Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 12/23/22
Area Forecast Discussion
National Weather Service Indianapolis IN
1021 PM EST Thu Dec 22 2022
.Mesoscale Update...
Issued at 1021 PM EST Thu Dec 22 2022
****SIGNIFICANT WINTER STORM UNDERWAY****
Quick update to the mesoscale update from earlier in the evening...
becoming increasingly apparent that the heaviest swath of snow will
be further east than we anticipated...likely aligning more across
far eastern Indiana and western Ohio. It is possible that the
steadier snowfall may pivot back to the west slightly over the next
few hours as the surface low deepens over NW Ohio and SE Michigan.
But it would appear that snowfall totals will end up being closer to
the lower end of the forecast range over much of the area and we
have scaled back amounts accordingly.
The winds and bitterly cold temperatures remain the primary
threats. At 03Z...temperatures had slipped into the single digits
and lower over most if not all of the forecast area. Across western
counties...several locations have already fallen to subzero levels
with wind chills now at -20 or lower. The winds have been routinely
gusting at 30-40mph through the evening but expect an uptick into
the overnight as the low deepens and the pressure gradient tightens.
Have seen a few sites in Illinois with gusts peaking above 45mph.
This will maintain blowing snow and areas of reduced visibilities
throughout the night and into Friday. Travel remains challenging.
Early evening mesoscale update follows. Stay safe.
Issued at 731 PM EST Thu Dec 22 2022
As of 00Z...the arctic front has cleared almost the entire forecast
area with perhaps the exception of parts of Randolph County.
Conditions have steadily deteriorated over the last 2-4 hours from
west to east as temperatures have tumbled...winds have strengthened
substantially and moderate to at times heavy snow continues. At
00Z...temps ranged from near zero in the Wabash Valley to the mid
30s in our far eastern counties. The temp falls have been
exceptionally impressive...on the order of 20 degrees or more over
about a 90 min period.
Elongated surface wave over western Ohio beginning the deepening
process that will finish over eastern Ontario in the 960-965mb by
Friday evening. Snowfall rates have been largely manageable up to
this point but expect further intensification of snow rate and flake
size over the next few hours especially focused across the eastern
half of the forecast area as the dendritic growth zone deepens and
lowers with the influx of much colder air into the region. This will
also have the impact of increasing snow ratios perhaps as high as 25
to 1 by late evening. Even though there are some recent model hints
at lower snow totals over the western half of the forecast area than
previously thought...not going to make any changes to snowfall
amounts at this time. And still expect the potential for some spots
to cash in over far northern counties as the pivoting process to the
bombing out low pressure occurs overnight. Snow will linger longer
over the northeast half of the forecast area with the potential for
a few locations to approach 5-6 inches before it is all said and
done.
But as we have messaged for the last few days...the snowfall
totals are the secondary issue. The primary concerns remain the
bitterly cold temperatures continuing to advect into the region and
the strong NW winds which will only increase as the low strengthens
overnight. Icy conditions are present across the region courtesy of
the rapid temperature drop experienced this evening. And now the
wind and snow are adding to the travel problems with blowing snow
across roads and other exterior surfaces. These conditions will only
worsen further over the next few hours with the increase in snow
rate and wind speeds.
Temperatures will likely be near or below zero over the entire
forecast area near or shortly after midnight with wind chills of -35
to -20. An interesting historical note: should we get to 0 or lower
by midnight here at Indy...there would be high potential for
breaking the lowest max temp record for December 23 which is 1
degree as we think temperatures will struggle to get back above
zero on Friday. That occurred during the brutally cold late December
of 1983.
Stay safe and stay warm.
&&
.Short Term...(This evening through Friday)
Issued at 247 PM EST Thu Dec 22 2022
=====================================================================
SIGNIFICANT WINTER STORM EXPECTED THURSDAY AFTERNOON - FRIDAY
=====================================================================
Key Points:
* Very dangerous cold and associated societal impacts, including
rapid development of frostbite and hypothermia is the primary
message.
* Rapid drop in temperatures and rapid freezing of wet road surfaces
4-8pm time frame.
* Near Blizzard-like conditions at times due to heavy snow rates and
winds gusting upwards of 60 mph at times this evening, especially
along and north of I-70 corridor.
* Blowing snow and additional snow showers Friday will create
dangerous traveling conditions.
Forecast Changes:
* Snow amounts across the region remain between 2 and 5 inches.
Isolated areas across the north potentially could get a little
more.
* Increased snow shower chances for Friday into Friday night to
include "scattered snow shower" wording in the forecast.
Current Observations:
Current satellite and surface observations indicate the arctic front
is right along the IL/IN border as of 2 PM EST. Surface low is just
now beginning to develop ahead of the front in an area just south of
I-70 between Bloomington, Sullivan and Terre Haute as surface
observations are showing this is the area with the lowest pressure
dropping about 1-2 mb per hour. Observations from that area show
pressure already down to 1007 mb at KBMG and KIND as of 2 PM EST,
which is right where pressure should be at this point in time. Will
have to watch how fast pressure falls this evening as the potential
is there for the low to rapidly strengthen faster than what guidance
shows.
Observations behind the front show a rapid drop in temperatures into
the single digits within a few hours. As the surface low pressure
continues to strengthen and push northeast, expect the temperature
gradient to tighten even further with temperatures potentially
falling over 20 degrees within an hour as the front passes through.
Currently, not seeing many observation sites across Illinois with
vis less than a mile, but expect visibility to rapidly deteriorate
as the low strengthens and winds and snowfall rates increase behind
the front. Blizzard-like conditions still possible later tonight
behind the front for a few hour period, mainly between 21z and 03z
for Central Indiana. This is a rapidly evolving situation and
conditions are expected to deteriorate rapidly as the front moves
through.
Meteorological Analysis:
Intense mid-latitude system has dislodged an anomalous Arctic air
mass to our northwest, with its forward surge commensurate with
impressively strong PV forcing. The nature of this type of
intensifying mid-latitude system at this life stage will be for
strong vertically developed frontogenetic circulation, enhanced by
strong ageostrophic response to impressive upper level jet dynamics.
The preceding warm sector response is resulting in low-level
moisture advection and ascent (most pronounced on the 285-K
isentropic surface) this afternoon. This has allowed for drizzle and
rain showers to persist today across Indiana ahead of the front.
Latest IND ACARS sounding still shows a dry layer between 700mb and
500mb that still needs to saturate; however enough of a saturated
layer has developed below it for showers to pick up in intensity
this afternoon.
The heavier precipitation should occur within a band immediately
ahead of the tropopause fold and cold front, and associated deeper
ageostrophic vertical circulation. Frontogenesis slope is steep so
the opportunity for a thermal profile that would cause a mix of
precipitation at transition is quite limited, and alternate
precipitation types (i.e., sleet and freezing rain) are negligible
and not mentioned in this forecast. Instead, we have a clean
transition from rain to snow. It is worth noting that if the pre-
frontal thermodynamic environment were colder and supportive of
snow, a robust and dangerous snow squall scenario would be possible.
However, it appears that these heavier rates will be right at
transition with snow occurring primarily behind this
frontogenetically-enhanced band within broader anafrontal
precipitation shield. Timing of the aforementioned band at onset of
very strong cold advection is covered in supplemental decision
support graphics and is roughly from 3pm to 8pm west-to-east across
the area.
It is very important to note that precipitation is expected to be
ongoing at the time of this rapid temperature drop and this is
supported by MRMS subfreezing road temperature modeling
probabilities to our west in the Plains where the cold front current
is. Confidence is very high that rapid freezing of wet road surfaces
will occur, in what we`re essentially messaging to be a "flash
freeze" situation. It may be difficult for road treatment crews with
even the best equipment to keep up at least initially, and a period
of particularly hazardous travel is likely. This will be followed by
accumulating snow atop potentially ice covered roads as we progress
through the evening.
Most of the snow accumulation will occur in the relatively narrow
anafrontal precipitation band within a 4-5-hour window of the
passage of the Arctic front. Snow-liquid ratio will transition
quickly west-east during this time period. At the onset of snow they
should be near climo at roughly 11:1, but will briefly increase to
around 16-17:1 as deep isothermal layer evolves within dendritic
growth temperature range. Though, this may be somewhat tempered by
strong surface winds fracturing dendrites. Regardless, this may only
last for a short time as further cooling will nudge our thermal
profiles to the cold side of the DGZ transitioning to predominately
plates and columns for ice crystal habit for the last couple of
hours of the snowfall that is generated by deep synoptic-scale lift.
The result is 2 to 5 inches of storm total snow across the area.
Dry conveyer belt pushing in behind the front along with sinking air
as seen on the 280 K isentropic surface map, briefly shutting off
heavy snowfall from around 06z Friday through around 15z. As the
surface low continued to "bomb out" (rapidly intensify at a rate of
at least 1 mb per hour), the TROWAL should wrap around the back side
of the low and push in from the north, evident on the GFS 280k
Isentropic surface forecast map. While the best lift aloft remains
to the north, there should be weak isentropic lift pushing into
Central Indiana from the north midday Friday. At the same time,
frontogenetical forcing within the shallow saturated layer near the
surface should help aid in the production of snow showers. While
winds will still be gusting upwards of 55+ mph through the state,
blowing snow and additional snow showers will likely cause whiteout
conditions at times. Any accumulations will be minor, since most
snow will not stick and just blow and drift. Main impact from snow
showers Friday will be hazardous travel conditions and very low
visibility.
Wind, Temperature, and Wind Chill Impacts:
Very tight pressure gradient and very strong low level jet aloft
associated with the rapidly intensifying low will keep high winds
across Central Indiana through Friday night. Would not be surprised
to see isolated gusts over 60 mph on Friday as the low level jet
right at the top of the inversion continues to strengthen and mix
down to the surface. Significant arctic air advecting into the area
will create dangerous conditions with temperatures falling as low as
-10F Friday morning and struggling to rise above zero Friday
afternoon. These temperatures combined with high winds will create
dangerous wind chills down to -35F which can cause frost bite in as
little as 10 to 15 minutes on exposed skin. The impacts from wind
and dangerous cold will likely be more impactful than the impacts
from the snow. While snow will cause near blizzard conditions at
times and will likely cause significant travel impacts, the
dangerous cold could potentially be life threatening, especially to
vulnerable populations with inadequate supplies to stay safe.
&&
.Long Term...(Friday night through Thursday)
Issued at 303 PM EST Thu Dec 22 2022
* Dangerous wind chills as low as -25 to -10 thru Sunday morning
* Strong wind gusts as high as 30-40 mph Saturday
Saturday through Sunday...
The holiday weekend will exhibit a phase-two, or extension so to
speak of the intense winter storm...with anomalous cold and strong
wind gusts continuing to bring extreme low wind chills through AM
hours Saturday...and less-extreme, yet still dangerous wind chills
continuing through AM hours Sunday. Additional organized snowfall
is not expected...although flurries and a few snow showers are
possible north of I-70 during the day Saturday as aloft the system`s
tail of vorticity slides west to east near the region. The bigger
impact to both visibility and road conditions Saturday would likely
be from the existing snowpack to continue to contribute to blowing
snow. Negative differential vorticity advection should then cross
the Midwest around the late-Saturday timeframe which would promote
at least partial clearing and a slight decrease to winds as another
portion of the approaching very broad, amplified arctic surface
ridge builds into central Indiana. No precipitation is expected for
Christmas Day, while blowing snow concerns continue to decrease amid
winds finally gusting to only 20 mph or less, and perhaps a slight
crust forming on top of the snowpack from even more sunshine Sunday.
Nevertheless, temperatures will be dangerously low from near zero
both Saturday and Sunday mornings, with afternoons only rebounding
to 10-15F for most locations. Wind chill values will continue to be
dangerously low, ranging from around -20F early Saturday to
hopefully near zero by late day CHristmas Day.
Monday through Thursday...
While still 15-20 degrees below normal, the Monday timeframe should
display the first noticeable moderation in temperatures...as winds
finally drop to around/under 10 mph while backing to a more
southerly direction...amid the center of high pressure passing from
near the Ozarks towards the Tennessee Valley. The upper levels will
also attempt to rearrange with a more progressive western US ridge
advancing eastward towards the lingering/filling trough over eastern
Canada...with a moisture-starved and rather weak short wave expected
to plunge southward between these broader features through the
Middle Mississippi Valley. Can`t rule out a few snow showers around
Monday as this weak disturbance crosses to the Ohio Valley, yet so
far low confidence in any impacts.
Despite its southern track around the filling trough`s periphery,
the weak disturbance will act as a quasi-kicker to at least wobble
the eastern-Canadian trough`s influence northward and finally out of
the region...with a more zonal pattern resuming as the arriving
upper ridge flattens over much of the CONUS. The once-extreme
arctic surface high should then continue to slide east to near the
Atlantic coast and at least promote southerly return flow, even if
the degree of moderation from this flow may be more dependent on the
intensity of the next cyclone...near the northern Plains by the mid-
week. This should all translate to a continuing moderation amid
light to moderate southerly flow...with temperatures expected to
rise above 32F around the Wednesday timeframe...if not even reach
slightly above normal levels by the end of the long term.
The normal max/min at Indianapolis through the long term is 38/24.
&&
.Aviation...(00Z TAF Issuance)
Issued at 620 PM EST Thu Dec 22 2022
Impacts:
===================================================================
WINTER STORM TO CAUSE SIGNIFICANT AVIATION IMPACTS THIS EVENING INTO
FRIDAY
===================================================================
* Widespread IFR and lower conditions in snow through the evening
* W/NW winds gusting as high as 45kts at times through Friday
* Blowing snow through Friday
Discussion:
Significant impacts have developed from the Winter Storm as the cold
front is now east of all of the terminals. Expect further
deterioration of conditions for aviators through the evening then
continuing all day Friday.
Snow is now falling at all terminals with wind gusts at 30 to 40
kts. Expect an uptick in winds through the overnight to as high as
35 to 50 kts on Friday as low pressure to the northeast rapidly
intensifies. Near blizzard conditions remain possible at times with
heavy and blowing snow and low visibility through the evening until
about 06Z. While the heaviest snow ends overnight...blowing snow
will continue all day Friday with the strong winds persisting.
Expect additional snow showers to develop Friday afternoon and
evening with the potential for white out conditions at times and
lower ceilings...especially along and north of I-70 corridor.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 7 PM EST Friday for INZ021-028>031-
035>049-051>057.
Winter Storm Warning until 1 PM EST Friday for INZ060>065-
067>072.
&&
$$
Mesoscale...Ryan
Short Term...CM/BRB
Long Term...AGM
Aviation...Ryan
Area Forecast Discussion
National Weather Service Raleigh NC
910 PM EST Thu Dec 22 2022
.SYNOPSIS...
Low pressure will lift northward over the Mid Atlantic coast this
evening. An unusually strong Arctic cold front will cross the region
late tonight through Friday morning, allowing strong winds and
frigid temperatures to overtake the area. Much below normal
temperatures will hold through early next week within cold high
pressure.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 910 PM Thursday...
The surface low that moved northeast across our eastern counties
earlier today is now weakening as it moves into eastern Virginia.
Meanwhile, the primary surface low continues its march northeast,
currently located near Detroit with the cold front stretching to the
east of the Mississippi River.
Temperatures should be rather steady overnight until the arrival of
the arctic cold front. This means that most locations east of US-1
shouldn`t have much change in temperature overnight or possibly rise
a degree or two. West of US-1, especially in the Triad, temperatures
should be steady until 4-7am and then temperatures will drop off.
Today`s precipitation has exited to the east, but another round of
precipitation is possible with the arrival of the front after
midnight. Likely pops are primarily contained to Forsyth and
Guilford Counties, but almost all locations will have at least a
slight chance of precipitation through sunrise. Precipitation will
fall mostly as rain, but a few wet snowflakes cannot be ruled out as
precipitation ends. Snow accumulation is not expected. In addition,
a flash freeze could occur across the western Piedmont late tonight
into early Friday morning from the rain that occurred earlier today.
&&
.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
As of 130 PM Thursday...
...Wind Chill Advisory has been issued for Friday night into
Saturday morning for all of central NC...
...Wind Advisory has been issued for Friday across all of central
NC...
The strong mid-level trough over the Ohio Valley and Mid-Atlantic
region will track into Canada by early Sat. The well advertised
Arctic front will plow through central NC Fri morning, moving off
the coast in the afternoon/evening, as a strong surface low occludes
over the Great Lakes. Along with temperatures crashing into the
middle teens in the western Piedmont to the 20s/30s in the
afternoon, strong wind gusts with the Arctic frontal passage may
briefly reach 45-50 mph. Thereafter, winds will remain gusty between
30-40 mph owing to the strong CAA and tight pressure gradient. As a
result, have issued a Wind Advisory for all of central NC into early
Fri evening.
The winds will remain sustained in the 10-15 mph range with gusts
between 20-25 mph Fri night into early Sat. This, combined with
temperatures falling into the single digits to lower teens by early
Sat , will result in very cold wind chills as low as 10 below zero,
lowest in the Triad region. The latest MAV/MET/ECM show single
digits in the Triad and lower teens in the Sandhills to eastern
Piedmont. Although the continued mixing is expected with these
winds, which should prevent optimal radiational cooling, the
anomalous airmass makes these statistical guidance numbers quite
believable. To that end, we expanded the Wind Chill Advisory for all
of central NC (Fri evening to Sat morning) to also highlight the
potential for these very cold wind chills.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
As of 255 PM Thursday...
Long term pattern supports cold and dry conditions with some
moderation of temperatures late in the period.
A longwave trough will be in place across eastern North America to
start the long term period on Saturday morning. The relatively
uniform and broad cyclonic circulation across the eastern CONUS
becomes noisier with time as multiple short wave troughs drop into
the back side of the long wave trough. These features first appear
late Saturday and are moisture starved but with time they will be
accompanied by some high and mid level moisture. Will maintain a dry
forecast but will note intermittent periods of mid and high clouds.
Will need to monitor these features as subtle adjustments to track
and phasing with the southern stream could result in a chance of
precipitation. After the most significant trough passes on Tuesday,
heights begin to rise and the airmass moderates with a westerly flow
aloft.
Temperatures will be well below average over the weekend with highs
in the upper 20s to mid 30s on Saturday, the lower to mid 30s on
Sunday and the 30s to near 40 on Monday. Highs in the 40s on Tuesday
and Wednesday will moderate int the 50s on Thursday. -Blaes
&&
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
As of 735 PM Thursday...
Adverse aviation conditions of one form or another will continue
through tonight and Fri. Patchy light rain and drizzle with MVFR-IFR
vsbys and IFR-LIFR cigs and light mainly SW surface winds will
continue over central NC into the early overnight hours ahead of an
approaching Arctic cold front. The expected timing of this frontal
passage will be 09z-12z at INT/GSO, 11z-13z at RDU, and 12z-15z at
RWI/FAY. This is no typical cold front passage: As winds shift
around to be from the W and WNW, sustained winds of 20-30 kts are
likely during this time window, with gusts of 35-50 kts as very
frigid air rushes in with intense falling temps and humidity.
Surface winds will remain strong through Fri, with frequent gusts of
30-45 kts. Winds aloft will be strong as well and could cause
difficulties in aircraft handling, particularly small aircraft, with
a significant crosswind. In addition, a narrow/short-lived band of
rain, mixed with or briefly becoming snow, is expected as the front
moves through. If there is some good news, it`s that VFR conditions
are expected starting just behind the front from mid morning Fri
onward, with few clouds behind the front as Arctic air builds in.
Surface winds from the WNW or NW will start to decrease very late in
the period, after 22z, but will remain strong and gusty.
Looking beyond 00z Sat, winds will continue a gradual decrease
through the night but remain elevated through Fri night and Sat,
sustained 10-15 kts with gusts up to 20-25 kts. VFR conditions will
dominate Fri night through Tue, with just some mid level cloudiness
Mon night associated with a passing disturbance aloft. -GIH
&&
.CLIMATE...
Here are the temperature records for the next couple of days and the
years they were last set:
12/24 12/24 12/25 12/25
record low record low max record low record low max
GSO 4 (1983) 28 (1943) 1 (1983) 18 (1983)
RDU 6 (1983) 29 (1943) 4 (1983) 19 (1983)
FAY 14 (1989) 20 (1989) 4 (1989) 31 (1989)
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 4 AM to 6 PM EST Friday for NCZ007>011-021>028-
038>043-073>078-083>086-088-089.
Wind Chill Advisory from 7 PM Friday to 9 AM EST Saturday for
NCZ007>011-021>028-038>043-073>078-083>086-088-089.
&&
$$
SYNOPSIS...Hartfield
NEAR TERM...Green
SHORT TERM...Kren
LONG TERM...Blaes
AVIATION...Hartfield
CLIMATE...RAH