Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/21/23
Area Forecast Discussion
National Weather Service Buffalo NY
1047 PM EST Mon Nov 20 2023
.SYNOPSIS...
Low pressure will move from the Ohio Valley to the eastern Great
Lakes Tuesday through Tuesday night, before giving way to secondary
low pressure along the east coast. Rain will overspread the area
from west to east Tuesday. The rain will likely start as a brief
period of freezing rain across portions of the Southern Tier, and as
a mix of snow, sleet, and freezing rain for portions of the North
Country before changing to all rain. It will also become very windy
Tuesday, especially along the Lake Erie shore. Leftover showers will
gradually end Wednesday, followed by mainly dry weather for the rest
of the week.
&&
.NEAR TERM /THROUGH TUESDAY NIGHT/...
High pressure will result in dry weather the rest of tonight with
high clouds increasing from west to east. Light winds, mostly clear
skies, and a chilly/dry airmass this evening is leading to excellent
radiational cooling which is allowing temperatures to drop back into
the mid to upper 20s in Western NY, low to mid 20s from the Genesee
Valley into the western Finger Lakes, and teens east of Lake
Ontario. Lows will likely occur into the early overnight, especially
across Western NY. Increasing southeast winds and clouds will force
temperatures to start rising before daybreak, most notable along the
Lake Erie shoreline.
Tuesday through Tuesday night a mid level trough will advance east
across the Great Lakes and Ohio Valley, with a surface low tracking
from Indiana Tuesday to just north of Lake Erie Tuesday night. A
powerful 75+ knot low level jet will transport deep moisture
northward into the eastern Great Lakes. Strong low level convergence
on the nose of the low level jet will enhance isentropic upglide and
combine with strongly diffluent mid/upper level flow to support a
shorter period of deep layer ascent moving from southwest to
northeast across the area Tuesday through Tuesday evening.
Precipitation type will be rain for the majority of the area through
this event with a few exceptions which will be discussed below. The
first of the rain will enter the southwest corner of NY mid to late
morning, then rapidly spread northeast through the remainder of
Western NY by midday to early afternoon before reaching the eastern
Lake Ontario region by mid to late afternoon. The steadiest rain
will be with this initial wave of warm advection, with more
intermittent rain following in the warm sector of the approaching
low. Rainfall amounts will be heavily modulated by terrain
influences, with downslope areas seeing considerably less than higher
terrain and upslope areas.
Wintry Mix Potential...
Increasing warm advection and downslope compressional warming will
allow temperatures to move above freezing in most areas prior to the
arrival of the rain, with a few exceptions...
Across the Southern Tier, forecast soundings and high-res guidance
continue to suggest a shallow sub-freezing layer persisting through
early to mid afternoon across portions of Cattaraugus and Allegany
counties. This will support the likelihood of some pockets of
freezing rain for a few hours midday through mid afternoon before
temperatures rise above freezing. The brief window will keep ice
accretion very light, with a few hundredths of an inch possible.
East of Lake Ontario, there will be a little longer window from mid
to late afternoon through the evening, particularly across Lewis
County. A colder start, and evaporative cooling may allow the column
to remain cold enough to support snow briefly at the start. If this
occurs, there may be a quick 1-2" of snow accumulation, mainly
across the Tug Hill and western foothills of the Adirondacks. A warm
nose aloft will then force a change to sleet and freezing rain
Tuesday evening, with ongoing warm advection then supporting just
plain rain after midnight. Ice accretion should be very light in
most areas, but high-res guidance continues to support up to a
quarter inch or so of ice for the southern Tug Hill where
temperatures will remain near freezing longer. For Jefferson and
Oswego counties, most of the wintry mix potential will be limited to
the far eastern and northern portions, with mainly rain near the
population centers of Fulton/Oswego/Watertown.
Strong Winds...
Model guidance continues to trend stronger and stronger with the
forecast low level jet on the front side of this system. 12Z NAM and
GFS soundings and recent NAM and RAP guidance show a 75+ knot SSE
low level jet crossing Western NY Tuesday. The strength of the low
level jet within the warm advection ahead of the system is high end,
and raises concerns for a downslope windstorm in susceptible areas.
The peak of the low level jet crosses Western NY during the
afternoon and early evening, with 65 knots in forecast soundings
located just above the terrain barrier of the Chautauqua Ridge. The
wind direction is favorably oriented to the terrain barrier, and
forecast soundings show a stable layer persisting near the ridge
tops. All of these ingredients point towards a downslope windstorm
to the lee of the Chautauqua Ridge, with a standing wave developing
in the stable air above the terrain and supporting acceleration of
stable air down the lee slopes near the Lake Erie shore. The 12Z
HREF probabilistic data supports a very high likelihood of a narrow
zone of warning criteria gusts along the Lake Erie shore with this
setup.
With this in mind, a High Wind Warning is in effect for Chautauqua
and southern Erie counties for Tuesday and Tuesday evening. Farther
east, sporadic gusts of 45-50+ mph are likely where downsloping
occurs off smaller ridges across the northern portions of the
Southern Tier, and in the western Finger Lakes. A Wind Advisory has
been issued in these areas. There may be a brief window of near
Advisory gusts near the northern slopes of the Tug Hill as well, but
this setup looks more marginal and brief.
Later Tuesday night the strong winds will rapidly subside from west
to east as the low level jet exits. Precip type will also change to
all rain east of Lake Ontario.
&&
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Trough axis connecting both the northern and southern stream troughs
will pass across the Eastern Seaboard Wednesday morning, resulting
in the broad based northern stream trough to center across the area
an place zonal flow across the region by Thanksgiving morning.
Overall this will result in a cold front to cross the region
Wednesday with surface high pressure to quickly build in by
Wednesday night and last through Thursday.
Deciphering this pattern, will mean Wednesday the last of the
precipitation will finish crossing from west to east Wednesday
morning into the afternoon ahead of the cold frontal passage. The
cold frontal passage will usher in cooler air across the region
starting Wednesday morning, meaning highs across the west will occur
early in the day. Additionally, lingering moisture and upslope flow
will favor a few rain and mix of rain and snow showers east and
southeast of Lakes Erie and Ontario Wednesday afternoon. As the
surface high builds east into the region late Wednesday and into
Wednesday night the shower potential will dwindle down across the
west, while a few showers will linger east/southeast of Lake Ontario
Wednesday night.
Thursday, high pressure will continue to build overhead. The
combination of the subsidence and dry air from the surface high will
act to diminish lake effect showers east of Lake Ontario during the
day. A brief uptick in shower activity east of Lake Ontario may
occur Thursday night as a clipper system pushing northeast across
southern Canada will advect in a limited amount of moisture.
Otherwise, expect the Thanksgiving holiday to be near normal with
highs in the low to mid 40s.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
Zonal flow spread across the area Friday morning will give way to an
upper level ridge pushing east across the central and eastern Great
Lakes Saturday. Overall, surface high pressure will remain spread
across the region throughout the end of the week and into the start
of the weekend, and therefore dry weather is expected to continue.
Heading into the later half of the weekend and into the start of the
new work week, model guidance continues to remain diverged with the
timing/placement and strength of the next upper level trough and
corresponding surface low. In a general sense, moisture will advect
into the region to support some rain and snow showers late Sunday
through Monday. The forecast resembles some chances for
precipitation throughout the end of the weekend/start of next week
due to the elevated forecast uncertainty because of the model
disagreements.
&&
.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
High pressure will drift east of the area tonight, with VFR
prevailing through most of Tuesday morning as high clouds thicken
and lower from west to east.
Low pressure will move from Indiana Tuesday to just north of Lake
Erie Tuesday night. Rain will spread northeast across the area from
late morning through afternoon Tuesday. Precip type will be rain in
most areas, but there may be a brief period of freezing rain across
portions of the Southern Tier east of KJHW at the onset. There will
also likely be a period of snow, sleet, and freezing rain east of
Lake Ontario late Tuesday afternoon and evening, mainly east of KART
and KFZY.
CIGS will lower to MVFR across the higher terrain from west to east
Tuesday afternoon as low levels saturate. Some of the lake plain
locations will benefit from increasing downslope flow, which may
help to keep CIGS VFR. South to southeast winds will become very
gusty Tuesday afternoon, with 25-35 knot gusts areawide, and
localized gusts of 40-50+ knots along the Lake Erie shore. There
will also be a period of strong low level wind shear prior to the
increase in surface gusts, as a strong low level jet arrives.
Outlook...
Tuesday night...MVFR/local IFR with rain. Mixed precip east of
Lake Ontario changing to all rain. Strong winds in the evening
diminishing overnight.
Wednesday...Areas of MVFR ceilings with rain showers ending.
Thursday through Saturday...Mainly VFR.
&&
.MARINE...
High pressure will continue to drift east of the area tonight, with
low pressure moving into the Ohio Valley and Great Lakes Tuesday.
Southeast winds will start to increase late tonight and become quite
strong Tuesday through Tuesday evening. This wind direction is
offshore with higher wave action in Canadian waters, but nonetheless
the strength of the winds will still support solid Small Craft
Advisory conditions on Lake Erie and most of Lake Ontario.
Winds will swing around to the southwest by Wednesday morning, and
then northwest later Wednesday behind the system. These winds will
not be as strong, but still may allow Small Craft Advisory
conditions to continue on Lake Ontario.
&&
.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Weather Advisory from 3 PM to 10 PM EST Tuesday for
NYZ006-007.
Winter Weather Advisory from 3 PM Tuesday to 4 AM EST
Wednesday for NYZ008.
Wind Advisory from 11 AM to 11 PM EST Tuesday for NYZ012-020.
High Wind Warning from 9 AM to 11 PM EST Tuesday for NYZ019-
085.
MARINE...Small Craft Advisory from 7 AM Tuesday to 1 AM EST Wednesday
for LEZ040-041.
Small Craft Advisory from 1 PM Tuesday to 1 AM EST
Wednesday for LOZ043>045.
&&
$$
SYNOPSIS...Hitchcock
NEAR TERM...Hitchcock/JLA
SHORT TERM...EAJ
LONG TERM...EAJ
AVIATION...Hitchcock
MARINE...Hitchcock
Area Forecast Discussion
National Weather Service Columbia SC
646 PM EST Mon Nov 20 2023
.SYNOPSIS...
Light showers will develop late tonight ahead of a strong cold
front. The front will bring widespread showers and potentially
strong to severe thunderstorms to the area Tuesday afternoon and
evening. Drier air fills in briefly Wednesday before rain
chances return late in the week.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Closed upper low, currently over E KS/W MO with trough
extending south into TX, will move slowly east into the Mid Miss
Valley tonight. Associated surface low, currently near
ArkLaTex, progged to shift east into the Lower Miss Valley, then
NE into the lower Ohio Valley, through late tonight. This will
drag a cold front slowly east into the Deep South, while strong
surface high pressure remains anchored over E Can/New England
region. H85 flow progged to veer from SE to S and increase in
speed tonight, leading to increasing isentropic lift and
moisture transport. Plenty of mid level moisture/clouds over the
region currently, but low levels are still dry, evidenced by
large surface dewpoint depressions and dry air noted below H85
on recent ACARS sounding out of GSP. As isentropic ascent
develops and increases tonight, will expect some light
precipitation to develop. Current radar mosaic indicating some
showers offshore, with returns over NC appearing to be mainly
mid level cloud cover/virga. Latest HRRR indicates patchy light
rain developing and shifting north across portions of the
forecast area (FA) tonight, becoming more widespread and
pronounced mainly to our north in response to orographic lift
and surface cold air damming regime setting up over the piedmont
of the W Carolinas. So, latest model guidance indicating higher
POPs northern areas. Cloud cover and wind staying up will lead
to much above normal low temps in the 50`s.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Complex forecast for Tuesday and Wednesday of this Thanksgiving
week. Large, longwave trough over the central US will begin
translating east and northeastward tonight as a 90+ knots 500 hPa
jet streak, currently over west TX, rounds the base of the trough
and ejects towards the OH Valley region. Ridging at 500 hPa will
precede this, and the convergence aloft noted in advance of this
feature will help to establish an intense surface high across New
England by Tuesday morning. This is already having impacts on our
area, with surface ridging noted on the eastern slopes of the
Appalachians and into the central Carolinas this morning.
Intensifying surface low is expected to be pushing into the central
OH Valley by 7a Tuesday morning, with a cold front trailing it into
central Alabama. Expecting that we`ll be firmly locked into an in-
situ wedge situation as this scenario unfolds, as the surface high
over New England will intensify tonight and result in pesky surface
ridging persisting north of a northward advancing cold front. This
will be reinforced by increasing isentropic ascent between 295K and
300K surfaces as low-level flow intensifies as a result of intense
cyclogenesis upstream. So expecting scattered to numerous rain
showers Tuesday morning because of this, and these should last
through midday, with copious low-clouds as well.
The expectations for Tuesday afternoon and evening are becoming more
clear; though, there are some caveats to note in this forecast.
Model guidance continues to suggests that very strong warm air and
moisture advection will overspread the region between 7a and 10a on
Tuesday, helping to push the surface warm front northward and "scour
out" the low-level wedge conditions. I am skeptical in this scenario,
A) actually occurring, and
B) having any significant impact on our severe weather chances.
There will be an impressive low-level mass response to the upstream
cyclone intensifying over the OH Valley, with 850 hPa flow
increasing to 40 to 50 knots by midday. While this is likely intense
enough to result in the warm front lifting northward, the magnitude
of warm air advection may result in another round of widespread
showers developing well ahead of the actual front itself. CAM
guidance is more on board with today`s 12z suite of runs, casting
uncertainty on whether or not we`ll actually be able to recover
enough instability by Tuesday evening ahead of the front to make any
sort of difference in convective strength and potential. This is
highlighted by the most aggressive 00z model (the HRRR) backing on
considerably on MLCAPE in recent runs (most notably, the 12z). So
even if we do actually break out of surface wedging (again, models
do not handle these scenarios well), it seems unlikely that we`ll be
able to destabilize enough to support intense convection during the
evening hours. This is especially due to the intensity of the low-
level shear, which will be on the order of ~40kts of 3km shear by 7p
Tuesday. Shear of this magnitude, without even modest CAPE, is
typically too strong to sustain deep convection.
All of this is complicated by the timing of the front. Guidance is
starting to trend towards a slower approach of the front itself &
any convection along it. This owes to the strongest diffluence aloft
moving well to our north by Tuesday night and early Wednesday, with
another shortwave diving into the lower MS Valley behind it. This is
usually a setup for a front to very slowly move into and through the
area, and I expect that to be the result of this overall setup. As a
result, I am not confident that we`ll see severe weather on Tuesday
evening. The combination of an unfavorable time of day, slow moving
front, showers ahead of the line, and weaker forcing should limit
the overall ability for storms to get going. If a strong storm does
develop, though, it will be capable of damaging winds given the
strength of the shear in the low levels.
There is an increasing likelihood that the second shortwave I
mentioned above will interact with the slow moving front on
Wednesday to create a favorable setup for widespread rainfall during
the day. Right now, it looks like the central and southern FA is in
line for the most precip with this as the front looks to be slowing
down and closest to this area on Wednesday, but confidence isn`t
high in the exact placement of that front. PWs in the 1.2-1.5" range
will certainty suffice for good rainfall, but the IQR range for
totals is very high within ensembles for rain associated with this
wave specifically, with HREF, GEFS, and ECE IQR for 24h precip all
approaching 1". Regardless, it does look like clouds and cooler
temps are likely, especially if we do see the rain that models are
trending towards. Will opt to err on the low side of guidance as a
result, with temps likely staying in the low 60s. The shortwave will
pass through on Wednesday night, pushing rain chances eastward as
well. Temps will fall into the 40s.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
Thanksgiving looks really nice, as we`ll have dry surface high
pressure settle over the region beneath convergence aloft. This
should make for a fantastic setting for any backyard football games
or any other outdoor Thanksgiving traditions. Highs will likely be
in the low 60s under sunny skies. Clouds will increase late in the
day as another weak shortwave translates northeastward to bring
some more showers by Friday. These should be light given the
dry air in place. Beyond this, really didn`t change too much
from the NBM given the uncertainty in the forecast between now
and Thursday.
&&
.AVIATION /23Z MONDAY THROUGH SATURDAY/...
VFR early this evening then ceilings expected to lower to MVFR
late with some showers near the TAF sites near daybreak.
Considerable VFR strato-cumulus and alto cumulus across the
region early this evening with strong high pressure to the north
extending into the area. Expect clouds to lower to MVFR by
around 06z as low level moisture increases due to increasing
low-level flow 25 to 35 kts. High resolution models suggest
some light showers late tonight/toward morning. Other concern is
low level wind shear so will monitor later this evening. Weak
cold air damming in the morning but the warm front will be near
the area, moving to the north. So ceilings may improve later in
the morning, especially at AGS and DNL. Stronger instability
possible in the CSRA, and a few thunderstorms possible in that
area by afternoon. Showers should be numerous/widespread at
times through the day and visibility may be reduced especially
in the morning if wedge conditions hold. Weak instability in the
afternoon and a few elevated thunderstorms possible but
confidence low. Cold front approaching from the west late in the
period. Will keep MVFR through the period. Winds will be east
near 10 knots early tonight and shift to southeast/south 10 to
20 knots with a few higher gusts by 18z Tuesday.
EXTENDED AVIATION OUTLOOK...A cold front will move through the
area Tuesday night with showers/possible thunderstorms and
associated restrictions expected Tuesday night into early
Wednesday. Improvements occur Wednesday into the first part of
Thursday, with another round of restrictions possible late
Thursday and Friday.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion...CORRECTED
National Weather Service Goodland KS
301 PM MST Mon Nov 20 2023
.SHORT TERM...(This evening through Thursday Evening)
Issued at 107 PM MST Mon Nov 20 2023
Surface low is located across southern Oklahoma with the as the
High Plains as a result are in the cool sector with wraparound
precip occurring. Consistent drizzle and waves of light rain have
been occurring thus far through the day. SPC Mesoanalysis page
shows another wave moving into the area from the Nebraska
Panhandle. This along with a 250mb jet exit region moving into the
Tri-State area will continue to provide additional lift through
the remainder of the afternoon and early evening hours. Isentropic
ascent will then provide additional lift as the jet streak moves
slowly east, through the evening. Overall QPF looks to remain a
couple hundredths of an inch but isolated locales may see perhaps
a tenth of inch as some locally heavy cells have developed. RAP
forecast soundings across portions of the area show wet bulbing
to around 2-3C which would be supportive of some snow mixing in
at times given if precipitation is heavy enough at times. This is
especially favorable across east Colorado where some blowing snow
concerns could materialize through the mid to late afternoon just
given the strength of the wind.
As for the wind, due to the lower ceilings the overall strength
of the wind hasn`t fully materialized due to the ceilings being
overall lower than what was initially expected. Taking Goodland
for instance, 30-40 knot winds occurred before 11am when the
ceiling was 1300-2000 feet, vs now with ceilings less than 1000
feet we struggling to gust to 30 knots. Still think the overall
favored for the strongest winds will be across Kit Carson and
Cheyenne counties where ceilings are around 1500 feet but have
more influence from the above mentioned jet aloft.
Moving into tonight, the temperature forecast is a little tricky
as it is dependent on how quickly the clouds can move out. Winds
will remain breezy around 15-20 knots sustained from the north
which should help moderate temperatures as a true source of CAA
isn`t really present. Went ahead and trended temperatures cooler
into the low 20s to low 30s but if the clouds can hang around
longer then warmer temperatures may occur.
Into Tomorrow, NW upper level flow will be present along with breezy
northerly winds in wake of the strong low pressure system that
will be over the eastern CONUS. Winds will not be as strong as
today but do think that 30-40 mph wind gusts will be common across
the entire area with the strongest favoring the east. Trended
temperatures down a little over the east as 850mb temperatures in
the 0-3 C range look to be present.
Wednesday currently appears to be by far the warmest day of the weak
as SW surface flow returns with a surface low develops in eastern
Colorado which will allow temperatures to warm into the 60s to
low 70s across the area. Winds do appear to be on the tamer side
around 10 to 15 mph as well. An overall pleasant day for any
traveling for the Thanksgiving holiday. The warmth will be short
lived however as another cold front moves through the area
Thanksgiving morning. Clouds will be on the increase through the
day along with breezy easterly winds. High temperatures in the 40s
are currently forecasted area wide for the holiday.
.LONG TERM...(Thursday night through Monday)
Issued at 1236 PM MST Mon Nov 20 2023
For the extended period, the latest run of the ECMWF looks to be
more of the favored trend in guidance at this time for the upcoming
system in the post-holiday timeframe compared to the latest GFS. The
GFS is a bit more progressive in pushing the system across the
Plains, while the ECMWF is a bit slower with the upper low lingering
longer over the CWA due to a blocking ridge over the eastern portion
of the country.
Uncertainty still remains to the track of this system as the last
couple runs pushed this system on more of a southeast track. It`s
current movement is similar to what was seen 2-3 days ago, a west to
east movement. With this change, the amount of snowfall the area
could receive shifts upward with more low level moisture expected on
an easterly upslope flow. The current range expected is 2 inches or
less along/east of Highway 83, and mainly 3-5 inches west. Highest
totals are focused in the NW section, especially in Yuma county.
Stay tuned as lack of consistency in model runs could have this
change in the next forecast.
The slower movement of this system will also delay the arrival of
precip from the NW to between 06z-12z Friday. This will taper in the
east on Saturday evening. Bulk of precip/snow will occur between 12z
Friday-00z Saturday. If the totals hold, Advisory level conditions
could be met.
What has been steady in several runs of the forecast will be the
arrival of colder air working into the region behind the exiting
low. 850mb temps drop a core -6C to -11C over the area. Have
continued close to guidance for lows and expected wind chill
readings that will accompany the overnight periods.
Dry conditions expected for Sunday and next Monday as the region
lies under NW flow aloft. A couple shortwaves will come close to
northern portions of the area, but nothing is expected.
For temps, looking for highs on Friday to range from the mid 20s
west into the lower to mid 30s east. This will be the colder period
for highs in the extended. For the upcoming weekend, 30s area-wide
on Saturday give way to upper 30s to mid 40s on Sunday. And for the
start of next week, mainly mid 40s for most locales.
As overnight lows start off mainly in the teens for Thursday night,
going into Friday and Saturday nights, the overnight periods will
drop into a range from the mid single numbers above zero west into
the mid teens east. By Sunday night, slightly warmer with mainly
lower to mid teens. Some spots west of Highway 27 into Colorado
could still see upper single numbers above zero. For next Monday
night, mid teens to around 20F.
Wind chill readings will continue to be impactful for the extended
period. Looking for readings Thu-Fri nights mainly in the single
numbers above/below zero. Worst conditions Saturday night with
mainly single numbers below zero. A few isolated locales west could
approach minus 10. Sunday night, back to a mix of single numbers
above/below zero.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 241 PM MST Mon Nov 20 2023
Rain is forecast to lessen in coverage as we head into the
evening. Any remaining rainfall looks to favor the KGLD terminal.
Winds will remain breezy overnight around 15-20 knots sustained
but any higher wind gusts should remain above the inversion as it
sets in; as a result LLWS will be present at each site. Ceilings
and visibilities will improve through the evening through the
overnight hours; however until then MVFR to occasionally IFR
conditions will remain. Breezy northerly winds will continue
Tuesday gusting 20-30 knots throughout the day but under clear
skies.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...Trigg
LONG TERM...JN
AVIATION...Trigg
Area Forecast Discussion
National Weather Service Houston/Galveston TX
455 PM CST Mon Nov 20 2023
...New AVIATION...
.SHORT TERM...
(This evening through Tuesday Night)
Issued at 345 PM CST Mon Nov 20 2023
We continue to keep our eyes closely on the radar this afternoon.
However, the bulk of the severe weather has been to our north and
east where UL diffluence has been strongest. The southeast Texas
atmosphere has not been lacking in shear. Effect bulk layer shear
has been an impressive 50 to 70 knots. RAP analysis indicate that
instability isn`t necessarily lacking either. But the window of
opportunity for severe weather is closing fast. The Tornado Watch
for our northeastern counties has been cancelled.
As these showers/storms exit the region, the primary focus will
shift to the approaching cold front. Winds will increase from the
northwest in the front`s wake tonight, possibly gusting near 30 MPH
at times (higher near the coast). In addition, much cooler
temperatures will filter southward into our region with lows falling
into the upper 40s in our northern counties and low/mid 50s
elsewhere. Conditions remain breezy and cool on Tuesday with
afternoon temperatures in the upper 50s to low 60s. Despite being
well behind the cold front on Tuesday, the combination of mid-level
Pacific moisture as well moisture wrapping around a low-pressure
system in the midwest is expected to delay our sunshine. Our current
sky grids show an eventual gradual clearing by late afternoon and
evening.
Self
&&
.LONG TERM...
(Wednesday through next Sunday)
Issued at 345 PM CST Mon Nov 20 2023
CAA will continue to prevail going into Wednesday with surface high
pressure nearby. Although, Wednesday is trending a bit cooler due to
increasing cloud cover ahead of an approaching upper level low
moving in from northern Mexico. Not too much cooler, but enough to
where we can say highs are expected to be mainly in the upper 50s
rather than the low 60s now. This upper level low forms from
shortwave energy that pinches off from the upper level low that
aided in pushing in Monday`s cold front. The trough with the
embedded low then pushes southeastward going into Wednesday before
the flow aloft allows it to track northeastward across Southeast
Texas on Thanksgiving Day. There still remains a bit of uncertainty
as far rain goes on Thanksgiving, so I`m still going to allow that
to have it`s own paragraph. I should note here though that although
NBM trended back cooler for Wednesday night, I kept temperatures a
few degrees warmer due to the increasing cloud cover. Alright...now
let`s make like turkey and wobble on to the Thanksgiving forecast!
If you don`t want to read through the technical/nerdy stuff that
follows, then here`s a quick summary for you (and you can skip to
the next paragraph afterwards): light rain is expected on
Thanksgiving morning into the afternoon and tapers off in the mid to
late afternoon, but the overcast clouds will lead to cooler daytime
temperatures in the mid to upper 50s. Now onto the cool stuff! As
the upper level trough (with embedded cutoff low) moves into
Southeast Texas on Thursday, it`ll become negatively tilted.
Saying "negative tilt" may get some heads to turn, but nothing
severe will occur...in fact there won`t be any storms at all with
effectively zero instability. Additionally, PW values have trended
a bit drier with values now expected to peak at 0.8"-1.0" south
of I-10 on Thursday (75th percentile: ~1.27"). Model soundings
reveal that there`s also drier air at the surface to contend with
from the surface to 2 km, so the saturation is mainly at the
mid/upper levels. On top of that, the timing/progression of this
low will play a key factor due to the jet streak on its
southeastern flank. We`ll start out in a region of upper level
divergence/diffluence (left exit region) followed by a quick shift
to a region of upper level convergence/confluence (left entrance
region). Think of it like a clap on/clap off situation for
favorable upper level dynamics. And then on top of that, there`s
still some uncertainty in the exact track of the upper low as a
southern track (off the coast) like the NAM/GFS suggest would keep
us drier. So...it`s not entirely surprising that ensemble members
are a bit wishy-washy and seem to be the equivalent of asking a
wishbone if it`s going to rain and breaking it apart. All that
being said, there are enough ensemble members showing light rain
that I kept in the 20-30% PoPs for Thanksgiving...but no heavy
rain is expected, so outdoor plans shouldn`t be impacted other
than the grounds being a little damp.
As far as temperatures go, the overcast clouds will keep
temperatures in the mid to the upper 50s throughout the day.
Thanksgiving night will be on the chilly side with lows ranging from
the upper 30s to mid 40s. Past that, we`re still eyeing the next
cold front some time next weekend with another upper level trough
swinging through the Four Corners region. Originally, the timing
looked to be on Saturday, but now things have transitioned to more
of a Sunday timeframe. Either way, rain chances increase going into
the weekend with PW values climbing into the 1.3"-1.6" range.
Temperatures look to remain cool throughout and past the long term
period with NBM upper quartiles for maximum temperatures remaining
well below 70°F into next week. So, it`s entirely possible that we
could stay below 70°F through the end of the month...and if not then
you know who jinxed it. ¯\_(ツ)_/¯
Batiste
&&
.AVIATION...
(00Z TAF Issuance)
Issued at 444 PM CST Mon Nov 20 2023
The majority of the showers and thunderstorms have ended with the
front now moving through the area. The northwesterly wind shift
will occur shortly at CLL and UTS, and then in the next few hours
at CXO. The front will slide through IAH around 3z, SGR/HOU
around 4z, and then to LBX/GLS by 5 to 6z. The winds will become
strong behind the front with sustained winds expect around 15kts
and gusts to 25kts, which will continue through tomorrow afternoon
or evening. VFR conditions will prevail, but there may be some
MVFR CIGs at around 2500-3000ft coming down from the north late
tomorrow morning into the afternoon for CLL, UTS, and maybe CXO.
Fowler
&&
.MARINE...
Issued at 345 PM CST Mon Nov 20 2023
Light to occasionally moderate onshore flow continues to prevail
with caution flags raised for the farshore waters through this
afternoon as well. This is ahead of an approaching cold front that
will push through during the evening hours with showers/storms
possible ahead of and along the frontal boundary. In the wake of the
front, elevated seas reaching 7-9 feet and moderate to strong
northerly/northwesterly winds will prevail through Tuesday night
with gale force gusts possible at times. The window for gale force
gusts looks to be roughly between 4am-12pm Tuesday. A Small Craft
Advisory will go into effect tonight and will likely need to remain
in place through early Wednesday morning. Winds and seas gradually
subside on Wednesday with offshore flow prevailing through late
Thursday. Rain chances return again on Wednesday night/Thursday as
an upper level disturbance pushes through. Winds transition to a
northeasterly flow going into Thursday night/Friday and into the
weekend.
Batiste
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 50 61 41 58 / 10 0 0 0
Houston (IAH) 52 61 45 58 / 10 0 0 0
Galveston (GLS) 55 63 50 59 / 0 0 10 10
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...High Rip Current Risk until 7 PM CST this evening for TXZ436>439.
GM...Small Craft Advisory from midnight tonight to midnight CST
Tuesday night for GMZ330-335.
Small Craft Advisory from midnight tonight to 6 AM CST Wednesday
for GMZ350-355-370-375.
&&
$$
SHORT TERM...Self
LONG TERM....Batiste
AVIATION...Fowler
MARINE...Batiste
Area Forecast Discussion
National Weather Service North Platte NE
605 PM CST Mon Nov 20 2023
.KEY MESSAGES...
- Chances for significant snowfall across wrn Nebraska have
increased 40 to 70 percent across parts of western Nebraska.
- Subfreezing high temperatures are predicted Friday and
Saturday.
- Highs in the 60s are predicted Wednesday.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 258 PM CST Mon Nov 20 2023
Satellite indicates a developing clearing line across northwest
Nebraska and this will move quickly southeast this afternoon and
this evening. Clear skies should be widespread by late evening. Just
an isolated POP is in place ahead of the clearing and the POP
forecast uses the short term model blend plus a dose of the HREF.
The are no other rain chances between now and Wednesday.
The temperature forecast tonight uses the short term model blend
plus bias correction for lows in the 20s. Winds should stay up east
of highway 61 but there is a chance winds could decouple for a few
hours across the northwest. It is in this area, lows in the teens
may develop.
The temperature forecast Tuesday and Tuesday night uses the guidance
blend and lows Tuesday night may well need to be marked down toward
the NBM 50th percentile or lower. It is worth noting warm air
advection will be underway which could impact the radiational
cooling underway.
The model consensus shows the leading edge of cooler air arriving in
nrn Nebraska around 21z Wednesday afternoon. H850mb temperatures
around 12C will easily support highs in the mid to upper 60s ahead
of the front. Some of the guidance suggests highs reaching 70 and
this may be the best forecast given the RAP high cloud procedure
shows nearly full sun conditions. The forecast for highs mostly in
the lower 60s is 3-5 degrees lower than the NBM 90th percentile and
later forecasts can mark up temperatures if warranted.
&&
.LONG TERM /TUESDAY THROUGH MONDAY/...
Issued at 258 PM CST Mon Nov 20 2023
Cold air will pour into western and north central Nebraska
Wednesday night and continue during the day Thursday. By
Thursday evening h850mb temperatures will have fallen 15C to
around -5C.
The deterministic GFS and ECM/ECM ENS have perked up on snow chances
Friday. The GFS ENS and CMC ENS are holding steady for this run
suggesting just light amounts. There is little change in the
moisture and basic thermodynamics but the upper level low and
associated dynamics are lifting out slower. In fact, the ECM shows
accumulating snow still underway Saturday morning.
Another reason for increased snow chances could be the GFS shows the
arctic air mass shallow with the inversion top at just h850mb.
Earlier GFS model runs showed a shallow wedge of dry air holding
back snow growth processes. That concept has faded today.
The GFS ENS shows a 50 to 70 percent chance of over an inch of snow
across wrn Nebraska. The ECM ENS shows this figure increasing to
near 100 percent and the 3 inch snow probability is 50 to 70
percent. The CMC ENS is like the ECM ENS for the 1 inch but very low
like the GFS ENS for the 3 inch.
As advertised by the deep layered moisture in the models and very
favorable thermodynamic profiles, all that will be need for
significant snow is lift-over-time and the models today are
suggesting this will occur. POPs across wrn Nebraska for this
forecast are 50-70 percent. Lower chances are in place to the east.
The blended forecast suggests snow chances across wrn Nebraska are
70 percent or greater for 1 inch of snow and 30 to 60 percent for 3
inches.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 605 PM CST Mon Nov 20 2023
MVFR ceilings at KLBF will improve back to VFR by 02Z. Northerly
winds near 34015G25KT will continue tonight through 21Z
Tuesday, then diminish. LLWS concerns at KLBF, mainly from 11z
to 15Z Tuesday.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Roberg
Area Forecast Discussion
National Weather Service Louisville KY
915 PM EST Mon Nov 20 2023
.Forecast Update...
Issued at 915 PM EST Mon Nov 20 2023
Currently, mostly cloudy skies were noted across the area with
regional radars showed widespread rain showers mainly west of I-65.
Temperatures across the area were in the upper 40s to lower 50s west
of I-65 and north of the BG Parkway. Across south central KY,
stronger warm advection was pushing temperatures into the upper 50s
and lower 60s.
Overnight, the low-level jet axis will surge northward into central
KY and align itself along and east of I-65. Strong moisture
advection along with significant synoptic scale lift due to the
region being in the exit region of the upper level jet will result
in widespread rain showers. As mentioned earlier, PWAT values are
still forecast to get into the 1.25-1.40 inch range overnight and
pockets of moderate to heavy rainfall will be possible, especially
along and east of a line from BWG to LEX. Low-level jet axis
continues to push northward into the region and we`ll see it max out
in the 60-65kt range overnight. Shear values are quite impressive
across the area, but a look at model soundings shows very little, if
any, instability. Still can`t rule out a rumble of thunder or two
especially across our SE in the Lake Cumberland area. As far as
rainfall amounts, a solid 0.75 to 1.25 inches of rainfall with some
locally higher amounts will be possible.
In addition to the rain overnight, we`ll see surface winds gradually
pick up due to the pressure gradient increasing. While we`ll have a
screaming LLJ overhead, model soundings from the high resolution
models really show a stout temperature inversion setting up
overnight which will keep those higher winds from mixing down to the
surface. While gusts of 15-20 mph will be possible in most areas,
any stronger shower may be able to mix down some higher winds, so a
few gusts of 30-35 mph can`t be ruled out. The best chances of that
though look to be confined to our SE areas down near Lake Cumberland.
With all that said, the current forecast remains in good shape
overnight. Have made just a few minor adjustments to the grids here
and there to bring them in alignment with current observations.
&&
.Short Term...(This evening through Tuesday)
Issued at 321 PM EST Mon Nov 20 2023
===================================================================
Key Messages
* Widespread soaking rain - Tonight
* Gusty - Tonight
===================================================================
Currently, a large upper trough dips south through the western
states, turns east through northern Mexico, and then shoots
northeast towards the Ohio Valley. Within the trough a 500mb closed
low sits over eastern Kansas. To the south, the system`s surface low
is sliding east across southern Oklahoma, and by early tonight, the
low will near the southern Mississippi River Valley.
Through the rest of the day, mid-level clouds will continue to get
pushed across central Kentucky and southern Indiana ahead of the low
pressure system. Lower stratus is developing and will continue to
fill in as a Gulf of Mexico moisture feed continues to strengthen on
850mb and surface winds, as they continue veering towards the south
from the the approaching low. A few sprinkles or light showers will
remain possible, but most areas will remain dry across the CWA until
later this evening.
Tonight, a jet streak along the front edge of the aforementioned
upper trough will begin moving from the Mississippi River Valley
into the Lower Ohio River Valley. This will place the CWA in the
exit region of the jet. A low level jet response will develop and
strengthen as it moves east over the CWA tonight. On the
conservative side, the HREF has this LLJ reaching between 60-70
knots while the HRRR and some others have it reaching 70-80 knots.
This is making for some huge low level SRH values, but the lack of
instability should limit severe weather potential. There will be the
added possibility for a thunderstorm or two across south central
Kentucky. This will be worth monitoring. Precipitable water value
trends have increased from near one inch showing in the models
yesterday to 1.25-1.40" today, so decent rainfall will be expected
at times during the overnight hours, which is when most of the
rainfall in the area will fall. Winds will increase to around 10-15
mph as they veer from the east to south. Gusts can be expected to
reach between 20-30 mph. Those near Clinton County could see gusts
reach a little higher for an hour or two as the system passes. Low
temperatures are expected to drop into the upper 40s to low 50s.
Tomorrow, the bulk of the main rain will come to an end around mid-
day as the surface low reaches northern Indiana, and its trailing
cold front moves east of the area. With low stratus remaining
through the day light rain/drizzle chances will remain through the
day, and a few light showers could develop on the backside of the
low. These showers would pass through the CWA during the afternoon
and evening hours. Overall rainfall totals are expected to reach
between 0.7-1.5", but with the LLJ being so strong and the increased
moisture, believe totals could overachieve. Some areas could maybe
see 2". High temperatures will reach into the upper 50s to low 60s
as winds veer from the south to the west. The gusty conditions will
remain with winds between 10-20 mph most of the day.
.Long Term...(Tuesday night through Monday)
Issued at 255 PM EST Tue Nov 20 2023
====================================================================
Key Messages
* Dry Thanksgiving Day
* Low confidence in timing of light precip chances Fri, and again
Sun-Mon
====================================================================
Tuesday Night - Wednesday...
The upper trough axis and surface cold front will be pushed through
our region by Tuesday night, effectively shutting off the deepest
moisture over our area. However, it does appear that a good bit of
moisture will remain trapped in 1000-850mb layer and will likely be
sufficient enough to produce some lingering very light rain or
drizzle through at least the first half of Wednesday, if not into
the entire day across our eastern CWA. Will keep measurable rain
chances through Tuesday night, tapering W to E on Wednesday.
Lows on Tuesday night should drop into the upper 30s to around 40
for most folks. Highs on Wednesday should struggle under heavy cloud
cover and a steady cool advection component. As a result, only
expecting mid to upper 40s for highs, a fairly tight diurnal range.
Wednesday Night - Saturday Night...
Look for a dry stretch of weather through mid week as a quiet zonal
pattern aloft takes hold, in addition to high pressure in control at
the surface. Expect skies to clear for Wednesday night which will
allow for chilly overnight lows down around freezing. Temps recover
nicely on Thanksgiving as plenty of sunshine results in a higher
diurnal range. Looking for low to mid 50s with plenty of sunshine.
We`ll keep some small pops in for Thursday night into Friday as a
weak closed low over northern Mexico ejects out as an open wave to
our south. Ensembles are likely just a little uncertain on
timing/placement of this feature, which is why a small chance is
lingering for this time frame. Ultimately expect this to be a dry
period, but will wait until the fine details resolve themselves
before removing those pops. Saturday looks dry with temps in the
upper 40s and low 50s.
Sunday - Monday...
More uncertainty creeps into the upper pattern to end the weekend
and start the new work week. A shortwave looks to eject out of the
western CONUS by this time, just ahead of deeper troughing
enveloping central Canada. Will keep some broad pops in mostly for
Sunday, but perhaps could linger into Monday given timing
uncertainty. Highs should continue in the upper 40s and low 50s.
&&
.Aviation...(00Z TAF Issuance)
Issued at 622 PM EST Mon Nov 20 2023
In the short term, VFR conditions are expected at the terminals
through around 21/5-6Z. Light rain showers will move into the
western terminals (HNB/BWG/SDF) in the 21/2-3Z time frame and then
into LEX after 21/5Z. Cigs will then lower to MVFR along with vsbys
due rain showers. Rainfall is expected to become heavier later
tonight and some tempo drops in cigs/vsbys are possible within the
heavier showers. A strong low-level jet will move over the region
and we plan on keeping LLWS in at BWG/LEX overnight. As the surface
low pressure center pulls aways from the region late Wed morning,
we`ll see showers diminish rather quickly from SW to NE. Cigs will
likely remain low MVFR through the end of the period as a return to
VFR will likely occur outside of the upcoming TAF period.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update.......MJ
Short Term...KDW
Long Term....BJS
Aviation.....MJ
Area Forecast Discussion
National Weather Service Marquette MI
627 PM EST Mon Nov 20 2023
.SHORT TERM...(Through Tonight)
Issued at 223 PM EST MON NOV 20 2023
Key Messages:
-Quiet and dry weather continues through tonight.
RAP analysis shows a mid level closed low over Kansas that is
between a ridge over the west coast and a westward tilted ridge
over the Great Lakes Basin. A trough to our northwest is also
analyzed, centered between Saskatchewan and Manitoba. Sfc high
pressure centered over Southern Ontario also extends over our CWA,
yielding light south to southeast winds. Moisture advection off
Lake Michigan and orographic lift supported some isolated low
level clouds into the early afternoon over south central Upper
Michigan, but overall high level clouds have been pushing in
gradually today with more sunshine over the east. With gradually
increasing cloud cover, temps may increase an additional degree or
two with highs expected in the upper 30s to mid 40s.
The mid level trough to our northwest will dig southeast through
Manitoba this evening and tonight, reaching northwestern Ontario by
Tuesday morning. Meanwhile the closed low over the plains will lift
northeast toward the southern end of Lake Michigan by Tuesday
morning, where shortly after these will phase together over Lower
Michigan outside the short term forecast period. The cold front
associated with the low to our north and the lift from the
subtropical low currently over Oklahoma are expected to stay outside
our CWA until Tuesday, leaving us quiet and dry through tonight.
Increasing cloud cover will help insulate temps in around 30; warmer
by the lakeshores.
.LONG TERM...(Tuesday through Monday)
Issued at 429 PM EST MON NOV 20 2023
Key Messages:
- A period of light rain/snow over the eastern fcst area on Tue.
- Occasional w to nw flow LES expected late Wed night through
early next week, but dryness of the air mass over most of that
time frame will keep snow accumulations on the light side.
- Trend to below normal temps Thu/Fri, then to around normal over
the weekend.
Medium range models depict a split flow regime into the weekend with
the northern stream becoming increasingly dominant for Upper MI
weather. Flow may tend to become more consolidated for a time
heading into early next week. Mid-level ridging/positive height
anomalies developing over the ne Pacific with axis then running n
vcnty of the w coast of Canada thru AK during the last half of this
week will force troffing into eastern Canada with negative height
anomaly over time setting up around Hudson Bay. For Upper MI, this
evolution of the flow will lead to temps initially above normal
trending to a mix of normal and blo normal, beginning Thu and
continuing into early next week, coldest Thu/Fri. Some degree of
ridging will persist near the W Coast next week, so temps should be
on the cold side of normal more often than the warm side next week
as we round out the month of Nov. Any of the colder days will
certainly be nothing out of the ordinary for this time of year. As
for pcpn, a southern stream wave will venture far enough n to bring
some light rain/snow to the eastern fcst area on Tue with a passing
northern stream wave bringing a few -shrasn to much of the rest of
the area. Otherwise, the current split flow regime will be a dry one
for Upper MI, outside of light LES later this week that will
struggle under incoming dry air. Over the weekend into early next
week, the northern stream will become a little more active, at least
providing some opportunities of lake enhanced snowfall. At this
point, there is nothing on the horizon indicating any potential of
significant snowfall thru next week. So, it will be a slow start to
establishing winter snow cover in Upper MI.
Beginning Tue/Tue night, a northern stream shortwave will extend
from western Hudson Bay to MN while the southern stream wave
currently over the Southern Plains will have lifted into the Lower
Ohio Valley. Models are now in good agreement suggesting that pcpn
with the southern stream wave may reach as far nw as a line from
roughly Menominee to Grand Marais Tue aftn to early evening. Wetbulb
zero heights indicate a mix of rain and snow, but the NAM/GFS are
supportive of a more predominant snow ptype. In the end, with sfc
temps running at least a couple of degrees above freezing and qpf no
more than around 0.1 inch at most, snow accumulations will be
minimal, if any. No snowy/icy roads are expected. To the w, northern
stream wave will be accompanied by isold/sct -shrasn arriving w mid
to late aftn and spreading e thru the evening. Fcst soundings
indicate moisture depth will diminish as the northern stream wave
sweeps across the area, which is supported by the notable weakening
of the wave with time. As a result, ice nucleation appears to become
less likely moving e across the fcst area as moisture depth falls to
below the -10C isotherm. So ptype may become more -dz with time
instead of -shsnra. WAA gets underway a short time after the wave
passage, so no lake effect pcpn is expected. As it is, 850mb temps
only drop to about -6C at lowest, marginal at best for any lake
effect anyway.
The waa is a result of the next shortwave streaking from the
Canadian Rockies to northern Ontario by Wed evening. Associated cold
front will reach Upper MI Wed evening. Ahead of the front, expect
highs in the upper 30s to mid 40s F on Wed.
Fropa will be dry given the lack of moisture. Following caa will
drop 850mb temps down to -10 to -13C by sunrise on Thanksgiving Day
with further cooling down to around -16C by evening, plenty low
enough for nw flow LES by morning given water temps averaging around
6C. However, incoming very dry air mass will be a strong negative
along with large scale low-level flow trending anticyclonic. With
the dry air mass, fcst soundings show a fairly pronounced well-mixed
layer/inverted-v below cloud deck. Where fetch is longest into the
eastern fcst area, this well-mixed layer diminishes. The DGZ does
dominate the cloud deck, but that`s all that`s going for the LES.
Expect only flurries/isold -shsn into the western fcst area,
especially a bit farther inland into the interior where the
upsloping gives a further upward motion boost. Over the e, Alger
County eastward, expect sct -shsn. Snow accumulations will be
minimal, inch or less. It will be a chilly day with blustery nw
winds 20-30mph and falling temps. Early highs will be in the upper
20s nw to mid 30s F se. Mid to late aftn temps will range thru the
20s.
Air flowing across Lake Superior remains very dry Thu night/Fri as
low-level flow backs more westerly, shifting light LES closer to
shore over the e during Fri. Flurries/isolated -shsn will continue
into nw Upper MI under the shift to westerly flow. A shortwave
swinging across northern Ontario and brushing Lake Superior may
briefly increase LES Thu night/Fri morning as inversion bumps up
slightly. However, the main negative of dry air continues. Highs
Fri will be in the mid 20s to around 30F.
Moderation occurs on Sat ahead of the next shortwave dropping se
into s central Canada. A southern stream wave will also be pushing
out over the western Plains. With winds backing wsw in addition to
the warming, expect any light LES to end.
At some point Sun/Mon, passage of the shortwave will bring a period
of lake enhancement along with potential area-wide -sn for a short
time as it passes, especially if the southern stream wave can become
involved. At a minimum, models have overall shown a bit better LES
setup with deeper moisture involved this go around.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 626 PM EST MON NOV 20 2023
High clouds tied to a system approaching the Lower Great Lakes
tonight will slowly diminish Tuesday as a cold front pushes into the
region from west to east. Expecting VFR conditions at KCMX and KIWD
to lower to MVFR by afternoon. KSAW will also lower, but likely
remain VFR in this period. Some light precip in the form of rain
and/or snow will be possible along and after the front passes.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 429 PM EST MON NOV 20 2023
With high pres to the e and a cold front approaching from the w,
expect southerly winds across Lake Superior tonight, generally
gusting to 15-20kt, though some gusts to 25kt will occur across the
e. The cold front will then sweep across Lake Superior during Tue
and Tue evening, but it will be weakening. While winds across the e
half of Lake Superior ahead of the front will diminish to under 15kt
on Tue, expect a shift to 20-30kt nnw winds behind the front across
the w. Winds will shift to nw gusting to 25kt across the e half Tue
night, but will diminish to under 20kt w as a high pres ridge
arrives. That ridge will quickly shift e on Wed ahead of the next
cold front. In response, sw winds will ramp up across the w half of
Lake Superior on Wed, gusting to 25-30kt by aftn. Winds should
remain mostly under 20kt e half. The cold front will sweep across
Lake Superior Wed night, bringing a wind shift to nw winds to 30kt
that will continue thru Thu into early Fri. Given the increasingly
colder air flowing across the lake that will increase instability
and thus mixing to stronger winds aloft, gale potential will also
increase. Currently, there is a 40-50pct chance of low end gales
across the e half of Lake Superior on Thu. Winds will only diminish
a little Fri into Sat. Expect 20-30kt winds to prevail both days.
Winds may ramp up later Sat, depending on timing of next cold front
approaching from the nw.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Jablonski
LONG TERM...Rolfson
AVIATION...JTP
MARINE...Rolfson
Area Forecast Discussion
National Weather Service Morristown TN
845 PM EST Mon Nov 20 2023
...New UPDATE...
.UPDATE...
Issued at 837 PM EST Mon Nov 20 2023
Forecast mostly on track but a few updates this evening. Based on
latest HRRR trends, slowed down precip arrival by a few hours
areawide. Also, slightly lowered QPF amounts across the east TN
mountains and foothills during the overnight hours. Winds will
continue to ramp up through the night with the strongest winds not
expected until around daybreak Tuesday morning. During this time
the fire weather concerns will remain extremely high. Also,
slight adjustments to hourly temps and dewpoints. Temps were too
cool as winds are keeping temps warmer and dewpoints were too
high. Will send new zones.
&&
.SHORT TERM...
(This evening through Tuesday)
Issued at 321 PM EST Mon Nov 20 2023
Key Messages:
1. High winds expected over the E TN mountains/foothills, and strong
gusty winds also expected over SW NC, Plateau, and SW VA.
2. Dangerous fire weather conditions this evening and overnight into
Tuesday morning especially in the foothills and mountains ahead
of the rain.
3. Most confident in significant beneficial rainfall from
Chattanooga and the Plateau counties north to southwestern Virginia.
Least confident in rainfall in the East TN foothills of the Smoky
Mountains.
Discussion:
A very dangerous next 24 hours is upon us. The well discussed
shortwave will be moving to the Ohio River and onwards through
Tuesday. High resolution guidance is painting very strong H85 flow,
and as a result peak sustained winds 40 to 50 knots are in the
forecast in the lee-side mountains. Gusts upwards of 70-80 mph in
the mountains, and gusts of 40 to 45 mph in the Plateau and
ridges of the Sequatchie Valley overnight are possible. Given the
extreme drought we find ourselves in, these winds will pose not
only a major threat to ongoing fires, but also fire potential from
any wind damage that occurs. The most dangerous time is overnight
tonight into Tuesday morning, with a several hour gap between the
arrival of decent rains and the strongest winds flowing across the
mountains. As a note, the hazards are nearly entirely confined to
the elevated portions of East TN, along with our NC and VA
counties. The valley between the plateau and mountains will have
breezy winds overnight, but expected to remain below advisory
criteria and will not have the same degree of fire danger.
There is high confidence in a line of moderate to heavy rainfall
entering the Plateau counties around daybreak, with the potential
for lighter showers out ahead before then. This line will steadily
march eastward across the state. Rainfall along the Plateau as far
east as Knoxville metro and along a parallel north and south is
still expected to be around an inch, with higher amounts possible
closer to the Plateau.
Of significant concern and continued uncertainty is when exactly
rainfall arrives in the foothills of the Smoky Mountains. 18z runs
of the HRRR and NAM have continued with a pessimistic outlook on
rainfall in the lee-side shadow of the mountains. Due to the high
downslope winds, a rain shadow is evident in guidance and is
expected, although to what degree is the uncertain bit. Decreased
rainfall slightly to four-tenths of an inch across central Sevier
and Cocke counties to move closer to CAM guidance. Tops of the
mountains should still receive decent beneficial rainfall. Arrival
of the heavier main rain band looks to be around noon, though
scattered rain showers are possible beginning around daybreak for
the mountains. Backside of the bulk of the rain looks to be
exiting the state by Tuesday evening, though will maintain some
PoPs at the end of the period.
&&
.LONG TERM...
(Tuesday night through next Monday)
Issued at 321 PM EST Mon Nov 20 2023
Key Messages:
1. Rain decreases Tuesday night with a few light showers Wednesday.
2. Cooler temperatures expected through Thanksgiving and into the
weekend, with a round of light rain possible Friday heading into the
weekend.
3. A weak system will affect the area Sunday night into Monday but
again only light to little additional rainfall expected.
Discussion:
By Tuesday night into early Wednesday the front moves east of the
Appalachian mountains and the steady precipitation comes to an end
from west to east throughout overnight across most of the eastern
Tennessee Valley. The surface low will be far to the north over the
eastern Great Lakes by early Wednesday but models show some wrap
around moisture will stick around across the northern and eastern
sections of the forecast area through the day Wednesday. The highest
elevations of the eastern Tennessee Mountains should be cold enough
for some brief snow Wednesday with no accumulations expected. Highs
Wednesday will be slightly below normal in the upper 40s to lower
50s with higher elevations in the upper 30s to lower 40s. This
should be the coldest day through the weekend. Skies will be
clearing Wednesday night and then Thursday temperatures will be
slightly warmer with more sunshine and high pressure building over
the southeast states.
Thanksgiving night through Friday evening a low pressure system
along the Gulf coast will weaken as it moves east. Some light rain
will spread into the Tennessee Valley but rainfall amounts
unfortunately will be very low and have not included any QPF. The
latest long range models have kept the significant precipitation to
the south of Tennessee. Upper flow is more west to east Saturday and
Sunday. On Sunday another upper trough digs south into the northern
plains and eastern Great Lakes. A weak surface low over the northern
Gulf and associated frontal system moving across the western
Tennessee and Ohio Valleys weakens as it moves east overnight. There
will be a few showers over the eastern Tennessee Valley Sunday night
or early Monday but rainfall amounts again look light. The system
looks like it is splitting too with the better precipitation
coverage to the north. With the mostly zonal flow after Thanksgiving
temperatures will be near average with highs in the 50s and lows in
the 30s and 40s.
&&
.AVIATION...
(00Z TAFS)
Issued at 631 PM EST Mon Nov 20 2023
VFR conditions at CHA until midnight. Then, MVFR Cigs will be in
place through late morning, then dropping to IFR. MVFR returns
late in the period. Southeast winds will gust from 20 to 25 kts
until early morning. LLWS in place at TYS to begin the period.
LLWS drops off early tomorrow morning as surface winds increase.
VFR conditions in place, due to the downsloping winds off the east
TN mountains, through most of the period. Then, MVFR late in the
period. Southeast wind gusts to 20 kts by early tomorrow morning,
transitioning to southerly winds by late morning. VFR at TRI
until tomorrow morning due to downsloping winds. MVFR conditions
late in the period. Calmer winds expected at all sites toward the
end of the period.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 55 67 48 54 / 90 90 10 10
Knoxville McGhee Tyson Airport, TN 54 66 47 53 / 60 100 30 20
Oak Ridge, TN 52 64 46 53 / 80 90 20 20
Tri Cities Airport, TN 48 60 46 51 / 50 100 60 40
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...Red Flag Warning until 7 AM EST Tuesday for Cherokee-Clay.
Wind Advisory until 4 PM EST Tuesday for Cherokee-Clay.
TN...Red Flag Warning until 7 AM EST Tuesday for Blount Smoky
Mountains-Cocke Smoky Mountains-East Polk-Johnson-Sevier
Smoky Mountains-Southeast Carter-Southeast Greene-Southeast
Monroe-Unicoi.
Wind Advisory until 4 PM EST Tuesday for East Polk.
Wind Advisory until 10 AM EST Tuesday for Campbell-Morgan-Scott
TN.
High Wind Warning until 4 PM EST Tuesday for Blount Smoky
Mountains-Cocke Smoky Mountains-Johnson-Sevier Smoky
Mountains-Southeast Carter-Southeast Greene-Southeast
Monroe-Unicoi.
Wind Advisory until 6 AM CST Tuesday for Bledsoe-Marion-
Sequatchie.
VA...Wind Advisory until 4 PM EST Tuesday for Lee-Russell-Washington
VA-Wise.
&&
$$
SHORT TERM...
LONG TERM....TD
AVIATION...