Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/01/22
Area Forecast Discussion
National Weather Service Birmingham AL
554 PM CST Fri Dec 31 2021
For 00Z Aviation.
/Updated at 1150 AM CST Fri Dec 31 2021/
Fog has pretty much mixed out, with ragged stratus now the
predominant condition. Had to raise high temps several degrees in
the south due to warm advection and peaks of sun getting through.
Highest POPs through the afternoon will remain in the north half.
Outside chance of thunderstorms, but given the cloud depth and
coverage of showers, I think that any storms that form would be an
isolated exception rather than the rule.
Winds start to pick up tonight ahead of the next inbound system,
and models now suggest more of a continued stratus regime rather
than the fog we got last night.
/Updated at 0224 PM CST Fri Dec 31 2021/
No big changes from previous long-term forecast. Strong/severe
storms, followed by much colder air mass, followed by return to
dry and seasonably cold weather.
Previous long-term discussion:
/Updated at 400 AM CST Fri Dec 31 2021/
Saturday night and Sunday.
Strong to severe thunderstorms are expected to enter Central Alabama
Saturday evening, generally along and ahead of a progged pre-frontal
surface trough positioning from near the ArkLaTex northeastward into
the TN Valley. This will likely contain a mixed/messy variety of
thunderstorm modes, which includes a conditional risk for discrete
supercells ahead of the subsequent linear band of convection.
Discrete cellular convection continues to be suggested by the ECMWF
(which verified quite well with convective placement with our last
severe event), as well as some initial runs of the HRRR and HRW
FV3. Pressure falls associated with the pre-frontal surface
trough should keep surface winds backed to a south-southwesterly
direction during this time. These winds will coincide with a 50-60
kt southwesterly low-level jet, and from there, gain further
momentum with height, though not changing direction much. Thus,
deep-layer flow still seems to remain mostly parallel surface
features; this has always been a source of uncertainty for
anticipated severe risks, but a more supportive factor for locally
heavy rainfall. Nonetheless, my overall expectation is for 0-1 km
wind profiles to support 200-300 m2/s2 SRH along with the
expected 60+ kts eff. bulk shear. These kinematic fields support
all modes of severe weather given any robust thunderstorm
updrafts, either discrete or line-embedded supercells. Expected
thermodynamics include 500-1,000 J/kg MLCAPE, particularly after
sunset when guidance suggests height falls occur overtop the
unusually warm, moist warm sector. Height falls/cooling aloft will
help improve mid-level lapse rates, which most guidance suggests
for the majority of the afternoon are not that good. This seems to
be the main reason more muted instability values appear in
guidance despite what could be another record-breaking warm
For now it appears the best chance for severe convective weather
will be along and north of I-20 from Saturday afternoon through the
early morning hours on Sunday. By later in that period, pressure
falls begin to subside with the northeastward departure of the
surface low. This will allow veering of 0-3 km flow to occur which
will reduce overall severe weather threats, especially the tornado
threat. This should occur as the convective line nears the I-85
corridor. All severe weather should continue to diminish from there
as 850 mb flow becomes westerly behind the exiting low-level jet and
the surging polar air mass infiltrates Central Alabama from the
northwest. By then any lingering thunderstorms should have exited
the area anyway.
Guidance continues to suggest a lagging vort max swinging through
the Deep South at the base of the parent positively tilted upper-
level trough. This has continued to leave the door open for PoPs
throughout Sunday as residual moisture below 700 mb interacts with
lift aloft (PVA). By late Sunday afternoon/evening, most
lingering moisture should now reside below 850 mb. Throughout this
period lies an overlap of critical thickness values supportive of
a glancing transition to light snow/flurries across the northern
part of the forecast area. This is also suggested in various
forecast soundings. Despite this, no accumulation is expected; QPF
is zero. Sunday night will be a huge transition in temperatures
considering the extended period of unusual December warmth.
Monday through Thursday.
Cool/dry/stable air will be in place across the region due to a
broad footprint of high pressure Through at least Tuesday morning.
By then flow aloft should become more zonal and the surface high
should slide toward the Mid Atlantic. This will help air mass
modification to occur as low-level flow becomes more southerly with
time. By mid week, a low pressure system is progged to advance
across the Upper Midwest and Great Lakes. A trailing front and
subsequent disturbance aloft will bring our next rain chance in the
Wed/Thu time frame.
00Z TAF Discussion.
The showers have mostly dissipated with sct-bkn clouds with bases
4-6k feet agl. The cooling of the lower atmosphere overnight will
help stabilize the air mass with limited pcpn expected. Sct
showers will likely develop arnd 09z for areas along and east of
I-65 and continue thru the morning hours. Cigs will lower
overnight with widespread MVFR cigs by 06z with bases arnd
1500 ft agl. Cigs may briefly fall below 1000 feet agl between
09z and 15z. Fog is not expected to be an issue overnight due to
higher boundary layer winds and cloud cover. Cigs will likely rise
above 3000 ft agl between 18z and 21z at most sites. Tstms will
increase in coverage across nw Alabama in the late afternoon, but
will not impact TAG sites until after 00z Sunday. Sfc winds will
increase in speed after 14z and reach 12-15 kts sustained with
gusts to 25 kts by 18z.
Note: AMD NOT SKED is appended at KBHM due to ASOS power loss until
Unsettled weather will continue across the area with additional
round(s) of showers and thunderstorms through Sunday. This period
of unseasonably warm and moist conditions will feature surface
winds from the south and southwest. Thus, RH values will stay
well above minimum thresholds along with periods of wetting
rains through Sunday. A strong cold front is expected to sweep
through the area Sunday. This will be followed by much colder,
drier air which will linger into at least early next week.
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 63 77 58 61 25 / 40 50 100 70 20
Anniston 65 79 62 64 29 / 40 40 100 70 20
Birmingham 66 78 61 61 29 / 30 40 100 60 10
Tuscaloosa 69 79 59 60 28 / 20 50 100 60 10
Calera 65 79 63 63 30 / 30 40 100 60 10
Auburn 67 78 65 66 33 / 40 40 90 80 20
Montgomery 70 82 67 68 32 / 30 30 90 70 10
Troy 66 82 67 69 32 / 30 30 90 80 10
Area Forecast Discussion
National Weather Service Denver/Boulder CO
850 PM MST Fri Dec 31 2021
Issued at 840 PM MST Fri Dec 31 2021
Radar is showing the heaviest snow best area snow over the plains
south and east of the Metro Area. Snowfall amounts 4-8 inches have
fallen across the I-25 corridor from Denver northward. Lesser
amounts south and east. The foothills and mountains have received
about 6 to 12 inches of snow so far. Temperatures are fairly
uniform across the CWA right now at 5-15. Certainly the coldest
airmass to date for the 2021-2022 winter around here. Made some
cosmetic changes to the snowfall, sky and wind GFE grids this
update. This first "real" plain`s snowstorm forecast this season is
panning out pretty well.
.SHORT TERM...(This evening through Saturday)
Issued at 110 PM MST Fri Dec 31 2021
Snow is beginning to blossom across the plains this afternoon as
better synoptic scale ascent begins to enter the region. RAP
Mesoanalysis shows our broad trough axis centered over Utah/Nevada
and this trough axis will continue to push eastward tonight and
tomorrow morning. Water vapor shows increasing moisture over most
of the state and observations/cameras across the mountains and
southern Foothills are beginning to show better snow.
We should see snow spread across the metro and begin accumulating
in the next couple of hours. KFTG`s VAD profile shows deepening
upslope... 10-20kt in the lowest 1km AGL... and this should
contribute to snowfall development. Though certain high-resolution
guidance appears to be struggling with the ongoing conditions,
most guidance is in relatively good agreement in a burst of
heavier snow this evening, followed by prolonged light snow
tonight and tomorrow morning. Trends today suggest a slightly
wetter solution... with QPF amounts close to 0.4-0.5" of liquid
for Fort Collins and Boulder, with 0.2-0.4" for the I-25/I-76
corridors. Snowfall amounts in most locations haven`t changed
much, but we did bump up totals slightly for the lower foothills
and immediate adjacent plains.
Snow should come to an end by late tomorrow morning, though some
flurries may persist across portions of the Foothills and Palmer
Divide tomorrow afternoon. It will be significantly colder
tomorrow across the forecast area, with highs in the single digits
to mid 10s likely. Winds will begin to pick up during the
afternoon across the high country with wind chills well below
zero. Over the plains, wind chill values between 0 and -10F are
likely through the day.
.LONG TERM...(Saturday night through Friday)
Issued at 110 PM MST Fri Dec 31 2021
Even though the snow has ended, it will be cold Saturday night
with temperatures falling below zero in many locations. Clear
skies, fresh snowfall, and light winds will result in good
radiational cooling. The mountain valleys should get very cold
with readings down to -20F. Even low lying areas across the plains
could fall well below zero.
Upper level ridge over the Great Basin will bring warm air
advection Sunday and push highs above freezing over northeast
Colorado. Low lying areas could have a tough time scouring out the
colder and will likely be the coldest locations. Temperatures
will increase more on Monday as the ridge over the Great Basin
shifts eastward over Colorado.
Strong west-northwest flow aloft will prevail Tuesday and should
bring snow back to the northern mountains. East of the mountains
will see gusty downslope winds and mild temperatures.
Northwest flow aloft will continue Wednesday and Thursday. Snow
should prevail in the mountains. May see a period of heavy snow
when the favorable part of the jet moves overhead. This jet along
with a cold front bringing upslope flow may bring snow to the
Front Range and eastern plains sometime Wednesday or Thursday.
Models are still uncertain on the timing of this. A little over
half of the ensemble members are showing this snow. The cold front
should be through the area by Thursday which will lead to colder
temperatures. Ridging should return to the area for Friday and
start a warming and drying trend.
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 840 PM MST Fri Dec 31 2021
Models keep weak east and northeasterly winds at DIA overnight
into Saturday morning. They also keep light snow going all night.
There is some snowfall still upstream over western Colorado at
this time. Ceilings should range in the BKN-OVC007-015 with
Visibilities in the 1SM-2SM -SN range into Saturday morning.
Winter Weather Advisory until 11 AM MST Saturday for COZ040>046-
Winter Storm Warning until 11 AM MST Saturday for COZ030>036-038-
Area Forecast Discussion
National Weather Service Grand Rapids MI
641 PM EST Fri Dec 31 2021
Issued at 642 PM EST Fri Dec 31 2021
I have updated the overnight forecast slightly to increase the
risk of showers this evening. There is a frontal wave passing just
south of Michigan this evening. The supporting upper level jet
(160 to 170 knot speed core) is tracking north of HTL this
evening. The entrance region of that jet has created some mid
clouds and precipitation that currently is no reaching the ground.
I expect the lift from that shortwave to continue to increase the
mid cloud depth and allow for some rain to reach the ground (to
warm for snow of freezing rain) this evening. Mostly north of
This frontal wave has caused the surface wind to back to the
northeast along and north of I-96. It is after this frontal wave
gets east of this area during the early morning hours of Saturday
(NEW YEARS) that we will see temperatures start to fall. It is
also at this time we may see some fog but it would be most
extensive and dense in the I-69 area. We could have some drizzle
during this time but temperatures will mostly be above freezing
so not much threat of freezing drizzle from GRR and southward. By
the time the temperature falls below freezing north of GRR, around
sunrise, the moisture for drizzle will be gone in that area. So
not much threat there either.
Seems the start time for the snow will be mid to late afternoon.
The 18z model runs have not changed this.
.DISCUSSION...(This evening through next Friday)
Issued at 323 PM EST Fri Dec 31 2021
- Travel impacts expected for Saturday afternoon into the Saturday
Overall models trends continue to support accumulating snow moving
into the CWA Saturday afternoon and then persisting into Saturday
night. At the same time...the surface temperatures will be dropping
through the 20s while the winds increase out of the northeast. As a
result...travel impacts are looking widespread.. We will be
hoisting winter weather advisories for much of the CWA. The
northern zones will see the least amount of snow generally an
inch or less so no headline up there...from Harrison to Ludington.
Further south though headlines will be warranted. There will be
two splits to the headline with some timing and amount
differences. We have a swath of 4 to 6 inches of snow from near
South Haven to Lansing with gradually lesser amounts further north
and south of this axis of higher snow amounts.
The right entrance region to a strengthening upper level jet sets up
over the low level baroclinic zone located over central and southern
parts of the CWA Saturday afternoon and evening. Mid level fgen
is noted as well especially Saturday evening. This is when the
column...including the DGZ is most saturated and the lift is
maximized. As a result...accumulating snow is expected and it
could be moderate at times. Currently the southern half of the CWA
is projected to see the most snow. Several models like the High
Res Euro...UKMET and Canadian models have trended downward with
the amounts over the past few runs so there is still some
uncertainty as far as how much snow we actually see. However from
an impact perspective combining the snow...wind...falling
temperatures...the travel should end up being treacherous even if
we only see a few inches of snow.
- Risk for dense fog tonight and local freezing drizzle
Last night there was widespread fog upstream across portions of
IA into MO. We will continue to advect a moist low level airmass
into southern MI this evening. Also there have been some pockets
of clearing this afternoon. As we go through the evening...fog
should develop across Southern Lower MI. Models like the HRRR are
showing the fog becoming dense. While this could
happen...increasing winds may limit this potential. For now we
will feature areas of fog in the grids and zones.
Light precipitation will be possible overnight as a
weak wave of low pressure tracks northeastward along a frontal zone
over Lower MI. There is some lift up to about 4k ft shown in the
moist layer especially over northern zones. Some of this
precipitation could be a mix of freezing drizzle or light snow to
the north of a Big Rapids to Mt Pleasant line as surface
temperatures will be near or just below freezing. Basically we
will feature high POP`s but low QPF for this weak system. Local
travel impacts are possible where the freezing drizzle and light
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 642 PM EST Fri Dec 31 2021
Widespread MVFR conditions prevail at 2330z this evening at all
of our TAF sites. There is IFR cigs/and vis upstream over Iowa and
Illinois. I expect that to move into our TAF sites after 06z.
Areas south and east of GRR will likely see some IFR or even LIFR
fog for a few hours in the 06z to 10z time frame. Once the cold
air solidly moves in around 12z ish... the lower cigs/fog move
Then there is snow event for the late afternoon. That has been
very consistent in the models for days now. I believe all sites
will go IFR in snow by 21z or so on Saturday.
Issued at 323 PM EST Fri Dec 31 2021
The wind will be on the increase tonight into Saturday as the
next storm system approaches from the southwest. The track of this
system has it remaining south of the zones so a northeast flow
will develop. Then as the wave tracks east of the area...the winds
will back to the north by Sunday. It looks like the winds peak
Saturday afternoon and evening when the mixing heights and low
level wind fields will be the strongest. There is some potential
for gusts to reach 30 knots then. We will maintain the small craft
advisory that runs into late Saturday night.
MI...Winter Weather Advisory from 1 PM Saturday to 7 AM EST Sunday
Winter Weather Advisory from 4 PM Saturday to 7 AM EST Sunday
LM...Small Craft Advisory from 3 AM Saturday to 1 AM EST Monday for
Small Craft Advisory from 10 AM Saturday to 1 AM EST Monday for
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1024 PM EST Fri Dec 31 2021
Issued at 1020 PM EST FRI DEC 31 2021
Overall no major changes to the forecast. Starting to see some
embedded thunderstorms over central KY. Forecast soundings show a
shallow inversion near the surface right now which will cap any
severe threat for a few hours, but eventually that cap will erode
and any stronger cells overnight will have the ability to bring
those stronger winds down to the surface. Updates sent to NDFD and
UPDATE Issued at 745 PM EST FRI DEC 31 2021
Only minor tweaks to the grids with this update. With the CAM`s
still not in full agreement, didn`t mess with Pops for later this
evening, and will watch and see how convection develops to our
west over the coming hours. Updates sent to NDFD and web servers.
.SHORT TERM...(This evening through Saturday night)
Issued at 559 PM EST FRI DEC 31 2021
The latest upper level map features a seasonably strong
subtropical ridge centered across western Cuba. Meanwhile, deep
troughing is centered from Hudson Bay down through the northern
Great Basin and then southward through Baja California. Fast west
southwest flow is found in between these aforementioned features,
aligning from the eastern Pacific through the Eastern Seaboard. At
the surface, a stationary frontal boundary is positioned from New
England through the Ohio Valley and across the middle Mississippi
Valley/southern Plains and through the central Rockies. Broad low
pressure is found from the Midwest through the southern Plains,
before congealing into a more concentrated center near the front
range in southeastern Colorado. A secondary warm front is analyzed
from the Deep South through the lower Mississippi Valley. Yet
another pre-frontal surface trough/warm front associated with an
advancing low level jet nose is moving northward. Scattered
showers and isolated thunderstorms have been persistent with this
boundary as it crossed eastern Kentucky today, with the
consolidated activity having now exited northeastern Kentucky.
Highs today have ranged from the low to mid 60s.
The western trough will gradually advance eastward through the
period, maintaining a positive tilt. An embedded more intense
short wave trough, currently rotating across southern Arizona,
will become absorbed into the flow as it cruises east northeast
through the middle Mississippi Valley and eventually into the Ohio
Valley late tonight into Saturday. This will escort anomalously
high PWATs into an axis from the Arklatex region through the Ohio
Valley. At the surface, a baroclinic zone will tighten up across
the Ohio Valley, with traversing areas of low pressure advancing
along the boundary as it very gradually shifts southeast towards
the Appalachians late in the period, bringing heavy rainfall to
eastern Kentucky. On top of the heavy rains, there is also a
potential for severe weather from near I-75 and westward late
Saturday afternoon into the evening hours.
A mostly quiet evening is expected across eastern Kentucky to
begin the period; however, as deeper moisture advects in ahead of
an advancing warm front to our south, showers and embedded
thunderstorms are expected. While an embedded stronger
thunderstorm can not be completely ruled out, any more organized
threat looks to remain to our southwest. The CAMs have also been
showing the potential for some convective training across the
Tennessee/Kentucky border as the boundary slows/stalls for a while
during the pre-dawn hours and into daybreak Saturday. The
synoptic models are less supportive of this idea, maintaining a
more progressive boundary, and quite a bit less rainfall across
our south. Given the increased CAM support and pretty consistent
signal from many HRRR runs following the 12z run from this morning,
have allowed for the slower frontal progression idea. Given this
potential, as well as the main slug of moisture to move through
later Saturday evening, have added the rest of the counties into a
Overall, the heaviest rainfall totals continue to be around the
I-64 corridor, with upwards of 3 inches, as the baroclinic zone
stalls the longest towards the Bluegrass, coincident with the
longer residence time of the very high PWATs that will be in
place. Depending upon upstream convective trends, a more organized
severe threat may also unfold late in the day Saturday, as bowing
segments organize upstream and attempt to hold together as they
advance towards the I-75 corridor. This will be a high shear/low
CAPE environment, with damaging wind gusts the main threat, but
isolated QLCS tornadoes can not be ruled out, given the favorable
low level shear in place. Outside the thunderstorms, southwest
winds will become breezy southeast of the heavier rain axis, with
gusts in the 25 to 35 mph range, especially if some of thicker
clouds relent in the wake of the boundary setting up further to
the north. The rains will gradually taper off from northwest to
southeast Saturday night, with winds veering more towards the west
closer to dawn Sunday morning. Temperatures will continue to
average way above normal into 2022, with lows tonight ranging from
55 to 60 degrees, and highs ranging from the mid 60s north of
I-64, to the lower 70s across southeastern Kentucky for New Year`s
Day. Temperatures will then drop off late Saturday night behind
the departing cold front, ranging from the low to mid 40s across
our far northwest, to the mid 50s across the far southeast.
.LONG TERM...(Sunday through Friday)
Issued at 422 PM EST FRI DEC 31 2021
Models appear to be handling the larger scale synoptic pattern well
this cycle and are showing fairly good agreement through the
extended. However, as would be expected, there are differences in
the details of surface features which will have an impact on
sensible weather. Aloft, a significant trough will pass from the
Great Plains across the Deep South Sunday through Monday, causing a
wave of surface low pressure to develop on the tail end of a frontal
boundary that will be pushing through the Piedmont. This low will
pass through the Southern Appalachians as colder air is pouring into
eastern Kentucky behind an exiting storm system. Evolution and
timing of events suggest there will be a transition from light rain,
or possibly drizzle to snow late Sunday or Sunday evening into
Monday morning. After an extended period of temperatures running
well above normal, ground temperatures will hardly be cold enough
to support more significant accumulations, especially at the lower
elevations. With respect to accumulations, current thinking is that
the bulk of any snow to be realized mainly on grassy areas. Roads
should remain in good shape though some bridges and overpasses could
develop some slick spots, but it is still a bit early to know full
impacts if any...stay tuned.
Shortwave energy will pass through the Midwest by Wednesday, but
moisture will be lacking for this mid/upper level disturbance.
Consequently, at this time, little if any impacts are expected
other than some isolated rain showers. A more significant trough
will dig into central and eastern portions of the CONUS behind
this disturbance, bringing a better chance of precipitation to
the area for the latter portion of the upcoming work week. At this
time, indications are that a surface low will pass northeast
through the Tenn Valley and into the Ohio Valley. Current
solutions have this surface low passing just to our northwest,
close enough that colder air will be drawn into the area quick
enough to convert any lingering precipitation (wrap around
moisture) from rain to snow before ending, providing a second
opportunity of some light snow for the week. As is typically the
case, the exact track of the surface low (again, currently
expected just to our west-northwest) will determine our sensible
weather with respect to potential snow totals. Also, a relatively
warm ground again will act to reduce overall accumulations, if
any. Storm tracks are so important in the winter that we can be
guaranteed that the forecast will change between now and the end
of the extended.
Temperatures are expected to average above normal through the
period, though they will be much closer to normal or even below
normal Monday, and possibly again on Friday. Sunday will likely be
our warmest day (mid 50s to around 60), but temperatures will be
dropping through the day as colder air pours into the coal fields.
Monday will only see highs in the mid 30s, but Friday could wind
up being a bit colder with current forecast highs in the low to
mid 30s. PoPs will be highest during the period Sunday afternoon
and evening (60-90%), but likely PoPs Thu-Fri will probably
increase as we get closer to the end of the week.
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
ISSUED AT 625 PM EST FRI DEC 31 2021
MVFR ceilings to start the 00Z TAF period. Poor flying conditions
expected overnight into Saturday as periods of moderate to heavy
rain move into the area. Ceilings will eventually drop to IFR
overnight into the early morning hours on Saturday before slowly
improving to MVFR throughout the day. Visibilities will also be
reduced at times, especially during periods of moderate to heavy
rainfall. Southerly winds 5-10 kts this evening through early
Saturday morning, increasing to 10-15 kts with gusts of 20-30 kts
during the afternoon and early evening on Saturday. Wind shear has
been mentioned at SYM/SJS/JKL during the beginning of the TAF
period this evening, but winds aloft are expected to decrease
Flood Watch through Saturday evening for KYZ044-050>052-058>060-
Flood Watch through late Saturday night for KYZ084>088-110-113-
Area Forecast Discussion
National Weather Service Louisville KY
921 PM EST Fri Dec 31 2021
Issued at 919 PM EST Fri Dec 31 2021
Forecast remains on track this evening. Light showers are beginning
to overspread the region in response to warm air advection and
isentropic lift. These showers should become more widespread and
moderate to heavy in nature going into the morning hours as deeper
moisture is advected in from the southwest. We`ll also see
thunderstorms develop as elevated instability remains in place, with
them being most prevalent across south-central Kentucky.
Still keeping an eye on the potential severe threat after midnight.
Most high-res guidance continues to highlight a band of stronger
convection developing near the TN/KY borders after 04-05z and slowly
lifting northward ahead of a surge of low level moisture/Theta-E
gradient. Several CAMs have had updraft helicity (UH) tracks
associated with this band of convection as it pushes northward,
which is indicative of supercellular activity. There continues to be
some uncertainty in regard to whether these storms will become
surface based, as soundings reveal a very shallow/weak layer of warm
air in the lowest ~50mb off the surface. And per some upper air
observations like the 01.00z BNA sounding, models have generally
underestimated the strength of the low level (~850mb) cap. This will
be something that will have to be watched very closely as low level
shear/helicity is supportive of tornadoes in this environment. The
cap is expected to weaken overnight with advection of low level
moisture from the south... and even with a weak cap in place,
dynamic lift/forcing associated with mesocyclones in supercells can
overcome weak surface inversions and go from elevated to surface
.Short Term...(This evening through Saturday)
Issued at 300 PM EST Fri Dec 31 2021
...HEAVY RAINFALL EVENT BEGINS LATE TONIGHT AND CONTINUES THROUGH
...STRONG TO SEVERE THUNDERSTORMS POSSIBLE LATE TONIGHT ACROSS
...STRONG TO SEVERE STORMS POSSIBLE ACROSS CENTRAL AND SOUTHERN
KENTUCKY ON SATURDAY...
Near Term Forecast
In the very near term, satellite imagery shows that skies have
broken out a bit more than expected. Skies were generally partly to
mostly cloudy with temperatures warming into the lower 60s across
southern Indiana. Across Kentucky, temperatures had warmed solidly
into the low-mid 60s. KY Mesonet data shows a dewpoint gradient
extending from near Somerset northwest to near Owensboro. These
higher dewpoints continue to advect into the region from the
southwest and on the front edge of this dewpoint gradient, we`ve
seen some scattered showers and a few thunderstorms. The storms
have been moving to the northeast and into a more stable environment
with less moisture and that trend should continue through the
afternoon. For now we will keep isolated/scattered PoPs in the
forecast with temps remaining in the 60s through this evening.
This Evening and Tonight
For tonight, our region will be within a broad baroclinic zone
stretching from TX northeastward through the Ohio Valley. A short
wave trough axis in the Baja will eject northeastward into the
southern High Plains this evening as a stronger wave within the
northern branch of the jet drops into the desert southwest from the
Pacific northwest. Low-level moist flow will continue across the
region and moisture will pool along a northward moving warm front
that is forecast to lift northward toward KY. Low-level warm theta-
e advection is forecast to overspread the region during the
overnight period and that combined with steepening mid-level lapse
rates should result in widespread convective development tonight.
For the most part, rain showers with moderate-heavy rainfall is
expected across southern Indiana and much of the northern half of
Kentucky overnight. Some thunderstorm development will be possible,
mainly across southern Kentucky near the warm front. Based on model
soundings, surface instability is likely to remain rather limited,
but we will have elevated instability given the strong theta-e
advection expected. Given the approaching mid-level speed max along
with a strong low-level jet axis overspreading the area from the
southwest, we will have plenty of low-level shear across southern KY
overnight. There is a threat of some elevated supercells posing a
damaging wind and perhaps a marginally severe hail threat. We can
not rule out an isolated tornado or two, however, we believe that
the highest tornado risk will remain to the south of Kentucky across
middle Tennessee overnight where there is a greater risk for storms
to become surface based.
Given the amount of moisture pooling along the northward lifting
warm front, we will see precipitable water values increase into near
1.5 inches. Model soundings along and north of the WK/BG Parkways
look deeply saturated (almost tropical in nature) with relatively
thick warm cloud layers present. This strongly suggests that we`ll
have efficient warm rain processes ongoing that will result in very
good precipitation efficiency. With storms moving parallel to the
mid-level flow, training of cells is likely. Therefore, we believe
that we can easily achieve 1-2 inch rainfall amounts across central
KY, probably along and just north of the WK/BG Parkway corridor.
Lows tonight will be in the low-mid 50s across southern Indiana and
northern Kentucky. Lows across southern KY will be in the upper 50s
to around 60.
Saturday and Saturday Night
The forecast for Saturday is a bit more complex and contains a fair
amount of uncertainty. What we know is that we anticipate the warm
front across southern Kentucky to lift northward throughout the day.
As this occurs, an area of surface low pressure will be moving
northeast along this boundary coming in from Arkansas with a cold
front trailing it. The global models of the GFS/GEM/Euro continue to
limit the northward push of this warm front, essentially stalling it
out somewhere between the Cumberland Parkway and the
Bluegrass/Western Kentucky Parkway. The 3km NAM and HRRR solutions
are a bit further north bringing the warm front as far north as the
I-64 corridor (HRRR) or as far north as the Ohio River (NAM).
However, there continues to be a notable shift southward in those
models with the 18Z HRRR now only bringing the warm front as far
north as the WK/BG Parkway corridor.
The cold front is poised to intersect this warm sector across
Kentucky resulting in the development of one or more quick moving
squall lines. Model soundings within the warm sector show some weak
surface based instability with abundant amounts of low-level speed
and directional shear. Certainly the squall line would poise a
damaging wind threat and isolated tornadoes within the line would be
possible. Of particular concern is that we could see an area of
enhanced tornado threat in that area just southeast of the low track
and just south of the warm front where low-level surface winds could
be come sufficiently backed to the southeast. Again, the unknown
here is how far north will that warm front go tomorrow afternoon.
Perhaps we`ll see a bit more model convergence later this evening
with the 00Z runs. The slight and enhanced risk areas have been
shifted northward slightly by the SPC to take into account the
possible NAM/HRRR northward placements of the warm front. Given the
speed shear across the region, we feel that the enhanced risk across
southern KY is justified.
To the north of this warm front, extensive rain showers with
moderate to heavy rainfall will continue until the surface low and
cold front press to the east. The NAM solutions continue to hit the
areas north of the Parkways hard in KY with another 1-2 inches
possible. We may get a small break in the action if the warm front
were to press northward through the region for a time tomorrow
morning, but additional convection along the front is expected to
move right back in.
The squall line is expected to exit our forecast area somewhere
between 1-2Z Saturday evening with rain diminishing from west to
east. Cold advection will then move into the region with dropping
temperatures expected overnight. Prior to the frontal passage highs
on Saturday will be mild with readings ranging from the 60s north of
the warm front to the upper 60s to near 70 south of the warm front.
QPF wise, we`re still forecasting 2-4 inches of rainfall with the
highest axis along and just north of the WK/BG Parkways. In this
corridor, 3-4 inches with locally higher amounts will be possible.
The Flood Watch will continue across the entire area as pockets of
flash flooding and more areal flooding are expected to occur
throughout the period. This excessive rainfall will result in quick
rises on area creeks and streams. The runoff will lead to rises
along area rivers such as the Green, the Rough, the Rolling Fork,
The Kentucky, Stoner Creek, and the Licking Rivers. We also expect
the Ohio to rise significantly later next week as the water enters
the Ohio main stem.
.Long Term...(Saturday night through Friday)
Issued at 320 PM EST Fri Dec 31 2021
Sunday Morning - Sunday Night
The cold front, bringing all the rain, is expected to be just east
of the CWA early Sunday morning, but trailing light precipitation is
expected to remain for most of the day. Temperatures behind the
front will drop, but expect the drop to be slow enough that air
temperatures won`t be below freezing until the overnight hours.
Spitting snow mixed with rain is very possible, but no impacts are
expected over much of the CWA. However, areas across south central
Kentucky will likely experience additional precipitation ahead of
the mid-level closed low that will likely pass over Tennessee Sunday
night. This will be late enough and cold enough, with temperatures
below 30, that our southeastern counties could see around a quarter
of an inch of snow. It`s still early, so that number could change.
Monday - Wednesday
Surface high pressure with upper ridging will bring clear skies and
below normal temperatures with highs in the mid to upper 30s on
Monday, but after the center of the surface high passes east of the
CWA Monday night, return flow quickly lifts temperatures to the mid
40s to near 50 for Tuesday and Wednesday. A week cold front is
expected to bring clouds for Wednesday, but will likely lack the
moisture in the low levels for precipitation.
Thursday - Friday
An upper trough diving south, east of the Rockies, will push a
surface high southeast over the Plains to the Mississippi River
while a strong cold front along the southern edge of the high
quickly bows southward through Texas. On the eastern end of the
front, a surface low strengthens as it moves east over the Lower
Ohio Valley. Deep moisture and cool temperatures already in place
from Wednesday`s cold front will likely give the region its first
chance at a measurable snow. Northern winds ahead of the high will
drop high temperatures from the low 30s to mid 40s on Thursday to
the upper 20s to low 30s on Friday.
.Aviation...(00Z TAF Issuance)
Issued at 620 PM EST Fri Dec 31 2021
Moisture will gradually increase through the overnight hours ahead
of a cold front and result in IFR to LIFR cigs by tomorrow morning.
Rain will also increase in coverage, along with some thunderstorms
mainly in central/southern Kentucky, and will result in MVFR to IFR
visibilities. By sunrise tomorrow morning, all TAF sites within the
region should be observing poor flying conditions.
A warm front is progged to push northward into the region tomorrow
after sunrise, and could result in a break from the precipitation
across portions of central Kentucky in the mid/late morning to mid
afternoon hours. In areas that see a break from the rain, southerly
wind gusts could gust +25kts and cigs could push above IFR levels.
Otherwise, rain will continue most of the day tomorrow across
southern Indiana and northern Kentucky and cigs will struggle to get
above IFR levels.
A line potentially strong to severe thunderstorms may push into the
region after 18z tomorrow. Winds could be very gusty along and just
ahead of these storms for a brief period of time, and would mainly
impact the BWG/LEX terminals. Cigs/Vis will slightly improve toward
the end or just beyond the end of the forecast period behind the
main line of storms.
IN...Flood Watch through Saturday evening for INZ076>079-083-084-
KY...Flood Watch through Saturday evening for KYZ023>043-045>049-
AREA FORECAST DISCUSSION
National Weather Service Morristown TN
942 PM EST Fri Dec 31 2021
1. A few elevated, isolated severe storms possible late tonight
and early Saturday morning.
2. Strong winds across the area on Saturday afternoon.
3. Main risk Saturday evening/night will be QLCS storm mode
capable of damaging winds and a few tornadoes.
Surface analysis shows a diffuse boundary located through
Middle TN and extends southeastward through SE TN and NE GA. As
jet dynamics strengthens across the Ohio Valley late tonight, the
850mb LLJ will become more SSW and strengthen across our region
which will take this diffuse boundary/weak secondary warm front
northward and increase low-level convergence along the boundary.
This will spark some isolated convection across our area with the
highest concentration of convection across northern Middle TN and
into KY where boundary layer convergence along the boundary will
be strongest. RAP forecast soundings indicate MUCAPE of 1000 to
1300 J/Kg is expected along this boundary tonight which will
result in the possibility of some elevated thunderstorms late
tonight and early Saturday morning. While these storms are
forecast to be isolated across our area, any that develop could
contain some 1 inch+ hail and have some elevated rotation with
backed surface winds along the front resulting in fairly long,
curved hodographs. The lack of surface instability will mitigate
damaging wind or tornado risk tonight.
The strong gradient winds and strengthening LLJ on Saturday
afternoon will result in very strong wind gusts across the entire
area. Have issued a High Wind Warning for the higher elevations of
the mountains where winds gusts near 70 mph will be possible near
and above 4k ft. Wind gusts approaching 40 mph will be possible
across the valley. Potential higher gusts will be possible along
the plateau and higher elevations of NE TN/SW VA, and these areas
will be monitored for any potential wind headlines on future
The big forecast impact will be Saturday evening and early
Saturday night. Speed shear will be very strong, but
unidirectional shear with height paralleling the approaching front
should limit prefrontal cellular activity. This will favor a QLCS
line of convection with damaging winds and QLCS tornadoes being
the primary risk early Saturday night. A few CAMs continue to
show some supercell development ahead of a QLCS across AL with
these cells moving NE late Saturday afternoon and evening. With a
mid-level cap in place, if some local forcing can overcome CIN, a
few cells could perhaps develop. Supercell storm modes cannot be
discounted and need to be monitored as we head into the event, but
the overall positive tilted upper trough and relatively straight
hodographs should favor splitting cells and make it difficult to
maintain long-tracked cellular structures. Continue to be most
confidence in the QLCS storm mode for our region, and with 0-3 km
shear near 60 kt, any bowing segments with a descending RIJ could
quickly produce QLCS tornadoes.
00Z TAF DISCUSSION.
Poor flight conditions forecast through the period. MVFR cigs and
vis likely to prevail tonight with a moist boundary layer and a
secondary warm front surging northward. This will initiate some
scattered showers late tonight with a few vcts near CHA and TYS.
We dry out some in the warm sector tomorrow with vcsh and some
vcts during the afternoon. Winds become strong from 200 to 240 deg
during the mid-day to afternoon hours on Saturday with gusts
potentially approaching 40 kt at terminals. A line of
thunderstorms is expected near the end of the period with severe
wind gusts possible.
/ISSUED 358 PM EST Fri Dec 31 2021/
SHORT TERM...(Tonight through Saturday)...
1. Elevated showers and thunderstorms tonight as warm front lifts
north through the forecast area.
2. Scattered showers and thunderstorms developing by late
afternoon ahead of potential severe weather event tomorrow night.
Broad WSW upper flow will remain in place across the southern
tier states tonight and into Saturday. A shortwave trough will
eject ENE out of New Mexico tonight and into Saturday morning
which will help pull a warm front north through the forecast area
late tonight as southerly flow strengthens out ahead of it.
Already have some isolated storms ongoing across northeast AL and
northern GA this afternoon and some HREF members, namely the HRRR,
shows this continuing to blossom and spread northeast across areas
from Polk count TN eastward into western NC. This should be mostly
it in terms of precip until later tonight when isentropic ascent
ramps up. Have PoPs following the HiresWFV3 mostly, showing
fairly widespread elevated convection developing tonight along the
TN/GA border and lifting north towards the KY/VA/TN border area by
daybreak or so tomorrow. This should yield mostly dry conditions
tomorrow as we are deep into the warm sector of this system, but
couldn`t take PoPs completely out as some isolated convective
showers will certainly be possible during the day.
By late tomorrow afternoon, aforementioned New Mexico shortwave
shifts east to TN/KY, and low level flow responds accordingly. By
21z most guidance shows H85 flow ramping up to 40-50kt across the
Cumberland plateau, which will eventually shift east into the CWA
for a conditional severe weather threat tomorrow night. It`s
doubtful that there will be much of any strong to severe
convection before the end of the short term but would expect the
southern Cumberland plateau area to be the location to watch if
LONG TERM...(Saturday Night through Friday)...
1. Strong to severe storms will be possible Saturday evening, with
damaging wind gusts and heavy rainfall being the main impacts.
2. Much colder temperatures are expected Sunday, with a transition
from rain to snow Sunday evening into early Monday. Snow
accumulations are possible in the Valley, with the highest amounts
expected in the higher terrain and NE TN & SW VA.
Saturday evening through Monday morning looks to have active and
varied weather from strong/severe storms, flooding, and winter
weather all within a 48 hour timeframe. All of this weather will be
driven by a strong dynamic system swinging through the
Ohio/Tennessee Valley`s over the weekend. Will break down the
current thoughts on the threats with this system.
Very warm day is expected with a strong low level jet out of the
southwest to the south of the frontal boundary. This will help to
pump in warm, unstable air, along with good speed shear. Directional
shear component is not as impressive, but with these strong winds
helping to increase low level shear of 30+ knots in the eastern TN
Valley, the chance for a possible tornado is present. Biggest
question looks like it will be how much instability is available for
storms to tap into. As usual the NAM is the most bullish with MLCAPE
while most other forecast soundings showing a more moderate 300-500
J/kg, but all of these are pretty high for New Years Day. Think the
biggest threat with possible severe weather will be strong straight
line winds as this fast moving system makes it`s way through, but a
quick isolated spin up of a tornado can`t be ruled out along the
QLCS line. Think the main line will move onto the Cumberland Plateau
around 00z, and quickly push east of the mountains by around 06/07z.
This system will also have a good amount of moisture to work with as
the jet helps to pull in Gulf moisture, and PWAT values rise above 1
inch in the Valley. This will help produce heavy showers and
thunderstorms that could quickly dump a moderate amount of rain
ahead of the line with isolated storms, and as the main line moves
thorugh. High resolution models and Plumes indicate that 0.5-1.5
inches of rain are expected on Saturday which could lead to flooding
of low lying and poor drainage areas by Saturday evening into early
Sunday. But hopefully with this system quickly moving through the
QPF amounts and flooding will be somewhat mitigated.
By Sunday we should get a brief break in precipitation chances as
the line is to the east of the mountains, and the surface low begins
to move through the Tennessee Valley. This will bring with it a
strong shot of cold air Sunday night into Monday morning quickly
dropping temperatures below freezing. With the 12z model runs some
of the operational models are now indicating that the system will be
stronger and slower than previous model runs. If this verifies it
would mean that colder air and higher QPF amounts would be likely
leading to more snow in the southern Appalachians and eastern TN
Valley. Operational GFS has gone MUCH higher on snowfall amounts
overnight, and in general most models have increased snowfall
amounts overnight. Have bumped up official snow amounts in the
Valley, but have been much more tame with amounts ranging from a
dusting to quarter inch around Chattanooga, up to around an inch or
more in the Tri-Cities... Higher amounts closer to 2+ inches can be
expected in the higher elevations of the southern Appalachians and
northern Cumberland Plateau. Have stayed closer to GEFS plumes which
show a much lower amount compared to the operational models. Think
that snowfall totals may need to be bumped up if models continue the
trend of slower and stronger with the low, but would like to see
multiple runs of the stronger/slower solution, and would also like
to see ensemble members in better agreement with the slightly higher
snow amounts. Have also undercut some guidance because ground
temperatures are still going to be very warm (highs in the 70s/60s
the days before) so snow will hit the ground quickly melt... Snow
totals on the snow board will be much higher than what people
actually see on the ground and on the roads (which is what most
people actually care about).
Weather quiets down by Monday afternoon and we get into a more mild
and seasonable pattern thorugh the middle of the work week. Another
trough will begin to swing through the eastern half of the US by the
end of the work week... Temperatures are expected to be warm enough
that most of the precipitation that falls Thursday into Friday will
be all liquid, but in the overnight hours we could switch over to
light snow in the Valley... But this is still a ways off and
confidence will likely increase after we past this weekend system.
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 63 75 58 65 29 / 70 70 100 70 30
Knoxville McGhee Tyson Airport, TN 59 75 57 64 27 / 90 50 100 70 50
Oak Ridge, TN 58 72 55 62 26 / 90 70 100 70 50
Tri Cities Airport, TN 55 73 55 62 25 / 90 50 100 60 60
TN...High Wind Warning from 10 AM Saturday to 4 AM EST Sunday for
Blount Smoky Mountains-Cocke Smoky Mountains-Sevier Smoky
Area Forecast Discussion
National Weather Service Paducah KY
523 PM CST Fri Dec 31 2021
Issued at 523 PM CST Fri Dec 31 2021
Aviation section updated.
.SHORT TERM...(Tonight through Saturday)
Issued at 252 PM CST Fri Dec 31 2021
The main concerns through Saturday continue to be flooding
and severe weather. As of 19z today, the leading edge of moist
and marginally unstable air has moved into western Kentucky.
Mixed-layer capes ranged from 500 to 1000 across most of western
KY. A few storms developed earlier today over west KY, but they
were likely elevated due to a capping inversion seen on model
soundings in Bufkit. If surface-based storms can develop this
evening, wind shear parameters are very favorable for organized
severe storm structures. However, this potential remains low at
the current time.
During the night tonight, large-scale forcing will increase ahead
of an upper-level impulse over the southern Plains. Rain will
increase in coverage this evening. As a strong cold front sags
south into the lower Ohio Valley late tonight, strong low-level
moisture convergence will result in a band of heavy rain. The
cams models suggest the heavy rain will initially set up near the
Tennessee-Kentucky border area late tonight, then move north.
On Saturday morning, a rather large band of training showers and
thunderstorms is forecast to occur along the front. Model qpf has
cycled back upward with the 12z runs. The nam in particular has
increased its qpf since yesterday. The exact amounts are probably
not well-handled by any model due to the mesoscale nature of the
training convection. However, href probability-matched mean qpf
supports isolated amounts of up to 4 to 5 inches in the watch
area. The href and wpc axis of heaviest rainfall is mainly across
western Kentucky down into southeast Missouri, south of a kcgi-
kpof line. The Flood Watch remains in effect for most areas except
the I-64 corridor of southern IL, which should be north of the
By early Sat afternoon, a surface low is forecast to track
northeast of our region along the front. The trailing portion of
the front will surge southeast across western Kentucky in the
afternoon. There remains strong agreement among the cams models
such as the hrrr that parts of west Kentucky will remain in the
warm sector for all or part of the afternoon. Therefore, the
combination of marginal instability, strong forcing, and very
strong shear will pose the risk of a significant severe weather
event as far north as the Tennessee border counties. The exact
northward extent of the significant severe weather still varies
depending on the model. The gfs and ecmwf remain quite stable
across western KY, but the cams models are likely to be more
reliable within 36 hours of the event.
.LONG TERM...(Saturday night through Friday)
Issued at 252 PM CST Fri Dec 31 2021
Two main areas of focus in the long term. First, a blast of arctic
air accompanied by some light wintry precipitation Saturday night
into Sunday. Then a second system Wednesday night into Thursday that
may produce more wintry weather.
Gusty northwest winds will usher in significantly colder temperatures
Saturday night. Sub-freezing temperatures reach our northwest
doorstep around 05z and transition across nearly the entire region
by 13z. While the majority of the precip is expected to move out of
the region before the temp drops below freezing, there may be enough
leftover moisture to squeeze out a light wintry mix. Soundings
struggle to generate saturation in the ice nucleation layer, so
freezing drizzle or light freezing rain certainly is still on the
table. Not expecting much, if any, accumulation though.
As we move into Sunday, there is good agreement on a band of snow
developing on the backside of the system as the upper trough axis
pivots through the TN and lower OH Valley. What is less certain is
the exact placement and timing of this. 12z GFS and NAM suggest it
primarily remaining south of our cwa down into TN. The ECMWF and
Canadian depict greater areal coverage of the snow and are also
further north into west Kentucky. GEFS and ECS ensemble members are
varied, but there is enough support from them to boost PoPs higher
and increase snowfall totals somewhat across west Kentucky. This
still looks like a minor event with any accumulations primarily
confined to elevated surfaces.
High pressure builds in Sunday night into Monday, setting the stage
for our coldest air temps down into teens. Highs on Monday will
remain in the 30s. Afterwards, stronger southerly flow boosts our
highs into the 40s, and perhaps even low 50s for southern counties
Tuesday into Wednesday.
Our next system looks to sweep into the region sometime in the
Wednesday night-Thursday time window. A strong upper trough is
expected to dig across the central U.S. with an area of low pressure
developing somewhere in the TN/lower Ohio Valleys. The exact track
of the surface low will be key in determining where any snow sets
up. There certainly appears like a decent chance for wintry
precipitation across at least portions of our area. With it still 6
days out though, fluctuations in the track are likely. Just
something to monitor for now. It took its sweet time in arriving,
but winter is finally here as we flip the calendar to January.
Issued at 523 PM CST Fri Dec 31 2021
VFR conditions early on this evening will transition to MVFR then
IFR in the 03-06 UTC time frame, with IFR conditions prevalent for
the overnight into Saturday. We will start off with SSW winds 10
to 20 kts and gusty at times. They will diminish in speed as a
front pushes into the area and slows down. We will likely have
widely varying wind conditions later tonight into Saturday with
low pressure systems along the boundary across our area.
Showers will develop this evening, then become solid and increase
in coverage overnight into Saturday along the slow moving
boundary. Some thunder is expected, especially across portions of
southeast MO into west KY. Flight conditions late tonight into
Saturday will be particularly poor say 50 miles either side of a
line from KPOF-KCIR-KPAH-KOWB.
IL...Flood Watch through Saturday afternoon for ILZ081>094.
MO...Flood Watch through Saturday afternoon for MOZ076-086-087-100-
IN...Flood Watch through Saturday afternoon for INZ081-082-085>088.
KY...Flood Watch through Saturday afternoon for KYZ001>022.
Area Forecast Discussion
National Weather Service Blacksburg VA
1041 PM EST Fri Dec 31 2021
A frontal boundary and it associated precipitation will enter the
region this weekend and stall. This same front will act as a focus
for an upper level low pressure system to follow across our region
Sunday night into Monday, bringing more robust precipitation, very
gusty winds, and perhaps enough colder air for the lingering rain to
transition to light snow. High pressure builds into the region for
the first half of the week with colder, near seasonable temperatures.
.NEAR TERM /THROUGH SATURDAY/...
As of 1040 PM EST...
Minor changes to adjust PoPs with a few light showers/drizzle
across southeastern WV. Precipitation will be filling in by the
early morning hours. A few spots of transient dense fog, but
most locations are above 3 miles visibility.
As of 700 PM EST...
Clearing but still cloudy, with low stratus and fog developing.
This will trap any fireworks smoke and will make it a New Year`s
Eve to stay in.
Showers and a few thunderstorms are moving through the region
this evening, and are largely now just affecting the Greenbrier
Valley of WV and north central VA, as well as our eastern
zones. The activity near Greenbrier has produced a few lightning
strikes in low-topped convection (cores 10-15kft). The HRRR is
handling this precipitation footprint better than earlier, so
have adjusted overnight PoPs to better reflect its latest
After this batch of precip exits the area shortly, we should see
a break in the activity for a few hours. We will begin to see
more showers as a warm front begins to lift north from our
south, and as a cold front nears from the west. Thus western and
southern sections will see rainfall begin earlier, around 3-5
AM, with interior VA seeing chances increase closer to daybreak
as the fronts shift north and east, respectively.
Low stratus looks more likely than fog for most spots, but we
will see widespread 2-4 mile visibilities late tonight into the
morning. Denser fog is likely for the Greenbrier Valley and
perhaps right along/south of the warm front. These lower
visibilities of a half mile or less will likely come and go and
will be hard to capture with an advisory.
Have adjusted PoPs, weather grids, sky cover, and visibilities
for this update. Also QPF was tweaked. Most locations are still
in the upper 50s to lower 60s, and expect overnight temperatures
to hover near their current readings or even increase slightly.
Most sites will have their lowest readings in the next 1-3
As of 230 PM EST...
Rain and rain showers will be on the increase, especially late
tonight and New Years Day.
Patches and areas of light rain continue to make progress eastward
across our region. An distinct area of drying follows this first
band for this evening, so we are not looking for a continuous
washout of precipitation overnight. However, as we arrive into the
new year, precipitation is expected to start expanding eastward into
the region as a front settles over the area. By daybreak New Years
Day, most of the region west of the crest of the Blue Ridge will be
experiencing a continuous rain which will trend more showery in
nature, along with a generous coverage of fog. Some of the stronger
showers will have the chance to grow into thunderstorms, especially
in areas along and west of roughly the I-77 corridor.
As New Years Day progresses, an approaching upper low along the
front, will buckle the front northward, helping to take the bulk of
the precipitation north of the area by mid-day. Patches or area of
fog may continue across sections of the region also through mid-day.
Temperatures will continue to be very mild for this time of year.
Lows tonight are expected to range from the upper 40s to the mid 50s
across the mountains with mid to upper 50s across the Piedmont. High
temperatures on New Years Day are expected to range from around 60
to around 70 across the mountains with low to mid 70s across the
Piedmont. Take note of the CLIMATE section of this discussion for
possible record temperatures.
Confidence in the above weather scenario is moderate to high.
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
As of 300 PM EST Friday...
Increased Snow Potential Sunday Into Monday.
A cold front will be approaching the area Saturday night, bringing
another round of rainfall behind the day`s warm front.
The heaviest rainfall should come with this front. Overall timing
for arrival hasn`t changed much: entering the area before sunrise
Sunday. Anemic instability and lacking forcing from the ever
increasingly distant parent low should qualm any real severe threat,
besides maybe right against the CWA border to the west. What has
changed is the overall departure of moisture/development of a
The strong trough axis is still expected to pivot, changing from a
positive to negative tilt. Changes in guidance are now pointing to
this change taking longer, resulting in a slow progression of the
front/movement of the secondary low that forms. Because of this
slowing trend, the low will have greater residence time to
strengthen and pull cold air into the area and provide a greater
opportunity for change over Sunday night into Monday before the
trough can depart the region. Because of this trending pattern, the
forecast has been edited to follow it. For now, the forecast still
runs on the lower side of current deterministic guidance (minus the
NAM, which is a current outlier) for snowfall, as overall ensemble
guidance still shows minimal support and high variability in higher
snowfall amounts, and instead most clustering is still on the lower
end of the scale. Amounts in the forecast are generally 1-3 inches
for areas west of the Blue Ridge, with a dusting to an inch in the
east. Obviously the greatest amounts will remain in the higher
terrain. Trends will need to continue to be monitored over the next
24 hours so keep checking back for updates. Overall amounts in the
west are not expected to increase much more, instead amounts in the
east could increase more: likewise, if we see trend back to a faster
departure, amounts overall will go down.
Windy conditions ahead of FROPA are still expected. However, the
slower front and lingering precipitation should help cut back on the
post frontal wind conditions, though it`ll still be breezy.
Following the front`s departure Monday, temperatures remain below
.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 300 PM EST Friday...
Dry Weather Until Next System Thursday Into Friday.
The overall weather pattern levels out starting Tuesday as high
pressure gradually builds into the area. The coming cold snap should
last for some time, keeping temperatures in the long term near
normal. We won`t really start to see a warm up occur until closer to
Thursday as WAA will start to take place ahead of our next frontal
system that should arrive later Thursday into Friday based on
current guidance. With a more arctic based origin, this should be yet
another decent blast of cold air to continue trying to keep things
more winter like.
.AVIATION /04Z SATURDAY THROUGH WEDNESDAY/...
As of 700 PM EST Friday...
Through this evening...
Isentropic lift will result in bkn-ovc mid level cloudiness,
bases 7-12kft. There will also be areas of scattered light rain
associated with tempo cloud bases 4-7kft.
Fog and/or low stratus may redevelop with cigs 500 to 1000 ft.
Areas of light rain are expected to develop toward morning
associated with vbys of 1-3sm.
Forecast confidence in the near term is moderate.
.Extended Aviation Discussion...
Sub-VFR conditions at times Saturday ahead of a cold front with
showers, few thunderstorms. Front moves across Sunday with
showers and sub-VFR, with windy conditions behind it. Winds
ahead of the front will be out of the southwest Saturday into
Sunday morning, with gusty winds possible east of the mountains.
Winds then shift to the northwest Sunday with frequent gusts
25 to 35 kts areawide. May see a brief period of LLWS for
Lewisburg before winds increase tomorrow morning, and again for
BLF/LWB/BCB late tomorrow night into Sunday morning, when
surface winds begin to come down.
Flurries and MVFR cigs will linger across the mountains Monday,
otherwise expect clearing with widespread VFR by Tuesday. Winds
will also diminish Tuesday.
As of 200 PM EST Thursday...
Records for New Years Day...
Site MaxT Year MinT Year LoMax Year HiMin Year
Bluefield, WV 72 1985 0 1977 10 2018 55 1952
Danville, VA 74 1952 5 1918 27 2018 52 1952
Lynchburg, VA 74 1952 3 1918 24 1918 51 1934
Roanoke, VA 78 1952 8 1918 23 1918 51 2005
Blacksburg, VA 75 1952 2 2018 17 1918 46 1934