Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/05/21
Area Forecast Discussion
National Weather Service Denver/Boulder CO
849 PM MST Sat Dec 4 2021
.UPDATE...
Issued at 823 PM MST Sat Dec 4 2021
Satellite imagery shows areas of high clouds moving into northeast
Colorado this evening. Very minor adjustments were made to cloud
cover to reflect latest observations.
A High Wind Warning is in effect from 11pm tonight through 11am
Sunday for the mountains/foothills and the latest model/ensemble
data continues to support this. RAP analysis shows increasing NW
flow aloft this evening. Model cross-sections indicate a mountain
top stable layer and strong cross-barrier flow (50-70kts). Some
solutions show better indications of mountain wave amplification
with a stable layer coupled with weakening winds above 600mb. HREF
ensemble shows mean gusts to 70 mph and max gusts 75+ mph. This
is similarly reflected in the HRRR showing potential for gusts
above 85 mph. The plains will also experience gusty winds although
likely below high wind criteria.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 245 PM MST Sat Dec 4 2021
Currently, weak flow aloft and at the surface prevail across the
forecast area with some thin Cirrus cloudiness overhead. Current
temperatures are 10-20 degrees F above normal highs, at least over
the plains and foothills.
Tonight, models show increasing northwesterly flow aloft. Cross
sections indicated a decent mountain wave set up developing by 06Z
tonight. The low level pressure gradient tightens up significantly
as well. High wind speeds seem to be a good bet along the divide
and into the foothills a ways from midnight through about 18Z on
Sunday. Will go with a high wind warning for zones 33, 34, 35 & 36.
It appears the strongest winds should stay above 7,000 feet MSL.
Out on the plains, the downsloping winds should stay below high
wind criteria. However, a pretty strong cold front, with is
expected to upslope flow behind is expected to move across the
plains, into the foothills from 20Z onward during the later
afternoon hours. Some of the models hints at some, potential, low
level cloudiness with this by 00Z, but precipitation is not
expected. There could be a bit of elevated fire danger over the
southern plains and Palmer Ridge of the forecast area by Sunday
afternoon with RH values getting into the teens for a short period
of time. For temperatures on Sunday, readings should be about 5-8
C cooler than today`s highs, except about 12 C colder over the
far northeast corner.
.LONG TERM...(Sunday night through Saturday)
Issued at 243 PM MST Sat Dec 4 2021
Cold advection behind the front will bring temperatures on the
plains down to near or slightly below normal by Sunday night, and
breezy northerly winds should gradually decrease through the
night. Strong winds in the high country will also gradually
decrease as the mountain wave relaxes, but breezy conditions will
persist. Expect lows in the teens to low 20s across the area.
Monday, temperatures will remain slightly below normal across the
plains with highs in the mid 30s to low 40s. Continued breezy
conditions across the higher elevations will moderate the cooldown
there, where temps will stay closer to or slightly above normal
especially in the mountain.
Monday, a weak shortwave will bring an increase in moisture and
cloud cover and some light snow showers in the mountains late
Monday through Tuesday. Accumulations should be light. A few
showers may make it over the Front Range to the adjacent plains
but would only bring flurries. Isolated to scattered, light
orographic snow showers may continue late Tuesday and early
Wednesday as the nose of a northerly jet moves over.
Models disagree on the synoptic situation Wednesday. The GFS has
some quick ridging ahead of another shortwave, while the ECMWF and
Canadian models have a persistent northwesterly flow aloft with
the nose of another jet pushing into Colorado. In general, expect
some brief ridging, subsidence and warming with gradually
increasing winds.
By Thursday, models come back into agreement with a more zonal
flow and around 120 knot jet streak over the area. Breezy westerly
winds are likely in the high country. A trough will be deepening
as it moves over the western states. There is good model consensus
about this next system especially given the time range. It should
be a much colder airmass with better moisture and increasing
potential for widespread snowfall. Snowfall should begin to impact
our mountain zones on Thursday, though the greatest impacts look
to occur Friday into Saturday. Models are showing light snowfall
for the lower elevations as well though details are more uncertain
east of the mountains. Ensembles still favor at least some
measurable snow across the urban corridor and much of the plains,
but with varying degrees of impact.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 440 PM MST Sat Dec 4 2021
VFR conditions expected tonight and Sunday. Light SE and E winds
early this evening will return to drainage (SSW) after 00z.
Main concern for impacts will be gusty winds after 15z Sunday.
Confidence is high for breezy conditions to extend eastward from
the foothills tomorrow. Gusts up to 30kts out of the west to
northwest are possible in the afternoon. Additionally, a front
will bring a surge of gusty northeast winds likely in the 22-00z
timeframe. Winds decrease after 02z. No precipitation expected.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until 11 AM MST Sunday for COZ033>036.
&&
$$
UPDATE...Mensch
SHORT TERM...RJK
LONG TERM....EJD
AVIATION...Mensch
Area Forecast Discussion
National Weather Service Boston/Norton MA
956 PM EST Sat Dec 4 2021
.SYNOPSIS...
A weak frontal system passes from the Great Lakes into the
waters tonight, with high pressure returning for Sunday.
Generally dry and seasonably chilly weather is expected through
the remainder of the weekend. Potential for strong to damaging
wind gusts on Monday along with showers and thunderstorms. Will
be unseasonably mild with highs in the low to mid 60s. Dry and
cooler than seasonable air works into the region late Monday
night and Tuesday. Accumulating snow likely for parts of the
region on Wednesday, but the rain/snow line and the axis of the
heaviest precipitation remains uncertain.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Latest few runs of the HRRR and RAP were doing the best at
acknowledging the clouds and scattered light showers shown on
radar. Not a large risk for accumulating precipitation, but did
tweak precipitation chances this evening. Once the clouds
depart, most of southern New England should remain clear the
rest of tonight. Areas north of Route 2 in MA may flirt with a
few more clouds associated with a lake effect band extending
east from Lake Ontario. Minor tweaks to temperatures and dew
point to reflect observed trends.
745 PM Update...
Have increased precipitation chances across the interior per
latest observations. Have some flurries/light snow showers
moving across the region. Given the temp/dew point spread do not
think much of this reaching ground, but folks could see some
flakes falling over the next few hours. Leaned toward the latest
HRRR guidance.
630 PM Update...
Have adjusted the forecast to lower overnight low temperatures.
We are just a bit clearer than the previous forecast indicated
and with the relatively light winds there should be fairly
strong radiational cooling in place. Lowered temps to the 5th
percentile of guidance to more accurately capture the current
falling temps. Lows bottom out in the 20s across much of the
interior and the low-mid 30s along the coastal plain. Winds have
also decoupled a bit faster than previously indicated, so
adjusted wind speeds/gusts down across the interior. Offshore
winds still looking good. Rest of the forecast remains on track.
215 PM Update...
Generally scattered to overcast mid level clouds prevail across
most of Southern New England this afternoon, with lower cloud
cover around the Berkshires. Fast belt of WNW flow governs
conditions across Southern New England, stuck between two weak
frontal systems: one near the mid-Atlantic coast leading to a
shield of clouds affecting our far southern offshore waters, and
the more prominent if still weak frontal system over western
Quebec.
This latter feature moving in from western Quebec and the Great
Lakes will still contribute to areas of mid-level clouds through
early this evening, although the moisture layer is rather
shallow between 900 and 700 mb. Thus, this frontal passage
should be a dry one with a wind shift from SW to W/WNW with
associated brief period of gusts between 25-30 mph between mid-
evening to midnight, driven by onset of moderate cold advection
coupled rising sea-level pressure tendencies. As pressure rises
become less pronounced overnight, cooling PBL to then be offset
by gradually falling temperatures, with model soundings for the
after- midnight period becoming inverted with a tendency for
gusts to abate for most. The exception is near the
coasts/shorelines and over the waters where somewhat milder air
temps/water temps may maintain WNW gusts to 25 mph into the
overnight.
With at least some sustained WNW winds overnight, kept lows on
the milder side of available guidance, generally in the upper
20s for a large part of the interior, with lower 30s for the
southern/eastern coastlines, and mid to upper 30s for most of Cape
Cod and the Islands.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
215 PM Update:
Sunday:
An approximate 1030 mb high pressure over the western Allegheny
Plateau in PA to progress eastward over Southern New England by
the early to mid afternoon hours. Still rather dry columnar
moisture with PWATs around 0.25 to 0.30 inches, but as high
pressure shifts offshore later in the day and winds become more
onshore, expect PWAT values to improve to around 0.35 to 0.50
inches. Overall a seasonably chilly day but with light south to
southeast winds and generally more sun than today, though high
to mid-level clouds approach late in the day. Highs should be
fairly similar today as more sun offsets the cooler thermal
profiles expected (925 temps -4 to -7C).
Sunday Night:
High pressure moves offshore early Sunday night, with
tightening pressure gradient allowing for stronger S/SE surface
winds. Will see clouds lower and thicken as lead shortwave
disturbance comes up from the mid-Atlantic region, spreading a
warm front northward during the latter half of the night and
especially for the early Monday morning period. Fairly strong
warm and moist advection and increase in cloud cover toward OVC
favored a non-diurnal temperature curve for many locations with
expectation of temperatures rising into the overnight. 925 mb
temps rise to around +5 to +9C by daybreak!
Warm front should bring mainly light showers northward as
temperatures by daybreak for most locations in the 40s to
perhaps near 50F towards the South Coast. However there is some
level of uncertainty as to how quickly will any shallow sub-
freezing air be scoured out across part of the northern hills in
Worcester County, the Route 2 corridor into the Berkshires.
Given the warm profiles aloft with wet-bulb temps running
between 30-32F in this corridor, some light freezing rain or ice
pellets could be possible at onset. While trace amounts are
anticipated, as roads or sidewalks here still may not be
treated/salted, slippery spots possible. Given that some models
show above- freezing surface temps in this area when precip
begins, hence the uncertainty in predominant p-type, have
refrained from winter weather headlines at this point. A
statement or possible winter advisory could be needed for these
far northern and northwestern locations if colder solutions
become more apparent or surface temps are slower to rise then
presently envisioned.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Highlights...
* Unseasonably warm Monday into Monday night with the potential
for strong to damaging wind gusts, showers and thunderstorms.
* Near to slightly cooler than seasonable temperatures for the
rest of the work week.
* Appears that we will see the first widespread accumulating
snowfall Wednesday into Wednesday night, but the specific
amounts and details are uncertain at this time.
Monday into Monday night...
Trough lifts from the Upper Midwest early on Monday into the
eastern Great Lakes/Quebec by late Monday. Will also initially
have a subtle leading shortwave trough lift into the region
early on Monday ahead of the deeper wave. At the surface a warm
front lifts into and through southern New England early on
Monday. A weak low lifts across the Mid Atlantic through the CT
River Valley. There may be a bit of a lull in the precip late in
the AM into the early afternoon before the cold front swings in
for later in the day.
Main concern during this period is the potential for strong to
damaging wind gusts. Will have a roughly 45-65+ kt low S/SW low
level jet crossing the region. This really picks up during the
afternoon and into the evening immediately ahead of the incoming
cold front. Did back off slightly from the previous shift on
how strong gusts get as there is quite an inversion to overcome.
If we can break out in enough sunshine and deepen the mixed
layer then these higher end gusts could be realized, but it will
be dependent on how warm we get. For now started off with the
NBM90th and bumped up speeds around 5 kts, which is roughly 80
percent of the 925 hPa low level jet. Risk of the strongest wind
gusts is highest across SE MA, which includes Cape Cod and the
Islands. Not out of the question that Wind Advisories will be
needed in future updates, but confidence too low at this point
in time.
On top of the wind risk there is the potential for some
convection. There is a lot of deep layer shear in place with
40-70+ kts in place with those values really increasing as that
cold front slides in. The big question is how much instability
can we get, which appears meager and elevated at this point in
time per BUFKIT soundings. As previous shift mentioned, there is
the potential for rotating storms given the helicity in place,
so there is a non-zero risk of a few strong to severe
thunderstorms. Have kept the isolated thunder mention in the
forecast, but really would like to see more convective allowing
guidance other than just the NAM/NAMNest to really dive into
the details. Will also mention there are decent mid level lapse
rates/an EML in place, 6-8 degree Celsius lapse rates, as the
warm front is lifting through earlier in the day. The big
question at this point is how much instability will be in place.
The latest SPC Day 3 general thunder outlook highlights the risk
area well. Will need to hone in more on the convective allowing
guidance in future updates.
Expect it to be anomalously warm with 925 hPa temps of 8-13
degrees Celsius. Went with the 75th percentile of guidance given
am not completely certain how much sunshine we will get in the
break between the warm front lifting through and the cold front
moving in. The result are highs in the mid/upper 50s across the
higher terrain of the interior and the low 60s elsewhere. If we
can clear out a bit more then temps will need to be increased
further in future updates.
Tuesday...
Weak mid level ridge builds into the region bringing drier and
cooler than seasonable temperatures. A surface high builds in
from the eastern Great Lakes/Quebec. Will have blustery
conditions especially earlier in the day before the high can
really relax the pressure gradient. High temps topping out in
the mid 30s to low 40s.
Wednesday into early Thursday...
Next shot for potentially impactful weather for southern New
England. Does appear that there is a risk for widespread
accumulating snowfall, especially across the interior. The
specific amounts/details are uncertain at this point in time
however. The reason for the uncertainty is that there are
differences in the intensity of the trough lifting through the
region. On top of this the exact track of the surface low
associated with the trough is widely spread at this point in
time. Will really need to hone in on the details to determine
the exact totals and where the rain/snow line sets up.
Given the uncertainty at this point in time have really just
stuck with the NBM guidance as there is a lot of spread amongst
guidance. Will point out that the EPS has roughly a 30-60
percent chance of snowfall amounts AOA 3 inches with SLR of
10-1. The GEFS is much more keen on these chances in the roughly
40-80 percent range, but will point out that both pieces of
ensemble guidance have backed off a bit in the probabilities
when comparing run to run. Luckily, the storm is fairly
progressive in nature so would be moving through fairly quickly.
Much too early to dive in the specific details given the
uncertainty, but folks who are traveling will want to keep an
eye on the forecast for future updates.
Mid Thursday through Friday...
Drier on Thursday with any lingering precipitation ending
earlier in the day as low pressure exits. Behind the low, high
pressure builds in briefly bringing dry weather for much of the
day. Will have another shot for isolated to scattered snow
showers late Thursday into Friday as a shortwave swings through.
However, away from the highest elevations across the interior
precip may change over to rain during the day time. Again given
the uncertainty in the Wednesday-Thursday window have mainly
stuck with the NBM.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight...High confidence
VFR with W winds around 5-10 kts. Could have some 10-15 kt
speeds across the Cape/Islands with gusts of 20-25 kts possible
at ACK.
Sunday...High confidence
VFR with W to WNW winds around 5-10 kts becoming light and
variable as high pressure builds in overhead. The high moves
offshore during the afternoon shifting winds to the S/SE.
Sunday Night...High confidence in trends, moderate on timing.
VFR with lowering ceilings; deterioration to MVFR-IFR more
likely after 06Z across the interior. Eastern locations could
see MVFR conditions and spotty IFR toward daybreak. Light rain
for most as temperatures warm overnight, though a period of
light frozen precip (mainly light ZR/IP) may be possible across
northern MA, Route 2 corridor and the Berkshires (e.g. away from
any TAFs).
SE winds increase to 5-10 kt in the interior, and around 10-15
kt eastern/southeast MA and southern RI. Southerly LLJ of 40 kt
associated with warm front may lead to areas of low-level wind
shear and local turbulence from BDL-BED north and west.
KBOS TAF...High confidence in TAF.
KBDL TAF...High confidence in TAF.
Outlook /Monday through Thursday/...
Tuesday: VFR. Breezy.
Tuesday Night: VFR. Chance SN.
Wednesday: MVFR/IFR conditions possible. Breezy. SN likely, RA
likely.
Wednesday Night: MVFR/IFR conditions possible. Breezy. Chance
SN, chance RA.
Thursday: Mainly VFR, with local MVFR possible. Breezy.
Thursday Night: VFR. Breezy. Slight chance SN.
Friday: Mainly VFR, with local MVFR possible. Slight chance RA,
slight chance SN.
&&
.MARINE...
Forecaster Confidence Levels.
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
4 PM Update...
Have hoisted a Gale Watch on Monday into early Tuesday for the
waters. Will have a strong south/southwesterly jet bring a
period of gale force gusts. Not completely out of the question
there could be some brief storm force gusts late in the day, but
will not be as widespread as the gales.
High confidence.
Small craft advisories continue for tonight into Sunday morning
with a period of 25-30 kt westerly gusts as colder air surges
across the waters. Seas briefly build to 3-5 ft on most offshore
waters.
Winds then begin a decreasing trend and become east to
southeast into Sunday afternoon as high pressure moves offshore.
Seas decrease to 3 ft or less all waters.
For Sunday night, gradient strengthens and leads to SE winds
becoming around 15-20 kt, perhaps near small craft levels by
daybreak. Seas will be building toward the 4-6 ft range offshore
and around 2-4 ft on nearshore waters. Light rains approach
southern waters late Sunday night into early Monday morning.
Outlook /Monday through Thursday/...
Tuesday: Low risk for Small Craft Advisory winds with gusts up
to 30 kt. Areas of rough seas.
Tuesday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain.
Wednesday: Winds less than 25 kt. Seas up to 5 ft. Rain likely.
Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Rough seas up to 10 ft. Rain likely.
Thursday: Low risk for Small Craft Advisory winds with gusts up
to 20 kt. Rough seas up to 10 ft. Slight chance of rain, slight
chance of snow.
Thursday Night: Winds less than 25 kt. Areas of rough seas.
Slight chance of rain, slight chance of snow.
Friday: Winds less than 25 kt. Seas up to 5 ft. Slight chance
of rain.
&&
.TIDES/COASTAL FLOODING...
Tide heights are rising to their December monthly highs over
the weekend. The following are the astronomical heights and do
not include surge values from local wind/weather conditions.
Pockets of splash over and minor coastal flooding are possible
on Monday with the best chance along the south coast given
southerly winds. However, significant coastal flooding is not
expected.
Boston Saturday 12.1 feet 1029 AM
Sunday 12.2 feet 1120 AM
Monday 12.0 feet 1214 PM
Nantucket Saturday 4.3 feet 1129 AM
Sunday 4.4 feet 1224 PM
Monday 4.4 feet 120 PM
Providence Saturday 5.9 feet 732 AM
Sunday 5.9 feet 824 AM
Monday 5.8 feet 917 AM
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Gale Watch from Monday morning through Tuesday morning for
ANZ230>237-250-251-254>256.
Small Craft Advisory until 5 AM EST Sunday for ANZ232.
Small Craft Advisory until 3 AM EST Sunday for ANZ233-234-255-
256.
Small Craft Advisory until 4 AM EST Sunday for ANZ230.
Small Craft Advisory until 7 AM EST Sunday for ANZ231-251.
Small Craft Advisory until 2 AM EST Sunday for ANZ237.
Small Craft Advisory until 3 AM EST Sunday for ANZ235.
Small Craft Advisory until 8 AM EST Sunday for ANZ250.
Small Craft Advisory until 9 AM EST Sunday for ANZ254.
&&
$$
SYNOPSIS...BL/Loconto
NEAR TERM...Belk/BL/Loconto
SHORT TERM...Loconto
LONG TERM...BL
AVIATION...Belk/BL/Loconto
MARINE...Belk/BL/Loconto
TIDES/COASTAL FLOODING...Staff
Area Forecast Discussion
National Weather Service Grand Forks ND
850 PM CST Sat Dec 4 2021
.UPDATE...
Issued at 850 PM CST Sat Dec 4 2021
Heavy snow potential on track.
Looking like some sort of lull in impacts by later Sunday
morning.
Confidence continues to increase toward significant blowing snow
impacts within the Red River Valley Sunday afternoon and evening.
The pattern is a classic hybrid blizzard event. Majority of hi-
res guidance indicate a strong secondary cold front will
propagate through the region, bringing strong cold air advection.
Temperatures will rapidly drop, making it easier for freshly
fallen snow to blow around. RAP guidance indicates 925mb winds ~40
knots (and unidirectional through that layer), with due northerly
winds increasing the valley component. Winds will be strong
enough for at least near blizzard conditions, and blizzard
conditions if winds materialize as expected. Using NBM wind
probabilities and the Canadian blowing snow model, there is ~70%
chance for winds to be strong enough to lead to consistent
whiteout conditions (where enough fresh snow exists). Will keep
current headlines as is since they mainly deal with the falling
snow, and plan to transition headlines toward blowing snow
impacts once the falling snow comes to an end or is nearly done.
UPDATE Issued at 700 PM CST Sat Dec 4 2021
Radar imagery indicates band of 700mb warm air advection snowfall
across much of North Dakota, propagating north/northeast. Current
snowfall forecast in good shape, as this initial slow moving area
of snow should lead to 3-5 inches of snow. Then, the upper wave
seen on water vapor imagery provides additional synoptic forcing
across the area where the heaviest snowfall is forecast thus
adding another 3-5 inches of snow by Sunday morning within that
corridor.
Planning on taking a closer look at winds and potential blowing
snow impacts Sunday afternoon/evening with the next update.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 338 PM CST Sat Dec 4 2021
Low pressure continues to deepen from southeastern MT into
northwest SD as a nascent winter storm system intensifies. The
elevated warm frontal band which has formed ahead of this system
continues to slowly lift northward now from northern SD into
south central and far southeastern ND attm, with light snow
showing from the Sisseton Hills along an arc toward Bismarck and
points west.
The deterministic model suite has come into fair agreement on the
overall evolution of this storm system through the remainder of
today through Sunday, with both the GFS and ECMWF operational runs
having slowed just a tad from previous runs. The consensus favors
a slight southerly expansion of the heavier snow, so that the
Fargo-Moorhead area and points eastward have been added into the
Winter Storm Warning area, with expected highest snowfall amounts
still running along and either side of the Hwy 2 corridor. The
Winter Storm Watch area across the far southern Red River Basin is
now in a Winter Weather Advisory. Heavier snow fall is still
expected to develop into eastcentral and southeastern ND through
early evening, and expand across the remainder of the area during
the late evening and over night period tonight.
On Sunday... The surface low center is expected to pass across
central MN through midday, with a very strong wraparound wind
developing in its wake. Though snowfall amounts will drop off
appreciably as the low center passes, there will like be residual
light snow and appreciable blowing and drifting snow developing
across eastern ND by midday and then across northwest through west
central during the afternoon. The more exposed areas of eastern
ND, the Red River corridor, and western MN will likely experience
near blizzard conditions Sunday afternoon into the evening.
Forested areas in northcentral MN will see pockets of significant
blowing and drifting snow in more exposed areas.
Temperatures tonight through Sunday afternoon will range though
the teens north to upper 20s south, then dropping off throughout
the afternoon on Sunday. Overnight lows on Sunday night will
plummet down to and below zero across most of eastern ND and
northwest MN.. with winds chills ranging from minus 15F to minus
25F by Monday morning.
.LONG TERM...(Monday through Saturday)
Issued at 524 PM CST Sat Dec 4 2021
Not much risk for impactful weather coming up for the week ahead, in
the wake of the prior weekend event.
A much colder airmass moves in as the winds gradually diminish
from near 20 mph around sunrise to a more zephyr-like 5 to 10 mph
by sunset on Monday. High temps will only be in the single
integers above zero before dipping to between 5 and 15 below at
night as a result wind chills will be in the 15 to 30 below range.
The new snow pack will aid in the redux, the degree of which will
naturally be determined by cloud coverage.
Ensembles and clustered products don`t really show much of
consequence for Tue through Fri; a few short waves moving through NW
flow could trigger some light snow over the southern valley later
Tue, with another chance coming on Thu. Temps will rebound on
Wed/Thu, maybe getting above freezing over the far south on Thu.
That time frame should offer more robust winds, out of the SW
approaching 20 mph.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 524 PM CST Sat Dec 4 2021
Snow will lift northward this evening across the region as it does
VSBYs and CIGs will erode. Expecting mostly MVFR and IFR
conditions to develop within the heaviest snowband overnight and
some gusty southeasterly winds. Tomorrow snow wanes but north
winds will increase with BLSN concerns and gusts of 30 to 40 kts.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...Winter Weather Advisory until midnight CST Sunday night for
NDZ038-049-052-053.
Winter Storm Warning until midnight CST Sunday night for
NDZ006>008-014>016-024-026>030-039-054.
MN...Winter Weather Advisory until midnight CST Sunday night for
MNZ029>031-040.
Winter Storm Warning until midnight CST Sunday night for
MNZ001>004-007-022-027-028.
Winter Storm Warning until midnight CST Sunday night for MNZ005-
006-008-009-013>017-023-024-032.
$$
UPDATE...TG
SHORT TERM...Gust
LONG TERM...JK
AVIATION...WJB/JK
Area Forecast Discussion
National Weather Service Green Bay WI
911 PM CST Sat Dec 4 2021
New Information added to update section
.UPDATE...
Issued at 910 PM CST Sat Dec 4 2021
Decided to issue a Winter Weather Advisory for Door, Southern
Oconto, Menominee, Shawano and Marathon counties for Sunday.
Forecast soundings suggest that 2 to 5 inches of snow should fall
in most of that area along with winds gusting to 35 mph at times.
&&
.SHORT TERM...Tonight and Sunday
Issued at 335 PM CST Sat Dec 4 2021
The main concern for today will be the snow arriving late tonight
and continuing into Monday morning. There was a slight shift to
the south with the heavier snow. A northwest to southeast band
of snow is expected to break out ahead of the main system. Still
a good deal of uncertainty in where the band will set up as some
of the models are farther south than yesterday. However, the
latest HRRR model has trended slightly to the north on the latest
run.
Decided to go with a winter storm warning for Vilas, Oneida,
Forest and Florence counties where some locations could see 6
inches within 12 hours on Sunday if the band sets up over the
same area for a period of time. Have winter weather advisories
for the tier of counties to the south. To the south, there will
be a wintry mix as boundary layer temperatures should climb into
the middle to upper 30s.
There will be a lull in the heavier precipitation at some point
Sunday evening with the heavier precipitation moving back into the
north after midnight. Some of the worst conditions across the
north will be late Sunday night into Monday as the snow ratios
lower, thus providing a powdery snow will blow around with wind
gusts of 30 to 40 mph creating considerable blowing and drifting
of the snow. Snowfall accumulations of 7 to 11 inches are expected
across Vilas County while totals less than an inch are are
expected south of a Wisconsin Rapids to Green Bay to Sturgeon Bay
line.
Gusty northwest winds late Sunday night could result in some power
outages across the north as well.
.LONG TERM...Sunday Night Through Saturday
Issued at 335 PM CST Sat Dec 4 2021
The mix of drizzle, freezing drizzle, and snow on Sunday will
transition to all snow Sunday night as the storm system moves
northeast into Canada and cold air pushes in on the back side of
the system. Lake-effect snow across the far northern counties of
WI will be the primary source of precipitation Sunday night thru
Monday afternoon. However, winds will gust to 30-40 mph out of
the west-northwest Monday morning, causing blowing snow and poor
visibility across many areas from Highway 29 north.
Low temperatures will tank Monday night as Canadian air moves in
and winds slacken. Lows in the Fox Valley will drop to near zero
while central and northern WI should see temperatures as low as
10-15 degrees below zero.
The progressive pattern aloft will remain in place, and there will
be chance for snow on Tuesday as a mid-level shortwave rotates
through the region. With cold air and weak northerly winds still
in place, high temperatures on Tuesday will only struggle into the
teens. After that, winds should switch around to the south again
as the high pressure ridge shifts east of us. Temperatures should
moderate on Wednesday with the wind shift and as another shortwave
possibly approaches on Thursday.
&&
.AVIATION...for 00Z TAF Issuance
Issued at 549 PM CST Sat Dec 4 2021
Middle clouds will increase this evening as low pressure approaches
from the Northern Plains. Light snow will arrive from west to
east after midnight, with MVFR conditions conditions by daybreak
west of an IMT to CWA line.
Snow and IFR conditions are expected north of a CWA to SUE line
Sunday, with snow and rain showers to the south and mostly MVFR
conditions.
Snow will continue north of a AUW to IMT line Sunday night, with
areas of drizzle or friezing drizzle elsewhere. A cold front will
move across the area late Sunday night and bring an end to the
precipitation, with the exception of lake effect snow showers
north of a RHI to IMT line. Winds will become westerly and gust to
35 knots or more through midday Monday.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning from 3 AM Sunday to noon CST Monday for
WIZ005-010>012.
Winter Weather Advisory from 6 AM to 9 PM CST Sunday for WIZ022-
074.
Winter Weather Advisory from 3 AM Sunday to noon CST Monday for
WIZ013-018-019-021-073.
Winter Weather Advisory from 3 AM to 6 PM CST Sunday for WIZ020-
030-031.
&&
$$
UPDATE.........RDM
SHORT TERM.....Eckberg
LONG TERM......ML
AVIATION.......RDM
Area Forecast Discussion
National Weather Service Lincoln IL
739 PM CST Sat Dec 4 2021
.SYNOPSIS...
Issued at 255 PM CST Sat Dec 4 2021
Cool high pressure will slide east-southeast through the area
tonight. Rain is in the forecast for Sunday with mainly scattered
showers expected, but there could be some thunderstorms south of
I-70 Sunday night. Central Illinois will see an active pattern
through next weekend, with a chance of snow on Tuesday night
followed by chances for mainly rain for the latter part of the
week and into the weekend.
&&
.UPDATE...
Issued at 739 PM CST Sat Dec 4 2021
Mid and high level clouds have gradually been spreading southeast
early this evening, with the thicker clouds still north of I-74.
Most places are still in the mid 30s to lower 40s at 7 pm.
Exception was the Decatur airport at 29 degrees, but after an
investigation of nearby mesonet stations, this appears to be an
anomaly as other stations around Decatur are in the mid 30s. The
clouds will continue to expand across the forecast area overnight,
though areas south of I-70 should remain fairly clear until
closer to daybreak. Not expecting a huge dropoff in
temperatures, as winds are expected to pick up some toward
midnight. Latest HRRR suggests some light rain making it as far as
Springfield by 6 am, but soundings show a decent amount of dry air
lingering below 850 mb at that point, so will leave the forecast
dry there at this time.
&&
.SHORT TERM...(This evening through Sunday night)
ISSUED AT 255 PM CST Sat Dec 4 2021
Currently, the region is under the influence of a ridge of high
pressure at the surface, with the high centered over southern MN
and IA. The high will slide ESE across northern IL to PA tonight
in order to make way for a strong low pressure system developing
in the Northern Plains. This low will move east across the Great
Lakes region Sunday night into Monday. With the warm, moist air
pushing northward ahead of this system, expect enough instability
and lift to produce some showers on Sunday and Sunday night across
much of Illinois. The latest suite of near-term convective
allowing models indicate there should be MUCAPEs of perhaps up to
500 J/kg generally south of I-70 Sunday night. So, have included a
chance of thunderstorms in this area. Not expecting severe
weather this far north, but it will be possible south of
Lawrenceville. A cold front will sweep through the area Sunday
night as well, ushering in considerably colder air for Monday.
&&
.LONG TERM...(Monday through Saturday)
ISSUED AT 255 PM CST Sat Dec 4 2021
By Monday, the cold front will have pushed through the area and an
upper trough will exist aloft over the region. Skies will be
clearing and temps will struggle to rise during the day, leaving
highs only in the 30s in most areas. Cold high pressure will
settle in over the region on Monday night, with lows in the teens
to low 20s expected.
With west-northwest flow aloft across the region on Tuesday, an
upper level wave will begin to deepen across the central U.S...and
push ESE from the Northern Plains. Isentropic lift, and eventually
a band of frontogenesis, will set the stage for some snow
development Tuesday night. The latest forecast supports light snow
accumulations in the region.
Expect the region to stay active with yet another system possible
late in the week. However, temperatures support a mostly rain
forecast at this time as we transition to a warmer southwest flow
aloft. Models have trended wetter with this system, but
uncertainty remains high. Another weather system is expected for
the weekend and currently looks like one of the stronger systems.
There`s plenty of uncertainty with the details of this system
also.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 535 PM CST Sat Dec 4 2021
The pre-12Z period will be fairly quiet, with winds gradually
shifting southeast and increasing to about 8-10 knots. After that,
a steady lowering of ceilings is expected as rain showers move
in from the southwest, with MVFR conditions likely at all sites
between 15-18Z. Ceilings linger below 2,000 feet through the
afternoon. Southeast winds will continue to pick up and gust
around 20 knots most of the day.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Geelhart
SYNOPSIS...Knutsvig
SHORT TERM...Knutsvig
LONG TERM...Knutsvig
AVIATION...Geelhart
Area Forecast Discussion
National Weather Service Melbourne FL
924 PM EST Sat Dec 4 2021
.DISCUSSION...
Skies will be mostly clear to partly cloudy into tonight with
ridge axis of high pressure over the west Atlantic remaining
extended across the area. This will generate a light southerly
flow in the low levels, which will again be conducive for fog
development overnight. Greatest potential and coverage of any
dense fog, producing visibilities of a quarter mile or less, will
continue to be toward and N/NW of the I-4 corridor after midnight
through early morning Sunday. However, patchy dense fog will be
possible across much of the area as favorable radiational cooling
conditions drop temperatures into the 50s over much of the region.
Dense Fog Advisories may again be needed over portions of the
area should fog become widespread enough late tonight.
HRRR is showing some isolated showers approaching the Treasure
Coast late tonight, but not moving onshore until after daybreak.
Will therefore keep rain chances out of the forecast for land
areas tonight.
&&
.AVIATION...Fog development possible again tonight, with light
winds and mostly clear to partly cloudy skies prevailing
overnight. Greatest chance for areas of dense fog still looks to
be toward and N/NW of I-4, with visibilities less than a mile.
Model guidance has not been in the best agreement with coverage,
but should begin to see fog form after 06Z and increase in
coverage through daybreak and then gradually lift and dissipate
into late morning Sunday. VFR conditions then expected to largely
prevail during the day, with only brief reductions in cig/vis in
isolated onshore moving showers along the Treasure Coast.
&&
.MARINE...Ridge of high pressure over the west Atlantic will
remain extended across the waters into tonight, with S/SE winds
around 5-10 knots. Seas will linger around 1-2 feet.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 52 77 61 80 / 0 10 10 0
MCO 54 81 63 83 / 0 0 0 0
MLB 57 78 63 81 / 0 10 10 10
VRB 59 81 65 85 / 10 20 10 10
LEE 53 81 62 83 / 0 0 0 0
SFB 54 80 62 83 / 0 0 10 0
ORL 55 80 63 82 / 0 0 10 0
FPR 58 79 63 83 / 10 20 10 10
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&
$$
Weitlich/Cristaldi
Area Forecast Discussion
National Weather Service Springfield MO
525 PM CST Sat Dec 4 2021
...00Z AVIATION UPDATE...
Key Messages:
1. Drizzle or light rain showers possible tonight-Sunday.
2. Strong to severe storms possible Sunday Night south of I-44.
3. Cooler and drier weather early next week.
4. Additional precip chances next weekend.
.SHORT TERM...(This evening through Sunday)
Issued at 130 PM CST Sat Dec 4 2021
A stationary front across Oklahoma and Arkansas was in the
process of slowly lifting north this afternoon. Dewpoints to the
north of the front, across our area, were in the 30s, with areas
south of the front experiencing dewpoints in the 60s. Low to mid
level clouds will continue to lift north into the area tonight.
As we head later into the night, a low level jet will increase
across the area. A weak 700mb wave approaches and should provide
additional lift for some isolated to scattered precip to form.
Forecast soundings show plentiful low level moisture, however an
absence of cloud ice will likely lead to areas of drizzle or very
light showers. Temperatures will likely level off or slowly rise
across the western half of the area overnight.
While some patchy drizzle or showers could last through the
morning, HREF cloud cover data and forecast soundings suggest
that the area may see some clearing during the afternoon Sunday
ahead of the next cold front. Stayed with NBM highs for now
(middle 60s), however if clouds clear sooner, then highs could go
up a few more degrees. Gusty winds up to 30mph are possible during
the day.
.LONG TERM...(Sunday Night through Saturday)
Issued at 130 PM CST Sat Dec 4 2021
Sunday Night Storms: Models are in excellent agreement that a cold
front will drop southeast into Missouri Sunday Evening. The area
will be located in a favorable position to the subtropical jet to
the south of the area, and a digging polar jet to the north. This
is a classic clash of airmasses. Forecast soundings show that the
area will likely be capped until late evening. The cold front
looks to enter the far NW counties by 7-8pm. HREF updraft
probabilities increase markedly once the front gets to Interstate
44 by 9-10pm. This is where storm initiation appears possible.
Storms look to then form quickly as the front moves through areas
south of Interstate 44. Updraft helicity values from the HREF are
maximized just south of the Missouri/Arkansas state line.
Forecast soundings from Branson to West Plains off the RAP and
NAM both have about 500-750j/kg of ML cape, and about 40kts of
0-6km shear. Hodographs generally show a unidirectional flow, with
west to southwest winds. Mid level lapse rates look to be in the
7-7.5 C/KM range. Therefore the ingredients are there for a few
strong to severe storms with large hail and damaging winds south
of Interstate 44. The tornado potential looks very low at this
time, especially with the forecast hodographs. The band of storms
will likely be southeast of the area by 3-5am early Monday
morning.
Early Next Week: The airmass behind this front will be much cooler
and drier, with surface dewpoints in the teens by Monday morning.
Gusty northwest winds and a dry airmass will likely lead to a
elevated fire weather threat Monday afternoon. NBM spread of temps
are small, with highs in the lower 40s likely. Model ensemble
clusters are in decent agreement that a zonal upper level pattern
will develop during the week, with a few weak waves moving through
at times. One such wave, as shown more pronounced by the GFS
ensembles, moves through the area Tuesday night into Wednesday
morning. There may be enough lift for some light precip during
this time, however other model clusters are much lighter, or even
dry. Given the colder environment, if any precip were to fall, it
would likely be flurries/light snow. Current NBM probabilities for
light snow are less than 50 percent, with slightly higher
probabilities just northeast of the area. Warm ground temps would
negate any impacts.
The pattern then looks to become zonal to slightly southwesterly
for the rest of the week, with NBM temperatures slowly climbing a
few degrees each day. A 10 degree spread exists for Friday,
however the range is all above average, either in the upper 50s to
upper 60s, therefore the warmest day of the week will likely be
Friday.
Next Weekend Storm System? We will be monitoring the ensemble
data as we look to next weekend. Ensembles are in decent agreement
that a large upper level trough will develop out west, however
timing differences exist on when it will eject out into the
plains. This has large implications on temps and precip chances
and for now have not strayed from the NBM which has precip chances
in the 30 to 50 percent range for next weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 511 PM CST Sat Dec 4 2021
Current VFR conditions will begin to change to MVFR status likely
after 03Z as ceilings begin to lower. Winds will shift and take a
more southwesterly direction, and some gusts over 20 kts will be
likely for KSGF overnight into tomorrow. Low level wind shear can
be expected between 10Z-16Z Sunday, mainly for KSGF and KBBG.
Tomorrow afternoon, winds will take a southerly direction, and
gusts over 20 kts will be likely again for all sites. Cannot rule
out light rain showers or drizzle late tonight into Sunday
morning.
&&
.SGF WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&
$$
SHORT TERM...Burchfield
LONG TERM...Burchfield
AVIATION...Schwartz