 / 10 0 0 0
TXK 41 55 27 49 / 30 0 0 0
ELD 39 51 23 47 / 80 0 0 0
TYR 47 57 33 52 / 30 0 0 10
GGG 46 58 30 50 / 50 0 0 0
LFK 52 60 34 53 / 60 10 0 10
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
SHORT TERM...24
LONG TERM....26
AVIATION...44