Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/18/21
Area Forecast Discussion
National Weather Service La Crosse WI
952 PM CST Wed Feb 17 2021
.UPDATE...
Issued at 952 PM CST Wed Feb 17 2021
Radar at 952 pm is...a mess regionally. Weak forcing on the 275K
surface and shortwave trough activity passing through while the
lowest levels have a dry air mass to battle. But, some light snow
down to about 4SM is being reported here and there. Some dustings
of snow out there as well, but very hard to predict where. Will
continue to have iso-sct snow showers overnight in the forecast.
Working on an update for higher snow chances Thu afternoon and
eve along and north of I-94 mainly. I think the models are
underdoing this negatively tilted shortwave trough moving the
area. Mesomodels now starting to trend up in precipitation
coverage since 00Z runs or so. It is becoming more dynamic into
WI in the mid- afternoon and into the early eve...looking like a
light amount, higher snow chance event. Now 50% chances in
northcentral WI, decreasing southward...about a 20% uptick.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 201 PM CST Wed Feb 17 2021
Early afternoon radar imagery showed light snow continuing across
south-central Minnesota and into northwest Wisconsin, mainly driven
by isentropic ascent. Farther southeast, certainly seeing the
effects of a dry layer up to about 700 mb, as there are plenty of
radar returns, but nothing in the way of ground truth other than a
few passing flurries seen on MNDOT webcams. RAP guidance has been
persistent in showing isentropic ascent tapering off as we go
through the afternoon and that seems to be panning out as radar
returns have decreased in intensity over the past 1-2 hours or so.
It does pick up again overnight as some weak shortwave energy
slides through, so could see some flurries continue across the
entire area through Thursday, but the lift does remain quite weak,
so wouldn`t expect much in the way of accumulation. Once all snow
comes to an end, could see up to around 1/2" along our border
with NWS Twin Cities and lesser amounts to the southeast. Should
any pockets of stronger forcing develop, it wouldn`t take much to
get near 1" given the 18-20 to 1 snow to liquid ratios, but again,
guidance remains persistent in isentropic ascent tapering off for
a time this afternoon. Otherwise, we continue our gradual warming
trend on Thursday, with highs in the teens and 20s, though there
is a chance clouds could keep them a bit lower.
.LONG TERM...(Thursday night through Wednesday)
Issued at 201 PM CST Wed Feb 17 2021
Although small, chances for snow remain off to the east of the
Mississippi River Thursday night. Any lingering precipitation will
continue to exit the region Thursday night as high pressure
builds in from the west and the deeper longwave trough slides off
into the eastern CONUS. The region continues its slow warm up
with afternoon high temperatures in the teens on Friday. Low
temperatures will dip into the single digits above and below zero.
Additional warming is in store through the weekend as 850 mb
temperatures rebound to near -5C by Sunday and surface winds
become more southerly over the weekend. High temperatures are
expected to increase into the upper 20s to low 30s. Additionally,
above freezing temperatures are still on track over the first half
of the work week, with overnight lows decreasing only into the
teens and 20s above zero.
The next best chance for precipitation comes on Sunday, but there
has been a decreasing trend from previous model guidance runs. The
17.00z GEFS is on the more aggressive side with this system
producing higher snowfall accumulations across the region. However,
the 17.00z ECMWF EPS is on the lighter side with several members
even keeping the area completely dry. The general idea is that a
low pressure system will pass to the south of the region. The
question is how far north of the system will the shield of
accumulating snowfall advance. The differences and spread between
models is partially due to how each handles the mid- to upper-
level flow. While surface temperatures will increase under ridging
this weekend, the ridge itself would be relatively weak and
flattened. The flow would also be somewhat split as two shortwaves
move eastward through the region. One shortwave looks to move
through southern Canada, while the second progresses through the
central CONUS. How these separate waves potentially interact as
they progress eastward is one of the many issues introducing such
a spread between the models and ensemble members. Will continue to
stick with the blended model guidance with bringing in slight
chances for snow for much of the area.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 558 PM CST Wed Feb 17 2021
Periods of light snow or flurries summarizes the TAF period. A
lull will occur into the evening, before more light snow moves in
from the west overnight. It could be MVFR visibility -SN, but for
now confidence is not high enough to include that in the TAF.
Ceilings will likely come into the MVFR category however.
Will have to keep an eye on late afternoon and evening on Thursday
as a bit stronger weather system moves through. It develops as it
shifts east, which could bring MVFR SN in that period, with a bit
higher probability to KLSE.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
UPDATE...Baumgardt
SHORT TERM...CA
LONG TERM...Peters
AVIATION...Baumgardt
Area Forecast Discussion
National Weather Service Binghamton NY
956 PM EST Wed Feb 17 2021
.SYNOPSIS...
A disorganized series of upper level disturbances and weak
coastal lows will bring an extended period of light to moderate
snow to parts of the region starting in the pre-dawn hours
Thursday morning, and extending into Friday. Snowfall amounts
through Friday evening will range from 2 to 5 inches over the
Southern Tier of New York, with 3 to 6 inches in the Catskills
and Northeast Pennsylvania. Expect lighter amounts elsewhere in
Central New York. Colder air will push into the region behind
this system, bringing scattered lake effect snow showers to the
area Friday night through Saturday, with some light
accumulations possible. Sunday will be a fair weather day with
high pressure building in. But an active pattern will continue
next week with rain and snow moving through the area on Monday,
with lake effect snow showers likely through mid-week.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
955 pm Update...
Water vapor imagery shows the beginning of a baorclinic leaf
like pattern over the midwest to middle Mississippi Valley as
the core of the upper level wave was moving through eastern
Texas at this time. As the moisture heads northeast it is taking
on the classic warm air advection look with anticyclonic
curvature at upper levels. Indeed models all show strong warm
air advection tonight through Thursday as the above mentioned
upper level wave moves northeast to the eastern Great lakes by
00z Friday. The 850 mb low will take a similar track with its
attendant warm air advection (or isentropic lift if you prefer
that coordinate system). This overall will bring a modest amount
of moisture northward as it is lifted leading to widespread
snowfall. Moisture is rather limited with this feature as it
eventually weakens over NY Thursday night and Friday. This
occurs as a coastal low gets going well offshore with the bulk
of the moisture. So in the sum we are expecting a longer
duration light to occasionally moderate snowfall with the
highest amounts in northeast PA/Catskills and southern tier of
NY. Overall these areas will see generally 3"-6" with locally
higher amounts in the Poconos and Catskills. Farther north, from
the Finger Lakes, Syracuse and Oneida County we are expecting
around 2-4" of snow.
The snow will begin first in a band across northeast PA between 06z
and 09z. This is in response to a surge of warm air advection which
leads to some frontgenetic forcing. We are beginning our snow
earlier in northeast PA as all models, hi-resolution and even
synoptic scale are showing this band. So we will begin the winter
weathr advisory sooner in these areas to account for earlier snow
onset. Again, moisture looks limited so we are expecting basically 1-
3" before dawn northeast PA. This will affect the morning commute
down there. Then the snow likely will back off until strong warm air
advection arrives later in the morning into the afternoon. This will
be the main surge of light to moderate snow. Then NAM12 and hi res
CMC both show another low-level jet at 850 mb which enhances lift
Thursday night associated with the upper level wave. This will be
another period of snow of central NY and northeast PA.
Then for Friday continued lifting aloft from PV advection and a
fairly decent mid to upper level short wave will continue light
snows which will taper to lake enhanced snow showers later Friday.
Made some tweaks to POP to further refine timing and temperatures.
As for snowfall forecasts 18z runs had the following snowfall:
18z Euro 4"-7" in southern central NY and northeast PA/Catskills and
1"-4" farther north.
18z GFSv15 (operational) widespread 6-9 inches south and east of a
Cooperstown NY to BGM to Towanda PA line in the BGM forecast area. 2-
6" northwest to Finger Lakes.
GFSv16 6-8" ne PA and Sullivan Co and 3" to 6" southern tier and 1-
4" farther north.
The 00z HRRR run had 5"-8" northeast PA with highest amount over
higher terrain and in the Poconos/Sullivan County. The rest of
central NY even our northern areas around Syracuse had 2-5" of snow
with the latest HRRR.
The 00z NAM 4-7" in northeast PA/Catskills, 3-5" in southern tier
and 2-4" farther north in central NY.
The 18z Canadian had 3-6" in northeast PA and 2-5" southern tier and
1-2" farther north to the Finger lakes.
So we see no big reason to change significantly change snow amounts
as 18z guidance is in line with going forecast. Just added more snow
between 06 and 12z Thursday. But offset this a bit so as to not
change total snowfall in northeast PA.
355 PM update...
Widespread sunshine allowed temperatures to in the lower
elevations in the Southern Tier and NE PA to climb up into the
upper-20s this afternoon. Some lake effect clouds and a few
flurries persisted further to the north. Some flurries will be
possible into early this evening over the northern Finger Lakes
and wrapping around in the Syracuse and Tug Hill Plateau areas.
While clouds will begin to increase from southwest to northeast
over night, dry air and a mostly clear start will allow
temperatures to drop off pretty quickly. Single digits and
perhaps a few below-zero readings will be possible by early
morning over Oneida County.
Increasing isentropic lift ahead of the approaching system will
allow light snow to overspread NE PA before dawn, but the onset
time of snowfall may struggle north of the NY/PA border as
precip fights drier air. Snowfall looks likely by the AM commute
in NE PA, but we`ll be right on the edge in the Southern Tier.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY/...
355 PM update...
Light snow will continue to slowly progress northward Thursday
morning, as isentropic lift steepens across the area. Meanwhile,
a series of shortwave troughs embedded in southwesterly flow
aloft will move up the east coast, with weak surface lows
developing just offshore. None of the shortwaves are
particularly strong, and none of the surface lows really get to
take off as the stronger northern stream trough remains well
back over the western Great Lakes. Later Thursday, 850-700 mb
frontogenesis band associated with a weak coastal low will slide
off just to our south and east, and we may see a bit of a lull
in the light snowfall over much of the area, especially the
further west you go. Much of our anticipated event total
snowfall (especially northwest of the NE PA and the Cats)
depends on subsequent waves moving up the eastern seaboard. The
NAM and GFS continue to be more generous over our area Thursday
night into Friday, while the Canadian and Euro are more stingy.
The former models are a little stronger with the the shortwave
troughs coming up from the southwest, and develop a slightly
stronger low at the surface to around 700 mb. The stronger lift
allows for another band of snow to flare up Thu night into
Friday, perhaps lingering over the eastern part of the CWA well
into the afternoon. I leaned a little towards the NCEP model
solutions here, though the 12Z GFS ensembles still suggests
about an even split. Without the expected Thursday night/Friday
flare- up, snowfall amounts near, north, and west of BGM might
only end up in the 1 to 3 inch range.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
400 PM Update:
A west-northwesterly flow will develop behind the departing storm
system Friday night. This will lead to lake enhanced snow as
moisture wraps around. This will be mainly concentrated along and
north of the NY Thruway corridor, before shifting southward towards
the Finger Lakes region the second half of the night. Lows Friday
night will likely be in the mid teens to lower 20s.
Continued lake effect snow showers are expected on Saturday,
especially across the Finger Lakes region. Otherwise, mostly cloudy
skies with highs in the mid to upper 20s are expected. High pressure
approaches from the west Saturday night, which will gradually end
any lingering lake effect snow showers. This high pressure system
will lead to quiet weather on Sunday with partly sunny skies and
highs in the upper 20s to lower 30s.
Clouds increase from west to east Sunday night ahead of the next
system. A shortwave trough sweeps across the Central US and into the
Northeast, bringing snow to the area late Sunday night through
Monday. As temperatures increase above freezing throughout the day
on Monday, rain may mix in with the snow, especially in the valley
locations.
Another shortwave is expected to quickly move through the area on
Tuesday, likely bringing another round of a mix of rain and snow.
Highs Tuesday are currently expected to be in the mid 30s to lower
40s. Then a weak lake effect response is expected Tuesday night into
Wednesday.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
VFR conditions expected at all terminals through the early
morning hours Thursday. A storm system will bring quickly
deteriorating conditions with light snow from south to north
beginning Thursday morning for KAVP, KBGM, KELM, and KITH and
Thursday afternoon for KSYR and KRME. An earlier arriving
snowband for KAVP could bring visibility down to below airport
minimums during the early morning hours. KAVP, KBGM, KELM, and
KITH will see below alternate minimum restrictions by Thursday
afternoon as snowfall becomes more widespread. KSYR drops to
IFR late in the TAF period, and KELM will only fall to MVFR.
Confidence remains fairly high that all terminals will see light
snow during this period.
Outlook...
Thursday afternoon through Friday...Snow and associated
restrictions likely from a passing storm system.
Friday night through Saturday...System lifts out Friday night,
but then lake effect snow showers appear likely for several NY
terminals.
Sunday...Mainly VFR
Monday...Another system will likely bring light snow and
associated restrictions.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...Winter Weather Advisory from 3 AM Thursday to 7 PM EST Friday
for PAZ040-048-072.
Winter Weather Advisory from 3 AM Thursday to 1 PM EST Friday
for PAZ038-039.
Winter Weather Advisory from 1 AM Thursday to 1 PM EST Friday
for PAZ043-044-047.
NY...Winter Weather Advisory from 3 AM Thursday to 7 PM EST Friday
for NYZ062.
Winter Weather Advisory from 6 AM Thursday to 1 PM EST Friday
for NYZ024-055-056.
Winter Weather Advisory from 6 AM Thursday to 7 PM EST Friday
for NYZ057.
&&
$$
SYNOPSIS...MPH
NEAR TERM...DJN/MPH
SHORT TERM...MPH
LONG TERM...BJG/TAC
AVIATION...BTL
Area Forecast Discussion
National Weather Service El Paso TX/Santa Teresa NM
437 PM MST Wed Feb 17 2021
.AVIATION...00Z TAF CYCLE
Generally VFR conditions are expected for most locations through
the period. However a passing disturbance this evening, overnight,
and into the morning hours will create opportunity for brief and
isolated MVFR to IRF conditions with isolated to scattered snow
showers. The best probability is over the mountains across the
Gila region and the Sacramento Mountains, as well as the lowlands
between. The only terminal expecting precipitation this evening
and overnight is TCS between 23Z- 10Z when -SN will be possible
with brief VIS reductions to 2SM. CIGs for most of the area will
be 080-120, with lower CIGs to 030-040 in any showers. West/
northwest surface winds at 14-18G24-28KT will subside and become
northerly through the 03-08Z period.
&&
.PREV DISCUSSION...205 PM MST Wed Feb 17 2021...
.SYNOPSIS...
An upper level disturbance will move across the Rocky Mountains
today and tonight. This system will bring a few rain and snow
showers to the region this afternoon and tonight along with chilly
below normal temperatures Thursday and Friday. Westerly winds will
produce warmer dry weather Saturday before another disturbance
brings breezy to windy conditions Sunday with cooler temperatures
again Monday. Warmer dry weather is forecasted for next Tuesday
and Wednesday.
&&
.DISCUSSION...
.SHORT TERM...Rest of Today through Thursday...
A secondary shortwave has rotated down along the backside of the
weather system that we saw yesterday across the Borderland. Radar at
the noon hour shows light scattered showers popping up across a good
portion of the area, with quite a spread of cumulus clouds
developing across the entire CWA. This is considerably more coverage
than what the high resolution models have been showing all morning.
The HRRR and NAM all kept the precip confined the mountains and
perhaps the northern lowlands. The only exception is the very latest
HRRR run which does now show a handful of spotty showers in Dona Ana
and Otero County. Mesoanalysis shows a few hundred J/kg of CAPE over
most of the Borderland, which is also different than the earlier
model solutions that kept CAPE focused in the northwestern third of
the CWA. Dewpoints are also a bit higher than what models thought
they would be. Looking aloft, we do have a strong 500mb jet skirting
around the Borderland today, which is likely helping develop these
afternoon pop ups. Expect coverage to remain more scattered in
nature, with the best chances for precip in the mountains and
lowlands east of the Continental Divide. Radar may look scarier that
what`s actually happening since some of these echos may just be
virga and not actual rainfall reaching the ground. Either way, most
areas shouldn`t be surprised if they see a few sprinkles on their
windshields through the afternoon. Since there is a bit of CAPE and
LIs are forecast to fall below 0 in spots, a rumble of thunder or
two will also be possible during daytime heating. The lowland
showers will remain as rain since temperatures are in the mid to
upper 40s to even some lower 50s, with mountains likely seeing snow
thanks to temps right around freezing.
What models do agree on is any lowland activity diminishing as we
get closer to sunset, then focusing the remainder of the precip over
the Gila region and Sacramento Mountains. Once we lose the heating
of the day, snow levels will start to drop to 3500-4000 feet. Again,
models have most of the precip confined to the mountains at this
time, but if any moisture does linger across the lowlands, some
spots may see a rain/snow mix or perhaps some light flurries. No
accumulations are anticipated in the lowlands. Rain amounts are
expected to remain below 0.10". It looks as though the precip will
linger in the Sacramento Mountains longer then originally thought,
so the Sacs could see light snow showers all the way through mid-day
Thursday before the precip finally exits the area. When all is said
and done, the Sacramento Mountains and Gila region may see up to an
inch or two of snow accumulation. Winds this afternoon have become a
bit gusty, though not as strong as we saw yesterday. These winds are
forecast to subside after sunset and gradually become
north/northeasterly overnight as the backdoor cold front tries to
make a short move west once again. Low temperatures will be below
freezing for most everyone, and the Sacramento Mountains and Gila
region will likely fall into the low teens to single digits thanks
to the dense snow pack on the ground. Winds will remain easterly on
Thursday, and clouds will clear out by the afternoon. With
north/northwesterly flow aloft and easterly flow at the surface,
temperatures will take a small tumble tomorrow, as forecast highs
will be in the mid to upper 40s.
&&
32 Pegram
.LONG TERM...Thursday Night through next Wednesday.
By Thursday evening far west Texas and southern New Mexico will be
located between deep upper trough in the plains and high amplitude
ridge west of the divide. This will place the region in a deep
subsiding northwest flow with transport of dry but cool air mass.
So expect cold below normal morning lows Friday with high
temperatures on Friday also around 10 degrees below normal
despite the sunny skies.
Westerly winds will advect dry but warmer air by Saturday pushing
temperatures up to a little above normal. However a rather strong
upper wave will move eastward into the central and southern rockies
on Sunday. This system will cause low and mid level gradients to
strengthen causing breezy to windy conditions across portions of
the CWA. In addition an associated Pacific cold front will move
across the CWA causing temperatures to cool around 5 degrees
Sunday with slightly below normal temperatures on Monday. Despite
strong upward forcing this system will lack sufficient moisture
for significant rain or snow.
Westerly winds will sustain dry weather conditions and produce
warming temperatures next Tuesday and Wednesday.
&&
.FIRE WEATHER...
A few lowland rain showers and mountain snow showers will be
possible through the afternoon and into the late evening hours. A
couple of isolated lightning strikes will be possible mainly in the
Gila region and Sierra County this afternoon, though a strike in the
rest of the lowlands can`t be ruled out. The Sacramento Mountains
will see snow linger through mid-day Thursday before all of the
moisture finally exits the area. Snow amounts in the mountains will
be 0.5-2 inches, and scattered rain amounts in the lowlands will be
below 0.10". Gusty northwest winds will subside and become northerly
overnight. Expecting light northeasterly winds on Thursday with cool
temperatures. Min RHs this afternoon and tomorrow will be above 25-
35 percent, with 18-22 percent in NM fire zone 111.
The Borderland will dry out for Friday and into early next week as
westerly flow takes over. Aside from warming temperatures and
patches of high clouds passing through, it will be a benign weather
period. Min RHs will drop below 20 percent starting Friday. A weak
trough may skirt the area on Sunday creating breezy northwesterly
winds. Will have to watch this day for a chance of critical fire
weather conditions as min RHs will drop into critical thresholds.
Vent rates will be poor to fair Thursday and Friday, then good to
very good Saturday and excellent on Sunday.
&&
32 Pegram
&&
.PRELIMINARY POINT TEMPS/POPS...
El Paso 32 47 25 55 / 10 0 0 0
Sierra Blanca 27 37 21 51 / 20 10 0 0
Las Cruces 28 46 22 54 / 10 0 0 0
Alamogordo 23 42 19 52 / 20 10 0 0
Cloudcroft 10 23 9 34 / 30 30 0 0
Truth or Consequences 27 46 23 54 / 40 0 0 0
Silver City 21 42 22 53 / 10 0 0 0
Deming 24 48 20 56 / 0 0 0 0
Lordsburg 23 50 22 58 / 0 0 0 0
West El Paso Metro 33 47 28 55 / 10 0 0 0
Dell City 24 39 16 53 / 30 20 0 0
Fort Hancock 29 44 20 57 / 20 0 0 0
Loma Linda 27 39 23 48 / 10 0 0 0
Fabens 30 47 23 56 / 10 0 0 0
Santa Teresa 28 46 22 53 / 10 0 0 0
White Sands HQ 30 45 27 53 / 10 0 0 0
Jornada Range 24 45 21 53 / 10 0 0 0
Hatch 27 48 22 56 / 10 0 0 0
Columbus 29 49 24 56 / 0 0 0 0
Orogrande 26 43 19 51 / 20 10 0 0
Mayhill 14 31 13 48 / 30 30 0 0
Mescalero 13 32 10 43 / 30 30 0 0
Timberon 12 29 9 42 / 30 30 0 0
Winston 12 40 11 53 / 30 0 0 0
Hillsboro 22 44 19 56 / 20 0 0 0
Spaceport 24 44 20 53 / 30 0 0 0
Lake Roberts 14 40 15 54 / 30 0 0 0
Hurley 18 45 17 54 / 0 0 0 0
Cliff 22 49 21 58 / 0 0 0 0
Mule Creek 21 45 24 55 / 20 0 0 0
Faywood 24 45 23 54 / 0 0 0 0
Animas 24 50 21 60 / 0 0 0 0
Hachita 22 50 19 58 / 0 0 0 0
Antelope Wells 26 49 24 58 / 20 0 0 0
Cloverdale 28 47 28 58 / 10 0 0 0
&&
.EPZ WATCHES/WARNINGS/ADVISORIES...
NM...None.
TX...None.
&&
$$
32/05/14
AREA FORECAST DISCUSSION
National Weather Service Morristown TN
1005 PM EST Wed Feb 17 2021
.UPDATE...
EVENING UPDATE.
&&
.DISCUSSION...
Doppler radar and surface observations indicate that precip has
begun reaching the ground across the southern Plateau and
southern Valley, and we have received public reports of sleet in
Cleveland and 0.3 inches of snow in Whitwell. The potential for
snow and sleet will spread north and east through Midnight as
isentropic upglide continues to strengthen along with
strengthening warm, moist advection ahead of the approaching
shortwave. Surface temps are generally in the mid 30`s to near 40,
but dew points in the 20`s will lead to evaporative cooling as
the airmass saturates, which will support the wintry precip. RAP
soundings show a warm nose developing near 850 mb as WAA
increases, so snow/sleet mix will gradually change to more of a
sleet scenario then eventually all rain as the warmer air makes it
back to the surface. This will occur fairly quickly from S to N,
and the HREF precip types support this idea with much of the S
Plateau and S Valley through SW NC expected to be rain by 07Z
while the middle Valley changes to rain in the 07-09Z timeframe
and the N Plateau through the N Valley and NE TN into SW VA
changes to rain in the 09-12Z timeframe (perhaps later in SW VA).
The previous forecast and headlines look good, so the only change
was to issue an SPS for Bradley, McMinn, NW Monroe, and W Polk
Counties through 07Z to cover the current mixed precip.
Garuckas
&&
.AVIATION...
00Z TAF DISCUSSION.
Showers will overspread the TAF sites this evening with periods
of MVFR first developing at CHA then reaching TYS and TRI late
this evening or early tonight. Cigs and vis will fall to
primarily IFR with periods of MVFR overnight as precipitation
becomes steadier. A mix of snow and sleet will occur at TYS and
TRI before dawn with light accumulations possible before changing
to all rain Thursday morning. Showers will become more scattered
Thursday, but reduced cigs and vis will prevail much of the day.
Garuckas
&&
.PREV DISCUSSION...
/ISSUED 349 PM EST Wed Feb 17 2021/
SHORT TERM...(This Evening through Thursday)...
Key Messages...
1) A wintry mix of snow, sleet, and possibly freezing rain Plateau
and Mountains can be expected across the region from this evening
through early Thursday morning. Wintry mix will transition to all
rain by around daybreak Thursday. Greatest accumulations from the
Plateau, northeast Tennessee into southwest Virginia.
2) Very challenging forecast on precipitation type.
Initial precipitation will be influenced by wet bulb cooling due
to dry airmass and eventually strong dynamic forcing between
04-09Z. However, models also depict strong strong warm air
advection/isentropic lift which will fight to change precipitation
to rain. Model soundings show warm air winning out over most of
the area by daybreak.
3) The strong system will also produce widespread rainfall
amounts of 1 to 1 1/2 inches with localized 2 inches+. Given the
soggy soil conditions, most of this will be runoff which may cause
some localized flooding issues.
4) Temperatures warming into the 40s across much of the valley
Thursday with another round of rain with frontal passage in the
afternoon.
Now for the particulars...
For this evening and tonight, strong jet structure will move
across the Tennessee valley and southern Appalachians. Some models
are so a 300mb jet of 165-170kts over the Ohio valley. Models show
very strong upper divergence with the jet configuration between
04-09Z. The Ageostrophic Vertical Circulation with the jet will
produce dynamic cooling as well as the wet bulb cooling due to
initial dry airmass.
A period of heavy snow (some sleet) is possible across the
Plateau, western sections of the Tennessee valley, northeast
Tennessee, and southwest Virginia. The strong warm air advection
and isentropic lift will produce widespread precipitation.
Eventually the warm air advection will win out with model
soundings show precipitation transitioning to rain area-wide soon
after daybreak.
For Thursday, the strong dyanmics will move east of the area with
a break in the widespread precipitation ending by mid-morning.
However, another wave of jet energy and frontal passage will
produce another round of rain in the afternoon.
LONG TERM...(Thursday night through Tuesday)...
By Thursday night the precipitation will be pulling out to the
northeast as the strong trough over the central US begins to finally
swing through into the eastern half of the country. Have trimmed
back precipitation chances Thursday night into Friday as some models
are speeding up the exit of the precip. If precipitation is able to
linger into the early overnight hours Thursday night temperatures
will drop enough that we could see another round of light snow.
Accumulations with any snow Thursday night and Friday morning are
expected to be very light if they do occur as the moisture will be
mostly gone and QPF should be light.
We`ll finally take a break from wintery precipitation over the
weekend, with the biggest story being cold temperatures in the
morning, specifically Saturday morning. This will be the time when
the cold air from the northwest will have the greatest impact and
low temperatures are expected to be in the low 20`s into the teens
across all of the area. Winds are expected to be light as the
surface high begins to build in with winds likely remaining below 5
mph, so am not anticipating a wind chill advisory being needed. But
these will still be some of the coldest temperatures of the season
regardless.
Trough begins to weaken it`s grip and with the drier air from the
west/northwest we`ll actually get to see the sun for the majority of
the weekend. This will help with a warming trend and temperatures
are expected to finally warm up into the 50`s on Sunday, although
we`re still going to be running a few degrees below normal it`s
probably going to feel very nice out in the sun.
Another trough and front are expected to quickly swing through the
area early in the week on Monday. Models have trended a bit colder
with this system from previous runs so we could see a bit of snow in
the higher elevations Monday morning mixed in with the rain (which
should be the dominant precipitation type). This system will quickly
move through and we get back to a warming trend behind it. The
current forecast calls for temps in the upper 50`s and possibly 60`s
(and sunny) on Wednesday.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 34 45 29 42 22 / 100 60 20 10 0
Knoxville McGhee Tyson Airport, TN 33 42 30 38 21 / 100 90 40 10 0
Oak Ridge, TN 33 43 28 38 20 / 100 70 30 10 0
Tri Cities Airport, TN 32 43 31 37 19 / 100 100 60 20 0
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...Winter Weather Advisory until 7 AM EST Thursday for Cherokee-
Clay.
TN...Winter Storm Warning until 1 PM EST Thursday for Anderson-Blount
Smoky Mountains-Campbell-Claiborne-Cocke Smoky Mountains-
Hancock-Hawkins-Johnson-Morgan-Scott-Sevier Smoky Mountains-
Southeast Carter-Southeast Greene-Southeast Monroe-Unicoi-
Union.
Winter Weather Advisory until 7 AM EST Thursday for East Polk-
Grainger-Hamblen-Hamilton-Jefferson-Knox-Loudon-Meigs-North
Sevier-Northwest Blount-Northwest Cocke-Rhea-Roane.
Winter Weather Advisory until 10 AM EST Thursday for Northwest
Carter-Northwest Greene-Sullivan-Washington.
Winter Storm Warning until 9 AM CST Thursday for Bledsoe-Marion-
Sequatchie.
VA...Winter Storm Warning until 1 PM EST Thursday for Lee-Russell-
Scott-Washington-Wise.
&&
$$
Area Forecast Discussion
National Weather Service Pendleton OR
756 PM PST Wed Feb 17 2021
.SHORT TERM...Tonight and Thursday...A ridge of high pressure will
be passing over the region tonight ahead of the next weather system
expected to move off the Pacific Thursday in a westerly flow. Will
see some increasing clouds overnight and the potential for some
patchy fog around the Columbia Basin. Precipitation will begin move
over the Cascades late in the morning then impact the entire
forecast area through the afternoon and evening. The westerly flow
will somewhat shelter the Cascade east slopes and Basin with the
least precipitation while the Cascade crest and eastern mountains
will see the most. Winter Weather Advisories have been issued
covering Thursday afternoon through midday Friday for the Cascades
and northern Blue Mountains. There will also be the potential for
some freezing rain in portions of the Columbia Basin Thursday night.
&&
.PREV DISCUSSION... /issued 215 PM PST Wed Feb 17 2021/
SHORT TERM...Tonight through Friday night...WSR-88D continues to
pick up weak returns over the Blues and Wallowas, so will keep
isolated snow showers or snow flurries for this area through the
evening. Otherwise, no precipitation is expected through early
Thursday morning. Patchy dense freezing fog was observed this
morning in the Tri-Cities area, and believe the areal coverage
will be greater tonight. This is supported by the HRRR visibility
progs that show fog as far south as the Lower Columbia Basin of
Oregon and near Prosser as well as the eastern Columbia River
Gorge. Southerly downslope winds along the Blue Mtn Foothills may
keep this area fog free tonight.
A shortwave trough will travel across WA/OR Thursday and Thursday
night. There is a weak warm front associated with the trough that
will increase snow levels to around 3000 feet over eastern OR and
far southern WA but only around 1500-2000 feet for areas north of
the Tri-Cities and Prosser. Precipitation will develop along the
Cascades early Thursday morning then gradually spread eastward
over the remainder of the forecast area Thursday afternoon and
evening. One forecast challenge has been whether there may be
light freezing rain or sleet over the Columbia Basin where
persistent fog and low clouds may keep temperatures just around
the freezing mark. Using the NBM Conditional Probability for
-FZRA as a guideline, will introduce a chance of freezing rain for
the Lower Columbia Basin from the Tri-Cities south to the Blue
Mountain Foothills. Confidence isn`t high to go likely, but a
chance. The wintry mix will not last long as a westerly flow will
follow the shortwave trough which is not favorable for
precipitation across the Columbia Basin and surrounding valleys.
Winter Weather Advisories are in effect for the east slopes of the
WA/OR Cascades and the northern Blue Mountains from Thursday
morning through Friday afternoon. There will be a prolonged
period of a westerly flow Friday and Friday night bringing
numerous snow showers in the advisory locations. The Wallowa
Valley, Grande Ronde Valley, and the Ochoco-John Day Highlands
will likely receive 1-3 inches of snow which do not meet advisory
criteria. The lower elevations, including Central Oregon, will
have up to 1 inch of new snow.
No wind concerns during the short term, although it will be windy
in the Grande Ronde Valley Thursday and Thursday night. Wister
LONG TERM...Saturday through Wednesday...A progressive pattern
with an overall west to northwest flow will prevail through much
of the extended period. On Saturday a weak trough will move across
the area in a northwest flow, which will cause mainly upslope
mountain snow and occasional light valley rain or snow. QPF
amounts are not too impressive with this disturbance, but there
could be a substantial amount of upslope snow in the northeast
mountains, and the Cascades, especially near the crest. Then on
Sunday weak upper ridging will develop. However, there will be a
shortwave trough that will move in and flatten the ridge by
afternoon. There will still be some lingering upslope mountain
snow showers. This pattern will persist through Monday night. Then
a westerly jet stream will increase over the PacNW with a faster
zonal flow on Tuesday. During this time, the upslope snow showers
over the northeast mountains will taper off and end, and the flow
over the Cascades will bring some spill over precipitation near
the crest. Elsewhere will be dry. A new trough will then develop
and amplify with the trough axis over areas west of the Cascades
in OR/WA on Wednesday. The dynamic lift with the associated
vorticity advection and increased moisture with the trough will
cause precipitation to develop again in the eastern and northeast
mountains. Precipitation will increase over Oregon, but the
northern areas will stay mostly dry (mainly the WA Lower Columbia
Basin, and the Yakima/Kittitas Valleys). There will be a warming
trend Saturday through Monday, with Monday peaking out in the 40s
and 50s...and then temperatures will cool slightly after that. It
will be breezy to locally windy through most of the extended
period due to the fast progressive flow pattern. The longer range
models are in pretty good agreement through the extended period
with each other and with the various ensembles. 88
AVIATION...00Z TAFs...VFR conditions will prevail this evening
at all terminals. However, there could be periods of low clouds
and light fog over KALW, KPSC and KYKM. Flying conditions will
deteriorate on Thursday afternoon from west to east as another
weather system moves into the region, with periods of MVFR and
possible IFR conditions as clouds lower and visibility decreases
in precipitation at all terminals. The exception will be at KPSC
and KYKM which will be in the drier northern areas. Winds will be
light tonight and under 5-10 kts, but a southeast gradient will
cause winds to increase along the Blue Mountains and Foothills and
also in the Ochoco-John Day highlands with possibly locally
breezy winds by late Thursday afternoon. 88
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 24 36 33 42 / 0 30 70 20
ALW 26 37 33 43 / 0 20 70 30
PSC 25 34 29 43 / 0 40 60 10
YKM 26 34 25 42 / 0 60 50 10
HRI 26 36 31 44 / 0 40 70 10
ELN 26 32 27 41 / 0 60 50 20
RDM 21 41 31 44 / 0 70 60 20
LGD 18 33 31 40 / 0 30 80 50
GCD 19 39 32 45 / 0 60 90 30
DLS 32 36 35 47 / 0 90 70 30
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory from 10 AM Thursday to 1 PM PST Friday
for ORZ502-509.
WA...Winter Weather Advisory from 10 AM Thursday to 1 PM PST Friday
for WAZ030-520.
&&
$$
SHORT TERM...91
LONG TERM....91
AVIATION...74
Area Forecast Discussion...UPDATED
National Weather Service Shreveport LA
945 PM CST Wed Feb 17 2021
.UPDATE...
The significant winter storm has now exited the entirety of the
Four State region and has laid down significant accumulations of
snow, and/or sleet, and/or ice (depending on where you live). We
are becoming increasingly confident the deeper baroclinic zone
aloft (925 to 700 mb) will juxtapose with the right entrance
region of a strong upper level jet to squeeze out an additional
light wintry mix (mainly fzra/snow) from late tonight and possibly
into early afternoon from mainly Deep East Texas into North and
Central LA and the Arklamiss. Additional ice and/or snow
accumulations are possible in these areas, but they should be very
light. Nevertheless, any additional accumulations will ensure
already bad travel conditions will not be improving at all. For
the above reasoning, the prior Winter Storm Warning in effect for
the whole region through midday tomorrow was kept going in
outlined areas where additional wintry precipitation is possible.
However, since no additional wintry precipitation is anticipated
northwest of the outlined zones, we have canceled the Winter Storm
Warning in Arklatex zones basically along and northwest of the
I-30 corridor. Of course most of those areas are already covered
with snow and impacts from this locally heavy snow will continue
and travel will be treacherous. Otherwise, low temperatures were
lowered in most areas tonight to match trends and will range from
the upper teens northwest to upper 20s southeast.
Stay safe and try to stay warm everyone. Warmer and sunnier times
are eventually coming. /50/
&&
.PREV DISCUSSION... /issued 645 PM CST Wed Feb 17 2021/
AVIATION...
IFR cigs will persist across much of the region through the
overnight hours, with areas of a wintry mix expected to diminish
through 03Z across Srn AR/N LA. However, additional snow and ice
accumulations are expected at the TXK and ELD terminals, with
lighter icing accumulations at MLU. Some slow improvements to cigs
are expected overnight across portions of NE TX/SW AR with MVFR
cigs returning, although this improvement is not expected for
areas farther SE until mid/late morning through the afternoon
Thursday. However, areas of a light wintry mix may redevelop late
tonight through much of the morning Thursday across portions of
Deep E TX into NCntrl LA, possibly affecting the LFK/MLU
terminals. However, any additional icing will be minimal over
these areas. Conditions will continue to improve gradually late in
the TAF period and beyond, although MVFR cigs looks to hang on for
a better part of the day before lifting/scattering out. NNE winds
6-10kts will continue through the end of the TAF period. /15/
PREV DISCUSSION... /issued 413 PM CST Wed Feb 17 2021/
SHORT TERM.../Today through Thursday Night/
The 2nd winter storm of the week has been fully impacting the
Four State Region today, but will be winding down from southwest
to northeast through late afternoon into early this evening. Some
of the snow amounts, in particular, have been very impressive
across AR portions of the CWA and we will be doing reports through
the evening to highlight event totals, so look for those. Even
though there will be a relatively quick downward trend in activity
over the next handful of hours, there could still be lingering
light FZRA potential tonight in portions of the region, although
recent model runs have made this seemed less likely. The final
portion of trough energy may also squeeze out some more very light
freezing drizzle or flurries tomorrow in the region, but any
additional impact from this is also looking far less likely. The
current Winter Storm Warning does not expire until noon tomorrow
to cover those lingering threats and we may cancel the warning
early later this evening, choosing not to change parameters of the
warning right now to avoid confusion when the event is still
ongoing.
Otherwise, the HRRR model has been doing a pretty good job handling
the mixed precipitation details pretty well with mostly sleet,
occasionally heavy, in a tight corridor from GGG, to SHV, to ELD -
with mostly snow north of this corridor and mostly FZRA south of
this corridor. We have also seen some slight shift north of these
pcpn type boundaries this afternoon, although not a great deal of
further change is expected before most everything exits to the
east/northeast later this evening. Additional ice accumulations
(from freezing rain) of up to a quarter inch are probably more
limited to Central Louisiana with additional snow accumulations
greater than 2 inches probably more limited southwestern AR. Less
additional snow/sleet/frza rain accumulations are expected
elsewhere according to p-type boundaries described above.
Interestingly, temperatures warmed far above model expectations
in central portions of the CWA where latent heating processes at
the surface due to freezing rain have warmed temperatures to, or
near, freezing. But these areas will likely not get above freezing
before starting to fall off again tonight. Locations across Deep
East TX and Central LA have just barely topped the freezing mark,
but will fall below freezing again tonight.
For tomorrow, a solid reinforcement of below normal temperatures
will be coming in the wake of this system and some patchy and
light wintry pcpn types could accompany this in at least SE
portion of the CWA, as alluded to above. There should be at least
some patchy sunshine by afternoon in the northwestern half of the
CWA juxtaposed with temperatures probably a little above freezing
and, if this occurs, would get a touch of melting going on. But
roads will remain a mess in most areas as lows tomorrow night
should be in the chilly teens in most areas and will efficiently
freeze any liquid or slush on road surfaces. A hard freeze
warning will be considered for future package covering tomorrow
night, but we decided to hold off on that product for now to keep
the message simple. /50/
LONG TERM.../Friday through Wednesday night/
Friday morning will see a 1036mb high over the Rio Grande valley
that will slowly edge eastward and weaken down to 1030mb or so in E
TX by nightfall. We are still looking at loads of lingering ice
getting into the weekend with more record lows perhaps to start and
then highs on Friday only in the low to mid 30s with sunshine
helping to melt ice off structures anyway.
The weekend will be chilly to start with more mid to upper teens,
but rebounding on Saturday as winds shift to southerly on the back
side of this still 1030mb air mass axis crossing the MS river. High
temps on Saturday will get into the lower 40s north of I-20 and
upper 40s south. Then the clouds will begin to increase overnight
into early Sunday blanketing in more heat and keeping lows closer to
average for late February.
The clouds will continue lowering during the mid to late day with
highs ranging from near 50 north to 60 south. Most of us along I-20
only in the lower 50s with rain not far behind the clouds for I-30
in the afternoon and then spreading down area-wide by nightfall.
This is a weaker Pacific airmass of 1028mb that will push another
cool front through overnight Sunday. The upper trough arriving
overnight will be cooling temps aloft which will allow for a brief
window for a mix to end predawn, mainly along and north of I-20.
This will only be how the overnight light rainfall ends, due to
timing of predawn hour and the drier NW flow deepening under the
passing trough. NO additional ice accumulation is expected anywhere
in our area with this few hour window of transistion before quickly
ending. Hopefully travel will have greatly improved over the weekend
and this tail end trace will not affect that process in the least,
as we continue with sfc winds the will back from NW to SW late in
the day. The rest of the work week look very nice with average 60s
for highs and 40s for lows and southwest winds and sunshine. /24/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 23 34 18 37 / 20 30 0 0
MLU 26 33 19 36 / 40 40 0 0
DEQ 19 37 11 36 / 20 10 0 0
TXK 22 35 14 34 / 40 10 0 0
ELD 21 34 15 36 / 60 20 0 0
TYR 21 33 13 32 / 10 10 0 0
GGG 21 34 14 35 / 20 20 0 0
LFK 25 36 19 40 / 30 30 0 0
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...Winter Storm Warning until noon CST Thursday for ARZ060-061-
070>073.
LA...Winter Storm Warning until noon CST Thursday for LAZ001>006-
010>014-017>022.
OK...None.
TX...Winter Storm Warning until noon CST Thursday for TXZ112-125-126-
136>138-149>153-165>167.
&&
$$
50/15/24