Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/16/21
Area Forecast Discussion
National Weather Service Green Bay WI
524 PM CST Mon Feb 15 2021
Updated aviation portion for 00Z TAF issuance
.SHORT TERM...Tonight and Tuesday
Issued at 230 PM CST Mon Feb 15 2021
Partly sunny skies prevailed across the region this afternoon.
It was still very cold with readings in the single digits above
zero, except at Marinette/Menominee where it was 11 degrees.
For tonight, have posted a wind chill headline for portions of
central and north-central Wisconsin. Decided to add northern
Marinette and northern Oconto Counties to the wind chill advisory
after running the numbers. Lows tonight will range from a few
degrees above near Lake Michigan to near 25 below zero across
Attention then turns to the lake effect potential tonight for
portions of east-central Wisconsin, especially Manitowoc County.
The meso models having a lake effect snow band set up this
evening offshore and then heads westward towards the shoreline
late this evening and overnight. Latest meso models still give
several solutions on how far west the lake band will get which
will have a significant impact on snowfall totals. To complicate
matters, the latest HRRR keeps the most intense portion of the
band remains offshore and pointed towards Sheboygan County. Did
contemplate upgrading to a warning, but the above mentioned
concerns will result in the Winter Weather Advisory remaining in
place for now. If the main portion of the band sets up across
eastern Manitowoc County like the ARW model would suggest, totals
could be considerably higher which would prompt an upgrade to a
winter storm warning. Will pass on concerns to the evening shift.
Any lingering snow across east-central Wisconsin will gradually
end tomorrow as winds turn more northerly than northeast like
tonight. Highs will be mainly in the teens to around 20, which
will seem fairly balmy after the last several days.
.LONG TERM...Tuesday Night Through Monday
Issued at 230 PM CST Mon Feb 15 2021
Cold weather will linger into Tuesday night, but a gradual
moderation in temperatures is anticipated through the week, with
highs reaching the upper 20s to lower 30 by Sunday, and lower to
middle 30s by Monday.
Have kept small pops for lake-effect snow showers from Wednesday
afternoon through Thursday, as winds maintain an easterly
component off Lake Michigan. A short-wave trough may bring some
light snow showers or flurries Thursday night into Friday,
especially in eastern WI.
Models show big differences with a low pressure system moving
through the region on Sunday. The GFS has a strong low moving
through WI, and bringing heavy snow to much of GRB CWA. The ECMWF
is much weaker and farther south, and suggests perhaps an inch or
two of snow in the southeast part of the forecast area.
Probabilistic forecast information supports the weaker solution,
so will just mention chance pops for much of the region for now.
.AVIATION...for 00Z TAF Issuance
Issued at 524 PM CST Mon Feb 15 2021
VFR conditions will continue through Tuesday for all the TAF sites
except MTW and locations along Lake Michigan. The lower flying
conditions will be a result of lake effect clouds and a lake
effect snow band moving onshore late this evening and overnight.
Ceilings will likely drop to MVFR/IFR while visibilities drop
below a mile at times in the heaviest snow band. Intermittent
light lake effect snow will likely linger through at least mid
Wind Chill Advisory until 10 AM CST Tuesday for WIZ005-010>013-
Winter Weather Advisory until noon CST Tuesday for WIZ050.
Area Forecast Discussion
National Weather Service Lincoln IL
937 PM CST Mon Feb 15 2021
Issued at 307 PM CST Mon Feb 15 2021
Moderate to at times heavy snow will continue through this evening
and eventually taper off to flurries overnight tonight.
Temperatures will be cold tonight, falling into the single digits
and even below zero is some locations near the Illinois River
Valley. Temperatures will warm into the teens Tuesday under partly
to mostly cloudy skies.
Issued at 937 PM CST Mon Feb 15 2021
Tweaked the grids some tonight. Looks like the snow will be
tapering off. However, not going to change any of the headlines at
this time due to the blowing and drifting snow that will continue
through the night. Update will be out shortly.
.SHORT TERM...(This evening through Tuesday)
ISSUED AT 307 PM CST Mon Feb 15 2021
Snow is ongoing and increasing in intensity this afternoon across
central Illinois. Water vapor imagery reveals a negatively tilted
shortwave lifting across portions of mid Mississippi Valley,
ejecting out ahead of main upper low centered over eastern KS.
Snow is expected to peak across the area through around midnight
tonight when the H5 low finally begins to shift across central
Illinois marking the back edge of the accumulating snow.
No major changes to the going forecast made this afternoon with
the heaviest snow still expected to be focused over the eastern
part of the state. From this afternoon through tonight, in
addition to snow that fell last night into this morning, an
additional 3 to 6 inches of snow is possible along the Illinois
River Valley (under the Winter Weather Advisory), 4 to 8 inches
from the I-55 to I-57 corridors, and 6 to 10 inches east of I-57.
Latest RAP does depict a modest layer of FGen over east central
Illinois and regional radar does show a couple bands of heavier
snow lifting north. Does seem the better banding potential will be
through the remainder of the afternoon and then will diminish
with time this evening. Under the heavier bands, visibility less
than a quarter mile and snow rates of around an inch per hour or
slightly higher are possible, at least briefly.
Meanwhile, winds will remain breezy out of the north through at
least midnight tonight with gusts of 20 to 30 mph. Winds should
begin to taper slowly after midnight, but in the meantime the
breezy north winds will result in blowing and drifting of snow,
especially on east-west oriented roads. Given the high snow to
liquid ratio (20+:1), snow is expected to shift pretty easily
.LONG TERM...(Tuesday night through Monday)
ISSUED AT 307 PM CST Mon Feb 15 2021
Expect a brief break in snowfall on Tuesday. Low pressure will
exit east towards New England Tuesday while expansive ridge
spreads south from the Upper Midwest along the Mississippi River
Valley. This ridge axis will shift across Illinois late Tuesday
evening. Temperatures remain bitterly cold with highs only in the
teens then lows Tuesday night dipping into the single digits and
just below zero in some spots. Cloud cover and its impacts on
temps will be the primary area of uncertainty Tuesday night. While
there may be a window of clearing skies Tuesday evening resulting
in otherwise very favorable radiational cooling conditions with
fresh snow pack and light winds, do expect clouds to increase
from the SW overnight which will help to prevent temps from really
Wednesday into Thursday, a strong shortwave will round the base
of a deep upper trough centered over the Great Plains and lift
northeast across the lower to mid Mississippi Valley. There
remains quite a bit of model spread on the evolution of this
system, but in general guidance depicts an elongated trough of low
pressure centered over the Deep South that lifts northeast along
the Appalachians. Models are in generally good agreement that an
initial warm advection driven wing of precip will overspread
central Illinois Wednesday. Differences grow quickly thereafter
with some models (GFS, ECMWF) placing the bulk of the deformation
axis snow well to our east while others (NAM, GEM) bring heavier
snow across central Illinois.
Confidence further out increases again as models indicate another
strong high building across the Great Plains Friday and Saturday.
Dry weather is expected to prevail during this time. Temps remain
bitterly cold Friday, but should moderate Saturday as the ridge
axis shifts east and return flow spreads across the Midwest in its
wake. Some locations could see temps near or above freezing by
this weekend, especially on Sunday into early next week.
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 544 PM CST Mon Feb 15 2021
LIFR and VLIFR conditions will continue this evening as moderate
to heavy snow continues at all sites. As the system lifts ENE the
back end of the heavies snowfall will end around midnight. So
will increase vis and cigs a little bit but still seeing IFR
conditions. Conditions will improve quickly and expecting VCSH
during the overnight hours at all sties with cigs just above 1kft.
MVFR cigs will continue tomorrow at all sites but should become
broken in the late morning through afternoon. Winds will be
northerly through most of the period at 10-15kts. Winds will
become northwest tomorrow at around 10kts.
Winter Storm Warning until 6 AM CST Tuesday for ILZ038-042>046-
Winter Weather Advisory until 6 AM CST Tuesday for ILZ027>031-
Area Forecast Discussion
National Weather Service Indianapolis IN
1008 PM EST Mon Feb 15 2021
The NEAR TERM Section has been updated below.
Issued at 247 PM EST Mon Feb 15 2021
Heavy snow has returned to central Indiana and will continue
through the evening before tapering off after midnight. Snow will
continue to blow around through the day tomorrow with the next
round of wintry weather arriving Wednesday night into Thursday.
Dry and warmer weather then looks to return late in the weekend
into early next week.
.NEAR TERM /Overnight/...
Issued at 1009 PM EST Mon Feb 15 2021
Surface analysis shows deep low pressure in place over eastern
Kentucky. Cold arctic high pressure remained in place over
Minnesota. Cold and gusty north winds were the result across the
forecast area as strong pressure gradient remained in place. Radar
shows the back edge of the expected snowfall approaching
Vincennes...pushing northeast. Water vapor imagery is impressive
this evening with an upper low found over MO and some dry air
working into the system over Wrn TN...Wrn KY and SW Indiana. Best
forcing is now pushing much farther north of Indiana across the
southern Great Lakes. Radar trends still suggest the next few
hours will continue with persistent snow and wind as we have seen
the past few hours as the dry air and subsidence arrives across
Thus will expect another 1-2 more inches of snow as the last part
of this system begins to depart. We have had reports and seen many
pictures of significant drifting. This is expected to continue
overnight particularly across more rural areas as the pressure
gradient is expected to remain in place. Snow drifts of 2ft or
more will be common...continuing to keep travel difficult. Ongoing
Winter Storm warning will remain.
.SHORT TERM /Tuesday and Tuesday Night/...
Issued at 247 PM EST Mon Feb 15 2021
Blowing snow will continue into the day tomorrow with lessening
impacts later in the day as snow will have come to an end. The
upper level system that brought all this snow will rapidly exit
the area with a brief break in the winter weather through tomorrow
and tomorrow night. With a thick snowpack, expect temperatures to
struggle to break out out of the teens tomorrow before crashing
into the low single digits to below zero tomorrow night with
partly cloudy skies at the beginning of the night. Clouds though
will increase towards sunrise which should limit the fall.
.LONG TERM /Wednesday through Monday/...
Issued at 247 PM EST Mon Feb 15 2021
As the long term begins a longwave trough will be in place over the
western plains with a broad upper ridge over the Atlantic. The
trough will progress eastward, and as it does so, will pull a
surface low out of the Gulf and bring it northeastward. The latest
operational guidance shows a fair amount of variability with the
surface low track, and this lowers overall confidence in the
forecast for this system. The upper trough looks more broad than
yesterday`s runs, and this should produce weaker but more
prolonged forcing over the area. Isentropic lift moves into place
Wednesday afternoon and could continue into Wednesday night, with
access to a good feed of Gulf moisture on southerly 850 mb winds
of 20 to 30 kts. Favorable jet streak dynamics may also be in play
on Wednesday night, contributing additional upper forcing into
the mix. On Thursday upper forcing in the way of q vector
convergence will move through, there are indications in some
solutions that a TROWAL could set up somewhere in the vicinity of
Ohio or Indiana (although other solutions take the feature further
north). At this time the best potential for heavy snow appears to
be across the central and southeastern counties, and
probabilistic output indicates greater than 30% chance for 6
inches of storm total snow by Friday morning across the
High pressure will slide through the area and bring dry weather with
it Friday through Saturday night. Temperatures will remain below
normal on Friday through Saturday with the snow pack in place and
the base of the upper trough of cold air moving through. Wind chills
Friday night/Saturday morning could again approach 10 below zero.
A bit of a warm up will be possible starting Sunday. Could see
temperatures climb above freezing at that time. Early indications
are that another system could move through Sunday into Monday, so
will include some low chances for precipitation then, but confidence
is low given the variability in models that far out.
.AVIATION /Discussion for the 160000 Tafs/...
Issued at 558 PM EST Mon Feb 15 2021
IMPACTS: IFR or worse conditions are expected for the next 6-9
hours. Improvement to VFR is expected by the end of the Taf
DISCUSSION: Radar Mosaics across the area show a large band of
snow...limiting visibilities to 1/4 mile or less along with CIGS
less than 1000ft stretching from the Taf sites across Southern IL
to Western Kentucky. This precipitation is expected to continue
to track to the northeast over the next 6 hours...resulting in a
continuation of the IFR conditions. Deformation band set up is
also possible which could result in some higher snowfall rates.
HRRR remains on board lifting this precipitation across the
forecast area through the next 6-8 hours...resulting in very poor
As the Low and upper trough begin to exit the area overnight the
precipitation should begin to end...leading to improving
visibilities but plenty of MVFR to IFR CIGS will remain across the
area as Time height and forecast soundings continue to reveal
saturation within the lower levels.
Subsidence and drying is depicted within the column as surface
high pressure build across the area on Tuesday. Thus will expect a
gradual return to VFR on Tuesday late morning.
CONFIDENCE: High confidence for IFR conditions this evening and
Winter Storm Warning until 7 AM EST Tuesday for INZ021-028>031-
Area Forecast Discussion...CORRECTED
National Weather Service Chicago/Romeoville, IL
836 PM CST Mon Feb 15 2021
812 PM CST
Not sure what`s left to be said that hasn`t already, but our
remarkable snowstorm (considering the magnitude of the arctic
airmass in place) is essentially heading into its peak at this
time, with snowfall rates maximizing here probably through about
midnight to 2 AM. The axis of steadiest snowfall has set up shop
roughly east of a Mendota to McHenry line. Lake enhancement is and
has been ongoing for a few hours with strong confluence noted
with buoys showing northeast winds gusting to 30-35 mph, with
northwesterlies just inland. The cooperative observer near Midway
recently reported an exceptional 2.9 inches of snow in just about
100 minutes. Think the writing is on the wall at this point given
radar trends that the jackpot area for this event will probably be
2-3 miles either side of a roughly Winnetka/Evanston to Midway
line. When all is said an done (after lingering lake effect
diminishes later tomorrow afternoon), imagine we`ll see a handful
of snowfall reports pushing 20 inches in this corridor.
The going forecast is in good shape, but did nudge overall amounts
through the rest of the night upwards a bit based on recently-
observed amounts and reported SLRs.
With winds routinely gusting to around 25-30 mph, have also
increased our blowing snow wording, especially near the immediate
lakefront areas, as well as across more of our open/rural areas,
with these effects most notable on east-west oriented roadways.
Snowfall rates as a whole look to start diminishing towards 2-4
AM, with any snow of consequence ending across northwest and
north-central portions of Illinois around/by daybreak. Steady
lake-enhanced snowfall will likely continue through Tuesday
morning, and may not full come to an end until early tomorrow
evening, although rates during the afternoon will be considerable
No changes to the winter headlines at this time. The message is:
don`t be out tonight unless it`s unavoidable. Updated products
329 PM CST
Through Tuesday night...
Bottom line up front...Be prepared for a very messy evening commute,
heavy snow tonight, with impacts expected to linger into the morning
commute even though the heaviest snow will fall before daybreak
Tuesday. Hazardous road conditions and low visibility will be the
main concerns and will arrive very quickly late this afternoon and
evening. This snow will hit hard and fast.
This is certainly one heck of a system, and also impressive in the
southern extent with readings in some areas over the Gulf of Mexico
at or below freezing! Synoptic snow from the main storm system is
knocking at our door as a strong upper level jet pushes into
Indiana. This will place most of the area in the left exit region
(and even some jet coupling from the northern stream jet) combined
with significant upper level height falls will allow the still
blossoming snow shield to spread in. Visibility values across most
of the southern half of Illinois below three-quarters of mile, many
areas much lower. Many areas upstream of here easily reached 6" of
snow in the heart of this system. Expect the worst conditions
tonight and into the early overnight hours. We will maintain a
decent pressure gradient on the back side of the associated surface
low, thus blowing snow will be a concern. It is still quite unusual
to get such a high QPF system with these really cold temperatures,
so the snow will fluffy and blow around easily, which has already
occurred at O`hare and will become a higher concern in rural
With regards to lake effect/lake enhancement, RAP forecast of
convergence suggests that the main band across central Cook county,
possibly smack dab between O`Hare and Midway (likely to include
Midway airport) and will likely remain the focus of the lake band
into this evening. Eventually it will become masked in the broader
snow shield, but expect this only to further reduce visibility, with
some locations earlier reporting visibility no more than a city
And while wind chill values have "improved", values of 0 to minus
20, with the lowest readings west of the Chicago, are still
significant, thus caution is urged if outside. We did decide that
it was prudent to expand the Winter Weather Advisory through the
remainder of the area as impacts should be similar across north
central Illinois in spite of possibly slightly lower snow amounts.
With this light snow, expect blowing snow concerns to linger in
rural areas into Tuesday morning, thus we wanted to message this
concern as well, along with the cold temperatures.
So when will this all end? The main system snow should be done by
daybreak in most areas, though it will be slower to exit near the
lake. It should generally be shifting east of Chicago after mid-
morning with the focus in northwest Indiana from mid morning onward.
We envision that lake effect will linger across northwest Indiana
longer than the current warning is in effect (9AM CST), so the night
shift will need to assess whether we will need to extend this.
Breezy northwest winds will continue the drifting snow for open
areas most of the day.
High pressure will shift into the area Tuesday night. We could drop
temperatures pretty fast in the evening out ahead of any incoming
mid level clouds. Ensemble guidance has areas in north central
Illinois possibly getting down to -10F temperatures, with below zero
lows likely area-wide.
329 PM CST
Wednesday through Sunday...
Majority of the previous shift discussion is still valid through the
Focus in the extended forecast remains primarily on another synoptic
snow-producing system Wednesday through Thursday night.
Another mid-level wave rounds the base of the long wave upper trough
over the western CONUS during the day Wednesday, which is progged to
eventually lift out to the northeast cross the upper Ohio Valley and
far eastern Great Lakes region through late Thursday. This continues
to be a complex evolution involving a couple of northern stream
disturbances within the trough across the upper Midwest, and as such
continues to produce some spread in model solutions. The general
consensus is that the surface low with this system will track from
the Louisiana coast northeast into the upper Ohio upper Ohio Valley
and eastern Lakes, with the heaviest QPF southeast of the forecast
area through the Ohio Valley and eastern Lakes. The GFS/Canadian and
their 00Z ensemble means continue to be slightly further to the
northwest with the precip shield and higher amounts than the 00Z EC
and EPS mean, similar to runs of 24 hours ago. NBM blended guidance
continues to favor the southeast half of the WFO LOT cwa for higher
pops Wednesday night into Thursday evening, and this remains
reasonable at this time, with some accumulating snow fairly likely.
Will of course need to continue to monitor this for a better handle
on amounts/locations over the next couple of days. Guidance also
continues to indicate some potential for lake effect snow across
especially northwest IN as the system departs Thursday night into
Models depict a flattening of the overall pattern at the end of the
week, as the deep trough associated with the mid-week storm
progresses off to the east. Rising mid-level heights and surface
high pressure are indicated across the area later Friday into
Saturday, with the coldest 850 mb air also exiting off to the
northeast. This would support a moderation in temperatures over the
below-average conditions we`ve experienced of late. There`s also
indications of another wave moving into the region Sunday, with some
additional snow or rain/snow mix potential as temperatures warm.
For the 00Z TAFs...
557 PM...Primary forecast concerns include...
Moderate/heavy snow through early Tuesday morning.
Strong/gusty northerly winds with blowing snow tonight.
A lake effect snow band extends from just east of ord/pwk to mdw.
Visibilities are 1/4sm in this band and this lake effect band is
likely to continue this evening as moderate snow spreads across
the entire area. Still some uncertainty for exactly how fast the
snow will taper off but high confidence for an improving trend by
daybreak. There will likely still be some lake effect snow showers
near ord/mdw at daybreak, possibly just east of those airports
but once this shifts east, that should be the end of the snow with
the rest of Tuesday dry, with perhaps some flurries.
Northerly winds will gust into the mid 20kt range this evening
and slowly diminish overnight. Wind directions at ord/mdw will
likely fluctuation either side of north as the lake effect band
drifts near those sites. Wind directions should favor north/
northwest Tuesday morning and then more northwest Tuesday
afternoon/evening with speeds diminishing under 10kts with sunset
Tuesday evening. cms
IL...Winter Storm Warning...ILZ013-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-
ILZ039-ILZ106-ILZ107-ILZ108 until 9 AM Tuesday.
Winter Storm Warning...ILZ006-ILZ103-ILZ104-ILZ105 until noon
Winter Weather Advisory...ILZ003-ILZ004-ILZ005-ILZ008-ILZ010-
ILZ011-ILZ012-ILZ019 until 9 AM Tuesday.
IN...Winter Storm Warning...INZ001-INZ002-INZ010-INZ011-INZ019 until
9 AM Tuesday.
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AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
925 PM EST Mon Feb 15 2021
An area of low pressure and immediately preceding warm front will
track from the Gulf of Mexico northward across the eastern Carolinas
and middle Atlantic coast tonight. Cool high pressure will follow
for Tuesday and Wednesday.
.NEAR TERM /THROUGH TONIGHT/...
As of 925 PM Monday...
Surface analysis show a 1003mb surface low near Morristown TN and
associated wedge and warm fronts drape south and east across SC and
GA, respectively, while 00Z regional raobs show the strong CAD
inversion from GSO to MHX. Radar imagery suggests one MCV moving
through the foothills, with another over central SC in closer
proximity to airmass boundaries, which should be where the secondary
wave of low pressure begins to track toward the eastern Piedmont and
coastal plain overnight. There has been a very slow
north/northwestward mixing of the warm sector airmass, with 60F
dewpoints barely into the Savannah River Basin as of 01Z. An area
of showers extends from the western Piedmont south through the GA
coast, with pockets of fairly impressive lightning frequency,
suggest elevated CAPE above the LLJ and warm nose. As expected the
intensity of these storms has waned as they move north and become
more elevated. The window for any near surface based convection
still looks very short centered around 06Z when 60F dewpoints make a
run at the southern coastal plain, and recent HRRR runs have shown a
southeastward trend wrt stronger surface-based convection. As
such, there is not much to changed in the current forecast, as
observed trends have matched pretty well.
There could be some concern for isolated flooding in the coastal
plain urban areas where better convective rates could develop, but
it appears the line of convection is moving a decent clip and
should limit QPF to less than 0.75" on average. -bls
Previous discussion: Thanks to ongoing CAD, low clouds, fog and
drizzle will persist through the evening. Then we turn our
attention to the low pressure center moving up out of the northern
GOM and across the NC Piedmont overnight tonight...accompanied by
strengthening winds aloft ahead of the short wave trough lifting NE
across the Miss and OH Valleys. The latest CAMs continue to depict
rain showers, some with heavy downpours, overspreading and sweeping
across central NC from west to east between 03Z and 09Z tonight.
While the CAD and cool near-sfc layer will hold firm across the
region west of the US-1 corridor (which is coincident with the track
of the sfc low), forecast soundings show the potential for at least
some elevated instability, and given the increasing deep layer bulk
shear in excess of 50kts, we can`t rule out some elevated thunder
with hail being the main concern, particularly from US-1 eastward.
East of the low track (basically east the US-1 corridor)...sfc temps
will climb pretty quickly after 04z, but even still, enough of a low
level inversion will persist to preclude a sfc connection to
instability. Rather, it appears that the only place where a sfc
connection could be established is near the immediate coast.
Nevertheless, it`s a vigorous system, so heavy downpours, a few
gusty thunderstorms east of US-1, and potentially one or two with
some large hail, is a possibility overnight. Temps tonight will
hold steady west of US-1 and rise east of US-1 as the sfc low lifts
.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
As of 304 PM Monday...
The showers and tstms will be pushing off the east coast by 12 or
13Z. Behind that, low clouds will be slow to erode across the
western Piedmont and Triad since the existing CAD airmass will still
be in place (given the low passing by the east). However, from US-1
east, clouds should begin to thin out before noon and there may even
be some sunshine by afternoon. Even across the Triad, some sun may
break out by mid-late afternoon. Otherwise, CAA in the low levels
will result in steep lapse rates in that layer, so it will become
rather breezy if not windy at times thanks to good momentum transfer
below H9. Frequent wind gusts up around 20kt can be expected during
the daytime Tuesday. The steep low level lapse rates may also
manifest in some stratocu up around H8 by mid to late afternoon, so
any clearing in the early afternoon may be short-lived. With CAA
underway, temps will slowly fall during the day through the 50s and
40s (or simply remaining in the 40s across the Triad), then continue
to fall Tuesday night under mostly clear skies and lighter winds.
Lows Tuesday night from the mid 20s NW to around 30 SE.
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 415 PM Monday...
Wednesday will be a welcomed dry day with partly sunny skies as high
pressure noses in from the north over SE Canada. This CAD regime
will result in well-below-normal temperatures, and leaned toward the
cooler NAM with highs in the 40s across the area. This dryness will
be short-lived, however, as yet another shortwave trough digs south
into the southern Plains on Wednesday night and moves into the Deep
South on Thursday. At the surface, a low pressure system will
develop along the Gulf Coast and move northeast along a quasi-
stationary frontal boundary, with another low developing off the Mid-
Atlantic coast. This will bring more widespread precipitation to
central NC from Wednesday night into Friday morning. The heaviest
precipitation will likely come in two rounds, the first being from
isentropic lift overnight Wednesday night into Thursday morning, and
confidence continues to be high enough for categorical POPs.
Confluence between the approaching upper trough and the weakened
polar vortex over SE Canada will keep the ~1035 mb mb surface high
in place over New England during this period, which looks
increasingly likely to result in temperatures just cold enough (30-
32F) for a period of freezing rain in the far northern Piedmont on
Thursday morning. The main threat area appears to be similar to the
last event, along and north of I-85. Elsewhere only rain is expected.
Models still show the high pressure system then retreating north,
which will result in temperatures rising above freezing everywhere
by late morning Thursday and only liquid precipitation for the rest
of the event. The good news is the above-freezing temperatures
combined with plenty more precipitation should help to melt whatever
ice does accrue in the far north. A warm front with a very sharp
temperature gradient (60s to the south and 30s-40s to the north)
will try to lift into the area, which makes for a challenging
temperature forecast on Thursday. As is often the case, the cold
dense air at the surface will likely be very difficult to scour out,
and both the GFS and ECMWF continue to trend colder for Thursday.
The 12z NAM actually trended warmer and brings the wedge boundary
well north into the area, but this is not supported by other
guidance and continue to lean toward the colder solutions at this
time, with the boundary not getting past the Coastal Plain.
Precipitation coverage should lessen somewhat during the day
Thursday, especially in the far south and east. While deep-layer
shear looks quite prolific (60-80 kts), continue to leave out any
mention of thunder at this time with the cooler trend of most model
guidance and the likely lack of enough instability. Any convection
if it were to develop would be elevated with the best chance in the
far south and east. Another band of heavier rain associated with a
cold front will then move through from west to east Thursday night
into early Friday morning. Total forecast precipitation from the
system is currently one and a half to two inches across central NC,
highest north where the strongest 500 mb height falls will be. This
would be enough for more flooding issues especially with rivers and
streams already running high.
Westerly flow behind the cold front will result in rapidly
decreasing rain chances and clearing skies from west to east on
Friday morning and afternoon. High pressure will finally result in
some dry weather and clear skies for the weekend. Saturday will be
cooler than normal with highs in the 40s and lows in the 20s, before
the high moves offshore on Sunday and Monday resulting in
temperatures moderating into the 50s. Both the GFS and ECMWF are in
good agreement that the next shortwave trough will move into the
Great Lakes on Monday, with a trailing cold front bringing
precipitation to the area, so introduced low chance POPs on Monday.
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 700 PM Monday...
LIFR conditions will hold across most of central NC overnight owing
to a strong wedge airmass in place. Showers associated with a low
pressure system that will track across the eastern Piedmont and
coastal plain have begun to move into the vicinity of GSO/INT as of
00Z, and these will shift east overnight, with a thunderstorm
possible at any site between 02-08Z, earlier at GSO/INT and later at
RDU/FAY/RWI. However, the probability of strong winds in the storms
is low, especially at GSO/INT/RDU.
In the wake of the departing showers and storms early Tuesday, low
clouds an LIFR to IFR conditions will linger through at least mid-
morning, and potentially into the early afternoon at GSO/INT, with
westerly winds slowly eroding the low clouds and eventually gusting
to 20-25kt during the afternoon.
Outlook: VFR conditions may briefly return for Wednesday, before
the next weather system approaches Wednesday night, bringing another
round of IFR or less flt conditions Thursday through early Friday.
Also note the possibly of freezing rain at INT/GSO late Wed night
through mid-day Thursday, before changing to rain. Flight
conditions should improve again late Friday and Saturday.
Area Forecast Discussion
National Weather Service Blacksburg VA
957 PM EST Mon Feb 15 2021
Low pressure will move across the southeast tonight giving us
mainly rain. Colder high pressure builds in behind this system
Tuesday, followed by another winter storm impacting us by
Wednesday night.Drier conditions are expected to return for
the weekend ahead.
.NEAR TERM /THROUGH TUESDAY/...
As of 930 PM EST Monday...
...Some rumbles of thunder overnight give way to breezy conditions
and some breaks of sun for some Tuesday...
Subtle changes in regards to temperatures, precipitation
chances ,winds, and visibility for the overnight period.
Heaviest rain and a few rumbles of thunder have been confined in and
east of the Blue Ridge Parkway this evening. Waves of moisture
continue to funnel in from the south out of Greensboro-Winston Salem
as our storm system quickly lifts north. Not much wind can be found
so far with any of our rain despite a jet core humming along at 30-
60 knots 4000-7000 feet off the surface. Some gusty winds of 20-40
mph have been noted in elevations above 3500 feet with an occasional
gusts upwards of 50 mph across the highest peaks of the North
Carolina mountains this evening. Any winds will slowly subside after
midnight once the system passes before re-energizing again late
Tuesday morning into Tuesday afternoon as the pressure gradient
As for precipitation expect any moderate rain to slowly taper during
the wee hours of Tuesday morning east of the Blue Ridge. Some
freezing rain may also mix along the parkway leading to a light
glaze although impacts look to be minimal. Elsewhere around the
region light rain, drizzle, mist, and low clouds will linger into
the early morning commute so allow some extra time heading off to
work and school. Some fog may also be out there as well but with
winds picking up late in the mid morning period that may not be
likely. Hi-res guidance along with model soundings also seem to be
on that point of thinking for the early morning period.
A westerly component to the wind means that many locations from
Roanoke to Lynchburg back south to Blacksburg and Danville may
actually see that giant orange ball know as the sun pop out in the
skies tomorrow. Downsloping will be in play which will allow us to
scrub out some of the gray and gloom for a little blue above. It
won`t be all that much but maybe just enough to force highs into the
mid to upper 40s along the Blue Ridge with low to mid 50s over the
Piedmont/Southside. Further west the colder air will remain
entrenched with highs in the mid to upper 30s and low 40s underneath
more of those gray skies.
Confidence remains average to above average in the near term.
As of 530 PM EST Monday...
Heavy rain moves in this evening/tonight with a brief dry stretch
and some hints of sunshine for some Tuesday..
Minor changes in regards to precipitation timing and winds this
evening as our next weather maker moves.
A nice band of moderate to heavy rain is already showing up on radar
from Cincinnati, Ohio back south to , Tennessee. This band
will continue to pivot north and east into our region tonight giving
us once again another night of miserable weather conditions. Out
ahead of this band winds have been gusting 15-30 mph with a good
downsloping effect along our western facing slopes warming temps in
Richlands toward 50 degrees. Further east the air is lot
cooler/stabler with temps 33-37 degrees under a layer of dense fog.
The fog should scrub out once the rain overspreads the area from
west to east between 7pm-9pm this evening. Even with that said
expect pockets of poor visibility to continue through the overnight
hours with extra ponding on the roadways. The heaviest rain looks to
remain in two corridors one against the western facing slopes with
the low crossing along the Ohio River and the other out over the
Piedmont with the main surface low pushing up through the central
NC/eastern VA into the Delmarva by early Tuesday morning. Rainfall
amounts will be on the order of a quarter of an inch to half an inch
west of the I-81 corridor with a half an inch to one inch along the
crest of Blue Ridge points east into the Piedmont. Locally heavier
amounts are possible from the North Carolina Piedmont points north
along and east of US-29 corridor where even a little thunder cannot
be ruled out thanks to some elevated instability due in part to bulk
deep layer shear values humming between 30-50 knots.
Flooding does not look to be a concern with this event with the
exception of a few poor drainage areas maybe running into some
issues. We will continue to keep an eye on the Dan river though
at South Boston which crested below minor flood stage earlier
today based upon the heavy precip set to move in.
Any wintry weather this evening will remain north of the I-64
corridor and along the Blue Ridge Parkway where a period of
light freezing rain could occur. Accumulations will be less than
a few one hundreths in these locations so no advisories have
been issued at this time but a mention has been made in the HWO.
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 230 PM EST Monday...
Another winter storm may bring an icy mess starting Wednesday night.
Upslope snow showers will linger across western Greenbrier County on
Tuesday night but should eventually fade by Wednesday morning. High
pressure should cross over the southern Great Lakes on Wednesday to
bring drier conditions. However, it will wedge southward along the
eastern slopes of the Appalachian Mountains by Wednesday afternoon
into Wednesday night. Meanwhile, a low pressure system should
organize over the Gulf Coast and move northeastward toward the Mid
Atlantic. A deep upper level trough will crave itself over the
central Plains, while an upper level ridge persists off the East
Coast. As a result, the moisture fetch from the Gulf of Mexico will
ensue on Wednesday night and persist through Thursday night.
It almost looks like a repeat of the ice storm experienced this past
Sunday with all the models showing a strong warm nose lifting
northward over a cold wedge of high pressure in the lowest layers of
the atmosphere. The biggest difference this time is that the high
will be in a more ideal location to promote wedging as it will be
centered over New York on Wednesday night. Precipitation may start
as a mix of snow and sleet along and west of the Blue Ridge with
rain changing over to a wintry mix in the Piedmont. By Thursday,
most locations may see freezing rain as model soundings show the
warm nose reaching up to +10 C by the afternoon. The ice
accumulations appear noteworthy, which is a significant concern
given how much the Virginia Piedmont is still recovering from the
previous ice storm with downed trees and power lines. The freezing
rain will slowly change to rain from south to north as surface
temperatures struggle to climb above freezing during Thursday
afternoon. However, some of the moisture could turn back into sleet
or snow as colder air arrives from the northwest on Thursday night.
.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 230 PM EST Monday...
Mountain snow showers, gusty winds, and cold air will persist
through Friday and Saturday.
Cold air behind the departing low pressure system will arrive by
Friday morning. Winds will become gusty from the northwest, and
upslope snow showers should crank up along a line from Boone to
Lewisburg. Meanwhile, conditions should become dry across the
Piedmont. The ECMWF and the GFS models agree on keeping the gusty
winds and mountain snow showers through Friday night into early
Saturday. Temperatures were steered toward the colder side of
guidance, and there may be a few locations testing wind chill
advisory criteria by Saturday morning. High pressure will build
overhead on Saturday afternoon, which should allow the gusty winds
and the mountain snow showers to gradually diminish.
With high pressure in control by Saturday night, our weather will
finally turn tranquil after an extremely active and wet week. Sunday
should see the flow turn around to the southwest, so temperatures
could turn somewhat milder as the upper level pattern flattens. By
Sunday night, a shortwave trough will cross over the central Plains
and approach the Mid Atlantic by Monday morning. A weak low pressure
system associated with this trough should bring the next chance of
precipitation. This system should exit offshore on Monday evening.
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
As of 717 PM EST Monday...
Light to moderate rain will continue to overspread much of the area
this evening as an area of low pressure and it`s aforementioned
front move through. Areas west of KBLF, KBKW, and KLWB look to see
ice from this system while areas east of KAVL, KCLT, KGSO, and KDAN
look to see thunderstorms. This has been noted on the current radar
east of KCLT where several lightning strikes have occurred in the
last hour or so. With that said have opted to leave a tempo group
out for TSRA at KDAN at this time but may reevaluate based on radar
trends in the coming hours.
Elsewhere it`s predominantly IFR to LIFR cigs/vsbys especially out
over the mountains as our system moves moves through. As for icing
concerns they look to remain minimal. KLWB may see some according
to the hi-res soundings between now and 6z Tuesday otherwise most of
the icing will remain from KCRW, KHTS, and KEKN points west along
with the crest of the Blue Ridge Parkway.
Low level wind shear will remain an issue through the early evening
hours according to the NAM nest and HRRR for KBLF, KLWB, and KTNB
before settling down after 6z Tuesday as the low level jet core
Improving conditions for our Tuesday at all the TAF sites although
winds will remain gusty out the west at 10-20 knots. Some upslope
snow showers may also be noted Tuesday morning into Tuesday
afternoon west of KLWB and KBLF but do not look to provide any major
impacts at these TAF locations at this time. Elsewhere expect a MVFR
conditions with some brief periods of VFR cigs/vsbys at KROA, KLYH,
and KDAN by Tuesday afternoon.
Above average confidence for ceilings, wind, weather. Average to
slightly below average confidence on visibility and concern for
Extended Aviation Discussion...
Weather pattern is forecast to remain unsettled through Friday
with increasing threat for wintry precipitation Wed night-Friday as
Arctic air surges further southeast into the eastern United
States. Generally MVFR or worse conditions expected through most
of the entire period.
The KFCX radar will be down through about Thursday, February 18
for the replacement of a generator as well as other electrical
components powering the facility. In addition, the Richlands
NOAA weather radio broadcast will be off the air through at
least Tuesday, February 16 due to phone line problems.