Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/10/21
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
500 PM MST Tue Feb 9 2021
00Z TAF CYCLE
Breezy to locally windy conditions are in progress, but gusts should
subside shortly after dusk in most locations. Much like yesterday
afternoon, VFR conditions have returned to all of northern and
central New Mexico as low stratus clouds and fog (associated with
the Arctic front) have retreated. However, these low clouds and
freezing fog are expected to re-enter northeastern parts of the state
this evening, spreading over much of far eastern New Mexico toward
dawn Wednesday where IFR to VLIFR conditions are expected. Conditions
will improve in eastern New Mexico through the late morning and
early afternoon when moderate breezes will redevelop across much of
the state. Localized areas near and immediately east of the central
mountains could observe stronger wind speeds with gusts to 25 to 30
.PREV DISCUSSION...323 PM MST Tue Feb 9 2021...
Westerly breezes will subside this evening, and the cold front draped
across northeast New Mexico will slide back to the south and west a
bit. Freezing fog will again be likely across northeast NM overnight
behind the front. This front will slide a bit more to the south and
west each day, with nightly rounds of freezing fog behind it,
before finally plowing through the state on Saturday. Bitterly cold
temperatures and even more bitter wind chills are likely through the
weekend. Easterly gap winds are also expected in the Rio Grande
Valley Saturday night with gusts up to 50 mph. Valentines Day will be
a good day to stay inside and snuggle as it will be the coldest day
of the next week.
SHORT TERM...(TONIGHT THROUGH WEDNESDAY NIGHT)...
West winds haven`t been as strong this afternoon as in the last
couple of days. Combined with the increasing high clouds, this has
helped keep temperatures a few degrees cooler than at this time
yesterday. Also, the low clouds have been stubbornly hanging on over
the far eastern side of Union county where the temperature hasn`t
yet warmed above freezing today. There is quite a contrast between
the current temperature at Raton, at 61 and Clayton at 26. The
latest HRRR weakly suggests there could be a brief break in the low
clouds later this afternoon before they return this evening. In
fact, low clouds and fog/freezing fog may become more widespread
farther west tonight, as an upper trough approaches NM from the
west. Not betting the increasing high clouds associated with the
trough will have much of an impact in the areal coverage of low
clouds/fog/freezing fog tonight, which is reflected in tonight`s and
Wed morning weather grids. Guidance hasn`t been cold enough with
lows near the TX border and have again gone a bit colder for
tonight. Pretty much a repeat performance expected for Wednesday
night, although the low clouds, fog and freezing fog could make it
close to a line from Raton to Las Vegas, Clines Corners and Roswell
late night as the upper trough passes overhead. There may be a few
snow showers over the northern peaks, as well as the Gila thanks to
the trough but not expected to be much of an event.
Highs Wednesday will be several degrees cooler, but still mostly
warmer than normal. The exception will be portions of the Northeast
and East Central Plains where the colder air remains anchored.
LONG TERM...(THURSDAY THROUGH TUESDAY)...
All eyes remain focused on the arctic airmass and its progression
through much of the extended forecast. A dry upper level trough is
still expected to cross the state on Thursday with little change to
our sensible weather. The front is expected to linger across
northeast NM Thursday afternoon. As has been the case, the front
should diurnally slosh back westward Thursday night with freezing fog
possible once again behind it. It`s likely it will get a little
further west than the nights before. On Friday, an upper level trough
will approach from the west, increasing westerly flow aloft and
inducing a lee side low to the east of the Sangre de Cristo Mtns.
This will help to push the front back eastward with flow becoming
southwesterly at the surface, but it`s likely the front will still
be this side of the NM/TX border by the afternoon hours.
Additionally, the lift associated with the upper level trough
combined with a weak influx of Pacific moisture, should result in
light snow across northern and western NM Friday afternoon and early
evening. The trough will quickly pass overhead Friday night, ending
any remaining snow.
By Saturday morning, a reinforcing shot of arctic air will shift into
eastern NM. The front is expected to make it to the Central Mountain
Chain by mid day, push through the gaps of the Central Mountain
Chain by early evening, and reach the ContDvd by early Sunday
morning. With a 1050mb sfc high over NE MT, this will be some of the
coldest February air and linger the longest since the Big Chill of
February 2011. Areas along the OK and TX borders may stay below the
freezing mark Friday night through Tuesday morning. Making matters
worse will be the winds. Though the strongest winds are expected in
the Rio Grande Valley below gaps, where gusts may reach 45-50 mph,
any wind will make it feel colder. The lowest wind chills are
expected Sunday morning where readings of -10 to -20 will be possible
across the east, and wind chill readings as low as 0 will be
possible in the ABQ Metro Area. All-in-all, this weekend through
Monday will be very cold and a good time to stay inside. Right now is
a good time to prepare for the cold, including protecting pipes and
making arrangements for outdoor pets to have a warm shelter with
Last but certainly not least, another, more potent, upper level storm
system will approach and cross the state on Sunday. Abundant moisture
and lift should result in widespread snow Sunday and Sunday night.
Given the cold temperatures, this will no doubt make travel
treacherous with icy road conditions.
Temperatures will remain well below normal on Monday, but may warm up
quickly on Tuesday across the east as westerly flow increases
substantially, finally mixing out the remainder of the cold air.
However, another disturbance may bring more snow to the northwest.
Localized critical fire weather conditions are being observed this
afternoon over portions of central and eastern NM where the air mass
remains very dry, winds have increased and temperatures are above
normal. These conditions are expected to subside with sunset.
Mid to high level moisture will be increasing tonight and Wednesday
as an upper trough to our west advances over NM. This will result in
some cooler, although still mostly above normal temperatures and
higher humidities overall for the west and central, as well as a
slight chance for snow showers over mainly the northern mountain
The modified arctic air mass will continue to return to eastern New
Mexico each night for the rest of the week, but progressing closer
to the central mountain chain each night, and not receding as far
east during the daytime. Significantly colder weather is expected by
Saturday across the eastern plains and on Sunday area wide. Much of
the Northeast and East Central Plains may not get above freezing
Saturday through Monday. There will also be increasing chances for
snow starting Friday but moreso late in the weekend and early next
Area Forecast Discussion
National Weather Service Fort Worth TX
705 PM CST Tue Feb 9 2021
...New Short Term, Aviation...
.SHORT TERM... /NEW/
GOES-16 satellite imagery reveals most of North and Central Texas
remains beneath a blanket of low clouds this evening, with the
exception being across our far southwestern counties where some
clearing is occurring. This should be short lived, with overcast
skies expected regionwide overnight. Current temperatures across
the region range from the upper 20s along the Red River to upper
40s across Central Texas, with the freezing line roughly along a
Comanche to Fort Worth to Greenville line. The 00Z FWD upper air
sounding reveals very dry air above roughly 850 mb and a saturated
layer from 850 mb to just above the surface, which high res
guidance has been able to capture fairly well this afternoon.
We still expect light precipitation to initially develop across
portions of North and Central Texas beginning around or after 10
PM this evening, becoming more widespread closer to daybreak and
lingering through most of Wednesday. Temperatures will play a key
role in the type of precipitation that will reach the surface.
Light drizzle or rain is expected across most of Central Texas as
surface temperatures remain above freezing. It will be a different
story for most of North Texas, especially along the Red River
where temperatures are currently below freezing. Freezing drizzle
and light freezing rain will be possible along and north of a
Comanche to DFW to Paris line tonight through mid morning
Wednesday, with the highest chances for freezing precipitation
the further north you are located. Any accumulations/impacts
should be confined to areas mostly along the Red River, amounting
to less than one tenth of an inch. However, if temperatures were
to drop into the upper 20s further south, it is possible to see
the transition line of rain/drizzle and freezing rain/drizzle
shift further south. We`ll keep an eye on temperature trends and
adjust the Winter Weather Advisory if needed. For the morning
commute, light icing along elevated bridges and roadways will
lead to hazardous travel.
A cold and cloudy day is expected on Wednesday with light
precipitation continuing for most of the day. For Wednesday`s
high temperature, I did rely heavily on the NAM as it does handle
these shallow airmasses very well. Highs will struggle to reach 32
degrees along the Red River and remain in the mid to upper 30s
elsewhere. The colder temperatures along and north of the
Metroplex may result in the Winter Weather Advisory extending
beyond noon tomorrow. We`ll continue to monitor and make any
adjustments as needed.
.LONG TERM... /Issued 437 PM CST Tue Feb 9 2021/
/Wednesday Night through Tuesday/
Well below normal temperatures and continued chances for wintry
precipitation will remain in the forecast into early next week. A
deep longwave trough continues to spin across southern Canada
sending periodic shortwaves through the central CONUS and keeping
the door open to polar air spilling southward. By Wednesday night,
a southern stream shortwave will eject out of northwest Mexico
into Texas. With shallow cold air already in place, strong warm
advection atop the cold airmass will lead to rapid development of
rain across Central and North Texas. Strong isentropic ascent will
commence Wednesday afternoon and become focused across North Texas
late Wednesday night into early Thursday morning. The freezing
line is expected to be draped from near Paris to Fort Worth to
Lampasas by sunrise Thursday. Areas to the north and west of this
line will likely see a combination of freezing drizzle and light
freezing rain. This forecast has trended heavily toward the high
resolution guidance (NAM/TTU-WRF/HRRR) with respect to
temperatures so it does appear that we`ll be dealing with at least
some wintry weather late Wed into early Thursday. Additional
winter weather advisories/storm warnings are possible during this
time. The latest issue for early Thursday morning now concerns
the potential for some convective activity within this cold
airmass. Latest NAM and HRRR soundings north and west of the
Metroplex indicate parcels may have anywhere between 300-600 J/kg
of elevated instability. This would be more than sufficient for
isolated thunderstorms and perhaps some convective sleet/graupel
showers with surface temperatures in the upper 20s. We`re
monitoring this potential closely. Precipitation should exit the
area with the departing shortwave late in the day Thursday.
Friday should be a cold but precipitation free day with highs in
the 30s. The next blast of arctic air will arrive sometime on
Saturday, although there is still considerable spread among the
guidance. We`ll continue to side with the colder side of the
ensemble spread given the recent poor performance of coarser
resolution temperature guidance. Temperatures will likely fall to
below freezing by early afternoon and should remain there through
Monday. There will be some potential for a quick shot of rain/snow
during the day Saturday, but better chances for additional
precipitation will occur on Monday as another strong shortwave
moves out of the Southwest U.S. accompanied by better moisture. It
does appear that the column will be sufficiently cold during this
time for a precipitation type of all snow. While there is still
considerable uncertainty with respect to precip chances during
this time, it does appear that we`ll be quite cold Sunday and
Monday. Wind chills may approach -10 northwest of the Metroplex on
Sunday morning and -5 to -10 again on Monday. Precautions should
be taken now to protect outdoor pipes during this cold spell.
Poor flying conditions will prevail through and beyond the
forecast period. MVFR/IFR ceilings are being observed across all
the terminals this evening, but some clearing and VFR ceilings can
be seen on satellite imagery south and west of the terminals.
Overall, expect MVFR/IFR to prevail for the next few hours before
falling to the IFR category and remaining below 1000 feet through
the remainder of the forecast period.
Light precipitation may develop as early as 3Z this evening
across portions of North Texas, but the better chances will arrive
after 06Z. The precipitation will initially fall as light drizzle,
but as temperatures drop below freezing there will be a potential
for freezing drizzle across the Metroplex terminals tonight.
Temperatures at Waco should be just above freezing tonight, which
should allow for any precipitation to remain as light drizzle or
light rain. Drizzle will likely persist through most of the day on
Wednesday. Otherwise, north to northwest winds around 10 knots
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 31 35 33 34 30 / 20 30 90 50 5
Waco 34 39 34 39 31 / 20 50 90 70 20
Paris 30 36 34 34 29 / 30 60 90 70 5
Denton 28 33 29 33 25 / 30 30 80 40 5
McKinney 29 35 30 33 26 / 30 40 90 50 5
Dallas 32 37 33 34 31 / 20 40 90 60 5
Terrell 32 37 33 35 28 / 20 50 90 70 10
Corsicana 35 37 37 38 33 / 20 60 90 70 20
Temple 36 39 35 40 32 / 20 40 80 70 20
Mineral Wells 28 33 25 34 23 / 20 30 70 40 5
Winter Weather Advisory from 10 PM this evening to noon CST
Wednesday for TXZ091>095-100>104-115>117-129.
Area Forecast Discussion
National Weather Service Lincoln IL
820 PM CST Tue Feb 9 2021
Issued at 345 PM CST Tue Feb 9 2021
A weather disturbance will arrive Wednesday, bringing a good
chance of light snowfall to much of central Illinois, and possibly
some freezing rain south of I-70. There is yet another chance for
light snowfall Thursday. Much below normal temperatures will
continue through the upcoming week.
Issued at 820 PM CST Tue Feb 9 2021
Fairly quiet across the forecast area for the moment, with even
some thinning in the clouds across the north where cirrus is more
prevalent. Main concern will be after midnight south of I-70, as a
band of some light freezing rain/drizzle forms over southern
Missouri/Illinois and lifts north. Latest HRRR brings it to near
highway 50 by around 4 am. Greater impacts along this corridor
expected to be during the daytime hours. Further north, new NAM
guidance remains robust with snow development over the northern
CWA as early as late tonight, while other high-res guidance favors
more of a late morning into afternoon scenario. Some indications
that a more focused band could set up along I-72 which may amplify
snow amounts a bit more in that area, but will not make any
changes at this point. With the cloud cover, temperatures
shouldn`t drift too much from where they are now.
Updated zones/grids have been sent.
.SHORT TERM...(This evening through Wednesday)
ISSUED AT 345 PM CST Tue Feb 9 2021
Warm advection aloft associated with a disturbance ejecting out
of the southern Plains will gradually initiate precipitation over
the area starting late tonight/early Wednesday morning, especially
near and north of I-72 where some frontogenetical forcing appears
likely. South of I-70, some loss of ice aloft appears likely,
which should lead to light freezing rain and drizzle, and
therefore a winter weather advisory is in effect from midnight
tonight to 6 am Thursday. Snowfall amounts look relatively light
in general across central Illinois, with under an inch forecast
through Wednesday afternoon, however some banded structures could
develop resulting in locally more, perhaps 2 to 3 inches. Cold but
unremarkable temperatures tonight and Wednesday, with lows
ranging from 3 in Galesburg to 21 in Lawrenceville, and highs
Wednesday ranging from 14 in Galesburg to 27 in Lawrenceville.
.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 345 PM CST Tue Feb 9 2021
Another upper level wave rotates through the broad trough over the
continental US Thursday, with yet another good chance of light
snow, again forecast at under an inch.
Yet another wave is consistently progged by most models for
Saturday. Models spread somewhat more on precipitation amounts and
timing, but at this point light amounts appear likely. This
feature will likely be followed by another pronounced drop in
temperatures, taking highs from the teens to mid 20s Thursday,
Friday, and Saturday down to perhaps single digit temperatures at
most locations Sunday. Nevertheless, model spread in temperatures
increases dramatically over the weekend as well, indicating high
uncertainty in exact values. Thereafter, no end appears to be in
sight for the well below normal temperatures for the next week.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 519 PM CST Tue Feb 9 2021
VFR conditions to prevail in the short term, but ceilings
expected to lower below 3,000 feet between 06-12Z ahead of the
next disturbance. Light snow is expected to gradually develop on
Wednesday morning, with the heavier snow band bringing visibility
down to around 1 to 2SM. Where exactly that heavy band ends up is
a bit uncertain, but areas from KSPI-KCMI appear to have a higher
probability at this time. North winds of 5-10 knots will become
more northeast and increase a bit by midday Wednesday.
Winter Weather Advisory from midnight tonight to 6 AM CST
Thursday for ILZ071>073.
Area Forecast Discussion
National Weather Service Key West FL
1041 PM EST Tue Feb 9 2021
A fairly muggy air mass resides over the Keys this evening, with
dewpoints running near 70F. Where sea-surface temperatures north
of the Keys are in the upper 60s or cooler, some sea fog
development is possible overnight. Satellite imagery shows that
this process has not yet begun, with the nearest indication of sea
fog being off the coast of Bonita Springs. The HRRR has backed off
on extent of fog late tonight over our Gulf waters, but will first
give fog a chance to develop overnight before possibly yanking it
from the forecast.
Otherwise, some flat pancake stratocumulus occasionally drift in
from the Straits, capped by a subsidence inversion that the 00z
KEY sounding showed near 2,000 feet. This is too shallow of a
mixed layer to support any shower activity, so confidence remains
high in shower-free weather through Wednesday. Indeed, the
sounding observed a 500 mb height of 5880 meters, highlighting the
strong mid-level high pressure over South Florida and the Keys
Latest near-term guidance shows fresh easterly breezes for the
rest of tonight over the distant Straits, thanks to a nocturnal
easterly surge off the north coast of Cuba. With the most recent
ASCAT pass squarely missing the waters and a lack of obs way out
there, will have to just rely on guidance to support insertion of
the cautionary headline over the Straits for the rest of tonight.
From synopsis...The Keys will remain to the south of an Atlantic
ridge extending across Florida through Thursday. Moderate easterly
breezes will prevail across the Keys coastal waters, except for
fresh surges over the Straits through tonight and again on
Wednesday night. Breezes will turn to the southeast by Thursday
night and subside as a cold front moves into the northern Gulf of
Mexico. Light to gentle breezes will prevail Friday through
Some sea fog formation is still possible over the cooler waters
north of the Middle and Lower Keys overnight, but easterly surface
winds will hold any areas of fog comfortably north of the island
terminals. Will therefore carry a persistent forecast of
stratocumulus near 2,000 feet and easterly surface winds.
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Area Forecast Discussion
National Weather Service Lake Charles LA
939 PM CST Tue Feb 9 2021
Visibilities are already beginning to fall across the region this
evening. Fog nearer the coast is expected to be more dense as it
will be largely of marine origin while fog development further
inland across central Louisiana will be more patchy, radiational
fog. Weather grids and wording were updated to reflect the
already ongoing fog as well as the expected evolution through the
night. Short range guidance is in good agreement on the marine fog
remaining over the nearshore waters through the day so felt
comfortable extending the marine fog advisory through 06Z
Thursday. This may need to be extended a bit further, but the
influence of the approaching front may dissipate most of the
marine fog beyond this time frame. Also added isolated showers
beginning after 12Z Wednesday to account for the HRRR and high
res models depicting a few showers developing early. The
remainder of the forecast is on track.
.PREV DISCUSSION... /issued 628 PM CST Tue Feb 9 2021/
For the 02/10/21 0000 UTC TAF package.
Area remains to the SE of a stalled frontal boundary stretching
near a Shreveport, LA to Conroe, TX line early this evening,
yielding a continued influx of low level MSTR. Another round of
IFR/LIFR conditions is forecast tonight, with low CIGS and reduced
VSBYS already observed at KBPT. Used a blend of latest guidance
and persistence to time the arrival and subsequent improvement
tomorrow, which again will be sluggish. In addition, scattered
shower activity is expected tomorrow, especially by afternoon,
amid increasing MSTR/lift as a remnant warm front over the Gulf
lifts north through the area.
PREV DISCUSSION... /issued 428 PM CST Tue Feb 9 2021/
A rather warm day across the region saw temperatures in the low to
mid 70s as the fog eroded through the morning hours. The sea fog
will move in tonight and begin to lower the visibility to less
than 1/2 mile from the I-10 corridor south to the coast including
the coastal waters. In the coastal waters visibility will range
1/4 miles to 1/2 mile later this evening into the overnight
hours... visibility will improve during the late hours tomorrow.
Scattered showers and thunderstorms for tomorrow as moisture is
pooling over the region as we remain in the warm sector. Upr lvl
energy advects ovr the rgn fm an upr lvl low back to the west tmrw.
The next cold front though is progged into the region on Thursday
which will lower temperatures somewhat but the colder air moves
in early Friday. The upr lvl low back to the west is expected to
fill and slowly and lift out but rains will continue into Friday.
Looking at one to three inches of rains from Wednesday afternoon
through Friday afternoon. A secondary cold surge on Sunday will
drive temperatures into the 20s for morning lows Sunday and into
the low 20s Monday and Tuesday morning. This will be a strong
arctic surge that is expected to produce the chances for snow on
Monday into Tuesday. We are going to have to wait another day or
so to sort the strength of that system. But it will bring in the
coldest air of this winter.
.PRELIMINARY POINT TEMPS/POPS...
AEX 53 68 53 59 / 0 50 90 90
LCH 58 73 61 69 / 0 40 70 80
LFT 60 75 63 73 / 10 30 50 80
BPT 59 73 61 70 / 10 50 60 90
LA...Dense Fog Advisory until noon CST Wednesday for LAZ041>045-
TX...Dense Fog Advisory until noon CST Wednesday for TXZ215-216.
GM...Dense Fog Advisory until midnight CST Wednesday night for GMZ450-
Dense Fog Advisory until noon CST Wednesday for GMZ430-432-435.
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
917 PM CST Tue Feb 9 2021
915 PM CST
Just a few mainly minor adjustments to the grids this evening. The
first was to knock several degrees off the low temperatures. With
dewpoints solidly in the 5 to 15 below zero range, it didn`t take
long after sunset for temperatures--especially in our outlying and
typical cool spots--to tank. The diurnal curve will continue to
flatten some through the rest of the night, and some additional
high cloud cover starting to stream in overhead should help mute
any additional falls.
We continue to note some degree of disparity in the very short
term guidance regarding precipitation trends for tomorrow morning
and afternoon, mainly as they pertain to the northern terminus of
any snow potential. The latest RAP/NAM/HRRR/NAMNEST are showing
essentially precipitation-free conditions across the I-88
corridor, while the GFS, CMC/RGEM, and ECMWF (as well as their
respective ensembles) develop an additional west-east band of
light precipitation through the morning hours.
Oddly enough, the precip-free RAP does develop a rather coherent
zone of respectable isentropic upglide--maximized near/along the
280-285 K theta surfaces--Wednesday morning, tied to the leading
edge of a low-amplitude shortwave which is presently scooting
across eastern Nebraska. At the same time, all guidance indicates
we`ll be in a favorable region to locally enhance upper jet
divergence on the western flanks of a slightly anticyclonically-
arcing 120 kt jet streak. While the signal for any coherent low-
level response in the f-gen fields remains low, envision that this
persistent upglide/WAA should be sufficient to help saturate
things enough to crank out some light snow a bit farther north
than the American hi-res guidance would currently suggest.
Upstream radar returns across east-central Nebraska are likely
tied to this disturbance and burgeoning upper jet divergence, and
look somewhat convective in nature, which isn`t too surprising
given the narrow regions of analyzed steepened lapse rates around
600 mb. Extrapolating this activity slightly north of due east
within the mean flow suggests some credibility to the ECMWF, RGEM
which develop light snow across the I-88 corridor tomorrow
morning. Have followed their lead here and gently expanded likely
PoPs a bit farther northward although do note there will be a
sharp northern cutoff given the dry low- level airmass in place. A
quick 1 to possibly even 2" can`t be ruled out with this northern
activity given another round of high-ratio snow and the presence
of at least modest static stability reductions. Thinking is that
this activity should develop late enough in the morning so as to
limit travel issues with the morning commute.
No changes to the PoPs towards I-80 and south except to nudge
those up a smidge with accumulating snow looking like a good bet.
Multi-model consensus suggests up to about 0.10" of liquid in this
area with the going forecast of 1-2" (maybe a three-inch amount in
there somewhere) there also looking good, and a bit less
conditional than the activity farther north. Updated products have
330 PM CST
The main forecast concern is the likelihood of another round of
fluffy snow accumulations on Wednesday, though with lighter
amounts than what we saw on Monday. In addition, cold wind chills
will be an ever-present issue as low level Arctic air mass remains
entrenched across the region. Drivers should be ready for yet
another day of travel impacts on part of Wednesday as we continue
with the 18-36 hour interval for fluffy snow accums, with more to
come in the long term forecast period.
In the near term, the lake effect snow over primarily Porter
County has finally slid east and diminished intensity, with
visibility at KVPZ as of this writing up to 7 miles. Could see
some lingering travel impacts on some roads due to the light
accums today and cold temps. For this evening into the overnight,
Day Snow-Fog RGB shows there`s a solid window of radiational
cooling to start for I-80 and north, so temperatures should drop
quickly toward and after sunset, to the single digits above and
below zero, coldest in favored outlying spots, where we`ll need to
keep an eye on trends. Light northerly winds and temperatures not
as cold as last night will keep minimum wind chills in check
relatively speaking, down as low as 10-15 below, locally near 20
below in outlying areas.
Mid and high clouds will then increase overnight in advance of our
next round of snow, so temperatures will likely flat-line or
slowly increase toward daybreak Wednesday. Relied heavily on the
global guidance, Canadian regional models, and ensemble consensus
for PoP and snow forecast. Strongly suspect NAMs and high res WRFs
are spuriously struggling to saturate in the Arctic air mass, a
not uncommon issue with these models, that usually goes the other
way in reality. Large scale lifting mechanism will be placement
of our area in the right entrance of a strong upper jet streak
over the northern Lakes. Model guidance is indicating a banded
nature to QPF output, so am expecting a modest f-gen contribution
again, though likely not to extent/magnitude of Monday, with a bit
of warm advection at 850 mb implying lower-level f-gen, along with
some wind convergence at 700 mb north of I-80 possibly hinting at
placement of mid-level f-gen banded component.
Light to occasionally moderate snow banding should expand east-
northeastward during the morning, and will need to watch for a
dual structured nature (a northerly mid-level f-gen driven band
and southerly focused one I-80 and south driven by lower-level
f-gen). One thing that even the preferred guidance is in
agreement with in the QPF and snow output is a sharp northern cut-
off to the precip shield, which in this forecast was indicated
just a bit north of I-88. Indicate some lowering PoPs north of
that for uncertainty, as some guidance does bring measurable QPF
up closer to the WI state line. With more modest nature of forcing
and steepened but not as pronounced mid- level lapse rates vs
Tuesday`s setup, favoring a lower QPF high PoP scenario for areas
in line to see snow, though will need to investigate wetter
guidance such as GFS as to how realistic its output is in any
potential for over- performance tomorrow. Cobb BUFKIT output from
the GFS supports well above climo snow ratios again from 15-20:1
due to the relatively modest lift intersecting upper portion of
deep DGZ for several hours.
The official snow forecast indicates a coating to up to 1" from a
few to several miles north of I-88 down to about I-80 and then
1" to as much as 2" I-80 and south. Due to the cold air
temperatures (highs ranging from 10F-20F northwest to southeast)
rendering road treatments less effective, even these lighter
amounts can be expected to cause some travel impacts, possibly
overlapping a portion of the morning commute. The snow should
slide east- southeast during the afternoon and end by the early
evening for most locations. Exception to this could be for
portions of northwest Indiana, where northerly flow lake effect
snow showers could develop from the late evening into the
overnight, though confidence is on the lower side with varied
depiction from the guidance. If clouds clear more than forecast
tomorrow night, temperatures and minimum wind chills could be a
bit lower than official forecast (and vice versa).
301 PM CST
Thursday through Tuesday...
Continued cold conditions are expected through the remainder of the
forecast period, including a reinforcing shot of even colder air for
the late weekend into early next week. Multiple periods of snow
also remain likely, though different portions of the forecast area
are favored with each one, and nothing looks overly significant at
least into early next week.
Deterministic models of course offer a variety of details, but the
overall picture painted by ensemble solutions show the local area
continuing to sit on the southern edge a broad and persistent
surface high locked in across central Canada and the north central
CONUS. Anticyclonic low level flow will continue to support cold
northerly winds, occasionally veering enough toward the east to
establish some transient lake effect plumes over northeast IL and
then backing west to push the activity into northwest IN.
In addition to the periods of lake effect, weak upper waves passing
to our north will bring a quick shot of more widespread, though
still light, snowfall Thursday afternoon into evening, and again
from late Friday into early Sunday.
Following the weekend system, models start to suggest a more
amplified pattern may push the center of the arctic high farther
south, even toward the western Great Lakes. This outcome would
support single digit highs for much of the area both Sunday and
Monday, with double digit negative lows Sunday night, especially
outside the metro area. Confidence is not high on the timing and
magnitude of this solution, nor the hints of slightly milder highs
near 20 returning by Tuesday.
For the 00Z TAFs...
* Fair weather overnight into early Wednesday morning
* Next snow event arrives mid-morning Wednesday
Our pattern of short waves moving through every 24 to 36 hours
continues, with the start of this forecast period in-between
systems. TAFs start off with scattered high clouds and light
northerly winds. These conditions will remain through mid-AM
Wednesday morning, when some mid-level broken ceilings move in.
Next weather system is expected to arrive Wednesday mid-morning (13
to 14Z), progressing from the south towards the north. The more
intense snow is expected to be towards the south, so looking at
predominate VIS at GYY and MDW of 2SM in -SN, with an IFR TEMPO
group as low as 1 SM from 15/16Z through early afternoon (19/20Z),
while sites further north will have less restrictive visibilities (2
to 3SM at ORD/DPA). With RFD being the furthest north site, I expect
minimum impacts at that site, with mainly snow flurries starting
later and ending earlier (16Z to 19Z).
This system appears to be short-lived, and expect the snow to move
out from the northwest towards the southeast in the mid to late
afternoon (21Z), departing GYY towards the end of the TAF period.
Winds continue to be light from the north throughout this forecast
period as surface high pressure remains to our northwest.
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Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
945 PM CST Tue Feb 9 2021
Subfreezing temps surged south through the east AR delta this
afternoon. The thermal trof was nearly juxtaposed with a surface
pressure ridge axis. This was wasn`t modeled well, but late
afternoon runs of the HRRR seemed to catch on quickly. The Ice
Storm Warning was expanded south through the I-40 corridor in east
AR, where light freezing rain fell earlier this evening.
The surface thermal trof/freezing line had remained static in
position since sunset, as northerly surface winds veered
northeast, parallel to the thermal gradient. Concurrently, KNQA
VAD wind profiler showed strengthening warm advection above the
1500 ft deep frontal inversion. This warm advection will gradually
strengthen overnight, supporting scattered areas of drizzle and
rain, which will freeze over most of east AR, the MO bootheel and
far northwest TN.
Heavier precip, and a potential ice storm, appears on track for
Wednesday night and Thursday morning, under the right entrance
region of the upper jet.
.PREV DISCUSSION... /issued 521 PM CST Tue Feb 9 2021/
Updated 00z Aviation Discussion.
PREV DISCUSSION... /issued 350 PM CST Tue Feb 9 2021/
A significant ice storm appears likely across portions of the Mid-
South over the next 48 hours as moist air is forced over the top
of a shallow arctic air mass. The forecast is complicated enough,
but the messaging of hazards covering multiple periods is even
more so. In trying to simplify the process, we`ve opted to start
the Ice Storm Warning to 6 PM this evening for portions of
northeast AR, the Bootheel, and northwest TN. The remaining areas
in the Watch remain unchanged. Now for the nerdy part...
A broad trough is affecting much of the CONUS this afternoon with
a deep vortex centered southwest of Hudson Bay. The flow aloft
remains quasi-zonal with a low-amplitude shortwave trough located
off the CA coast. Closer to home, the quasi-stationary arctic
front extends across north MS into middle TN, separating
temperatures in the 20s and 30s from those in the 50s and 60s.
Automated stations currently range from 28F at Kennett (MO) to 68F
at Aberdeen (MS). Light freezing rain has already occurred in
Jonesboro this afternoon and temperatures aren`t expected to warm
much, if at all, over the next 24+ hours.
We`re watching a strong upper tropospheric jet over the Great
Lakes which will enhance large scale ascent tonight via the
thermally direct circulation in the absence of strong QG forcing.
Isentropic ascent will increase overnight, especially in the
285-290K layers. This will maintain broad lift, resulting in
periods of freezing rain and freezing drizzle north of the quasi-
stationary front. While significant accumulations of ice aren`t
anticipated tonight, there may be enough to create some travel
issues along/north of a line from Harrisburg, to Dyersburg, to
Martin. With this in mind, we went ahead and pushed the start time
of an Ice Storm Warning up to 6 PM this evening, running through
noon Thursday. We won`t see freezing rain or continuous impacts
throughout the duration of the warning as the main focus still
lies in Wednesday night into Thursday as QG forcing for ascent
increases and rain/freezing rain becomes more widespread.
As we saw yesterday, warm advection in the layer around 850 mb
will produce a prominent warm nose around 6-8C. The subfreezing
air north of the arctic front will only be up to 2000 ft deep,
resulting in a classic freezing rain/drizzle sounding. As the cold
air deepens, we may see some sleet (and perhaps some snow) mix in,
but freezing rain looks to be the predominant weather type at the
onset. The front will sag south Wednesday night and Thursday,
allowing the subfreezing air to to approach the I-40 corridor. The
southern extent of where the freezing line will set up by 12z
Thursday is a huge area of uncertainty. This makes the forecast
less certain from Memphis to Jackson but points to the north look
more certain to see significant ice accumulations.
The 25th-75th percentiles ice accumulations for the whole event
range from roughly 1/4 to 1/2 inch of ice from Jonesboro to
Union City. Worst case scenario (90th percentile) has a full inch
of ice in this swath with near 1/2 inch as far south as Memphis
and Jackson. On the other end of the spectrum, the 10th
percentile calls for roughly 2/10 within the Ice Storm Warning.
Needless to say, an inch of ice would be devastating. With all of
this in mind, the official forecast of up to 0.35 inches of ice is
quite conservative and may need to be increased depending on
where the bands of heavier rain develop. We`re certainly watching
this closely and will adjust as needed.
This system looks to move east of the area Thursday evening with a
wintry mix possible as precip winds down. Little in the way of
additional accumulations are expected after sunset. Then the cold
air settles into the Mid-South. We`ll see several days with highs
in the 20s/30s with lows in the teens. Wind chill readings Friday
and Saturday will be quite cold, approaching single digits in
some areas. A fast-moving trough will bring a chance for very
light snow to portions of the area Saturday evening, but no
impacts are anticipated. A reinforcing cold shot will arrive by
Sunday (and Monday), where wind chill values may fall below zero.
Another deep trough is progged to affect the region early next
week, bringing another chance for snow to the Mid-South. Given
the plethora of moving parts between now and then, confidence
remains limited but low PoPs were included Monday and Tuesday.
MVFR conditions will prevail through the evening eventually
becoming IFR by tonight. Showers and wintry precipitation will
affect most areas with JBR having the best potential for freezing
rain into tomorrow morning. Winds will mostly be NNE between 5 to
10 kts through much of the period.
AR...Winter Storm Watch from Wednesday evening through Thursday
morning for Lee AR-Phillips.
Ice Storm Warning until noon CST Thursday for Clay-Craighead-
MO...Ice Storm Warning until noon CST Thursday for Dunklin-Pemiscot.
MS...Winter Storm Watch from Wednesday evening through Thursday
morning for DeSoto-Tunica.
TN...Winter Storm Watch from Wednesday evening through Thursday
morning for Benton TN-Carroll-Crockett-Fayette-Gibson-
Ice Storm Warning until noon CST Thursday for Dyer-Lake-Obion-
Area Forecast Discussion
National Weather Service Marquette MI
751 PM EST Tue Feb 9 2021
.SHORT TERM...(This evening through Wednesday)
Issued at 408 PM EST TUE FEB 9 2021
WV imagery and RAP analysis indicated a mid/upper level low over
northern Manitoba/Ontario with a broad trough through the northern
CONUS. At the surface, low pressure was located over northwest
Ontario while Arctic high pressure extended from Alberta through the
northern Plains to the southern Great Lakes resulting in brisk WSW
flow through the northern Great Lakes. Visible satellite indicated
continued multiple wind parallel LES aligned with the wsw winds
brushing the northwest portion of the Keweenaw. Otherwise, mostly
clear skies prevailed across the rest of the area with temps
mainly in the single digits.
Tonight, Wind chills similar to Sunday night are expected with the
unrelenting westerly influx of Arctic air. Lows into the -5 to -20
range with winds of 5 to 15 mph will drop wind chill values into the
-20 to -35 range, coldest interior west. A downslope land breeze
near Marquette will also help sustain higher winds and severe
wind chills even if the temps are not quite as low.
A weak shortwave trough pivoting around the mid level low will
result in subtle wind direction changes affecting the location of
the heavier LES. As the shrtwv moves through tonight expect winds to
veer slightly, especially over the northern Lakes. This will result
in increasing low level conv likely to support a stronger or
dominant band that should shift through the Keweenaw. Plenty of
instability will be available to support stronger LES with lake
induced CAPE values to 500 J/Kg and equilibrium heights to around
9k ft. However, confidence is still limited regarding the
duration of the band and overall snowfall amounts. Even with the
extreme cold limiting SLR values below 20/1, snowfall amounts
into the 3 to 6 range are likely with some locally higher amounts.
Late tonight the LES could also move into the shore from Grand
Wednesday, convergent westerly flow is likely to continue into the
Keweenaw with additional moderate to ocnly heavy LES. The band(s)
may also affect the areas from Grand Marais eastward with moderate
to ocnly heavy snow with amounts also into the 3 to 6 inch range
.LONG TERM...(Wednesday night through Tuesday)
Issued at 438 PM EST TUE FEB 9 2021
Lake-effect showers in the west to north snow belts look to dominate
the extended period. Could see some synoptic snowfall associated
with a shortwave Thursday night into Friday, but snowfall
accumulations should be under an inch save for in the Keweenaw (and
even then, not much more there than elsewhere). This weekend could
see some enhanced lake-effect snow in the north to northwest snow
belts due to a low progging north up the East Coast. But afterwards,
models diverge for early next week as to whether lake-effect snow
will still occur or not.
As models predict that the jet stream will remain to the south of
us, don`t expect much change in weather conditions Wednesday night
to early Thursday evening; winds are predicted to become more
northerly Wednesday night and Thursday, and they are predicted to
become lighter. Therefore, as lake-effect snow shifts to the
northwest and north snow belts, expect heavier snowfall
accumulations along the Superior lakeshore as convergence of the
winds at the shoreline due to friction create the heavier snowfall
rates. Hence, lake-effect snow should not be going too far inland,
and higher snowfall amounts should be limited to the shoreline
Models indicate a shortwave moving through the area Thursday evening
and Friday. While there is some uplift given a little bit of
frontogenesis at 850mb and moisture advection, not much is expected
out of this shortwave, as the lower levels should still be rather
dry. Therefore, not much snowfall is predicted with the passage of
this shortwave; I`m thinking no more than an inch of snowfall across
the U.P., save in the Keweenaw, where there could be an additional
inch due to lake-enhancement.
A low pressure is indicated to prog up the East Coast this weekend,
and should bring additional moisture into the area. The GFS also has
a mesolow set up over eastern Lake Superior Saturday and Sunday as
the low over the East Coast progs northeast. Therefore, the mesolow
over the eastern lake and the additional moisture should help
reinvigorate lake-effect snow in the northwest to north snow belts.
This mesolow, in conjunction to the the low pressure out east that
will bring CAA over our area behind it, should increase wind speeds.
This should bring lake-effect snow much deeper into the interior of
the U.P. this weekend. Indeed, winds may rotate rather quickly over
the mesolow over the lake this weekend, and could create a
convergence area of enhanced lake-effect snowfall in the north snow
belts between Marquette and Munising. Snowfall from this weekend
could become significant at spots, particularly in that convergence
Some lake-effect snow may hang around through Monday, but most of it
should end before Tuesday as winds shift to come from the south
ahead of an approaching shortwave from the west.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 751 PM EST TUE FEB 9 2021
VFR conditions are expected to prevail at KIWD and KSAW throughout
the TAF period. At CMX, WSW wind lake effect snow is ongoing and is
expected to gradually veer to WNW by Wednesday morning. Hi-Res model
guidance indicates the dominant lake effect band currently north of
the Keweenaw will move over CMX around 04Z as winds shift from WSW
to WNW. LIFR vsby is expected under this lake effect snow band, but
it`s unclear how long the band will stay over CMX and whether or not
it weakens Wednesday morning. Gradually improving vsby Wednesday
morning seemed most likely, but some model guidance stalls the lake
effect band near CMX with IFR vsbys persisting most of Wednesday.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 408 PM EST TUE FEB 9 2021
Expect westerly winds of 20-30kt to prevail across Lake Superior
shifting to the west and then nw into Wed. There will be gale force
gusts to 35kt at times given the extreme instability over the lake
in this arctic air mass. Hvy freezing spray will also continue.
Winds will then shift more northerly and subside a bit for Thu thru
Sat, but hvy freezing spray is still expected at times as arctic air
remains over the area.
Wind Chill Advisory until noon EST /11 AM CST/ Wednesday for
Wind Chill Advisory from midnight EST /11 PM CST/ tonight to 10
AM EST /9 AM CST/ Wednesday for MIZ006-007-012>014-085.
Winter Weather Advisory until 1 PM EST Wednesday for MIZ001-003.
Heavy Freezing Spray Warning until 7 PM EST /6 PM CST/ Wednesday
Area Forecast Discussion
National Weather Service San Angelo TX
822 PM CST Tue Feb 9 2021
...New SHORT TERM...
(Tonight through Wednesday)
Issued at 816 PM CST Tue Feb 9 2021
...Updated to drag the Winter Weather Advisory a little farther
south, and to start it a little sooner...
After slightly retreating late this afternoon, colder air mass is
sagging south again across West Central Texas. Winds have shifted
back north across the I-10 corridor and temperatures have
dropped. Earlier models significantly too warm and have used the
latest RAP and HRRR as a first guess for the first 18 hours. This
drops Abilene?Sweetwater into the upper 20s, Brownwood below
freezing, San Angelo to Freezing, and areas farther south much
cooler as well.
Latest models also show decent isentropic lift over the boundary
and a growing area of drizzle likely. Starting to see a little of
this from radar and observations. With all that, and with the
colder temperatures, have pulled the Winter Weather Advisory
another set of counties southward and started it earlier. San
Angelo is right on the edge and will continue to monitor to see if
it eventually needs to be added as well.
(Wednesday night through next Tuesday)
Issued at 230 PM CST Tue Feb 9 2021
..Record-Breaking Cold Temperatures Possible This Weekend...
Where to begin? The forecast from Thursday through the weekend
looks very messy with lots of uncertainty from timing and
intensity of the cold air to precipitation chances. Overall, the
GFS has continued to run colder, so have generally trended
temperatures in that direction. Both the NAM and the GFS show elevated
instability on Wednesday night with the approach of a shortwave.
This instability may result in pockets of light wintry
precipitation across the Big Country and northern Concho Valley through
Thursday morning. At this point, accumulation will be light and
spotty, but roads and bridges in some locations could become
hazardous. Precipitation chances should end by Thursday
afternoon, with clearing skies on Friday, but continuing cold
The GFS and Canadian models continue to show another surge of even
colder air on Saturday through Monday. Low temperatures in the
teens or even single digits may occur on Sunday and Monday, which
would be record-breaking conditions. In general, we have trended
on the cold side for temperatures, given the consistency of the
GFS and the way this season`s cold snaps have evolved. There also
exists some uncertainty with shortwaves bringing additional
chances of overrunning wintry precip on Saturday and Monday. For
now, the big story is the potential for record-breaking cold this
Issued at 523 PM CST Tue Feb 9 2021
Widespread IFR and LIFR conditions will return across the area
overnight tonight. Look for areas of dense fog to reduce
visibility. In fact, a freezing drizzle is possible across KABI.
However, terminals south of KABI may see a light drizzle that will
not freeze during the later part of the TAF. Otherwise, expect
very little improvement across the terminals for tomorrow
.PRELIMINARY POINT TEMPS/POPS...
Abilene 27 33 24 33 / 10 10 40 30
San Angelo 32 42 31 40 / 5 10 60 40
Junction 46 47 34 41 / 5 20 70 70
Brownwood 30 36 27 36 / 10 20 60 50
Sweetwater 27 34 26 33 / 10 10 30 30
Ozona 52 57 37 43 / 5 10 60 50
Winter Weather Advisory until noon CST Wednesday for Brown-