Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/04/21
Area Forecast Discussion
National Weather Service La Crosse WI
507 PM CST Fri Dec 3 2021
.SHORT TERM...(Tonight through Saturday)
Issued at 241 PM CST Fri Dec 3 2021
Broad northwest flow continues across the area with generally quiet
weather on tap to start the weekend. Subtle cold front is
approaching forecast area from central Minnesota this afternoon with
stratus field associated with it. Weak feature has no precipitation
associated with it at this time but will kick up winds for a short
time.
Otherwise seasonal temperatures expected with short term ridging
Saturday.
.LONG TERM...(Saturday night through Friday)
Issued at 241 PM CST Fri Dec 3 2021
The weather will get far more active for the 2nd half of the weekend
and into Monday as upper flow amplifies.
Upstream short wave of notice will be approaching the Northern
Rockies on Saturday with response noted just to the west of us by
Saturday evening. This will be in the form of impressive warm air
advection and associated lift that could lead to initial band of
snow in mid level frontogenesis region mainly across far northern
areas. Trends for this area have been shifting north slightly so
unsure if this initial precipitation will have much impact. CAMS in
agreement with idea but differ a bit on how far south precipitation
may reach.
This same wave is predicted to deepen and strengthen as it
approaches the Great Lakes. Continued forcing and lift will likely
result in more widespread saturation, especially as wave moves east.
Sunday morning will be time that precipitation fills in and sweeps
through with short duration along and ahead of front, and perhaps
longer duration further north. Precipitation types could be brief
issue with some melting aloft along and south of I-90 and perhaps
all liquid along and south of Highway 20.
Then finally, as wave swings through, could see round of wrap around
precipitation that will change over to all snow Sunday night. Again,
this scenario would mean higher potential snowfall the further north
you go with little if any to the south. Due to the more prolonged
threat across parts of north central Wisconsin, several inches of
snow could fall by the time system exits so will need to monitor for
possible advisory impacts.
Another facet to this dynamic system will be wind. Deepening
characteristic and subsidence will lead to increase in winds Sunday
night into Monday. Strong mid level winds, on back side especially,
could mix to surface and reach or approach advisory levels early
Monday, especially in wind prone areas across southern Minnesota.
Since blend of models tends to undercut these higher wind scenarios,
bumped wind fields closer to 90th percentile to catch potential for
stronger gusts.
Not much time devoted to later periods but another wave Tuesday
could bring some light precipitation through the area as colder air
settled back in next week. Also will be watching potential for
stronger system late next week as CONUS pattern becomes even more
amplified.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 507 PM CST Fri Dec 3 2021
A rather narrow band of MVFR ceilings were advancing across
southern Minnesota with some signs of also slowly dissipating.
The RAP seems to have a decent handle on this moisture and
suggests there is some potential for these clouds to reach KRST
this evening but should break up before getting to KLSE and as a
result, have included a short window of MVFR ceilings for KRST.
After that, a large area of high pressure will build in overnight
and move across the region Saturday. General VFR conditions are
expected from the high.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Shea
LONG TERM...Shea
AVIATION...04
Area Forecast Discussion
National Weather Service Bismarck ND
938 PM CST Fri Dec 3 2021
.UPDATE...
Issued at 937 PM CST Fri Dec 3 2021
00Z guidance has shifted the frontogenesis/isentropic ascent band
of lighter snow tonight through Saturday morning a bit farther
south, starting earlier and with a slower northward progression.
The most notable change for this update was to PoPs, as snow
amounts were only increased by a few tenths of an inch at most in
southwest North Dakota. Despite surface dewpoint depressions
remaining quite high, model soundings suggest ceilings lowering
enough to allow hydrometeors to survive the shallow layer of dry
air.
While the most recent guidance has maintained a general
consistency with overall snow totals, a few 00Z models are showing
a slight southward shift across the eastern half of North Dakota.
Additionally, there continues to be concerns about very strong
winds across southern North Dakota on Sunday, as was addressed in
the previous update. NBM 90th percentile wind guidance has
increased, but remains below 35 kts sustained and 50 kt gusts,
which is warning criteria. Therefore, we will hold off on any
wind headlines for now, but all ingredients are still present in
deterministic guidance for a potential high wind event.
The one headline change that was made with this update was to
expand the Winter Storm Watch into Stutsman County, prompted by
increasing probabilities for higher snow amounts combined with
stronger winds.
UPDATE Issued at 604 PM CST Fri Dec 3 2021
No major changes were made for this update. The latest model data
were blended into the forecast through Saturday evening, which up
to that point, does not change our overall thinking and messaging
for the upcoming storm system.
Recent extended runs of the HRRR and RAP show a concerning
potential for very strong winds across southwest and south
central North Dakota early Sunday morning through the afternoon.
Most, if not all ingredients needed for efficient mixing of mean
boundary layer winds to the surface appear to be in place,
including strong pressure rises, cold air advection, steep low
level lapse rates, and a chance of precipitation. The RAP is
simulating mean BL winds (900-800 mb as a proxy) around 50-55 kts,
and other deterministic models are only around 5 kts lower. If
the model trend of increasing potential for warning criteria winds
continues, our headlines and messaging may need to be re-
evaluated. Thankfully, the strongest winds are expected in areas
with much lower forecast snow amounts, and will not intensify
there until long after the majority of accumulating snow has
fallen.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 325 PM CST Fri Dec 3 2021
Accumulating snowfall Saturday through Sunday morning, with strong
winds and blowing snow through the day Sunday highlight the short
term forecast period.
Surface pressure this afternoon was relatively diffuse as a post-
front high had built in this morning. To the north and central
where a modest gradient remained, breezy northwest winds were
observed. Mid-level clouds were streaming in from the west through
strong flow aloft, but otherwise the weather situation was benign
this afternoon.
On Saturday, chances for snow will increase as a potent mid-level
shortwave crosses the Northern Rockies and leading isentropic lift
develops over southern North Dakota. Through the day the low-mid
level baroclinic zone by which this ascent is associated with
will lift north as the shortwave approaches. Light snow is likely
along the track of this frontal zone, with minor accumulations
expected initially. By the afternoon hours, divergence aloft will
increase with the approaching shortwave, which combining with the
lower level baroclinic zone will begin to increase snowfall rates
over northwest North Dakota. Here is where 1"-2" of accumulation
will be possible by the evening hours, with moderate to heavy
snowfall rates then spreading east over northern North Dakota
through Saturday night.
The duration of heavy rates however remains in question, as this
would likely require persistent mesoscale banding to occur and the
necessary ingredients displayed by 12Z guidance remains somewhat
out of sync or too transient for a strong significant
accumulation signal at any one location. Q-Vector convergence
associated with the left exit region of the upstream jet is
strongest late Saturday night, generally behind the 700mb
frontogenesis signal, and more in line with frontogenesis at 850mb
due to the nature of the sloped front. In forecast soundings this
creates a transient and relatively short- lived duration of
strong ascent through the DGZ. That`s not to say moderate to heavy
snowfall rates within mesoscale bands are not possible, but the
development and certainly placement remain uncertain even at this
lead time. Thus while accumulating snow is likely across much of
the forecast area north of the I-94 corridor, location
predictability for warning criteria with 6+ inches of snow remains
in question. 12Z global guidance does paint some sort of
predictability solution, with many ensemble members still landing
the heaviest QPF near and north of Highway 2, with a tilt
southeast towards the northern James River. The 6 inch probability
from both ECMWF and GFS ensemble members agree in this area, but
remain rather low (maxing at 50% for both) due to the spread in
locations of the heaviest band. This keeps the going Winter Storm
Watch in good standing, but consensus for headline upgrades has
yet to be reached.
Strong winds are expected to materialize as the surface low
deepens while a cold front drives southeast during the day Sunday.
Strong pressure rises associated with the front and moderate 850mb
flow will create strong sustained winds likely to blow and loft
fresh fallen snow, as well as lingering wrap around falling snow.
Overall the strongest wind wind should lag behind the heavier
snowfall rates which will help mitigate high end visibility
concerns, though some impacts to travel are still likely.
.LONG TERM...(Sunday night through Friday)
Issued at 325 PM CST Fri Dec 3 2021
Cold temperatures are expected Monday, with very cold wind chills
possible over northern North Dakota Monday morning.
A strong push of cold air is expected Sunday night in the wake of
this system, resulting in very cold temperatures Sunday night and
Monday morning. ECS/MET/MAV are all in good agreement with NBM
guidance for morning lows, with double digits below north to
single digits above south. Wind chills will be a concern Monday
morning depending on the lingering pressure gradient and the
building surface high, but even with lower winds in the morning
forecast wind chills fall to around 25 below far north. Cold
daytime highs Monday are expected while the surface high drifts
across the state, around zero northeast to around 20 far
southwest.
The remainder of next week still looks relatively active, with
several low amplitude waves set to bring chances for
precipitation, though predictability in precipitation at any
one location is very low. In this active flow temperatures
moderate somewhat towards mid-week, followed by a cool down to end
the week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 937 PM CST Fri Dec 3 2021
VFR conditions are expected through tonight. A strong low pressure
system will bring accumulating snow and strong winds to the region
beginning Saturday morning. The snow will begin in southwest North
Dakota Saturday morning and progress north and east through the
day, barely reaching KMOT and KJMS by the end of this forecast
period. Expect MVFR ceilings and IFR visibility associated with
the falling snow. Southeasterly winds will increase to 15-20 kts
Saturday afternoon, with gusts near 30 kts.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Saturday afternoon through Sunday
afternoon for NDZ001>003-009>011-021.
Winter Storm Watch from Saturday afternoon through Sunday
afternoon for NDZ004-005-012-013-022-023-025-037.
&&
$$
UPDATE...Hollan
SHORT TERM...AE
LONG TERM...AE
AVIATION...Hollan
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1053 PM EST Fri Dec 3 2021
.AVIATION...
Remnant low level moisture will maintain some intervals of MVFR to
low VFR ceiling tonight, but with the southern fringe most likely
eroding into the I-94 corridor. Ceiling heights are expected to lift
and then scatter out by Saturday afternoon as west to northwest flow
develops in the wake of passing cold front. Wind gusts to 20 knots
or so will be possible with this front as well.
.DTW THRESHOLD PROBABILITIES...
* High for for ceilings of 5000 feet or less tonight, medium on
Saturday morning.
&&
.PREV DISCUSSION...
Issued at 405 PM EST Fri Dec 3 2021
DISCUSSION...
Northwest flow pattern remains locked in place for the time being.
The polar jet is impressively strong with a series of 150 knot jet
streaks racing through the low amplitude upper trough. With the
southern MI wave now in our wake, we turn the attention to the next
wave racing through the flow across northern lower this evening.
Region radar is running hotter than the hires suite with a broader
coverage of reflectivity. We`ve been watching the potentially for
the southern edge of this wave to clip the Saginaw Valley and Thumb
as it fights the weak ridge building in from the west. Decided to
add a small area of isolated rain/snow showers for this evening to
capture this system. Observations have yet to verify the broader
coverage on radar, but with RAP soundings showing saturation up to
8kft, nearing the -10C layer, won`t be too surprised to see a few
flakes or raindrops get squeezed out.
Once this system tracks over Lake Huron, drier conditions will take
over for the rest of the overnight and through Saturday with the
high sliding through the western Great Lakes. Thermal advection will
be weak if not neutral on Saturday so expect high temps in the upper
30s once again for most with some lower 40s sneaking up into the
Detroit area.
A stronger system remains on tap for Sunday and Monday. The next 150
knot jet max will come ashore causing the nearly linear polar jet to
ripple with cyclogenesis then occuring just east of the Rockies
Sunday. A deep trough will quickly form over the Plains and lift
through the Great Lakes Monday. The leading isentropic arm will
start reaching into Mid MI early Sunday morning but 8-10kft dry
layer extending up from the surface will make it hard to realize any
snow from this feature. We will then enter the warm sector though
the first half of the day with strong warm advection bringing highs
into the low 50s. Moderate to heavy rain showers will then spread
across the region in the afternoon/evening ahead of the cold front.
Still looking for around 0.5 inch or more of QPF by the time the
precip tapers off Monday morning. Though primarily rain for most of
SE MI, local probability graphics support mid range model soundings
with a chance of mixed precip over MI Mid as colder temps hold. this
could change with a slight change in storm track but for now will
keep a mention in the forecast. Current trends as for a slightly
slower storm track which favors the rain scenario as the precip
wouldn`t start til the heart of the day with warm advection well
under way.
The rapidly deepening low will send a cold front through early
Monday ushering out the synoptic rain and will then open the door
for the lake effect precip to begin. Cold advection will begin in
the morning but really kick in behind the passage of the mid level
trough axis early afternoon Monday. A strong wind event still look
possible as deep layer mixing due to CAA attempts to bring down the
strong winds aloft with 40 knots down to about 2kft and potential
for 50 knots around 4-5kft. Local probabilities have come down
slightly the last 24 hours but will hold with the current forecast
of 30-40 mph winds Monday for now. Especially considering lake
effect snow showers will be ongoing and may locally increase chances
to mix down the stronger winds.
Will be dealing with a diminishing lake effect trend overnight Monday
with some lingering westerly wind gusts to around 20 mph on Tuesday.
high pressure building across the area will support a dry forecast
but the next precip maker is already targeting the area for
Wednesday. This system has been advertised in the models for a few
days now but has been pushed back 24 hours already as it deals with
a northern stream trough and southern stream wave phasing.
MARINE...
Departing high pressure keeps a relaxed surface gradient and light
W/SW flow around through the rest of the afternoon and evening
period. Approaching low pressure to then enhance the surface
gradient and low-level wind field late tonight, with winds ramping
up to gale criteria overnight. Given high confidence in gusts
reaching gales, the Gale Watch was upgraded to a Gale Warning during
the morning update. Peak of the gale event will be daytime tomorrow,
following the passage of an early morning cold front. Northwesterly
winds post-front push enough cold air over the lakes to mix 35+ kt
gusts to the surface during the daylight hours. Majority of the
nearshore zones remain aob 25 kt gusts, with the exception of Outer
Saginaw Bay and Port Austin-Harbor Beach where northwesterly flow
builds waves of 3-5 ft and supports gusts at or slightly above 30
kts. Winds to diminish late tomorrow evening before ramping up once
again ahead of a strong disturbance approaching the Great Lakes
Sunday-Monday. Increasing confidence in gale potential for this
timeframe as well.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Gale Warning from 2 AM to 10 PM EST Saturday for LHZ361-362.
Small Craft Advisory from 2 AM to 10 PM EST Saturday for LHZ421-441.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
AVIATION.....DG
DISCUSSION...DRK
MARINE.......MV
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Lincoln IL
826 PM CST Fri Dec 3 2021
.SYNOPSIS...
Issued at 208 PM CST Fri Dec 3 2021
Cooler weather will follow the passage of a cold front this
evening, though temperatures will still be a bit above early
December normals on Saturday. Another mild day is expected Sunday
as the next storm system moves into the region. This system will
bring windy conditions, as well as periods of rain.
&&
.UPDATE...
Issued at 826 PM CST Fri Dec 3 2021
Low pressure has exited out of southeast Illinois, allowing
northerly winds to become established across the area. High
pressure will continue to build into central IL from the
northwest, eventually producing increasing N-NE winds after
midnight. HRRR and GFSLAMP guidance continue to advertise an area
of low clouds and fog developing just north of Bloomington to
Kankakee around 3 am, then advancing southward through our eastern
counties through 8 am. Not seeing enough evidence in the dewpoint
depressions across that area to introduce fog, but we already
indicate some increasing clouds later tonight across that area.
Low temps will respond to the cold air advancing southward behind
the low pressure, dropping to around 30 from Galesburg to Lacon.
Low to mid 30s will prevail elsewhere in central IL, with upper
30s south of I-70. No notable updates are needed to the overnight
forecast at this point.
&&
.SHORT TERM...(This evening through Saturday)
ISSUED AT 208 PM CST Fri Dec 3 2021
Another pleasant early-December day with abundant sunshine and
temperatures in the 50s/60s. Latest surface map shows weak low
pressure centered near Effingham, with its attendant cold front
stretching across the northern St. Louis metro. This front should
slip south of I-70 early this evening. No significant impacts
expected in its wake, though northerly winds pick up a bit after
midnight as high pressure builds in from the northwest. This high
should pass just to our north on Saturday, keeping our weather
dry. While temperatures will be cooler than today, they will still
be a bit above seasonal normals with highs in the mid 40s north to
low 50s south of I-70.
.LONG TERM...(Saturday night through Friday)
ISSUED AT 208 PM CST Fri Dec 3 2021
Zonal upper pattern begins to break down later this weekend, as a
shortwave moves out of the Canadian prairies. Main core of the
surface cyclone will be across the upper Mississippi Valley, with
the net effect for us being windy conditions Sunday/Monday as well
as periods of rain. Some potential for over a half inch of rain
south of I-70 from this system with a surge of moisture coming
from the southwest. Will keep a mention of isolated thunder east
of I-57 as well Sunday evening ahead of the front. Another mild
day ahead of the front on Sunday, close to today though a bit
cooler.
Not a lot of consistency in the models with the Tuesday storm
system. Latest European model is trending more toward Tuesday
afternoon/night, while the GFS has more of a two-pronged system
with greater energy sliding up the Ohio Valley Tuesday night.
European ensemble show about a 30% chance of an inch of snow
north of I-74 with the GFS a bit more widespread in that regard
and the NBM in the 40-50% range. Will concentrate the higher PoP`s
during the nighttime hours. Not looking like anything major at
this point, but with it being the first widespread accumulation
potential, it`s something to grab people`s attention.
Several upper waves are projected to traverse the CONUS during the
second half of the week, with indications of another milder spell
over the eastern U.S. Timing of a system Thursday night is a
bit variable, but may result in additional rain or snow mention in
future forecasts.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 602 PM CST Fri Dec 3 2021
Primarily VFR conditions expected the next 24 hours. The latest
HRRR and GFS are pointing toward some patchy fog and MVFR clouds
could develop in NE IL and drift south across BMI, DEC and CMI
between 08z and 12z tonight. We did introduce IFR vis and SCT015
at BMI to acknowledge that possibility. Will monitor closely for
updates through the evening. Winds will be N-NE in the wake of a
surface low that just passed across our SE counties. Speeds around
10 knots are expected to develop late this evening and continue
through tomorrow.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Shimon
SYNOPSIS...Geelhart
SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Shimon
Area Forecast Discussion
National Weather Service San Angelo TX
547 PM CST Fri Dec 3 2021
...New AVIATION...
.SHORT TERM...
(This evening through Saturday)
Issued at 203 PM CST Fri Dec 3 2021
The shortwave trough that brought scattered showers and a few
lightning strikes to our eastern counties this morning is pushing
off to the east of the area. Skies have gone mostly sunny in the
wake of the trough. The clear skies in combination with downsloping
southwest winds has resulted in well above normal conditions once
again this afternoon. Temperatures are even a couple of degrees
warmer than yesterday, with most locations currently sitting in
the mid to upper 80s as of the 2 PM hour. For tonight, lows will
dip back down into the 40s in the Big Country and the 50s
elsewhere. Though not mentioned in the grids, some patchy fog or
mist is possible along the I-10 corridor in the morning hours.
A cold front is still expected to move across the area on
Saturday. The NAM continues to be the colder than the GFS, with
the NAM MOS a good 10-15 degrees cooler than the GFS MOS guidance.
Will stick with the NBM which is closer to the GEFS mean and RAP
and HRRR models but not quite as cold as the NAM. Temperatures
will be coolest in the Big Country (lower to mid 60s), with mid
70s to lower 80s across the southern half of the area.
&&
.LONG TERM...
(Saturday night through next Friday)
Issued at 200 PM CST Fri Dec 3 2021
Breezy southwest winds and warmer temperatures quickly return on
Sunday, ahead of a stronger cold front that will affect the area
Sunday night and early Monday. Temperatures will be above normal
once again, with afternoon highs in the mid and upper 70s. The
cold front will move across the area Sunday night and clear far
southern counties just before daybreak Monday morning. Gusty
north winds will follow the front but will diminish across the
area during the afternoon hours. Highs on Monday will range from
the lower 50s across the Big Country, to the upper 50s and lower
60s south of the I-10 corridor. Expect light winds Monday night,
with overnight lows in the upper 30s and lower 40s. Tuesday will
be warmer, with highs mainly in the upper 60s and lower 70s.
Could see a few showers develop over far southeast counties
Tuesday morning as weak shortwave moves through, otherwise dry
weather will persist.
The rest of the week looks dry, with another weak front possible
by Wednesday, followed by above normal temperatures again by
Thursday and Friday.
&&
.AVIATION...
(00Z TAFS)
Issued at 546 PM CST Fri Dec 3 2021
VFR conditions expected through late this evening, with some MVFR
conditions possible by around sunrise. A weak frontal boundary
will push through the region tomorrow, shifting winds to the
northwest, but should remain under 10 knots during this time.
&&
.PRELIMINARY POINT TEMPS/POPS...
Abilene 50 67 48 77 / 0 0 5 0
San Angelo 52 74 51 77 / 0 0 5 5
Junction 55 81 56 76 / 0 0 5 5
Brownwood 54 75 49 78 / 0 0 5 5
Sweetwater 48 67 50 77 / 0 0 0 0
Ozona 52 75 54 73 / 0 0 5 5
&&
.SJT WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...42
LONG TERM....24
AVIATION...SK