Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/20/18
Area Forecast Discussion
National Weather Service Birmingham AL
749 PM CDT Mon Mar 19 2018
.UPDATE...
MESOSCALE UPDATE.
&&
.DISCUSSION...
...SEVERE WEATHER THREAT CONTINUES...
The environment remains favorable for severe thunderstorms with
wind shear continuing to increase across our northern and central
counties. Though storm development remains more isolated across
our southern and central counties, any activity that develops and
intensifies will have the opportunity to tap into favorable
instability and dynamics that will support all convective hazards
from very large hail to tornadoes to damaging winds. Currently,
the most favorable area for severe storms in where the best low
level convergence is from Double Springs to Oneonta to Helfin.
These storms will slowly move south and east the nest few hours.
An effective surface dryline extended from near Natural Bridge in
Winston County southwest to near Vernon in Lamar County. The
severe weather threat will end as the dryline progresses further
southeast.
We have launched special weather balloon soundings every 3 hours
since 18Z this afternoon and the trend over time has been
increasing wind shear across central Alabama while robust
instability has been maintained due to the solar heating much of
the area experienced for much of the afternoon along with
generally southerly winds that have helped maintain dew points
generally in the 60`s across much of our forecast area.
A limiting factor in convective development has been the remnant
Elevated Mixed Layer (EML) that has persistently been present in
the observed soundings aloft this afternoon. This dry layer has
helped to promote the accumulation of convective available
potential energy while only permitting the strongest of updrafts
to break through the cap. This has resulted in the cap holding
strong across much of our south-central counties since mid
afternoon while earlier development across northeast Mississippi
and northwest Alabama have maintained their development and
further expanded in extent and intensity over the past few hours.
05/75
&&
.AVIATION...
00Z TAF Discussion.
Trend with this set of TAFs will be in a bit more optimistic
direction, as the higher coverage of convection thus far has
remained well to the north of central Alabama terminals. Will
maintain a VCTS for a couple of hours at most locations, although
it did push this back an hour or two from the previous forecast
(based on radar trends). Still quite a bit of uncertainty on how
far south the convection will get overnight. If radar trends over
the next couple hours show the storms eventually expanding in
area, then we can update the TAFs where necessary.
Winds will shift around to a more westerly direction overnight,
and start to increase and be more gusty after sunrise on Tuesday.
The models were giving me mixed signals on the development of
lower clouds after the rain/storm threat ends overnight. Given the
lack of clouds back to the west, I am inclined to believe the more
optimistic of the model solutions. But once the winds kick up
Tuesday, the cumulus field should start to fill in as well.
/61/
&&
.FIRE WEATHER...
After some storms tonight, light showers are possible Tuesday,
before dry conditions arrive by Wednesday. RH values will be
elevated the next couple days. There are no fire weather
concerns.
&&
.PREV DISCUSSION...
/Issued 649 PM CDT Mon Mar 19 2018/
Confidence has increased in the potential for explosive supercell
thunderstorm development late this afternoon into tonight
especially along and north of a line from Tuscaloosa to Calera to
Wedowee. A dangerous environment will also be in place south of
this line, but initiation of storms and storm coverage is
questionable.
Currently, surface winds have veered to the southwest across most
of the area following the passage of a warm front. Normally this
would yield lower dewpoints and overall moisture quality, but this
does not appear to be the case. Dewpoints are holding in the mid
to upper 60s upstream across MS. Moisture quality should not be an
issue as this event progresses.
This event will hinge on evolution of the surface to 850mb wind
fields in response to the approaching upper-level trough. We are
already seeing this response across the northern half of MS where
winds are south to southeast near Tupelo and Columbus. Hi-res
models appear to be getting a better handle on the mesoscale
features and are slowly trending more aggressive with surface
pressure troughing and backing of winds in the 23-03z time frame.
HRRR guidance suggests the potential for 0-1km shear to exceed
40kts. This amount of shear combined with SBCAPE of 2000-3000 J/kg,
supports a risk for a few long-track tornadoes. A violent tornado
cannot be ruled out. The best chance of these enhanced ingredients
coming together for long-track tornadoes appears to be from I-65
eastward and as far south as Shelby, Talladega, Clay, and Randolph
counties.
Balloon launches are planned for 330 PM, 6 PM, and 730 PM to sample
critical changes in the low-level wind environment.
87/Grantham
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 51 55 34 51 33 / 90 40 30 0 0
Anniston 53 56 35 53 33 / 90 40 30 0 0
Birmingham 49 54 37 56 36 / 80 40 20 0 0
Tuscaloosa 48 56 37 60 37 / 70 30 10 0 0
Calera 50 55 37 59 36 / 80 40 20 0 0
Auburn 56 59 38 58 36 / 70 20 20 0 0
Montgomery 57 60 39 62 38 / 60 20 10 0 0
Troy 55 62 41 62 37 / 50 20 10 0 0
&&
.BMX WATCHES/WARNINGS/ADVISORIES/...
None.
&&
$$
Area Forecast Discussion
National Weather Service Columbia SC
756 PM EDT Mon Mar 19 2018
.SYNOPSIS...
A warm front will lift northward and into the area tonight
ahead of approaching low pressure. The low will be in the region
Tuesday and northeast of the area Wednesday.
&&
.NEAR TERM /UNTIL 7 AM TUESDAY MORNING/...
A warm front is slowly lifting northward across southern
Georgia, while a cold front moves eastward through Mississippi.
Isolated to scattered showers/storms expected to develop along
the lifting warm front later tonight, and move towards portions
of the CSRA. Then after Midnight, a potential squall line in
advance of the cold front may then move across the cwa.
MUCAPE values will be higher overnight due to the cooler mid-levels.
However a stable near-surface layer will help to limit the severe
potential. Expect the line of thunderstorms along the warm front to
break up as it moves into the southern cwa and into the upper
ridge early tonight. Hrrr does show the squall line ahead of the
cold front moving through the area after Midnight. Although the
threat of severe weather becomes increasingly isolated through
the night we cannot rule out small hail, damaging wind gusts,
and even an isolated tornado with some of the stronger cells.
Overnight lows remaining mild with cloud cover expected.
Readings from the middle 50s north, to the lower 60s south.
&&
.SHORT TERM /7 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
A shortwave trough will move across the Southeastern US
and through the forecast area Tuesday afternoon and evening.
Models show an area of low pressure and an associated cold front
in the area shifting east. There is still some uncertainty
regarding the timing of the system and how far west into the
forecast area the moisture will be. The GFS pushes the deeper
moisture east of the area by 21Z while the NAM is slower pushing
the moisture east. A few strong to severe thunderstorms will be
possible particularly south and east of the I-20 corridor mainly
during the late morning and through the afternoon hours. The
far eastern portion of the area is in the Storm Prediction
Center`s slight risk for severe weather. The primary threats
appear to be strong to damaging winds, isolated tornadoes and
hail. Model LI values are around -5 to -7 with 0 to 6 km shear
values around 55 knots. Latest model guidance is trending warmer
further north with temperatures on Tuesday. This will
ultimately depend on the position of the warm front, but believe
northern counties will reside in the warm sector. Models show
the area becoming more stable Tuesday night. With the upper low
north of the area and wrap around moisture Tuesday night, have
continued likely pops north Tuesday night and slight chance
south. Winds will stay up Tuesday night with temperatures
forecast in the lower 40s.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
The shower chance Wednesday will be greatest in the north
section closer to deeper moisture and colder air aloft. Reduced
pops some on Wednesday especially further south given that the
models are pushing the upper low northeast of the area more
quickly and moving the moisture out of the area. Wednesday
appears quite breezy with a tight pressure gradient in the area.
Dry ridging is forecast to dominate Thursday and Friday. The
GFS and ECMWF MOS have temperatures during the early morning
hours Thursday and Friday in the middle and upper 30s. It may be
cold enough for frost. The models show much of the moisture
associated with a warm front north of the forecast area Saturday
and little moisture along a cold front Sunday. The GFS and
ECMWF MOS have pops 20 to 30 percent.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Broad upper trough over the central CONUS with weak upper
ridging off the SE coast. Closed upper low moving east towards
the Ohio valley. Surface low over W TN with warm front to our
west and south. Upper impulses interacting with the front
providing convection over S GA/N FL. This activity is expected
to shift east and remain just south of our forecast area (FA)
this evening. Warm front to shift north into our FA tonight
ahead of a cold front and prefrontal band of convection,
currently stretching across central TN into N AL, approaching
from the NW. Will expect lowering CIG heights later tonight in
response to the approaching warm fron and will include LLWS
with indications of a fairly strong low level jet developing.
Main concern will involve potential for convective activity,
possibly severe, to affect the FA late tonight. Main upper
energy to remain just to our north, with some guidance
indicating the convective activity weakening as it moves into
our FA. However, latest HRRR maintains potent band of convection
moving across the FA 06Z-10Z tonight. Combination of shear and
mainly elevated instability will provide a severe threat with
strong straight line winds appearing to be the main threat. Due
to uncertainity, will indicate a predominant period of SHRA
with VCTS late tonight, and tweak later based on radar trends
and latest guidance. Improving CIGs expected Tuesday morning.
Main upper trough will come through late Tuesday with main cold
front pushing through the northern FA during the morning, and
through the central and eastern FA Tuesday afternoon. Some
convective activity will be possible mainly S/E FA and towards
the coast Tuesday afternoon, and could be severe, and would be
more likely to affect OGB than the other TAF sites. Breezy
conditions expected to develop Tuesday.
EXTENDED AVIATION OUTLOOK...Some CIG restrictions possible late
Tuesday night and Wednesday morning. Otherwise, VFR and continued
breezy through Thursday.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Charleston SC
1050 PM EDT Mon Mar 19 2018
.SYNOPSIS...
A warm front will move north of our area tonight while a strong
cold front approaches from the west. The strong cold front will
cross the area Tuesday, followed by cooler high pressure for
the latter half of the week. A cold front could impact the area
next weekend.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
As OF 1040 PM: Very interesting storm structure ongoing across
north central GA. A series of supercells have formed a line and
will soon develop into a QLCS. Corfidi vectors indicate that the
convection will track ESE across GA late tonight. The forecast
arrival during the pre-dawn hours across the SC Lowcountry. I
will update the forecast to adjust temps and fine tune the PoP
timing and placement.
As of 945 PM: Latest SPC analysis continued to show a weakly
unstable environment across the forecast area, especially across
the SC Lowcountry. 0Z CHS observed sounding showed less than
200 J/kg of CAPE and around 40 J/kg of CIN. Based on radar
trends and the latest HRRR run, I will expect the coverage of
the rainfall over the southern tier of the CWA to decrease
sharply by midnight. I will update the forecast to adjust PoP
timing and placement through early Tuesday morning.
As of 745 PM: KCLX radar indicated stratiform rain with embedded
showers/thunderstorms advancing across SE GA. Latest SPC
mesoscale analysis indicated that the storms have encountered
the stable air mass that was left over from the morning in-situ
wedge. I will update the forecast to increase PoPs across the GA
zones through 11 PM. The next interesting feature is a
developing severe MCS over northern AL. This feature will likely
remain highly organize as it tracks SE across GA late this
evening into the early morning hours. However, the activity
currently over SE GA will likely work over the environment over
SE GA. Steady SSE winds may advect weak instability across the
SC Lowcountry, but model guidance show only minor increases in
CAPE. Overall, this line will weaken as it approaches the
forecast area after 3 AM. However, due to the rapid motion and
high organization, this line will need to be monitored closely
for severe weather.
The most interesting period for severe weather appears to occur
after sunrise Tuesday into the early afternoon. The low level
water vapor channel from GOES-16 indicated what appeared to be
an elevated mixed layer over the western Gulf of Mexico, sourced
from the high Mexican hill country. In fact, 0Z sounding from
Brownsville, TX indicated a layer of steep lapse rates from
600mb to 400 mb. The GFS indicates that this region of steep
lapse rates will slide east ahead of an amplifying H5 trough,
reaching the forecast area by late Tuesday morning. At the sfc,
the cold front will like sweep over the Coastal Plain during the
mid morning. Given a few hours of sunlight, the atmosphere will
likely become moderately unstable with significant veering llvl
wind fields. Model sounding parameters appear very respectable,
TT in the mid 50s, EHI above 1.5, SWEAT above 400, and WBZ
around 10 kft. These storms will be in a favorable environment
for severe hail, damaging winds, and possibly a tornado.
Previous Discussion:
A complex weather forecast for tonight. The
mid/upper levels consist of semi-zonal flow over the area while
a stronger disturbance passes well to our northwest. There are
weaker disturbances within the general flow that will pass over
our area, but the strongest ones will remain to our north and
west. At the surface, observations indicate a weak/diffuse warm
front spread across our area and slowly moving northward. It`s
exact location is somewhat difficult to pinpoint, but the
expected trend is for it to strengthen and accelerate northward
this evening, being well north of our area overnight. This is
because low pressure currently moving over the lower/mid MS
Valley will move northeastward and intensify, becoming located
over NC by daybreak. Attached to the low will be a strong cold
front that will quickly zoom eastward. The front is expected to
be well to our west late tonight. There is plenty of moisture
across the region, with a band of ~1.5" PWATs spreading into our
area from the south this evening. A disturbance is helping to
generate convection over FL. Both synoptic models and the CAMs
indicate this feature moving northward and into at least our
southern portion of the area this evening. It should then weaken
as it moves northward and offshore. We tried to account for it
the best we can with the hourly POP grids. But more adjustments
will be needed based on radar trends. Additionally, convection
currently near the AL/GA border is stronger than expected and
racing eastward. The CAMs haven`t done that well accounting for
this, but the current thinking is for it to weaken as it gets
closer to our area and merges with the previously munitioned
weakening area of convection. Instability for our area this
evening is decent. LI`s and Showalter values are negative. Lapse
rates are steepening. SPC Mesoscale Analysis indicates MLCAPEs
across GA approaching 500 J/kg. 0-6 km shear is 60-70 kt. So
there is the risk for strong thunderstorms with gusty winds. The
severe risk this evening is low because the best instability
remains out of our area. After this band of convection moves
through late this evening, all models are in good agreement of
their being a lull in precipitation until around daybreak. A
strong line of showers and thunderstorms will be approaching
from the west at that time. (See the discussion below for more
details.) Lows will range from the upper 50s to the lower 60s.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
Tuesday: An "Enhanced Risk" of severe weather is forecast across
parts of Southeast South Carolina and Southeast Georgia Tuesday
morning into early Tuesday afternoon, especially along the
coastal corridor.
Latest guidance indicates a progressive shortwave trough with a
strong mid-lvl speed max skirting along the northern coast of the
Gulf of Mexico and over northern Florida during the day. At the sfc,
the area will be warm sectored ahead of a cold front that quickly
pushes eastward given strong and deep westerly flow off the sfc. The
timing of this front will play a large role in the overall strength
of thunderstorms and the severe weather threat across the area
Tuesday morning into early Tuesday afternoon. Given strong
unidirectional wind fields associated with the passing system along
with DCAPE values as high as 800-1000 J/kg within the warm sector,
the main severe weather threat should come in the form of damaging
straight-line winds associated with a line of strong to potentially
severe thunderstorms during morning hours, potentially into early
afternoon.
Increasing mid-lvl lapse rates around 7-8 C/km, lifted index values
upwards to -5/-6 C, along with 0-6km bulk shear of 50-60 kt could
produce bouts of moderate size hail in deepest convection. Although
low-lvl lapse rates and veering are not particularly strong over the
area (stronger north near the passing low pressure center), a quick
punch of low-lvl moisture characterized by PWATs near 1.25-1.5
inches, low LCLs, increasing SBCAPE (1500-2000 J/kg), including a
fairly large amount of 0-3km CAPE, could be sufficient to support an
isolated tornado or two across the area, mainly in thunderstorms
that initially develop within breaks of a convective line or just
ahead of the convective line. The greatest potential for severe
weather is anticipated along the coastal corridor of Southeast
Georgia and Southeast South Carolina where warming into the low/mid
70s coincides with the arrival of stronger wind fields and forcing
associated with the advancing cold front, progressive h5 shortwave
and divergence with a passing h25 jet aloft. Although conditions
appear conducive for strong and/or severe thunderstorms Tuesday
morning and potentially into Tuesday afternoon, ongoing convection
upstream could make way into the area late tonight and impact the
overall severe weather setup across Southeast South Carolina and
Southeast Georgia. Should this scenario unfold, activity would
likely suppress the overall strength potential of thunderstorms
Tuesday morning due to ongoing rains and widespread clouds. Activity
will have to be monitored tonight for any potential changes. Once
the cold front pushes through the area, the threat of severe weather
will come to an end. However, some lingering showers are possible
into mid late afternoon hours until the mid/upper lvl trough shift
offshore. Expect conditions to dry out fairly quick Tuesday night
with lows dipping into the low/mid 40s.
Wednesday and Thursday: Sfc low pressure will pull away to the
northeast while a mid/upper lvl trough remains overhead into
midweek. The main issue will be gusty winds over much of the area as
a tight pressure gradient occurs over the Southeast. In general, we
could see west-northwest wind gusts upwards to 25-30 mph as sfc
temps warm into the upper 50s/lower 60s Wednesday afternoon.
Overnight lows could approach the mid/upper 30s, leading to some
frost concerns away from the coast late. By Thursday, the pressure
gradient will relax with weather conditions remaining quiet and dry.
Afternoon temps should warm a few degrees, peaking in the lower
60s.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Models remain in fairly good agreement through the long term period.
Surface high pressure will drift overhead on Friday and then
eventually into the Atlantic by Saturday. A cold front will approach
from the west on Saturday, and then cross the area sometime late
weekend. Moisture doesn`t appear overly impressive so little, if
any, precipitation is expected to accompany it. Temperatures will
gradually warm through the period as flow turns more southerly.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
As of 2335z: KCLX Doppler radar indicated stratiform rain with
embedded showers and thunderstorms moving ENE across SE GA. This
activity is expected to pass over KSAV through 4Z, highlighted
with a TEMPO from 0Z-4Z. By late this evening, convection should
slide off the coast and MVFR to IFR stratus should develop
across the region. A MCS developing over northern AL will
organize and race SE late tonight. HRRR times the line passing
across KCHS between 10Z to 14Z, highlighted with a TEMPO. A few
CAMs indicate that a second round of thunderstorms may develop
during the late morning to early afternoon hours, between the
cold front and the coast. These thunderstorms will likely
develop in an environment that would support large hail,
frequent cloud to ground lightning, and damaging wind gusts. I
will highlight with a PROB30 from 16Z until 21Z. Late afternoon
should feature gusty SW winds and VFR conditions.
Extended Aviation Outlook: Flight restrictions are likely Tuesday as
showers/tstms associated with a cold front impact the region.
Clearing will take place Wednesday, with VFR expected the rest of
the week. Breezy conditions likely Tuesday and Wednesday.
&&
.MARINE...
Tonight: A warm front will move north of our area while a
strong cold front approaches from the west. Winds will gradually veer
to the SW and increase, most noticeably late in the time
period. Wind gusts could approach 25 kt for the outer GA waters
(AMZ374), but we think they will stay just under Small Craft
Advisory criteria. Additionally, the risk of thunderstorms
continues. Some storms could become strong enough to require
warnings. There is even a small risk for isolated waterspouts.
Tuesday through Saturday: Marine conditions will deteriorate on
Tuesday as the pressure gradient tightens ahead of an area of low
pressure. A strong cold front associated with this low pressure
system will then shift offshore later Tuesday with strong cold air
advection in its wake. Small Craft Advisories will likely be needed,
beginning as early as late Tuesday morning in the outer Georgia
waters, and then spreading to most, if not all, waters later in the
day. Gale force winds are also possible in offshore Georgia waters
for a period of time Tuesday night through Wednesday morning. It`s
still too early to hoist a Gale Watch at this time based on the
timing of the event. Winds and seas will improve on Thursday as high
pressure builds in and the gradient slackens. The high will drift
overhead Friday and then into the Atlantic by Saturday, allowing
winds to become southerly.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
NEAR TERM...NED
SHORT TERM...
LONG TERM...ECT
AVIATION...NED
MARINE...
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1028 PM EDT Mon Mar 19 2018
.SYNOPSIS...
A complex low pressure system will approach from the west tonight
bringing showers and thunderstorms to the region. The low will cross
the region tomorrow through tomorrow night. In its wake, mountain snow
showers are likely late Tuesday through Wednesday. Drier high pressure
will return over the area on Thursday with another moist low arriving
from the west for the weekend.
&&
.NEAR TERM /THROUGH TUESDAY/...
As of 1025 PM EDT Monday: Showers and isolated thunderstorms are
quickly becoming widespread across the area this evening. In fact,
there is some lightning in the heavier showers north of where the
best MUCAPE is. Therefore expect a few rumbles of thunder across the
entire area but the best chance for any severe storms remains across
the western and southern forecast area where the better instability
and effective bulk shear exist. The latest CAM guidance shows this
as well. The 01Z HRRR is particularly interesting as it develops a
meso-low and squall line with embedded bow echoes over north central
GA and moves it across the southwestern portion of the forecast
area. However, it appears to have initialized this feature too far
north. That said, will need to keep an eye on the convection over GA
as it moves ESE. Can`t rule out a strong storm over the NC mountains
given the strength of the convection over TN.
Otherwise, potent little ball of vorticity is working its way toward
the Mid-MS Valley this evening. Surface pattern is a bit of a mess
with the primary low over the Ozarks, a secondary low (almost a
Miller B looking thing) over extreme SW VA, with a warm front
stretched between the two and then around the Appalachians where a
bit of damming remains, though little bits of sunshine that peeked
through today have done a good job with eroding some of that. High
clouds have been on the increase today which have kept temperatures
down across the western half of the area after some initial sunshine
this morning. Ahead of the approaching surface/upper low, isentropic
lift is on the increase as well, and will result in a gradual
blossoming of showers and possibly drizzle (or at least low clouds)
this evening.
The surface low will lift NE into S KY, but with the damming wedge
still weakly in place, a secondary low should form somewhere across
N GA or possibly even the Upstate. The front will be draped like a
ribbon between the two, eroding the damming from the SW as the two
lows lift NE. With the diffluence aloft ahead of the upper low, the
incoming upper jet, plentiful dPVA, plus the lift associated with
the cold front itself, we`re looking at a strongly forced synoptic
system pushing through tonight and tomorrow. Deep-layer shear will
be impressive as the system moves across, with 0-6km shear of at
least 50-60kt (though higher naturally closer to the upper low). Low-
level helicity of at least 200m2/s2, in some cases 300-400m2/s2, will
result in beautifully curved hodographs tonight, peaking in shape
around 06z (give or take an hour or two depending on the site).
To counteract this scary-looking shear, as is typical in damming
events (not to mention just the overnight frontal passage), CAPE
will be limited. We seem to be in a bizarro world because the NAM is
actually on the low side of CAPE for once, not bringing any into the
northern Upstate or NC overnight, but with a very strong gradient
right on our southern CWA border. The GFS, however, brings a good
200-400J/kg in a finger up the foothills and I-26 corridor
overnight. That said, though, even with the lack of instability, if
supercells really get going over N AL and N GA, the immediate storm
environment might certainly be enough to overcome the surrounding
environment, and SPC HREF does bring streaks of concerning max
updraft helicity across the Upstate (I-85 and south) overnight. SPC
Slight Risk was expanded to include all of our NE GA counties and
Greenwood/Abbeville, with the Marginal risk extending almost to I-
26. Severe thunderstorms with damaging winds/large hail and possibly
isolated tornadoes certainly can be expected, though the threat
would diminish the farther east you go. CAMs do still have a greater
area of thunderstorms pushing across the area overnight so isolated
strong winds will be possible just about anywhere, with of course a
widespread lightning concern. The thunderstorm threat will be
pushing out in the predawn hours.
Heavy rain, of course, will be a threat with the convection moving
through, but it should move through fast enough that most areas will
see no more than an inch, basin-average, though with convection it`s
certainly possible that isolated areas might see more than that. Any
flash flood threat would be minimal.
A secondary shortwave diving down the NW flow behind the initial
upper system will bring a secondary surge of lift to the area on
Tuesday. Lapse rates will increase and with temperatures warming
behind the eroded CAD (to fairly seasonal levels), can`t rule out
some isolated thunderstorms especially across the NC foothills and
Piedmont, but for now have kept wording at showers.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 3:00 PM EDT Monday: An upper level low pressure system roughly
located over northern Tennessee and Kentucky, will wobble into our
region Tuesday night while low pressure develops along the Mid
Atlantic Seaboard.
As spokes of energy move through the area, crashing heights aloft,
coupled with a potential deformation zone, cold air being drawn in
from the north (via CAD like structure) and cold air aloft, should
set-up a banding or a deformation zone of precipitation.
Precipitation will be ongoing Tuesday night, with the greatest
values over the northern three quarters of our forecast area (FA).
Considering thermal profiles, rain will change to snow over the NC
mountains and perhaps foothills and mountains of NE Georgia Tuesday
night.
It appears the focus of precipitation will remain over the northern
half of the FA Wednesday, before being drawn back to the mountains,
as low pressure shifts north and northeast up the coast, and
lingering upslope conditions remain.
Considerable collaboration with surrounding offices and National
Centers concerning snow amounts and timing. It appears we are
looking at about a 24 hour event. We have issued a Winter Storm
Watch from midnight Wednesday to midnight Thursday for 3 to 6 inches
of wet heavy snow. Although we might fall just a tad short on the
deterministic numbers, wind gusts increasing to 35 to 45 mph and
even higher on the mountain tops, (combined with the potential heavy
snow), could lead to impact issues. We would not be surprised if the
model trend remains that a slice of Winter Weather Advisories might
be needed across the foothills of NC, perhaps fanning out along the
I40 corridor and the mountains of NE Georgia.
As the surface and upper level energy move away Thursday, weather
conditions should quiet.
We are looking at below normal temperatures during this part of the
forecast cycle.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 220 PM Monday: the extended fcst picks up at 00z Friday with
broad upper trofing moving off the Atlantic Coast while upper ridging
spreads over the Central CONUS. As the upper ridge approaches our
region, it is expected to deamplify and flatten. This more zonal
pattern is expected to persist over the area thru the weekend and
into early next week. At the sfc, cool and dry high pressure will be
in place to start the period. As we move into the weekend, another
low will deepen over the plains and move eastward. As this happens,
low-lvl flow will become more southerly and deeper moisture will
overspread the fcst area as a warm front lifts northward. Beyond this
point the track and evolution of the low remains fairly uncertain
with the ECMWF moving the system to our north late Sat/early Sun and
then offshore later on Sunday. The GFS, on the other hand, dissipates
the low by early Sunday and develops a wedge over our fcst area that
lingers for the remainder of the period.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
At KCLT and Elsewhere: Skies have held at MVFR across the western
TAF sites but remain chaotic at KCLT and KHKY. Expect MVFR to
develop at those sites with IFR elsewhere through the evening. Have
used CAM guidance to time best chances for heavier rain or thunder
and LIFR restrictions. After the convection moves through, IFR to
MVFR cigs with LIFR to VLIFR cigs will linger through day break.
Conditions improve by mid-morning but MVFR cigs will linger or
return to portions of the area. General S to SE winds this evening
become SW overnight. SW winds on Tuesday become W to NW for the
afternoon. Gusts are most likely at the western sites. There will
even be some scattered showers for the afternoon, but chance too low
to include except at KCLT.
Outlook: Colder air wrapping around the exiting system will bring
snow to the mountains, and potentially mixed precip to to KAVL, KHKY
and KCLT Tuesday night into Wednesday morning, VCSH/-SHRA is
expected elsewhere. MVFR/IFR anticipated, with VFR returning late
Wednesday.
Confidence Table...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 84% Med 73% Med 65% Med 70%
KGSP High 84% Med 76% High 89% High 100%
KAVL Med 72% Med 77% High 100% High 100%
KHKY High 81% Med 73% Low 56% High 85%
KGMU Med 74% Med 73% High 83% High 100%
KAND High 80% Med 79% High 86% High 100%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:
www.weather.gov/gsp/aviation
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Winter Storm Watch from late Tuesday night through Wednesday
evening for NCZ033-048>052-058-059.
SC...None.
&&
$$
SYNOPSIS...JPT
NEAR TERM...RWH/TDP
SHORT TERM...TS
LONG TERM...JPT
AVIATION...RWH
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1015 PM CDT Mon Mar 19 2018
.DISCUSSION...
Storms are long gone and now seeing the drier/cooler air making
its way into SE TX this evening. Forecast/grids looks on track.
Not planning on any major changes. 41
&&
.PREV DISCUSSION... /ISSUED 259 PM CDT Mon Mar 19 2018/
Temperatures were very warm this afternoon and Galveston
established a new record high temperature for the day. A
combination of a warm start to the day and a west wind will
generally deliver very warm temps to the region. At 2 PM, a cold
front extended from low pressure over So Missouri to near
Texarkana to near Rockport to Laredo. Radar is showing a few
showers/thunderstorms along the middle Texas coast as lift from
the front coupled with PW values near an inch and daytime heating
trigger precipitation. The experimental HRRR and TT WRF both show
some showers moving up the coast late this afternoon into this
evening so have added isolated shra/tsra to areas mainly east of
US Highway 59 but showers should mainly be along the coast.
Once the front clears the coast, skies will clear area wide. Winds
will decouple inland and the dry air in place will allow for ideal
radiational cooling. Low temps by Tuesday morning will cool into
the mid and upper 40s. The rest of the week looks quiet with
seasonal temperatures. The surface high will settle over SE TX on
Wednesday morning with the coolest temperatures of the week
occurring that morning. The high moves east of the region by
Wednesday evening and onshore winds will return and bring a slow
increase in low level moisture. Winds will increase Thursday night
into Friday as low pressure in the lee of the Rockies deepens.
Upper level ridging over northern Mexico will amplify and expand
over the state and suppress rain chances through Friday night. Low
level moisture will deepen enough that a few showers will be
possible by Saturday under a strengthening capping inversion. The
cap will remain in place through Monday albeit slightly weaker as
the upper level ridge is displaced to the east as a deepening
upper trough moves into the southern Rockies. The middle of next
week is looking wet as the upper level trough moves very slowly
across the southern plains. 43
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 47 70 45 75 52 / 0 0 0 0 0
Houston (IAH) 49 73 48 76 54 / 10 0 0 0 0
Galveston (GLS) 56 71 55 72 62 / 10 0 0 0 0
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION from 3 AM to 10 AM CDT
Tuesday for the following zones: Galveston Bay...Matagorda
Bay.
Small Craft Advisory from 3 AM to 10 AM CDT Tuesday for the
following zones: Coastal waters from Freeport to the
Matagorda Ship Channel out 20 NM...Coastal waters from High
Island to Freeport out 20 NM...Waters from Freeport to the
Matagorda Ship Channel from 20 to 60 NM...Waters from High
Island to Freeport from 20 to 60 NM.
&&
$$
Area Forecast Discussion
National Weather Service Wilmington NC
957 PM EDT Mon Mar 19 2018
.SYNOPSIS...
Low pressure will move east toward the Carolinas on Tuesday, dragging
a cold front through Tuesday night as it tracks northeast and
deepens off the North Carolina coast. Possible strong to severe
thunderstorms will occur ahead of the low on Tuesday with
potential for a few flurries in the mix as colder air moves in
on the back end on Wednesday. Cold and dry high pressure will
extend down into the Carolinas Thursday and Friday. The weekend
may become unsettled and remain cooler, with clouds and periods
of rain possibly through early next week.
&&
.NEAR TERM /THROUGH TUESDAY/...
As of 930 PM Monday...01Z surface analysis show low pressure
centered over middle TN and north-central AL, with a warm front
extending to just south of Charleston, SC. The low will track
east-northeast through the remainder of the overnight, as the
warm front lifts north. Showers and thunderstorms associated
with the surface low will track across the forecast area between
09Z-12Z, and although they should be weakening with diminishing
upper support, the presence of shear along the warm front will
necessitate a close watch for potential rotation.
After a lull in activity in the 12Z-18Z window, a vigorous mid-
level trough and associated surface cold front will approach
from the west in the afternoon and evening hours Tuesday. This
will give the atmosphere an opportunity to destabilize, with
surface-based CAPE values reaching 1500-2000 j/kg. SPC has
included the CWA in an slight to enhanced risk of severe storms
for Tuesday afternoon, noting the possibility of a few
tornadoes considering the amount of low-level wind shear.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 300 PM Monday...Complex storm system will be exiting the
area albeit slowly through the period. The latest guidance has
shown a considerable drying trend with precipiation through the
period. It appears the mid level cyclone will just be pulling in
too much dry air to allow any significant showers to develop.
Overall I have trended pops down through the period.
Temperature guidance continues to show some differences but in
general maintained a blend.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 300 PM Sunday...Although I would not discount a few
flurries as potent shortwave swings through the back end of the
upper trough early Thurs, the moisture will be very limited.
Therefore will not include any pcp in forecast early Thurs
morning as upper trough swings off the coast. CAA continues
through Thurs into Friday in strong NW flow as high pressure
builds in from the north. The 850 temps drop down around -4c and
do not return above 0c until Sat. Temps will drop into the 30s
most places with some frost or freeze potential in spots again
early Fri morning. Temps both Thurs and Fri may not reach above
60. Low pressure system will brush the Carolinas Fri night into
Sat as it moves toward the Mid Atlantic coast. This will produce
increase in clouds and greater chc of rain across the area late
Fri into early Sat. The latest model runs show a possible wedge
type scenario setting up for the weekend with clouds and periods
of rain possible. Overall, the weather may turn out to be cooler
and more unsettled than originally forecast.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
As of 23Z...The next 24 hours should be a roller coaster, especially
for the coast. The first batch of convection will be associated with
the warm front which will move through the region through the
overnight hours. The HRRR model has some pretty rigorous convection
hitting the western CWA around 08Z, rolling to the coast by 10Z.
Gusty southwest winds and brief IFR visibilities in heavy showers
are possible. Thunder can not be ruled out, but the convection will
likely weaken as it nears the coast.
Tuesday, a possible wild day in store as the cold front approaches
from the west. The convection will be strongest near the coast, as
it will have the best moisture and possible sea breeze interaction.
Strong thunderstorms are possible as we are in a favorable region
for convection with strong shear, with moderate cape and helicity.
Extended outlook...Periods of MVFR/IFR through Wednesday.
&&
.MARINE...
NEAR TERM /THROUGH TUESDAY/...
As of 930 PM Monday...A weak pressure gradient is in place
across the waters this evening on the north side of a warm
front, which will progress north overnight. Winds will remain
light, generally 10 knots or less, and mainly east-southeast
until the front lifts through after midnight. At that point,
winds will become south to southwest and increase to 15 knots,
and shower and thunderstorm activity is expected to be moving
off the coast in the few hours before sunrise.
Conditions will deteriorate Tuesday, as SW winds pick-up ahead
of a cold front. An advisory may not be needed but a few lines
of showers, and even strong TSTMS could impact the 0-20 NM
waters Tuesday morning, and again in the afternoon. Mariners can
expect SW gusts near 20 kt Tuesday, outside of showers and
TSTMS. Seas will build to 3-5 ft Tuesday afternoon, and an
`Exercise Caution` headline may be needed. A radar update is
recommended before venturing out, as some storms may become
capable of gusts in excess of 35 kt Tuesday morning and again in
the afternoon.
SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 300 PM Monday...Expect a rough and tumble period for the marine
community. A complex storm system will be exiting the area with
initially gusty southwest winds. The winds will shift to northwest
by Wednesday evening but the speeds will remain elevated in a 20-25
knot range. Some guidance is showing higher winds and subsequent
shifts may need to increase the wind forecast with gales a
possibility. Not surprisingly considering the winds, seas are
expected to be high from 4-8 feet with the higher values across the
outer waters.
LONG TERM /THURSDAY THROUGH SATURDAY/...
As of 300 PM Monday...Cold and dry high pressure will extend
down over the local waters Thurs through Saturday. Strong off
shore flow up to 15 to 20 kts early Thurs will weaken and become
more northerly through the period down to 10 kt or less by Sat.
This will allow seas to subside from close to 3 to 5 ft early
Thursday down less than 3 ft by Fri aftn into Sat.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.
&&
$$
NEAR TERM...MJC/CRM
SHORT TERM...SHK
LONG TERM...RGZ
AVIATION...MRR
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
914 PM CDT Mon Mar 19 2018
.UPDATE...
Updated for evening discussion.
&&
.DISCUSSION...
All of the products and graphics have been updated by now to show
that the CWA is clear of any severe wx threat tonight. A cooler
air mass will move into the region overnight. The gusty winds we
saw today will slacken a bit but will remain between 5 to 10 kts
throughout the area tonight. As the upper low pushes to the
Ohio Valley tonight, some wrap-around moisture may be enough to
form some light showers in the northern half of the area in the
morning. Otherwise, skies will be partly cloudy overnight and temps
will fall into the 40s by dawn. /10/
Prior discussion below:
Today and Tonight...
A warm day is unfolding across the region as we continue to monitor
radar and satellite for storm initiation as a dryline progresses
across our region. Latest HRRR guidance is bullish with storms in
north MS but even it agrees on storms having a hard time breaking
the cap in our region. However, we will maintain the threat of
isolated severe storms for the rest of the afternoon and into the
evening in the eastern portions of our region as the atmosphere
still remains prime to support storms in that area if the cap is
ever broken.
Drier, cooler air will filter into the region overnight behind the
surface front. Cloud cover will begin to increase again tomorrow
morning as wrap around moisture, associated with the deep low
that will continue to progress eastward, moves into the region
from the north. A secondary shortwave, ejecting into the region
from the NW, may provide enough lift to kick off some light shower
activity through the day on tomorrow, with the best chances
occurring in the northern portions of the ArkLaMiss. Highs
tomorrow will be about 10 degrees below normal areawide.
Tuesday night through Sunday: The light rain Tuesday should end by
Tuesday evening and a period of dry weather is expected Tuesday
night through Friday. Rain chances still look to return to the
northern zones Friday night and continue over at least the northern
half of the area through the weekend. Tuesday evening the nearly
stacked low is expected to be centered over the Ohio valley with
northwest flow aloft remaining across our region. This will help a
>1020mb high build over our CWA from the northwest. With the high
still to our northwest early Wednesday morning the wind may not
decouple but, CAA and clear skies will allow temperatures to bottom
out well below normal. Mid 30s will be possible across our northeast
and there is some concern that patchy light frost may develop. The
surface high will become centered over our CWA Wednesday and still
be over eastern Mississippi early Thursday morning. Under clear
skies and a near calm wind all night patchy frost development is
more likely over our northeast zones as temperatures there bottom
our in the mid 30s again. The surface high will shift east of our
CWA Thursday and light return flow is expected during the afternoon.
Normal highs run from the upper 60s north to the lower 70s
southeast. Temperatures will top out close to normal in the
southwest but slightly cooler than normal elsewhere. Temperatures
and moisture will continue Friday into the weekend. A large closed
low moving over the northwest CONUS will induce mid level ridging
over the central CONUS Friday. This ridging aloft will shift east
over our region as a shortwave moving out of the southwest CONUS
deepens a Lee side low. Models differ on when rain chances will
return to our CWA but Friday still looks warm and dry. The surface
low will track east and weaken. It now appears more likely that its
cold front will stall north of our CWA Saturday though daytime
heating should be able to set off a few storms across our northern
zones. The stalled front is expected to remain north of our CWA
through Sunday. Rain chances look to remain more confined to the
northern half of our CWA with warmer than normal temperatures and
dry weather across our south. /22/
&&
.AVIATION...
18Z TAF discussion:
Flight conditions will continue to improve areawide as a front
sweeps across the region, ushering in dry air and an end to low
CIGs. Cloud cover has already began to clear along and west of the
MS River and will continue to clear as the dryline pushes
eastward. Some isolated thunderstorms will be possible in east MS
this afternoon and could impact sites in that area. Winds will
remain gusty through the period.
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 46 60 40 65 / 0 23 0 0
Meridian 48 60 36 63 / 0 25 1 0
Vicksburg 46 63 40 65 / 0 14 0 0
Hattiesburg 51 63 41 68 / 0 15 0 0
Natchez 47 64 41 66 / 0 7 0 0
Greenville 47 59 40 62 / 2 25 0 0
Greenwood 46 57 37 60 / 8 31 1 0
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&
$$
Area Forecast Discussion
National Weather Service Jacksonville FL
1000 PM EDT Mon Mar 19 2018
...ANOTHER ROUND OF STORMS TUESDAY...
...SEVERE STORMS POSSIBLE TUESDAY...
.UPDATE...Evening convection has nearly abated Southeast GA and
northeast FL. Severe storms are not forecast overnight. Lingering
showers are over coastal Georgia and over portions of NE FL. These
showers will continue to wane overnight. During the pre-dawn
hours, showers and thunderstorms are expected to enter the
northwest part of the CWA over the far western reaches of interior
SE GA well ahead of an approaching cold front. These storms are
expected to remain below severe limits until mid morning Tuesday.
From mid-morning through late afternoon there will be an enhanced
potential for severe weather. Around early afternoon, storms will
clear interior SE Georgia, with the greatest potential for severe
weather focuses west of Georgia High 301 and across NE FL where
instability will be maximized late morning through mid/late
afternoon with CAPES of 1500-2500 J/Kg with 50 knot LLJ peaking
out between 18z-21z across Northeast Florida where deep layer
shear will be pretty impressive. As a result, a squall line is
expected to develop ahead of the front with isolated embedded
severe thunderstorms. Isolated supercell development is possible
ahead of the front, especially south of I-10 early to mid-
afternoon. Damaging winds, large hail and a couple tornadoes are
all possible with HRRR showing a few good helicity swaths across
the region.
&&
.AVIATION...Expect brief VFR conditions through about 09z, with
stratus at about 700 to 1500 feet until 12-13z. Another round of
showers and possibly strong to severe storms is expected on
Tuesday along and ahead of a cold front, mainly between 16z and
21z, as the region gradually clears out between 21 and 24z.
&&
.MARINE...SW winds 15-20 knots offshore tonight Seas 2-3 ft near
shore and building to 4-5 ft well offshore. A strong cold front
will cross Tuesday afternoon and evening, with showers and storms
ahead of it. The region will be between departing low pressure to
the Northeast and building high pressure to the West Tuesday night
into Thursday. The high will build overhead Thursday night
through Friday.
Advisory criteria conditions will be expected from Tuesday
afternoon through at least Wednesday night.
Rip Currents: Low risk through Tuesday.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 66 79 44 62 / 40 60 0 0
SSI 64 78 50 63 / 30 80 0 0
JAX 67 83 48 68 / 20 80 0 0
SGJ 67 81 49 68 / 30 80 0 0
GNV 67 78 47 68 / 40 80 0 0
OCF 67 80 48 69 / 80 80 0 0
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AM...None.
&&
$$
Cordero/Nelson/Corless
Area Forecast Discussion
National Weather Service Blacksburg VA
949 PM EDT Mon Mar 19 2018
.SYNOPSIS...
Low pressure over the central Plains will cross east over the
Tennessee Valley and central Appalachians on Tuesday. The low
will then deepen off the coast and track northeast Wednesday and
Thursday. High pressure will cover much of the eastern United
States on Friday.
&&
.NEAR TERM /THROUGH TUESDAY/...
As of 940 PM EST Monday...
Shield of rain/convection edging closer to the forecast area,
and starting to see light rain as far east as Wytheville, while
deeper convection remains over Tennessee into Alabama and
northeast Georgia. Latest HRRR and RAP have good handle on this
and look for area of rain to work from southwest to northeast
through the forecast from late this evening into dawn Tuesday,
with average rainfall amounts of a quarter to half inch.
Stable layer seems to hold in place, but cannot rule out a
rumble of thunder making into to the mountains of NC into far SW
VA by midnight. Overall, think temps will stay elevated, but
could drop toward the lower to mid 30s in the Alleghanys late,
with some sleet possible, but nothing of note winter wise until
Tuesday night.
Previous early evening discussion...
Made some changes to the precip forecast this evening as radar
coverage and mesoanalysis showing lack of precip, and forcing,
as area of subsidence passes by per upper vort exiting to the
northeast. Should start to see a ramping up in rainfall after
10-11pm from the southwest as models bring shield of
rain/convection from mid TN into Southwest VA, with better upper
support pushing into the mountains as well.
Previous discussion from early afternoon...
Vorticity advection, isentropic lift and upslope forcing will
all contribute to widespread rain across southwest Virginia,
southeast West Virginia and northwest North Carolina tonight.
Water vapor loop shows a short wave over the Tennessee Valley
which will cross the central Appalachians tonight. Will be
leaning toward the heavier side of the guidance for rainfall
amounts. Clouds and warm air advection will limit temperature
drop tonight. Will use a non diurnal temperature trend for
tonight.
Models continue to indicate the beginning of cooler temperatures
advancing down the eastern slopes of the appalachians late Tuesday.
Otherwise there may a be sleet or snow mixed in with the rain north
of I-64 Tuesday. BUFKIT forecast soundings keep Hot Springs rain
until afternoon with a slow transition to snow in the afternoon.
Surface temperatures may not drop below freezing during the day
so any accumulation before dark will be minimal.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 330 PM EDT Monday...
Guidance seems to have come into general agreement with the complex
synoptic evolution of our midweek weather system. Several surges of
short wave energy will carve out a broad, deep trof which culminates
in a closed low moving across the Appalachians and central mid
Atlantic region on Wednesday. The short wave energy rotating around
the trof will drive development of low pressure that will move up
the Atlantic coast Tuesday night and Wednesday as a surface
reflection of the upper low lingers back to the west over the
mountains, all while a wedge of high pressure lingers east of the
mountains.
As the initial wave Monday night departs to the east early Tuesday,
expect some light lingering precipitation through early Tuesday
afternoon. By Tuesday afternoon expect convection to develop on the
western/southern periphery of the wedge as the upper trof begins to
push over the region from the west. Convective elements will then
ride up over the wedge as the complex structure of surface low
pressure begins to develop. During this time also expect
synoptically induced dynamic cooling to aid thermodynamic cooling
and allow for a transition from rain to snow from north to south and
from high to low elevations, with the possible exception of
locations deeper into the NC piedmont. Snow will then continue
through Wednesday with primary forcing from the closed upper low.
Ptype will become complicated by diurnal effects of heating
especially east of the Blue Ridge and at lower elevations and wet
snow conditions may not be very efficient at accumulating. The event
will gradually taper off as the upper low slowly pulls off to the
east Wednesday afternoon/night and lingering upslope snow showers
diminish by Thursday morning.
The end result will be several inches of wet snow across the region
Tuesday night through Wednesday with greater amounts west of the
Blue Ridge and at higher elevations, and lower amounts further to the
south and east. Currently leaning toward thermal profiles which would
more favor sleet as a mixed ptype than freezing rain during the
transition Tuesday night mainly north of Interstate 64 but this is a
fine line and will be monitored closely. While confidence remains low
in specifics, there is enough certainty in potentially impactful winter
weather to warrant the issuance of a winter storm watch for locations
along and west of the Blue Ridge from Tuesday night through Wednesday.
This watch may be adjusted in timing and/or coverage, and some
locations may eventually transition to a warning or advisory.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 330 PM EDT Monday...
A large ridge being undercut by southern stream energy and moisture
will move across the eastern US into the first part of next week.
This will keep our weather active through Monday.
After a brief break of fair weather on Friday, a warm front
extending from low pressure in the midwest will begin to push
precipitation back into the region Saturday. Temperature profiles
point to the possibility of wintry precipitation especially from the
Blue Ridge west through Saturday night. Solutions then start to
diverge with the possibility of the frontal boundary and wedge
lingering over the region with precipitation through the weekend, or
possibly a brief break on Sunday before the next wave brings
precipitation back for Monday. Will blend solutions to find a
compromise, but the main point is to expect unsettled conditions
into the first part of next week with temperatures generally below
normal.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
As of 715 PM EDT Monday...
Should see VFR early this evening, then shield of rain moves in
from southwest to northeast from 02z to 07z, with cigs/vsbys
sinking into MVFR to IFR range, then more IFR before 12z as
column saturates.
Rain should be moderate to heavy at times, but no thunder
expected.
Models are showing break in precip coverage during the late
morning into early afternoon as one area of lift pushes north
into PA/MD and next shortwave moves into mid TN. This next
system will bring more precip back to the area late in the day,
but overall despite the break low level moisture remains so IFR
to MVFR cigs and some MVFR vsbys stay around.
Any winter ptype will hold off until after 00z Wed at the taf
sites, but could see some snow mixing in toward the end at LWB.
Confidence is medium through the period.
Extended Aviation Discussion...
As a low pressure system heads offshore Tuesday night,
precipitation wrapping along the western periphery of this
system is expected to change to snow. This will result in
MVFR/IFR conditions, and gusty north to northwest winds Tuesday
night and Wednesday. Drier air should finally result in
improving conditions Thursday as high pressure builds from the
northwest. Another low pressure system will bring rain and the
associated MVFR or lower conditions for Friday and Saturday.
&&
.EQUIPMENT...
As of 335 PM EDT Monday...
The Mount Jefferson NWR remains off the air. The radio unit
needed to repair the system is expected to arrive on Wednesday.
The earliest this system will again be operational will be
Wednesday afternoon.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Winter Storm Watch from late Tuesday night through Wednesday
evening for VAZ007-009>020-022>024.
NC...Winter Storm Watch from late Tuesday night through Wednesday
evening for NCZ001-002-018.
WV...Winter Storm Watch from late Tuesday night through Wednesday
evening for WVZ042>044-507-508.
&&
$$
SYNOPSIS...AMS
NEAR TERM...AMS/WP
SHORT TERM...MBS
LONG TERM...MBS
AVIATION...AMS/PM/WP
EQUIPMENT...AMS