Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/31/21
Area Forecast Discussion
National Weather Service Birmingham AL
606 PM CST Thu Dec 30 2021
.UPDATE...
For 00Z Aviation.
&&
.SHORT TERM...
/Updated at 0105 PM CST Thu Dec 30 2021/
Through Tomorrow.
A broken line of thunderstorms persists along a weak surface
boundary oriented nearly parallel to the south of I-20. This is in
contrast to clearing skies across the northwest. There`s been plenty
of instability and moisture ahead of the thunderstorm activity with
dewpoints in the mid to upper 60s in addition to a sustained
presence of 50-60kts of eff. bulk shear per RAP mesoanalysis. This
setup lacks substantial synoptic support aloft, but thunderstorm
updrafts will continue to be sustained by the preceding unstable
airmass and robust wind fields. As such, a low potential for a few
damaging wind gusts up to 60 mph and small hail will continue
through the afternoon, and a Severe Thunderstorm Watch has been
issued through 8 PM for our southeastern tier of counties where
sfc temperatures have risen into the 80s. A few weak mid-level
mesocyclones have been observed on radar in some of the stronger
cells today, but 0-1km winds are not supportive of tornadogenesis.
With deep, southwesterly flow aloft, there`s been little southward
push and slow storm motions which has resulted in localized flooding
due to heavy rain rates of 1-3 in/hr. Storms will slowly move
towards the I-85 corridor with less flooding potential as these
areas have been mostly rain-free up to this point and storm
motions have increased slightly, but there will still be heavy
downpours and the Flood Watch will continue until 6 PM.
Showers will wane this evening with the decrease in instability, but
patchy fog is likely to develop in its wake across much of the area.
This is due to a combination of calm surface winds, and moist
surface conditions with overnight temperatures falling below
crossover temperatures. We won`t see a cool down heading into
tomorrow and in fact, there won`t be much of a temperature change at
all as the southwesterly flow continues. The remnant surface
boundary will lift northward tomorrow as a warm front and associated
isentropic lift may help produce some scattered showers and a few
rumbles of thunder, but the activity will be much less organized.
Highs will range from the lower 70s north to lower 80s south with
mostly cloudy skies.
86
.LONG TERM...
/Updated at 0214 PM CST Thu Dec 30 2021/
Rapid turnaround to return flow really starts to pick up again
Friday night into Saturday morning, with low level jet pushing 50
kts by 15z Saturday. Surface dewpoints never really drop after the
present system, and remain in the mid/upper 60s until frontal
passage Saturday night. Severe parameters highlighted in previous
discussion (and copied below) remain valid, and will continue to
monitor for severe storm/tornado potential Saturday afternoon into
early Sunday. SPC has outlooked a large Slight Risk area on Day
3, and I would not be surprised if part of that area is upgraded
in later updates.
Sunday will feature falling temperatures and probably some
lingering light precipitation as the core lobe of the upper level
shortwave moves across our area. I`ve removed the (small) chance
of snow on Sunday, as our current temperature forecast suggests
that the chance is now even smaller.
One thing to note -- there was a lot of rain in some spots
yesterday and last night, and there will be more rain to come
between now and Sunday night. Temperatures will fall quite quickly
into the 20s in much of central Alabama Sunday night. Any standing
water or areas of water seepage across roadways will likely
freeze in these areas. Plan accordingly.
/61/
Previous long-term discussion:
/Updated at 406 AM CST Thu Dec 30 2021/
Saturday and Sunday.
Warm sector conditions are progged to extend across much of the
Southeast CONUS Saturday morning after the northward surge of a warm
front the day before. This will coincide with cyclogenesis along an
active frontal zone stretched across the Mid Mississippi River
Valley. This deepening, elongated surface low is a response to the
ejection of a lead shortwave disturbance and overall amplifying
forcing aloft. Thus, increasing southwesterly flow aloft will
establish across the Deep South and will set the stage for another
record-breaking warm day across Central Alabama. Temperatures should
climb into the mid 70s to low 80s along with dewpoints in the mid to
upper 60s. This will support MLCAPE of 500-1,000 J/kg given lapse
rates of ~6 C/km. Ample kinematic fields are also expected, mainly
owing to the approach of the parent upper-level trough advancing
east across the Plains. Most guidance suggests 500 mb flow
increasing to 60-70 kts late Saturday afternoon which will produce
eff. bulk shear values of at least 60 kts across the Deep South.
However, guidance also suggests wind profiles will be mostly
unidirectional above 850 mb, but there`s a little more backed flow
in the boundary layer due to better pressure falls now progged
across the TN Valley. In fact, forecast hodographs aren`t too
dissimilar from the RADAR derived wind profiles experienced tonight
(0-1km SRH 200-300 m2/s2) within a ~50 kt low-level jet. This trend
will certainly need to be watched as the warm sector/expected
forcing will be supportive of all modes of severe convective weather
- primarily damaging wind gusts and a few tornadoes if
thunderstorms/convective modes evolve accordingly. The main threat
timing for Central AL should be mid Saturday afternoon into early
Sunday morning. Further refinements to the forecast should be
expected as mesoscale details are better resolved in the next day or
so. We`ll also continue to monitor additional threats involving
excessive rainfall/flash flooding as progged deep-layer winds run
nearly parallel to the advancement of the strong cold front. We may
also have the need for a wind advisory at some point.
40/Sizemore
&&
.AVIATION...
00Z TAF Discussion.
The strong to severe storms that impacted southern Alabama
Thursday afternoon have mostly dissipated or moved into Georgia. A
few showers remain across the far southeast, south of KTOI. The
main flight hazard overnight will be fog and low cigs. The air
mass is very moist in the low levels and skies have cleared across
areas north of I-85. This will allow the air mass to quickly cool
and saturate, with widespread LIFR conds expected between 05z and
14z. A warm front will lift northward during the day Friday and
produce sct showers and a few tstms across Central Alabama. The
increase in south winds will help erode the fog and lift the cigs,
but cigs will stay in the 1000-1500 ft range after 18z.
Note: AMD NOT SKED is appended at KBHM due to ASOS power loss until
further notice.
58/rose
&&
.FIRE WEATHER...
Unsettled weather will continue across the area with additional
round(s) of showers and thunderstorms through Saturday night.
This period of unseasonably warm and moist conditions will feature
surface winds from the south and southwest. RH values will stay
well above minimum thresholds with periods of wetting rains. A
strong cold front is expected to sweep through the area late
Saturday night into Sunday. This will be followed by much colder,
drier air into early next week.
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 57 74 61 76 54 / 20 50 40 90 100
Anniston 60 76 64 78 59 / 20 50 30 80 100
Birmingham 61 75 66 77 56 / 20 50 20 90 100
Tuscaloosa 62 76 66 78 53 / 20 50 20 90 90
Calera 62 76 66 78 58 / 20 50 20 80 100
Auburn 64 76 65 76 63 / 20 40 10 50 90
Montgomery 65 80 67 81 65 / 20 40 10 60 90
Troy 67 81 67 80 66 / 30 30 10 40 90
&&
.BMX WATCHES/WARNINGS/ADVISORIES/...
None.
&&
$$
Area Forecast Discussion
National Weather Service Des Moines IA
917 PM CST Thu Dec 30 2021
...Updated for Weather Trends over the Next 24 Hours and
Discussion on 18z/00z Guidance for Saturday`s Snow...
.UPDATE...
Issued at 917 PM CST Thu Dec 30 2021
An overall quiet evening before a period of more active weather
to end 2021 and start 2022. The main concern the rest of tonight
is fog development as the low level flow just above the surface
becomes southerly and weak warm air advection begins. Forecast
soundings and cross sections show this thin, highly saturated
layer arriving quickly toward and after 6z/midnight tonight. The
depth of the saturation is below a kilometer (km), which would not
favor drizzle/freezing drizzle. However, 18z HREF probs of 1/2
mile visibility rise quickly after 6z and are 60-80% by 9z for
areas near and east of I-35 from northern MO into southeast MN to
a DEH to OTM line. 15z SREF has similar timing and high probs of
vsby less than 1 mile in roughly the same area. Therefore, have
issued a dense fog advisory for areas near and east of I-35.
Messaging within the advisory also includes the possibilitiy of
slick roadways. With temperatures below freezing and the juicy,
dense fog, could have accretion/freeze on contact with roadways.
Also have seen observations and heard from our neighboring NWS
meteorologists of freezing mist at La Crosse and patchy freezing
drizzle in Quad Cities service area.At this time, not expecting
that in our area, but will monitor. This advisory will run
through 9a Friday, though it may need to be extended/adjusted in
area and will allow the overnight and dayshift crews to assess as
needed.
On the heels of the dense fog will be concern for drizzle/freezing
drizzle (dz/fzdz). NAM and CMC both have the typical light QPF
signal which is indicative of the moist low levels/dz/fzdz.
Compared to tonight into early Friday, cross sections show the
depth of the moisture increasing to around 850mb/1km by 18z over
northern Iowa and mainly east of I-35. Lift within this saturated
layer is weak, but would be sufficient for dz/fzdz. Current
forecast highlights this potential to the northeast of DSM, but
have pulled the dz/fzdz back to a FOD/DSM/OOA line given RAP/HRRR
sounding depth of saturation.
As for the New Year`s Day snowstorm, the 18z ECMWF and its ensemble
mean are a bit farther south than its previous run and south of the
18z GFS/GEFS. The GEFS still has some members with northern
solutions/spread snow farther north into northern Iowa/near
Minnesota border. In comparison, the ECMWF members do not show that
northern solution/spread and are largely locked into southern
Iowa. Away from global models, high resolution models such as the
21z RAP and 00z HRRR show the highest totals south of I-80 and a
minimum of a tenth to two tenths higher QPF. Obviously, your
choice of snow ratios will dictate snowfall amounts from these
given models. Forecast soundings continue to show a deep nearly
dendritic/dendritic layer with moderate lift that will enhance
snowfall rates, ratios, and amounts. Both the RAP and HRRR show
the DGZ depth over 15kft over our southern forecast area, which is
impressive. Thus, snow ratios may need to be boosted from their
current values, especially as we near the event. Lastly, the 18z
HREF and extrapolated 12z HREF indicate that there should be a
period of snow rates exceeding 1"/hr with these snow rates driving
visibility to under a half mile at times.
&&
.DISCUSSION.../Tonight through Thursday/
Issued at 304 PM CST Thu Dec 30 2021
Key Messages:
- Dense fog potential overnight into Friday along with some
Freezing Drizzle over northern Iowa Friday.
- Dangerous wind chills Friday night through Sunday morning.
- heavy snow and blowing snow for parts of central and southern
Iowa late Friday night into Saturday evening.
Broad area of stratus and some fog has lingered over much of central
Iowa today. The stratus has been clearing over western Iowa as the
steering flow has become more westerly. This clearing should
continue to progress east into this evening before the steering flow
becomes more southerly overnight. Expect the stratus and some fog to
expand again overnight as the flow becomes more southerly again and
warm advection commences along with the arrival of higher dew
points. A couple of concerns overnight and into Friday is the
development of widespread dense fog and the potential for freezing
drizzle across parts of the area on Friday. A dense fog advisory may
be required later tonight but will leave for the evening shift as it
maybe a see the whites of its eyes type of scenario to capture the
areal coverage. The same can be said for the freezing drizzle
potential on Friday. The warm advection and subsequents vertical
ascent through the near surface saturated layer likely will lead to
sufficient collision coalescence for freezing drizzle development
and possibly some icing. The Waterloo/Ceder Falls and surrounding
areas appears to be the most prone area on Friday for icing.
Arctic air will begin to spill into northern Iowa Friday night with
wind chill values diving to 20 below to 35 below zero mainly north
of Highway 30 by Saturday morning. Given the New Years Eve
festivities and this is the first true taste of Arctic cold this
season, have issued a wind chill advisory for parts of northern Iowa
through Friday night. These dangerous wind chills will extend into
Saturday thru early Sunday and headlines will be readjusted as the
Winter Weather headlines are finalized. That is due to the parts of
the Wind Chill headline area are covered in Winter Weather
headlines.
The other issue is obviously the winter storm set to impact parts of
Iowa late Friday night and into Saturday evening. With this being
and upper low swinging into the region with the surface low well to
the south and an Arctic High pressure system filtering dry air in from
the north, there remains the typical temporal placement of the
deformation snowband uncertainties. Still expecting snow to begin
late Friday night into southwest Iowa and will expand northeast
through central Iowa and into east central Iowa. There will likely
be a sharp cutoff to the main accumulation band along the north edge
due to the northerly winds drawing dry air from the Arctic High to
the north. There remains some uncertainty on the depth of the dry
air coming in from the high as there have been a few solutions
suggesting a more shallow dry intrusion which would allow for snow
to gravitate a bit further north. Therefore, will continue to
monitor that situation. Further south, especially Highway 30 and
south, a deep dendritic layer from near surface all the way to near
600 mb will setup for a 3 to 5 hr window that could lead to 1"+/hr
rates during that time due to increasing snow ratios that likely
will top 20 to 1 for a period. Agree with WPC that the the potential
for CSI is low with cross section showing a lack of negative EPV or
the back bending of Theta-e. The heaviest snowfall is expected to
occur from mid morning through mid afternoon then gradually diminish
in intensity after that time. Still expect 6+ inches of snow for a
large portion of southern Iowa and possibly central Iowa. This snow
will be fluffy and easy to blow around. Expect increasing wind of 15
to 25 mph with gusts over 35 mph at times will create significant
blowing and drifting of snow. Not blizzard criteria but still bad
given the first winter storm. Will default from typical 6" in 12 hr
criteria to 4" in 12hr along with sustained 25 mph wind and blowing
snow for warning upgrade decisions. Will have a partner webinar on
Friday at 11 am.
The Arctic cold blast will persist into Sunday morning. Will have to
reorient wind chill headlines again as the Winter Storm winds down.
Warm advection arrives for a brief period for Monday before colder
weather arrives again for Tuesday and into mid next week. The focus
for the forecast remain through this weekend.
&&
.AVIATION.../For the 00Z TAFS through 00Z Friday evening/
Issued at 533 PM CST Thu Dec 30 2021
Main aviation concern is restrictions from stratus/fog that will
expand overnight into Friday. DSM, MCW, and OTM will soon clear
from the stratus, but only for a short period before stratus and
fog surge back to the west toward and after midnight. Restrictions
will likely drop into LIFR or lower across central and eastern
Iowa after midnight through mid-morning Friday. Visibilities
should improve mid to late morning Friday, but low ceilings will
remain. Most areas should improve into MVFR, though IFR could
linger over eastern Iowa.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory from 3 AM to 9 AM CST Friday for IAZ006-007-
016-017-025>028-036>039-047>050-059>062-072>075-083>086-094>097.
Winter Storm Watch from Saturday morning through Saturday
evening for IAZ047>050-057>062-070>075-081>086-092>097.
Wind Chill Advisory from 9 PM Friday to 6 AM CST Saturday for
IAZ004>007-015>017-023>028-033>036-044>046.
&&
$$
UPDATE...Ansorge
DISCUSSION...Donavon
AVIATION...Ansorge
AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
929 PM CST Thu Dec 30 2021
.UPDATE...
Issued at 916 PM CST Thu Dec 30 2021
00Z guidance continues to support the development of a strong
frontal band by Friday morning across portions of central South
Dakota into eastern Minnesota. Already late this evening, we`re
beginning to see the first signs of 700 mb lift as a extensive
cloud layer is starting to develop over south central South
Dakota.
Latest NAM/RAP and other CAMS support snow developing over the
western Dakotas after midnight, with 850mb frontogenesis rapidly
intensifying by daybreak along the White River northeastward
towards Huron and Watertown as a subtle 500 mb vorticity max
slides into central SD. Snow will quickly progress eastward after
sunset and moves east of the area early in the afternoon.
What`s a bit concerning is the potential for both short term
snowfall rates pushing 0.5-1" per hour, and a sounding that
supports a substancial portion of the lifting layer within the
DGZ. All that said, we could see SLR pushing 18-20:1 at times.
With QPF trending upwards, this has increased the potential for a
band of 2-5" of snow.
With winds behind the arctic front increasing up to 25-30 mph at
times, have opted to issue a winter weather advisory for snow and
blowing snow potential.
&&
.SHORT TERM...(This Evening through Friday)
Issued at 328 PM CST Thu Dec 30 2021
Front continues to work across the area this afternoon, with clear
skies allowing us to see the limited snow cover left across our CWA.
Ahead of the front, temperatures as of 20z are in the upper 30s to
40 in KSUX with southerly flow. Back to the north and west, however,
KHON is at a chilly 20 degrees with northwesterly flow.
Tonight, temperatures drop with the northerly flow in place and cold
air advection (CAA) beginning to work into the area. Will likely see
low temperatures below 0 near/along Highway 14, with single digits
to lower teens elsewhere.
By daybreak on New Year`s Eve (NYE), winds are expected to be on the
increase as the surface pressure gradient increases due to a
strengthening low pressure ejecting from CO and high pressure to our
north. Meanwhile, a quick moving wave passing through central SD
looks to bring a chance for light snow to areas along and north of a
Gregory county, SD to Lyon county, MN during the morning and early
afternoon Friday. Models this morning/early afternoon, with the
exception of the NAM, have shifted this focus of the frontogenesis a
bit further to the northwest. Given this, as well as uncertainty in
how quickly dry air with cut off moisture through the lower levels
and the exact location of the best forcing, have left pops in the
chance category for now. Expect accumulations to be light, with less
than an inch for most (although areas in the narrow band could see
around 2 inches). 18z HRRR soundings for KHON do show some lift in
the upper tier of the dendritic growth zone (DGZ), and maintain
saturation through the DGZ which could lead to some higher snowfall
rates by the afternoon. Could see some patchy blowing snow Friday
afternoon with the brisk winds for areas which receive new snow.
Temperatures on NYE could rise a bit during the day, but are
generally expected to remain steady and fall in the afternoon/early
evening. With the cold temperatures and brisk winds, expect wind
chills to reach dangerous levels by the evening, especially
near/along Highway 14 and the Buffalo Ridge.
.LONG TERM...(Friday Night through Thursday)
Issued at 328 PM CST Thu Dec 30 2021
Aforementioned southern low pressure is expected to swing through
the Central Plains during Friday night into Saturday. Areas south of
I-90, particularly south of Highway 18, will likely see some light
snow to start 2022. Amounts for this system also look to remain
light, with less than an inch expected. There also is some
uncertainty in the northern extent of this system given dry air
working in from the north.
The bigger story and likely bigger impact with this system passing
to the south is the cold, as high pressure slides in from the north.
As the final chapter on 2021 closes and we start the first chapter
of 2022, temperatures for all except possibly the Highway 20
corridor will be below zero. Lows Friday night fall into the single
digits and teens below. These cold temperatures and brisk
north/northwesterly winds cause wind chills to remain at dangerous
levels Friday night through Saturday. In collaboration with
neighbors, have issued both Wind Chill Warnings and Wind Chill
Advisories for this time frame. Those with plans to ring in 2022
outdoors will want to bundle up with extra layers as frostbite could
occur quickly. Highs on Saturday look to be in the single digits
either side of zero as high pressure remains in place, with lows
Saturday night lows in the single digits and teens below zero.
Ridging and warm air advection (WAA) begin to move into the area for
the second half of the weekend into early next week, which should
help to moderate temperatures (barring any snowpack) near to above
normal. Models diverge in the synoptic pattern for the middle of the
week, although all show some sort of wave/trough at different
points, with much colder temperatures returning. Thus, have left the
blend as is.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 507 PM CST Thu Dec 30 2021
A few concerns tonight in the aviation forecast, first of all with
the potential of backbuilding stratus or fog into NW Iowa later
tonight. Models continue to hint at strong potential for
development, but also may not be factoring in lack of snow cover.
Will remain optimistic in this area tonight.
Otherwise, biggest concern will be with potential for strongly
forced banded snowfall event beginning by daybreak Friday and
ending early afternoon. Models remain bullish on potential for
MVFR to IFR ceilings and visibility at times along a line from
Chamberlain to Brookings through the morning. Snow potential of
1-4" may be possible in some areas.
Arctic surge of cold air will also drag stratus southward through
the day, and with low-lvl temperatures crashing, we may likely
deal with flurries or even light snow over much of the area in the
afternoon.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Wind Chill Advisory from 9 PM Friday to noon CST Saturday for
SDZ050-052>071.
Wind Chill Warning from 6 PM Friday to 6 PM CST Saturday for
SDZ038>040.
MN...Wind Chill Advisory from 9 PM Friday to noon CST Saturday for
MNZ098.
Wind Chill Warning from 6 PM Friday to 6 PM CST Saturday for
MNZ071-072-080-081-089-090-097.
IA...Wind Chill Advisory from 9 PM Friday to noon CST Saturday for
IAZ001>003-012>014-020>022-031-032.
NE...Wind Chill Advisory from 9 PM Friday to noon CST Saturday for
NEZ013-014.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Wind Chill Advisory from 9 PM Friday to noon CST Saturday for
SDZ050-052>071.
Winter Weather Advisory from 6 AM to 3 PM CST Friday for
SDZ038>040-052>054-057-058.
Wind Chill Warning from 6 PM Friday to 6 PM CST Saturday for
SDZ038>040.
MN...Wind Chill Advisory from 9 PM Friday to noon CST Saturday for
MNZ098.
Wind Chill Warning from 6 PM Friday to 6 PM CST Saturday for
MNZ071-072-080-081-089-090-097.
IA...Wind Chill Advisory from 9 PM Friday to noon CST Saturday for
IAZ001>003-012>014-020>022-031-032.
NE...Wind Chill Advisory from 9 PM Friday to noon CST Saturday for
NEZ013-014.
&&
$$
UPDATE...Dux
SHORT TERM...SG
LONG TERM...SG
AVIATION...Dux
Area Forecast Discussion
National Weather Service Louisville KY
933 PM EST Thu Dec 30 2021
.Forecast Update...
Issued 930 PM EST Wed Dec 29 2021
Have seen some clearing of the low clouds across most of central
Kentucky, but we do have some passing high clouds down there. Latest
hi-res guidance indicates that the cloud deck should stop its
northward progression and then linger most of the night. Just south
of the current cloud belt, we do have some observing stations
starting to show lower visibilities. Some fog may briefly form over
the early overnight hours, but as winds pick up from the south
expect visibilities to improve.
Looking ahead to the early runs of the high-res models coming in
now, the 00Z HRRR has rains blossoming in the evening hours over a
wide swath of the region, with some heavier more convective returns
near the KY/TN border overnight. Per forecast soundings, that
convection would be elevated. As you go into the day Saturday, that
model shows additional waves of rain would move through the region
before a line of storms comes through late afternoon/early evening.
Think this latter line has the best chance of having severe winds
and isolated quick spin-up tornadoes...matching up the best shear
with some slight surface-based instability. The line SPC drew up for
their slight risk area matches up real well with this run of the
HRRR for the threat area.
Thus the focus on the heavy rain flood threat with an outside shot
at some damaging winds still looks good. Made some slight tweaks to
the gridded forecast, but plan no changes for this update.
&&
.Short Term...(This evening through Friday)
Issued at 321 PM EST Thu Dec 30 2021
Mildly amplified almost zonal upper flow continues to stream from
the west-southwest to the east-northeast over the Lower Ohio Valley.
At the surface, a low pressure center sits anchored to the eastern
side of the Rockies in eastern CO as high pressure remains east of
Florida over the Atlantic. This is resulting in a weak pressure
gradient and light southwest winds through the CWA. A strong
inversion is capping moisture under 900 mb. This has allowed the low
level cloud cover to hold on all day and limit temperatures to the
50s and provided pockets of drizzle.
Tonight, expect more of the same as the inversion is expected to
keep stratus over the region through the night. The exception could
be areas to the southeast towards Knoxville, TN. Parts of the Lake
Cumberland region could see ceiling lift.
The aforementioned surface low is expected to break free from the
Rockies and drift eastward towards Chicago. Winds back towards the
south across southern IN and central KY, and with winds remaining
light, don`t expect much WAA. Lows will likely only drop to the mid
40s in southern Indiana to near 50 along the TN border.
Tomorrow, as the moving surface low moves from KS to Chicago, the
surface pressure gradient increases causing winds to become breezy
during the afternoon with gusts near 20 mph. WAA is expected to lift
high temperatures into the 60s. Precipitation chances tick up as the
surface low`s trailing cold front approaches from the northwest. Any
remaining stratus will likely cause drizzle before rain chances
increase late in the day.
.Long Term...(Friday night through Thursday)
Issued at 344 PM EST Fri Dec 30 2021
Friday Night through Thursday...
...HEAVY RAINFALL EVENT LIKELY FRIDAY NIGHT AND SATURDAY...
...SOME WINTRY WEATHER POSSIBLE ON SUNDAY...
====================================
Synoptic Overview
====================================
In the near term, strong upper trough axis off the southern
California coast is forecast to move eastward into Baja California.
As this occurs, secondary upper trough axis is forecast to move
through the Pacific northwest. These two upper troughs are forecast
to phase over the southwestern US and then move into the southern
Plains. Lee side cyclogenesis is forecast early Saturday morning in
the southern Plains with the surface low moving east-northeast along
a strong baroclinic zone oriented from the southern Plains
northeastward through the Ohio Valley. Strong mid-level flow is
expected ahead of this trough axis along with a strong southerly
fetch of rich Gulf moisture. As the system moves northeast,
widespread heavy rainfall with embedded thunderstorms will be seen
across the Ohio Valley mainly from Friday night through Saturday
evening. Excessive rainfall is very likely with 2-4 inches of
rainfall expected along the surface low track. Some strong to
possibly severe storms may affect the Tennessee Valley and portions
of the southern Ohio Valley during the period. As the system pulls
off to the east, a sharply colder airmass will move into the region
by Sunday. As mid-level trough axis pushes through, some light
snows will be possible on Sunday across the region. A tranquil, but
cold period of weather is expected for early next week before the
next weather system approaches by next Thursday.
====================================
Model Discussion/Trends/Preferences
====================================
The 30/12Z model suite seems well initialized with no glaring
issues. The overall model solutions continue to trend a bit slower
with the trough coming through the Baja of California and subsequent
phasing over the southwest US. The global runs of the GFS/GEM/Euro
continue to track the surface low through the center of of KY on
Saturday. Those global model QPF`s are in reasonable agreement with
a swath of 2-4 inches of rainfall. In general, the global models
area really hitting the area of KY between the Ohio River and the
Parkways with the axis of heavier rainfall. The Euro Extreme
Forecast Index is strongly suggestive of a heavy rainfall/flooding
event aligned along and north of the Parkways. Shift of Tails are
greater than 2 that adds a higher level of confidence of an extreme
event for late December and early January.
While overall confidence in the model output is high on the flood
threat, the severe threat is much more complex and contains
significant uncertainty. The global models keep the bulk of the
severe threat across far southern KY and into the deep south through
much of the event. However, the last few runs of the NAM have kept
the aforementioned surface low a bit further to the north. This
would allow for much more of the region to get into the warm sector
with a highly sheared environment with localized low-level backed
flow. If the NAM solutions were to materialize, a severe weather
threat would be more likely Saturday afternoon. The reason for the
NAM`s northern track is because it was ejecting the Baja/SW US wave
slower allowing the system to gain latitude much more quickly than
the faster GFS/Euro.
As of this writing, we have leaned heavier on the GEM/Euro/GFS
solutions with a more southern low track. This results in a
forecast that hits harder on the flooding/excessive rainfall threat
with a lesser threat of severe convective weather. However, we will
continue to monitor the subsequent runs of the NAM and HREF guidance
as it becomes available.
Overall the models agree with a surge of colder weather coming into
the region for Sunday. As the upper trough slides into the region
some light wintry weather is possible on Sunday.
====================================
Sensible Weather and Impacts
====================================
Widespread showers should develop rather quickly Friday evening
mainly from northwestern AR northeastward into Kentucky. This will
be aided by intense mid-level jet axis pushing into the region above
a strengthening low-level jet axis. While the jet structure is
impressive, the main uncertainty remains around potential surface
based instability. Soundings do show some warming just off the
surface that may keep surface based instability in check. It
appears that higher amounts of surface based instability will remain
to our south and southwest. Nonetheless, some strong/severe storms
will be possible across southern KY Friday evening if surface based
instability can get established. Right now, overall confidence
remains very limited due to uncertainties in the mesoscale evolution
and multiple model differences here.
Going into the day on Saturday, widespread convection is expected to
be ongoing across the region. We may see a break in the
precipitation across southern KY during the morning hours as much of
the forcing retreats to the north along the warm front, so we still
think that plenty of rainfall along and north of the Parkways is
likely throughout the day. As the surface low heads northeast, we
expect more widespread convection to develop and move through the
region. With much of the precipitation moving east-northeast along
the surface boundary, training of convection will be possible,
especially in areas along either side of the WK/BG Parkways. The
global models keep much of the area rather stable near the surface
to preclude the development of severe thunderstorms. Again, the NAM
runs were outliers taking the low further north and possibly
resulting in a second round of severe storms Saturday afternoon and
evening. The CIPS analogs, SPC Chiclets, CWASP parameters, and the
Euro Extreme Forecast Index still insistent on keeping much of the
severe weather contained to our south. Our current thinking is
that we`ll be dealing with primarily heavy rainfall producing
convection with some gusty winds embedded in the strongest cores.
The convection will end from west to east as a cold front will move
across the region Saturday night. If the cold front is slower to
get to the region that advertised, as mentioned above, we could have
another round of strong storms before the colder air rushes into the
region.
As for rainfall amounts, there is very good agreement in the models
for widespread 2-4 inch rainfall amounts across the region. The
axis of heaviest QPF looks to fall along and perhaps just north of
the Western KY and Bluegrass Parkways. In this small corridor of an
area, we expect primarily 3-4 inch amounts. Slightly lesser amounts
will be seen further away from these areas (like our far northern
row of southern Indiana counties and perhaps parts of southern KY).
Given the relatively good model agreement and strong signal from the
Euro EFI, a Flood Watch has been posted for the entire area for
Friday night through Saturday night.
On Sunday, the cold front will move through the region and colder
air will usher in from the northwest. Highs on Sunday will occur
probably around midnight Sunday and then fall throughout the day.
Overall, the models are a little slow at bringing the cold air into
the region, but temperatures should start off around midnight in the
mid-upper 50s and then crash to near freezing by evening. As the
upper trough cruises into the region, additional lift will result in
some light snows developing across the area. It will be another one
of these "cold chasing the back edge of the precipitation" events.
However, it is possible that some very light accumulations will be
possible with this activity. However, given the complexity of the
overall system, it remains a bit early to get too wrapped up about
this part of the forecast at this time.
For early next week, a period of tranquil but cooler weather is
expected. Highs on Monday will likely stay in the 30s with lows
upper teens to low 20s. However, a southerly flow pattern will get
re-established and allow temps to warm back into the mid-upper 40s
by Tuesday and then into the 50s by Wednesday. The next weather
system is expected to arrive by Thursday.
====================================
Forecast Confidence
====================================
Heavy Rainfall/Flooding Threat : Medium-High confidence Severe
Weather Threats : Low-medium confidence
Wintry Weather Threats (Sunday): Low confidence
====================================
Extended Range Discussion
Beyond Thursday and into Week Two
====================================
Looking into far extended, the general trend of turning colder
across the eastern US looks likely. However, the depth and duration
of that cold contains considerable uncertainty. The overall pattern
will likely feature fluctuations of temperatures with warm ups as
systems approach followed by cool downs in the back side. Each
successive cool down may be a bit stronger in nature. In terms of
the hemispheric pattern, we should be somewhere in the phase 7/8 on
the MJO and for a La Nina winter that would argue for a colder
regime across the eastern US. However, there are some reliable data
sources that suggest that the MJO could get stuck or regress back
into Phase 7. Teleconnection wise, the longer term looks to feature
a neutral to slightly positive NAO, EPO, and AO with the PNA
remaining negative, but increasing to near neutral by mid-month. We
still have to deal with the La Nina background state which remains
in full swing and the -PDO pattern is likely to keep the SE ridge in
play for some time. The models have been way too fast in trying to
swing the MJO through phase 7/8/1 and I expect them to continue to
be too fast with that push. So overall, while the models and
ensembles do suggest a colder pattern emerging, it will probably be
at least mid-month before things get into a more persistent cold
pattern.
However, the idea of a transition to a colder regime across the east
will be in jeopardy if the MJO gets stuck in phase 7 and doesn`t
make a move into phase 8 or phase 1. In that case, we may find
ourselves in a large SW-NE oriented baroclinic zone with the cold to
our north and west, and continued warmth to our south and east. This
type of pattern would yield a high amount of precipitation across
the Ohio Valley.
In terms of signal analysis, earlier week analysis suggested a
signal passage toward the end of the extended period (day 7-8 or 1/6-
7th) which could bring some impactful weather to the region. Behind
this system another modified cold airmass will rush into the region
at least through the weekend of the 8-9th. Another ramp up in temps
is likely as the next signal passage is on course for arrival around
1/11-12th followed by another around 1/14-15th. It may be the 14-
15th signal passage that finally brings a bit more of a persistent
cold pattern to the Ohio Valley for maybe 10-14 days. After that,
it is very possible for the MJO to get another run through phase
3/4/5 which would result back to a warmer pattern possibly in
February.
&&
.Aviation...(00Z TAF Issuance)
Issued at 605 PM EST Thu Dec 30 2021
IMPACTS:
- IFR/LIFR conditions possible next few hours at SDF but
likely at HNB
- Winds will pick up from the south Friday afternoon
- Showers and a few storms possible late in SDF TAF period
DISCUSSION:
Active weather period will commence with low pressure
approaching from the central Plains Friday afternoon. Ahead of that
system, residual low-level moisture will keep some chances for lower
cigs in place, especially at HNB all night. Will have to watch for
transitions at the other terminals thru the night. By Friday evening
expect a cold front approaching the region to bring a swath of heavy
rains and possible storms.
CONFIDENCE:
High confidence in all elements at HNB, Medium at
SDF/LEX/BWG through the morning hours then Medium High in the
afternoon and evening hours.
&&
.Hydrology...
Issued at 354 PM EDT Thu Dec 30 2021
Flash flooding and more widespread flooding will be possible over
the region from Friday night through Saturday night as showers and
thunderstorms are expected to move through the region. Our current
forecast has widespread 2-4 inch rainfall amounts and some
localized areas could see 5+ inches of rainfall. This would be
especially true in areas that training of storms over the same area.
As far as the area rivers are concerned, the NAEFS river ensemble is
suggesting minor flooding of river forecast points across central
Kentucky. This would include forecast points like Rochester Ferry
and Woodbury on the Green River. Boston on the Rolling Fork River.
Peaks Mill (Frankfort) on the Kentucky River and Paris on Stoner
Creek. Should the 3-4 inch rainfall axis develop as currently
forecast, there is a chance that Peaks Mill could go into moderate
flood stage.
Excessive runoff will move into the larger river basins as we head
through the weekend and into next week. There is potential for some
minor flooding at Tell City and possibly at Cannelton on the Ohio
River by early next week.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...Flood Watch from Friday evening through Saturday evening for
INZ076>079-083-084-089>092.
KY...Flood Watch from Friday evening through Saturday evening for
KYZ023>043-045>049-053>057-061>067-070>078-081-082.
&&
$$
Update...RJS
Short Term...KDW
Long Term....MJ
Aviation...RJS
Hydrology....AMS/MJ
Area Forecast Discussion
National Weather Service Memphis TN
921 PM CST Thu Dec 30 2021
.UPDATE...
Fog is already beginning to develop across the Mid-South at this
time. Expect that visibilities will continue to drop during the
overnight hours as a secondary warm front is nearly stationary
over Central Mississippi. As a result, issued a Dense Fog
Advisory for the entire Mid-South. The front will lift northward
on Friday and will become stationary near the MO/AR and KY/TN
state borders. Expect showers and thunderstorms to begin
developing along the front around sunset tomorrow night and will
continue until the front begins moving east late Saturday
afternoon. With the extended period of convection expected, went
ahead and issued a Flood Watch for Northeast Arkansas, the
Missouri Bootheel, and West Tennessee. Otherwise, just made some
minor tweaks to temps and sky conditions.
KRM
&&
.DISCUSSION.... /issued 352 PM CST Thu Dec 30 2021/
Mild temperatures and mostly dry weather will prevail through
tomorrow afternoon. Some pop up showers and sprinkles may dot the
area tomorrow morning, but any precip would be light. Near record
warm temps again tomorrow afternoon with highs in the low to mid
70s due to deep, persistent southerly flow as well as a warm front
lifting north. Fog may develop in the early morning hours as
well, and could be dense in some areas. The warm front stalls to
our north tomorrow afternoon, leaving us with ample warmth and
moisture to set up a severe weather event to ring in the New Year.
By tomorrow evening, the aforementioned frontal boundary will
finally be overtaken by an incoming strong cold front. This will
encourage strong to severe thunderstorms to develop ahead of the
front as it approaches tomorrow night. Most of the area is under a
Slight Risk of severe weather both Friday night and Saturday. The
details are still slightly fuzzy on the setup for specific modes
of severe weather (tornadoes, hail, etc) but confidence is high
that this system will be a heavy rain- maker. Near record high
PWAT values for this time of year combined with a relatively slow
moving system will set the stage for an Excessive Rainfall event
Friday night and continuing well into Saturday. QPF amounts of up
to 3" will be possible with this system in the northern parts of
our CWA near the MO Bootheel.
Behind the cold front associated with the severe weather, a blast of
cold air moves in to shock the Mid-South late Saturday night into
Sunday morning with the sudden arrival of winter. Lows will plunge
into the 20s Sunday morning, struggling to climb out of the 30s
by the afternoon. Timing of the front is still uncertain, but if
the cold air catches up with the lingering precip, a wintry mix
will be possible on Sunday. Models are fairly split on the exit
timing of the front, so carried 30-40% PoPs on Sunday and thus
have some wintry precip in the forecast as well. Temperatures will
be even more frigid Monday morning, even getting down to the
upper teens in some rural areas.
In the extended forecast, temperatures begin to moderate to more
normal values for this time of year and we have a mostly dry period
for several days as high pressure builds in.
CAD
&&
.AVIATION...
00Z TAFs
IFR ceilings to start the JBR TAF, left over from earlier. With
cooler temps under the stratus, dewpoint depressions were less
than 5F. Should clearing occur, IFR visibility may settle in,
though likely limited by mixing.
East of the MS River, including MEM, setup is more optimistic, but
complicated by clearing this afternoon, and more importantly,
modest low level mixing through the night. This may limit
visibility reductions to -SHRA / -DZ, along an elevated warm
front after 09Z. The accompanying surface warm front will approach
MEM in the 11-13Z time frame, per NAM surface theta-e prog. This
suggests a brief IFR potential. The HRRR departs from consensus in
maintaining IFR ceilings in the mid/late morning at MEM. The 00Z
TAF does give a nod to the more pessimistic HRRR, maintaining
MVFR through 17Z. Low level mixing should be strong and
sufficiently deep by 18Z to support prevailing VFR.
PWB
&&
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Dense Fog Advisory until 9 AM CST Friday for Clay-Craighead-
Crittenden-Cross-Greene-Lee AR-Mississippi-Phillips-
Poinsett-St. Francis.
Flood Watch from Friday evening through Saturday afternoon for
Clay-Craighead-Crittenden-Cross-Greene-Mississippi-Poinsett-
St. Francis.
MO...Dense Fog Advisory until 9 AM CST Friday for Dunklin-Pemiscot.
Flood Watch from Friday evening through Saturday afternoon for
Dunklin-Pemiscot.
MS...Dense Fog Advisory until 9 AM CST Friday for Alcorn-Benton MS-
Calhoun-Chickasaw-Coahoma-DeSoto-Itawamba-Lafayette-Lee MS-
Marshall-Monroe-Panola-Pontotoc-Prentiss-Quitman-
Tallahatchie-Tate-Tippah-Tishomingo-Tunica-Union-Yalobusha.
TN...Dense Fog Advisory until 9 AM CST Friday for Benton TN-Carroll-
Chester-Crockett-Decatur-Dyer-Fayette-Gibson-Hardeman-
Hardin-Haywood-Henderson-Henry-Lake-Lauderdale-Madison-
McNairy-Obion-Shelby-Tipton-Weakley.
Flood Watch from Friday evening through Saturday afternoon for
Benton TN-Carroll-Chester-Crockett-Decatur-Dyer-Fayette-
Gibson-Hardeman-Hardin-Haywood-Henderson-Henry-Lake-
Lauderdale-Madison-McNairy-Obion-Shelby-Tipton-Weakley.
&&
$$
AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
900 PM EST Thu Dec 30 2021
.SYNOPSIS...
A stationary front over the northern portions of NC will sink south
late tonight before lifting back to the north as a warm front Friday
night. A strong cold front will then sweep across the area late
Sunday.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 900 PM Thursday...
At 00Z a stationary front was analyzed from north of Greensboro to
Roxboro to Raleigh to Goldsboro, marked by mid 60s temps/dewpoints
at RDU and mid 50s and a northeast wind at Roanoke Rapids. Earlier
rain in the south has moved off to the east as a notable shortwave
on water vapor clears off mid/high level moisture. The GSO raob
showed substantial erosion of a capping inversion near 850mb, which
may result in some weak destablization ahead of a modeled but hard
to observe disturbance that should be crossing the NC mountain at
the moment. The RAP and HRRR have been consistent in showing
scattered showers by 03-05Z, though with varying intensity. Given
the amount of observed mid-level drying and perceived weak
disturbance, the update will remove the mention of thunder and keep
POPs to chance. Behind the disturbance, the frontal zone will sink
south through the Piedmont between 09-15Z. With additional clearing
and a weak pressure gradient, fog should develop north of HWY 64,
even with dewpoints beginning to fall. Some of the fog could be
dense, though a light wind may be the limiting factor. Lows will be
in the mid 50s NW to lower 60s SE.
&&
.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
As of 325 PM Thursday...
At upper levels, a weak ridge will build across the East Coast, and
the broader upper trough is now looking like it will be slower to
approach the East Coast. As a result, have removed pops from western
counties on Friday, although the upper trough will still approach
the region Friday night. There is a wide gradient of pops across the
forecast area late Friday, from slight chance pops across Sampson
County up to high chance pops in the Triad. Friday`s highs should be
similar to today`s, except values will be warmer across the
northeast with the front having lifted back to the north. Friday
night`s low will once again be in the mid-50s to mid-60s.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
As of 250 PM Thursday...
...Unseasonably warm conditions through the weekend...
The New Year will start out wet for portions of Central NC as the
approaching cold front moves across the Mississippi and Ohio valleys
early Saturday morning. The ridge over the Southeast US will help
keep mainly the eastern portions of NC dry for Saturday as the
approaching strong cold front will move into the Mid-Altaic region
Saturday night. Early Sunday morning the rain will return with best
chances of rain everywhere Sunday day through Sunday night. The
latest model runs show increasing instability Sunday afternoon as
the cold front crosses the region, thus a chance of thunderstorms is
possible everywhere early Sunday morning and into the afternoon.
Wind gusts up to 30 mph and heavy rain fall are expected hazards as
the front moves through. Chance of rain decreases from west to east
late Sunday night and early Monday morning as the cold front exits
the region. As the cold front exits early Monday morning, much
colder and drier air will follow. High pressure will dominate the
region Monday and Tuesday before lifting northeast. Rain chances
return late week as a weak shortwave tries to move across the Mid-
Atlantic, but low confidence as it is still far away.
Well above average temperatures for the weekend with highs in the
upper 60s and 70s. After the cold front moves through, temperatures
will be near normal with highs in the 40s and 50s for Monday and
Tuesday. By late week temps will slightly warm into the mid 50s to
mid 60s. Monday night will be the coldest night with lows in the mid
to upper 20s across the region. Lows the rest of the week will be
low 30s to low 40s.
&&
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
As of 715 PM Thursday...
Forecast confidence is medium. Earlier rain around FAY has moved
off to the east and conditions range from (briefly) VFR around FAY
to MVFR around INT/GSO and LIFR from RDU to RWI. Additional showers
are possible overnight as an upper wave crosses the area, with
periods of drizzle from GSO to RDU and northeast while ceilings
likely lower back to IFR/LIFR area-wide by 03Z. The more uncertain
period of the forecast will be late night as skies somewhat clear
behind the upper wave and a relatively stationary boundary extending
from north of GSO to TDF-RDU-GSB sinks south. With light winds,
conditions should be favorable for fog after 09z and the fog could
be locally dense, at least briefly, at INT/GSO/RDU. This has been
reflected in the latest TAF. VFR conditions are then expected to
return from west to east after 15Z.
Outlook: A warm front will lift through the region Friday night,
bringing another round of restrictions and scattered showers. While
conditions should briefly dry out Saturday, widespread
moderate/heavy rain and restrictions are expected Saturday night and
Sunday. Showers and restrictions may linger into Sunday night before
dry weather and VFR conditions return for Monday and Tuesday.
&&
.CLIMATE...
Raleigh (KRDU)
Date Record High Max/year Record High Min/year
12/30 76 2019 63 2015
12/31 72 1929 59 1923
01/01 75 1985 55 1979
01/02 79 1952 56 1966
Greensboro (KGSO)
Date Record High Max/year Record High Min/year
12/30 76 1984 52 1974
12/31 71 1923 52 1936
01/01 75 1985 54 1966
01/02 76 1952 58 1966
Fayetteville (KFAY)
Date Record High Max/year Record High Min/year
12/30 76 1984 66 2015
12/31 79 1984 60 1923
01/01 77 1974 59 2019
01/02 78 1916 56 1985
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Smith
NEAR TERM...Smith
SHORT TERM...Green
LONG TERM...CA
AVIATION...Smith/Green
CLIMATE...Blaes
Area Forecast Discussion
National Weather Service Blacksburg VA
1040 PM EST Thu Dec 30 2021
.SYNOPSIS...
Abnormally warm conditions will stick around through New Year`s
Day, before transitioning to something colder. A strong storm
system will cross the U.S. Friday and Saturday, resulting in
winter storm conditions from the Rockies to the Mid-West, with
showers and severe thunderstorms across the Mid-Mississippi and
Tennessee Valleys. The cold front associated with this storm
system will cross the Mid Atlantic Region Saturday night into
Sunday bringing rain, followed by much colder temperatures and
mountain snow showers Sunday night.
&&
.NEAR TERM /THROUGH FRIDAY/...
As of 1035 PM EST Thursday...
Dense fog advisory issued.
Have issued a dense fog advisory for places near a surface warm
front to our south, and that are already or will shortly see
visibilities at or below a quarter mile tonight into Friday
morning. This encompasses areas mainly east and south of the
Blue Ridge, however patchy fog is likely in the mountains as
well.
As of 955 PM EST Thursday...
Springlike warmth to close out 2021.
A surface front has stalled over North Carolina with outflow
boundary driven showers/tstms even farther south into AL/GA/SC.
Stratus and fog will continue to fill in overnight as the
nocturnal inversion develops. Despite cloud cover, it will
remain mild with temperatures remaining well above
freezing...lows generally in the 40s.
Have maintained a low probability of precipitation in northern
North Carolina ans extreme southern Virginia based on the last
few runs of the HRRR and RAP.
The stalled front to our south is expected to move back north
as a warm front Friday in response to increasing southwesterly
flow from a storm system emanating from the Rockies. Isentropic
lift along the front will result in considerable cloud cover,
but again, temperatures will remain well above the seasonal
normals in spite of the cloud cover. Can`t rule out a shower
Friday afternoon/evening, QPF less than a tenth.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 130 PM EST Thursday...
Very gusty winds and the S-word will be in the forecast for parts of
the area Sunday night.
During this portion of the forecast we are expecting a significant
change in the over synoptic pattern across our region and much of
CONUS in general. What has been a trough-ridge pattern over the
central to eastern part of the U.S. will change. The the trough/low
over the central U.S. is expected to deepen/amplify through Sunday
morning. Sunday morning through Sunday night, this is expected to
rapidly eject eastward, crossing our region.
What this will mean weather-wise for the area will be a
strengthening of the southwest warm/moist flow across our region. A
stalled baroclinic zone between the trough and ridge will move
eastward and be the focus for round of showers, some on the moderate
side, advancing into and through the region.
We will also see the potential Saturday afternoon and Sunday
afternoon for some isolated thunderstorms across southeast parts of
the area.
The main upper trough and surface cold front are expected to cross
the area Sunday night. With this crossing will come a sharp wind
shift to the northwest with gusts increasing notably through the
night. We may have to watch for some area near the crest of the Blue
Ridge nearing, or reaching, Wind Advisory levels. These strong winds
will usher in much colder air through the night, taking what has
been a well above normal series of days back to near reality for the
start of January. Most of the moisture associated with the front
will exit in advance of the arrival of this colder air. However,
enough moisture will continue through the night for a switch from
rain showers to snow showers across the mountains. Currently, minor
accumulations are expected where any snow accumulates. Surfaces are
going to remain above freezing a for a period of time after the air
temperatures reaches freeing given how mild we have been lately.
Confidence in the above forecast scenario is moderate.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 200 PM EST Thursday...
Drier and near normal temperatures return to the area.
High pressure will build into the region through the middle of the
week. This will bring dry weather and temperatures more in line with
normal conditions for this time of year.
On Thursday, the area starts getting on the west side of the
high/ridge. This change will start to bring southerly winds back
into the area, along with a trend towards slightly milder
temperatures. Our next potential weather system currently looks on
track to starting bringing some light precipitation back to the
region Wednesday night into Thursday in association with this return
of moisture ahead of the next trough. However, there are notable
differences between the deterministic models on the timing,
location, and amount of this precipitation. Our forecast will
reflect a consensus forecast on timing and location.
Confidence in the above weather scenario is moderate.
&&
.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
As of 655 PM EST Thursday...
Western edge of a large area of IFR stratus extended from just
west of KCHO to KROA to just east of KAVL this evening. These
ceilings will lower this evening and more stratus and fog will
fill in over the mountains before 06Z/1AM. A stationary front
was along the Virginia/North Carolina border. IFR to LIFR fog is
expected overnight in the foothills and piedmont.
The front will lift north through the area Friday with
potential for scattered showers along the front Friday afternoon
and evening, especially in the mountains. Little improvement in
ceilings expected during the morning in the Virginia and North
Carolina piedmont with visibility improving from any morning
fog. Once the warm front comes through, conditions will improve
to VFR. Bufkit forecast soundings showed ceilings over the
mountains will dissipate before noon/17Z but it will take longer
for KROA/KLYH and KDAN. Winds through are expected to be light
and variable until the front goes through then winds will be out
of the southwest at 5 to 10 knots.
Average confidence on low clouds and fog tonight, and the timing
of the warm front lifting north and improving conditions.
.Extended Aviation Discussion...
A strong storm system will move across the central U.S.
Saturday, then across the eastern U.S. Sunday. Best chance for
VFR in our local region will be Saturday, with high likelihood
of IFR/MVFR conditions Saturday night into Sunday as a strong
cold front crosses the region with showers and embedded
thunderstorms.
Behind the front expect rapidly falling temperatures with
mountain snow showers Sunday afternoon into Sunday night. Winds
ahead of the front will be out of the southwest Saturday. Some
gust wind is possible in the piedmont. Winds then shift to the
northwest Sunday with frequent gusts 25 to 35 kts areawide.
Flurries and MVFR cigs will linger across the mountains Monday,
otherwise expect clearing with widespread VFR by Tuesday. Winds
will also diminish Tuesday.
&&
.CLIMATE...
As of 200 PM EST Thursday...
Records for Thursday, Friday and Saturday...
Dec 30
Site MaxT Year MinT Year LoMax Year HiMin Year
Bluefield, WV 68 1990 -25 1917 4 1917 51 1990
Danville, VA 76 1984 -1 1917 16 1917 52 1990
Lynchburg, VA 71 1996 -4 1917 16 1917 50 1990
Roanoke, VA 70 1996 -12 1917 16 1917 50 2019
Blacksburg, VA 68 1984 -27 1917 11 1909 50 1984
Dec 31
Site MaxT Year MinT Year LoMax Year HiMin Year
Bluefield, WV 74 1951 -2 1917 14 2017 53 1972
Danville, VA 76 1984 7 1917 22 1917 51 1990
Lynchburg, VA 73 1992 5 1983 17 1917 47 1992
Roanoke, VA 72 1992 3 1917 17 1917 51 1992
Blacksburg, VA 65 1992 -8 1917 17 1917 46 1911
Jan 01
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
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Dense Fog Advisory until 10 AM EST Friday for VAZ014-017-
022>024-032>035-043>047-058-059.
NC...Dense Fog Advisory until 10 AM EST Friday for NCZ004-005.
WV...None.
&&
$$
SYNOPSIS...PM
NEAR TERM...AMS/PM/SH
SHORT TERM...RR
LONG TERM...RR
AVIATION...AMS/PM
CLIMATE...RCS
Area Forecast Discussion
National Weather Service Tulsa OK
834 PM CST Thu Dec 30 2021
...New SHORT TERM...
.SHORT TERM...
(The rest of tonight)
Issued at 734 PM CST Thu Dec 30 2021
The big picture view with WV sat imagery shows a deep upper low SW
off the coast of California that will eventually move inland late
tonight into tomorrow morning. Rounding the base of this upper low
is the subtropical jet which extends across much of the southern
half of the country including our region. The polar jet is evident
across the pacific NW and the northern plains. With a jet streak,
more or less over our region, clouds are developing though modest
moisture at the surface will continue to squash any chance for
precipitation through the night. By early tomorrow morning, a
pronounced 250mb jet streak will begin developing to our north
putting our region solidly into the right entrance jet region or
a zone for lift. This aspect will eventually lead to precipitation
chances tomorrow which is covered in more detail in the long term
section.
As for tonight, temperatures have recently dipped quite a bit
across NE OK thanks to some clearing that had developed and weak
winds promoting radiation cooling. A weak boundary separates the
cooler air from the more mild air. Skies will continue to be
scattered to mostly cloudy through the night with mid level cloud
cover increasing later tonight into early tomorrow morning.
The Oklahoma mesonet and observations across NW AR show a large
area of temperatures in the mid 50s across E OK into NW AR
generally south of I-44 with winds south of the aforementioned
weak boundary in the 8 to 15mph range from the south. Locations
north of I-44 are seeing temperatures largely in the 40s with
even some mid 30s. RAP soundings for the current time across
E-central OK into NW AR show a rather large inversion that extends
vertically a few hundred meters. With the aforementioned winds
ongoing, mixing is occurring allowing for temperatures to remain
mild across much of E OK and NW AR. This inversion also helps
explain why we will see temperatures stay relatively steady or a
slow decrease for areas currently south of the aforementioned
boundary while locations along and north of the slowly migrating
northward boundary will see temperatures slowly rise through much
of the night as winds increase behind the boundary. Tulsa is a
good example as it is currently located near the boundary.
Temperatures fell quickly into the 40s for the 7PM observation
thanks to light winds and mostly clear skies but a rise of 3
degrees occurred through 8PM with a temperature of 50 thanks to
an increase in wind being noted. Since the 8PM observation, the
temperature has fluctuated by as much as 4 degrees as a result of
winds going calm and then picking up again. In short, locations
near the boundary may see temperature swings by up to 5 degrees
(possibly more) in a very short amount of time between winds
going calm (allowing for rapid radiational cooling) and picking up
to 10mph or so (allowing for mixing of warmer air to the
surface). This, in turn, makes a tricky hour by hour forecast for
the overnight hours.
Temperatures and sky conditions were adjusted with this forecast
package to account for the current observed trends. An update will
be issued shortly.
Snider
&&
.LONG TERM...
(Tomorrow through Thursday)
Issued at 417 PM CST Thu Dec 30 2021
Main focus continues to be the Friday afternoon into Sunday
morning time frame as a strong low pressure system and strong cold
front are forecast to move through. Severe weather
potentials...ice and snow accumulations and dangerous wind chills
are all in play across parts of the CWA.
Breezy south to southwesterly flow is expected to continue Friday
which will allow for one more day of well above seasonal average
temperatures across Eastern Oklahoma and Northwest Arkansas before
the bottom falls out over the weekend. Increasing moisture is also
expected Friday into Friday night with dewpoints in the 50s to
near 60 deg setting up across Southeast Oklahoma into West Central
Arkansas. Rain showers and thunderstorm chances become possible
Friday afternoon and increase Friday night ahead of the strong
cold front progged to move into the CWA late Friday night/early
Saturday morning. The greater potential for thunder is forecast
mainly along and south of Interstate 40 Friday night where the
northern portion of the higher instability looks to be.
Instability combined with the higher surface dewpoints and a
30-40KT low level jet will allow for a few storms to become
strong to severe with damaging winds the primary threat and large
hail a secondary threat. Locally heavy rainfall is also possible
as precipitable water values around 1.5 inches lifts into
Southeast Oklahoma and Western Arkansas. 1 to 2 inches of rain and
locally higher are forecast through Friday night across these
locations.
By Saturday morning the greater thunder potential looks to be
pushing off to the southeast as the strong cold front enters into
the CWA. The cold front looks to be near/slightly north of
Interstate 44 around 12z and reaching into Southeast Oklahoma and
Northwest Arkansas late morning and early afternoon Saturday. At
the same time...the upper level trof axis is progged to be moving
out of the Desert Southwest and into the Southern Plains.
Thus...precip chances are forecast to continue through Saturday
morning and taper off mid/late Saturday afternoon as the surface
low and cold front exits.
Behind the cold front...a much colder airmass will quickly spread
into the CWA within gusty northerly flow. Aloft...the colder air
is forecast to be slightly delayed with southwesterly winds and
warmer conditions holding ahead of the mid level front. These
conditions will create the potential for freezing rain to develop
across parts of Northeast Oklahoma Saturday morning and possibly
transition to light sleet by late morning as the colder air aloft
makes its way into the CWA. The greater potential for ice and
sleet looks to be mainly north of Interstate 44 with some ice
accumulations possible. At this time...there could be a band of a
tenth to two tenths of an inch of ice possible near the Kansas
border before the precip tapers off Saturday afternoon. Gusty
northerly winds of 20-30mph could create impacts of some power
outages within the ice accumulation areas. By Saturday
afternoon...majority of the precip looks to be lifting to the
northeast with slight chances of light freezing drizzle/sleet
remaining across the far northeast corner of Oklahoma into far
Northwest Arkansas. A glaze of ice may be possible for these
locations Saturday afternoon. South of these locations...rain
showers are expected across the rest of Eastern Oklahoma and
Northwest Arkansas into Saturday afternoon. Continue to monitor
latest updates as wintry precip/types/amounts/locations continue
to be refined.
Saturday night into Sunday morning...the cold airmass continues
to filter into the CWA along with breezy to gusty northerly winds
as the upper level trof axis finally makes it into the region.
These conditions will aid in low temps early Sunday morning in the
teens for most locations with the normal cold locations near the
Kansas border in the upper single digits. In response...wind chill
values of around 5 below zero to 5 above zero are forecast across
much of the CWA. As the upper level trof axis moves into the
region and interacts with mid level frontogenetic forcing
remaining over the region...some light snow could be possible
across Northeast Oklahoma into Northwest Arkansas Saturday night.
A narrow band of up around 1 inch or so may be possible and this
will continue to be monitored with latest data. The upper level
trof axis should exit during the day Sunday with clearing skies
Sunday afternoon.
The much colder conditions look to be replace with a warming trend
for the first half of next week as breezy to gusty southerly winds
return. Temps by Tuesday/Wednesday look to be back closer/slightly
above the seasonal average again. There continues to be
indications with latest model solutions of another wave pushing
through the CWA around the middle part of next week with colder
conditions again. Moisture looks to be limited and will continue
to keep the passage of this system dry at this time.
&&
.AVIATION...
(00Z TAFS)
Issued at 519 PM CST Thu Dec 30 2021
VFR conditions expected to prevail with mostly passing mid/high
clouds. Still a small chance of stratus development in the higher
terrain areas late tonight into Friday morning, but chances too
low to mention. Have inserted a PROB30 for late day showers.
&&
.PRELIMINARY POINT TEMPS/POPS...
TUL 47 69 45 50 / 0 30 90 80
FSM 49 71 59 67 / 0 40 100 90
MLC 52 68 57 64 / 0 40 90 80
BVO 38 66 35 41 / 0 20 80 80
FYV 46 68 56 59 / 0 40 100 90
BYV 49 69 54 60 / 0 30 90 90
MKO 47 67 55 59 / 0 40 90 80
MIO 43 66 39 46 / 0 20 90 90
F10 49 67 55 58 / 0 40 90 80
HHW 55 71 60 68 / 0 40 90 80
&&
.TSA WATCHES/WARNINGS/ADVISORIES...
OK...None.
AR...None.
&&
$$
SHORT TERM...21
LONG TERM....20
AVIATION...18