Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/22/23
AREA FORECAST DISCUSSION
National Weather Service Albany NY
1045 PM EST Tue Nov 21 2023
.SYNOPSIS...
Clouds will thicken and lower through the day with gusty
southerly winds developing by afternoon. A storm system will bring
snow and a wintry mix to the region for this evening, which will be
changing over to plain rain during the overnight and early morning
hours on Wednesday, with a light accumulation of snow and ice
expected for northern and high terrain areas. Precipitation will
taper off on Wednesday, although it will remain chilly and breezy
through the day. Cool and mainly dry weather is expected for
Thanksgiving into the holiday weekend.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
...Winter Weather Advisory expanded...it is in effect until 10
AM for the southern Adirondacks, Lake George Saratoga Region,
northern Taconics, southern Vermont and northern Berkshires...
Quite a variety of precipitation types and accumulations over
short distances this evening. Snow in the southern Adirondacks
to Lake George with around 2 inches of snow, and near 4 inches
in parts of the southern Adirondacks. Snow of 1 to 2 inches from
the Capital Region to Saratoga Region, and northern Taconics. A
coating of sleet and freezing rain in the western and central
Mohawk Valley, Schoharie Valley, Helderbergs and eastern
Catskills. Sleet changing to rain east of the Hudson Valley with
an occasional mix with snow. Rain in the mid Hudson Valley to
NW CT, and an inch or two of snow in southern VT and Berkshires.
The 00Z soundings from KALB and KBUF show some of why areas west
of the Hudson Valley had more sleet and freezing rain, beginning
the transition to a cold rain. Strong low level convergence at
the nose of a boundary layer jet maximum supported lots of
moisture advection and upward motion, resulting in lots of
precipitation and wet bulbing and diabatic cooling for snow
around the Capital Region to southern Adirondacks.
NY Mesonet temperatures showing warming from the south as
surface winds from the southeast spread the warming temperatures
north through the rest of the night. NY Mesonet profilers show
warm advection veering from the surface through the boundary
layer. The coating of snow, sleet and freezing rain may slow the
warming but there will be warming through the night and the
precipitation transition will be complex and will vary based on
elevation and location as the warm air aloft changes
precipitation to rain aloft and surface temperature warming will
again, vary by location and elevation.
Advisories remain in effect and issuing Special Weather
Statements where sub advisory but nuisance snow and mixed
precipitation occur. Thanks to everyone who have provided snow,
sleet and freezing rain reports.
PREVIOUS DISCUSSION:
The surge of isentropic lift ahead of an inverted trough
associated with a complex storm system moving into the lower
Great Lakes Region with a secondary low moving into the
Piedmont/Mid Atlantic Region is impacting the forecast area. The
mid and upper level ridge axis has moved downstream over the
Gulf of Maine and Nova Scotia with strong southwesterly flow
aloft ahead the positively tilted mid and upper level trough.
The PWAT anomalies will surge a couple of standard deviations
above normal based on the NAEFS with +V anomalies at H850 to +2
to +3 or STDEVs above normal. The moisture transport from the
Gulf will be advected into the region for about a half an inch
to an inch and a quarter of QPF. The ptype continues to be a
challenge with snow/sleet and even some freezing rain with the
onset. We have seen this trend upstream over central NY and
eastward into the Schoharie Valley, eastern Catskills, western
Adirondacks and the west-central Mohawk Valley. We have added
northern Fulton Co. to the Winter Wx Advisory with the southern
Dacks where 2-5" of snow is possible with some light icing.
Further south, the icing should be brief based on the 3-km HRRR
/ NAM sounding profiles and we have issued an SPS for the west-
central Mohawk Valley, northern and eastern Catskills and
Helderbergs with 1-3" of snow and sleet. Further east, the
Capital District and the north-central Taconics may getting a
coating to an inch of snow...especially the grassy surfaces
before turning quickly to rain early tonight. The southern
Berkshires and Litchfield Hills may get a half an inch to inch
or so of snow. The mid Hudson Valley and southern Litchfield
corridor will have mostly rain.
Further northeast, the dynamic or wet bulb cooling combined with
the favored east/southeast upslope flow off the eastern
Adirondacks, and southern Greens may allow for 3-5" of snow and
sleet with light freezing rain overnight. Would not be surprised
if isolated higher terrain areas of northern Saratoga Co. get
2-5" of snow. Near the Lake George Village/Queensbury and KGFL
expect 2-4" which will be the most this year for those areas!
The column gradually warms towards daybreak, as the dry slot
surges across the region. A secondary low forms south of Long
Island but its impacts look limited for the CWA towards sun
rise with the pcpn starting to taper. Lows will be in the mid
20s to mid 30s early tonight and then slowly rise. Expect south
to southeast winds 10-20 mph with some gusts 30-45 mph over the
Taconics, southern Adirondacks and western New England higher
terrain.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/...
Tomorrow...We have kept the advisories going until 10 am for the
southern Dacks, southern Greens and northern Berks in case any
spotty freezing rain persists. However, these may need to be
canceled early. The winds will swing around to the
north/northwest at 10-15 mph with some isolated to scattered
rain and upslope snow showers for the southern Greens and
western Dacks with little additional accums for the afternoon.
Highs will be in the mid 30s to lower 40s north of I-90, and
mainly 40s to lower 50s to the south. The secondary wave scoots
east/northeast of Cape Cod early Wed night.
The mid/upper trough axis lingers with some light snow/rain
showers and weak cold advection moving into the region. It will
be partly to mostly cloudy and cold with lows in the mid 20s to
to mid 30s.
Thanksgiving has weak ridging build in early with the mid level
flow shifting zonal over the region by the afternoon. It will
become partly sunny with temps rising fairly close to normal for
the holiday with west winds 10-20 mph. Highs will be in the mid
30s to lower 40s over the higher terrain and lower 40s to lower
50s in the valley locations. A few lake effect snow showers may
impact the western Adirondacks late in the day.
&&
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
The extended forecast period opens with zonal flow beneath an upper-
level low and subsequent upper-level trough that will send a
moisture starved cold front through the region overnight Thursday
into Friday morning as it follows a northeastward track further into
Quebec. Despite overall lack of moisture, some light snow showers
are possible mainly in the Western Adirondacks early Friday morning
as the the front picks up moisture off Lake Ontario. Dry conditions
are then expected to return despite the rotation of a shortwave
about the southern periphery of the upper trough Friday afternoon
through early Saturday morning. Without a moisture source, however,
the main influence of said short wave will be to increase the
pressure gradient across the region such that breezy winds are
likely Friday. High pressure will then build in at the surface
Saturday with weak ridging aloft to ensure dry conditions throughout
the weekend.
The remainder of the long term period contains a fair amount of
uncertainty. Though long range models are beginning to hint at a
developing large-scale trough over central CONUS and coastal low
forming somewhere along the Atlantic Coast that could pair to bring
us our next batch of widespread precipitation, several discrepancies
still exist pertaining to the evolution of these two systems as well
as the timing for their impact. These details will play a crucial
role in the duration, amount, and type of precipitation to expect.
For now, maintained higher chance to low likely probabilities for
precipitation since confidence is increasing surrounding the
likelihood of precipitation, but the details are still not certain.
Temperatures throughout the long term period will lean slightly
below normal with mainly 30s and 40s across valley areas and cooler
in the mountains.
&&
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
Precipitation is beginning over the region and some light snow
and sleet will occur at KALB, KGFL and KPSF through about 03Z,
as ceilings and visibilities lower to MVFR. Visibilities will be
predominantly IFR between about 03Z and 06Z at KGFL and KPSF as
the intensity of precipitation increase, then changes to more
rain by around 06Z, improving the visibility to MVFR.
Ceilings will be MVFR through the night but some brief periods
of IFR ceilings are not out of the question, just not enough to
put in TAFs and will amend if some intervals of IFR develop.
Precipitation becomes rain at KALB, KGFL and KPSF by around
05Z-06Z but surface temperatures will be near or just above
freezing.
KPOU should be just all rain. By 13Z-16Z steadier rain ends and
just some light showers with MVFR conditions continuing through
the afternoon.
Wind will be east to southeasterly through tonight at around 10
kt with a few higher gusts possible, especially at KALB/KPSF.
Wind will shift to the northwest later Wednesday morning at 5-10
kt.
Periods of LLWS will be possible at all sites tonight as a low-
level jet moves through. Winds at 2000 ft will range from 35-50
kt during this time. LLWS will end by mid morning Wednesday.
Outlook...
Wednesday Night: No Operational Impact. NO SIG WX.
Thanksgiving Day: Low Operational Impact. Breezy. NO SIG WX.
Thursday Night: No Operational Impact. NO SIG WX.
Friday: Low Operational Impact. Breezy. NO SIG WX.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: No Operational Impact. NO SIG WX.
Saturday Night: No Operational Impact. NO SIG WX.
Sunday: Low Operational Impact. NO SIG WX.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...Winter Weather Advisory until 10 AM EST Wednesday for NYZ032-
033-041>043-082>084.
MA...Winter Weather Advisory until 10 AM EST Wednesday for MAZ001.
VT...Winter Weather Advisory until 10 AM EST Wednesday for VTZ013-
014.
&&
$$
SYNOPSIS...Wasula
NEAR TERM...NAS/Wasula
SHORT TERM...Wasula
LONG TERM...Gant
AVIATION...NAS
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
728 PM CST Tue Nov 21 2023
.SYNOPSIS...
Issued at 257 PM CST Tue Nov 21 2023
Dry weather will prevail across central and southeast Illinois for
the next couple of days. High temperatures will remain in the 40s
on Wednesday, but will climb into the lower 50s by Thanksgiving
Day.
&&
.UPDATE...
Issued at 728 PM CST Tue Nov 21 2023
Main challenge remains with the narrow ribbon of clear skies west
of I-55. This has largely persisted since this afternoon while
edging southeast, though it`s starting to pinch off some south of
Peoria this evening. Latest HRRR suggests this area should fill in
some more over the next few hours, while trying to clear out
across the northeast sections of the forecast area. Some
adjustments were made to the sky grids to reflect these trends,
with overall partly to mostly cloudy conditions in the forecast.
Temperatures are generally on track at this time.
Geelhart
&&
.SHORT TERM... (Tonight through Wednesday)
Issued at 257 PM CST Tue Nov 21 2023
Overcast conditions persist across central Illinois this
afternoon: however, subsidence on the back side of a departing
short-wave trough has lead to a sizable tear in the overcast from
central Wisconsin into eastern Iowa. 2030z/230pm satellite
imagery shows skies beginning to clear west of the Illinois River,
and think this area of clearing will expand eastward toward the
I-55 corridor by early evening. The period of partly to mostly
clear conditions will be short-lived, as another band of low
clouds further west across central Iowa/Missouri shifts eastward
overnight into Wednesday. After a mostly cloudy start to the day,
skies will become sunny everywhere west of I-57 by Wednesday
afternoon...while locations further east remain partly sunny. Low
temperatures tonight will drop into the lower to middle 30s, while
highs on Wednesday top out in the middle 40s.
Barnes
&&
.LONG TERM... (Thursday through Next Tuesday)
Issued at 257 PM CST Tue Nov 21 2023
A cold front is progged to drop southward through central Illinois
on Thursday: however, it will be devoid of deep-layer moisture
and will produce little more than an increase in cloud cover and a
shift in the wind. After highs in the upper 40s and lower 50s on
Thanksgiving, readings will drop back below normal by the end of
the week. Predominantly dry weather is expected in the extended, with
the exception of late Saturday night into Sunday. The GFS/GEM/ECMWF
all show a short-wave trough ejecting eastward out of the Rockies
and tracking through the Midwest. While moisture will be limited,
enough synoptic lift will be generated to warrant chance PoPs.
With temps initially below freezing early Sunday morning, any
precip that falls will be in the form of very light snow before
readings warm sufficiently for rain or a rain/snow mix during the
day. Given the very light nature of the precip and the prevailing
warm ground temps, am only expecting very minor snow accumulations
of perhaps a couple tenths of an inch. Latest Grand Ensemble
shows a 30-40 percent chance of snowfall exceeding 0.1 inch
along/north of a Saint Louis to Danville line...and a 50-60
percent chance along/north of a Quincy to Minonk line. Once the
Sunday wave passes, an even colder airmass will settle into the
region early next week, resulting in highs only in the 30s for
Monday and Tuesday.
Barnes
&&
.AVIATION... (For the 00z TAFs through 00z Wednesday Evening)
Issued at 521 PM CST Tue Nov 21 2023
Widespread MVFR ceilings continue early this evening east of a
KPIA-KTAZ line. While skies scatter out for a time across much of
central Illinois this evening, another lower cloud deck will
approach from the west, and bring another round of MVFR conditions
overnight into Wednesday morning. Ceilings improve by mid morning
near KSPI/KPIA and across eastern Illinois by mid afternoon.
Geelhart
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Marquette MI
1026 PM EST Tue Nov 21 2023
.SHORT TERM...(Through tonight)
Issued at 236 PM EST TUE NOV 21 2023
Key Messages:
-Light rain and snow showers with a cold front moving through.
-Some lake effect snow showers linger across the eastern U.P.
tonight.
RAP analysis shows ridging over the Rockies with troughing extending
south through Ontario, digging into the central area of our CWA.
Another trough is analyzed over southeast Wisconsin and Lake
Michigan. These two troughs will continue to move east the rest of
today into tonight, phasing together over the eastern end of the
Great Lakes Basin and southern Ontario late tonight. This in turn
will push the ridge over the northeast U.S. coast out over the
Atlantic. The sfc low over the southern end of Lower Michigan will
continue northeast through this evening into southern Ontario before
moving east tonight into Wednesday with high pressure briefly
building in behind it.
Visible satellite shows a nice break in the clouds that has carried
into this afternoon with low clouds filling in along the cold front
over the west. This has allowed temps this afternoon to go above the
guidance with mid 40s across the interior west and central portions
of the U.P. The east has stayed cooler in the 30s under the cloud
cover associated with the sfc low over lower Michigan. Observations
have been quite dry so far, but some light snow showers and drizzle
have come to fruition from the sfc low. These light showers will
continue drying out from west to east moving into this evening as
the low continues east over southern Ontario. Meanwhile a cold front
is beginning to pass over Lake Superior and the western U.P. This
will bring another round of light rain/snow showers.
Cold northwest flow tonight following the cold front will keep some
lingering lake effect showers over the northwest wind belts, mainly
across the east with 850mb temps briefly dropping to around -6 to -
7C. However, with model soundings drying and quickly lowering
inversion heights as the night progresses, no significant
accumulations are expected. Low clouds off Lake Superior will help
keep the east warmer tonight, but lows in the mid to upper 20s are
expected with near 30 around Lake Superior.
.LONG TERM...(Wednesday through Tuesday)
Issued at 439 PM EST TUE NOV 21 2023
Key Messages:
- No widespread, significant snowfall through next week.
- Occasional w to nw flow LES expected late Wed night thru early
next week, but dryness of the air on most days will result in
only light accumulations of snow.
- Away from LES, dry, except maybe some light snow Sun and Tue
(less than 30 percent chance)
- Trend to below normal temps Thu/Fri, around normal over the
weekend, below normal again Mon/Tue - coldest days Fri and Tue.
Medium range models continue to depict a split flow regime into the
weekend with the northern stream becoming increasingly dominant for
Upper MI weather. Flow still looks to become a bit more consolidated
for a time heading into early next week. Guidance remains in good
agreement showing mid-level ridging/positive height anomalies
developing over the ne Pacific with axis then running n vcnty of the
w coast of Canada and thru AK thru the weekend. This 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 above normal on Wed trending to a mix of
normal and blo normal, beginning Thu and continuing thru at least
the first half of next week with coldest days Fri and Tue. Some
degree of ridging will persist near the W Coast next week, so temps
will be on the cold side of normal more often than the warm side as
we round out the month of Nov and head into the first days of Dec.
Any of the upcoming colder days will certainly be nothing out of the
ordinary for this time of year. As for pcpn, 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. Late weekend
thru the middle of 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 still nothing on the
horizon indicating any potential of widespread, significant snowfall
thru next week. So, it will be a slow start to establishing winter
snow cover in Upper MI. Farther down the road, a trend to prevailing
above normal temps appears to be in the offing for Upper MI
beginning the first full week of Dec per EPS/GEFS/GEPS. Above normal
temps are indicated to become widespread across Canada into the
adjacent Lwr 48. Recent CFSv2 ensemble means and ECMWF weeklies
carry this above normal temp regime thru the 2nd week of Dec as
well.
Beginning Wed, a weak northern stream shortwave will streak to
northern Ontario. Given the weakness of the wave and dry air, no
pcpn is expected ahead of the associated cold front that will reach
western Lake Superior late aftn. Expect highs in the upper 30s to
lwr 40s F.
As cold front sweeps se across Lake Superior Wed night, 850mb temps
around -6C overtop sfc water temps averaging around 6C will be
sufficient for isold/sct -shsn to develop due to the forcing along
the front. Will include 20-30pct mention from the Keweenaw eastward
as the front sweeps onshore. While hvy lake enhanced snow often
accompanies cold fropa during the cold season, dry air and lack of
ongoing LES will result in only light shsn. Any accumulation will be
nothing more than a dusting. 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 to develop given sfc water temps averaging around 6C.
However, incoming very dry air mass with inversions around 4kft 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, hostile for
LES. 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. Despite the dry air concerns,
the favorably positioned DGZ and lake-850mb delta-T increasing to
over 20C should support some flurries and isold -shsn developing
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 to perhaps nmrs -shsn.
Snow accumulations will be minimal given all the negatives,
generally no more than an inch. It will be a chilly day with
blustery nw winds gusting 20-30mph and slowly 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.
A shortwave will swing across northern Ontario and Lake Superior Thu
night. This should briefly increase nw flow LES Thu night as
inversion bumps up slightly. However, the strong negative of dry air
continues. In the end, while coverage of -shsn will increase a bit
Thu night, the snowfall will continue to be light, around 1 inch or
less into the eastern fcst area. Sct flurries/isold -shsn will
continue into western Upper MI.
By late Fri, low-level winds will back more westerly, shifting light
LES closer to shore over the e. However, with waa also getting
underway, expect any flurries over the w to end on Fri, and the
light LES over the e may diminish to just flurries. Highs Fri will
be in the mid 20s to around 30F.
A little moderation occurs on Sat under wsw flow ahead of the next
shortwave dropping se into s central Canada. A southern stream wave
will also be pushing out over the western Plains. Expect a dry day
with highs in the upper 20s to mid 30s F.
On Sun, the southern stream wave will get picked up by the northern
stream wave, but not phasing as they move into the Great Lakes
region. Result will be the potential of an area-wide -sn, but
accumulations would be minimal, under 1 inch if in fact widespread
-sn does develop. Passage of the shortwaves will bring a short
period of lake enhancement followed by LES for areas favored by nw
winds. At a minimum, models continue to show a little better LES
setup for this event than the LES setup for Thu into Fri as deeper
moisture will be involved this go around. Still, there is nothing
right now that suggests anything more than light accumulations
of snow, 1-3 inches, for the lake effect Sun into Mon.
Timing/amplitude of northern stream waves become much more uncertain
heading into midweek, but that`s expected at this time range. Next
wave may arrive as early as Tue, providing another period of lake
enhancement followed by nw flow LES.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1026 PM EST TUE NOV 21 2023
MVFR conditions will continue overnight before becoming VFR later
tonight which will last into Wednesday night at all sites.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 439 PM EST TUE NOV 21 2023
Cold front currently extending across central Lake Superior will
sweep across the rest of the lake tonight, followed by a period of
nw winds gusting 20-25kt. Across western Lake Superior, winds will
diminish to under 20kt 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/Fri. Given the increasingly colder air flowing across the lake
Thu/Thu night that will increase instability and thus mixing to
stronger winds aloft, gale potential will also increase. Currently,
there is a 35-45pct chance of low end gales across the e half of
Lake Superior on Thu. None of the models show mixing high enough to
reach gale winds aloft, but given the increasing magnitude of the
instability over the lake, would not be surprised to see mixing to
those gale winds happen, resulting in gale gusts near the sfc. Will
be something to monitor. Winds will only diminish a little late Fri
into Sat. Expect 20-30kt winds to prevail. Ahead of the next cold
front, wsw winds will increase some late Sat/Sat night, mainly w
half. Low end gale potential is 40-50pct there. Winds of 20-30kt
will shift nw later on Sun.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Jablonski
LONG TERM...Rolfson
AVIATION...07
MARINE...Rolfson
Area Forecast Discussion
National Weather Service Raleigh NC
940 PM EST Tue Nov 21 2023
.SYNOPSIS...
A storm system will cross our region through early Wednesday,
followed by passage of a strong upper level disturbance Wednesday.
This disturbance will exit late Wednesday, and will be followed by
cool high pressure for Wednesday night through Thursday. Another
upper level disturbance and surface low pressure tracking along the
Carolina coast may bring a chance of rain mainly to southern and
eastern areas late Friday into early Sunday.
&&
.NEAR TERM /TODAY THROUGH TONIGHT/...
As of 945 PM Tuesday...
Marginal severe threat appears limited to areas of the Sandhills and
Coastal Plain overnight. The threat is over in the NW Piedmont as
the front has passed back to the east.
A few wind gusts to 40-45 mph will be possible in heavier convection
later tonight over the eastern Piedmont eastward, with the marginal
risk of a damaging wind gust to tornado south and east of Raleigh.
A wedge boundary pushed NW into the Triad earlier this evening, but
has been pushed back E by the cold front from the west. To the east,
temperatures and dew points were in the lower to mid 60s with some
lingering 50s along the NC/VA border. Convection with this event has
been non existent for our region thus far. However, as of 930 PM
scattered convection (showers) had finally developed near a weak low
pressure near CLT. The showers extended north and east from CLT
through the Triad and Triangle areas, keeping these areas stable.
Showers have also stabilized the SE zones at times, keeping the
severe threat very low. The latest HRRR indicated that the main
threat of stronger storms may very well remain south and east of
Raleigh, mainly in the FAY to Goldsboro areas or along and east of I-
95. A few stronger wind gusts up to 40-45 mph will be possible
elsewhere east of the Triad region as the wedge boundary and cold
front merge and progress east overnight. Even after the front passes
later tonight and early Wednesday, periods of showers will continue
into Wednesday morning, mainly east.
Previous discussion... as of 400 PM Tuesday...
A surface low pressure system is currently centered over southern
MI, with a cold/occluded front draped to its south across eastern
KY/TN. The warm front has started to move NW into the Coastal Plain
and Sandhills, where dew points have risen into the lower-to-mid-60s
in many spots. Elsewhere the cold air wedge is still locked in, from
a 1034 mb high centered over Maine. Further lowered forecast
temperatures and dew points across the NW based on the latest obs,
as GSO and INT are still stuck in the mid-40s. Areas of stratiform
light to moderate rain continue across central NC, due to isentropic
lift and weak height falls from a shortwave trough extending from
the Upper Great Lakes into the mid-MS Valley. The environment across
central NC is still very stable, with any SBCAPE still to our south
over GA and SC, so no thunder is expected for the rest of the
afternoon. The main area of rain is currently pushing into eastern
zones, and then a brief lull in precipitation chances is expected
late this afternoon and early evening.
The main line of showers and storms associated with the cold front
is currently entering far western NC, and it is expected to enter
the Triad region after about 00z. It will then slowly push east
through the rest of central NC, with the CAMS showing it still over
the Sandhills and Coastal Plain early tomorrow morning. Some
lingering showers will still be possible behind it as another
vigorous shortwave approaches from the west. A lot of high-res
guidance continues to predict the warm front won`t clear the Triad
at all this evening before the cold front sweeps through tonight. So
it`s looking increasingly likely that at least the NW Piedmont
remains too stable for any thunderstorm activity at all with this
event. Still expect a secondary triple point low developing to our
SW to help continue pushing the warm front through the rest of
central NC the rest of the afternoon and evening, helping advect dew
points in the lower-to-mid-60s. So despite marginal instability
(MUCAPE around 500 J/kg or less), can`t ruled out an isolated
damaging wind threat tonight with the line, as effective bulk shear
will be on the order of 30-40 kts, and convective downdrafts may mix
down the strong flow in the low to mid levels (45-55 kts at 925 mb).
An isolated tornado also can`t be ruled out given model soundings
show potential for 200-300 m2/s2 of 0-1 km SRH. However, hodographs
are more linear by this time, as the flow in the low levels becomes
more unidirectional when it switches from SSE to SSW near the
surface. So this combined with the marginal instability make the
tornado threat appear quite limited. A marginal risk for excessive
rainfall also continues through tonight outside of the Sandhills and
central/southern Coastal Plain, as rainfall on the order of 1.5-2.5
inches is expected. However, the dry antecedent conditions should
help limit the threat, and the marginal instability will keep rain
rates from being too impressive. Low temperatures tonight still look
quite mild given all the clouds and precipitation, ranging from near
50 in the far NW to lower-60s in the SE.
&&
.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
As of 300 PM Tuesday...
By 12Z Wednesday, the cold front should be moving east across the
Coastal Plain, with a broken line of showers and scattered
thunderstorms mostly east of US-1. The limited MLCAPE and strong
shear will continue the marginal severe threat of damaging wind
gusts and possible isolated tornadoes across the Coastal Plain
through the early morning hours until the front pushes east out of
the region. Precipitable water values near 200% of normal will
continue heavy to moderate rainfall across eastern areas along the
front.
By late morning, an upper trough will slide east across the NC/TN
border, with forcing for ascent spreading across central NC for one
last potential round of scattered showers. As this wave moves by, PW
will be on the decline, and the system will have less moisture to
work with, with only light showers are expected. CAMs move all
showers east of the region by early evening. Skies will also become
clear to partly cloudy by late Wednesday night, with cold and dry
air advection in full swing as surface high pressure builds east
across the Southeast.
Highs will range from the upper 50s NW to upper 60s SE, and lows
will vary from the mid-30s to low 40s.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
As of 200 PM Tuesday...
...Thanksgiving Day will be dry with multiple slight chances for
precipitation late week into early next week...
Thanksgiving Day: Quiet, dry most of the day with increasing clouds
into early Fri morning. Central NC will be on the backside of a
departing shortwave with strongly convergent/subsident air already
overspreading the area by Thurs morning. Deep layer moisture will
also plummet to 0.5 to 0.25 of an inch leading to a very dry
thermo-profile below the increasing/thickening cirrus deck
overspreading the area from the SW. Temperatures will be warmest on
Thurs with the clearest day in the extended with highs rising into
the upper 50s to low 60s.
Fri: The tail-end of the positively tilted trough axis this morning
will pinch off into a closed low over northern Mexico late Wed and
lift NE Thurs and approach the Southeast and southern Mid-Atlantic
late Thurs into Fri. Overall weak synoptic forcing for ascent as it
transitions into an open wave and point soundings show saturation
fairly shallow within the mixed-phase region with lingering
dry/subsident low-level airmass in place. This should lead to
increasing cloud cover and virga moving into the Carolinas Fri into
early Sat. Light accumulations (< 0.10 of an inch) will still be
possible, mainly near the NC/SC border where deeper saturation will
be most likely with a chance for sprinkles farther north into the
Sandhills.
Weekend into early next week: An area of Canadian high pressure over
the northern Plains will spread east and ridge down through the Mid-
Atlantic late Fri into Sat remaining in place into early Sun. At the
same time, an area of low pressure is expected to develop off the
Carolina coast along an inverted trough axis Sun increasing rain
chances towards the NC coast. There is some uncertainty on the
inland wobble of this area of low pressure, but an ensemble approach
keeps the low off the NC coast with rain chances confined mainly to
the Coastal Plain. Another weak cold front may approach the region
Mon into Tues, but the position of parent high settling into the Mid-
MS Valley may lead to stalling of the front west of the mountains.
Temperatures will hover near normal for highs and lows with a brief
shot of cooler area behind the front Sat into early Sun morning.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 650 PM Tuesday...
A difficult forecast for the 24-hour TAF period. A batch of rain
impacting RDU/FAY/RWI continues to move ENE and should lift out by
02-03Z. A secondary batch of rain tied to a cold front will be
moving east and impacting all terminals tonight and overnight,
earliest at GSO/INT and latest at FAY/RWI. Based on latest
observational trends, a CAD wedge remains in place currently at
GSO/INT with LIFR conditions. With moderate rain expected to move
back in tonight, flight conditions may improve briefly at GSO/INT to
IFR or MVFR, but outside of rain LIFR should dominate under light
winds and a saturated boundary layer. There is some potential for
early morning fog at GSO/INT between 09 and 14z but confidence was
not high enough to include at this time. This TAF package went with
the more pessimistic guidance for GSO/INT, lifting from LIFR to MVFR
by 15-16Z Wed and VFR by 18z. At RDU/FAY/RWI, the CAD wedge has
lifted north with a warm front lifting into the terminals. This
should favor generally MVFR conditions ahead of the next batch of
rain, then IFR to perhaps briefly LIFR in rain/storms prior to 14z.
IFR conditions at RDU/FAY/RWI in rain should lift to MVFR by midday
Wed as rain starts to push out, then VFR toward the afternoon hours,
latest at FAY/RWI. LLWS should exit the terminals around 04z in the
west and 09z in the east.
VFR weather is expected to return Wed evening, lasting through at
least Thu. There is a chance of unsettled weather with light showers
Fri into Sat, mainly in our SE, although confidence in this is low,
and VFR conditions should still dominate through Sun.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Hartfield/JJT
NEAR TERM...Badgett
SHORT TERM...JJT
LONG TERM...Swiggett
AVIATION...Kren/Hartfield
Area Forecast Discussion
National Weather Service Tallahassee FL
938 PM EST Tue Nov 21 2023
...New UPDATE...
.UPDATE...
Issued at 918 PM EST Tue Nov 21 2023
A frontal system is slowly working its way through the area this
evening. Showers and thunderstorms have made it to roughly Lee Co,
GA to Bay Co, FL. SPC Mesoanalysis page shows that we`re capped at
the surface, but there`s 500-1000 J/kg of CAPE, highest around
the Apalachicola River area and the counties that surround it.
Bulk shear of 40-50kt, but the large scale support has lifted more
to the northeast. The 0Z TAE sounding shows similar data with
surface CAPE around 176 J/kg and mixed layer CAPE around 384 J/kg,
with shear values similar to the SPC page. If any additional
stronger or severe storms were to form it`d have to be along the
front itself. Behind the front, cloudy skies will linger.
&&
.NEAR TERM...
(Through Wednesday)
Issued at 315 PM EST Tue Nov 21 2023
Afternoon satellite and surface observations show a well-defined
cyclone tracking NE through the Great Lakes with an attendant cold
front extending across the Appalachians to the northern Gulf coast
and warm front penetrating the TN Valley. Meanwhile, vapor imagery
continues to highlight a shortwave digging down from the Midwest and
will be the main upper feature to watch going through tonight. We
remain in a large warm sector where widespread cloudiness and
pockets of showers have been ongoing since this morning. Several
rotating cells have been noted on radar thanks to sufficient deep &
low-level shear in place, but have been mostly weak and transient to
this point.
Current radar trends depict a relative lull in activity across the
service area, though a developing band of convection appears to be
getting gradually organized along a low-level convergence zone
around the I-65 corridor just ahead of the cold front. The 18Z HRRR
has this convective line intensifying through the afternoon as it
gradually marches eastward within a favorable environment for
severe weather where a tongue of modest instability is present,
per latest SPC Mesoanalysis. Hi-res trends suggests the window for
the severe weather threat maximizing is from about 3PM CST to
around midnight EST, with a probable weakening trend thereafter.
A Slight Risk (level 2 of 5) by the SPC is maintained for SE AL,
FL Panhandle, and portions of adjacent SW GA, while a Marginal
Risk (level 1 of 5) extends into the Eastern FL Big Bend through
12Z Wednesday. Greatest threats are damaging wind gusts and
perhaps a couple tornadoes. The former appears more likely given
the linear storm mode and LLJ, but embedded circulations within
the line, or semi-discrete cells out ahead of it could yield
tornadic concerns. A secondary threat is isolated heavy rainfall
that could lead to local runoff issues in urban, low-lying, poor-
drainage spots.
Full frontal passage is expected by mid-to-late Wednesday morning,
which will be met by northwest winds and a drier airmass filtering
in. However, lingering low-level moisture trapped beneath a post-
frontal inversion makes for cool and cloudy conditions. A
somewhat sharp NW-SE low-temperature gradient is forecast tonight
with readings ranging from the mid 50s to mid 60s. Daytime highs
stay mostly in the 60s outside of the Cross City area (low 70s).
&&
.SHORT TERM...
(Wednesday night through Thursday night)
Issued at 315 PM EST Tue Nov 21 2023
Thursday will be in between systems with a trough departing to our
east and a trough digging into the western Gulf. Cold air advection
will bring in much cooler air Wednesday night with lows in the lower
to middle 40s. Cloudy skies will linger as moisture lingers in the
upper-levels, and weak cyclogenesis takes place in the southwest
Gulf. Overall, a cool, cloudy, gloomy Thanksgiving is in the cards.
Highs will struggle to get out of the 50s. The cloud cover Thursday
night will likely inhibit much cooling with lows in the middle to
upper 40s. Some light showers are also possible Thursday night,
mainly near the coast and offshore.
&&
.LONG TERM...
(Friday through Monday)
Issued at 315 PM EST Tue Nov 21 2023
Weak upper-level perturbations continue to ride overhead as an area
of low pressure moves east across the southern Gulf of Mexico,
followed by a series of cold fronts. This will keep our forecast
rather gloomy through the long term with limited sunshine, cool
temperatures, and the chance for light showers.
Highs Friday through Monday will be in the middle to upper 60s with
lows in the mid 40s to low 50s. Another push of colder air arrives
early next week beyond the forecast period.
&&
.AVIATION...
(00Z TAFS)
Issued at 710 PM EST Tue Nov 21 2023
A line of storms is slowly working its way through the service
area this evening. The line currently stretches from Randolph Co,
GA to Walton Co, FL and is moving east. Expect periods MVFR to
LIFR as rain and storms pass over sites, with with VFR to MVFR
conditions ahead of the line. Behind it, MVFR to IFR cigs are
expected with winds shifting to the north and northwest. By late
morning to early afternoon, cigs should improve leaving us with
VFR conditions and breezy northwesterly winds.
&&
.MARINE...
Issued at 315 PM EST Tue Nov 21 2023
A cold front will sweep through the marine area late tonight into
Wednesday morning. Showers and a few storms, some possibly with
strong winds and waterspouts, will remain possible through tonight.
Winds will clock around from the south to the northwest and freshen
tonight as the cold front passes through. Border-line advisory level
winds are expected over the western waters to start Wednesday before
decreasing into the day Thursday. 3 to 5 foot seas will also be slow
to subside. Light to moderate east-northeast winds will continue
beyond Thursday into the weekend with maybe some light occasional
showers.
&&
.FIRE WEATHER...
Issued at 315 PM EST Tue Nov 21 2023
Any wetting rains and/or thunderstorms should come to an end by
Wednesday morning as an associated cold front passes through the Tri-
State area. Northwest winds then filter in with cloudy skies
persisting despite the drying airmass. Light northerly winds on
Thursday lead to low dispersions areawide on Thursday afternoon. Low-
end rain chances return to the forecast on Friday, but are mostly
confined to the coast. Overall, cool and cloudy conditions heading
into the weekend should preclude fire concerns despite no
appreciable rainfall expected beyond tomorrow.
&&
.HYDROLOGY...
Issued at 315 PM EST Tue Nov 21 2023
Rainfall totals so far today have largely been in the 0.5 to 1
inch range in the Panhandle to 0.25 to 0.50 inch in southeast
Alabama and southwest Georgia. We could still see another
widespread 0.25 to 0.5 inch of rain over the next 24 hours. Some
locally higher totals around 1 inch are still possible in heavier,
slower-moving storms. If there are any flood concerns, it`d be
limited to the urban areas. Otherwise, no flooding is expected.
Beyond this system, showers look to be light, only adding maybe
another tenth of an inch to our totals.
&&
.SPOTTER INFORMATION STATEMENT...
Spotter activation is requested. Spotters should safely report
significant weather conditions and/or damage by calling the
office or tweeting us @NWSTallahassee.
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 63 67 43 62 / 60 20 0 0
Panama City 58 64 44 61 / 70 10 0 0
Dothan 54 60 40 59 / 70 0 0 0
Albany 60 63 41 60 / 80 10 0 0
Valdosta 65 67 43 61 / 70 40 0 0
Cross City 67 73 44 64 / 40 50 0 0
Apalachicola 62 66 45 62 / 50 20 0 0
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk until 1 AM EST /midnight CST/ Wednesday
for FLZ108-112-114-115.
GA...None.
AL...None.
GM...Small Craft Advisory until 3 PM CST Wednesday for GMZ750-752-770-
772.
&&
$$
NEAR TERM...IG3
SHORT TERM...Young
LONG TERM....Young
AVIATION...KR
MARINE...Young
FIRE WEATHER...IG3
HYDROLOGY...Young