Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/19/22
Area Forecast Discussion
National Weather Service Cleveland OH
1005 PM EST Sun Dec 18 2022
.SYNOPSIS...
High pressure will gradually build into the region tonight and
Monday. A weak cold front pushes through Wednesday. An expansive
and impactful low pressure system will organize over the lower
Mississippi Valley in conjunction with a deepening upper level
trough that will ultimately bring Arctic air, strong winds, and
snow to the region after Thursday through Saturday.
&&
.NEAR TERM /THROUGH MONDAY NIGHT/...
Late Evening Update:
Cold and quiet across most of the area this evening. Lake effect
snow has lifted north of Erie County this evening...as a subtle
shortwave goes by over the next few hours, a bit of re-
invigoration along with a push back onshore is expected, with
some potential for very light snow to get into Lake and northern
Ashtabula Counties overnight into early Monday as well.
Freshened snowbelt QPF and POPs with a heavy lean on the hi-res
NAM, RGEM, HRRR and RAP models as they`re capturing current
placement of the snow best. Enough juice left for any bands to
produce some accumulating snow where they take shape overnight,
but not expecting anything heavy. Light lake effect will linger
into Monday in Erie County and perhaps along I-90 in extreme
northeast Ohio before completely tapering by Monday evening as
surface ridging moves right overhead. New accumulations of an
inch to locally two may occur through Monday morning in parts of
northeastern Erie County, with amounts elsewhere in northern
portions of the snowbelt under an inch if any manages to
accumulate. Reluctantly continued the LES Warning for Erie
County PA until 4 AM Monday with this update as potential does
exist for one last push of accumulating snow in parts of the
County overnight tonight on top of the locally several inches
that fell today, though any additional impacts (including to the
Monday AM commute) should admittedly be on the minor side.
Previous Discussion:
The lake effect remains reluctant to move further onshore due
to 250-260 wind directions that are more aligned with the Lake
Erie shore line, and there has been a large discrepancy in the
snowfall totals between Erie PA under an inch of snow and North
East PA. Probably going to come in under criteria but will leave
headlines in place with the 00Z-06Z Monday POPs pushing inland
a bit with winds turning more westerly and more snow still to
come. High pressure will push in from the lower Ohio Valley
Monday, and will gradually end the snow in the lake effect
zones. Meanwhile, the southwestern portion of the CWA will get
into some breaks in the clouds Monday, but temperatures area
wide will still have trouble getting above freezing. Will cloud
back up quickly into Monday night with mid/upper level moisture
from a weak warm front passing south to north just west of the
CWA. Largely dry Monday night with the lake effect pretty much
finished at that point.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Quiet weather will preclude the much talked about late week storm as
surface high pressure centered over the Ohio Valley Tuesday morning
moves east by the afternoon allowing a fast moving mid/upper
shortwave trough to brush across the northern Great Lakes. This wave
will be deamplifying, so its associated weak surface low will pass
well north of our region tracking from Lake Superior Tuesday
afternoon to east of James Bay by Wednesday. Since the energy and
forcing is passing well north and moisture return is minimal, expect
the trailing cold front to come through dry Tuesday evening and
Tuesday night. H85 temps dip to -6 to -8 C late Tuesday night and
Wednesday over Lake Erie in the weak post frontal cold advection as
we will be on the southern fringe of a large pool of arctic air
building into the northern Plains and northern Great Lakes, but the
airmass will be too dry for any lake-effect snow. Surface high
pressure returns Wednesday afternoon and quickly exits into New
England Wednesday night allowing mid/upper ridging to build over the
eastern CONUS ahead of a large, dynamic mid/upper trough diving into
the Plains. This will be the makings of the late week storm that I
know you want to read about, so more on that below.
So to some up the mid week period, dry conditions are expected
Tuesday through Wednesday followed by chances for light snow showers
increasing from south to north late Wednesday night as warm/moist
advection and isentropic ascent develop ahead of the deepening
trough to the west. Milder highs Tuesday in the upper 30s will cool
a degree or two Wednesday into the mid/upper 30s. Lows both Tuesday
and Wednesday nights will be generally in the mid 20s, so quite
seasonable for mid week.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
All eyes remain on the intense storm system expected to impact the
entire Ohio Valley and Great Lakes regions Thursday into the start
of the holiday weekend. The main messages, as well as the most
certain aspects of this event, continue to be rapidly falling
temperatures late Thursday night through Friday leading to rain
changing to snow and a flash freeze, damaging winds, and extreme
cold, both in terms of actual air temperature and wind chill, that
will worsen through the day Friday and Friday night. What is more
uncertain is how much snow will fall once the rain changes to snow
on Friday with differences in model guidance giving ranges from a
few inches to over a foot. It is important to note that no matter
how much snow falls on Friday, the damaging winds with this system
(likely topping 60 mph given the rapidly intensifying low and
extreme cold advection), will blow the snow into drifts and easily
create white out conditions. It would only take a few hours of
falling snow to realize true blizzard conditions with that wind and
the rapidly falling temperatures. When you combine that with
dangerous wind chill values worsening as the day wears on, this will
be a very dangerous storm no matter what. Those with travel plans on
Friday should be flexible and stay tuned to the latest updates. We
will transition to lake-effect snow behind the system as it lifts
north through Ontario Friday night and Saturday, lingering through
Sunday, but uncertainty with wind direction (west vs southwest)
makes it impossible to pinpoint if the bands will impact NE Ohio and
NW PA or if they will stay in western NY. What is certain is that
bitter cold temperatures and dangerous wind chills will continue
through the weekend with highs in the teens Saturday and Sunday and
lows well into the single digits both nights. Wind chill values
may get as low as -15 to -20 early in the weekend.
Now for a little more on the evolution of the storm, today`s 12Z
model runs have actually reverted back to being out of sync with
each other. This is unfortunate because it makes the timing of the
rain/snow changeover and the amount of snow we will receive highly
uncertain; even more uncertain than 24 hours ago. The big mid/upper
trough and associated pool of arctic air, originating in Siberia,
digs into the Plains Thursday. As it does, a 160+ knot H3 jet diving
into the base of the trough will cause it to tilt strongly negative
while cascading into the Midwest Thursday night while will lead to a
rapidly deepening surface low somewhere in the vicinity of Indiana
or western Ohio. Because the trough axis deepens all the way to the
Gulf coast, it will also scoop up additional southern stream energy
late Thursday. This will further aid in the deepening process
allowing the northern and southern streams to phase over the western
Ohio Valley and Great Lakes. This will result in a rare "bombing
out" of the surface low to take place right over our area as the
mid/upper trough closes off, with the whole system then pinwheeling
north through the central Great Lakes Friday and Friday night.
It is the bombing out that has us so concerned about damaging winds
once the arctic front plows through the area. Most guidance has the
low at least reaching the sub 975 mb range as it lifts just north of
our region, so this very tight pressure gradient combined the jet
energy and intense cold air advection will easily support 60+ mph
wind gusts. This will down trees and power lines and result in
widespread power outages, which is a worst case scenario given the
extreme cold.
In terms of the snow, today`s 12Z guidance is making this even more
uncertain due to timing and track differences. The new GFS came in a
solid 6 hours slower and now phases the system over the Ohio
Valley/lower lakes Friday afternoon. This would delay the rain to
snow changeover to almost midday Friday, with the heaviest snow
potentially not falling until Friday evening. The ECMWF maintains a
late Thursday night phasing and keeps the changeover to snow
consistent with the Friday morning timing, but it tracks the low
across west Michigan which would bring a dry slot into the area
after an initial burst of snow, with heavier snow from the trowel not
arriving until later in the day. The RGEM is in the middle with
timing, but it tracks the low toward the eastern Great Lakes as it
bombs out through the day Friday. This solution would give us the
most snow but may lessen the winds slightly. Any of these solutions
will lead to snow, high winds, and brutal cold developing Friday
into Friday night, but the amount of snow that actually falls is the
biggest question mark.
To summarize, warm air advection ahead of the deepening trough
Thursday will warm temps into the upper 30s, so precipitation driven
by broad warm/moist advection and isentropic ascent will fall as a
rain/snow mix, with rain being the dominant p-type Thursday. Rain
will rapidly change to snow late Thursday night or Friday morning,
depending on timing of the arctic front, with a burst of snow and
flash freeze likely. Winds will steadily increase Thursday night
from the SE and become damaging by Friday morning as they veer to
the W to SW in the cold advection behind the front. Snow will fill
back in at some point Friday morning or afternoon after a lull
behind the initial burst, with blizzard conditions possible through
the day and extensive blowing/drifting, even though exact snow
amounts are in question. Temperatures will fall through the teens
Friday afternoon and will continue to fall through the single digits
Friday night with dangerous wind chill values. The synoptic snow
will transition to pure lake-effect Friday night through Sunday east
of Cleveland, but to what extent the main band gets into our region
remains unclear. It is possible that a SW component to the wind
keeps it mainly over western NY most of the weekend, but lingering
wind and arctic cold will keep conditions hazardous.
&&
.AVIATION /00Z Monday THROUGH Friday/...
An MVFR stratus deck remains across much of the area as moist
low-level cyclonic flow continues across the Great Lakes. High
pressure wedging in from the Ohio Valley is trying to bring
some clearing towards Mansfield from the southwest and they may
scatter out the clouds this evening before re-filling in
overnight as a subtle shortwave goes by. Elsewhere, expect the
stratus to persist tonight, with cigs probably lowering a bit
across the board due to some amount of nocturnal cooling. Expect
the MVFR stratus to persist Monday with a gradual scattering
out from the west/southwest late in the day. The general rule
this time of year is to not expect the stratus to lift/scatter
out quicker than expected, so leaned somewhat pessimistic in
terms of bringing cigs back to VFR.
Lake effect snow has lifted just northeast of ERI this evening,
but should sag back in later this evening as winds turn slightly
more onshore. Generally not expecting heavy snow, but periods of
MVFR and somewhat more intermittent IFR are likely late this
evening through early Monday. Activity gradually weakens on
Monday, but not expecting cigs to lift to IFR through the end of
the TAF period even as vsby improves.
Modest west-southwest winds continue through the TAF period, a
bit stronger at CLE and especially ERI through Monday.
Outlook...Non-VFR possible in minor lake effect Tuesday night.
Non-VFR and strong winds expected the end of the week with
impactful and expansive low pressure system.
&&
.MARINE...
Water levels on the western basin fell close to the critical mark of
6 inches above low water datum this afternoon, but those are
starting to come back up now. This should continue through tonight
as the winds gradually lessen. W winds will decrease to 15-20 knots
tonight with waves subsiding to 5-7 feet on the central and eastern
basins. This will give way to lighter 5-10 knot winds by Monday
afternoon and waves falling under 3 feet as high pressure builds in.
Quiet conditions will then continue on the lake through Wednesday
night due to weak pressure gradients.
By Thursday, a strong trough and developing low pressure system
approaching from the west will start to increase winds on the lake.
SE winds will increase to 15-20 knots Thursday afternoon becoming SW
late Thursday night and Friday and increasing to Gale force as the
low moves north and rapidly bombs out. The high winds will continue
through Friday and into Friday night. The low is strong enough that
storm force winds are not out of the question Friday. Waves will
easily top 10 feet in the central and eastern basins with freezing
spray as bitter cold arctic air filters across the region. This will
lead to water levels in the western basin likely falling well below
low water datum Friday and Friday night.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...Lake Effect Snow Warning until 4 AM EST Monday for PAZ001-002.
MARINE...Small Craft Advisory until 10 PM EST Monday for LEZ144>149.
&&
$$
SYNOPSIS...26
NEAR TERM...26/Sullivan
SHORT TERM...Garuckas
LONG TERM...Garuckas
AVIATION...Sullivan
MARINE...Garuckas
Area Forecast Discussion...UPDATED
National Weather Service Corpus Christi TX
940 PM CST Sun Dec 18 2022
...New UPDATE...
.UPDATE...
Issued at 929 PM CST Sun Dec 18 2022
Coastal trough is sharpening along the lower and middle Texas
coast this evening. Southeasterly low level flow will continue
to advect higher moisture into the coastal region tonight with
shower activity expected to increase during the overnight hours.
Models depict enough elevated instability will develop toward
daybreak for isolated thunderstorms to occur westward into the
eastern Brush Country for Monday morning. Latest HRRR shows
MUCAPE values up to 500 J/kg in the morning in this region.
Added slight chance for thunderstorms to the forecast to
the east of a Hebbronville to Tilden line.
Also, some concern for stronger storms over the marine areas
Monday morning as more unstable air mass will move into the
coastal waters ahead of the surface low. HRRR shows MLCAPE values
from 1000-1500 J/kg with 0-6 km shear around 50 knots. Could see
some strong storms over the coastal waters with the potential for
rotation with the stronger low level helicity to the east of the
surface low. Adjusted marine forecast to show chance for storms
during the morning hours. No changes were made to the current
SCA configuration.
&&
.SHORT TERM...
(Tonight through Monday night)
Issued at 343 PM CST Sun Dec 18 2022
Concur with the GFS/ECMWF that an upper level trough will move
across the TX Panhandle/southern Plains tonight/Monday, while
another upper system moves across the CWA Monday, both at 500mb.
Also the CWA is predicted to be under the RRQ of a 250mb jet
streak early Monday. Most recent MSAS depict a weak surface trough
near the southern coast. The deterministic runs continue to
predict this trough to continue to develop, with the GFS
developing it into a closed low adjacent to the coast, while the
ECMWF retains the trough and slightly east. Nevertheless, expect
upper/surface forcing, increasing moisture to result in mainly scattered
to numerous showers tonight through early Monday over the Coastal
Plains. Although the predicted thermodynamic soundings preclude
surface-based CAPE, will add isolated thunderstorms near the
coast/offshore, given that conditions in the vicinity of the
surface low may be conducive to thunderstorm activity. Expect
precipitation to dissipate from west to east Monday afternoon, as
the upper/surface systems move east. Yet, concur with the NAM
which maintains overcast conditions through Monday afternoon,
which should maintain cool conditions. Decided to lower maximum
temperatures Monday below the NBM. Will retain the high risk of
rip currents tonight. Will not extend the high risk beyond the
current 12z Monday expiration, since the transition, beginning
after 12z Monday, in the winds in response to the foregoing
eastward moving surface low, which will decrease the rip current
risk.
&&
.LONG TERM...
(Tuesday through next Saturday)
Issued at 343 PM CST Sun Dec 18 2022
Key Messages:
-Strong arctic cold front Thursday
-Well below freezing temperatures likely Thursday night and Friday night.
-Single digit wind chills Friday morning?
Between Tuesday and Wednesday there`s not a whole lot to talk about.
Northerly surface flow will keep temperatures near or slightly below
normal with a fair amount of clouds, especially in the east. A mid
level shortwave pushes through on Tuesday, but doesn`t have enough
moisture to work with for any notable rain chances.
The more interesting part of the forecast starts on Thursday.
Usually 5 days out, we`re talking about model uncertainty...one
model shows one thing and others show another. Or that there are
timing differences, but not this time! Consistency has been pretty
remarkable with the cold air forecast to move through much of the
country in the later half of this week. It`s not very often what the
models are showing in the 240+ hour range holds up, but baring any
unexpected changes, it looks like it will this time.
Mid and upper level trough deepens as it moves into the central US
and will usher in the coldest air we`ve seen since February 2021.
That said...this situation has some important differences from 2021.
First, we`re not expecting precipitation. There may be enough
moisture/forcing for some showers over the Gulf of Mexico, but as
far as land areas, at times of freezing temperatures, we look dry.
Second, daytime temperatures are expected to warm above freezing
each day. Yes, it`s going to be cold, but it doesn`t compare to 2021.
A cold front will blast through the area (yes, blast looks to be
an appropriate verb) Thursday afternoon or evening with strong winds
and very cold temps following closely. Temperatures fall from the
60s for highs Thursday into the lower and mid 20s for much of the
area by Friday morning...The Victoria Crossroads and portions of the
northern Coastal Plains could even fall into the teens assuming
skies clear as quickly as expected. The strong winds accompanying
these low temperatures will bring dangerously cold wind chills in
the teens and possibly single digits for some areas. It`s not out of
the question that we may have to issue a wind advisory for islands
and coastal portions of counties behind the front with gale
conditions in the marine areas a near certainty.
High temperatures on Friday could stay in the 30s for much of the
area before falling into the 20s once again Friday night. A coastal
trough develops into the weekend and will push some moisture into
the coastal areas which will a) keep temps from falling as cold near
the coast and b) bring the potential for an isolated cold shower by
Saturday night into Sunday. Important note...the moisture increase
that would lead to these showers should also keep temperatures above
freezing. Looking ahead into Christmas day, temperatures will begin
to rebound with highs expected back into the upper 40s and 50s.
&&
.AVIATION...
(00Z TAFS)
Issued at 558 PM CST Sun Dec 18 2022
Good aviation conditions, with VFR ceilings from 5-6 kft across
most of south Texas except for high end MVFR ceilings near LRD at
this time, will deteriorate tonight as the coastal trough
develops. The low level warm air advection will increase this
evening leading to ceilings falling through MVFR during the
evening hours except for the Victoria Crossroads. Showers will
develop over the Coastal Bend after midnight with ceilings falling
to IFR over most of south Texas, except for MVFR ceilings for VCT
area. LIFR ceilings and IFR vsbys with showers will affect the
coastal plains during the early to late morning hours as the low
drifts to the northeast along the coast. Isolated thunderstorms
may develop within the area of showers over the Coastal Bend
between 10-16Z while TSRA will be possible at VCT from 14-18Z.
Ceilings will gradually lift to MVFR over the Brush Country by
late afternoon, maybe even see some clearing skies for LRD. IFR
ceilings and MVFR vsbys will linger over the coastal plains during
the afternoon while precipitation activity moves to the east.
&&
.MARINE...
Issued at 343 PM CST Sun Dec 18 2022
Continue to expect a coastal trough or closed low to develop
along/near the coast tonight/early Monday morning, which should
contribute to numerous to scattered showers and isolated
thunderstorms. Moderate to strong onshore flow and high seas are
expected tonight through Monday morning. Conditions will gradually
improve from west to east as the surface low moves east. Extended
the Small Craft Advisory to 00z Tuesday for the coastal waters. A
moderate to strong north wind will develop Tuesday across the
region. Winds become moderate from the east and southeast
Wednesday ahead of a strong arctic cold front Thursday. Very
strong northerly winds and elevated seas are expected behind the
cold front Thursday and Thursday night with gale conditions likely
Thursday night through Friday morning. Very cold air will drop
temperatures into the 30s for much of the Middle Texas area
Thursday night and portions of the area Friday night.
&&
.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi 57 61 47 61 / 70 70 0 0
Victoria 49 55 45 59 / 50 80 10 0
Laredo 49 58 47 66 / 50 10 0 0
Alice 52 58 45 63 / 70 50 0 0
Rockport 55 62 47 60 / 70 80 10 0
Cotulla 48 56 45 65 / 50 20 0 0
Kingsville 55 60 47 62 / 70 50 0 0
Navy Corpus 59 64 49 60 / 80 80 10 10
&&
.CRP WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk until 6 AM CST Monday for TXZ345-442-443-
447.
GM...Small Craft Advisory until 6 PM CST Monday for GMZ250-255-270-
275.
&&
$$
SHORT TERM...TMT/89
LONG TERM....PH
AVIATION...TMT
Area Forecast Discussion
National Weather Service Des Moines IA
534 PM CST Sun Dec 18 2022
...Updated for the 00z Aviation Discussion...
.DISCUSSION.../Tonight through Sunday/
Issued at 352 PM CST Sun Dec 18 2022
Forecast Highlights:
- Quiet tonight into early Monday, warming slightly
- Snow expected Monday, which may mix in with some freezing
drizzle/rain at times later in the day
- Large and impactful system Wednesday/Thursday with many inches of
snow possible, windy and arctic cold especially Thursday/Friday
GOES Satellite Imagery clearly depicts the recently fallen snow from
earlier this week across Iowa, thanks to sunny skies as snow can be
seen across central and northern Iowa while the far south/southeast
remains bare. A short lived high pressure system continues to pass
through the state into the afternoon, with generally chilly
conditions as temperatures have struggled to increase much through
the day. Despite the cloudless skies, snowpack has helped keep
temperatures cooler in the teens north of I-80 and in the 20s
further south where there is no influence from any snowpack. Winds
remained light out of the northwest which continues to reinforce the
cooler air. Quiet conditions are expected to continue this evening,
though as low level flow shifts southwesterly this evening into
Monday, warm air advection with increasing moisture will bring a
return of clouds into the state. Overnight lows are expected to fall
into the single digits north and in the teens south.
A shortwave traveling northeast from the Desert Southwest later
today into the Central Plains Monday is expected to bring the next
system to the state. Deterministic models have generally slowed the
arrival of precipitation slightly, moving into the state from
southwest spreading northeast in the mid to late morning. Recent
runs of the GFS and Euro have trended the higher QPF amounts
slightly further west than has been seen in earlier runs, which
would place the highest totals along and west of I-35 Monday.
However the NAM is more consistent placing the higher amounts
along central Iowa as has been the trend over the previous runs,
which the RAP and HRRR also captures. Overall, QPF amounts have
not changed much, with general accumulations in the 0.05 to 0.15
inch range before ending late Monday/early Tuesday. Snowfall
accumulations between 1-2 inches are still generally expected at
most, with less elsewhere across the state. With some ice
introduction lost late Monday into Tuesday across parts of eastern
Iowa despite low level saturation per soundings, some freezing
drizzle could occur with overall little accumulations. The RAP and
HRRR does introduce freezing drizzle Monday afternoon/evening to
Tuesday with at least little accums, though the NAM, GFS and Euro
remain colder with no ice concerns. Confidence is not very high
however and if anything would likely be rather isolated, but will
depend on how conditions evolve through the event so will keep an
eye on this. For now have continued to mention freezing
rain/drizzle in the forecast but little to no ice accumulations at
this time.
Dry conditions return Tuesday but will come with the passage of a
cold front pushing northwest to southeast through the morning into
the afternoon. This will bring in the first round of much chillier
temperatures with returning northwesterly flow. This frontal passage
will however be paired with drier air which will keep conditions
otherwise dry for the day into Wednesday morning. Morning lows are
expected to fall into the single digits northwest and in the teens
further southwest, before topping out in the single digits to teens
into the afternoon.
A very large and impactful system developing from a deepening trough
is expected to pivot into the Northern Great Plains and eventually
Upper Midwest by midweek. Deterministic models have trended an
earlier arrival of widespread snow in most recent runs, arriving
into western Iowa into Wednesday afternoon before spreading east
across the state into the evening. The evolution of the system
remains a bit more uncertain, as the GFS and NAM depict less robust
forcing for widespread heavier QPF amounts Wednesday and Thursday
before cyclogenesis forms a closed low further into the Ohio Valley,
as the greater moisture content remains further south and east. The
Euro however continues to be in better favor of this low pressure
system becoming better defined into Thursday over Iowa, with much
better forcing and moisture availability. Despite these continuing
differences, accumulating snowfall is expected to be widespread and
highest Wednesday evening throughout Thursday, with at least a few
if not several inches falling before finally exiting the state into
Friday. Along with this, a strong signal remains in place for gusty
winds Thursday and Friday out of the northwest, with gusts looking
to occur around 35 to 40 mph for most areas of the state. This will
cause for blowing snow and resulting potential blizzard conditions,
leading to additional hazards for travel of any kind. If the wind
and snow isn`t enough, dangerously cold air dropping into the region
from an arctic airmass will allow for extremely bitter
temperatures Wednesday and especially through Thursday and Friday.
Morning lows will generally fall into the single digits to teens
below zero across the state, with highs only reaching into the
just above and below zero. Lowest wind chills in the -20s to -40s
are looking likely as well. In summary, the weather is going to be
extremely unpleasant and will be hazardous if traveling or going
outdoors for longer periods of time. Please plan ahead and
consider adjusting travel plans as needed in order to avoid these
conditions as much as possible.
&&
.AVIATION.../For the 00Z TAFS through 00Z Monday evening/
Issued at 534 PM CST Sun Dec 18 2022
VFR conditions will prevail through the night and Monday morning,
then low ceilings and light snow will spread from into the area
from the southwest from around midday into the evening. Have
advertised the trend of deteriorating conditions in the 00Z TAFs,
however timing and magnitude are estimates at this range and will
be refined in later TAF issuances.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
DISCUSSION...Bury/Donavon
AVIATION...Lee
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
543 PM CST Sun Dec 18 2022
...AVIATION UPDATE...
.DISCUSSION...(This evening through Sunday)
Issued at 230 PM CST Sun Dec 18 2022
Key Messages:
* HIGH CONFIDENCE in strong winds and very cold air combining to
produce very dangerous wind chill values of -25F to -45F
Wednesday night through Friday morning.
* MEDIUM HIGH CONFIDENCE in travel impacts due to snow and blowing
snow, especially on Thursday. Winds WILL be strong, but there is
still some uncertainty regarding snowfall amounts. Currently it
looks like at least a couple inches but any snow with those
winds will likely impact visibility and cover roadways with
snow.
* LOW to MEDIUM CONFIDENCE in a light wintry mix of light snow
and freezing drizzle east and southeast of the Tri-Cities Monday
morning.
* Confidence is increasing of a warming trend starting Christmas
weekend.
Forecast Details:
Starting with the first potential impact tonight and into Monday
morning, a shortwave trough will move across the area, pulling
precipitation northeast through Kansas and eastern Nebraska. Most
of this precipitation will remain east and southeast of the
forecast area, but model guidance continues to show a chance that
our eastern and southeastern counties could get impacted by this
system. The timing is still a little questionable especially with
the HRRR trying to push this later on in the morning, but most
likely from the early morning hours Monday through around noon.
Most of this will be in the form of flurries but model guidance
and forecast soundings do show a brief period of freezing drizzle
potential southeast of the Tri-Cities (meaning ice impacts are NOT
currently expected in the Tri-Cities). If freezing drizzle does
develop, roads and sidewalks will become slick and the morning
commute in those areas will likely be affected (this would be one
of those low chance but potentially impactful events). Seeing as
most of the model guidance indicates no ice at all, we elected not
to issue any advisory at this time...but will be watching it
closely.
Starting Monday afternoon, high pressure begins to dive into the
region from Canada and the northern Plains, and this will lead to
a fairly wide temperature gradient within the forecast area. Highs
Monday will range from the upper teens north to the mid to upper
30s south. This cold air will deepen Monday night and Tuesday, and
breezy north winds Monday night will bring about the first night
of widespread below zero wind chills, with values of -5F to nearly
-20F Monday night/Tuesday morning. Tuesday night, winds will be
lighter and wind chill values will not quite be as cold.
The most impactful period of this forecast will be the strong
winds and deep Arctic cold temperatures Wednesday night through
Friday. In addition, there is increasing confidence in at least a
couple of inches of snow with this, so blowing snow is also
becoming an increasing concern Wednesday through Friday. The first
point of note will be the strong winds and dangerously cold wind
chills. Winds will start to increase Wednesday and at the peak of
this event Thursday, north winds will be gusting to 40-45 mph
Thursday. With the Arctic cold and strong winds, wind chill values
will be in the -25F to -45F range Wednesday night THROUGH Friday.
Wind chills this low can cause frostbite to unprotected skin in as
little as 10-15 minutes, just to give an idea of how quickly these
values can be impactful.
Now that we have covered wind chill, there is also the snow
element to this. There is increasing confidence in at least some
snow but amounts are still somewhat uncertain...latest WPC
ensemble plumes suggest around 2" to 4" but there are still a few
days to nail that down and those numbers could trend either way at
this point. Regarding timeframe, latest model guidance indicates
this will move in Wednesday morning with the bulk of the snow
falling Wednesday evening and overnight, then moving out to the
east Thursday morning. With temperatures as cold as they will be,
this will be a dry, powdery snow with higher than normal liquid
to snow ratios (LSRs). Some of the deterministic models like a
ratio in the low 20s:1, but chose to go a bit lower due to the
probability of dendritic fracturing in those strong winds. No
matter what the LSR or the snowfall amount, any snow that falls
will blow around, and it does not help that those are a couple of
the busiest travel days just before Christmas. It is too early to
be forecasting "blizzard" conditions especially with uncertain
snowfall amounts, but the potential is in our minds as we get
closer to this event. Keep in mind if traveling that the
combination of blowing snow, poor visibility, and bitter cold wind
chills could make travel conditions very dangerous very quickly.
Once we get past the bitter cold wind chills Wednesday night
through Friday, temperatures will start to moderate going into
Christmas weekend. High temperatures Saturday will climb into the
teens and 20s and by Christmas Day there may even be a few places
that make it above freezing.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Tuesday)
Issued at 538 PM CST Sun Dec 18 2022
VFR conditions until around 08Z then cigs will come down to around
MVFR then down further to IFR around sunrise. Cigs will be the
main concern this period with MVFR and IFR conditions through part
of the overnight and throughout most of tomorrow. Cigs will begin
to scatter out tomorrow late afternoon into the early evening.
Winds will shift in the next few hours from southeasterly to more
easterly then northeasterly overnight then more northerly by
midday tomorrow. Speeds will be generally modest at around 5-10
kts.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
DISCUSSION...Hickford
AVIATION...Shawkey
AREA FORECAST DISCUSSION...CORRECTED
National Weather Service Charleston WV
728 PM EST Sun Dec 18 2022
.SYNOPSIS...
Snow showers become confined to the mountains tonight, clearing
elsewhere. High pressure first half of next week. A strong
storm sends arctic air by end of week.
&&
.NEAR TERM /THROUGH MONDAY/...
As of 645 PM Sunday...
Haven`t had to make too many tweaks to the forecast this
evening. Adjusted temperatures and dew points in the grids to
reflect current obs.
Clearing in the lowlands is right on time as high pressure
continues sliding in. Snow showers are going to continue
tonight in the mountains. The main ponder is to when these
showers will finally taper off and move out. Current guidance is
suggesting snow showers to continue throughout the night for
Randolph and Pocahontas counties. Canadian model keeps these
showers past midnight tonight. GFS and EURO shutting them off
before midnight. The RAP Keeps a mountain wave over the
mountains of Pocahontas and Randolph tonight which will hold the
low clouds overhead and enhance snow shower activity tonight.
Certainly thinking it is possible for snow showers to continue
through morning for the western facing slopes in these counties.
Particularly areas such as Snowshoe, Elkins, Buckhannon, and
Clarksburg will see this activity. Not expecting any
accumulations past a quick hundredth or tenth though. High
pressure will dominate the weather pattern starting tomorrow. Some
lingering clouds are possible for the mountains.
As of 1230 PM Sunday...
Snow showers/flurries gradually taper off from south to north
through this evening across the lowlands, persisting into the
overnight in the mountains.
Channeled vorticity associated with an area of upper level low
pressure south of Hudson Bay will lift north out of the region
through late this afternoon. Should see a marked decrease in upper
level seeder clouds as this occurs which should yield less coverage
of snow showers/flurries. Additional cold air stratocumulus is
already developing across Ohio as upper level cloudiness clears, and
would expect this trend to continue in our area. This will yield
continuing isolated/scattered show showers/flurries through late
this afternoon/early this evening across the lowlands when surface
heating is lost. Additional snow accumulations across the lower
elevations will be light, generally less than a tenth of an inch,
although any more persistent bands could produce slightly more. In
the mountains, upslope enhanced snow showers likely continue through
daybreak Monday, although once heating is lost this evening
additional accumulations will be minimal.
Surface high pressure begins to build in overnight amidst clearing
skies. Not expecting a perfect radiational cooling night with light
westerly flow continuing into the pre-dawn hours, but would expect
better protected low spots to fall to saturation yielding
temperatures in the upper teens to lower 20s, especially
locations holding onto a little bit of snow cover over grassy
surfaces. The main concern overnight will be a potential
refreeze, primarily on elevated surfaces such as bridges and
overpasses. The modest westerly wind should assist in
alleviating some of this concern as it assists in drying
surfaces.
Monday remains chilly with highs struggling to get out of the mid
30s amidst increasing upper level cloudiness in response to a
southern stream system that will otherwise have little impact to our
sensible weather.
&&
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 210 PM Sunday...
High pressure continues to keep the area dry through Wednesday
afternoon. With a relatively persistent pattern during this
time, highs will climb into the 40s with overnight lows in the
20s. Winds will be generally light under ten mph during this
weak pattern.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 210 PM Sunday...
A winter storm continues to be the main focus for the extended forecast
Thursday night through Saturday as a powerful storm tracks across the
plains to the northeastern states.
Wednesday night rain and snow showers along with gusty
southerly winds are expected to develop as disturbances moves up
from the south, ahead of a deepening trough over the plains.
Warm air advects across the region early Thursday as the front
punches to the north, which will change any snow over rain for
the lowlands fairly quickly. The mountains may be slower to
change over and could maintain a few pockets of cold air that
will keep localized snow, or perhaps a wintry mix including ice
pellets. Details on these precipitation types still need refining.
There could be a short break in precipitation Thursday afternoon across
the lowlands behind the frontal passage; but, a strong cold front
quickly follows bringing precipitation challenges areawide Thursday
night through Friday. The track of the low is critical on working
out the details for precipitation types. All models are in
relatively good agreement on arctic air to arriving by mid day
Friday. The GFS model continues to be an outlier with the low
position, tracking the storm slower and farther south than the
ECMWF and Canadian models. The GFS solution would support a
longer duration of rain into Friday with snow heavier snow lasting
into the evening hours. The populated NBM into the forecast is
influenced by the colder model solutions which brings the
front/higher chances for accumulating snow through early in the
day Friday with scattered chances diminishing from the west
overnight.
Cold arctic air settling Friday night drops temperatures down
into the single digits and lower, which will be the chilliest
of the season thus far. North to westerly breezes behind the
front will also make temperatures feel even colder into
Saturday.
&&
.AVIATION /23Z SUNDAY THROUGH FRIDAY/...
As of 700 PM Sunday...
Currently, ceilings are raising from southwest to northeast as
high pressure moves in. Skies are either clearing or lifting
and scattering out. Subsequently, most sites in the lowlands and
southern mountains have improved to VFR and will stay that way.
EKN is at MVFR and will keep this category most of the night.
Clearing will continue overnight except for the northeastern
mountains where MVFR/IFR ceilings will be probable through the
morning hours tomorrow as upslope continues. Light upslope snow
showers at EKN/CKB could persist through early tomorrow
morning. Periods of MVFR/IFR visibility are possible in some
heavier snow showers.
Finally, tomorrow VFR will be widespread at all sites after 15Z
tomorrow as high pressure dominates. Decoupling may not be
widespread under uniform westerly flow so some passing clouds at
18k-23k feet are possible late tomorrow.
Winds this period becoming predominantly more westerly at
speeds of 3-8KTs tonight. BKW may keep a more WNW/NNW flow from
4-9KTs before becoming more westerly tomorrow.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z TUESDAY...
FORECAST CONFIDENCE: High.
ALTERNATE SCENARIOS: Localized heavier snow showers could yield
IFR conditions for longer than advertised at CKB/EKN tonight.
Improvement to VFR in the mountains tomorrow may vary from
forecast.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
UTC 1HRLY 22 23 00 01 02 03 04 05 06 07 08 09
EST 1HRLY 17 18 19 20 21 22 23 00 01 02 03 04
CRW CONSISTENCY H H H H H H H H H H H H
HTS CONSISTENCY H H H H H H H H H H H H
BKW CONSISTENCY H H H H H H H H H H H H
EKN CONSISTENCY H H H H H H H H H H H H
PKB CONSISTENCY H M H H H H H H H H H H
CKB CONSISTENCY M M H H H H H H H H H H
AFTER 00Z TUESDAY...
IFR possible in rain and snow early Thursday morning. IFR in
snow possible Friday morning.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...None.
OH...None.
KY...None.
VA...None.
&&
$$
SYNOPSIS...KH/JP
NEAR TERM...LTC/JP
SHORT TERM...KH
LONG TERM...KH/JZ
AVIATION...LTC