Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/03/21
Area Forecast Discussion
National Weather Service Bismarck ND
1004 PM CST Thu Dec 2 2021
.UPDATE...
Issued at 1002 PM CST Thu Dec 2 2021
Snow has ended across the Turtle Mountains region. An area of very
low clouds has now settled in across parts of Burke, Mountrail,
Renville, Bottineau, and Rolette Counties. Tioga, which is near
the edge of the low cloud deck, recently reported 2 mile
visibility. Think that patchy fog may also be possible along
higher terrain areas underneath the low clouds. The clouds and
patchy fog will likely persist until the cold front moves through
later tonight.
Gusty winds have been observed upstream along the cold front. The
90th percentile of NBM membership along with the HRRR were
utilized to increase forecast winds and gusts as the front moves
across western and central North Dakota overnight. Peak gusts
should be limited to around 35 mph.
Periods of light rain continue along the South Dakota border, and
will likely diminish or drift out of the state after midnight.
UPDATE Issued at 636 PM CST Thu Dec 2 2021
A band of moderate snow has developed across Bottineau, Rolette,
northern Pierce, and far northern McHenry Counties in response to
mid level frontogenesis and isentropic ascent. Area webcams are
showing snow-covered roads across Bottineau County, where the
snow will soon be winding down. Areas along and north of Highway 2
and east of a line from near Bottineau to Towner can expect
deteriorating conditions through 730 PM CST.
A separate area of frontogenesis further to the south continues to
promote areas of light rain along and south of Interstate 94. This
rain is likely not as intense as some radar returns are making it
out to be due to a low level layer of dry air, but at least
sprinkles are reaching the ground. The chance for light rain will
drift off to the south and east through the evening.
A cold front will move from northwest to southeast across the
state later tonight. The forcing from the frontal passage through
a more saturated low level layer in north central North Dakota
may provide enough lift to generate some light freezing drizzle
and/or fog, but this is not a high probability outcome at this
time. There is also a potential for gusty winds with the frontal
passage, perhaps stronger than we are currently advertising. This
potential will be examined closer for the next update.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 251 PM CST Thu Dec 2 2021
We continue to watch two areas of precipitation this afternoon
across western and central North Dakota.
One area of light rain was located over the south, parked under
enhanced 700 mb frontogenesis per the SPC mesoanalysis page. This
light rain should continue through the afternoon, slowly
diminishing from west to east as frontogenesis starts to wash out
by this evening.
Another area of light snow will continue to develop across the
north central and northeast this afternoon through early evening.
As a weak wave continues to ride down the broad ridge to our west,
it will interact with a backdoor cold front as the drifts from
the northeast into the north central. When all is said and done,
we could end up seeing anywhere from a trace of snowfall to a half
inch or so, mainly in and around the Turtle Mountains.
It will be a bit cooler tonight with lows in the 20s and diminishing
clouds. Surface high pressure moves in on Friday, leading to
cooler high temperatures (but still normal to slightly above
normal for this time of year) in the lower 30s to lower 40s.
Clouds will be on the increase again Friday night in advance of
the next shortwave trough with lows in the mid teens to lower 20s.
.LONG TERM...(Saturday through Thursday)
Issued at 251 PM CST Thu Dec 2 2021
Accumulating snowfall from Saturday morning through Sunday morning
will be the big story for the long term forecast period.
The upper ridge to our west will continue to flatten on Saturday
as the aforementioned shortwave trough approaches. As this wave
passes over the Northern Rockies, we will see a low develop under
the influence of the right entrance region of one upper level jet
streak and the left exit region of another.
Precipitation will enter the west Saturday morning and spread
north and east through the day and night as the low approaches
the Montana/North Dakota border towards Saturday evening. Models
are in good agreement on the dynamics: strong frontogenesis to
the north and northwest of the low overlapping strong upper level
Q-vector divergence and steep midlevel lapse rates. All of this
points to a classic heavy banded snowfall setup somewhere across
northern or central North Dakota. Along and south of this
frontogenetical band, some negative EPV is also likely so a
convective element may present itself as well.
The big question and main source of uncertainty remains the
track/location of the low/band as the band could be relatively
narrow. In previous days, models had been settling on areas along
and north of Highway 2 but there has been a trend in the ensembles
to nudge the band a bit more south. While the northern third of
the state is still most favored for the heaviest snowfall, a
further south solution cannot be ruled out. The best bet for
accumulations will be north of Interstate 94.
Expect moderate to heavy snowfall to develop wherever the band
does setup. Several inches of snow are possible under this band
and areas under the heaviest part are likely to see 6 or more
inches before the low moves out. We did discuss the potential for
a Winter Storm Watch but chose to hold off given the exact
placement of the band will likely change multiple times between
now and the event. For now, will communicate the potential in the
Hazardous Weather Outlook, a Special Weather Statement, and social
media messaging. But, headlines will likely be needed at some
point as confidence grows.
Behind the low, winds will increase out of the northwest and
become gusty Saturday night and Sunday. Some lingering light wrap
around snow will be possible Sunday. Any fresh snow that has
fallen or is still falling will blow around, causing visibility
reductions and drifting snow. A Wind Advisory will also likely be
needed at some point Sunday for at least the south where the
models are showing the strongest pressure rises and steepest lapse
rates.
Another weak wave will move through Sunday night, possibly
bringing with it some more light snow, before high pressure moves
in on Monday. Monday morning lows will be chilly with double
digits below zero possible across the north. Wind chills could dip
as low as 25 below here. Afternoon highs will struggle to rise
much above zero northeast, and up into the mid 20s southwest.
Another frigid night is on tap Monday night.
We will likely see our typical baroclinic zone in place across
the region with northwest mean flow aloft through the rest of the
period (cold northeast and milder southwest), and the NBM depicts
this well with large high and low temperature spreads of its
members through Thursday. The next best chance for some more
light snow will be Monday night into Tuesday morning.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 1002 PM CST Thu Dec 2 2021
A cold front moving from northwest to southeast across North
Dakota later tonight could bring a period of MVFR ceilings and
gusty northwest winds. The probability of MVFR ceilings is highest
at KMOT. Clearing skies and northwest winds around 10-15 kts are
expected for Friday.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Hollan
SHORT TERM...ZH
LONG TERM...ZH
AVIATION...Hollan
Area Forecast Discussion
National Weather Service Caribou ME
922 PM EST Thu Dec 2 2021
.SYNOPSIS...
The low will track north of the area tonight into Friday
bringing a strong cold front across the region. Canadian high
pressure will build later Saturday into Sunday. Another low will
approach and track north of the state on Monday. A cold front
will push through Monday night with high pressure returning on
Tuesday.
&&
.NEAR TERM /THROUGH FRIDAY/...
9:20 PM Update...Forecast remains on track with bands of rain
moving east across the area. A closer look at mesoscale forecast
models is revealing a small but shortwave trough coming through
in the early morning as much colder air begins to surge in. This
could bring a burst of snow around sunrise Friday morning. Added
a brief period of numerous snow showers to the early morning.
Tonight...Warm/occluded front will lift n of the region tonight
w/the warmer air streaming all the way to the northern border
w/snow or mixed precip going to rain. Not expecting heavy rain
as precip has been generally light under-performing the expected
amounts. Radar had the first batch of precip lifting across
northern and eastern areas this afternoon w/another set of
precip apchg western areas lifting ne w/the warm front. That
batch of precip in the form of rain will lift up across thew
region. Adjustments were made to rainfall amounts to go a bit
lower than previously expected for early evening. However, there
is a llvl jet moving into NYS, which could enhance rainfall
amounts w/that second batch at it lifts ne into the late evening.
This in turn could enhance rainfall as it moves through the
region into late evening. Given the latest setup w/the cold
front still well back across Ontario and NYS, warmer air looks
like it will hang in longer into daybreak as shown by 12Z GEM
The GEM has been consistent over the last 3 runs w/hanging the
colder air back, which is now backed up by the HRRR and RAP. The
bulk of the precip will lift into Canada by the wee hrs of
Friday morning. The low temp tonight will be around 7 PM as
temps will rise overnight. There will be some melting of the
snow, which will lead to some fog formation into the late
evening.
For Friday, the vigorous cold front is set to move across the
region during the morning hrs w/nw areas seeing temps falling
off quickly by daybreak w/some snow showers and streamer action
setting up. High temps will be hit early, most likely before 12
PM for most of the region, w/the coast being the last to see
the sharp drop off in temps. That cold air will sweep across the
region during the rest of the day w/temps falling back. Upper
trof, NW flow and steep llvl lapse rates will allow for some
shower and streamer activity to continue right into mid
afternoon before the column starts to dry out. The GEM depicts
the streamer action quite well as does the 12Z NAMNEST. Another
item to point out is those steep lapse rates combined w/the
dropping temps, and strong pres gradient will lead to some wind
gusts closing in around 40 mph, especially across the higher
terrain. This will lead to some lower vsbys, blowing snow at
times and sporadic power outages.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
Fri night expect strong gusty winds to slowly dissipate during
the night but with the pressure gradient still tight expect
gusts 20-25mph through much of the night. Despite the winds the
air mass is very cold with 925-850mb temps -13C to -16C
advecting into the area on northwest flow aloft. NOAA Hysplit
backward trajectories show this air mass originating from the
Arctic region of far northern Canada. So despite the winds
expect low temperatures Sat AM to be around 0F in the North
Woods, Single Digits to low teens across the northern 1/2 of the
FA with Teens to near 20F from Bangor region to the coast. Wind
chills Fri night into Sat AM will be running -15F to -5F across
the northern zones, +5F to +10F in southern zones.
Saturday will feature a weak disturbance approaching from the
west with a weak cold front. Sunny start to the day with
increasing clouds with a weak front but a coastal system well
offshore may squeeze out a few snow showers back across the
Downeast coast. The weak front will spread snow showers into the
North Woods during the evening then spread south and east
through the night. Not expecting much in the way of
accumulations with perhaps a Dusting in spots. Another cold
night with a reinforced shot of cold air originating from the
Arctic region of Canada. Lows 0-10F north with 10-15F from
Bangor to interior Downeast with around 20F right at the shore.
Sunday will feature high pressure setting up over southern New
England which is in very good agreement with latest GFS/ECMWF
and Canadian ops runs. Highs running 5-10 degrees below average
area wide partly sunny skies resulting in highs mid to upper 30s
in southern zones and low to mid 20s across the north.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Sun night the high pressure will slowly drift east of the Gulf
of Maine waters. A warm front will lift northward through the
night across the state. As precip develop after midnight expect
cold air damming intially so light snow will develop from the
Bangor region northward into the Crown. It is likely the warm
air shoots inland across coastal areas by the time precip
starts. The warm front will push well north of the St. John
Valley by afternoon with warm air surging north and all areas
turn to rain. Models are in very good agreement with the low
pressure tracking north well into Quebec. A large slug of high
PWATs surge north so expecting gusty southerly flow and moderate
to perhaps brief heavy rain. Given the cold ground and highs in
the low 50s across the south and mid to upper 40s north expect
patchy fog to develop. Precip will slowly taper but colder air
will push east as a strong cold front clears the state. Rainfall
totals generally 0.5-0.75" possible and perhaps some snow
accumulations on the backside. High pressure settles over the
Mid Atlantic and the pressure gradient tightens up so expect
breezy westerly winds on Tuesday. Partly to mostly sunny skies
but expecting upslope clouds across the North Woods. Highs will
be 20-25F cooler than Monday back into the 20s to low 30s. High
pressure looks to shift east Tue night and another system
develops over the Mid Atlantic states. There is significant
differences in the operational runs and ensemble members where
this storm tracks. For now opted to take a blend resulting in a
chance to likely snow with the best shot of precip in the
southern 2/3rd. This could produce a decent accumulating snow if
the track remains over the Gulf of Maine but the upper level phasing
will be the key. As the system departs east expect a chance of
snow showers but temperatures remain below average.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
NEAR TERM: IFR/LIFR into late evening w/rain becoming MVFR LATER
tonight w/rain going to a period snow by daybreak for KFVE. S
winds 10-20 dropping back to around 10 kt later in the evening,
and becoming SW. LLWS tonight as winds around 1500 ft could
reach 40 kt.
For Friday, W wind 10-20 kt in the morning becoming NW 15-25 kt
w/gusts to 35 kt, especially across the higher terrain such as
KFVE and KCAR. MVFR cigs at times w/vsbys dropping down to IFR
times in snow showers and gusty winds.
SHORT TERM: Fri night...VFR. W winds 15-25kts.
Sat...VFR. W winds 5-15kts.
Sun...VFR/MVFR. SW winds 5-10kts.
Mon...MVFR/IFR cigs/vsby w/ LIFR possible in the afternoon.
Snow changing to Rain at all sites. S winds 15-25kts. LLWS
possible.
Tue...MVFR cigs early becoming VFR. W winds 15-25kts.
&&
.MARINE...
NEAR TERM: Gales in place including the intra-coastal zones
through Fri evening. S wind 20-25 tonight becoming SW late and
increasing to 25-30 kt w/higher gusts. Seas climbing to 8-9 ft.
For Fri, SW winds become WNW and increase to 30-35 kt w/gusts
hitting 40+ kt due to the strong pres gradient. Seas could hit
near 10 ft before dropping back to 7-8 ft late in the day.
SHORT TERM: Gales weaken to SCA level gusts through Sat
daybreak. Wind gusts fall below SCA levels through the morning
and remain below SCA through early Mon AM. By Mon late morning
southerly Gales likely return with another strong storm system.
Seas subside to between 2 and 4 feet through Sat. Seas become
1-3ft for Sun with seas building to 6-10ft by Mon afternoon.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...Gale Warning until 10 PM EST Friday for ANZ050>052.
&&
$$
Near Term...Hewitt/MCB
Short Term...Sinko
Long Term...Sinko
Aviation...Hewitt/Sinko
Marine...Hewitt/Sinko
Area Forecast Discussion
National Weather Service Cleveland OH
906 PM EST Thu Dec 2 2021
.SYNOPSIS...
A cold front will cross the area this evening ushering in a much
colder airmass. High pressure will briefly build across the
Ohio Valley and lower Great Lakes by Saturday before a strong
low pressure system and associated cold front progresses into
the region Sunday into Monday bringing gusty winds.
&&
.NEAR TERM /THROUGH FRIDAY NIGHT/...
900 pm update...
We made some minor adjustments to the hourly POP forecast from
this evening through Friday morning. We increased POPs slightly
for the primary Snowbelt areas of far NE OH and NW PA overnight
for some lake effect snow showers overnight into early in the
morning. Some light accumulations up to localized inch of
snowfall could be possible. Otherwise, the rest of the near term
forecast is in good shape at this time.
Previous discussion...
A secondary cold front that will be responsible for bringing the
true airmass change is currently dropping southward onto Lake
Erie. Current surface analysis depicts this boundary well
showing strong 3 hour pressure rises behind the front and winds
veering from WSW to WNW. Expect the boundary to progress across
the region quickly this evening with temps falling through the
40`s. Moisture along the front is limited with NAM and RAP
forecast soundings showing significant mid-level dry air, but
kept slight chance PoPs for a few light showers in NW PA this
evening where moisture is a bit better. The flow will become
increasingly NW in the cold air advection overnight with 850 mb
temps falling to -6 to -9 C through Friday morning with the
coldest being over the eastern basin of Lake Erie. This will set
up a minimal lake response with about a 14 C lake to 850 mb
deltaT and 19 C lake to 700 mb delta T. However, the
aforementioned shallow moisture and weak instability will keep
lake-effect precip light. HREF guidance suggests a Lake Huron
fetch into eastern Erie County PA for a few hours in the 05 to
12Z timeframe, so kept chance PoPs for light rain and snow in
that area through the night. On Friday, a fast moving mid-level
vort max and associated 150 knot 300 mb jet streak will slide
across the lower Great Lakes and Upper Ohio Valley. The
resultant upper divergence and PVA and isentropic upglide will
squeeze out a band of light precipitation starting over NW Ohio
during the mid morning hours expanding through NE Ohio and NW PA
during the afternoon and evening. Moisture is once again
limited, so QPF will only be a few hundredths of an inch. The
main impact with this feature will be to create overcast skies
and scattered light rain/snow or drizzle leading to a cold, damp
day. Behind this feature, renewed NW flow returns Friday night.
Soundings show a lot of boundary layer shear, so think any lake
response will be very limited, but HREF guidance suggests a
little lake enhancement over NW PA. Kept slight chances of light
rain/snow, but we could very well end up dry. Went a degree or
two colder then NBM/CONSSHORT for temps Friday given the clouds
and precipitation.
&&
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
A few lingering lake effect snow showers may continue for NW PA into
the beginning of the near term, but should diminish through Saturday
as high pressure and a much drier airmass move southeast across the
area. Little to no accumulation with these remaining showers is
expected for Saturday. The high pressure and dry conditions will
persist through Saturday night before moving off the New England
Coast ahead of an approaching low pressure system. High temperatures
on Saturday will be in the low to mid 40s with overnight lows in the
mid to upper 20s.
On Sunday, a low pressure centered over the northern Plains will
continue to strengthen with strong upper level support as it
approaches the Great Lakes region. South-southwest winds will
increase WAA and moisture over the area as a warm front moves north.
Winds are expected to steadily increase across the area beginning
Sunday afternoon/evening into the long term period as a result of
the pressure gradient becoming stronger with the deepening low. The
track of the surface low continues to look very favorable to
sustained winds near 20 mph, with elevated wind gusts of 40 mph or
greater Sunday night into Monday. This will need to continue to be
monitored for the potential of a wind advisory. During the day on
Sunday, most areas should remain dry, although areas of NW OH may
start to see rain showers late afternoon. These rain showers will
develop along and ahead of a strong cold front, moving west to east
Sunday night. Current thinking is that much of the precipitation
should remain primarily as rain as 850 mb temperatures remain above
freezing. Only areas that may see some snow mix in would be the
higher elevations in NW PA and NE OH. High temperatures will be
above average, reaching the low to mid 50s. Overnight lows will be
in the low to mid 30s.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
A few lingering showers may persist across the eastern counties as
the cold front departs to the east near day break on Monday. The low
is forecast to be centered north of the Great Lakes, allowing for
primarily west winds to persist into Tuesday. Strong winds remain a
concern through Monday evening as much colder air surges southeast
across the area. 850-mb temperatures are expected to decrease to -8
to -12C. This pushing across Lake Erie will likely allow for lake
effect snow to develop and impact the snowbelt, which will persist
until the winds shift to become southwesterly on Tuesday. The
biggest challenge with this lake effect set-up is how far inland the
wind will push snow showers. In conjunction with much colder air
aloft, high temperatures at the surface on Monday will be in the
40s, dropping into the 30s on Tuesday.
An active pattern persists over the area, with numerous shortwave
troughs modeled to move over the Great Lakes region through
Thursday. A low pressure system moving north from the Gulf Coast
could bring widespread synoptic snow Tuesday night into Wednesday as
the area will lie on the northern side of the low, but any change in
track of the low will adjust precipitation chances and type. This
will need to continue to be monitored. Temperatures Wednesday and
Thursday will return to near normal.
&&
.AVIATION /00Z Friday THROUGH Tuesday/...
VFR to MVFR conditions are expected for the next 24 hours.
Mainly VFR is expected tonight. An area of light rain/snow will
develop across western Ohio by 12z Friday with MVFR ceilings and
visibilities. Have this area of MVFR impacting TOL and FDY and
moving close to CLE and MFD during Friday morning. This precip
should decrease by midday and not really impact terminals in NE
OH or NW PA. West to northwest winds will slowly decrease this
evening and overnight to around 5 to 8 knots. Winds will become
light and variable by Friday morning and stay on the light side
during the day.
Outlook...Non-VFR possible across NE OH/NW PA with lake clouds
on Saturday. Non-VFR likely again Sunday into Monday with rain
and low ceilings. Non-VFR possible for the Snowbelt region with
lake effect snow showers Monday into Tuesday.
&&
.MARINE...
A very active weather pattern across the Great Lakes will keep
hazardous marine conditions around for the bulk of the forecast
period. Currently, low pressure centered over Quebec has resulted in
gale force winds from the northwest over the eastern basin of Lake
Erie, with waves of 6 to 8 feet. As a result, a Gale Warning remains
in effect until 7 PM this evening. The central and eastern basins
have sustained winds of 15-20 knots, building waves along the shore
to 2-5 feet, locally higher, maintaining Small Craft Advisory
criteria. The major change in headlines with this update is the
cancellation of the Low Water Advisory for the western basin. With
onshore flow and gradually weakening of winds into the evening,
waters levels are currently 35 inches above low water datum and are
expected to continue to rise, not reaching the critical mark of 18
inches above low water datum.
Conditions will gradually improve through the evening and overnight
hours as high pressure builds across the area for Friday. Another
low pressure moves across the region on Saturday, which will bring
marginal Small Craft conditions to the central and eastern basin.
Another weak high pressure will move in on Sunday before a much
stronger system impacts the Great Lakes on Sunday night into Monday.
The strongest impacts will be on Monday, with increasing confidence
in gales across all basins of Lake Erie. This system will need to
continue to be closely monitored.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...Small Craft Advisory until 7 AM EST Friday for LEZ145>149.
Small Craft Advisory until 10 PM EST this evening for
LEZ142>144.
&&
$$
SYNOPSIS...Garuckas
NEAR TERM...Garuckas/Griffin
SHORT TERM...Campbell
LONG TERM...Campbell
AVIATION...Griffin
MARINE...Campbell
Area Forecast Discussion
National Weather Service Goodland KS
850 PM MST Thu Dec 2 2021
.SHORT TERM...(This evening through Sunday Morning)
Issued at 127 PM MST Thu Dec 2 2021
To begin the short term period, the northwest flow that has been
present has flattened out. A strong inversion was present this
morning with RAP soundings indicating that it was as strong as 20
degrees C while the surface was just above 0 degrees C. As of mid
day the inversion has been slowly eroding allowing the warmer air
to make it to the surface. As of 12p MT all of our AWOS/ASOS
stations were above 70 degrees Fahrenheit; also interesting to
note that Hill City had broken their record high temperature at
11am CT. The temperature forecast still shows most if not all of
the area warming into the mid to upper 70s with perhaps a few
locales making it into the 80s as there is till another roughly 3
good hours of diurnal heating remaining. Into tonight, low level
flow becomes more SW in the vicinity of a trough. A cold front
moves N to S over the area overnight into Friday morning in
association with the eastward propagation of the trough. Winds
will shift to the NNW with the passage with winds picking up to
around 10-15 knots. Overnight lows look to fall into the mid 30s
to low 40s over the area.
Friday, winds will increase to 10-20 knots throughout the morning
with gusts of 25-35 knots possible, with the strongest winds mid to
late morning when the surface pressure change looks to be the
strongest. The stronger echelon of the wind gusts will be
dependent on if sufficient CAA will be available to help mix the
stronger winds to the surface. Temperatures look to be cooler, but
still above normal in the upper 50s to mid 60s over the area.
Overnight lows will be cooler in part to radiational cooling as
widespread 20s are expected over the area.
Saturday, cooler temperatures than Friday are expected with the
entire area seeing 50s. Winds will remain breezy as well as pressure
gradients tighten ahead of a developing surface trough over the
northern Rockies. Sustained southerly winds of 10-20 knots with
gusts up to 30 knots are currently expected. Winds begin to turn
towards the north overnight Saturday as another cold front begins to
move into the area. Saturday night lows look to fall into the lower
30s with clouds on the increase.
.LONG TERM...(Sunday through Thursday)
Issued at 143 PM MST Thu Dec 2 2021
This part of the forecast will be dry for the most part, except for
low chances for precipitation Tuesday as a cold front moves through.
Due to the upper level northwest flow shifting more over the
forecast area, the light wind days will be fewer than what has
happened recently. With the ridge shifting to our west, cooler air
will be allowed into the forecast area, bringing temperatures closer
to normal.
Sunday a cold front will move through. Behind the front north winds
will increase and temperatures will fall through the day. The
strongest winds will likely be in the morning, then gradually
decline through the day as the stronger winds shift east. Due to
the majority of the lift with this front being over the Midwest with
the trough, am not expecting any precipitation with the frontal
passage. Sunday night will be the coldest temperatures that have
been seen in a while. A surface high will move through, leading to
favorable radiational cooling (as long as clouds are few and far
between). This will cause lows to fall well into the teens. With dew
points in the single digits, wouldn`t be surprised if lows end up
being closer to ten degrees for most of the area.
The next cold front to move through will be Tuesday. Like Sunday,
temperatures will fall through the day behind the front. The upper
level pattern looks favorable for precipitation potential with the
passage, except for the potential split flow setup. The GFS clearly
shows the flow splitting over the forecast area, while the ECMWF is
much less suggestive but still evident. This is the only day for
precipitation chances for this week, but am doubtful anything more
than a few hundredths of an inch of precipitation will occur due to
the split flow potential. A reinforcing round of cold air will move
in Tuesday night. With dew points in the mid teens, the current low
forecast should see little change.
Toward the end of the week another trough moves onshore, then
deepens over the Desert Southwest. This will cause a ridge to form
over the Plains. This will lead to precipitation for the Plains,
the question is where at this point.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 850 PM MST Thu Dec 2 2021
KGLD...VFR conditions through the period. A west wind near 10kts
at taf issuance will veer to the northwest at similar speeds
through sunrise as a cold front moves through. During the day
Friday north winds gusting around 25kts are expected. For the
evening hours winds subside and steadily veer to the east at
speeds around 5kts.
KMCK...VFR conditions through the period. A west wind up to 10kts
at taf issuance will veer to the north at 11kts through sunrise as
a cold front moves through. During the day Friday north winds
gusting around 25kts are expected. For the evening hours winds
decrease below 11kts while veering to the east.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...TT
LONG TERM...JTL
AVIATION...99
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
807 PM CST Thu Dec 2 2021
.UPDATE...
Issued at 807 PM CST Thu Dec 2 2021
The forecast appears to be on track. As expected, a band of
showers is developing from southern South Dakota to central
Minnesota associated with increasing mid-level frontogenetical
forcing and upper-level diffluence in the right entrance region of
an elongated jet streak over the northern Great Lakes. Light
radar returns have also started to appear in northeastern Iowa in
response to increasing low-level frontogenetical forcing ahead of an
approaching but subtle mid-level wave, which leverages confidence
in the forecast scenario outlined in the short term discussion
below. A quick look at the incoming 00Z guidance does not provide
any additional insight into how the low-level thermal profile may
look about 6 to 12 hours from now, with forecast hrrr profiles
literally right on the line between rain/snow at Waukegan. Perhaps
one factor that may tip the scales toward rain will be modest
low-level advection off the warm and moist waters of Lake
Michigan, which may anchor wet bulb temperatures above freezing.
However, it`ll still be way too close for comfort and we would
not be surprised at all if a narrow band of slushy/wet snow
accumulates from Sharon, WI to Lake Forest, IL. Strong
frontogenetical bands of precipitation often have a sharp southern
edge, and indeed areas along and south of a line from Rockford to
Chicago look to remain dry through the next 12 hours.
Updated products will be sent shortly.
Borchardt
&&
.SHORT TERM...
Issued at 252 PM CST Thu Dec 2 2021
Through Friday night...
The primary forecast note for the short term is the low
probability of a short burst of snow late tonight/very early
Friday morning for mainly far northeast Illinois. Otherwise, the
main message is cooler Friday but still above normal.
Sunny, breezy, dry, and mild conditions prevail this second day
of Meteorological Winter, as a couple 60 degrees highs have shown
up south of I-80. Winds will drop off quickly after sundown as a
1017 mb surface high pressure ridge shifts over the area this
evening. In general, this will favor a good radiational cooling
evening, especially as cooler 925 mb temperatures have oozed into
the area from the north. However, mid-level clouds that have their
front edge pushing across southern Minnesota this afternoon will
spread over locations north of I-80 this evening. This should slow
the diurnal drop there and that does become somewhat key as the
best chance for late night precipitation is near the Wisconsin
state line. Have lows fading into the mid 30s in this area, with
dew points recovering some from current mid 20s to the upper 20s
by late tonight.
A 135+ kt jet stream extends from southern British Columbia all
the way through the Great Lakes, with a 150+ kt maximum moving
from the North Dakota/Canada border to Lower Michigan by Friday
morning. As that jet max translates, it will send a very low
amplitude mid-level wave toward southern Wisconsin and, more
noteworthy, increase a lower to mid tropospheric frontogenetic
(f-gen) circulation. Guidance today has continued the trend of an
increasing signal of enough saturation with this for QPF clipping
at least the far northern Chicago metro. While the overlapping
signal in guidance remains better for north of the state line and
still fairly large spatial uncertainty on the southern periphery,
there was enough of a high-resolution signal to further increase
PoPs for Lake and McHenry Counties and a slight boost in adjacent
areas. The main timing looks to be ~2-7 A.M.
Deterministic soundings from the NAM, GFS, RAP, and HRRR
(irregardless of whether they show precipitation) do show
marginally warm enough profiles for melting aloft. Further below,
the profiles in the boundary layer are also marginal, and some
dependency on evening trends as noted earlier. So rates of any
precipitation will likely be key in changeover and impacts, and
that will be tied to enough well-aligned, negative saturated EPV
(instability) on the warm side of the circulation above the f-gen.
In general the models do show that, so feel that if there is an
established f-gen band into far northern Illinois, it likely will
turn precipitation type over to snow. Given the time of day, some
minor accumulations would be possible with this including on
roads. The potential for this to occur to impacting levels still
remains on the less likely side of the spectrum of outcomes. The
evening shift will keep a close eye on it though to see if trends
support an increasing chance of impacts.
Any early morning precipitation will be shifting out fairly
quickly. Clouds though will probably linger into the afternoon in
northeast Illinois and far northwest Indiana, keeping highs south
of 50. But elsewhere, should be able to top that again on Friday.
MTF
&&
.LONG TERM...
Issued at 224 PM CST Thu Dec 2 2021
Saturday through Thursday...
A more active pattern is on the horizon with a couple storm
systems requiring close monitoring late this weekend and again
during the middle of next week.
Strong WNW aloft will remain over the Great Lakes region on
Saturday as surface high pressure rapidly advances from southern
MN to southern Lower MI through the day. Seasonable temps in the
low 40s under mostly sunny skies are expected. Modest mixing into
an exceptionally dry airmass aloft should allow dew points to fall
into the teens to possibly locally single digits above zero
across northern Illinois.
Extensive low-level WAA will commence Saturday evening and
continue well into Sunday ahead of broad low pressure shifting
east from the central Great Plains. Initial low-level trajectories
from the southeast will not be ideal for moisture advection into
the area until significant veering occurs toward daybreak Sunday.
Therefore, there remains low confidence that sufficient moisture
will advect into the area to support precip by daybreak Sunday.
However, the substantially dry low-levels will result in surface
wet-bulb temps remaining below freezing across much of the area
potentially into mid-morning. Given an increasingly warmer profile
aloft, initial precip will be primarily liquid, indicating at
least a low risk of light freezing rain around daybreak Sunday.
Air and wetbulb temps will quickly rise through the morning,
supporting all rain beyond mid-morning. An expanding rain shield
will then affect much of the area through the day and across the
southeast half into the evening.
Precip will end late Sunday evening as a mid-level dry slot
advects into the area, but scattered snow showers will likely
affect northern Illinois late Sunday night into Monday morning as
the upper- trough brushes the area to the northeast. Strong winds
NW winds gusting to 30 mph combined with modest low-level lapse
rates support the potential for some briefly heavier snow bursts.
Dry conditions should prevail Monday afternoon and night before
low pressure developing across the central CONUS brings unsettled
weather to the region Tuesday into Wednesday. Phasing issues with
a split trough exiting the western CONUS on Tuesday support a
varying range of solutions, from the potential for some
accumulating snow in the CWA to a N/S split of most precip around
much of Illinois.
Kluber
&&
.AVIATION...
For the 00Z TAFs...
Forecast concerns for the terminals...
*Increasing cloud cover with VFR ceilings tonight.
*Chance for a mix of light rain/snow showers late tonight through
Friday morning.
*Light and variable winds Friday.
High pressure resides over the area this evening which is keeping
the terminals under mostly cloud-free conditions with the
exception of a few cirrus clouds overhead. However, a weak frontal
boundary is advancing towards the area which will bring in more
cloud cover overnight tonight with VFR ceilings that will linger
through the day on Friday. Along with the clouds, the frontal
boundary will also bring the chance for light rain/snow showers
across northeastern Illinois with the best chances for
precipitation being along the Illinois-Wisconsin border. However,
sufficient forcing with the boundary may allow showers to move as
far south as the terminals after midnight and lingering through
daybreak. Guidance suggests that rain showers are likely to be the
dominant precipitation type as forecast soundings look to remain
just above freezing in the lower levels, but a slight shift in
temperatures due to evaporative cooling would favor a few snow
flakes mixing in.
Winds will remain light and turn generally northeast overnight
before shifting southeasterly after daybreak. Winds will remain
less than 10 kts throughout the day on Friday with winds backing
towards the east and northeast in the evening.
Yack
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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AREA FORECAST DISCUSSION
National Weather Service Morristown TN
1022 PM EST Thu Dec 2 2021
.UPDATE...
EVENING UPDATE.
&&
.DISCUSSION...
Passing high clouds across the northern valley and portions of
southwest VA have kept diurnal cooling at bay over the last few
hours, while in the southern valley temperatures are cooling
nicely. Thus blended in a little HRRR tonight for temperatures
which favored those trends the best. On that, am expecting some
patchy fog in the river valleys tonight given cooling, thus such
was added. No other changes needed/made with this update.
CDG
&&
.AVIATION...
00Z TAF DISCUSSION.
VFR through the period at all sites with the possible exception of
light patchy MVFR fog at TRI around daybreak per xover
temp analysis and HREF probs, thus such was included via tempo.
Otherwise, swly winds will gradually weaken through the
evening/overnight as PGFs relax favoring light swly flow on Friday
amidst SKC or high cirrus with some moisture advection late in the
period from the southwest favoring increased sky cover after
periods end.
CDG
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 44 70 48 68 48 / 0 0 0 10 10
Knoxville McGhee Tyson Airport, TN 44 68 47 63 45 / 0 0 0 10 10
Oak Ridge, TN 42 66 46 62 45 / 0 0 0 10 10
Tri Cities Airport, TN 41 64 43 59 41 / 0 0 0 10 10
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
Area Forecast Discussion
National Weather Service Pocatello ID
149 PM MST Thu Dec 2 2021
.SHORT TERM...Tonight through Sunday. Flat upper ridge remains in
place with upper jet centered along the Canadian border, keeping
East Idaho on the northern extent of high pressure across the
Great Basin. Patchy fog is still possible overnight tonight into
early Friday, and then again Friday night into Saturday morning.
At this time, do not expect widespread visibility issues for the
Snake Plain and surrounding lower elevation areas, especially
those along waterways. Temperatures remain mild/above normal into
Saturday, ahead of cold front that drops across the region during
the day. This system may produce a few light showers across higher
elevations to the north and along the Divide late Saturday into
Saturday night, but accumulations look to remain minor. Of more
concern is the winds associated with the front as the surface low
steeps significantly as it moves through Montana into Wyoming.
700mb winds >50kts combined with strong mixing look supportive of
winds approaching Wind Advisory late in the day, and continuing
past sunset, and possibly past midnight as well. Higher
elevations across the central mountains could take the brunt of
the wind, but the amount of blowable snowpack even at higher
elevations is a question. Winds should weaken after midnight, with
cooler temperatures headed into Sunday. This frontal system looks
like the prelude into a more unsettled work week, and some much
needed precipitation. The Long Term discussion below has more
details on the next system to arrive early in the work week. DMH
.LONG TERM...Sunday night through Thursday. A fairly robust upper
trough will work its way in from the northwest on Monday. The trough
should cover the vast majority of the forecast area in rain and/or
snow. Snow levels are coming in a bit lower than previous forecast,
coming to valley floors early Tuesday morning. GFS is back to a
split system as it passes through Idaho with the ECMWF keeping a
more consolidated trough. As a result, ECMWF is a tad more
progressive than the GFS; however, the end result from both
solutions is similar. Snow amounts Monday and Tuesday will add up to
an inch or less in the Snake Plain. Eastern Highlands should see
about 7 to 10 inches with over 12 inches at the highest peaks along
the WY border. Central Mountains will likely see 7 to 10 inches, and
about 2 to 5 inches around pass levels.
Another similar-looking weather system will drop in from the
northwest on Wednesday, though model consensus is lacking right now.
GFS again proposes a split system while the ECMWF again is more
progressive and consolidated with the trough. Day 6 and 7 have
chance to likely PoPs though with temperatures and snow levels
supporting snow. Accumulations will be difficult to predict at this
point as ensembles are vastly spread. Hinsberger
&&
.AVIATION...TAF sites are mostly clear today as high pressure
remains in control. Satellite imagery shows some fog/stratus in the
Upper Snake Plain that the HRRR and HREF expand down the valley
early tomorrow morning. HRRR visibility progs blanket IDA and PIH in
dense fog in the morning, though NBM highly favors VFR conditions at
both sites. Tough decision to make, as PIH/IDA could either stay VFR
or be below airfield minimums for the morning. Keeping other sites
VFR, but taking PIH and IDA to minimums. Hinsberger
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$