Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/23/20
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
535 PM MST Sun Nov 22 2020
Have gone ahead and issued a dense fog advisory for tonight for much
of the east slopes of the central mountain chain, as well as the
Pecos Valley and portions of east central NM. Dense fog already being
reported at CLines Corners and Sierra Blanca Airport, and HRRR
indicating the low visibilities becoming more widepsread over the
advisory area as the evening progresses. May need to consider
portions of ne NM as well, but will see how conditions progress
during the next few hours. Updated ZFP transmitted as well as the
.PREV DISCUSSION...459 PM MST Sun Nov 22 2020...
00Z TAF CYCLE
Widespread terrain obscurations from the RGV eastward to the TX
border in IFR to LIFR cigs/vsbys in clouds, br, fg, dz and -ra. Light
shsn possible over the Sangre de Cristo mt peaks. Some improvment
expected aft 23/19Z. From the RGV wwd, lcl MVFR to IFR conditions in
clouds and precipitation occasionally obscuring terrain, with
precipitation most likely over the nwrn mts. Occasional ely wind
gusts at KABQ to around 35kt to continue until around 23/03Z before
.PREV DISCUSSION...320 PM MST Sun Nov 22 2020...
It`s beginning to feel like November weather, with cooler
temperatures, drizzle across the eastern plains, and mountain snow
showers (above 9500`) continuing through Monday. A stronger
disturbance will cross the state Monday night into Tuesday, with
several inches up to a foot forecast across portions of the northern
mountains. It`ll be dry and mild for Thanksgiving, with another
potential system on the horizon for Black Friday.
SHORT TERM...(TONIGHT THROUGH MONDAY NIGHT)...
95 kt subtropical jet overhead while a surface backdoor cold front
continues to push west-northwest through western NM this afternoon.
Upslope stratus clouds with areas of drizzle and patchy fog will be
the rule tonight from the east slopes of the central mountain chain
eastward into West TX. Meanwhile, an upper-level trough is dropping
south-southeastward just off-shore of the OR coast as of this
writing. This feature is forecast to result in sufficient
atmospheric lift to generate areas of drizzle or light rain across
eastern NM while western locales see scattered rain showers,
isolated thunderstorms along with snow above about 9500` late
tonight through Monday night. The above mentioned upper-level trough
is forecast to drop into southern UT/northern AZ Monday night,
possible closing off over/near the Four Corners. Snow levels in
northwest NM will drop rapidly in northwest NM behind the associated
cold front Monday evening. Winter weather advisories may be
necessary for the Tusas and northern Sangre de Cristo mountains
Monday night into Tuesday with upwards of 10" possible above 8000`
feet or so by Tuesday morning.
LONG TERM...(TUESDAY THROUGH SUNDAY)...
As the upper-level trough continues to pass north of the state
Monday night into Tuesday and begin to close off, most areas along
and east of the central mountain chain will experience impacts in the
form of stronger winds, reaching near Wind Advisory speeds. Snow
levels fall from 9500` Monday night to valley floors by Tuesday.
Several inches up to a foot of snowfall are forecast for the Sangres
and Tusas Mountains (marginal for any Winter Weather Advisories at
this point), with potential travel impacts across these mountain
passes. Drier air filters in behind the low late Tuesday, cutting off
any precipitation and leaving 700 mb temperatures in the
-5 to -6 C degree range.
By Wednesday, it`ll be mainly zonal flow with a few stronger
westerlies. Thanksgiving Day looks to be the warmest day of the week,
with dry, mild conditions and temperatures near to a few degrees
above normal across much of the state. Another system is on the
horizon for Black Friday into Saturday of this week. Temperatures
at the 700 mb level are showing in the -10 C, but latest models have
gotten weaker with the amount of moisture. There are also some
differences with placement and timing, as the GFS is predicting an
open wave system, while the ECMWF remains a closed low. Stay
Weather more typical of November will keep critical fire weather out
of the forecast through the work week. Areas of drizzle or light
rain will increase across eastern NM tonight and Monday while a
Pacific storm system brings rain and mountain snow chances to
central and especially northern NM Monday through at least Tuesday
morning. West winds will increase somewhat on Wednesday afternoon
with very localized near critical condtions expected near Clines
Corners. The next storm system on the horizon is forecast to bring
chances for lower elevation rain and mountain snow to central and
northern NM on Black Friday.
Dense Fog Advisory until 8 AM MST Monday for the following zones...
Area Forecast Discussion
National Weather Service Boston/Norton MA
955 PM EST Sun Nov 22 2020
Strengthening low pressure tracks through New York overnight
and across Northern New England Monday. This will swing a cold
front across the region, bringing showers with locally heavy
rain & warming temperatures. Behind the front Monday afternoon
and Tuesday, drier, blustery and colder. High pressure moves
offshore Wednesday with milder conditions into New England. Low
pressure approaches the region Thanksgiving along with scattered
showers. Behind the departing low, dry weather returns Friday.
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Main change is to the timing of precipitation, which is slowed
until after 1 AM.
945 PM radar mosaics show showers over Central NY and PA moving
east. There are some showers farther east in NY, and so widely
scattered showers are possible in Western MA/CT during the
middle hours of tonight. Movement of the main line extrapolates
to the Berkshires around 1 AM/06Z and then across Srn New
England to the eastern coast around 5-6 AM.
Temperatures in NW Mass are roughly 37 with dew points 33-34.
These will trend warmer overnight. So there is little/no
likelihood of freezing/frozen pcpn overnight.
Low level flow shifts from the southeast and south overnight
with warm air moving up. Thus temps expected through the 50s to
near 60 by daybreak, except rising thru the 40s across
.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Column finally saturates high amplitude trough advects a deep
moisture plume northward over the area with PWATs 1+ inches during
the morning hours to midday day in eastern MA. Strong jet dynamics,
mid level trough beginning to take on a negative tilt, RRQ of upper
level jet streak, strong frontal convergence and some elevated
instability supports heavy showers, local downpours and isolated
thunder during the morning hours and spilling into early afternoon
across eastern MA. Thus beneficial/soaking rains with qpf ranging
from 0.25-0.75 inches and isolated amounts of 1+ possible across RI
into southeast MA. Also, we will have to monitor the prospects of a
fine line or broken line of low top convection along the cold front.
However with core of the low level jet removed well to the northeast
of our region along the ME coast, thinking threat of any strong to
damaging winds is minimal. But will have to watch model trends and
how it evolves Monday morning.
Strong low level warm air advection during the morning hours will
result in highs of 60-65 across eastern CT-RI and eastern-central
MA, mid to upper 50s elsewhere. Even a touch humid as dew pts rise
to near 60 across RI and southeast MA. Then temps crash with cold
frontal passage, occurring late morning across CT into western-
central MA, then into RI and eastern MA early afternoon. Expect
drying trend along with some sunshine but blustery. In fact WNW post
frontal winds could gusts up to 40 mph.
Dry but blustery and colder with lows in the upper 20s and lower
30s. However gusty NW winds will result in wind chills in the teens
and 20s. Mostly clear conditions, however strong cold air advection
across Lake Ontario combined with upslope flow over the Berkshires
and Litchfield Hills, will result in lake effect clouds over western
MA/CT. Low risk of scattered flurries or snow showers as well in
.LONG TERM /TUESDAY THROUGH SUNDAY/...
* Cooler than normal Tuesday and Tuesday night with dry weather. May
be a bit breezy early on Tuesday.
* Near to above normal temperatures for the rest of the extended.
Next shot of rain is late Wednesday or on Thanksgiving.
* Another shot of unsettled weather over the weekend or early next
Tuesday and Tuesday night...
Ridge axis builds from the central Great Lakes/Ontario into
Quebec/Ontario and the eastern Great Lakes by Tuesday evening. The
ridge shifts into New England Tuesday night, but flattens out a bit
as a trough lifts into the mid Mississippi River Valley. The surface
high builds into northern New England from Ontario on Tuesday. The
high moves offshore into the maritimes Tuesday night.
Pressure gradient remains tight due to the exiting system and
incoming high. This will relax as the day progresses as the surface
high builds into northern New England. So, should be a bit breezy to
start with winds diminishing as the day goes on. Will have -2 to -6
degree Celsius 925 hPa air advect in from the WNW to NW during the
day. This will keep it colder than normal, but should see some
downsloping keeping it a bit warmer across the Merrimack and CT
River Valley. Went with the 75th percentile of guidance, which
results in highs in the 30s across the higher terrain and low to mid
The high slides overhead Tuesday night into Wednesday morning. This
will bring light winds. Should have clear skies at the beginning of
the night, but mid to high clouds will move in as a warm front lifts
into the eastern Great Lakes. This should inhibit radiational
cooling a bit, so have only lowered temperatures to the 25th
percentile of guidance. Results in the lows in the upper teens to
20s across much of the region. If it takes longer for the clouds to
move in then temperatures will need to be lowered further in future
Wednesday through Thanksgiving...
Neutrally tilted trough will be situated over the Mid Mississippi
River Valley early on Wednesday. This feature will be deamplifying
as it lifts into the central Great Lakes by Wednesday evening. The
ridge axis will slide offshore. Expect the high to nudge in for much
of the day and keep southern New England dry, but cloudy. Think
there could be some light precipitation that spreads in associated
with the warm front lifting through later on Wednesday into
Wednesday night. Better chances of precipitation on Thanksgiving as
the trough lifts into the eastern Great Lakes.
Still some uncertainty amongst guidance with respect to the speed
and amplitude of the wave lifting in. At this point in time it does
appear that the wave will be deamplifying as the trough lifts in.
The GFS, GEFS and EPS feature a more progressive system, whereas the
ECMWF/UKMET and CMC are slow and a bit more amplified. Regardless of
which camp the models fall in it does appear precipitation will be
all rain. Though there could be a brief rain/snow mix across the
higher elevations of western MA before changing over to all rain.
The slower solution would bring more in the way of rainfall as a
coastal low develops nearby/just south of the region. As with
yesterday have gone with the NBM due to differences at this point in
Have higher confidence in mild temperatures through this period and
it being a bit gusty late on Wednesday into Thursday with a 30 to 45
kt low level jet in place. Temperatures will be in the 40s across
the interior on Wednesday and the low to mid 50s across the south
and east coast. For Thanksgiving will have +8 to +10 degree Celsius
925 hPa overhead. This yields highs in the 50s across much of the
region. Though there will be a few spots across the south coast that
get into the low 60s.
Friday through Saturday...
Drier on Friday as high pressure builds in, but this may be brief.
Does appear that another trough may swing through on Saturday
bringing chances of precipitation. Confidence is low past Friday
given the differences in the mass fields, so have kept with the NBM
guidance. This keeps temperatures around normal with highs in the
mid 40s to mid 50s and chances of rain on Saturday.
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
MVFR conditions deteriorating to IFR and potentially some LIFR
as precipitation spreads in late in the night. E/SE winds
between 5-10 kts. Coastal locations may see gusts of 15-20 kts.
Did introduce low level wind shear at all of the interior
terminals as a 30-40 kt low level jet moves in and some places
remain decoupled per the RAP guidance, which is doing well based
on latest obs. Winds shifting to the S toward daybreak.
MVFR with IFR across the interior. May see spotty LIFR in areas
of heavier rainfall or where there is isolated thunder. Best
shot of isolated thunder across eastern CT into RI and eastern
MA. Have not added in the latest update, but will likely need to
be added in future TAF issuances. Turning drier and improving
to VFR with the wind shift to west, beginning 14Z-16Z western
MA/CT to 15Z-18Z eastern MA. W to NW winds will gusts up to
25-35 kt at times.
Monday night...High confidence.
VFR with dry weather, but gusty. Winds W to NW at 5-15 kts with
gusts of 20-35 kt. Expect the highest gusts over Cape Cod and
KBOS TAF...High confidence in TAF. Low prob of isolated thunder
12Z-16Z. Wind shift to the west 16Z-18Z Mon with gusts up to 30
KBDL TAF...High confidence in TAF. Wind shift to the west 14Z-
16Z Mon with gusts up to 30 kt.
Outlook /Tuesday through Friday/...
Tuesday: VFR. Windy with local gusts up to 30 kt.
Tuesday Night: VFR. Breezy.
Wednesday: Mainly VFR, with local MVFR possible. Breezy.
Wednesday Night through Thanksgiving Day: Mainly VFR, with
local IFR possible. Breezy. Chance SHRA.
Thursday Night: Mainly VFR, with local IFR possible. Slight
Friday: Mainly VFR, with local IFR possible.
Tonight...E wind becoming SE then S toward morning, 15-20 kt. Spotty
light rain/drizzle lowering vsby late.
Monday...south winds 15-20 kt with heavy showers and isolated
thunder until early afternoon. Then wind shift to the west with
passage of a cold front. Behind the front, WNW winds gusting up to
35 kt late in the day. Vsby 1-3 miles but improving with the wind
Monday night...WNW winds gusting up to 40 kt. Dry weather and good
Outlook /Tuesday through Friday/...
Tuesday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Rough seas up to 10 ft.
Tuesday Night: Winds less than 25 kt. Local rough seas.
Wednesday: Winds less than 25 kt. Areas of seas approaching
Wednesday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 25 kt. Seas up to 5 ft. Chance of rain
Thanksgiving Day: Winds less than 25 kt. Areas of rough seas.
Chance of rain showers.
Thursday Night: Winds less than 25 kt. Seas up to 5 ft. Chance
of rain showers.
Friday: Winds less than 25 kt. Seas up to 5 ft.
MARINE...Gale Warning from 2 PM Monday to 7 AM EST Tuesday for
Gale Warning from 4 PM Monday to 3 AM EST Tuesday for ANZ230-
Area Forecast Discussion
National Weather Service Caribou ME
1022 PM EST Sun Nov 22 2020
Low pressure will approach tonight and track across the state on
Monday. High pressure will build in Monday night into Tuesday and
crest over the area early Wednesday morning. The high will slide
east of the region Wednesday afternoon. Weak low pressure will cross
the area Wednesday night followed by high pressure Thursday into
.NEAR TERM /THROUGH MONDAY NIGHT/...
1020 PM Update...Starting to see snow reaching the sfc and the
column has moisten quickly across the northern and western
areas. Even seeing flurries here at the office in Caribou. The
HRRR and WRF doing fine w/the placement. Brought pops up and
brought snow a bit further s including Bangor initially given
the high to the ne wedging in w/the colder air in place.
Thinking attm after looking at the latest NAM soundings is that
colder air could hang in longer across the southern areas where
some light icing could occur, although attm, it looks to be
brief. Attm, snowfall and ice amts that are forecast look ok,
although midnight crew might need to make some adjustment if
temps hang in colder especially across the southern areas.
Decided to stay w/the current headlines that in place.
Sfc low wl continue to move northeast this aftn. High pressure
wl be building off into the Maritimes this evng with airmass
saturating in return flow. Pcpn wl mv into far nwrn zones aft
00z tonight and with wet bulb temps blo 0C expect snow at onset
and throughout most of the nighttime hrs.
LLJ kicks in twd 09z tonight with significant surge of warm air
aloft around H8 resulting mixed pcpn acrs central areas by 09z and
slowly spreading north through 13z. As warm air surges northward
there wl be a thin area of mixed pcpn including snow, sleet and
freezing rain before going to all rain as entire column warms above
0C drg the daylight hrs. Likewise, sfc temps wl fall through 06z
before beginning to rise.
Snow will be moderate at times drg the overnight near the sfc low as
it tracks into the Gulf of St. Lawrence. Pcpn wl then become
moderate-possibly heavy at times fm late mrng into the early aftn
hrs as occluded front comes thru.
All in all it appears that qpf amnts wl average around one inch with
all rain expected fm Bangor south twd the coast. Snowfall amnts to
the north of Baxter will average around 1 inch across the Central
Highlands into nern Aroostook. One to 3 inches of snow possible from
nrn Somerset twd Frenchville. A glaze of ice is possilbe acrs nrn
zones as mixed pcpn heads north in warm advection with amnts up twd
0.10 inches over the St. John Vly late morning. Due to uncertainty
of fzg rain potential hv not made any chgs to Winter Wx Advisory at
this time, though it may need to be expanded one tier of zones to
the south with later updates. For the time being will update the HWO
to mention potential.
.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
Low pressure exiting the area Monday evening will consolidate and
intensify as it lifts northeast through New Brunswick. A strong
gradient between the departing low and high pressure building down
from central Canada will bring a rapidly increasing and gusty
northwest wind overnight Monday night. A strong northwesterly
gradient both surface and aloft combined with cold advection will
result in strong gusty northwest winds on Tuesday. Gusts may reach
40 mph or more over the area during the day possibly resulting in
some isolated power outages. Tuesday evening will remain a bit
breezy, then winds will rapidly diminish late Tuesday night as
high pressure builds in and then, by early Wednesday morning,
crests over the area. This will bring a clear, calm and cold
morning Wednesday morning. High pressure will slide east of the
area Wednesday as a poorly organized low approaches from the
west. One low, tracking through central Canada, will be pulling
an occluded front east, linking to a secondary low over the
Great Lakes. Some light snow may spread into the area, mostly
western locations, late on Wednesday.
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
A bit of snow Wednesday evening will change to rain from south
to north as the occluded front pulls warmer air north ahead of
it. Rain will dissipate very late Wednesday night into Thursday
as the front slides east of the region. Weak high pressure will
build north of the area later Thursday into Friday. However,
some moisture lifting out of a broad longwave trough centered in
the west will bring a partly to mostly cloudy sky Friday as the
high slides across the north. Clouds will increase Friday night
as one low lifts north through east central Canada, connecting
to another low in the Tennessee Valley supported by a southern
branch trough. Weak high pressure returning to the north will
slow the progress of the southern branch low Saturday into
Saturday night. The low should finally lift northeast Sunday or
Monday bringing rain, or snow changing rain, and wind as it
lifts up to our northwest.
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
NEAR TERM: VFR expected through this evening before diminishing
to MVFR/IFR after 06z in low clouds. Light snow will break out
after 08z at KFVE and after 07z at KCAR, KPQI and KHUL.
-FZRASNPL will likely mix in after 10z at HUL and progressing
north after this time. All rain expected early morning through
end of TAF valid time.
Downeast terminals likely to see IFR in -ra after 10z Mon. LLWS
will affect all terminals after 10z with FL020 from the SE
between 40-50kts until cdfnt moves through after the end of the
Monday night: IFR, becoming VFR Downeast and MVFR across the north.
Winds becoming strong and gusty out of the NW.
Tuesday: VFR. Strong gusty NW winds.
Tuesday night: VFR. Gusty NW winds, becoming calm late.
Wednesday: VFR, becoming MVFR. Winds calm becoming SE.
Wednesday night: MVFR lowering to IFR. S wind, becoming NE across
Thursday: IFR becoming MVFR, and possibly VFR N. NE winds.
Thursday night: MVFR. Light NE winds.
Friday: MVFR. SE winds.
NEAR TERM: Wind will be on the increase from the southeast after
midnight tonight with gale force winds expected. Expect a brief
lull as the boundary moves over the waters in the afternoon but
cold advection wl bring gale force winds back to the waters
after the near term pd. Seas will increase above 5ft late
tonight and remain elevated through the day on Monday.
SHORT TERM: Gales will continue Monday night into Tuesday for
strong gusty NW winds. The winds will quickly diminish late
Tuesday night and be tranquil Wednesday morning. A SCA may be
needed Wednesday night for S winds gusting up to 25 kt. Winds
should be below SCA Thursday into the start of the weekend.
ME...Winter Weather Advisory until noon EST Monday for MEZ001-003-
Wind Advisory from 6 AM to 4 PM EST Monday for MEZ029-030.
MARINE...Gale Warning from 5 AM Monday to 4 PM EST Tuesday for
Area Forecast Discussion
National Weather Service Green Bay WI
522 PM CST Sun Nov 22 2020
Updated aviation portion for 00Z TAF issuance
Issued at 219 PM CST Sun Nov 22 2020
A round of snow Tuesday--changing to a wintry mix across much of
the area Tuesday night, and a rain/snow mix and then mainly rain
across east-central Wisconsin. Quiet weather is expected from
Thanksgiving Day through most of the holiday weekend.
The upper flow across North America will be slowly progressive as
a series of shortwaves migrate across the CONUS during the
period. The main westerlies will split and then phase back
together at times--making it difficulty to reliably add detail
to the later periods of the forecast.
The pattern will allow some Gulf moisture to be transported into
the region, so the total precipitation for the period will range
from near normal across the NW part of the area to above normal
elsewhere. Temperatures will be near normal tomorrow, then
modestly above normal for the rest of the time.
.SHORT TERM...Tonight and Monday
Issued at 219 PM CST Sun Nov 22 2020
The latest RAP analysis and satellite/radar imagery show shortwave
energy and a surface troughing moving east across the northern
Mississippi Valley and western Wisconsin early this afternoon.
Snow showers along the trough have been dissipating as the move
east due to ample dry air in the mid-levels, as shown on the KGRB
12z sounding. Scattered light snow showers, possibly mixed with
rain over eastern WI, remain expected to move east across the area
during the afternoon. Perhaps a few tenths of snow accumulations
will be possible over north-central WI where temps are colder, but
accumulations will likely be confined to grassy surfaces. Forecast
concerns continue to revolve around precip trends, and if any
impacts on travel could occur.
Tonight...The trough of low pressure will slowly weaken as it
moves across northeast Wisconsin during the evening. A narrow
moisture channel will provide the highest chance of light rain and
snow over northeast Wisconsin, but forecast soundings indicate
that spotty drizzle/sprinkles could persist over much of the area
for a few hours into the evening. Based on obs upstream,
visibilities remain relatively high so it appears doubtful that
any drizzle or freezing drizzle will lead to travel difficulties. As
the trough exits, light snow showers will likely continue over the
snowbelt of far north-central WI overnight, while central to
northeast WI could see clearing take place late. With ample cloud
cover and a brisk northwest wind, don`t see temps falling much
tonight. Lows ranging from the lower 20s over central WI to the
lower 30s near the lake.
Monday...Cyclonic flow will gradually abate as a surface ridge
axis moves from the west. Northwest flow over north-central WI
will subside in the process, and therefore should see decreasing
clouds through the day. Elsewhere, partly to mostly sunny skies
are anticipated. High temperatures will mostly range from the low
to middle 30s.
.LONG TERM...Monday Night Through Sunday
Issued at 219 PM CST Sun Nov 22 2020
Temperatures Monday night could drop quickly under mostly clear
skies and light winds, but some recovery should occur later in
the night as clouds arrive.
A full-latitude trough that was coming ashore along the West Coast
today will progress east across the country during the next
several days. The wave will tend to split as the main westerlies
undergo at least some separation into northern and southern
streams, with the northern piece of energy progressing slightly
faster. Forcing with the system is still expected to be sufficient
to bring a substantial round of precipitation to the area,
especially give an expected influx of Gulf moisture. Timing has
slowed a bit since yesterday, and a little additional slowing is
possible. That should allow most of the area to get through the
Tuesday morning commute before the snow begins to accumulate. The
initial slug of precipitation will continue across the area
Tuesday and should be mainly snow everywhere except possibly right
along the Lake Michigan shoreline where boundary layer
temperatures will probably support a mix.
The details of the precipitation forecast rapidly become fuzzy
after Tuesday as the splitting of the upper support starts to
result in differences among the models. A warm layer aloft will
likely arrive late Tuesday/Tuesday evening across the S/SE part
of the area, resulting in a transition to a mix and then mainly
rain (especially in east-central Wisconsin). The north will
remain colder, but may lose mid-level moisture and have
precipitation change to FZDZ at times. At least occasional
precipitation will probably linger over east-central Wisconsin
Wednesday and into Wednesday night as the southern stream portion
of the shortwave closes off and a vertically stacked cyclone
tracks into southern Lower Michigan. Thermal profiles will
probably continue to favor mainly rain in E-C WI. The NW part of
the area will probably be in the col in the upper wind flow, so
other than perhaps a little lingering light DZ/FZDZ not much
precipitation is expected there after midnight Wednesday.
Quiet weather is expected for Thanksgiving Day at least into
Sunday. The medium range models continue to suggest there is the
potential for a significant storm system to affect the area at
the very end of the forecast period or shortly thereafter. But the
track and intensity of that system will depend on if/when/how
much phasing of the streams occurs, so it is likely to remain a
highly uncertain aspect of the forecast for at least a few more
.AVIATION...for 00Z TAF Issuance
Issued at 521 PM CST Sun Nov 22 2020
A trough of low pressure will move across the region this
evening. This trough will bring scattered rain and snow showers
that will drop vsbys to MVFR occasionally, mainly over central and
north-central WI. Cigs will also likely fall to MVFR and IFR at
times this evening at most locations. The light precip will pull
out later this evening except for the Vilas county snow belt,
where light snow showers and flurries could persist through the
overnight hours. Clouds will likely erode late tonight into Monday
morning with cigs lifting. VFR conditions are then expected
through Monday afternoon once the clouds clear out.
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1001 PM EST Sun Nov 22 2020
A cold front with limited moisture will cross our region from the
northwest early Monday. A cold front with more moisture is expected
to move through the area during the middle of the week. The active
pattern continues as low pressure and a cold front is expected to
cross the southeastern states next weekend.
.NEAR TERM /THROUGH MONDAY/...
As of 950 PM: A cold front is encroaching on the NC mountains
attm; obs across the Cumberland Plateau and portions of East
TN are now gusty and northwesterly. A band of light to moderate
rain accompanies the front. Although a modest amount of DPVA is
progged to cross the CWA with the front tonight, the majority
of the moisture seems to be eaten up by the mountains; the HRRR
in particular depicts this, and it seems to have initialized
well. Revised PoPs feature slightly more rain shadowing, keeping
more areas dry east of the mtn spine. The HRRR seems to be doing
better than the NAMNest so far, and the former ends the precip
earlier, too. Temps look to remain somewhat elevated beneath the
cloud cover, until the fropa occurs; these trends have also been
updated. For the high elevations this will bring temps down near
freezing. It is now looking still more likely the precip will
end before changing to snow. Even if it were able to change over,
SLRs would be small due to shallow moisture.
Areas south and east of Charlotte still look likely to see some
fog form in the next couple hours, where not already present, due
to the saturated boundary layer lingering after the earlier light
precip. The fog may advect into some areas that didn`t see precip,
but likely will dissipate before the morning commute as the front
After the full fropa occurs early in the morning, expect
post-frontal conditions with bright blue skies for the rest of the
near-term as cooler, drier air slowly filters into the region. Winds
will be breezy, especially near the Blue Ridge Escarpment, but
well below advisory criteria. Max Ts will be around or slightly
below-climo on Monday.
.SHORT TERM /MONDAY NIGHT THROUGH THURSDAY/...
As of 135 PM Sunday: Full latitude upper ridge axis briefly moves
over the area Tuesday. The axis moves east Wednesday as an upper low
moves into the OH River valley. There is some phasing with this low
and a short wave over Canada as the associated trough axis crosses
the area Wednesday night. Short wave ridge moves in behind this
system on Thanksgiving Day. At the surface, a cold air mass
associated with high pressure centered to our north moderates by
Wednesday as the center of the high moves off the New England coast
and a warm, moist southerly flow develops. Moisture deepens and
forcing increases Wednesday afternoon into the evening as an
associated cold front moves into the area. There`s also good low
level isentropic lift and upper divergence. Precip develops along
and west of the Blue Ridge first then spreads east across the area
through the evening. Precip then tapers off Wednesday night as the
forcing and front move east of the area. Little in the way of
instability with this system, so no thunderstorms expected. Doesn`t
look like any heavy precip expected with moderate QPF over the
mountains and Blue Ridge with mainly light QPF elsewhere. Should be
warm and dry on Thanksgiving Day as a dry but moderate air mass
Lows and highs 5 to 10 degrees below normal Tuesday rise to 5 to 10
degrees above normal for Thanksgiving Day.
.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
As of 240 PM Sunday: Uncertainty remains high in the long term as
models continue to have difficulty resolving the developing split
upper flow and resulting surface patterns. The GFS shows an
initially phased system becoming un-phased, then the southern stream
phases with a second northern stream wave by the end of the period.
The ECMWF shows a closed low developing over the Southern Plains as
the initial northern wave moves east. This low then phases with a
second northern stream short wave as it moves into the MS valley.
At the surface, the GFS shows a faster weaker cold front moving
into the area Saturday and moving to our east Sunday as the phasing
takes place. The ECMWF has a strong low pressure system and cold
front crossing the MS valley on Sunday. The GFS would suggest precip
developing late Friday, containing through Saturday, then drying on
Sunday. The ECMWF has a dry Friday, maybe some light precip on
Saturday, and a wet Sunday. The GFS ensemble mean seems to favor its
operational run, while the Canadian favors the ECMWF. Given the
differences and low confidence, have trended toward the guidance
blend, but kept any PoP below 50 percent. Show lows remaining above
normal through the period with highs above normal Friday then
falling slowly to near normal by Sunday.ht
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
Overall: Abundant cirrus already cover the region ahead of an
approaching shortwave; nearer the attendant cold front, low VFR cigs
are beginning to fill in as midlevel moisture increases. The front
will bring precip mainly to the higher mtn elevations overnight;
KAVL may see some cigs possibly down to MVFR, but the small
chance of precip only warrants VCSH. The front will scour out low
clouds in the morning, leaving mostly SKC for the remainder of the
period. Winds will turn NW and gusty across the region following
fropa, likely before dawn at all the TAF sites.
At KCLT: Prefrontal convergence continues to drive -SHRA SE of KCLT;
these likely will continue to track just east of the field. Cigs
are rapidly lowering beneath them, such that areas of IFR to LIFR
are likely thru the evening. With precip unlikely to actually reach
KCLT, there remains the possibility that some of those cigs will
advect in later this evening. This has prompted prevailing MVFR
and TEMPO LIFR.
Outlook: Dry weather expected Tuesday, while increasing clouds and
better rain chances enter the region Wednesday into Thursday with
next fropa. Unsettled weather could continue after that as we go
into the upcoming weekend.
03-09Z 09-15Z 15-21Z 21-00Z
KCLT Med 78% High 86% High 100% High 100%
KGSP High 100% High 100% High 100% High 100%
KAVL High 100% Med 68% High 88% High 100%
KHKY High 100% High 100% High 100% High 100%
KGMU High 100% High 100% High 100% High 100%
KAND High 100% High 86% High 100% High 100%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables are available at
the following link:
Area Forecast Discussion
National Weather Service Louisville KY
943 PM EST Sun Nov 22 2020
Issued at 943 PM EST Sun Nov 22 2020
Surface cold front is just about to exit the state of Kentucky this
evening. In its wake, low cloudiness extends back to near the I-65
corridor. Under the clouds, temperatures have dropped into the
lower 40s. Skies are scouring out nicely out to our west with the
clearing line nearing the I-65 corridor. This clearing line should
continue eastward through the remainder of the overnight hours.
Where skies have already cleared, temperatures have dropped into the
upper 30s across far western KY.
For the overnight period, we anticipate skies slowly clearing from
west to east. I think we`ll get a little more cloud cover moving
back over southern IN later this evening, but that should mostly
clear out by sunrise. Some patchy fog will be possible later
tonight where skies clear out. Overnight lows dropping into the 32-
38 degree range still look on target.
Overall, forecast remains on track. Have made some slight edits to
the cloud cover forecast to better align with current IR satellite
imagery. Updated products will be available shortly.
.Short Term...(This evening through Monday)
Issued at 243 PM EST Sun Nov 22 2020
Latest surface analysis places the surface low center between
Cincinnati and Columbus, OH with the cold front stretching SW along
the OH River before dipping more southward between HNB and SDF and
just west of BWG. Radar continues to show light rain and drizzle
along and ahead of the front with rainfall totals so far amounting
to around 0.20" north of the OH River and generally less than 0.15"
across KY. Quite the temperature drop behind the front with readings
behind the front in southern Indiana in the low 40s and mid to upper
50s ahead of the front across much of central and eastern KY. Winds
are also picking up just ahead of and behind the front with KY
Mesonet showing gusts in the 20-25mph range across much of the area.
Latest hi-res guidance pushes the bulk of the rain associated with
the front out of our eastern counties by around 23/00Z, but RAP
model soundings continue to show potential drizzle for a couple of
hours behind FROPA. Expect to see lingering low clouds through the
overnight period and into most of the morning, especially along and
east of I-65, until dry air aloft is able to mix down Monday
afternoon. Did add mention of patchy fog across portions of our
western CWA that could result from early clearing overnight, but
variable cloudiness should keep any widespread dense fog from
With that said, expect Monday to start off cloudy with morning min
temps bottoming out in the low to mid 30s. Lingering cloud cover
could delay diurnal warming a bit, so decided to back off of max
temps a bit with highs in the upper 40s across southern Indiana and
in the low 50s across the Commonwealth. But again, do expect most to
see some sunshine at some point Monday afternoon as high pressure
builds in across the region.
.Long Term...(Monday night through Sunday)
Issued at 245 PM EST Sun Nov 22 2020
Quiet wx expected Mon night and Tue under shortwave upper ridging.
Developing southerly flow on the back side of sfc high pressure will
allow Tuesday highs to climb just above normal even in the face of
increasing cloud cover.
By Tuesday night southerly flow develops through a deepening layer
ahead of strong low pressure over the Plains. We`ll stay dry through
the evening, but expect precip chances to ramp up before daybreak
Wednesday, especially west of Interstate 65 as a strengthening low-
level jet edges closer.
The low will be vertically stacked but still fairly potent as it
tracks across northern Illinois and Indiana on Wednesday. Low-level
jet cranks up to 60-65 kt, so gusty winds are a good bet. What is
more uncertain is any severe wx potential, as it will be a strongly
sheared sounding with long and looping hodographs, but little or no
sfc-based instability. Will not play up the severe threat just yet,
as surface-based storms still appear unlikely, but this bears
watching over subsequent forecast cycles. Have gone with categorical
POPs on Wednesday, but this system is progressive enough that QPF
will average a half to less than 1 inch.
Thanksgiving Day looks dry with seasonable temperatures, but beyond
Friday model solutions start to diverge a bit. Split flow will set
up, and the pattern will eventually amplify an upper trof over the
eastern CONUS, but sensible wx and timing will both depend on the
degree of phasing between the northern and southern streams. ECMWF
is more phased, and therefore slower and potentially colder, while
the GFS is more progressive with less phasing between the streams.
Bottom line is we will have a system this weekend, but the timing
and nature of that are in doubt. Will carry chance POPs both Sat-
Sun, and those will likely increase as we narrow down the time
period. All of the significant precipitation will be rain, though
that could prove to be quite a cold rain if the more amplified
solution verifies. There will be mention of rain/snow mix for parts
of the area Sat night/Sun morning, but any flip to snow would mean
the environment supports less QPF, so little or no impact is
.Aviation...(00Z TAF Issuance)
Issued at 555 PM EST Sun Nov 22 2020
Surface low continues to push off to the northeast while surface
cold front continues to move eastward across eastern Kentucky. In
the post frontal wake, low clouds will remain in place even though
drier is working in. We`ll see the cloud continue into the
overnight hours as the moisture remains trapped under a temperature
inversion. Latest guidance is a little more optimistic on these low
clouds mixing out late tonight, so have cautiously trended the
forecasts in that direction. Depending on how much clearing takes
place, fog could be an issue as well. Current guidance suggests
that KHNB/KLEX would have the best threats of at least some MVFR fog
overnight (23/08-12Z roughly). After 23/12-13Z, VFR conditions are
expected for the remainder of the TAF period.
Winds this evening will remain out of the west/northwest and will be
gusty at times. We expect the winds to diminish towards late
evening and overnight. Winds look to veer back to the west and
southwest for Monday.
Area Forecast Discussion
National Weather Service Memphis TN
815 PM CST Sun Nov 22 2020
.DISCUSSION...02Z Surface analysis places a cold front from East
Tennessee back through Northern Alabama and into Central
Mississippi. Rain ended just before sunset and GOES-16 satellite
trends indicate post frontal stratus quickly pushing to the south
with clearing skies north of I-40 thus far. Will be doing another
update to decrease cloud cover more rapidly for the remainder of
the night and make a few minor adjustments to temperatures.
Updated grids will be published shortly.
.PREV DISCUSSION... /issued 613 PM CST Sun Nov 22 2020/
See aviation discussion below.
PREV DISCUSSION... /issued 332 PM CST Sun Nov 22 2020/
A more typically progressive late November weather pattern has
returned, after a recent extended dry period. Active pattern
notwithstanding, dry and mild conditions appear on track for
For the short term, a cold front and accompanying showers will
exit northeast MS through late afternoon, as an upper trof over
the Ozarks lifts to the lower/mid MS River valley. Primary short
term forecast concern will be cloud trends, which will impact
overnight temperatures and fog potential. NAM and RAP soundings
concur with HRRR ceiling progs showing a complete dissipation of
of low clouds overnight at all but northeast MS. GOES East visible
imagery showed developing breaks in the low clouds over east
central AR and southern MO. Post-frontal cool season stratus
often persist for days over the Midsouth, but it appears that
sufficient drying will occur in the lowest 2kft for some clear
spots to develop, and perhaps expand even after sunset. Official
grids won`t go full clear as NBM and and short blends suggest, but
will reflect some clearing and patchy fog.
Fair weather will prevail Monday, under low amplitude ridging. By
Tuesday morning, an upper low will drop into the 4-corners
region. A low level warm sector will develop over the southern
plains and translate east with the the deepening upper low. By
midnight Tuesday night, the upper low will lift into northeast KS.
An associated surface cold front will likely hang across the
western Ozarks, until a shortwave trof ejects through the Ozarks
early Wednesday morning, taking the front east with it. For the
Midsouth, prefrontal elevated showers and thunderstorms are
expected late Wednesday evening, mainly along and west of the MS
River. GFS depicts only modest 0-1km MUCAPE of 200 J/KG at 9Z/3 AM.
This narrow band of instability will lift east of the MS River
after sunrise Wednesday, along and ahead of the cold. A post
sunrise bump MUCAPE to around 750 J/KG may develop over northeast
MS (beyond the SPC Day 3 outlook period) suggestive of some strong
Rain should exit the TN River valley by late Wednesday afternoon,
with fair conditions prevailing Thanksgiving Day. Expect some
increase in high clouds during the day, in advance of the next
rain event on Friday. Model timing with this next system remains a
bit scattered, due to its potential to cut-off from the main
westerlies. The main take-away is that unsettled weather will be
possible over the Midsouth through the upcoming weekend. As we get
closer in time, model consensus should improve, helping to better
pinpoint weekend rain timing.
Expect MVFR conditions to prevail through the early
evening hours. Some improvement is expected throughout the
overnight hours and we should be mostly VFR by daybreak at all
sites. Winds will shift to the north, but should diminish over the
next few hours.
Area Forecast Discussion
National Weather Service Marquette MI
645 PM EST Sun Nov 22 2020
.SHORT TERM...(This evening through Monday)
Issued at 319 PM EST SUN NOV 22 2020
Latest satellite imagery at 1930Z shows the slowly rotating upper
low over NW Wisconsin. At the surface, the surface trough boundary
is approximately near the Wisconsin and Upper Peninsula of MI
border. MSAS analysis has the surface cold front draped from
International Falls, WI southward to Sioux Falls, SD. The frontal
boundary will slowly propagate toward the CWA as the afternoon and
evening progresses. Surface obs are showing a gradual transition
from BKN to OVC skies from Ironwood earlier this morning eastward
toward the rest of the CWA, with snow showers also occurring there.
Radar is beginning to get scans of the snow showers slowly to the
northeast the last couple of hours. Temperatures have been hovering
around the freezing mark or slightly below that threshold.
As the broad swath of precip continues to move east, it is lightly
to have a rain/snow mix and/or become light rain showers from MQT
eastward due to the lowest layer of the atmosphere having a greater
than 2Kft warm layer above freezing and melting the frozen precip to
liquid. BUFKIT soundings show that after 0Z tonight, the column
begins to dry out for CMX/IWD/MQT, with MQT having slightly
moistened layer to about 3Z. From this point, CAA from the upper and
mid-level of the atmosphere will certainly help keep the area below
freezing overnight, but there will also be dry air infiltrating into
the area. Northwest winds will begin to ramp up overnight,
especially over the marine areas of Lake Superior with gusts over 30
knots possible, 15 to 25 knots over land. While there may be dry air
aloft, Hi-Res guidance from the HRRR is hinting at surface
convergence of winds over the Lake Nipigon area overnight with a
potential snow band developing and reaching the northwest snowbelt
areas of Keweenaw and Marquette Counties causing potential
orographic terrain enhancement. Snowfall totals over the area look
to be minimal however, with amounts in the 1-2 inch range at most
over the CWA. It is possible to have a stray 3 inch report over the
higher terrain of Marquette/Baraga counties. The potential for light
snow showers to continue after 18Z Monday looks pretty low at this
time of inspection due to the lowest 100-200mb of the atmosphere
drying out through the column.
A secondary cold front will propagate over the region between 18Z
and 0Z Monday afternoon. This will keep temperatures on the chilly
side where temps will likely decrease as the afternoon progresses
behind the surface cold front. The sky coverage will decrease from
southwest to northeast by late Monday afternoon. Winds should
dissipate from west to east by afternoon as well across the CWA
where winds will be 10 knots or less by sunset over land.
.LONG TERM...(Monday night through Sunday)
Issued at 248 PM EST SUN NOV 22 2020
Outside of a nuisance snow event Tuesday afternoon/evening...the
remainder of Thanksgiving week looks extraordinarily tranquil with
temperatures continuing to average a few degrees above normal.
Surface ridge axis will move across the Upper Lakes Monday night
with a seasonably cold night expected. Trends continue of northern
and southern stream energy phasing looking less and less likely for
Tuesday. Better dynamics with northern stream shortwave will stay
primarily just north of the area. Warm advection ahead of stronger
southern stream system will be the main precipitation driver across
the U.P. Tuesday afternoon through the evening. Total QPF amounts of
just under .20 inches are expected far west and Keweenaw to perhaps
as high as .40 inches over southern Menominee county. This will
yield 1-3 inches of sloppy slushy snow inland away from the Lakes.
GFS continues to show enough warming Tuesday evening to change all
precipitation to some light rain as the precipitation winds down.
Temperatures will stay steady or even rise a few degrees Tuesday
night. Any lingering light rain/snow mix will move out of the
eastern U.P. Wednesday morning.
Surface ridging will build over the Upper Lakes by late Wednesday
through Thanksgiving day. Another shortwave/weak front will move
across the area on Friday but with no appreciable moisture to work
with not anticipating any precipitation.
Extended models are trying to come in agreement with a brief surge
of cold air by the end of next weekend which could temporarily
invigorate the lake effect machine. But after that...the pattern
looks to return right back to zonal flow with mild temperatures and
minimal precipitation chances especially for early December
With only 5.1 inches of snow measured thus far this November at our
office...a top ten least snowy November is still within reach.
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 630 PM EST SUN NOV 22 2020
IFR conditions at KIWD and KCMX in light -shsn early this evening
should improve to MVFR late evening/overnight and then to VFR Mon
afternoon as high pressure and associated drier air move in from
the west. MVFR conditions will persist at KSAW through much of the
fcst period in a developing nw-n flow. Winds will become gusty to
around 23-28 knots tonight at CMX and IWD, with the highest gusts
at KCMX due to local terrain influences. Wind gusts will increase
above 20 knots by late tonight/Mon morning at SAW. Winds will then
slowly diminish from west to east during the day on Monday as high
pressure builds in from the west.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 319 PM EST SUN NOV 22 2020
A slow moving cold front will make its way over the lake tonight
bringing NW gusts up to 32 kts tonight into Monday morning. A few
gale force gusts will be possible over the eastern half of the lake
at times. Winds will dissipate through the remainder of Monday. A
new surface low pressure developing over the great Plains of the
U.S. will move toward the region by late Tuesday. A few marginal
gale force gusts to 35 knots will be possible across the east half
of the lake late Tuesday. Winds will diminish back to 20 kts or less
for Wednesday and Thursday behind the departing surface low.
Area Forecast Discussion
National Weather Service Topeka KS
454 PM CST Sun Nov 22 2020
Issued at 338 PM CST Sun Nov 22 2020
Early this afternoon an upper level trough was located along the
norther and central MS River Valley. Eastern KS was on the west side
of the upper trough axis, with stronger isentropic downglide
which has shifted the cloud cover from this morning, east into MO
and southeast KS. The insolation was helping temperatures to warm
into the mid 50s this afternoon.
A low amplitude trough embedded within the southern stream of the mid
level jet across southern CA will be kicked, by a more
amplified upper level trough digging southeast onto
Pacific northwest and northern CA coastline, northeast
into the central Plains on Monday. A lee surface trough will deepen
across the high plains Tonight as a surface ridge of high pressure
over northeast KS this evening will shift east into MO. Overnight
lows will occur from midnight to around 4 AM with temperatures
slowly rising through the 30s due to the surface winds becoming
southerly across the CWA, along with increasing cloud cover due to
weak WAA and DCVA ahead of the minor H5 trough lifting northeast
across the central high Plains. A few numerical models show there
may be enough ascent along with residual moisture return for light
rain or light snow mixed with rain to develop across north
central KS between 6 AM and 9 AM. By the time the light precip
reaches northeast and east central KS, surface temperatures should
be warm enough for light rain. Several of the CAMs shift the weak
H5 trough northeast across the central Plains and the better
ascent ahead of the H5 trough and isentropic lift will shift
northeast across northeast KS and northwest MO by afternoon. Much
of the CWA may see a break in the rainfall during the afternoon
hours. The cloud cover with periods of light rain will keep high
temperatures on Monday in the mid to upper 40s.
Monday night, the amplified H5 trough along the western US
coastline will dig into the southwestern US. The stronger
southwest mid-level flow across the Rockies will cause a deeper
lee surface low to develop along the CO/KS border along with a
deeper 850mb low across western KS. The strong 850m flow of 40 to
50 KTS will advect richer Gulf moisture northward across the
Plains. The resulting isentropic lift will cause widespread
showers and perhaps a few elevated thunderstorms to develop. Low
temperatures in the upper 30s to mid 40s will occur during the
early evening hours with temperatures rising through the 40s
overnight due to the stronger WAA.
Tuesday, the amplified upper level trough across the southwestern US
will move east across the Plains Tuesday night. Stronger DCVA ahead
of the upper trough combined with isentropic lift and richer
moisture transport will cause widespread showers and scattered elevated
thunderstorms to develop. If MUCAPES approach or exceed 500 J/KG,
then a few of the storms may produce small hail with some hail
reaching over quarter size with any type of mid-level storm
rotation. The surface based storms will remain south of the CWA
across southeast KS and eastern OK, which will spread northeast
into western MO and AR through the evening hours.
Tuesday night through Wednesday, as the H5 trough axis shifts east
across the state of KS, the surface cold front will move east across
the CWA dropping temperatures into the 30s during the evening hours.
The ECMWF and NAM show a TROWAL developing within the deformation
zone on the northwest side of the amplifying trough, which may
become a closed upper low across northeast KS as it shifts northeast
across northwest MO. If the TROWAL develops along the NE/KS
border, then there may be a period of accumulating snowfall
across the northern counties of the CWA through the morning hours
of Wednesday. The GFS solutions does not show a TROWAL developing
and is less amplified with the upper low. As the upper low shifts
east-northeast into northern IL by afternoon, stronger isentropic
downglide should clear skies from southwest to northeast across
the CWA. the southern counties may see more insolation through the
afternoon hours and highs may reach the lower 50s, while the
northeast counties will hold on to the clouds longer with highs
only in the mid 40s.
Thursday (Thanksgiving), looks mild and dry as an upper ridge shifts
from the Plains into the east central US. An upper level trough will
move onshore across the western US and dig southeast into the
Southwestern US. The northern stream branch of the H5 trough will
move east into the northern high plains. Skies will be mostly
sunny with highs in the mid to upper 50s.
Thursday night through Friday night, the northern branch upper level
trough will move east across the northern Plains Thursday night. The
resulting low-level CAA will cause a surface front to push
southward across the CWA late Thursday night into Friday morning.
Northerly winds will drop temperatures back into the upper 40s to
lower 50s. On Friday, a surface ridge of high pressure will build
southward across KS. The southern stream H5 trough across the
southwestern US will amplify into a closed upper low as if shifts
east into the southern high plains. At this time any precipitation
will remain well south and southwest of the CWA.
Saturday through Sunday, The 00Z run of the ECMWF kept the upper low
well south across TX but the 12Z run lifts the upper low east-northeast
across OK into south-central MO, much like the solution from 24
hours ago. If the 12Z ECMWF were to verify light rain would
develop Saturday evening and as the upper low moves east-
northeast across OK, vertical temperature profiles would cool
enough through the night for the rain to change over to snow, and
the snow may continue into Sunday. Based on the 12Z ECMWF track
of the upper low, the best chance for measurable snowfall would be
along and southeast of the KS turnpike. The 12Z Canadian model is
in good agreement with the 12Z ECMWF.
There still remains a lot of uncertainty with how the upper low will
develop over time and its track. The GFS keeps a positive tilt H5
trough across the center of the country with no amplification of
the southern stream trough. If the GFS solution were to verify it
would lead to a dry and cool forecast. Highs on Saturday will
probably reach the upper 40s to lower 50s. Highs on Sunday may be
in the 30s if the ECMWF and Canadian model solutions verify. If
the GFS verifies then highs on Sunday will once again be in the
upper 40s to lower 50s.
Stay tuned to the latest forecast since Sunday is usually a high
volume travel day to end the Thanksgiving Day weekend.
.AVIATION...(For the 00Z TAFS through 00Z Tuesday)
Issued at 454 PM CST Sun Nov 22 2020
Increasing warm air and moisture advection is expected to bring
some mid level clouds over the terminals late tonight. RAP forecast
soundings show quite a bit of low level dry air through a good
portion of the day, so CIGS are forecast to remain VFR. Models
showing some QPF developing by the late morning. Given the dry
layer around 850MB, any precip may be more along the lines of
sprinkles. So may only mention of VCSH for now with any precip
causing minimal impact.