Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/06/21
Area Forecast Discussion
National Weather Service Binghamton NY
1041 PM EST Sun Dec 5 2021
Winds will be increasing tonight with the strongest winds
expected in the Finger Lakes region where gusts to 50 mph are
possible. A cold front moves through Monday, bringing rain
showers tonight into tomorrow morning. Lake effect snow develops
late Monday lasting into Tuesday with minor snow accumulation
expected in favored areas.
.NEAR TERM /THROUGH MONDAY NIGHT/...
1030 PM Update...
Decided to expand the wind advisory to include the Twin Tiers,
Otsego and Delaware Counties and also Southern Oneida County.
Current thinking is that there may be a few spotty gusts across
higher terrain that near advisory criteria in these counties
overnight. Already getting some isolated reports of trees and
wires down in Broome County and gusts have only been in the 35
to 40 mph range. Tomorrow, with cold FROPA, widespread gusts in
the 40 to 50 mph range will be possible. BUFKIT soundings
showing momentum transfer over 40 knots in most locations as the
mixing layer lifts to near 4K feet behind the front. HRRR is
usually a bit overdone with wind gusts, but it is indicating
gusts over 50 knots in some spots and widespread 40 to 45 knot
gusts just behind the front. There is also some concern further
south into the Poconos for tomorrow afternoon and evening, but
will hold off from expanding the advisory any further for now,
and will let oncoming shifts reevaluate when 0Z model guidance
comes in later tonight.
9 PM Update...
Temperatures are warming a bit earlier than expected as low
level jet starts to punch into the region. Have increased low
temperatures overnight as temperatures should continue to warm
through the overnight hours and may near 50 degrees in some
spots across the Finger Lakes Region and into Syracuse before
sunrise. Winds are also increasing, with the wind advisory going
into effect in the next hour. So far, a few isolated gusts above
40 mph have been observed, but higher wind gusts will become
more widespread and frequent over the next few hours,
especially across the higher elevations from Steuben County
northeast into Onondaga County.
530 PM Update...
Forecast remains mostly on-track at this time. Only change made
was to increase cloud cover this evening, as overcast skies
have taken over most of the forecast area based on latest
satellite and observations.
330 PM Update...
The main concern with the near term is the strong winds tonight
through tomorrow afternoon. The area of high pressure that
brought the quiet weather today is propagating to the east and
strengthening. A deepening low in the Great Lakes region moves
NE into southern Canada lifting a warm front through the
Northeast tonight. A strengthening low level jet develops as the
pressure gradient tightens between the strengthening high and
the deepening low. 925 to 850 mb winds increase to 45-55 knots
across NE PA into the Catskills with 55-65 knots across CNY and
the Finger Lakes region. A wind advisory has been posted for
most of the Finger Lakes and CNY with downsloping winds helping
to mix some of these higher winds down. Forecast soundings do
show a strong inversion just above the surface so that will help
prevent the strongest winds from mixing down but widespread
40-50 mph wind gusts are still expected with an outside chance
of isolated 60 mph wind gusts possible on hill tops and favored
downslope areas in the Finger Lakes region.
Temperatures increase overnight as 850 mb temps rise to nearly
10C with upper 40s and 50s by sunrise region wide. A cold front
then approaches from the west by mid to lake morning Monday with
falling temperatures in the afternoon. Rain showers out ahead of
the front brings wet conditions to the region most of the
morning as well as some fog over the higher terrain of the
Poconos and Catskills as low LCLs develop with the moist
airmass advecting in ahead of the front. The highest rain totals
are expected across the southern Tug Hill as well as south
facing slopes of the Catskills and Poconos as upslope flow
enhances the precipitation.
Winds shift to the W after the cold front moves through.
Residual post frontal rain showers transition to snow showers
but coverage will be spotty in the afternoon. Lapse rates
steepen as CAA takes over with winds still around 35-45 knots at
925 to 850 mb so gusty winds will continue through the
afternoon. The wind advisory goes until 7 pm Monday as the
winds begin to slacken though gusts to near 40 mph will still be
possible through the early Monday evening.
As CAA continues at 850 mb and temps fall to around -10c Monday
night, lake effect snow develops downwind of Lake Ontario with
northern Oneida Co seeing the band. Winds in the lower
atmosphere will be shifting through the night from W to NW so
the band is expected to be fairly transient and not sitting
over one area for too long. Snow accumulations of 1-3 inches
with isolated areas of up to 4 inches is possible in northern
Oneida and an inch or less further south into the NY thruway
.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
250 pm update...
A cool but seasonal air mass will be in place Tuesday and
Wednesday with a period lake effect snow on Tuesday, then a
broad area of light snow possible late Tue night into Wednesday.
A weak cyclonic flow will be in place Tuesday morning embedded
within an air mass defined by 850mb temps around -11 to -13 deg
C. Low level winds from the west will move over Lakes Erie and
Ontario and create lake effect snow possibly into wrn Steuben
County, and likely along and north of the NY Thruway. High
temperatures on Tuesday will only reach into the lower to mid
30s. Breezy west winds around 10 to 15 mph will make it feel
like the lower to mid 20s.
A weak high pressure at the surface builds in from the w/sw
Tuesday night as the lake effect snow comes to an end Tue
evening. The cold air will hold on and some raditional cooling
will lead to low temperatures in the upper teens and lower to
A developing low pressure system over the southern Atlantic
coast will be slowly deepening and lifting to the northeast out
to sea on Wednesday. There is still some uncertainty with
respect to the northern extent of the light precip shield. The
latest GFS still wants to hold onto a broad area of light snow
across much of PA and NY. However, much of the other guidance
is now leaning toward a relatively dry and cold Wednesday. At
this time we have decided to just back off on precipitation
chances and still mention a chance of snow. If snow does
eventually develop it should be on the light side. Daytime highs
on Wed will once again range from the upper 20s to lower 30s.
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
250 pm update...
Deep low well off the East Coast will allow for the development
of a ridge axis along the spine of the Appalachians Wednesday
night. This should keep chances for snow to a minimum into Thu
morning. Should be another cold night with lows bottoming out in
the teens and lower 20s. A low amplitude ridge aloft will
arrive on Thursday and re-enforce the surface high moving to
the east and keep weather conditions quiet through the day.
A pattern change appears to be unfolding Thursday night through
Saturday as a deep upper trough looks to dig into the Central
Plains which will induce the amplification of an large upper
ridge over a good portion of the eastern third of the US. An
initial embedded short wave will move quickly across the
Northeast Thu night and Friday and produce a period of rain/snow
mix into Friday morning, before changing to all rain Friday
afternoon. Temperatures start out in the 20s and 30s in the
morning and end up in the upper 30s and 40s by the afternoon. As
the ridge continues to amplify Friday night into Saturday
temperatures will start to rise early Saturday morning back into
the mid to upper 40s...and eventually into the lower to mid 50s
by Saturday afternoon. During this time there will likely be
periods of rain showers...but timing, location and intensity is
too difficult to nail down at this time.
.AVIATION /04Z MONDAY THROUGH FRIDAY/...
640 pm update...
VFR conditions are expected at all terminals through at least
06z at all terminals. A strengthening low level jet increases
the Low Level Wind Shear across all of CNY and NEPA with very
strong LLWS developing by 04z. 2k ft winds are around 50 kts
from the south shift to SSW. There is uncertainty in the
surface winds this evening and overnight due to a strong
inversion just above the surface. There is a chance of stronger
wind gusts, especially at ITH and SYR tonight if the inversion
is any weaker than forecasted.
Rain showers will move in around 09z with MVFR cigs. As an
approaching cold front nears cigs fall further to fuel alternate
and IFR just at AVP/BGM. The front brings a wind shift to west
and improved cigs, as well as an end to LLWS.
Surface winds from the east and southeast at 10 kts to start
increase this evening to 15 gusting to 25 kts. Late tonight the
direction shift to south with speeds of 15 to 20 gusting to 25
to 30 kts.
Monday night through Tuesday...Gusty west winds with lake
effect snow showers and resultant intermittent restrictions;
mainly NY terminals Monday night and then KSYR-KRME Tuesday.
Tuesday night through Wednesday evening...Passing system with
snow showers and associated restrictions.
Thursday into Thursday Night...Dry with mainly VFR conditions.
Friday...Restrictions possible with next disturbance bringing
rain and snow showers to the region.
PA...Wind Advisory until 7 PM EST Monday for PAZ038>040.
NY...Wind Advisory until 7 PM EST Monday for NYZ015>018-022>025-036-
Area Forecast Discussion
National Weather Service Birmingham AL
730 PM CST Sun Dec 5 2021
Evening Update and 00Z Aviation.
/Updated at 0641 PM CST Sun Dec 05 2021/
Forecast right on track this evening. Positive MUCAPE values and
upward motion are hanging north and northwest of the area this
evening. The latest model suite continues to hold off convection
until right around sunrise in the northwest near Hamilton. The
showers/storms will then reach the I-59 corridor by noon and the
I-85 corridor by 2-3 pm. It appears that the instability values
are slightly better with the latest runs and may have to adjust
the Marginal Risk farther into central Alabama overnight.
Lower cloud cover will be advertised overnight for a large part of
the area instead of the dense fog we have received the past few
nights. This is mainly due to increased winds in the lower levels
overnight. The one area that may still get the low visibilities
will be southeast locations southeast of a line from Troy to
Previous short-term discussion:
/Updated at 1231 PM CST Sun Dec 05 2021/
It`s a "spring" day in December across Central Alabama, with
temps now rising into the 70s, and in some cases upper 70s across
far southern counties. Convective activity has also developed
close to the stalled and now diffuse frontal boundary draped
across the Tennessee Valley. Storms have already developed early
this afternoon across our northern counties with RAP analysis
indicating between 1000-2000 SBCAPE and 0-6km bulk shear values
between 20 and 30 knots. Low-level moisture values have increased
with dewpoints in the upper 50s to lower 60s. We can expect these
scattered showers and storms to continue through the afternoon,
decreasing in coverage after sunset. As low-level flow increases
overnight tonight the boundary layer should be sufficiently mixed
to prevent widespread fog formation, or at the very least much
less fog than we`ve seen the past few days. The best chance for
fog will be across the far southeast, more removed from the
approaching storm system.
Attention will then turn to the arrival of the cold front on
Monday morning and if we`re able to see any development of severe
storms. Following analysis of forecast soundings and model
guidance this afternoon, we`re going to include a Marginal Risk of
severe storms generally along and north/west of a line from Selma
to Clanton to Anniston from 6am to midday on Monday. Marginal
amounts of low-level instability with 0-6km shear between 50-60
knots could give us a chance for isolated damaging wind gusts, and
we can`t rule out a brief tornado embedded within the line of
storms as it moves into our northwest and western counties between
6am and 9am Monday morning. As the line moves farther to the
southeast, overall dynamics and shear weaken considerably, and
southern and southeast counties are not expected to have a severe
weather risk at this time. We certainly can`t rule out some
isolated gusty winds at Auburn, Troy, and Eufaula as instability
increases during the afternoon, but the best severe weather
dynamics will be exiting the area as the line reaches those
locations. We`ll continue to watch the latest observation and
guidance trends through the evening and overnight hours.
/Updated at 0138 PM CST Sun Dec 05 2021/
Tuesday through Saturday.
The long term period remains complicated and challenging with an
active pattern in place across much of the region.
Tuesday through Wednesday.
A longwave trough will be moving east over Ohio River Valley
while a surface cold front will push through the area Monday
night. Expansive surface high pressure across the High and Central
Plains will build southeast into the region. Fast zonal flow will
prevail aloft and will allow a few shortwave disturbances to move
over the area Tuesday into Wednesday. The cold front to our south
looks to stall late Tuesday and lift north as a warm front into
our south- central and southeast counties Wednesday morning while
a surface low develops and moves northeast along the front and
will enter west-central Georgia Wednesday morning. A longwave
trough approach from the northwest during the day Wednesday and
this will support another cold front that will move into our
northwest counties during the day Wednesday.
The result will be lingering showers Tuesday night and Wednesday
with the best chances across the southern portion of the area.
Rain chances will persist into Wednesday with chances for showers
and some thunderstorms across the south and southeast areas that
look to reside in the warm sector. A decreased chance of showers
is forecast Wednesday night as the cold front pushes back to our
southeast. Highs will range from the 50s north to the 60s
southeast with lows ranging from in the 30s northwest to the 50s
southeast. A light freeze northwest is possible Tuesday morning.
Thursday through Friday.
Shortwave ridging should move over the area Wednesday night into
Thursday while a shortwave trough moves east just to our northwest
over the Mid Mississippi River Valley Region. Mid-level ridging
will build further over the area Thursday before a shortwave
trough moves over the area early on Friday. Mid level ridging
becomes firmly established over the Gulf of Mexico with amplified
ridging over the area Friday night into Saturday.
The result will be a quick end to the cool down we see behind the
first cold front as a strong warm advection develops during the
day Thursday in concert with the mid and upper level height rises
supporting above-normal temperatures as we progress through late
week and into the upcoming weekend. An unsettled pattern will
emerge with the warmer and more moist airmass in the lower levels
with the upper disturbance moving east just to the north of the
area. Initially, chance for rain and some storms will be highest
south in the more warm and unstable low-level airmass, but we will
see isolated shower and some thunderstorm chances as we go from
Thursday into Friday. I capped PoPs during this time frame in the
40 percent range to account for uncertainty regarding timing and
location of expected convective development. We will experience
quite a warming trend with highs ranging from the 60s areawide
Thursday to readings ranging from the upper 60s northeast to the
mid 70s southwest on Friday. Lows will dramatically moderate with
readings from the low 30s northeast to mid 40s south on Thursday
followed by readings in the mid 40s east and northeast to values
in the upper 50s southeast on Friday.
A deep, potent longwave trough will approach the region from the
west late Saturday. This dynamic system will move over an unstable
environment with unseasonably warm temperatures with deep-low
level moisture forecast across the area. We will be closely
monitoring model trends over the next few days as we begin to
enter the range of the shorter-range higher resolution models.
There remains notable differences among the currently available
global guidance regarding the placement of features and mid-level
trough orientations/tilting. We can say at this time the period of
time looks stormy to say the least with potential for multiple
hazards from severe storms to heavy rainfall. Lows will range from
the upper 50s northeast to the mid 60s southwest while high
temperatures will range from the low 70s north and northeast to
readings in the upper 70s south. Heaviest activity is progged
across the northern half of the forecast area but to account for
the range and uncertainty, PoPs were capped in the 50-60 percent
00Z TAF Discussion.
All terminals start the period with VFR conditions, but this good
flying weather will quickly gain some restrictions overnight. Low
level winds increase overnight out of the southwest and near
35kts. This will be below LLWS criteria, but will allow strong
isentropic lift on the 290K surface and expect widespread IFR/LIFR
ceilings after 06z. Due to slightly increased surface winds, only
hit the fog at TOI near sunrise. A cold front moves through the
area on Monday with showers and a few storms accompanying it.
Winds will be southerly around 10kts ahead of the front and swing
around to the northwest and north behind the front 10-20kts. May
have to bump winds up slightly Monday afternoon. The winds should
start shifting after 18z north and after 21z south. Ceilings and
vis improve to MVFR by 15z outside rain areas and hold through the
Note: AMD NOT SKED is appended at KBHM due to ASOS power loss until
Low clouds and fog may develop overnight, especially across
portions of the south and southeast counties and persist into
early Monday morning. Low-level moisture content will continue to
increase as a cold front approaches from the northwest with
widespread rain chances on Monday along with a few thunderstorms.
RH values are expected to remain somewhat elevated into next week
as a period of unsettled weather could continue to bring periodic
rain chances for the next several days.
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 58 66 35 53 40 / 20 90 20 30 40
Anniston 60 69 39 56 45 / 10 90 20 40 40
Birmingham 61 67 39 53 44 / 10 90 20 30 40
Tuscaloosa 63 67 40 53 43 / 10 90 20 30 40
Calera 62 68 41 56 45 / 10 90 30 40 40
Auburn 57 70 45 57 50 / 0 80 40 50 60
Montgomery 60 75 47 61 50 / 0 80 40 50 60
Troy 59 75 51 63 52 / 0 80 50 50 60
Area Forecast Discussion
National Weather Service Boston/Norton MA
1052 PM EST Sun Dec 5 2021
High pressure moves offshore tonight. A warm front lifts north
across southern New England Monday morning with a period of
showers and isolated thunderstorms possible along with
unseasonably mild conditions. A strong cold front sweeps across
the region Monday evening which will be accompanied by another
period of showers and strong winds Monday afternoon and evening.
Dry and cooler than seasonable air works into the region late
Monday night and Tuesday. A coastal storm may bring some
accumulating snowfall across southern New England Wednesday into
Wednesday night, but there is considerable uncertainty. Dry
weather returns on Thursday before we become more unsettled late
in the week and heading into the weekend with warmer
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Minor tweaks to the forecast this evening. Tried to update
precipitation timing. Thought there was good agreement amongst
the near term guidance, especially the HRRR, RAP and 3 km NAM.
Used a consensus approach as the basis for changes. Still
looking complicated for early Monday morning. Lots of helicity
is still projected, but not much instability to tap into it.
Will need to monitor any convection early Monday morning. If it
gets strong enough, it could develop some rotation.
Brought temperatures and dew points in line with observed
trends. Still thinking there is a really low risk for some light
icing along and north of Route 2 late tonight. Based on latest
guidance, this window should only last for 1-2 hours. Still do
not have enough confidence for any headlines at this time. It
may be a last minute thing. Yet another aspect of the forecast
to monitor closely overnight.
645 PM Update...
No changes in the latest update other than making minor
adjustments to cloud cover to move more in line with current
obs. Rest of forecast is unchanged.
High pres moves offshore tonight as potent mid level trough and
shortwave moves across the Gt Lakes. A lead shortwave within the SW
flow aloft and attendant surface low lifts north along the mid Atlc
coast overnight. CAMs all show convective showers developing over
the ocean overnight within an area of marginal elevated instability.
These showers will move up along the south coast into portions of
CT, RI and SE MA toward daybreak. Meanwhile, some spotty light
precip may develop late tonight across western MA. Temps tonight
will drop to near freezing or a bit below in the interior before
slowly rising late tonight. If precip develops early enough, there
is a low risk for isolated light freezing rain across portions
interior northern MA along route 2 corridor to the east slopes of
the Berkshires. However, this risk is quite low and areal
coverage would be very limited. The more likely scenario is that
temps will be a bit above freezing when precip moves in. Will
have to closely monitor this overnight. Otherwise, temps will be
rising through the 40s near the coast as SE winds increase.
.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Convective showers lift north across SNE during the morning as warm
front moves northward. There is marginal elevated instability with
HREF indicating MUCAPE of 200-500 J/kg across eastern New Eng so
can`t rule out an isolated t-storm across eastern CT, RI and eastern
MA during the morning. While, low level shear values are impressive
soundings show a rather pronounced low level inversion in the
morning which would preclude any stronger convective winds from
mixing down to the ground.
Warm sector airmass overspreads SNE in the afternoon with temps
soaring into the mid 50s higher terrain to lower 60s coastal plain.
Expect a period of dry conditions late morning into the afternoon
before deeper moisture moves in from the west as strong cold front
approaches. A band of showers expected to move into western MA/CT
late in the day.
Strong winds are other concern for Monday afternoon and evening as
60+ kt low level jet develops across SE New Eng. Given SW flow,
mixing will be deeper than what we normally see with a S or SE wind.
Forecast soundings show potential for a period of 40-50 mph gusts
across SE New Eng late Mon into Mon evening. As a result we issued a
wind advisory for Cape/Islands into SE coastal MA and Newport county
in RI. Elsewhere, gusts 30-40 mph are possible.
Cold front moves across SNE during the evening and will be
accompanied by a period of widespread showers which move off
the coast just after midnight. Turning colder with partial
clearing developing overnight with lows upper 20s to mid 30s.
The rain may end as a brief period of snow over the higher
Strong pre-frontal SW winds in the evening, gusts 25-40 mph
except 40-50 mph SE New Eng coast where wind advisory
continues. Post- frontal W winds will be less but it will still
be blustery overnight.
.LONG TERM /TUESDAY THROUGH SUNDAY/...
* Drier with near to cooler than seasonable temperatures on Tuesday.
* Potential for accumulating snowfall late Wednesday into Wednesday
night. However, it is still too early to hone in on specific
amounts and the exact details as there is considerable uncertainty
in the track/intensity of the low passing by. Travelers will want
to stay tuned to future updates.
* Drier on Thursday as a weak high builds in. Unsettled late in the
week and heading into the weekend. May start off as snow before it
transitions to rain. Seasonable readings on Thursday before we
trend warmer than normal on Saturday.
Tuesday and Tuesday night...
Cyclonic flow in place across much of the US. Fairly weak mid level
ridge builds from the eastern Great Lakes/Quebec into northern New
England/eastern Canada. A trough digs into the Mid/Upper Mississippi
River Valley late on Tuesday. A the surface weak high builds into
the region from Quebec/eastern Great Lakes. The high shifts into
eastern Canada by late Tuesday night.
Dry and quiet weather anticipated across southern New England. Will
start off a bit blustery due to a tightened pressure gradient, but
will relax as the high gradually builds in. Did bump up high temps
slightly due to W/WNW flow aloft at 925 hPa resulting in some
downsloping. Went with the 75th percentile of guidance, which is
roughly seasonable readings for this time of year, but will be much
cooler in comparison to Monday. Highs in the mid/upper 30s across
the higher terrain and the low/mid 40s elsewhere.
Will see increasing mid/high cloud cover late on Tuesday and
especially Tuesday night ahead of the next incoming system. Should
remain dry with high pressure still in control, so dialed back the
default NBM precipitation chances based on the latest guidance.
Think that we will remain dry until a bit later in the day
Wednesday. Given the cloud cover will be tough for temps to really
plummet, but given the highs position could have some cold air
drainage due to a northerly ageostrophic wind component. Low temps
in the 20s for most except along the immediate coastline where
readings are around 30.
Wednesday into early Thursday...
Lots of uncertainty during this timeframe there is potential for
widespread accumulating snowfall, but really too early to tell given
the spread amongst guidance. A positively tilted trough will be
situated over the Mid/Upper Mississippi River Valley will dig into
the central Great Lakes/Ohio Valley and become neutrally tilted
during the afternoon. The trough then lifts into the Mid Atlantic
becoming negatively tilted by the evening and through New England by
early Thursday. At the surface, low pressure will develop offshore
from the VA/NC coast and lift northeastward south of southern New
England late on Wednesday. The low lifts offshore to the
east/southeast of southern New England by late Wednesday/early
Still have considerable uncertainty in this timeframe with respect
to QPF/snowfall amounts and anticipated impacts. The reason for the
uncertainty is due to both the intensity and track of the surface
low. Lots of spread amongst guidance with the current trend being
the system being weaker and staying further offshore to the S/SE. No
point in getting into the specific details at this point as we still
need to really hone in on the track of the surface low to determine
the impacts. The GFS right now features more of a snow lovers track
passing just to the SE of the benchmark, whereas the ECMWF/GEM/NAM
give us not much of anything. Within this window have honed in more
on the EPS/GEFS ensemble guidance, which also have been showing
trend of the low staying further offshore at this point in time.
There are 5/30 GEFS members indicating there could be warning level
snowfall accumulation assuming a 10-1 SLR. Whereas 14/30 show not
much if any snowfall accumulation. The EPS features no members
showing warning level accumulations with the 10-1 SLR and the vast
majority showing not much if any accumulations. Both EPS/GEFS
members have been trending in the wrong direction for snow lovers
with probabilities of amounts AOA 1 or 3 inches. Given the
uncertainty have stuck with the NBM guidance at this point in time
and nudged down WPC precip slightly. Given we are still talking 4-
4.5 days out will need to see if this trend continues and get better
consensus amongst guidance. If folks have travel plans they will
want to stay tuned to future updates. Appears at this time given the
progressive nature of the system that if there were impacts to
travel it would be more for the late afternoon/evening commute.
Given the progressive nature of the system precip should be over
with before daybreak.
High temperatures on Wednesday will be cooler than seasonable with
readings generally in the 30s, but the Cape/Islands could see
readings in the low 40s. Low temperatures heading into Thursday
morning would be fairly widespread 20s with low 30s across the
Weak high builds over southern New England in wake of the exiting
system. Will have cool NW/N flow aloft, which advects colder air
into the region. High temps will be below normal for this time of
year with fairly widespread 30 degree readings.
Some uncertainty with respect to the temps heading into Friday
morning. Models spread out on how strong a warm air advection we get
ahead of the next trough lifting in. Have stuck with NBM, but not
out of the question we are too cold at the moment give some models
925 hPa temps. Right now lows in the 20s across the interior and low
30s for the Cape/Islands.
Friday and Saturday...
Given the uncertainty earlier in the forecast, have not put much
emphasis this far out. Does appear that we have shortwaves/troughs
lifting into the region. This could bring us some light
snow/flurries heading into Friday. Does appear at the moment that
based on temp profiles would see precip change over to rain for
Friday and also for Saturday. Should be much warmer than normal
during this timeframe with pretty good consensus in a warm up. High
temps on Friday in the 40s with some low 50s along the south coast.
For Saturday, right now have widespread highs in the 50s.
.AVIATION /04Z MONDAY THROUGH FRIDAY/...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight...High confidence in trends, but moderate in specific
VFR to start with conditions gradually deteriorating to MVFR/IFR
around 08-12Z as ceilings lower. Will see scattered showers
moving in during this timeframe as well. Coverage still expected
to be the greatest near the south coast. Have also added a VCTS
mention to the Cape Cod/Island terminals as think this is where
the risk is highest heading into the AM push. Low risk for
isolated freezing rain in northern MA along route 2 corridor to
the east slopes of the Berkshires. Increasing SE wind
Cape/Islands late tonight. Not out of the question there may be
some 20-25 kt gusts, but have added LLWS mention per RAP BUFKIT
soundings until mixing appears more likely within the boundary
Mix of MVFR/IFR conditions. Showers lifting north across SNE in
the morning with isolated thunder possible in RI and eastern
MA. Have added the thunder mention to Cape/Islands terminals,
but may be needed for PVD/BED/BOS. Have held off on PVD/BED/BOS
for now as confidence is lower in how widespread the coverage
will be. A period of dry weather in the afternoon with another
round of showers moving into western MA late in the day.
Increasing S/SW winds with gusts 25-35 kt developing, strongest
SE New Eng. Areas of LLWS in the afternoon across Cape/Islands.
Monday night...Moderate confidence.
MVFR with areas of IFR as showers move across the region during
the evening, then improving to VFR from west to east. Showers
may end as snow showers over the higher terrain. A period of SW
gusts to 40 kt possible in the evening over Cape/Islands and
adjacent SE MA, with 25-35 kt gusts elsewhere, diminishing
KBOS TAF...High confidence in trends. Moderate confidence in
timing and exact details. Not out of question there is a
thunderstorm or two roughly in the 11-15Z window, but confidence
too low to add in the TAF at the moment.
KBDL TAF...High confidence in trends. Moderate confidence in
timing and exact details.
Outlook /Tuesday through Friday/...
Tuesday: VFR. Breezy.
Tuesday Night: VFR.
Wednesday: Mainly VFR, with local IFR possible. Chance SN, RA
Wednesday Night: Mainly VFR, with areas MVFR possible. Breezy.
Thursday: VFR. Breezy.
Thursday Night: VFR. Chance SN.
Friday: Mainly VFR, with areas MVFR possible. Chance SN, slight
Forecaster Confidence Levels.
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Increasing SE winds later tonight then a period of SW gusts to 35-
40+ kt developing in the afternoon/evening as 60 kt low level jet
develops. Gale warnings continue on all waters. Winds shift to W Mon
night behind the cold front with gusts gradually diminishing to 25-
35 kt. Scattered showers with an isolated t-storm possible late
tonight and Mon morning, then another period of showers Mon night,
Outlook /Tuesday through Friday/...
Tuesday: Low risk for Small Craft Advisory winds with local
gusts up to 30 kt. Areas of rough seas.
Tuesday Night: Winds less than 25 kt. Areas of seas approaching
Wednesday: Winds less than 25 kt. Seas locally approaching
5 ft. Rain likely.
Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. Rain likely, chance of
Thursday: Winds less than 25 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. Areas of rough seas. Chance of
The following are the astronomical heights of upcoming high
tides and do not include surge values from local wind/weather
Boston12.0 feet - 1214 PM Monday
Nantucket4.4 feet - 120 PM Monday
Providence 5.8 feet - 917 AM Monday
Given southerly winds, not expecting much surge on the east
coast with tidal anomalies less than 0.5 ft. Worst case along
the east coast is minor splash over for most vulnerable
Along the south coast, a surge of 0.5-1 ft is possible but this
will likely occur after the high tide so not expecting any
impact on the south coast for the Monday morning high tide.
MA...Wind Advisory from 1 PM Monday to 1 AM EST Tuesday for
RI...Wind Advisory from 1 PM Monday to 1 AM EST Tuesday for RIZ007-
MARINE...Gale Warning from 10 AM Monday to 7 AM EST Tuesday for
Gale Warning from 10 AM Monday to 1 AM EST Tuesday for ANZ230-
Area Forecast Discussion
National Weather Service Grand Forks ND
955 PM CST Sun Dec 5 2021
Issued at 945 PM CST Sun Dec 5 2021
Lengthened the blizzard warning to 3am with gusts up to 40mph
expected to persist per HRRRTL and also added Wilkin and Richland
county to the warning per conditions and webcams. Went with the
wind chill advisory in the Devils Lake basin ending the warning as
winds and visibility have improved there. Temps continue to
plunge with near zero in the north now and teens in the south.
These colder conditions really help snow flakes fragment and loft
more easily reducing visibilities.
UPDATE Issued at 622 PM CST Sun Dec 5 2021
Upgraded to blizzard warning with white out conditions reported
and seen on webcams across the northern valley behind the cold
front which is dropping temperatures a quick 10 degrees into the
teens. These lower temps along with the northerly wind gusts of 40
to 50 mph measured will continue blow the snow more easily than
the temps in the 20s we saw earlier today. Conditions are
obviously much worse in open country than they are in town or
within shelterbelts. HRRR maintains winds through about midnight
and then lessening.
.SHORT TERM...(This evening through Monday night)
Issued at 256 PM CST Sun Dec 5 2021
Low pressure at 20z east of Fargo and just southwest of Detroit
Lakes moving east. Upper low just east of Grand Forks. There will
continue to be light snow around the upper low as it moves east
with light snow ending in RRV by mid evening and in the far east
after midnight. Seeing winds turning north in the RRV and E ND at
mid aftn with gusts into the 25-30 kt range.
Question remains blizzard potential. Blowing snow model has 60
percent chance of vsbys to 1/2SM in the mid RRV 00z-04z. Max winds
low level reach 40 kts for mixing per soundings but as 930 mb and
below cool there remains a steep inversion and warm layer up thru
850 mb this evening and the 850 mb layer doesnt cool until
overnight. But by then the mixed layer winds are not as strong. So
if there is a time when the colder air first comes in and low
level winds are 40 kts is when blizzard conditions are most likely
and this would look to be 04-05z. So a 1-3 hour period of
widespread vsbys 1/4sm or less seem at least possible (50 percent
chance). At the time of this snow is not expected to be falling.
However will need to watch arctic front as some light snow is
progged with it into central ND and there is light snow upstream
near Brandon and thru SW Manitoba.
Net result of all this is the office consensus to continue winter
storm warning. Main snow is done, but impacts from still falling
snow combined with wind warrants keeping warning thru valid time
of 06z. If conditions are worse and more widespread, then
blizzard warnings can be issued (40 percent chance of that
Very cold overnight and wind chills drop into the -25 to -35F
range by 09z-14z in NE ND, nrn RRV. Wind chill advisories likely
needed but will hold until this storm event is done.
Cold day Monday with highs single digits above.
.LONG TERM...(Tuesday through Sunday)
Issued at 256 PM CST Sun Dec 5 2021
.LONG TERM...(Tuesday through Saturday)
Aside from a chance for light snow in the north on Thursday and in
the south on Friday, impactful weather is not anticipated throughout
the remainder of the long term period. Otherwise, a gradual warming
trend will be the story for the week ahead into next weekend.
Synoptically, northwesterly flow aloft looks to continue through
midweek. At the surface, this flow pattern will be accompanied by
generally quiet weather and a gradual warming trend. While Tuesday
is expected to remain cold with highs in the teens, with southerly
return flow inching into the region, warmer, near normal,
temperatures are anticipated moving into Wednesday. A quick moving
shortwave and its attendant cold front may introduce a glancing blow
of light snow to portions of the northern forecast area on Thursday.
Ensemble guidance is in varied agreement on this solution and as a
result, we are looking at a roughly 20-30% chance for some light
snow with this system. Following this system, ensemble guidance is
picking up on an upper trough that looks to traverse the central
Plains. While main impacts should remain to the south of the
forecast area, some light snow impacts cannot be ruled out for those
south of the I-94 corridor on Friday. However, confidence in the
exact track of this trough and its precipitation impacts is low at
this time. As the main upper trough exits the region, zonal flow
looks to take its place. This will lead to yet another quiet pattern
with varying degrees of gradual warming moving into the weekend.
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 622 PM CST Sun Dec 5 2021
Winter storm creating IFR or MVFR conditions across the area
tonight with north winds gusting over 40kts in the valley. Will
see conditions improve overnight into Monday morning. VFR expected
ND...Winter Weather Advisory until 3 AM CST Monday for NDZ038-049-052.
Blizzard Warning until 3 AM CST Monday for NDZ007-008-016-027-
Wind Chill Advisory until 10 AM CST Monday for NDZ006-014-015-
MN...Winter Weather Advisory until 3 AM CST Monday for MNZ030-031-040.
Winter Storm Warning until 3 AM CST Monday for MNZ005-006-008-
Blizzard Warning until 3 AM CST Monday for MNZ001>004-007-029.
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1105 PM EST Sun Dec 5 2021
Issued at 1105 PM EST SUN DEC 5 2021
The first of the convection is entering the JKL CWA - targeting
our northwest counties initially with the steadier rains and some
embedded thunderstorms. Some training of the cells will be a
concern in this area as well despite the dry conditions out there.
Have updated the forecast to beef up the PoPs and thunder chances.
The current obs and trends for the T/Td were also included with
the update. In addition, a fresh set of zones and SAFs were
UPDATE Issued at 755 PM EST SUN DEC 5 2021
00Z sfc analysis shows high pressure slipping out of the area to
the southeast ahead of an approaching cold front. The fairly tight
pressure gradient between these two features is supporting breezy
south to southwest winds throughout the area - at 10 to 15 mph
with some occasional gusts to 25 mph or higher around. These winds
are keeping the boundary layer well mixed with temperatures
mainly in the upper 50s to lower 60s while dewpoints are running
in the upper 40s to lower 50s. The front is pushing some broken
showers and even a few thunderstorms out ahead of it - in the
south - the strongest storms are mainly affecting locations
well southwest of the JKL CWA - but will need to be watched. The
forecast is on track with the approaching front and convection
arriving into the CWA later tonight. Accordingly, have mainly
updated the grids to incorporate the latest obs and trends for
the T/Td ones. The sky cover and PoPs were also adjusted into the
night per the current conditions and latest consensus CAMs
guidance. These updates have been sent to the NDFD and web
.SHORT TERM...(This evening through Monday night)
Issued at 455 PM EST SUN DEC 5 2021
Late this afternoon, an upper level ridge was centered southeast
of Bermuda with another upper level ridge centered over portions
of the eastern Pacific and extended into the western Conus.
Meanwhile, a broad trough extended from central and eastern
Canada south into the central Conus. A shortwave trough was
moving across the southern Appalachian/northeast GA western SC
area while another shortwave trough was working from OK into AR.
Further north a much more significant upper level low was
centered in the vicinity of far western Ontario/north central MN
with an associated shortwave trough south into the northern to
central Plains regions. Further upstream, another shortwave trough
digging southeast extended from the Hudson Bay region southwest
across Manitoba an into Saskatchewan. At the sfc, high pressure
was centered over the northeast Conus while a stationary boundary
extended west across southern NC, before turning north and
becoming a warm front and crossing the crest of the Appalachians
to the Big Sandy region and then turning west near the OH River
and then west northwest to a triple point sfc low pressure in the
MS Valley while the parent sfc low was centered over MN. Warm air
advection behind the north and northeastward lifting warm front
and in advance of the area of low pressure to the west and
northwest, combined with the recent dryness and downslope
southerly to southeast component to the flow, has led to breaks in
the low level clouds and very mild temperatures for early
December. Temperatures outside of the highest elevations ranged
through the 60s as of 4 PM.
This evening and tonight, the shortwave trough is expected to pass
south and east of the area, while the shortwave southwest of the
region in the OK/AR is expected to track toward the OH and TN
Valley regions. This system will begin to interact with the upper
level low that is expected to weaken to an open wave and track
into the Great Lakes and the associated shortwave trough
approaching the MS River and lower OH Valley. This upper level
shortwave trough will continue east during the day on Monday and
cross the OH Valley region as well as the Commonwealth and rotate
into and across the Northeast and into Canada through Monday
night as an upper level low closes off over Quebec. This will
result in a broad trough extending from Canada into portions of
the Central to eastern Conus as the end of the period.
Meanwhile, at the sfc, the warm front will continue lifting north
and east of eastern KY this evening as the main sfc low tracks
into the western Great Lakes. This sfc low will continue into the
northern Great Lakes late tonight with the trailing cold front
moving across western and into central portions of the Commonwealth
through dawn on Sunday. This sfc low will track into Quebec
through late Monday and into the Maritimes through the end of the
period. Sfc high pressure will build east from the Plains and MS
Valley region and into the OH Valley behind the front to end the
The pressure gradient across the region will increase this evening
and into tonight ahead of the approaching front and lead to 850 mb
winds in the 45 to 55KT range or so late tonight through early
Monday. This will lead to increased shear as well as the potential
to transfer some of this momentum to the sfc at least at times in
some locations in advance of the front itself and an anticipated
convective line. Instability will be limited from late this
evening into the overnight hours, but some thunder cannot be ruled
out in this low end CAPE somewhat high shear environment. SPC has
highlighted areas of the western edge of the CWA in a Marginal
risk for severe thunderstorms, where moisture and instability
should be greatest combined with a bit greater shear. Given the
strength of the LLJ and forcing from the approaching shortwave
trough, thunder cannot be ruled out over the entire area late
tonight, though chances appear best across the western half of
the area prior to dawn. There is a bit of uncertainty as to just
how quickly the convective line will move east as well with some
run to run and model to model variability among the CAMS. The HRRR
also has at times had a tendency to move the line a bit too
slowly downstream. Given all of this, thunder chances were
included as far east as all of Pike County late.
The front and any remaining convective line should continue east
and southeast during the first couple hours after sunrise on
Monday with some needed showers continuing for a few hours behind
the front. Drier air will begin to move into the region by midday
into the afternoon with chances for precipitation near the VA
border ending around or just after sunset on Monday evening.
High pressure building in will lead to clearing skies on Monday
afternoon to Monday evening with mainly just passing high clouds
on Monday night. This will set the stage for seasonably colder
temperatures on Monday night compared to the mild lows will
Moisture and forcing appears best across the northwest half of
the area and average QPF greatest there, nearing on inch if not
more, while, areas further southeast with the downslope component
to overcome should average in the 0.4 to 0.8 tenths range.
.LONG TERM...(Tuesday through Sunday)
Issued at 511 PM EST SUN DEC 5 2021
We start the extended in the middle of a very brief break
from any precipitation Tuesday, but an active pattern quickly
resumes as we head further into the middle of the week. The upper
level pattern Tuesday mainly consists of broad troughing across much
of the CONUS, with a few shortwaves embedded within the flow. Of
particular interest to our area, is one shortwave coming up from the
Southern Plains through the Lower Mississippi Valley, as well as a
northern stream wave coming down from the Northern Plains, and the
potential interaction between the two and how that effects the
details of a developing surface low. Though the overall pattern is
fairly well agreed upon, the differences that do exist over the
smaller details are contributing to continuing uncertainty around
the specifics of potential impacts felt by our area. Guidance has
trended towards a more suppressed system that stays further to our
south, leading to colder temps and less precip falling in our area
Tuesday night and Wednesday. The cooler trend has increased
confidence in at least some of this precip falling as snow for
portions of our area Tuesday night. However, the uncertainty in the
finer details, such as the low intensity and exact track, lends to
less confidence in precip amounts and the location of where rain
ends up transitioning to snow. While the exact amounts are still
subject to further refinement, generally expect that light
accumulations are possible. Temperatures at the beginning of the
period average normal, with highs Tuesday and Wednesday in the upper
30s to low 40s, and lows in the mid 20s to around 30.
We see a breif dry period Wednesday night through most of Thursday
as modest ridging passes aloft. Rain chances return late Thursday
into Friday as more shortwave energy approaches the region, though
exact timing is still yet to be completely worked out. Things turn
potentially more active over the weekend as a sharper trough
supports a more potent system that pushes a strong cold front
through the region. With abundant moisture being brought in ahead of
the front (PWATS more that 2 standard deviations above
climatological norms), there exists the potential for some within
the region to see some heavier rain with this front. Recent forecast
soundings also show at least limited instability and plenty of shear.
However this system is still far out in the forecast period, and
specifics can change as finer details like timing and intensity
become better resolved with time, but trends will continue to be
monitored. Under increasing southerly to southwesterly flow,
temperatures Thursday and beyond see a warming trend, ending up well
above normal by the weekend, before potentially dropping for the end
of the weekend.
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 710 PM EST SUN DEC 5 2021
Aside from some upper end MVFR ceilings at LOZ - VFR prevailed
throughout the CWA at the start of the period. VFR conditions are
expected to be the rule through around 06Z for most places. By
that point though, moisture, as well as increasing and lowering
clouds and some convection, will move into eastern Kentucky in
advance of a well defined cold front. This front will bring
showers and perhaps a brief convective line at the boundary along
with potential for some thunder. This is most probable during the
09 to 14Z timeframe as the front progresses through the forecast
area. An eventual deterioration to MVFR ceilings will follow with
this - possibly some MVFR VIS along with brief IFR conditions
accompanying the convection right along front, too. Locations
south and east of JKL may remain VFR until around 12Z due to a
downslope component to the flow.
South winds averaging 10 kts will continue through the evening
and increase into the 10 to 15 kt range from west to east between
02 and 07Z. As the front passes, between about 11 and 16Z, look
for the winds to become more westerly. A few gusts into the 20 to
30 kt range, at least at times, appear probable during the 02 to
15Z timeframe as the front approaches and crosses the area. In
addition, winds off the surface will become much stronger this
evening, with some low level wind shear likely transitioning from
west to east between 02 and 14Z.
Area Forecast Discussion
National Weather Service Lake Charles LA
858 PM CST Sun Dec 5 2021
Some low-level clouds are currently moving through the area this
evening. Winds are expected to be higher tonight which should keep
the chances for fog formation low. However, some patchy fog will
be possible. Therefore, patchy fog was added to the forecast for
the overnight hours into the morning as the front starts to
approach the area.
Precipitation chances in the forecast appear to be on track so
far, with the 00Z HRRR showing the bulk of the precipitation
starting to enter the area in the morning hours. Precipitation
chances will continue through the day. Showers and thunderstorms
will be expected. SPC has our area in a Marginal Risk of severe
weather as the front makes it way through the area.
.PREV DISCUSSION... /issued 528 PM CST Sun Dec 5 2021/
For the 06/00Z TAF Issuance.
Tighter pressure gradient between low pressure over the Plains and
high pressure off to the east will allow for stronger southerly
flow in the boundary layer. Thus, restrictions from fog is not
anticipated as it was the past few nights. Instead low clouds with
MVFR to IFR ceilings with developing showers will be the issue
On Monday, a cold front will move across the forecast area with
showers and thunderstorms developing ahead of it. In general, MVFR
conditions are expected during the day. However, worse conditions
will be possible if any of the stronger convection passes over a
PREV DISCUSSION... /issued 404 PM CST Sun Dec 5 2021/
SHORT TERM [Rest of today through Tuesday Night]...
Tonight going into tomorrow will be the highlight of this forecast
as a cold front slides into our CWA.
While the PW from this mornings sounding was not as high as
yesterday, its still close to the 75th percentile. In addition to
that, PWs ahead of the front range from 1.4 to 1.8, to which the
lower end of that range is at the 90th percentile. 24H QPF totals
will be around a half of an inch to two inches, with higher
amounts possible. Despite the fact that we have been on the dry
side as of recent, flash flooding is not out of the realm of
We remain in SPCs marginal risk for severe thunderstorms which
was expanded to cover the entire CWA. The main threat will be
damaging wind gusts however hail and isolated tornadoes cannot be
ruled out. Instability is not all that impressive but there is
sufficient low and deep layer shear to support modest updraft
With this front moving thru over the Monday, temperatures will be
similar to what we are experiencing today. Monday night will be
nearly 15 to 20 degrees cooler with temps in the 40s to lower 50s.
Tuesday will be cooler with temps struggling to make it into the
mid 60s at the most with overcast skies and scattered chances of
showers and storms.
LONG TERM [Wednesday through Sunday]...
A near zonal flow will develop aloft in wake of Tuesday`s departing
shortwave...however some lingering convection should be continuing
over lower Acadiana at the beginning of the day on Wednesday where
better lift/moisture will be last to depart as well as its
proximity to the old frontal boundary meandering over the nrn Gulf.
The boundary is progged to begin lifting back nwd as a warm front
on Thursday, with srly flow ushering in a moderation of temps as
well as the potential for a few showers as another weak impulse
crosses the region.
Increasing srly flow through the column will allow deeper moisture
to pool over the forecast area on Friday...however building
heights/warmer air aloft will effectively cap the atmosphere,
keeping rain chances fairly slim through the day. Temps are progged
to warm to around 80, with lower 80s possible in places...15-20
degrees above seasonal norms and approaching records for the date.
The weekend shows the approach/passage of a more significant
shortwave aloft and an associated sfc front which will provide the
basis for additional convection/higher rain chances. Forecast
soundings are showing some potential for severe weather around the
time of the frontal passage...this will be monitored in the days
ahead. Precip should be ending from west to east by the end of the
Onshore flow will begin to tick upwards this afternoon and
continue a steady trend upwards tonight before weakening. Rain
chances will begin in earnest Monday morning and ratchet up
during the day as a cold front approaches in the late afternoon
and evening. The front will stall Tuesday morning and meander
about over the waters before washing early Thursday morning.
Winds and seas will remain elevated during this first half of
.PRELIMINARY POINT TEMPS/POPS...
AEX 62 71 43 57 / 50 100 20 20
LCH 65 75 48 61 / 40 100 40 30
LFT 65 78 51 64 / 30 90 40 40
BPT 65 76 49 63 / 40 90 30 20
GM...Small Craft Exercise Caution through Monday morning for GMZ450-
Area Forecast Discussion
National Weather Service New Orleans LA
554 PM CST Sun Dec 5 2021
.AVIATION...Valid through 06z Tuesday...
Challenging forecast with this TAF cycle. First challenge is
determining extent of fog and low cigs tonight into Monday
morning. Still ample low level moisture in place, but low level
winds will be a bit stronger than the last few nights. That being
said, would only take a brief period of very light to calm winds
for vis and cig to drop like a rock. Have gone ahead and kept
LIFR/VLIFR conditions to TEMPO groups near daybreak for this
issuance. Once any fog dissipates, the next challenge is timing
the frontal passage. Have generally gone with a consensus of the
short range guidance as the CAMs are in fairly good agreement
within a couple hours of each other for timing. Squall line should
affect northwestern terminals around midday and progress
southeastward through the afternoon. As the squall like progresses
southeastward, expect it to lose some of its push, so gust
potential at the southeastern terminals is a bit lower than the
northwestern terminals. With the front expected to stall near the
coast, scattered showers could remain in the area even after 00z
.PREV DISCUSSION... /issued 356 PM CST Sun Dec 5 2021/
SHORT TERM (This evening through Tuesday Night)...
Starting off with late this afternoon/early evening, overall is
looking rather pleasant with only some patchy low-level cu or
stratocu areawide bringing partly to mostly cloudy skies. Current
state of the atmosphere reveals steady and persistent onshore
moist return flow in progress with subtle veering low-level/near
surface winds. We will continue to see low-level flow slowly
increase throughout the night tonight in response to a
strengthening low-level jet/attendant tightening height gradient
to nearby or just to our northwest. This is in association with a
deepening positive-tilt shortwave trough axis and attendant
surface low/cold front diving east and southeast into the Great
Lakes/MS valley region overnight tonight that we will talk more
about shortly. But meanwhile here, the first item to focus on will
be the potential for fog once again later tonight and into early
Monday. There are subtle environmental differences, including a
slight increase in low-level winds mentioned before that could
throw a wrench in either the expected coverage and/or density
owing to a lower-confidence forecast. Combing through a large
suite of model guidance this afternoon shows a bit of a spread,
but enough to build a consensus especially after closely analyzing
select short-range model soundings. The previous mornings fog
processes have generally been a mixed/conglomerate
radiative/advection process, with developmental emphasis moreso
near areas near better moisture sources with air/water temperature
differential (particularly near and within northern portions of
the MS river where the thickest fog has been maintained now for
the past several days). Closely looking at soundings show the
increase in winds roughly from around 150-200m AGL and above, but
with only very little increase below and to the surface. This will
be important as winds are technically forecast to be just a few
MPH higher than the previous mornings, but the question is how
much will this harm the production of widespread, dense fog.
Advertising for now that the potential of widespread dense fog
will be lower than the previous few days, but not entirely out of
the question especially anywhere where winds can shut down enough
to aid in a more radiative fog development process. Otherwise,
guidance also suggests shallow surface fog to maintain or increase
along coastal Terrebonne parish, transporting inland given
favorable wind advection regime. Because of this, will mention
the greater potential for another round of fog for western areas,
or generally along/west of I-55, with less potential east. Due to
a lower confidence forecast, will hold off on any dense fog
highlights for now, and will refer to subsequent forecast shifts
to re-analyze model guidance should the threat increase later this
Any fog around may linger, through mid-morning on Monday, but
should be quick to dissipate as surface winds continue to
increase out of the west/southwest. From here, the next focus as
mentioned earlier will be on an approaching cold front and
associated line of showers and storms entering our NW CWA areas
late AM/early PM. Thumbing through individual HREF members shows
somewhat ok confidence in regards to speed/timing with the main
line, with the spread being around 50 miles or so on average from
the slowest to fastest member. HRRR creeps this line in
northwestern areas around noon as a few members have it in an hour
or two earlier. The Storm Prediction Center does highlight a
large portion of our CWA in a Marginal Risk for severe weather,
highlighting particularly on low TOR and Wind probs. Taking a
closer look at available shear with this line looking at the
synoptic hour HRRR runs, we see a transitioning low-level vertical
wind profile as this line progresses south and east. Early monday
morning, surface winds begin more southerly (or from the SSW)
which aids in a slight bump up in low-level 0-1/0-3 SRH of around
100-200m2/s2. But this is well ahead of the front with the line of
showers then over northern LA/central MS. As the shortwave
trough/attendant surface low continues to eject east into the
Northeast, the aforementioned low-level jet discussed earlier
flattens out and deamplifies with time. Surface winds transition
more out of the southwest to eventual west-southwest which reduces
necessary low- level shear/curvature to support the potential for
rotating updrafts. Meaning, SRH lowers by the time the line
enters out CWA likely becoming cold-pool dominant at some point,
reducing the tornado risk. Having said all of that, storms within
the line will need to be monitored across far northwestern areas,
but the threat will likely diminish as the line sags south into
central areas early afternoon. HRRR Neural Network Convective
Hazard probabilities also illustrate this exact process with
lowering probabilities as the line swings southeast aiding in
confidence in the lowering TOR risk.
Damaging winds may be the only (albeit still low) risk, with the
potential for some sub-severe wind gusts along the line,
particularly for northern and western areas of the CWA. We do see
some very subtle phasing/matching of the weak subtropical jet
lining up with the axis of the deeper shortwave trough axis to
our north, but with max H5 winds in the 45-55kt range. Low-level
winds diminish as mentioned earlier which reduces the threat even
more to around 20-25kt meaning even where downward transfer
occurs, even nearby the strongest updraft, we should only see
generally sub-severe wind gusts in the 35-45mph range, maybe
isolated higher but will remain also a minimal risk. Will just
have to monitor for small bowing segments or for any cells that
could initiate ahead/merge with the line over
southern/southwestern MS and east of I-55 Monday afternoon; but
the threat should diminish thereafter. Should mention the threat
for hail is non-zero, with H5 temperatures in the -12 to -14C
range, but should updrafts ascend high enough to tap into some of
the colder air aloft, could see some isolated small hail
collocated within any stronger storm.
The line steadily diminishes as cold pooling overtakes the
leading updraft ingest down to more of a line of showers across
coastal LA and MS Monday afternoon/evening, with the stratiform
precip shield diminishing with time. We should see the front
settle into the northern Gulf Monday evening, eventually seeing
most precipitation diminishing at that point only with perhaps
some isolated/scattered showers around.
Monday evening/night, a close upper-low over northern Mexico
finally drifts east and weakens/stretches some, but provides
enough downstream divergence coupled with lingering surface
frontogenetic to re-enhance spotty shower coverage, mainly after
midnight Monday night into Tuesday morning. Tuesday offers a bit
of difficulty in the temperature forecast, but with persistent
post-frontal moisture advection leading to mostly cloudy to even
overcast skies, with some (but enough) ongoing low-level to near
surface CAA, have decided to lean on the lower end of the very
wide ensemble spread for MaxT`s. This places many areas just
around 2-3 degrees below deterministic values (upper 50`s
north/60`s south). Be aware that this could be even cooler with
thicker clouds or post-frontal showers, OR could lead in the wrong
direction should CAA relax and/or sunshine find it`s way to the
surface but will target temperatures below guidance for now given
the setup at hand. What is left of the weakening shortwave
impulse pushes east late Tuesday going into Tuesday night, leading
to a drying trend but we may likely be stuck in low-level post-
LONG TERM (Wednesday through Sunday)...
Clouds try to break up going into the daytime on Wednesday, with
a steady return flow setting back up over the northern Gulf coast.
This will lead to a warming trend starting mid-week, going into
the rest of the week ahead. We see a weak/broad trough swing
through Wednesday during the day, which tries to squeeze out some
showers near our area, but better coverage will exist with surface
cyclogenesis/frontogenesis over the mid-Atlantic states. We stay
in this relatively moist environment thereafter as temperatures
continue to build. Kept a warmer bias going on Thursday and
Friday, placing areas into the 80`s and overall pleasant.
Late this week, large-scale ridging remains in control of the
Gulf of Mexico, meanwhile deeper longwave troughing builds into
the intermountan west. Trends with the GFS keeps this large NE to
SW oriented positive tilt axis drifting east into the MS valley
region late Saturday into Sunday, with some sharper curvature at
the base of the trough pulling into the Arklatex region. The GFS
and ECMWF solutions are split on the amplitude/intensity of the
"tip end" shortwave axis which has everything to do with the
potential for severe weather downstream. The ECMWF suggests higher
amplitude troughing to promote enough downstream divergence along
the front to produce surface cyclogenesis, and should this happen
this could help to back surface winds/increase shear ahead of
what could be a quick-moving line of showers/storms. However, the
GFS suggests less overall amplitude with the mid-level trough that
never helps to deepen a surface low leading to less
surface/low level backing in a primarily unidirectional vertical
wind profile, limiting severe weather potential. Overall, many
doubts here but will advertise the next chance of rain with this
front at some point this upcoming weekend, with details including
any severe weather potential forthcoming in the next several days.
Onshore southerly flow will continue to build later this evening
through tonight and during the day on Monday, with exercise
caution headlines in effect later this evening, tonight and
through Monday. Some extension or upgrade to advisory criteria
will be possible, but should remain generally in the 15-20kt
range. The next front will swing through later Monday
afternoon/evening before stalling over the northern Gulf. The
front will return north with onshore flow persisting through the
middle to later parts of the week. Additionally, southerly fetch
increases as surface southerly winds build with increasing wave
heights before the next cold front swings through following into
.PRELIMINARY POINT TEMPS/POPS...
MCB 63 72 46 57 / 20 100 50 40
BTR 63 76 49 61 / 20 100 50 40
ASD 61 78 49 64 / 10 80 50 50
MSY 65 79 56 66 / 10 70 50 50
GPT 62 76 50 61 / 0 70 50 40
PQL 61 76 49 63 / 0 60 50 40
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
922 PM CST Sun Dec 5 2021
Issued at 922 PM CST Sun Dec 5 2021
The forecast remains on track with the main concern being the
strong winds beginning late tonight and through the day on Monday.
Current observations show that most of the CWA has dried behind
a cold front which is sitting along a line from Bloomington, IL to
Valparaiso, IN. Along the front, is a line of lingering showers
which will be departing the area with the front by midnight. While
most of the area will remain precipitation free tonight there is a
chance that the residual lower atmosphere moisture and steepening
low-level lapse rates could generate a few flurries for areas
north of I-80 through daybreak.
Behind the front, winds have veered to the west-northwest and
have started to gust into the lower 20 mph range in a few
locations. Winds will continue to increase in strength overnight
as a tightening pressure gradient and the afore mentioned lapse
rates allow 40 to 45 mph gusts to be transferred to the surface.
These strong winds will persist through Monday afternoon before
they slowly begin to ease from west to east across the CWA.
Temperatures on Monday will be cold with highs struggling to
make it above freezing in the upper 20s and lower 30s. Even colder
temperatures are expected Monday night with lows dipping into the
single digits and lower teens.
Issued at 310 PM CST Sun Dec 5 2021
Through Monday night...
The main concern in the short term is strong winds late tonight
into Monday morning, in which a Wind Advisory has been issued for
locations along and north of the I-80 corridor.
Scattered light rain and drizzle/mist continues to fall this
afternoon within continued warm, moist advection aloft north of
an approaching warm front. These light showers will continue
through early evening before pushing slowly off to the east ahead
of a 1002 mb low pressure lifting northeast over the area. MUCAPE
values of around 100 J/kg as analyzed by the RAP may still result
in a couple thunderstorms in/near the eastern CWA before the
showers depart, and earlier there was some lightning in central
Meanwhile, temperatures will continue to warm through about 8 PM
as a warm frontal boundary inches into the southern CWA this
evening. Seeing that much of the area will remain north of the
boundary, we will see a sharp north-south temperature gradient
this evening with the far southern CWA warming into the lower to
possibly even mid 50s while areas north of I-88 will be stuck in
the upper 30s. As the storm`s low pressure center passes to our
northeast, a strong cold front will pass through the area sending
Behind this cold front, westerly winds will markedly uptick
overnight within the cold advection regime and robust pressure
gradient between the deepening low and an incoming Canadian high
pressure around 1035 mb. The steepened low-level lapse rates and
unidirectional boundary layer flow look to support decent
momentum transfer to at least 2,000 ft where there is 45 to 50 mph
flow, despite the time of the day. It`s possible the overnight
hours keep gusts a little down from peak gust potential, but in
the morning hours the cold conveyor belt is potent enough that the
45 mph gusts should at least occasionally materialize. There is a
consistent signal of stratocumulus wrapping around in the morning
but this looks fairly thin and should not retard much of the
momentum transfer. With the cloud layer, albeit thin, overlapping
the -8C to -13C layer, some "low quality" flurries are likely to
pop up primarily in the northern CWA. These should not be a big
deal, but with the wind there could be some brief visibility
reductions. Winds will gradually ease late morning into the
afternoon from west to east.
The cold advection will not allow temperatures to recover on
Monday, with possibly a couple degree climb at best in the
afternoon. Wind chills will be in the teens much of the day. The
high pressure will spread over the area during Monday night with
winds dropping off. Before they do, some single digit wind chills
may unfold during the evening. Low temperatures Monday night have
the potential to drop down widespread into the single digits
(even a -1 from the 12Z MET guidance for Rochelle). One fly in
the ointment to that is the likelihood of incoming high to mid
clouds late Monday night/early Tuesday morning. We accounted for
those in the forecast, but if the clouds look less likely, the
lows will need to be inched downward.
Issued at 233 PM CST Sun Dec 5 2021
Tuesday through Sunday...
Guidance continues to fade away from any substantial precip
across the area Tuesday into Tuesday night as a trough embedded in
an expansive longwave trough across central and eastern North
America becomes rather sheared over the Great Lakes region. An
exceptionally dry antecedent airmass marked by sub-zero surface
dewpoints and pwats at or under 0.25" will inhibit widespread
precip potential even with modestly favorable mid and upper-level
dynamics in the region. Initially Tuesday morning, weak WAA and
fgen under the right entrance of an upper jet streak west of the
CWA may generate enough precip aloft for some flurries to reach
the surface into the northern CWA. A second area of light snow may
then develop later Tuesday into Tuesday evening ahead of a jet
streak approaching southern IL. Finally, light snow potential will
linger overnight into Wednesday as the embedded trough swings
through the area. Overall, most of the period will likely be dry,
with the setup favoring a period or two of higher probability
light snow with little to no QPF/accumulation.
Tuesday will be the coldest day so far this season with highs
struggling to rise into the mid 20s under decent cloud cover.
Winds should be fairly light in the morning, but wind chill values
near zero are likely across much of northern Illinois around
Another deep trough with an expansive low-level WAA and surface
trough response is progged to bring a bout of more unsettled
weather to the area Thursday into Thursday night. Thermal profiles
support mostly liquid precip given a notable warm nose advecting
in from the south, but some mixed precip potential exists at onset
with low- level wetbulb temps initially below freezing.
Another strong wave late Friday into Saturday will bring more
unsettled weather to the Great Lakes region. Given the variability
in guidance this far out, little detail can be provided. However,
the pattern favors some wintry precip during late week through
For the 00Z TAFs...
Aviation Forecast Concerns:
* IFR/LIFR ceilings and IFR vsbys this evening.
* Strong west winds developing later tonight, and persisting
Monday. Strongest winds with gusts near 40 kt through Monday
morning, easing gradually afternoon/evening.
Surface low pressure was over the upper Mississippi Valley early
this evening, with an occluded cold front stretching southeast to
a triple point with a warm front over northern IL. Light winds and
light rain/moist low level conditions across the forecast area
had resulted in LIFR cigs and IFR visibilities across the
terminals this afternoon, with ceilings 200-400 feet and
visibilities of 1 1/2-2SM common in drizzle/fog. These conditions
will persist for another couple of hours, though should begin to
improve as the surface frontal trough moves slowly east across the
terminals. Stronger west winds will lag the front a bit, but will
become strong and gusty late this evening/overnight. With the
stronger winds, an intrusion of drier low level air will allow for
rapid improvement to MVFR/VFR cigs and VFR visibilities. As the
main upper trough moves over the area Monday morning, a period of
high- MVFR cigs and a few snow flurries or light snow showers are
possible, though VFR conditions will return by afternoon.
As winds shift westerly later this evening, speeds will increase
with gusts 25-30 kt. Strongest winds look to arrive shortly after
midnight however, as strong low level cold advection maximizes
mixing and frequent gusts around 40 kts develop. This persists
through Monday morning, before a very gradual decrease occurs
during the afternoon/early evening. Direction should be pretty
consistent in the 280-300 degree range during this time.
Issued at 310 PM CST Sun Dec 5 2021
South to southwest winds to around 25 kt early this evening. A
lull in the winds is expected mid evening ahead of a trailing
strong cold front. This front will sweep across southern Lake
Michigan early overnight, shifting winds to the west/northwest
with speeds increasing to gales to 40 kt. These stronger winds
will continue through Monday morning and begin to slowly diminish
Monday afternoon into Monday evening. cms/MTF
ILZ106-ILZ107-ILZ108...2 AM Monday to noon Monday.
IN...Wind Advisory...INZ001-INZ002...2 AM Monday to noon Monday.
LMZ745...midnight Monday to 3 PM Monday.
Small Craft Advisory...nearshore waters until midnight Monday.
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Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
815 PM CST Sun Dec 5 2021
Issued at 754 PM CST Sun Dec 5 2021
The forecast is progressing much as anticipated. At 800 PM the
front looks to be stretching from near KIJX to KSTL to just north
of KVIH to just north of KJLN. It should pick up some speed to the
southeast as the mid/upper level trough continues to dig into the
Upper Mississippi Valley and the eastern Plains. Convection
allowing models, particularly the HRRR, has been very consistent
in developing convection between 02-04Z. This looks reasonable
particularly in light of the accelerating warm front producing
additional low level convergence, in addition to more robust low
level warm advection due to the strengthening low level jet just
ahead of the front. GOES is showing rapidly increasing low level
clouds ahead of the front...most likely in response to the
aforementioned warm advection. Indeed, convection has increased a
bit in coverage in the past 15 minutes or so as I`m writing, and
this trend should continue.
Latest RAP analysis shows around 1000 J/Kg MLCAPE and 1000-1500
J/Kg MUCAPE along with 40+ kts of deep layer shear over the
eastern Ozarks and south central/southwest Illinois. 0-1km
helicity is 300 M2/s2 and and the bulk shear is 30-40kts. This
would be pretty favorable for rotating updrafts and therefore severe
storms. Damaging wind and a few tornadoes will likely be the
primary threats from any storms that can develop strong enough
.SHORT TERM... (Through Late Monday Night)
Issued at 224 PM CST Sun Dec 5 2021
The primary item of interest in the short term will be the potential
for showers and thunderstorms across southeast Missouri and
southwest Illinois later this evening, along and ahead of an
advancing cold front.
Earlier today, scattered elevated showers along the leading edge of
an advancing warm front moved through parts of the area, producing
occasional bursts of moderate rain and a few lightning strikes. This
activity has finally moved northeast of the area, leaving behind a
stubborn deck of broken stratus. Temperatures have warmed nicely
into the 60s in parts of central Missouri where clouds have begun to
clear, with cooler temps in areas that have yet to see much sunlight
today. These clouds are expected to gradually thin a bit more over
the next few hours, although some areas may not completely emerge
from them until the cold front sweeps through late this evening.
Meanwhile, surface observations indicate that abnormally rich low-
level moisture has begun to surge northward into the mid-Mississippi
River valley, with dewpoints in the low 60s now across the bootheel
region of Missouri. This is expected to continue over the remainder
of the afternoon, and by the time the cold front arrives during the
evening, much of the area will see surface dewpoints well above the
90th percentile for this time of year. While mid-level lapse rates
will be poor, this abundant low level moisture will likely be enough
to generate at least marginal instability, perhaps between 250 and
750 J/kg across southeast MO and southwest IL. As the front
approaches from the north, the increased forcing is likely to
trigger at least scattered convective development during the evening
hours. The primary question will be exactly where this occurs, as
CAMS continue to exhibit some disagreement even now. This will most
likely occur south of the I-44 corridor, although it`s not
completely out of the question that a few of the initial cells could
begin to form as far north as St. Louis. In any case, it does appear
that this activity will not reach maturity until late in the evening
and well south of the St. Louis/Columbia/Jefferson City metro areas.
While instability will be marginal, strong forcing and ample shear
may provide enough ingredients to produce a strong, maybe even
severe, thunderstorm or two in the areas where storms manage to
form. Again, it seems like the bulk of this threat will be farther
south across the bootheel region and far southern Illinois, but it
can`t be completely ruled out farther north across parts of the
Ozarks either. Where this occurs, large hail, gusty winds and even a
brief tornado can`t be ruled out. Areas north of the I-44
corridor can expect mostly dry conditions the rest of the night,
aside from a few weak showers in the evening right along the
Showers and storms will quickly move southeast, and will likely be
out of the area by midnight or so. Otherwise, gusty southerly winds
will turn to the northwest overnight as the front passes, and may
gust up to around 30 or 35 mph at times. This will continue through
Monday afternoon before winds finally weaken. Dry, sunny, blustery
conditions can be expected Monday, with temperatures about 5 to 10
degrees below average.
.LONG TERM... (Tuesday through Next Sunday)
Issued at 224 PM CST Sun Dec 5 2021
The forecast for most of the work week continues to trend towards
the dry side, particularly regarding the potential for wintry
precipitation Tuesday and Wednesday. While temperatures will
certainly be cold enough to support frozen precipitation during this
timeframe (lows will fall into the 20s both Tuesday and Wednesday
mornings), latest model trends continue to suggest that
precipitation will be difficult to come by, and very light if it
does precipitate at all. It remains possible that some light snow
may fall at various times between Tuesday morning and Wednesday
morning, but it may only amount to some flurries with little to no
accumulation. Otherwise, expect temperatures to only reach the 30s
Tuesday afternoon, and back up to near normal Wednesday afternoon.
Over the latter half of the week, another rapid warming trend can be
expected thanks to the return of building high pressure aloft and
southerly low level flow. As such, temperatures Thursday and Friday
are likely to climb back to well above seasonal averages,
particularly Saturday when most ensemble members produce high
temperatures at least 10 degrees above average. While a weak
disturbance may move through the area sometime Thursday, this period
is also expected to remain dry.
Models continue to hint at the possibility of more active weather
returning over the weekend, but model spread remains too great to
make too many definitive proclamations just yet.
.AVIATION... (For the 00z TAFs through 00z Monday Evening)
Issued at 508 PM CST Sun Dec 5 2021
A cold front which is currently moving through northwest Missouri
will pass through the forecast area this evening. The primary
impacts from this frontal passage will be showers and
thunderstorms across the eastern Ozarks into southwest and south
central Illinois as well as a wind shift to the northwest and
wind gusts of 20-30kts behind the front. Some of the storms in
southeast Missouri and southern Illinois could produce wind gusts
in excess of 45kts as well as a tornado or two. Thunderstorms
could also reduce the visibility to IFR in heavy rain. Rain and
storms should move southeast of the forecast area by 06Z or
shortly thereafter. VFR flight conditions with gusty northwest
winds will then prevail through Monday.
SPECIFICS FOR KSTL:
The cold front should pass through Lambert between 03-04Z. Current
indications are that any showers and storms that form will stay
south-southeast of the terminal...but it looks close. Gusty
northwest flow and VFR flight conditions are expected to prevail
Area Forecast Discussion
National Weather Service Mobile AL
600 PM CST Sun Dec 5 2021
00Z issuance...Brief periods of IFR to LIFR ceilings due to low
clouds and fog can be expected tonight, however widespread dense
fog is not expected due to the cloud cover. A band of rain showers and
possible embedded isolated thunderstorms will move into inland
portions of SE MS and SW AL after mid-morning Monday, resulting in
localized MVFR ceilings and visibilities. /13
.PREV DISCUSSION... /issued 348 PM CST Sun Dec 5 2021/
NEAR TERM UPDATE /Now Through Monday/...A shortwave trough over the
central and northern Great Plains will move to the eastward through
the near term. The axis is forecast to shift east of the Mississippi
River Monday morning, and amplify on Monday as the trough digs
across the Upper Midwest and adjacent Great Lakes and Ohio Valley
region. A southerly low level flow pattern will be prevalent through
tonight as low level ridging extends across the western Atlantic and
much of the eastern and southeastern U.S. The moist southerly flow
will keep skies partly to mostly cloudy early this evening, with
clouds continuing to thicken overnight. Dry conditions will remain
through tonight, with patchy inland fog developing tonight over a
small portion of south central AL. A Dense Fog Advisory is not
expected at this time due to the patchy nature of the fog and
increasing cloud cover inhibiting radiational cooling.
Winds will shift southwesterly Monday morning ahead of a cold front
approaching from the northwest that will advance close to the I-65
corridor by late Monday afternoon. A zone of enhanced deep layer
ascent will become focused along the cold front during the day
Monday, and the latest short range model guidance remain in good
agreement with the development of a forced line of convection
advancing into our southeast MS and interior southwest AL counties
during the late morning hours on Monday. This line will then
continue to move southeastward across the remainder of CWA by late
Monday afternoon. There will be up to around 40 knots of deep layer
shear available across interior southeast MS and southwest AL as the
convective line approaches these northwestern counties during the
late morning and early afternoon hours. The higher resolution HRRR
and NAM guidance also indicates some weak instability in this region
with up to 500-1000 J/KG of MLCAPE available during peak heating, so
a couple of embedded stronger storms within the line may become
briefly capable of producing localized 40-60 mph gusts. SPC has
outlined a Marginal severe risk over much of our area, but the best
potential of a strong to marginally severe storm will probably be
most favored along and northwest of I-65 during the early to mid
afternoon hours prior to the gradual weakening of the line. Rainfall
amounts will not be overly heavy, but there could be a few spots
that receive between 0.5 to 1 inch of rain within the heaviest
convection along and northwest of I-65.
Lows tonight range from the upper 50s to lower 60s, with the
exception of mid 60s at the beaches. Highs Monday will range from 72
to 77 degrees, with a few upper 70s across portions of south central
SHORT TERM /Monday night Through Wednesday night/...A busy short
term period lies ahead as our initial upper level trough shifts
northeast across the northeastern U.S. and a surface cold front
pushes through the area. The cold front likely stalls somewhere
near the coast Monday night into Tuesday morning before beginning
to slowly lift back north as a warm front Tuesday afternoon into
evening. Another pair of shortwaves move through the area, first
one embedded within the subtropical jet Tuesday afternoon, and the
next one associated with a broad upper level trough Wednesday
afternoon. Prior to their passage, some attempt at warm air
advection is made over our coastal zones, seemingly in a battle
against the surface high to the north providing for cold air
advection over the area. As a result of this, expect a general
isolated to scattered coverage of showers and thunderstorms,
primarily elevated, across the area Monday night through Tuesday
night. Warm air advection prevails with better synoptics moving in
Tuesday night into Wednesday which should allow for the warm front
to finally surge inland, perhaps allowing for a few surface based
showers and storms to manifest over the coastal counties Wednesday
morning into afternoon. Prospects for severe weather potential
remain a bit uncertain, with initial threat for isolated damaging
winds and perhaps an isolated tornado early on Monday evening
associated with the cold front where marginal CAPE and ample shear
are present. Any future chances at severe look meager beyond this
except for perhaps Wednesday morning into afternoon across far
southwestern AL into the Fl panhandle where some surface based
convection seems possible amidst meager SBCAPE and 50 to 60kts of
sfc-6km wind shear.
Temperatures are going to solely rely on the evolution of the cold
front and when that lifts back north as a warm front. Currently it
looks like a majority of the CWA is in for a relatively chilly
Monday night and Tuesday with the front remaining along the coast
or just offshore in the marine zones. Lows dip into the lower to
middle 40`s over far interior southwestern AL and southeastern MS,
with lower to middle 50`s along and southeast of the I-65
corridor. Highs struggle to climb with extensive cloud cover,
rain, and cold air advection ongoing in the low levels with middle
to upper 50`s inland and lower to middle 60`s along the I-65
corridor. Some isolated upper 60`s are possible across the FL
panhandle if the front doesn`t quite clear the area. Tuesday night
features little diurnal change in temperatures with lower to
middle 50`s for most locations, and perhaps upper 50`s to lower
60`s along the immediate coast as the warm front begins to lift
north into the area. Wednesday will offer some improvement on
temperatures, reaching the lower to middle 60`s for most
locations. Across the coast, highs in the upper 60`s to lower 70`s
can be expected. Lows Wednesday night will fall into the middle
to upper 40`s inland and lower 50`s across southeastern MS,
southwestern AL and the FL panhandle. It`s important to note that
there continues to be great uncertainty in the temperature
forecast as models continue to differ on the exact placement of
frontal features and their evolution, and there will likely be
changes to the current temperature forecast moving forward,
particularly for the Tuesday into Tuesday night time frame. MM/25
EXTENDED TERM /Thursday Through Sunday/...The extended term
relaxes a bit early on as the upper level pattern reloads. A weak
shortwave tracks to the north Thursday as upper level ridging
settles in across the central Gulf of Mexico, putting us in
generally zonal to southwesterly flow aloft for Friday and
Saturday. A potent upper level trough begins to dig across the
western U.S. into the central Plains states Thursday night into
early Saturday before shifting east across the southeastern U.S.
Saturday night into Sunday. At the surface, high pressure over the
southwestern Atlantic noses west, allowing for surface
southerlies to take hold and a general warm air advection regime
to set up shop for a majority of the extended period into Saturday
night before a cold front moves through the area Saturday night
Overall weather is going to be Spring-like with isolated to
scattered showers and thunderstorms possible each day. Saturday
into Saturday night bears watching still as a favorable synoptic
setup exists for the potential of severe thunderstorms across the
southeastern United States. Trends in model guidance will be
monitored moving forward. An anomalously warm air mass takes
shape across the area during the extended period with
temperatures warming into the lower to middle 70`s Thursday, and
middle to upper 70`s for Friday and Saturday. It`s not out of the
realm of possibility temperatures can trend a little warmer and
flirt with record highs Friday into Saturday. Sunday in the wake
of the cold front temperatures will only reach the lower to middle
60`s. Current forecast low temperatures are nothing short of
remarkable, with Thursday and Friday nights featuring lows in the
lower 60`s to perhaps even middle 60`s across far southeastern MS
and southwestern AL/FL panhandle. To put this into perspective,
our typical average highs hover in the lower to middle 60`s for
this time of year, with average lows in the lower to middle 40`s.
Saturday night will likely feature cooler temperatures in the
upper 40`s to lower 50`s. MM/25
MARINE...Small craft should exercise caution after midnight beyond
20 nm due to southerly winds increasing to 13-18 knots. Otherwise, a
light to moderate onshore flow will persist through Monday, followed
by a light to moderate offshore flow developing over the near shore
waters Monday night as a cold front moves just offshore and stalls.
A light to moderate onshore flow will resume Tuesday afternoon,
shifting westerly on Wednesday momentarily, then back to an onshore
flow through the remainder of the forecast. Small craft will need to
exercise caution at times later in the week as southerly winds
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Area Forecast Discussion
National Weather Service Norman OK
550 PM CST Sun Dec 5 2021
(This evening through Monday)
Issued at 138 PM CST Sun Dec 5 2021
Very warm and slightly breezy conditions have developed this
afternoon ahead of an approaching cold front, now nearing central
KS. Southwest winds will decrease around sunset as decoupling
occurs. However, later tonight a tight pressure gradient and
a warm boundary layer will result in very breezy north winds with
fropa as remixing occurs. 45-50 kt speeds will be present around
10 PM to midnight near the top of the mixed layer. The HRRR
continues to suggest a very brief period around 11 pm to midnight
of gusts near 45 to 50 kt across west central OK. For this reason
we`ve decided to issue a wind advisory west of I-35 and
along/south of I-40. This advisory might be expanded northward
depending on early trends this evening.
Moist convection will also accompany the front this evening into
the overnight hours mainly across SE OK where moisture will be
sufficient. Enough deep layer shear and elevated instability could
support storm organization over far SE OK, where marginally
severe hail and damaging winds would be the main threats late
tonight. Do not anticipate widespread storm coverage, however,
and most of the PoPs will quickly decrease below mentionable by 4
(Monday night through next Saturday)
Issued at 220 PM CST Sun Dec 5 2021
A surface ridge, centered over Oklahoma Monday night, will allow
temperatures to cool quickly during the evening. Overnight, the
wind will increase some along with a gradually increase in high
clouds over the northern half of Oklahoma. The circulation around
high pressure over the Upper Midwest/Ohio Valley Tuesday will
keep most of the state on the cooler side Tuesday.
Low pressure will deepen over eastern Colorado on Wednesday as a low
amplitude wave approaches. Breezy to perhaps windy conditions may
result, especially by afternoon. Moisture return will keep
afternoon humidity from falling too much, but the exception might
be parts of western Oklahoma. Will need to keep an eye out for
possible fire weather concerns Wednesday. A weak frontal boundary
will move through part of the state on Thursday but will do little
to keep temperatures from warming back into the upper 60s and
A lead shortwave trough will move across the central Plains on
Friday. Breezy and very warm conditions will at least elevate fire
weather conditions during the afternoon. This wave will also push
a front through the state Friday night. Enough cold air may
overspread the region for wintry precipitation Friday night into
parts of the day Saturday. This system will move east of the area
by early Sunday with another warming trend possible into early
next week. At this time, any winter weather precipitation that
occurs Friday/Saturday should be light.
Issued at 549 PM CST Sun Dec 5 2021
VFR will apply through the forecast period, although gusty north
winds will accompany a cold front tonight. Expect winds to shift
to the NW and then N around 02 to 05Z for all terminals. Gusts
may briefly near or exceed 40 kt around 03-10Z. A few high clouds
are expected but any precipitation/tsra should remain east and
south of the terminals across SE OK.
Issued at 138 PM CST Sun Dec 5 2021
An Upper Air flight is not planned for tonight.
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 35 46 27 52 / 10 0 0 0
Hobart OK 34 48 25 54 / 0 0 0 0
Wichita Falls TX 39 52 28 59 / 0 0 0 0
Gage OK 26 43 24 48 / 0 0 0 0
Ponca City OK 31 45 27 47 / 0 0 0 10
Durant OK 42 54 32 56 / 60 0 0 0
OK...Wind Advisory from 10 PM this evening to 4 AM CST Monday for
Wind Advisory until 2 AM CST Monday for OKZ004>007-009>012.
TX...Wind Advisory from 10 PM this evening to 4 AM CST Monday for
Area Forecast Discussion
National Weather Service Pueblo CO
731 PM MST Sun Dec 5 2021
Issued at 710 PM MST Sun Dec 5 2021
- Continued strong winds tonight before decrease after midnight.
- Light snow expected tomorrow night into Tuesday.
- Still watching the track of the end of the work week system...
UPDATE Issued at 612 PM MST Sun Dec 5 2021
The strong cold front that blasted through the region this
afternoon and evening continues to cruise southward leaving behind
gusts 35-50 MPH. This trend will continue for the next few hours
before decreasing enough to allow folks to get some peaceful
sleep. Also watching a deck of stratus work it`s way in from the
north so expecting we do fill in quite a bit overnight as the
east-southeast flow becomes established.
.SHORT TERM...(This evening through Monday)
Issued at 253 PM MST Sun Dec 5 2021
Cold front racing southward through the plains of northeast Colorado
this afternoon, as upper level trough over the nrn plains heads into
the Great Lakes. Ahead of the front, very dry/warm/windy conditions
were noted over southeast Colorado, and Red Flag Warning was
verifying along I-25 and back into the eastern mountains as humidity
has dropped below 10 percent at many locations. For this evening,
cold front will continue to drop quickly southward through the
plains, driven by large (5mb/3hr) surface pressure rises over ern WY
and nern CO. HRRR suggests a brief period of gusts over 50 mph
immediately following the frontal passage, mainly over the plains
east of I-25, and given upstream observations, expect some brief
blowing dust in open areas as well. Over the mountains and interior
valleys, breezy w-nw Winds will gradually diminish this evening,
though higher peaks will likely see gusty winds persist through the
night. As winds gradually subside and turn s-se on the plains after
midnight, some model soundings suggest stratus may develop over El
Paso County, as rather narrow saturated layer forms under increasing
upslope flow. Min temps will end up fairly chilly at many locations,
with teens widespread and some single digits over high mountain
valleys. On Monday, much cooler conditions area-wide in the wake of
the cold front, and a few spots near the Palmer Divide may stay only
in the 30s as clouds linger into early afternoon. Winds will be
lighter than Sun as most locations, though with lee trough deepening
along I-25 in the afternoon, south winds over the eastern plains
toward the KS border will likely gust 20-30 mph in the afternoon.
.LONG TERM...(Monday night through Sunday)
Issued at 253 PM MST Sun Dec 5 2021
Late Monday into Tuesday, westerly flow aloft will increase ahead of
the next upper-level trough, and the transported moisture and
upslope flow will allow for orographic snowfall across parts of the
Continental Divide and central mountains. As the system translates
across the Rockies, the San Juans will be picking up around 1 inch
of snow, while some parts of the Continental Divide could be seeing
2-4 inches over some of the taller peaks. Other higher-elevation
areas could be seeing a light dusting as the system passes by, with
light isolated to scattered showers over our higher terrain,
depending on local orographic interactions. Temperatures on Tuesday
will be slightly above average, and a few degrees above Monday, with
high-40s and low-50s anticipated over most of the area.
Northwest flow aloft increases starting early on Wednesday before
becoming more westerly ahead of some more Pacific energy digging
into the region late Wednesday into Thursday. This will lead to
warmer and drier conditions over the plains both days, with low-60s
expected in most areas. Over the mountains, snowfall chances will
increase Wednesday night into Thursday along and west of the
Continental Divide as the moisture and westerly flow set up
supporting orographics again. Models continue to disagree on the
exact of the upper trough into next weekend. However, the
majority of ensemble solutions and some of the deterministic
guidance shows the trough deepening and digging into the southern
states, as well as slightly slowing down the progression of the
system, which will increase chances for more widespread
precipitation over the mountains as well as the eastern plains.
Temperatures Friday and Saturday are expected to cool down closer to
seasonal averages, before warming significantly on Sunday as upper-
level ridging is currently expected to return.
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 253 PM MST Sun Dec 5 2021
At KCOS, VFR into early evening, with a cold frontal passage 23z-
01z, then MVFR stratus developing by 06z and persisting into midday
Mon before slowly clearing. North winds will gust 30-40 kts
following the fropa this evening, before weakening and turning s-se
At KPUB, VFR the next 24 hrs, with a period of low VFR cigs
developing toward 06z tonight and persisting into midday Mon. Winds
will become n-ne behind a cold frontal passage 00z-02z, with gusts
over 30 kts until 06z. Lighter s-se winds then develop Mon morning.
At KALS, VFR tonight and Monday, with winds staying under 15 kts
through the period.
Area Forecast Discussion
National Weather Service Springfield MO
508 PM CST Sun Dec 5 2021
...00Z AVIATION UPDATE...
1. Strong to isolated severe storms tonight south of I-44.
2. Cooler and drier weather early next week - Elevated Fire threat.
3. Another warm up likely by late week.
4. Additional precip chances next weekend.
.SHORT TERM...(This evening through Monday)
Issued at 145 PM CST Sun Dec 5 2021
It was a warm and breezy afternoon as widespread clear skies
have allowed for mixing of higher winds to the surface. Wind gusts to
40mph have been observed so far. Temperatures were in the upper
60s to lower 70s. Big changes are on the horizon however, as a
strong cold front was currently working its way southeast through
Storm Potential Tonight: The cold front will likely enter the
northwest CWA by 6-7pm. The airmass currently is capped and will
likely remain capped as the front enters the area. Strong lift,
associated with mid level disturbances to the north and south of
the area, will allow for convection to develop as the front nears
the Interstate 44 corridor as early as 8pm. 12Z HREF analysis
suggests that updraft probabilities will increase to the southeast
of Interstate 44 as the front moves through. Updraft helicities
are strongest from the Missouri-Arkansas border and points south.
RAP forecast soundings from Branson to West Plains are consistent
in showing about 1000j/kg of ML cape, 40kts of 0-6km shear, and
steep mid level lapse rates. Therefore the ingredients are there
for a few strong to severe storms. The low level hodograph shows
a southwest to west flow, which should keep the tornado threat
very low. Higher QLCS potential with more organized storms looks
to remain just south of the area. Storms will be fast moving with
most areas seeing less than 0.50 in of rainfall. Storms will be
out of the area by 1-2am.
A strong cold front will usher in dry and cold air overnight, with
most locations seeing wind gusts up to 35 mph and temps in the 30s
by sunrise Monday. HREF cloud data suggests that skies should
remain partly cloudy during the day, and with strong cold air
advection, highs will struggle to warm into the lower to middle
40s. Lower humidity and gusty winds will lead to elevated fire
weather conditions Monday.
.LONG TERM...(Monday Night through Sunday)
Issued at 145 PM CST Sun Dec 5 2021
Zonal to slightly northwest flow aloft will persist Tuesday into
the mid week period. A weak disturbance moves into the area
Tuesday night into Wednesday. Moisture looks to be limited, with
the NBM only showing a 10-15 percent chance for measurable precip.
More than likely only a few flurries or sprinkles will occur with
A steady rise in temperatures looks likely as we head to the end
of the week. Ensemble cluster analysis shows good consensus in
another mid level ridge developing over the central US. NBM
temperatures support 50s Wednesday and 60s Thursday and Friday.
The flow turns more southwesterly on Friday, with cluster analysis
showing the potential for max temps to reach 70 degrees. This is
also seen in the 75th percentile of NBM guidance.
Next Weekend: While ensembles are in decent agreement that a upper
level trough will develop across the Rockies, there is
disagreement in the timing and structure of the wave as it ejects
into the Plains. At this time, NBM probabilities for precip are
highest across the southeast half of the area Saturday into
Sunday(40-60 percent). This also matches the ensemble cluster
analysis and CIPS extended analogs. Current probabilities for any
measurable snow are quite low at this time (20 percent). NBM
temperatures generally keep highs in the 40s to around 50 with
lows in the 30s during this time.
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 453 PM CST Sun Dec 5 2021
Current models show a strong cold front pushing through the
region this evening after 00Z, bringing a chance of
thunderstorms, mainly at KBBG around 03Z. Cannot rule out a storm
at KSGF, although chances are low at this point. Current southwest
winds will shift behind the front towards a more northwesterly
direction, and gusts up to 30 kts will be likely into Monday. VFR
flight conditions look to persist through the rest of the TAF
period, however visibilities and ceilings could lower with the