Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/01/21

Area Forecast Discussion...UPDATED

National Weather Service Aberdeen SD

 525 PM CST Thu Dec 31 2020

.UPDATE...
Issued at 524 PM CST Thu Dec 31 2020

The forecast is on track this evening. No major changes are
planned.

&&

.SHORT TERM...(This Evening through Friday Night)
Issued at 157 PM CST Thu Dec 31 2020

Forecast challenges revolve around downslope wind potential tonight,
and temperatures.

Currently, under a mostly sunny sky, temperatures are warming
through the teens and 20s on a light southerly wind, east of the
Missouri River valley. West of the valley, temperatures are noted
warming into the 30s on west-southwesterly winds.

The biggest concern right now in the short term is how strong can
downslope winds become overnight tonight. Fresh snow on the ground
is blowable. So if sustained winds reach 30 to 35 mph with gusts to
45 mph or higher, there will be some spots along I-29 and U.S.
Highway 12 in Roberts and Grant county that experience blowing snow
and potentially reduced visibility. The set-up is subtle and not
really ideal for downslope winds. There is some weak low level waa
happening overnight tonight and low level winds will have a west-
southwesterly direction. The HRRR continues to highlight some
stronger downslope winds developing (20 to 26 knots) after 7 PM CST
this evening, for several hours. Have bolstered the winds in the
Prairie Coteau`s downslope area and added blowing snow mention to
the weather grids.

By Friday morning, a weakening lee-of-the Rockies surface trof will
be working south and east of the CWA, turning winds around to the
west-northwest briefly on Friday. High pressure builds in during the
day, causing winds to gradually subside to calm or near calm. Friday
night, the next installment of lee-side surface trof begins to
deepen off to the west, signaling a switch in the winds back to a
southerly or southwesterly direction. Despite the ongoing weak
low level waa, high and low temperatures are not expected to
moderate from the most recent observed high and low temperatures all
that much between tonight and Friday night.

.LONG TERM...(Saturday through Thursday)
Issued at 157 PM CST Thu Dec 31 2020

Not much in the extended for impressive weather systems. Late
Saturday an upper trough passage will feature some cloud cover, very
little lift so if any precipitation does occur, it won`t be much
more then an isolated sprinkle or flurry, and blended guidance has
smoothed any precipitation out with this feature. It will bring in a
modified Pacific airmass, which will lead to temperatures above
average for Sunday and Monday. A clipper across southern Canada
Monday will draw cooler air in its wake, but really its just a
glancing shot for our area with more mild 850mb temperatures to
follow in its wake. The system that follows after that also appears
to be influenced by the split flow pattern and will have relatively
little impact on our region for the middle of next week aside from
clouds and winds picking up a little.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 524 PM CST Thu Dec 31 2020

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are expected to prevail through the period. There
could be a short period of restricted cigs/vsby near sunrise in
stratus/fog near KATY.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&

$$

UPDATE...Wise
SHORT TERM...Dorn
LONG TERM...Connelly
AVIATION...Wise



Area Forecast Discussion

National Weather Service Charleston SC

 1003 PM EST Thu Dec 31 2020

.SYNOPSIS...
A warm front will lift north of the area late tonight. A cold
front will impact the area late Friday through the weekend.
High pressure will return Monday and prevail through early next
week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
As expected, the stationary front has started to sink south late
this evening. Various mass fields from both the RAP and MSAS
show the front surged south across interior Southeast Georgia
over the past few hours with light northeast winds now being
reported at both Millen, GA (K2J5) and Metter, GA (KMHP).
Surface analysis at 01/02z showed the quasi-stationary front
was located roughly along a Saint Stephen-Harleyville-Hampton-
Oliver-Claxton-Collins line. Dense fog has started to rapidly
fill in behind the boundary with webcams out of Metter,
Vidalia, Claxton, Statesboro showing pretty widespread dense fog
with very low visibility. A Dense Fog Advisory has been issued
for much of interior Southeast Georgia as well as Allendale
County, SC, through 6 AM.

The front is still expected to sink closer to the lower South
Carolina coast later tonight. Dense fog should fill in behind
the front, but the redevelopment of showers over the Charleston
Tri-County area after midnight could keep dense fog from
becoming too widespread there. The better chances for dense fog
outside of the current advisory area should settle into Hampton
and Walterboro south to Beaufort and Hilton Head. South of I-16,
the front should not move too far south of there and only
patchy fog should occur there. Late evening reports from Hilton
Head (KHXD) and webcam images at sunset showed the patches of
sea fog just offshore. Guidance is similar in expanding the sea
fog along the far upper Georgia coast and into Hilton Head and
Beaufort later tonight. This could skirt parts of the Savannah
Metro Area. The fog is still expected to improve from south-
north prior to sunrise as the front lifts north as a warm front
so a 6 AM advisory expiration time looks reasonable, although
some areas could be cancelled prior to that.

The risk for isolated to scattered showers will linger through
the night, gradually shifting north of the area by daybreak with
the warm front. Temperatures will be some 20+ degrees above
normal, with lows ranging from the upper 50s across the interior
to around 60/low 60s elsewhere. These values put record high
minimums for January 1 in jeopardy.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
Friday (New Years Day): On Friday morning, most of the area should
remain rain-free as subsidence pushes onshore from Atlantic Coastal
waters. Though, a few light showers cannot be ruled out, mainly
inland and in the Charleston Tri-county as a coastal trough departs
the area. Lingering areas of fog is possible in the morning, mainly
in SE GA and in the GA nearshore waters. Fog could be dense in areas
with visibilities 1/2 mile or less. WAA over the marine waters could
advect sea fog on land along the GA coast maintaining low
visibilities. A surface low meandering near the ArkLaTex will finally
push northeast shifting the cold front eastward closer to the
region. Latest models show the cold front approaching Friday
evening, before stalling just as it reaches our forecast area as the
occlusion process dominates the surface low over the Midwest. SPC
has kept our far inland counties in a Marginal Risk for severe
thunderstorms and areas closer to the coast in general thunder.
Models indicate a line of storms just ahead of the front weakening
as they approach our most western counties as the front slows and
weakens. An isolated strong to severe thunderstorm could occur in
this high shear/low CAPE environment; however, storms should remain
limited to these inland counties as sfc forcing lessens; however,
showers could extend closer to the coast. Above normal temperatures
are expected with highs reaching the mid 70s over most of the region
and nearing 80F in southeast GA. Overnight, min temperatures will
only drop to the low 60s, nearing record high min territory.

Saturday: The front remains in place and weakens slightly via
persistent meridional flow as a secondary upper low develops within
the lingering upper trough. By the afternoon, a second H5 low
propagates over the Southern Appalachians, strengthening the front
as noted by strong 700 mb frontogenesis. With deep moisture in
place, rainfall will be more prominent with approximately 1-3"
forecast across the region, with higher amounts expected over the
inland counties. Locally higher amounts are possible within stronger
thunderstorms. SPC has the entire area outlooked in a Marginal Risk
for severe thunderstorms. The development of discrete cells are
possible due to 40-50 kt bulk shear. However, the severe potential
is on the low end as higher shear could overcome updrafts and limit
organization, due to minimal CAPE. Above normal temperatures are
expected again with highs reaching the low/mid 70s. Overnight temps
will gradually cool to the mid 50s.

Sunday: The front is expected to push offshore Sunday morning with
surface high pressure building into the region. The rest of Sunday
should be rain-free with clearing skies and breezy conditions in the
wake of the front. The strongest CAA is expected to occur late
afternoon as winds shift out of the northwest. While winds do not
look to exceed Lake Wind Advisory criteria, Lake Moultrie could have
occasional gusts up to 20 kt. High temperatures will be cooler, yet
remaining just above normal; in the 60s over the general area.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
High pressure will prevail through Wednesday and the area should
remain rain-free. Monday and Tuesday will be sunny before moisture
moves back into the area on Wednesday and cloud cover will increase.
High temperatures will be in the 60s. Lows will be in the 30s/40s
each night.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Shower activity near KCHS should largely pass north of the
terminal by 00z. No impacts are expected. Fog/stratus will
continue to be a concern at both KCHS and KSAV. The stationary
front across the interior is expected to meander south near both
terminals overnight before lifting north as a warm front prior
to daybreak Friday. Fog/stratus is expected to fall in near the
front, but with weak shower activity forecast to linger near
KCHS for much of the night, this may be enough to keep vsbys
from dropping too much. Opted to limit vsbys to MVFR 05-10z
along with IFR cigs. For KSAV, some clearing this evening ahead
of the front should promote a higher fog chance with chances
increasing as the front settles nearby. MVFR vsbys are expected
by 04z with IFR cigs/vsbys 06-09z before improving as the warm
front lifts north. Lowest conditions were handled in a TEMPO
Turin this time with vsbys below and cigs right at alternate
minimums. Some guidance suggest several hours of dense fog,
especially if winds tip northeast near the front and this will
have to be watched. Gusty winds will develop by mid-morning at
KSAV and early afternoon at KCHS.

Finally, low-level wind shear could impact KSAV from 04-09z.
Included WS020/18035kt during this time.

Extended Aviation Outlook: Flight restrictions possible in showers/t-
storms and early morning fog/stratus through the weekend.

&&

.MARINE...
KHXD has recently dropped to 1/4 mile and matches short term fog
guidance pretty well. NARRE-TL probabilities for dense fog
rapidly increase from Sapleo Sound to Edisto Beach out to
roughly 10 NM over the coming hours. Given this consistent trend
and the Charleston Harbor Pilot Boat recently reporting patches
of dense sea fog east of the Charleston Harbor, a Marine Dense
Fog Advisory has been issued for the Georgia and and far
southern South Carolina nearshore waters through 6 AM. Guidance
shows the best risk for dense sea fog holding south of
Charleston Harbor and the Charleston nearshore waters, but this
will have to be watched, especially if winds turn more south
than southeast as the warm front lifts north.

Tonight: Southerly winds will persist across the waters
tonight. Marine conditions should remain below Small Craft
Advisory criteria, with the exception being the Georgia offshore
waters where 6+ foot seas persist. The main concern will be the
potential for sea fog as warm, moist air moves over the cooler
shelf waters. Area webcams have shown some reduced visibilities,
and models indicate this trend should continue overnight.
Marine Dense Fog Advisories could be needed.

Friday through Tuesday: Southerly flow will prevail through early
weekend ahead of a cold front. Sea fog is possible Friday morning
through the afternoon over the nearshore waters with the advection
of much warmer air. Winds will shift out of the northwest Sunday as
the front finally pushes offshore. A Small Craft Advisory will
remain in effect through the period for the offshore Georgia waters
from 20nm to 60nm for seas greater than 6 ft and occasional wind
gusts over 25 kt. The nearshore waters could have occasional 6 ft
seas and wind gusts near 25 kt Saturday into Sunday where SCA`s
could be needed. Winds in the Charleston Harbor are forecast to
remain below SCA criteria. Marine conditions are expected to improve
Sunday night into early next week. Seas will drop to 3 ft or less by
Monday, and NW winds around 10-15 kt will prevail.

&&

.CLIMATE...
Record high minimum temperatures for Jan 1:
KCHS: 61/2019 and 1973
KSAV: 62/2019
KCXM: 62/2019

Record high minimum temperatures for Jan 2:
KCHS: 60/1985
KSAV: 66/2017
KCXM: 63/1985

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Dense Fog Advisory until 6 AM EST Friday for GAZ087-088-099-
     100-114-115.
SC...Dense Fog Advisory until 6 AM EST Friday for SCZ040.
MARINE...Dense Fog Advisory until 6 AM EST Friday for AMZ352-354.
     Small Craft Advisory until 2 PM EST Sunday for AMZ374.

&&

$$



AREA FORECAST DISCUSSION

National Weather Service Hastings NE

 531 PM CST Thu Dec 31 2020

.DISCUSSION...(This evening through Thursday)
Issued at 255 PM CST Thu Dec 31 2020

Main concern in the short term is potential for fog. Beyond that,
temps and low end pcpn chances become primary forecast challenges.

Not too bad out there today with full sunshine area wide, though
it is a bit chilly with the southerly breeze, at times. Latest
GOES WV imagery shows the area split between N stream well N of
the area, and active S stream with two potent vorticity lobes
noted - one over S CA, and the other over S TX. The mid level
speed max associated w/ TX vort lobe is beginning to round the
base of the trough, which will allow the trough to bec negatively
tilted as it lifts NE tonight into Fri AM. This system will have
an excellent tap to Gulf moisture, but it appears this will only
aid in production of widespread convection, which will likely help
"pull" the track of the trough a bit further SE than previously
expected. Models have trended this way, esp short term hi-res and
convective allowing models, so have pulled all PoPs from far SE
for tonight and Fri AM.

As far as potential for fog, HRRR and SREF continues to indicated
good potential for fog development tonight and into Fri AM, esp
for areas N of Hwy 6 and E of Hwy 283. This seems very reasonable
given lgt winds and likely at least some snow melt from this aftn
adding some moisture to the near-sfc boundary layer. Current Tds
are in low to mid 20s, so low temps in the teens to upper single
digits would be more than supportive from a crossover temp
perspective. BUFKIT data from RAP/HRRR also shows favorable
hydrolapse and MRi numbers. Have added some "dense fog" wording to
the grids. The potential for high cirrus to move in from the S
gives me just enough uncertainty to ramp it up more than that just
yet, but it`s certainly something the eve shift will need to
watch. Wouldn`t be surprised if parts of roughly N half of CWA
will need a dense fog advisory by dawn. Given what happened last
night, have trended temps down at least a few deg from guidance
for the favored cold areas of Dawson, Valley and Greeley Counties.

Shallow nature of fog and incr NW winds should allow for improving
conditions by mid to late Fri AM. Nrly winds and at least some
high clds will probably lead to slightly cooler high temps for New
Years Day, but overall, not too bad. May have to deal with fog yet
again Fri night into Sat AM as crossover temps are once again
favorable and winds look to go nearly calm under clr skies. SREF
probabilities are decent (50-70%) for vsbys <1sm. Debated incr
from the "Patchy" mention from prev shift, but felt best to
continue as is and reevaluate after we see what happens tonight.

Other than fog potential, the forecast is pretty quiet through the
weekend. The aforementioned CA vort lobe will probably take a
similar track to tonight`s system and remain SE of the area on Sat.
Models indicate a fast moving shortwave on the heels of this
system in increasingly zonal flow Sat night into Sun AM. We`ll
have to watch this to possibly squeeze out some flurries or
sprinkles, but counting on quick hitting nature of wave and lack
of deep moisture to keep forecast dry attm. Another wave looks to
arrive around the middle of next week, but models are not in very
good agreement as latest GFS is much further S than EC. QPF
signal doesn`t look great attm, so forecast remains dry, but
wouldn`t be surprised to see some low PoPs/QPF added later on.

Expect a moderating temperature trend over the coming days but
this will be tempered by the existing snow pack. Perhaps by early
next week we`ll have lost enough snow to allow most of CWA to see
highs at least in the 40s. Southern areas that remain snow free will
see more substantial incr in temps into the 50s as early as Sun.
Temps fall back a bit middle of next week, but overall, no
significant temp fluctuations expected over the next week.



&&

.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday)
Issued at 519 PM CST Thu Dec 31 2020

Primary concern remains for the potential of fog later on tonight,
especially after 06Z. With full sun and temperatures just above
freezing, enough melting has occurred today to help produce fog
tonight as winds will be rather light. One caveat is how soon the
thick shield of cirrus will stream northward to help tamp down the
widespread production of fog. If this cloud shield takes a little
longer, we will almost surely have some dense fog in the area. We
will hit a few degrees below crossover temperatures by as early as
03Z, and by 06Z we could be in trouble if not enough thick high-
level sky cover makes its way in. I suspect that BR will develop
if not FG, and that we will have a considerable stratus deck
develop in response. I have forecast IFR/marginally LIFR
conditions for the overnight, and hi-res models are consistently
indicating the potential for this to develop. I have hit
fog/stratus a bit heavier than the previous forecast and have
continued this trend from the previous forecast.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&

$$

DISCUSSION...Thies
AVIATION...Heinlein




Area Forecast Discussion

National Weather Service Lincoln IL

 857 PM CST Thu Dec 31 2020

.SYNOPSIS...
Issued at 846 PM CST Thu Dec 31 2020

Freezing rain will overspread central Illinois late tonight and
continue into Friday morning, though a changeover to rain is
likely in areas south of I-72 by late morning. The ice, mixed with
sleet and snow at times, is expected to continue into the
afternoon northwest of the Illinois River, before the storm system
moves northeast in the evening and takes the precipitation with
it. While much of central Illinois will reach the lower to mid 30s
by afternoon, areas south of I-70 should see highs well into the
40s.

&&

.UPDATE...
Issued at 856 PM CST Thu Dec 31 2020

Plenty of dry air sampled on our evening balloon sounding, but
this should moisten quickly from the top down as our storm system
lifts northeast. Mid evening radar imagery shows the leading edge
of the echoes across the southern third of Missouri, with surface
reports showing is freezing rain. Latest HRRR shows this precip
shield reaching Springfield and Decatur toward 2-3 am and the
Peoria metro toward 6 am.

Main concern will be with timing of any switchover to rain. HRRR
keeps the freezing precip continuing past midday north of I-72,
while the newly arrived 4km NAM and the ARW/NMM switch it over by
midday as far north as Bloomington. Stiff low level northeast wind
flow and frozen ground add some concerns that the slower solution
may be the way to go, though precip rates may be heavy enough that
latent heat release may compensate. Will keep a rain or freezing
rain mix continuing along and west of I-55 into the afternoon with
a switchover in eastern Illinois.

Still looking like a widespread quarter to third inch of ice
accumulation across the warning area, with a tenth or two of ice
southeast of there. No changes will be made to headlines at this
time.

&&

.SHORT TERM...(This evening through Friday night)
ISSUED AT 417 PM CST Thu Dec 31 2020

Lots to discuss, therefore the late products:

A deep upper level trof is carrying a large Low pressure system
across the far southern Plains, near the Gulf of Mexico off the se
Texas coastline. This is the system that will track northeast
through the overnight, impacting central Illinois and the Midwest
to ring in the new year. Currently looking at sfc observations and
seeing most locations throughout central and southern Illinois
sitting below freezing. This is the key component to precip type
for the overnight moisture. As the Low pressure system lifts
through the Mississippi River Valley, the excessive moisture
content will continue to lift with the core. With some precip
already edging out ahead of the system, this will work through
moistening up the lower atmosphere and continue leading
precipitation northward. Forecast soundings indicate that although
the sfc temperatures will be below freezing at the onset of
precip, the mid level will be much warmer. This will melt all
frozen precip in the mid levels, however as this falls, the level
near the sfc will be below freezing. This depth appears to only be
in excess of maybe 2kft, which would not typically be enough to
provide a full refreeze of water droplets. As these still liquid
droplets reach the below freezing ground (as indicated by frost
depth readings from this morning), they will freeze on contact.
Frost depth readings this morning, in areas where Ice Storm
Warning is in effect were from 1-6 inches deep. Here at the ILX
office, we reported a 4 inch depth this morning. This is
sufficient enough for freezing rain development. The leading edge
of this system is expected to fall as all freezing rain overnight
into Friday morning. With heaviest precipitation arriving towards
morning north of the I-72 corridor, this is highlighted as the
best chance for ice accumulations up to 0.40 inches of ice
accumulation possible. This will create dangerous and hazardous
conditions throughout the region, as travel would be nearly
impossible and damage to trees and power lines could create
widespread power outages. As the system tracks northward, warmer
air will begin to filter into the area Friday morning into the
afternoon, changing freezing rainfall to rainfall...however this
is only expected to occur se of the I-55 corridor. Mixed precip is
expected from the I-55 corridor through the Illinois River Valley.
Nw of the Illinois River Valley is forecast to remain cold enough
that freezing rain will likely prevail, before a change to
snowfall as the backside of the Low pressure system begins
shifting to the lower Great Lakes late Friday night. This could
bring up to two inches of snowfall around GBG, while decreasing to
near 1 inch along a line extending from Rushville to Peoria. This
system is forecast to be out of the area by 06-09z Saturday
(late Friday night).

&&

.LONG TERM...(Saturday through Thursday)
ISSUED AT 417 PM CST Thu Dec 31 2020

Another Low pressure system will progress through the se US
Saturday, with which another brief round of precipitation could
bring mixed precip to the area. This would be due to excessive
moisture lingering from tonight`s system.

High pressure then returns across much of the eastern US during
the first part of next week, however this is pushed off the
Atlantic coast by the middle portion of the week, as another upper
level trof and split Low pressure system traverse through the
central CONUS. Current model trajectory indicates a general path
north and south of the local area in the upper level, as the sfc
Low`s both track along the same idea. This will drape a frontal
boundary through the region Wednesday night into early Thursday,
however the current moisture availability does not support much
precipitation.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 518 PM CST Thu Dec 31 2020

MVFR conditions have overspread much of central Illinois early
this evening. HRRR and NBM guidance suggests there may be a
period between 08-12Z that may come back up, but confidence on
this lowers the further north you go, so will only include a TEMPO
period for the KSPI-KCMI area. IFR/LIFR conditions will be
widespread by mid morning Friday.

Large area of freezing rain will overspread central Illinois early
Friday morning from south to north, with northeast winds gusting
from 20-25 knots. The question will be whether any conversion to
straight rain will take place in the afternoon, as temperatures
rise. Most uncertainty for this will be at KPIA/KBMI, and will
keep the FZRA mention there through the end of the period, with a
switch to rain is more likely further south between 18-21Z.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from midnight tonight to noon CST Friday
for ILZ044>046-052>057-061>063-066>068-071>073.

Ice Storm Warning from 3 AM to 6 PM CST Friday for ILZ031-037-
038-041>043-047>051.

Ice Storm Warning from 6 AM Friday to midnight CST Friday night
for ILZ029-030-036-040.

Winter Weather Advisory from 6 AM Friday to midnight CST Friday
night for ILZ027-028.

&&

$$

UPDATE...Geelhart
SYNOPSIS...Geelhart
SHORT TERM...Baker
LONG TERM...Baker
AVIATION...Geelhart



AREA FORECAST DISCUSSION...UPDATED

National Weather Service Jackson KY

 757 PM EST Thu Dec 31 2020

.UPDATE...
Issued at 757 PM EST THU DEC 31 2020

Forecast is on track this evening. Evening update entailed only
minor adjustments to the hourly grids, mainly temperatures and
dew points. Also freshened up the zones to remove afternoon
wording. No other changes at this time.

Frontal boundary has stalled out just to the south of our forecast
area. With the loss of upper level support steady rains have
exited the area with only low stratus left behind. Low pressure
over ARKLATX is winding up and will be poised Friday morning to
shoot rapidly into the Great Lakes Region by late in the day.
This action will lift the surface front to our south back
northward during the day Friday. Consequently rain will redevelop
across the area late tonight. Current forecast has all this
handled well.

&&

.SHORT TERM...(This evening through Friday night)
Issued at 431 PM EST THU DEC 31 2020

Late this afternoon an upper level ridge extended from the
Caribbean into portions of the western Atlantic with a ridge over
portions of the eastern Pacific. A split flow pattern was observed
over much of the Conus with the northern stream displaced well to
the north and a broad trough in the southern stream. Moving
within the southern stream was an upper level low moving across
TX. A shortwave trough is moving across the Great Lakes and mid OH
Valley. At the sfc, high pressure was centered over the Great
Lakes region while a sfc frontal zone extended from the Atlantic
into VA and then into the TN valley. Surface low pressure is
organizing over southeastern TX with a warm front developing to
its east across the Gulf Coast states. Patchy light rain and
drizzle lingers across portions of the CWA at this point.

The upper level low is expected to track to the north northeast to
the mid MS Valley on Friday, New Years Day, and then into the
Great Lakes Friday night. Meanwhile, the sfc low should track into
southeast OK tonight and then into the mid MS valley on Friday
with a triple point low developing over western KY with the sfc
low tracking northwest of East KY on Friday night.

As the mid level shortwave passes east of the area over the next
couple of hours, the patchy light rain and drizzle should tend to
decrease in coverage with a relative lull in the precipitation
anticipated during the evening into the first portion of the
overnight. However, warm air advection and isentropic lift ahead
of the warm front lifting north toward the Commonwealth is
expected to lead to showers spreading into the area toward dawn
from the TN Valley. This warm front should lift into the region on
Friday afternoon and lead to the steadier precipitation departing
to the northeast. Showers are still anticipated on Friday
afternoon to Friday evening as the cold front approaches. Enough
instability may exist near the cold front for isolated
thunderstorms over central KY and middle TN that try to move into
the area later in the afternoon or early evening. If thunderstorms
were to materialize they may be able to mix down some of the
higher momentum from stronger winds aloft. Outside of thunderstorms,
the higher momentum from stronger winds aloft should mix down to
some of the higher terrain over southeastern KY. At this point, we
opted to increase the wind gusts across the higher terrain. The
12Z HREF and hi resolution models such as the 12Z and 18Z HRRR
suggest advisory level wind gusts are possible in the higher
terrain particularly in Harlan and Letcher counties near Pine and
Black Mountains for a few hours either side of 18Z. That pattern
is also somewhat conducive to mountain wave development potential
downwind of Black and or Pine Mountain as well. With this in
mind, opted to go with an SPS for some of the southeastern
counties though trends may need to be monitored for the need of an
advisory for some of the VA border counties.

As the cold front moves east and the associated upper level
low/mid level wave depart to the northeast, deeper moisture will
depart and chances for precipitation will diminish on Friday
night. Plenty of low level clouds are expected to linger, however.

Lows and temperatures tonight should not be far from current
readings with a north to south gradient anticipated. Temperatures
will be much milder on Friday in the warm advection pattern.
Highs should reach the 60s in many areas with temperatures
remaining mild behind the front on Friday night.

.LONG TERM...(Saturday through Thursday)
Issued at 440 PM EST THU DEC 31 2020

12Z Saturday - 12Z Monday...
By 12z Saturday, eastern Kentucky will be in between systems.
Aloft, upper level ridging will reside across the Southeast US
with an axis extending NWward to over Illinois. To our north,
upper level troughing, associated with the remnants of
Friday`s storm system, will be weakening over Lake Ontario and a
new coastal low will be taking shape along the New England coast.
The cold front associated with this transitioning system will be
to our southeast over the Piedmont while another weak surface
trough trails SWward to along the Ohio River. Between the front
and this surface trough, a narrow, anemic surface ridge will
likely reside along the western slopes of the Appalachians. To our
southwest, another upper level low will be deepening over TX/OK.

Model agreement is fairly good showing this next low lifting
toward the Ohio Valley Saturday and crossing the region Saturday
night into Sunday morning. As the low pulls away toward New
England Sunday night, another shortwave pivots around the
southern periphery of the low. At the surface, a weak surface low
develops over the mid-Mississippi Valley Saturday. This system
quickly occludes as it rides NEward along the Ohio River Saturday
night and a new low develops along the triple point over the GA
or SC. This new coastal low quickly strengthens and pulls away on
Sunday as the upper low`s trailing cold pool moves in from the
southwest.

In sensible terms, lingering low-level moisture under a
subsidence inversion should lead to mostly to partly cloudy
skies on Saturday. The more widespread cloud cover will likely be
found closer to the surface trough along the Ohio River while
nearly full sun develops over far southeast KY. With that in mind,
highs are expected to remain suppressed in upper 40s north of
I-64, but should rebound into the upper 50s in the warmest valleys
near the TN and VA borders. Increasing clouds will yield to a
period of widespread rain showers Saturday night. Temperatures
aloft will become borderline cold enough to support ice crystals
and possibly a few flakes above 3,000 feet on Sunday before the
precip tapers off. Low clouds, weak CAA, and precipitation should
hold Sunday`s highs in the 40s. The trailing shortwave will
likely keep plenty of clouds around Sunday night with even a
flurry or two possible.

12z Monday - Thursday...
Model agreement worsens Monday into Tuesday before improving
slightly for Wednesday. Initially, heights will rise on Monday
with surface high pressure expanding northeastward from the
Southern Plains and Gulf Coast. However by late Monday and Monday
night, another shortwave trough drops through the Great Lakes. The
ECMWF and Canadian feature a more amplified trough relative to
the GFS. The Canadian even hints at some light precipitation.
Retained the NBM guidance for now, which kept forecast dry but
increased sky cover to account for the increasing moisture and
raised surface winds to cover the tightening pressure gradient.
Once the trough exits, a stronger ridge, aloft and at the surface,
passes Wednesday. Yet another trough or upper level low ejects
eastward from the Rockies and brings renewed precip chances for
Thursday, but the poor model agreement obscures many of the
details for now.

Mostly clear to partly cloudy skies should prevail for most of the
Monday through Wednesday timeframe except for early Tuesday when
the trough could bring a period of mostly cloudy skies. Thicker
cloud cover will likely arrive by Thursday as the next system
approaches. Temperatures will remain mild for early January with
highs of 45 to 50 on Monday moderating to between 50 and 55 on
Wednesday. Lows are expected to range from the mid 20s to mid 30s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 757 PM EST THU DEC 31 2020

A surface frontal boundary has stalled out just to our south this
evening. With the loss of upper level support, steady rains have
exited the region, leaving only low stratus behind and LIFR CIGS.
Low pressure over ARKLATX is winding up and Friday morning will
be poised to shoot rapidly into the Great Lakes Region by late in
the day. This action will lift the surface front to our south
back northward during the day Friday. Consequently, rain will be
redeveloping late tonight and for a good portion of the day
Friday. The boundary to our south will lift north as a warm front
tomorrow as well, helping to scour out the low LIFR CIGS and
putting the area within the warm sector of this storm system by
late in the day. Wind fields are quite strong with this storm.
Thus non-convective LLWS will become an increasing threat towards
dawn and through much of the day Friday. Otherwise, surface winds
will be generally light, around 5 kts or less and variable, but
becoming southeasterly late and increasing in strength to around
10 kts (and gusty). Eventually will will continue to veer to the
south after the warm front lifts to our north.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

UPDATE...RAY
SHORT TERM...JP
LONG TERM...GEERTSON
AVIATION...RAY



Area Forecast Discussion

National Weather Service Lubbock TX

 710 PM CST Thu Dec 31 2020

.UPDATE...
The major winter storm was over central Texas and spreading snow
further west to along and even west of US 87 in Lynn County south
of Lubbock, and through Slaton and Ransom Canyon just east of
Lubbock in Lubbock County. We have added both Lynn and eastern
Lubbock Counties to the Winter Weather Advisory. But the situation
remains highly dynamic and fluid this evening. RADAR was showing
reflectivity developing over the western South Plains that may
indicate the back edge of the Deformation Axis. Latest HRRR
indicates a spoke of reflectivity also rotating back west to very
near Lubbock by mid evening. But we still have a dewpoint
depression of over 20 degrees needing to be mostly overcome in
order for snow rates to have a significant impact. None-the-less,
this is a very close call for the more populated I-27 corridor
from Lubbock through Plainview this evening into early Friday and
we will update as needed. RMcQueen

&&

.PREV DISCUSSION... /issued 610 PM CST Thu Dec 31 2020/

AVIATION...
A major winter storm system was rotating northeast over central
Texas. Snow and sleet bands were spreading north through the
Rolling Plains and eastern South Plains and best estimate is they
will remain just to the east of both KLBB and KPVW. Precipitation
has lifted north to near KCDS and will lead to increasing snow
through the evening. Appears the best chance for LIFR conditions
at KCDS will occur late this evening into early Friday morning
once full moistening and cooling occurs at the surface. Snow
chances at KCDS are expected to diminish near daybreak Friday with
gradual improving in ceiling thereafter. Cool northerly flow will
continue over KLBB and KPVW with VFR expected to dominate, even
with a possibility of light snow this evening. RMcQueen

PREV DISCUSSION... /issued 224 PM CST Thu Dec 31 2020/

SHORT TERM...
The afternoon short term forecast continues to revolve around the
snow potential this evening into the first day of 2021. While some
uncertainties still remain, the potential for accumulating
snowfall across the eastern half of the forecast area seems
likely with the greatest confidence in accumulating snowfall
across the last two columns of the Rolling Plains where the better
moisture and forcing will reside.

That being said, late afternoon observations show a moistening of
the lower atmosphere from Lubbock southeastward with snow being
reported at Lake Alan Henry and a few flurries across the City of
Lubbock. This activity is tied to energy moving northward into the
FA from the south. CAMs continue to show the upper low tracking
northeastward, digging and reforming a new deformation zone over
Oklahoma after sunset shifting the precipitation shield more to the
east putting areas from Garza County northward to Briscoe County on
the fringe of the snowfall by late this evening.

This biggest uncertainty continues to be the dry air near the
surface and in the mid-layers and how it will affect our
accumulations due to sublimation as top down moistening occurs. Have
trimmed snowfall amounts and QPFs back a tad to take this into
account, but the winter weather advisory still stands.  It does
appear from AMA and MAF 12Z soundings and from 12Z NAM that the
colder solution for mid-level temperatures will win out with snow
the dominant, if not sole, precipitation phase for the event.

LONG TERM...
The long term portion is quiet relative the storm in the short
term. Another, albeit weaker, upper level low will track across
the region Friday night. This one will also be much more limited
in the moisture it can tap. Add in a fast motion and a quick burst
of light snow across the northern zones still looks like the best
this one will do. Afterwards, northwest flow aloft will back
toward zonal as a low-amplitude ridge moves across the region
early next week. As a result quiet and mild weather is expected
for Saturday through Tuesday. The next upper low to potentially
affect the region is progged for the middle of next week, however
there is a large variance in the models regarding the handling of
this system. That will be something to watch as we head through
the first week of 2021. Happy New Year, y`all.

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM CST Friday for TXZ024>026-
030>032-035>038-041>044.

&&

$$

05/99



Area Forecast Discussion

National Weather Service Twin Cities/Chanhassen MN

 601 PM CST Thu Dec 31 2020

.SHORT TERM...(This evening through Friday night)
Issued at 256 PM CST Thu Dec 31 2020

Surface analysis this afternoon shows extensive high pressure
centered over IL/IN, expanding westward into the mid-upper
Mississippi River Valley. A weak surface low pressure sits over far
southern Saskatchewan province, with a warm front sagging south
southeast over the central Dakotas. Aloft, generally zonal flow is in
place over the northern Tier states from the Great Lakes well west
into the northern Rockies, with several minor perturbations in the
flow.

As alluded to above, one such perturbation is slow to move out of
the region and has shown up on RAP guidance atop satellite imagery.
Though the morning KMPX RAOB showed the saturated layer at around
1000ft and it is very shallow (only several hundred feet), it has
sustained low stratus over much of eastern MN into western WI into
this afternoon. Weak PVA well in advance of the warm front has been
just enough to keep the low stratus in place. It has shown a very
slow erosion eastward and this slow trend looks to continue into
tonight, trying to show this progression in the gridded forecast.
Another weak wave aloft will move across the region tomorrow in
conjunction with a southern stream system ejecting from the Deep
South into the Ohio Valley. With little impetus to kick the shallow
moisture out of the region, the low stratus is expected to advect
back to the west and encompass much of the area once again on Friday.
Thus, diurnal temperatures from today to tonight to tomorrow will be
fairly small (only about a 10-14 degree from today`s highs to
tonight`s lows) and highs on Friday will be very similar today,
reaching the mid 20s for much of the area. The return southerly flow
expected for Friday and Friday night will also keep Friday night
temperatures from dropping off much, again in the 10-15 degree range
which is what will be experienced tonight.

.LONG TERM...(Saturday through Thursday)
Issued at 256 PM CST Thu Dec 31 2020

An expected quiet pattern continues to be the case for the first
week of the new year. The upper level flow will remain split between
the fairly inactive northern stream and more noticeably active
southern stream, as evidenced by the potent storm system coming out
of the Deep South and into the northeast over the next couple days
and low pressure centers remaining north in Canada. Other than
increased clouds, potentially more than what is currently advertised
through the weekend per the NBM, impacts will be next to none. A
slight uptick in temperatures is expected with a generalized south to
southwest flow across the region going into early next week but any
systems to the north will stay to the north. There are some
indications Wednesday of a system developing in the lee of the
Rockies and spreading east northeast Tuesday-Wednesday, but NBM
continues to show very low PoPs (less than 20%) across the region
with conflicting ideas on what the P-type may be. Conventional
thinking looks for it to be snow, if anything at all, and best timing
with this model run confines any precip potential for only Wednesday
morning so have only advertised precipitation (slight chance -SN)
for that period. Otherwise, temperatures will rise into the low-mid
30s for early next week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 601 PM CST Thu Dec 31 2020

A swath of MVFR ceilings continues to dominate eastern MN and
western WI. There have been some broken and even scattered clouds
along the edges of this swath, but the trend has been to remain
mostly in place, and there are signs of it already expanding this
evening. In fact, some IFR stratus has been expanding over
southeastern MN and was heading northward, and this has not been
picked up in many of the latest short term models. Thus, any breaks
of broken or scattered clouds in eastern MN will be short lived. With
decent moisture advection from the south, and a gradient that will
become weaker overnight and Friday, it seems rather likely that
MVFR/IFR ceilings will be common, even expanding westward to
Alexandria and Willmar, and continuing most of Friday. There will
also be some visibility reductions to MVFR.


KMSP...Some brief breaks are expected this evening, but a broad area
of IFR stratus is making its way northward from southeast MN, so have
indicated IFR ceilings later this evening and for much of the night.
Short term models suggest improvement Friday midday, but only to
MVFR, then ceilings going back down Friday evening as the gradient
becomes very weak and low level moisture remains trapped under the
inversion.

/OUTLOOK FOR KMSP/
Sat...Mainly VFR. MVFR possible. Wind SW 5 kts.
Sun...VFR. Wind SW 5-10 kts.
Mon...VFR. Wind W 10-15 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&

$$

SHORT TERM...JPC
LONG TERM...JPC
AVIATION...TDK




Area Forecast Discussion

National Weather Service Blacksburg VA

 953 PM EST Thu Dec 31 2020

.SYNOPSIS...
Front will stall to our south tonight while high pressure
wedges southwest into our region. Strong low pressure moving
from the southern Plains to the Ohio Valley will lift the front
north across the area Friday, withe main cold front pushing
across Friday night. Another low will track across the southeast
by Sunday.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 950 PM EST Thursday...

Fog beginning to increase across parts of NC and timing of light
rain from the south may be even slower.

Back door wedge front has moved into central NC and is still
try to push into the foothills of wrn NC. Some gusts of 13-20mph
from the NE behind it. Lowering vsbys and ceilings ahead of the
boundary in foothills and Piedmont of NC, and this trend should
continue mainly NC foothills and into the mountains as well
overnight. Will likely issue an SPS for the fog but unsure of
how dense or widespread it may get. Certainly appears worse
south of the CWA.

Made a few minor adjustments to account for milder then expected
temps this evening ahead of the back door front and so far temps
not falling behind the wind shift boundary quite as quickly as
anticipated. Also continued to slow down timing of arrival of
light rain from the south by a couple more hours as most hi-res
guidance and trends on national radar mosaic seem to agree it
will likely be 4 or 5am or even later before beginning in NW
NC.


Prev discussion as of 630 PM EST Thursday...

Cloudy much of tonight with patchy fog and isolated drizzle,
then light rain moving north across the area from pre-dawn south
to just after dawn north of I-64. Some light freezing rain along
ridges Friday morning mainly north of US 460.

Made some minor adjustments for mild temperatures early this
evening and lack of precip most places with only a few light
sprinkle extreme southeast corner from Yanceyville to Charlotte
Court House, and also in the far west. As back door front moves
down from northeast, already pushing through LYH area, will
begin to see ceilings drop, more patchy fog and even some
isolated drizzle form.

Most 18Z and even more recent high res models such as HRRR are a
little slower with arrival of more steady light rain late
tonight and into Friday morning so made some adjustments to that
timing, but at this point not adjustments to early morning and
Friday daytime temperatures, but with precip arriving with a few
temps, mainly on ridges, still at or below freezing, this added
just a tiny amount of additional ice accum in a few spots. All
after 12Z though given timing of precip arrival. Not enough to
warrant any changes to advisory area, but a few higher ridges
down to Poor Mtn on Roanoke/Floyd border, and some of the ridges
in Giles and even wrn Montgomery Co could see a very light
glaze during the morning. Can likely cover these with statements
since these will be small areas.

No other changes at this time.


Prev discussion as of 140 PM EST Thursday...

A messy New Years Day - Light ice accumulation late tonight into
Friday morning north of Roanoke...rain for most of the area, but
nothing substantial.

Not much on radar early this afternoon, as moisture convergence is
limited to the eastern Carolinas. Nonetheless, a shortwave moving
across the mid-Atlantic this afternoon/evening should touch of
showers across the Wv mountains but overall most of the forecast
area will be dry yet damp/drizzly through this evening with spotty
rain along/east of the Blue Ridge.

Overnight insentropic lift increases and warm advection overtop the
frontal boundary will set up rain moving from south to north late.
At the same time high pressure wedge extends southwest to the NC
mountains. Models having tough time with wedge and how cold air will
be in the lowest 2kft. Leaning toward cooler temps but not very
confident as warm nose looks pretty strong. Thinking is that any ice
will be on elevated objects (tree/powerlines), but only takes a
trace of ice on roads to cause headaches, so will hoist a winter wx
advisory from Greenbrier to Amherst, south to Craig County for late
tonight through Friday morning. Best threat will be in the 7am-11am
time frame. Ensemble plumes overall have best threat of ice north of
HSP-Lexington, VA Friday afternoon, therefore ending advisory at
noon.

Patchy icing on elevated objects may occur as far south as Mountain
Lake to Floyd/Meadows of Dan, but too isolated for advisory.

As far as the rainfall, excessive amounts are not looking as likely
as line of convection moves across the southeast states, which could
rob inflow of deeper moisture up our way as the front moves across
late Friday. Thunder is not out of the question but wedge overall
looks strong enough to preclude it in the forecast. Best threat of
thunder would be in far SW VA into the NC mountains/foothills around
dusk Friday.

Lows tonight will be in the 30s, coldest along the eastern slopes of
the Alleghanys/Blue Ridge north of Roanoke, with lower 40s across
portions of far SW VA.

Wedge in place with increasing rain will keep it chilly New Years
Day for most of the area, with mid to upper 30s from the Roanoke and
Greenbrier Valleys east to southside Virginia/Lynchburg, but warmer
south and west with mid 40s to lower 50s expected. Potential for
bust on temps based on strength of wedge.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 209 PM EST Thursday...

No headlines at this time for Saturday and Sunday.

As upper low shears out over the southern Great Lakes Friday
evening, the front exits the CWA with showers ending from west to
east overnight.

Wedge slow to erode Friday night, but models have cold front moving
through which clears a wedge out, so temperatures could actually
rise for some as the wedge erodes. Lows will be in the mid 30s to
lower 40s, coolest across the Alleghanys, warmest in the Clinch and
Holston River Valley.

A cold front along the coastal plain Saturday morning will move
east into the Atlantic ocean Saturday afternoon as the low center
lifts northeast into the New England coast. High temperatures
Saturday will be mild with readings from the mid 40s in the
northwest mountains to the mid 60s in the piedmont.

Another closed low tracks across the Red River Valley Saturday into
Saturday night, heading into the Ohio River Valley Sunday. This low
will tap the Gulf and bring a wave of low pressure into the
Carolinas Saturday evening into Sunday. Rain on the northern edge of
this low will spread northward into our area. At this time, this low
is expected to track south of the area, but may clip Southside with
an half inch to an inch of rain. If the track of this low is further
to the west, heavy rain and the potential for flooding increases for
areas along and east of the Blue Ridge. Low temperatures Saturday
night will vary from the mid 30s in the mountains to the mid 40s in
the piedmont. Mostly cloudy conditions with scattered showers
especially in the west expected Sunday. High temperatures Sunday
will range from the lower 40s in the mountains to the mid to upper
50s in the piedmont. A few snow flurries may linger in the northwest
mountains of Greenbrier county in southeast West Virginia Sunday
night. Otherwise, dry and cold weather is expected. Low temperatures
Sunday night into Monday morning will be cold with values from the
mid 20s in the mountains to the mid 30s in the piedmont.

Moderate confidence in the Short term forecast.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 209 PM EST Thursday...

A progressive flow pattern aloft will continue through the middle of
next week.

The upper trough axis across the mountains Monday morning will pivot
east into the Atlantic ocean by Monday evening. High pressure and
ridging will build north into the central Appalachians Monday night
into Tuesday. High pressure will be centered over the region Tuesday
night and slide east Wednesday into Wednesday night. Low pressure
and its associated cold front will approach from the west on
Thursday. A cold front will move across our area Thursday night
into Friday.

Temperatures will be near normal during the long term period.

Moderate confidence in the Long Term Forecast.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
As of 700 PM EST Thursday...

Poor flying conditions will set in tonight as wedge sets up
moving down from the northeast, with patchy rain/fog reducing
vsbys to under 3-5sm at times later tonight and especially
Friday. Look for conditions, mainly ceilings, to drop to IFR at
all locations overnight, with light rain moving in by 12Z-14Z,
and some patchy drizzle even before that.

Some icing appear possible mainly north of a BLF-ROA line Friday
morning, with LWB-HSP showing best threat for freezing rain for
a few hours between 12-16z. BCB may also see very light icing
for a couple of hours after 12Z, but temps will be hovering very
close to freezing so may or may not be much of a factor at BCB.
More so farther north. Higher ridges north of BCB-ROA will
certainly experience some light ice accretions.

By 16-18Z rain may increase to moderate for much of Friday
afternoon with continued IFR conditions.

Winds will be light/variable for most location, with a couple
of exceptions. In the Piedmont northeast winds may gust from
10-15mph tonight at times behind back door wedge front, and then
Friday afternoon south to southeast winds may begin to pick up
at BLF as deep low pressure moves up into the Ohio Valley,
increasing ridge top winds especially.


Forecast confidence is above average for all elements, except
low confidence on how low cigs/vsbys may drop overnight at most
sites.

Extended Aviation Discussion...

MVFR/IFR conditions are expected into Friday night, but with
some partial clearing later Friday night in the central part of
the forecast area, with best chances for ceilings lifting at ROA
and maybe BCB. Brief return to VFR on Saturday for most
locations with exception of BLF and maybe LWB, before next
system with rain and sub-VFR conditions moves in for Saturday
night into Sunday.

High pressure should bring a return to VFR by Monday-Tuesday.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Winter Weather Advisory from 4 AM to noon EST Friday for
     VAZ018>020-023-024-035.
NC...None.
WV...Winter Weather Advisory from 4 AM to noon EST Friday for
     WVZ507-508.

&&

$$
SYNOPSIS...AMS/WP
NEAR TERM...SK/WP
SHORT TERM...KK/WP
LONG TERM...KK
AVIATION...AMS/SK/WP