Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/23/19
Area Forecast Discussion
National Weather Service Amarillo TX
654 PM CDT Thu Aug 22 2019
VFR conditions are expected through the 00Z TAF period. Latest
radar trends shows mostly clear conditions expected through the
overnight period. Winds will range between south and southeast at
5-15 kts. VCTS conditions are possible starting around 18Z through
to the end of the TAF period. Better timing of thunderstorms for
tomorrow afternoon will be illustrated in future TAF updates.
.PREV DISCUSSION... /Issued 327 PM CDT Thu Aug 22 2019/
SHORT TERM...This Evening through Friday Afternoon..
Latest mid level water vapor imagery reveals shortwave trough and
associated moisture field crossing into western OK and central KS.
Drier and more subsident air is advancing east into the Panhandles
in the wake of the shortwave. As mid level clouds exit the
Panhandles, temperatures have started to rise into the mid 80s with
dew points near 60. Visible satellite shows two cumulus fields, one
in southwest zones and one in northeast zones. If temperatures can
recover into the low 90s, an isolated thunderstorm can`t be ruled
out as MLCIN starts to erode. However, the weak subsidence aloft and
drier air aloft should keep coverage limited, if anything can form
at all. Given these concerns, went slightly below previous forecast
and NBM with slight chance PoPs across most of the area. If a storm
does develop, progged soundings suggest 700 to 1200 SBCAPE in a low
shear environment. High bases and DCAPE of 1000 to 1500 J/kg will
still promote a strong wind gusts potential.
For tonight, will have to watch convection coming off the higher
terrain of NM/CO. Most of the CAMs suggest this activity will
dissipate before making it into the Panhandles, but the RAP
indicates a subtle 500mb wave that may have enough lift to carry
storms into the area overnight. These would likely be elevated with
some gusty winds and brief heavy rain if they do make it into the
area. Otherwise, expected low temperatures mainly in the mid 60s.
For tomorrow, a much more notable upper level trough will cross
central Rocky Mountains. There is decent agreement in the raw
guidance showing a leading shortwave as 500mb winds shift to the
northwest through the afternoon. Low level theta-E advection will
increase as a lee surface trough develops near the TX/NM state line.
A few storms could develop along and east of the surface trough
within a 700mb theta-E axis in the western zones Friday afternoon.
Moderate instability (1000 - 2000 J/kg) and better effective shear
(20-30 knots) will support a few stronger storms especially going
towards the evening hours in the northwestern zones.
LONG TERM...Friday Night through Wednesday Night...
Broad scale high pressure off the western coast will provide
northwest flow to the Panhandles. Lee surface low is expected to
develop across SE Colorado and track a bit east. Best area of
convergence looks to be along the NM/TX border where storms can pop
up, and track east along a subtle wave embedded in the northwest
flow. Storms may start out discrete, but then merge into a line,
and could very well impact all the Panhandles. ML CAPE values in
the 1000-2500 J/kg range along with marginal shear and helicity
would support strong to severe storms tomorrow night. Hail and wind
will be the primary threats, with more wind after the storms line
Another round of storms will be possible on Saturday as the lee low
shifts further east, the drier air will be in place through the
Amarillo/Guymon line. Areas to the east will still have the chance
for storms. Again, high CAPE and shear values just east of the main
dryline convergence could support strong to severe storms on
Saturday as well.
Sunday, upper level high shifts a bit east, as well as the lee
surface low, and most of the Panhandles should be dry, other than
some potential lingering storms in the morning. Temperatures will
be hot and dry with most areas reaching and likely exceeding 100
degrees again. The heat stretch will be short lived as a weak cold
front is expected, bringing the temperatures back into the 90s for
Monday. The southwest could still hold onto low 100s.
Cutoff low over the Great Lakes associated with this cooler air
will merge with another low over south central Canada and provide a
stronger surge of cooler air. There is still a potentially decent
850mb temperature gradient (10C) from SW/NE, but for now will not go
astray from the blends.
As the trof amplifies over the Great Lakes and Midwest late in the
week, the upper level ridge will slowly shift back towards the four
corners. Surface high will shift over the southeast MO area and
start to push moisture back to the Panhandles from the southeast.
This could set up an interesting profile given the potential low
level jet setup from the south and then decent mid level northwest
flow on the lee of the upper level ridge. High surface moisture,
very good turning, and decent ML CAPE values could lead to some
interesting evening/nighttime storms on Tuesday. Still uncertain if
we will have a trigger for these storms given the loss of daytime
heating when all these ingredients come into play.
Keeping an eye out for possible strong cold front with storms to be
associated on Wednesday night, right now too far out and too many
model discrepancies to have confidence.
AVIATION...18z TAF Cycle:
VFR conditions are expected through the period. Confidence in
storm impacts for any given TAF site has decreased, so have left
mention out of TAFs. There is still potential for isolated storms
to develop, but at this time the higher chance is east of the
terminals through the early evening hours. Will amend TAFs if
storm activity does develop further west. Some storms may try to
move out of NM later in the evening and overnight, so the next
forecast update may need to address this. Winds should be
generally be out of the south at 5 to 15 knots.
Area Forecast Discussion
National Weather Service Boston/Norton MA
952 PM EDT Thu Aug 22 2019
A cold front moves across Southern New England overnight, then
stalls just off the South Coast. A wave of low pressure then
moves along the front and close to the region. Scattered
showers and embedded thunder may impact much of CT/RI and
Southeast MA through Friday morning. The front moves farther
offshore Friday afternoon with drier and less humid weather to
follow. Canadian high pressure then provides dry weather
Saturday with a mild afternoon and cool night. Onshore flow
Sunday will yield cooler conditions along with a few showers
possible. Cool weather likely lingers into early next week.
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Cold front has moved into Northern MA. Position of the front is
well indicated by dew points. Dew points at 9 pm in CT-RI-SE MA
were 70 to 75 (oppressive humidity) while values at Pittsfield,
North Adams, Orange, Fitchburg, and Lawrence were in the mid to
upper 50s. Radars show showers over NYC and SW CT moving east.
This batch is mostly a concern of our South Coast areas from
around 1130 PM to 230 AM.
SBCAPE from the SPF RAP shows 500-1000 J/Kg lingering over CT-
RI-SE MA through midnight, then diminishing. This should support
the showers moving across from NYC.
Synoptic support increases later tonight as Canadian upper
trough swings south, and our area moves under the right entrance
region of the supporting upper jet. PW values are forecast
around 2 inches overnight, supplying moisture for clouds and
We will continue to show an area of scattered showers/thunder
developing overnight along and south of the cold front, mainly
areas south of the Mass Pike.
Min temps will be highly dependant on the dew points. South of
the front temps and dews will linger in the low to mid 70s.
North of the front we expect temps to fall into the 60s, except
mid to upper 50s along the Berkshire east slopes and parts of
Northern Worcester County.
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
4 PM update ...
Showers with embedded thunder and heavy rain possible during the
morning across CT-RI and south of the MA pike, especially south
coast of RI/MA. For what it`s worth the new 12z EC has trended
slower with the departing rain shield, however all guidance
including the CAMs support a drying trend in the afternoon along
with sunshine developing from northwest to southeast.
Should turn out to be a nice afternoon with highs in the upper
70s to lower 80s (seasonable for late Aug) but very comfortable
humidity with dew pts falling into the upper 40s and lower 50s!
Friday night ...
Dry post frontal airmass overspreading the region with a cool
north drainage flow. Thus leaned toward the cooler guidance with
lows in the 50s regionwide, upper 40s for NW MA and around 60
for the big city of Boston.
.LONG TERM /SATURDAY THROUGH THURSDAY/...
4 PM update ...
* Mild temperatures and dry conditions Saturday
* Cooler than normal temperatures expected Saturday through Monday,
with spotty light rain or showers at times
* Temperatures moderate by mid week, with another chance for showers
Tuesday through Thursday
Saturday and Sunday...
The weekend looks overall pleasant and cooler, with a very
comfortably dry airmass in place. A large area of high pressure at
the surface moves east from southern Canada into northern New
England and remains anchored there through the weekend. While some
lingering weak troughing and cold pool aloft remain, high pressure
and an especially dry column should keep rain chances to a minimum.
Best chance of some showers will be on Sunday as moist low level
advection increases on north easterly flow which could allow for
some shallow showers...can`t rule out a pop up shower for most of
the region but the best chance would be along the south and east
coasts and coastal plain. Speaking of northeasterly flow around that
surface high, the pressure gradient tightens on the southern end,
bringing gusty northeast winds on Sunday (and to a lesser extent
on Monday), mainly along the south coast into Cape Cod where
winds could gust to 25-35 mph.
Comfortable conditions both days under a deep cold pool. H85 temps
down around 6-8C will support below average high temperatures in the
70s each day...60s along the east coast on Sunday given increased
onshore flow. Dewpoints remain comfortable in the 50s.
Monday through Thursday...
Monday looks to remain mostly dry with continued influence of high
pressure and only a slowly moistening atmospheric column. Winds
along the south coast remain gusty but start coming down. It`s not
until Monday night/Tuesday that we really see signs of a warm
frontal feature ahead of two incoming low pressure systems...one
moving from the Great Lakes into Canada, and another potentially
approaching southern New England up the east coast. High degree of
uncertainty on how these features play out and interact with each
other, but the general idea will be increasing moisture as dewpoints
surge back into the upper 60s Tuesday, into the 70s by Wednesday
into late week. Overall an unsettled pattern with at least periodic
rain chances Tuesday through Thursday as several frontal boundaries
and shortwaves move through. Not much instability for thunder, at
least through mid week given cool northeast flow. Temperatures
remain a bit below normal Tuesday, in the 70s, before rebounding
into the low 80s by mid-late week as warmer subtropical air is
pulled up the coast downstream of the trough.
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Friday Night/...Moderate confidence.
Mainly dry initially. VFR-MVFR cigs/vsbys moving into CT-RI-SE
Mass 03Z to 06Z. Isolated thunder possible. Mainly VFR and dry
north of the MA pike.
Showers in MVFR-VFR possible during the morning across RI/CT and
southeast MA, especially along the south coast and Islands.
Otherwise trend will be for VFR, dry weather and NW winds.
VFR, dry weather and northerly winds.
KBOS Terminal...High confidence in TAF
KBDL Terminal...High confidence in TAF.
Outlook /Saturday through Tuesday/...Moderate confidence
Saturday Night: VFR. Breezy. Slight chance SHRA.
Sunday through Sunday Night: Mainly VFR, with local MVFR
possible. Breezy. Slight chance SHRA.
Monday: Mainly VFR, with areas MVFR possible. Breezy. Chance
Monday Night: Mainly VFR, with local MVFR possible. Breezy.
Slight chance SHRA.
Tuesday: VFR. Breezy. Slight chance SHRA.
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Friday Night/...High confidence.
Tonight ... Scattered showers and isolated thunder especially
11 PM to 2 AM along the southern waters. Additional showers
arrive on most waters after 2 AM. SW winds slowly shifting to
NW as a cold front stalls over the southern waters. Seas
lingering at 5 feet south of Block Island, but expected to
diminish. We will continue the Small Craft Advisory to 2 AM.
Friday ... Scattered showers with isolated thunder and heavy
downpours possible in the morning, then trending drying in the
afternoon from NW to SE.
Friday night ... Cold front offshore with WNW winds and dry
Outlook /Saturday through Tuesday/...Moderate confidence.
Saturday: Winds less than 25 kt. Seas locally approaching 5 ft.
Saturday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Slight chance of rain showers.
Sunday: Moderate risk for Small Craft Advisory winds with gusts
up to 30 kt. Seas up to 5 ft. Slight chance of rain showers.
Sunday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers.
Monday: Moderate risk for Small Craft Advisory winds with gusts
up to 25 kt. Seas up to 5 ft. Chance of rain showers.
Monday Night: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers.
Tuesday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft. Slight chance of rain showers.
MARINE...Small Craft Advisory until 2 AM EDT Friday for ANZ254>256.
Area Forecast Discussion...Updated
National Weather Service Billings MT
926 PM MDT Thu Aug 22 2019
Cold front was about to move into Rosebud County at 0230Z per
surface obs. Inverted trough was over E. Sheridan, Powder River
and SW Custer Counties. Thunderstorms that moved through Billings
area earlier did have hail up to golf ball size and accompanying
damage. Two areas of storms remained. One was a line over SE MT
oriented N to S in the trough. The other was N of KBIL in post-
frontal regime just ahead of upper trough. A few other storms
were moving NNE through Big Horn County. PWAT`s were over an inch
in SE MT with ML CAPES of 1000-1500 j/kg. Wind shear continued to
be minimal in the SE. Given the above, the threat for severe
weather continued N and E of Billings. Latest RAP had good handle
on precip. placement so adjusted nighttime PoPs toward this
model. HREF showed precip. dissipating late tonight over the E,
but approaching upper trough will generate more convection over
western areas. Temps looked reasonable. Adjusted winds toward
ADJLAV which had good handle on speeds. Arthur
.SHORT TERM...valid for Fri and Sat...
Trough was approaching from the west with a low developing at the
surface, while an associated cold front moved through western
areas this afternoon. Ahead of the front, southeast winds were
gusting to around 40 mph near the Dakotas border. The cold front
will continue to push east through the evening with showers and
thunderstorms developing over the southern mountains and moving
off onto the plains, while another area of focus for thunderstorm
development will be an area of convergence over eastern areas.
Some of the thunderstorms could be strong to severe over the area
with good instability, but marginal shear. Best chances for strong
thunderstorms will be generally east of Billings. Main threats
will be strong wind gusts, hail, and heavy rainfall with PWATs
approaching 1.50 inches. Showers and thundestorms will linger
overnight as the aforementioned trough and associated low move
overhead, and upslope flow continues at the surface.
Shower and thunderstorm chances are greatest over the southern
mountains and foothills on Friday as the trough continues to slide
east. A strong storm is possible over far southeast Montana.
Overall drier conditions can be expected for Saturday, but a weak
wave moving through the region in northwest flow will bring shower
and thunderstorm chances to the area during the evening. High
temperatures behind today`s cold front will be mainly in the 70s
on Friday, with highs warming into the 80s for Saturday. Low
temperatures mainly in the 50s are forecast through the short
.LONG TERM...valid for Sun...Mon...Tue...Wed...Thu...
Generally zonal flow aloft will veer to west-northwest through
the day Sunday, but remain dry through the day. Highs around 80
degrees are expected for Sunday.
A cold front will shift across the region Sunday evening/night
shifting flow aloft to northwest, and bringing precip potential
across the region into Monday. Activity should clear out by
Monday afternoon. This wave will start the extended period of
cooler weather from Monday through Thursday, with temps solidly
in the 70s, and a nice break to recent hot stretch. Ensembles
appear in good agreement that a drier Northwest flow will persist
through this cool period as well. One caveat is that there are
several waves moving through the flow, which point to some shower
activity through the day Tuesday. Overall atmospheric moisture
availability seems pretty limited, but boundary layer moisture
may be enough to support some shower/thunderstorm activity.
The operational ECMWF swings another wave across the region to
end the period, bringing potential for isolated showers to end the
work week. Have carried some slight pops for this period, but is
quite a ways out at this point.
Showers and thunderstorms will continue over the area overnight,
mainly east of KBIL. MVFR/IFR conditions are expected in the
storms with heavier rainfall. There will be areas of mountain
obscuration. Gusty SE surface winds will continue over KMLS. Ceilings
will lower over much of the area late tonight to MVFR/IFR. Low
ceilings will continue into Friday morning. Most areas will
improve Fri. afternoon. Scattered showers and thunderstorms are
expected over the area on Friday with areas of mountain
obscuration. Expect MVFR/IFR conditions in thunderstorms, mainly E
of KBIL. Arthur
.PRELIMINARY POINT TEMP/POPS...
Fri Sat Sun Mon Tue Wed Thu
BIL 060/079 060/089 059/080 052/076 052/076 050/075 050/075
33/T 11/B 31/U 21/U 12/W 21/U 11/B
LVM 051/079 053/085 050/078 045/076 045/076 043/075 043/076
52/T 11/B 20/U 11/U 12/W 21/U 11/B
HDN 060/077 057/087 057/078 051/074 049/075 048/073 047/074
33/T 11/B 31/U 22/U 11/U 21/U 11/B
MLS 062/078 059/087 059/077 052/073 050/073 048/070 047/070
52/T 21/B 31/U 22/U 12/W 21/U 11/U
4BQ 060/078 056/086 058/078 050/073 049/073 047/070 046/070
53/T 41/B 32/R 32/U 12/W 21/U 12/W
BHK 062/080 056/085 057/076 050/071 047/072 045/069 044/068
32/T 32/T 43/R 22/U 12/R 21/U 11/U
SHR 056/076 053/087 055/078 047/073 046/075 045/072 044/073
26/T 31/B 22/R 32/U 12/W 21/U 22/W
Area Forecast Discussion
National Weather Service Louisville KY
949 PM EDT Thu Aug 22 2019
Issued at 945 PM EDT Thu Aug 22 2019
Lowered POPs overnight as the latest CAMs indicate only isld-sct
coverage of showers and storms during the overnight period. Low
temps in the upper 60s/lower 70s still look on track.
.Short Term...(This evening through Friday)
Updated at 243 PM EDT Thu Aug 22 2019
Storms are firing up along a remnant outflow boundary in southern
Kentucky from convection earlier in the morning. Storm motions are
nearly parallel to this boundary, and as a result, we`ve seen some
localized high rainfall amounts and potential minor flood issues due
to training storms. The good news is that in some of the more recent
low level radar scans from KHPX/KOHX, the outflow boundary the
storms fired along is beginning to outrun the convection, which has
helped to taper down the training convection threat as storms weaken
behind the cold pool.
Additionally, there is a low threat for severe weather near the Lake
Cumberland region this afternoon. This part of the region has
remained partly cloudy to mostly clear for a good part of the day,
which has allowed the environment to become unstable and fuel
developing storms. So far, storms have remained below severe limits,
and generally expect them to remain sub-severe as we move through
the rest of the afternoon, but can`t rule out a marginally severe
storm developing. Gusty winds and small hail will be possible in the
Another line of showers and storms currently along the western TN/KY
borders will move into south-central Kentucky over the several
hours. There`s a bit of uncertainty regarding how this line will
evolve as the current convection in south-central Kentucky may
stabilize the atmosphere ahead of it. Recent runs of the HRRR
suggest it might hold together through the BWG metro area before
gradually weakening as it approaches the Lake Cumberland region. The
line in western KY/TN isn`t moving particularly fast, but if it
becomes cold pool dominant it might speed up a bit and lower any
potential flood threat.
As we move into the overnight hours, models indicate the potential
for another wave to move through, but vary on the timing and
placement of the precipitation axis. Meanwhile, a cold front will
begin dropping in from the north, and slowly push through southern
Indiana late tonight, and then central Kentucky tomorrow morning.
Chances for showers and occasional storms will persist through the
morning, but it appears that by the afternoon we may begin to see
some clearing in southern Indiana and perhaps northern Kentucky.
Highs will generally stay in the low to mid 80s due to the abundant
cloud cover and shower coverage.
.Long Term...(Friday night through Thursday)
Updated at 255 PM EDT Thu Aug 22 2019
Cold front and associated precip will be pushed south into the
Tennessee Valley Friday evening, giving a taste of early fall for
much of the weekend. Temps will run solidly below normal through the
first part of Sunday, with Saturday highs just either side of 80 and
lows Sunday morning dipping into the 50s across most of the area.
Dewpoints will run in the 50s, certainly atypical for late August.
By Sunday afternoon we`ll see an inverted sfc trof ahead of an upper
impulse trying to undercut a blocking ridge, and precip chances will
ramp up across south central Kentucky. Scattered storms will expand
across the Ohio Valley Monday and Tuesday as the Great Lakes ridge
gives way to a series of upper troughs coming out of the Plains.
Deep closed low over NW Ontario will help to push a front through
the Ohio Valley, perhaps as soon as Tuesday night, which would
support a drying trend Wed-Thu. However, confidence is limited so
consensus leaves us with low chance POPs during the middle of next
week. Below-normal temps will continue, but with warmer nights and
slightly higher dewpoints.
.Aviation...(00Z TAF Issuance)
Updated at 740 PM EDT Thu Aug 22 2019
Forecast problem of the day is a slow moving frontal boundary over
the area. Attempted to time the precipitation occurrence at each TAF
site. Overnight looking for showers, with isolated thunderstorms
possible. A better chance for thunderstorms Friday afternoon. We can
look for periods of MVFR ceilings at SDF, HNB and LEX. Light and
variable winds will become more northeast Friday morning, with wind
speeds 4 to 5 knots Friday afternoon.
Area Forecast Discussion
National Weather Service Morristown TN
904 PM EDT Thu Aug 22 2019
Scattered showers and thunderstorms continue this evening with
greatest coverage across the central valley and mountain
foothills. According to RAP forecast analysis, this is in a
location of low-level convergence and upper-level divergence. A
weak jet streak and diffluent flow aloft is resulting in upper
divergence supporting deep lift with a converging 850mb flow of
about 20 kt. This is expected to shift northeast overnight with
near term guidance suggesting the 850mb flow increasing. This will
result in greater boundary layer convergence across NE TN and SW
VA between 09z and 12z Friday. The severe weather threat appears
very low, but a few thunderstorms could have gusty winds with
850mb flow forecast to be near 30 kt. The main hazard will be
heavy rainfall which may result in isolated flash flooding
concerns late tonight and early Friday morning across NE TN and SW
VA. PW values will be high, near 1.9 inches which is near the max
of climatology for this area, and flow will be nearly parallel to
the southward moving frontal boundary approaching the region later
Friday. Numerous showers and thunderstorms are expected on Friday
ahead of this frontal boundary with greatest coverage across the
northern two-thirds of the forecast area.
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 73 89 72 88 / 50 60 40 70
Knoxville McGhee Tyson Airport, TN 71 86 69 86 / 60 60 50 50
Oak Ridge, TN 72 86 68 86 / 50 60 40 30
Tri Cities Airport, TN 69 82 65 81 / 60 70 50 40
Area Forecast Discussion
National Weather Service Blacksburg VA
1132 PM EDT Thu Aug 22 2019
A cold front moves south into the region Friday. By Saturday,
the front will extend from the Carolinas to the southern Plains.
Cooler high pressure will build into the Mid Atlantic region
Sunday and Monday.
.NEAR TERM /THROUGH FRIDAY/...
As of 1123 PM EDT Thursday...
Have lowered pops as we head into early overnight throughout
most of the region. Exception will be area of moisture
convergence along an instability axis in Northeast TN into
Western NC that seems to staying active as it edges closer to
the NC High Country. Near term models suggest at least 50/50
threat of this stuff holding on into early morning so have pops
around 50-60 percent in the far southwest. These showers/storms
may fade toward 3am, before another batch arrives ahead of a
shortwave moving across KY by dawn into the WV and far SW VA
mountains, aided by approach of front to our north.
Increasing clouds should maintain less dense fog tonight, but
patchy fog appears likely given the storms we had earlier.
Previous discussion from early evening...
Have finally seen showers/storms weakening early this evening
with main axis of instability and deep moisture convergence
pushing east toward the Tidewater. Another area of showers,
maybe a few storms arrives later this evening in the mountains,
but as high-res models are keeping things in a weakened state,
not strong storms expected. Will reduce pops as radar and models
trends favor a drier evening over most of the forecast area,
with a blend toward slight chance of showers east late, with
better chance in the mountains.
Previous discussion from early this afternoon...
Scattered showers and thunderstorms in the mountains will spread
east this afternoon into tonight. Some of the storms will be
severe containing damaging winds, hail and heavy rains.
These storms were initially generated by an outflow boundary from
the Tennessee Valley heading east. The leading edge of this
cold pool will advance eastward around 25 kt, and will be the
one focus for thunderstorm activity. In addition, the
combination of instability, orographic lift, convergence and low
level boundaries will generate additional showers and thunderstorms
this afternoon into this evening. The HIresw-arw-east, HRRR and
NAMnest showed convection spreading east between 21z-00z.
Coverage and strength of storms will increase into this
evening, then decrease. SPC 18z Mesoscale analysis indicated
CAPES from 2000 to 3500 j/kg in the east with surface based LIs
minus 2 to minus 5. The best bulk shear will be to our north of
A cold frontal boundary to our north will slowly drop south and will
reach central West Virginia to northern Virginia late tonight into
Friday. Scattered showers and thunderstorms will diminish with
the loss of solar heating this evening into tonight. Late
tonight into Friday morning, additional storms will move into
the western mountains. The combination of light winds and low
level moisture will result in areas of low clouds and fog. Low
temperatures tonight will range from the upper 50s in the
mountains to the lower 70s in the piedmont.
A southward-sagging, west-east oriented cool front will interact
with poorly-defined vort maxima and lead to scattered showers and
thunderstorms Friday into Friday night. Some of the storms will be
strong to severe with damaging winds, hail and heavy rains. The
SPC Day Two convective outlook highlights a marginal risk for
eastern portions of our forecast area Friday, given the effective
shear values. High temperatures Friday will vary from the upper
60s to the mid 80s in the piedmont.
.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 300 PM EDT Thursday...
The frontal boundary will continue to drop south into
Friday night. A weak surface wave low/mesolow overnight Friday
into early Saturday may briefly stall the front`s southward
progress. This suggests opening with high PoPs on Saturday
morning at least to Southside seems realistic, lower PoPs north.
Northerly/northeast flow on the cool side of the front and rain
falling on the south side of the frontal zone should help shift
the front`s position into north- central NC toward Saturday
afternoon with falling PoPs toward slight chance or dry.
Biggest forecast challenges Saturday are timing the front`s
passage into central NC, and on temperatures due to variation in
cloud cover. To the latter point, cooler/drier air should
filter in on the northeast flow, with lowering dewpoints to much
more comfortable levels. Saturday night into Sunday will have
.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 300 PM EDT Thursday...
Outset of the long-term period will see a slow-moving frontal
boundary to our south across the Carolinas with a sprawling surface
ridge building across the Great Lakes and into the northeast. The
bulk of the heaviest rainfall associated with this frontal boundary
should be suppressed mainly to our south and east but portions of
southern CWA will likely see lingering showers and storms into the
day Saturday. A much cooler and drier period appears to be in store
for the second half of the weekend and into early next week. Highs
will be 10 to 15 below what has recently been experienced with daily
highs in the 70s or even upper 60s and overnight lows will be 50s
west to low 60s east. Will certainly feel different. The surface
high will shift north and east toward mid-week with increasing
southerly flow and warmer temperatures along with renewed chances
for mainly afternoon convection. An approaching front toward mid- to
late late week will possibly trigger a few stronger thunderstorms in
an increasingly warm and unstable air mass. A trough of low pressure
currently along the FL coast has been given a 30 percent chance of
tropical storm formation near the SC/NC coast in the latest NHC 5-
day outlook but impacts on the local weather look to be negligible
or minimal at this writing.
.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
As of 715 PM EDT Thursday...
Have low confidence in this forecast as models are varying on
low cloud/fog formation late tonight while next batch of showers
moves into the mountains toward 08-12z. With some clearing and
wetter ground may see fog to MVFR/IFR at most places with MVFR
cigs, and possibly IFR cigs in the mountains.
More showers and thunderstorms will be approaching the central
Appalachians from the west Friday morning which may lower
ceilings to MVFR at KLWB and KBLF. As the cold front approaches
from the northwest on Friday, scattered to numerous MVFR
showers and thunderstorms will develop. Will aim for better
threat of this east of the mountains Friday afternoon.
Confidence on critical parameters is low tonight but higher
toward late morning into the afternoon.
.Extended Aviation Discussion...
Weather pattern will continue to promote scattered showers and
thunderstorms. A cold front will approach from the northwest
Friday evening into Saturday, resulting in scattered to
numerous thunderstorm with potential for organized clusters of
thunderstorms to track across the Ohio Valley into the Mid-
Improving conditions with more in the way of VFR will be
possible for Sunday, pending just how far south of the Mid
Atlantic area the front progresses. Some MVFR showers are
possible in the southwest Virginia and northwest North Carolina
on Monday. Scattered showers and thunderstorms are expected