Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/06/20
AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
909 PM EDT Tue May 5 2020
Low pressure developing over the Carolinas will track to the
south of the local area overnight before pushing offshore by
Wednesday morning. A trough of low pressure will swing across
the area later Wednesday afternoon into Wednesday night. High
pressure will build into and across the region during Thursday.
Another cold front will cross the region on Friday and Friday
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of 905 PM EDT Tuesday...
Late evening surface analysis shows ~1006 mb sfc low pressure
centered from WV to to the mountains of VA/NC. A secondary low is
starting to develop in srn NC/nrn SC along a stalled frontal
boundary. Aloft, a trough over the Great Lakes is slowly propagating
east-southeastward toward the area. E-NE flow prevails across
the area on the north side of the boundary with temperatures
mainly in the 50s (dew points in the 40s-low 50s). It is mainly
dry at this hour, with a just a few showers streaming across the
area. Still expecting showers to increase in coverage and
spread across the area from W-E overnight (mainly after
midnight). Pcpn chances lower from W-E during the 09-12z
timeframe (except in the NE third of the CWA). Mainly minor
changes were made with the evening update, although near-term
CAMs (namely the last couple HRRR runs) have backed off somewhat
regarding the potential for tstms across srn portions of the
area overnight. Not enough confidence to remove thunder from the
forecast (am seeing isolated elevated tstm development across
NW/north- central NC on the cool side of the front). As such,
will maintain slight chc thunder across srn VA/NE NC. QPFs
through 12z range from 0.15-0.50" (highest E/lowest W).
Previous Discussion as of 300 PM EDT Tuesday:
The first wave of light rain associated with weak isentropic
lift/warm advection has generally moved offshore. More showery type
precipitation mainly west of the area will spread east tonight
as the upper trough moves east. More focused precipitation is
expected this evening across southside VA and NE NC as the
secondary surface low develops and moves offshore overnight. In
fact, could not rule out a thunderstorm across the far southern
tier this evening into the early morning hours due to the very
steep lapse rates aloft and MUCAPE values of nearly 1000 J/KG.
As such, have maintained the slight chance of thunder mainly
along/south of US 460 tonight. With the steep lapse rates and
subsequent CAPE profile as well as the 40- 50kt of deep shear,
one could not completely rule out hail if there is any storm
organization tonight however this would likely occur south of
the area in SPCs marginal/slight risk area co-located closer to
the surface boundary.
Showers will also spread across the rest of the area once again
tonight simply due to the upper trough approaching and subsequent
height falls, especially as the surface ridge centered just
offshore moves northeast. Will therefore maintain likely or
categorical pops for the rest of the area overnight. Lows will
drop into the mid 40s NW and MD eastern shore to low-mid 50s SE.
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
As of 300 PM EDT Tuesday...
Unsettled weather continues on Wednesday with the upper trough
moving overhead and the surface low just offshore. Although the
morning may be relatively dry as a weak dry slot moves across the
area, will see increasing shower coverage especially across the
north during the afternoon as the cold pool aloft (500mb temps
around -22c) moves overhead and we some some diurnal heating. In
fact, it would not be completely surprising to hear of small
hail/graupel with any shower activity Wed afternoon. Will
therefore maintain likely PoPs across the north Wed, with chance
PoPs to the south where there will be less influence from the
upper trough. Highs will be unseasonably cool again, with temps
in the upper 50s north and mid-upper 60s south with a little
High pressure finally builds in eventually by Thursday morning,
although there continues to be chances for showers especially
Wednesday before the upper trough axis moves offshore. Thursday will
be Mostly Sunny though as the surface ridge builds in from the west
and W-NW flow develops. Lows Wed night in the 40s (with upper 30s
NW of RIC). Highs Thursday in the 60s.
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 300 PM EDT Tuesday...
The cool pattern will continue into early next week at least. After
a quiet Thursday, another cold front and upper trough will approach
the east coast Friday. This will bring another round of light rain
to the area especially Friday afternoon/night as a weak low
moves up the Appalachians along the front. Behind this front,
unseasonably cool conditions will move into the area with GFS
500mb height anomalies 2-3 standard deviations below normal
across the Middle Atlantic. This will yield highs only in the
50s on Saturday but rebounding into the low-mid 60s on Sunday.
Increasing chances for a frost or even a freeze Sun morning
especially west of I-95 but even as far east as the interior
coastal plain. In fact, the NBM V4.0 10th percentile min temps
Sunday morning are in the upper 20s/lower 30s across much of the
area away from the coast so this will need to be watched very
closely in the coming days.
Heights remain below normal through mid week. Could not rule out a
stray shower on Monday with another weak frontal passage but for now
will keep dry or just slight chance of showers. Temps for
Monday/Tuesday will stay in the 60s with lows in the 40s.
.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
As of 755 PM EDT Tuesday...
High pressure is centered a couple hundred miles off the nrn
Mid-Atlantic coast as of 23z and is ridging southwestward into
SE VA/NE NC. Meanwhile, weak low pressure is centered over the
mountains of WV/VA. A secondary low is developing over srn
NC/nrn SC. Dry conditions prevail at the terminals at this
hour, with scattered light-moderate SHRAs approaching SBY from
the W. As the secondary low tracks ENE through NC/moves closer
to the area tonight, showers will develop and overspread the
terminals from 02-05z and persist through much of the night.
Pcpn is expected to end from W to E during the 08-11z
timeframe. CIGS are still VFR/high-end MVFR at the terminals
this evening, but are expected to lower to MVFR before dropping
to IFR from SW to NE early Wed AM (mainly after 06z). Cannot
rule out a rumble of thunder at ORF/ECG overnight but confidence
in this is low. Latest guidance has actually backed off a bit
with respect to thunder potential. CIGS rise to MVFR/VFR at the
VA/NC terminals by late morning-midday Wed as winds increase
out of the NW and some low-level drying occurs. At SBY, IFR CIGs
likely persist through much of the day as the low-level flow
remains N-NE and showers continue.
Expect re-development of scattered showers Wed aftn at the
remaining terminals (best chc at RIC/PHF) as an upper trough
and cold front push through the region. VFR conditions prevail
at RIC Wed night but CIGS could remain MVFR near the coast as
clouds/isolated-scattered showers persist. Dry and breezy
conditions develop Thursday with a NW wind in the wake of the
cold front. Another chc of showers arrives Friday aftn/evening
with another cold front. Dry and breezy again Saturday with a NW
wind in the wake of the second cold front.
As of 345 PM EDT Tuesday...
Afternoon surface analysis shows low pressure over eastern TN/KY
while weak surface high pressure near the local area slips offshore.
Winds vary considerably across the waters this afternoon with
generally light and variable winds across the northern half of
the area with 10-15 knot onshore flow in place across the
southern half. Waves are 1-2 ft with seas 2-4 ft offshore.
Low pressure will develop across the Carolinas and translate
eastward overnight tonight. Onshore flow increases 15-20 knots for
the southern coastal waters with generally 10-15 knot easterly winds
in the southern bay and lower James river tonight. Enhanced (but
sub-SCA) onshore winds will spread northward across the coastal
waters through sunrise as the low emerges into the Atlantic.
This low will strengthen modestly tomorrow morning while taking
a more NE track offshore. Winds turn to NW as the low pulls away
from the coast and increase to 15-20 knots with gust ~25 knots
Wednesday night into Thursday morning. Waves build to 2-3 ft
while seas increase to 3-5 ft offshore late Wednesday and
especially into Thursday with strong offshore flow. SCA
headlines are probable for the waters tomorrow night into
Conditions improve on Thursday as high pressure builds in from the
southwest. Another strong cold front approaches the region on Friday
with increasing SW flow ahead of the boundary and strong NW winds
and CAA forecast behind the front for the start of the weekend.
Increasing tidal anomalies associated with onshore flow near
the mouth of the bay combined with high astronomical tides will
result in some nuisance tidal flooding across the northern bay
tonight. Coastal Flood Statements are in effect after 10pm
tonight for Bishop`s Head and Cambridge in Dorchester county, MD
as well as for bayside portions of Westmoreland, Northumberland,
and Lancaster counties, VA.
Astronomical tides remain elevated for the next few cycles and
further instances of tidal flooding are probable in the coming
days with multiple areas of low pressure/fronts affecting the
Area Forecast Discussion
National Weather Service Bismarck ND
1017 PM CDT Tue May 5 2020
Issued at 1017 PM CDT Tue May 5 2020
A few isolated showers continue across northwest and north central
North Dakota, ahead of a mid level impulse that can be seen on
water vapor moving down from southeast Saskatchewan. Have
extended the isolated shower mention for a few hours for those
areas, otherwise the forecast remains on track.
UPDATE Issued at 706 PM CDT Tue May 5 2020
There has been a general downward trend in shower and thunderstorm
activity over the past hour so, and expect that this trend will
continue through the evening. Two geographic areas where isolated
thunderstorms will remain possible this evening are southwest and
far north central North Dakota.
.SHORT TERM...(This afternoon through Wednesday)
Issued at 240 PM CDT Tue May 5 2020
A weak upper level shortwave will rotate into western North Dakota
late this afternoon and tonight. This wave will be the focus for
widely scattered afternoon showers and isolated thunderstorms,
mainly across the west and south central. 19z RAP Mesoanalysis
shows a pocket of 500+ J/kg SBCAPE across much of the west and
portions of the south central. Although shear is quite weak,
expect some isolated claps of thunder under the heavier showers
that do develop. In general, the heaviest precipitation amounts
will be likely across the southwest and portions of the south
central, maybe a tenth of an inch or two. Coverage of showers will
diminish as the sun sets. Temperatures will dip into the 30s
overnight, possibly into the low 30s across the west.
An upper ridge builds from the west as it deamplifies and we get a
slight warmup with highs in the 60s and mainly dry weather.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 240 PM CDT Tue May 5 2020
The upper ridge breaks down on Thursday as a compact upper low
swings down into South Dakota from southern Montana. Most of the
lift will remain west and south of the state border but the far
southwest may see couple tenths of an inch of rain.
On Saturday, an Alberta Clipper will sweep down from southern
Canada, which will bring much cooler temperatures and even a
chance of some light snow showers. Lows will fall into the lower
30s for much of the weekend with highs generally in the 50s and
Various other waves will continue to slide down the ridge in a
northwest flow regime. This active period will provide various
chances for isolated to scattered showers but much uncertainty
remains with regards to timing across the range of solutions shown
by the global models.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 706 PM CDT Tue May 5 2020
Scattered showers are expected to diminish this evening. Other
than a possible brief period of MVFR ceilings at KJMS this
evening, VFR conditions should prevail through the forecast
period. Northerly winds will become light and variable overnight,
and remain around 10 kts or less through Wednesday.
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
726 PM CDT Tue May 5 2020
Issued at 721 PM CDT Tue May 5 2020
Last couple runs of the HRRR have been a bit colder, so overnight
temperatures were nudged down 1-2 degrees using the 10th
percentile of available model guidance. With dewpoints forecast
to recover back into the mid 30s, there is not much concern that
it will fall any lower than this forecast.
Patchy frost was also added to northwestern portions of the area.
But with some remaining cloud cover and steady north winds, there
should not be enough frost to warrant an advisory.
.SHORT TERM...(This evening through Wednesday)
Issued at 334 PM CDT Tue May 5 2020
A mid-level vorticity max will swing through this evening and early
overnight to give us some low chances of precip, especially in our
northwest half of the CWA. Hi-res ensembles indicate that our
chances would top out at 30 to 40 POPs as our ambient environment is
rather dry, and a bit of a v-shape to soundings through early
evening. Wind gusts should subside with surface cooling except for
where convection pops up, and dry air will help induce potentially
very gusty winds.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 334 PM CDT Tue May 5 2020
Pattern is setting up to be a persistent ridge in the western United
States with general troughing in roughly the the eastern half to two
thirds of the country. Generally speaking, instability will remain
low in the long term, with a bit more elevated instability showing
up for Thursday into Friday. The most significant wave is still
forecast to come through Wednesday night into Thursday/Thursday
evening. For frost, wind speeds look a bit more elevated for
Saturday morning, and temps have been nudged up, so perhaps less
likely now. Still a ways off, so we will have to see.
Long term ensembles and operational runs keep us below normal
temperatures well into mid-May. We will not be getting the brunt of
cold air overall as this is focused farther east, but we will likely
fall short of normal highs near 70 or lower 70s for awhile. Periodic
perturbations and troughs will probably give us chances of rain here
and there, but this pattern is not generally conducive to heavy rain
or widespread severe events. Although temps may get into the mid to
upper 30s for parts of the CWA 2 to 3 times during the long term,
our best chance of frost may be Saturday morning when wind subsides
more and rain chances are decreased.
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Thursday)
Issued at 622 PM CDT Tue May 5 2020
We still could see a few showers across central Nebraska this
evening, but the threat for thunderstorms has decreased and no
longer warrants inclusion in the TAFs.
After this moves out of the area, skies will clear out tonight. We
will have to watch for some low-midlevel clouds moving in from
northeast Nebraska, but this should largely stay northeast of
Winds will also decrease tonight, and will be noticably lighter
tomorrow with gusts only 15-20kts.
Area Forecast Discussion
National Weather Service North Platte NE
746 PM CDT Tue May 5 2020
.SHORT TERM...(This evening through Wednesday night)
Issued at 353 PM CDT Tue May 5 2020
The primary forecast challenges through the weekend are temperatures
and precipitation. Strong northwest flow aloft will keep conditions
rather cool and wet the next several days.
This evening and tonight... Expanded PoP a little farther west to
account for scattered showers and storms in the wake of a cold front
and along a stout shortwave. Convective initiation is underway in
SoDak as of 20z with the activity moving toward far north central
Neb. Elsewhere, towering cu fields are evident over much of the
forecast area and radar echoes are starting to light up in NW Neb
(although it`s likely virga attm). RAP mesoanalysis indicates some
instability, in the form of 500 j/kg MUCAPE and mid level lapse
rates near 8C/km. Expect increased convection over the Sandhills
through the evening. Coverage should remain scattered as the low
levels are quite dry (dew point depressions 30+ F), and begin to
taper after sunset. Surface high pressure settles into the Sandhills
overnight, resulting in nearly calm winds and mostly clear skies.
This will be another favorable setup for a cool night. Blended in
some cooler guidance for lows ranging from around 30F in the
panhandle to upper 30s north central. Included frost mention for
areas west of Hwy 83.
Wednesday and Wed night... Winds slowly transition to southerly and
skies remain mostly clear through the day as the surface high slides
southeast into the Missouri Valley. Negligible temperature advection
occurs at H85 with a weak ridge axis bisecting the forecast area.
Highs will generally be in the lower/mid 60s, similar to today.
Later in the evening, upslope flow intensifies and weak moisture
advection resumes. The next surface low and front emerge from the
Rockies, helping to reinforce lift. A band (or two) of precip should
develop ahead of the front where isentropic upglide really picks up.
The 305K sfc is slated to span almost 200mb across the forecast area
alone with 50kt winds converging to 20kt flow farther east. Despite
the decent signal for precip, thunder parameters are pretty weak.
Included likely PoP across the north and high end chc elsewhere.
.LONG TERM...(Thursday through Tuesday)
Issued at 353 PM CDT Tue May 5 2020
Thursday and beyond... The cool and wet pattern continues into next
week, especially with a tandem of closed upper lows rounding the
Eastern U.S. trough. The combination of strong forcing in the mid
and upper levels as well as several surface front passages present
multiple precip chances, notably Thursday, Saturday, and early
Monday. May see some thunderstorms with the round on Saturday,
mainly across north central Neb, where instability is greater. High
temps are held to the 60s through the weekend, and may not leave the
50s on Monday. Nighttime lows will persistently be in the 30s, so
will need to monitor the potential for frost. Conditions may be ripe
for widespread freeze Sunday morning.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 744 PM CDT Tue May 5 2020
VFR conditions will prevail over the next 24 hours. Winds will
diminish this evening out of northwest. Tomorrow afternoon winds
will shift to the southeast across much of the forecast area and
remain light around 5 to 10 kts.
Updated for 00Z Aviation Forecast Discussion below.
PREV DISCUSSION... /issued 350 PM CDT Tue May 5 2020/
Drier air will settle over the Mid-South tonight in the wake of
the cold front that moved through the area earlier today. There
are still some light radar echoes along/south of the I-40
corridor, but much of this is not reaching the ground. Other than
a few sprinkles this afternoon, we`re not anticipating much in the
way of precip over the next 48 hours.
Expect generally benign and cooler weather conditions across the
region Wednesday. A weak wave moving across the Upper OH Valley
will drive a reinforcing cold front into the area tomorrow. This
will result in cloud cover across west TN into the Bootheel, but
the relatively dry low-levels will preclude rain chances. Should a
shower develop, we`re looking at very limited coverage. This wave
will pass by midday with clearing skies in the afternoon and
evening. Temperatures will top out in the 60s across most of the
Most of Thursday will be nice with highs approaching 70F. We do
anticipate an increase in cloud cover throughout the day and this
may lead to a few very light showers west of the MS River in the
afternoon. Otherwise, dry weather is expected during the daytime
hours. Rain chances will increase Thursday night as a compact
shortwave trough traverses the Ozarks. Strong forcing for ascent
will overspread the region working in conjunction with warm-sector
warm advection to produce scattered showers and a few
thunderstorms. Instability doesn`t look too impressive (and is
mainly elevated at that), limiting the severe weather potential.
We`ll continue to monitor how this system evolves over the next
Cooler and drier air will return over the weekend. Temperatures
Saturday will be on the cool side for May standards with highs in
the low/mid 60s. The well below normal temperatures will persist
Saturday night as temperatures cool into the low/mid 40s. A few
areas in the TN Valley could briefly dip into the upper 30s early
Sunday morning. The good news is that we don`t anticipate any
rainfall across the Mid-South Saturday through Monday.
The flow aloft becomes a bit more zonal by Tuesday with southern
stream shortwave energy approaching from the west. This will
result in a return of low rain chances to the region through
Following VFR conditions overnight, NW winds will become gusty
following a reinforcing cold frontal passage. HRRR hints at some
briefly stronger gusts over 30KT, mainly west of MEM over the
eastern AR delta. These higher gusts should be brief.
VFR stratocumulus deck should clear as winds become light in time
for the Wednesday evening MEM inbounds.
Area Forecast Discussion...Updated
National Weather Service Portland OR
820 PM PDT Tue May 5 2020
Updated aviation discussion
.SYNOPSIS....Showers and slight chance of thunderstorms possible
this evening. A frontal system will push across the area tonight
into Wednesday morning. A switch to drier and much warmer weather
begins late Wednesday as high pressure builds over the region and
will persist through the weekend.
.SHORT TERM...Tonight through Saturday...Current GOES satellite
imagery and radar reflectivity indicate isolated to scattered shower
activity occurring along the northern Coast Range and Cascades.
Slight chance of thunderstorms will also be possible with a few of
these showers as instability continues to increase late this
afternoon to early evening. The highest potential of thunderstorms
will be mainly confined to the higher elevations east of PDX along
the north OR/south WA Cascades. Brief periods of heavy rain and
small hail are possible within a few of these convective showers.
Showers should taper off a little bit around sunset. Elsewhere expect
mainly sunny and dry conditions through the Willamette valley this
evening with temperatures reaching the low to mid 70s while the
coastal areas remain around 60.
Satellite imagery Tuesday afternoon also shows an approaching
elongated front associated with a low southwest of Haida Gwaii.
Strong southwesterly jet aloft will help push upper level trough
across western OR and WA rather quickly late tonight through
Wednesday morning. Gusty southerly winds are likely ahead of the
front as high pressure continues to build along the southern OR
coast this evening. Frontal system will push across the coast
between 6Z to 9Z with a westerly wind shift behind. Upper level
support will likely enhance precipitation rates along the coast with
rainfall totals of up to a quarter of an inch. RAP analysis does
indicate some weak instability along the front which could produce a
few isolated lightning strikes along the coast around midnight.
Expect the front to push through the area by early Wednesday morning.
Rain accumulations along the Cascade range up to 0.20 inches and
around 0.10 inches with the Willamette Valley. The remainder of
Wednesday will see slightly cooler temperatures with showers
dissipating as an upper level ridge builds across the NE Pacific and
surface high pressure moves north just off shore towards Vancouver
The upper ridge shifts over the entire Pacific Northwest region
Thursday and will be the dominate synoptic feature through most of
the weekend. A thermally induced trough will develop from northern
CA into southern WA turning winds offshore and maintaining dry
conditions. Temperatures will begin a warming trend Thursday through
the weekend, with the valley temperatures expected to reach into the
mid 80s possibly by Saturday. Temperatures along the coast will
likely warm into the low to mid 70s as well. /DDH
.LONG TERM...Saturday night through Wednesday...Upper level ridging
will continue Saturday night into Sunday allowing the thermally
induced trough to persist. This dry, warm and offshore flow regime
will persist through Sunday with temperatures only a few degrees
cooler than Saturday. Ensembles and deterministic model guidance
shows the ridge shifting eastward as an upper level low moves into
the NE Pacific west of OR late Sunday. This will allow a strong
surface low to move into the area by Monday. This low will turn
winds back onshore along with precipitation chances increasing early
next week. /DDH
.AVIATION...A few showers continue to move north over the Cascades
this evening, but should decrease a little shortly after sunset.
Otherwise, conditions across the interior remain VFR through tonight
with increasing mid and high clouds. The coast will see MVFR cigs
solidify over the next several hours as onshore flow increases. An
incoming quick moving front will bring the return of light rain to
the coast by midnight tonight, with rain spreading inland overnight.
As rain moves across the forecast area expect a few hours of local
MVFR cigs along with some gusty southerly winds to 20 kt. Conditions
will become showery behind the front, with a mix of MVFR and VFR
showers through the morning hours. Expect shower activity to slowly
decrease during the afternoon as high pressure starts to build into
the Pac NW.
PDX AND APPROACHES...Conditions remain VFR through tonight with
increasing mid clouds. A quick moving cold front will bring a few
hours of light rain along with some MVFR cigs between 09Z and 12Z.
Mainly VFR showers continue through the morning hours, then slowly
decrease during the afternoon. A few hours of gusty southerly winds
to 20 kt possible as the front moves across the terminal late
tonight/early tomorrow morning. /64
.MARINE...Seas are slowly subsiding from their earlier peak and
will let the SCA expire at 3 PM as planned. A fast moving cold
front will cross the waters later this evening. There will be a
very brief period where winds will gust 20-25 kt as the front
moves from West to East, but given the very short duration of 1
hour or less, do not feel a SCA is warranted. Will highlight the
brief increase in the CWF, however. Seas are expected to remain
around 9 ft, but again could very briefly bump back up to 10 ft
as the front crosses.
Thereafter, high pressure builds along the west coast with a
surface thermal low building north from California. Expect
northerly to northeasterly flow over the waters to develop
Wednesday afternoon, possibly reaching SCA gusts 20-25 kt
Wednesday evening, but more likely on Thursday. Will then see
little change heading in to the weekend when the ridge starts
getting nudged eastward beginning Saturday. Sunday looks to bring
a southerly wind reversal. Westerly swell will continue to
subside through the remainder of the week as northerly wind waves
begin to dominate. Expect COmbined seas to largely be 5-7 feet.
PZ...Small Craft Advisory until 3 PM PDT this afternoon for coastal
waters from Cape Shoalwater WA to Florence OR out 60 NM.
Small Craft Advisory until 7 PM PDT this evening for Columbia
Small Craft Advisory from 3 AM to 8 AM PDT Wednesday for
Columbia River Bar.
Interact with us via social media:
This discussion is for Northwest oregon and Southwest Washington
from the Cascade crest to 60 nm offshore. This area is commonly
referred to as the forecast area.
AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
1000 PM EDT Tue May 5 2020
A cold front will push east through the area early Wednesday morning
followed by a secondary cold frontal passage will Wednesday
afternoon. Chilly high pressure will build into the area late week.
.NEAR TERM /THROUGH TONIGHT/...
As of 955 PM Tuesday...
We have cancelled severe thunderstorm watch 168 given a lack of
substantial destablization north into the Piedmont and coastal
Deep convection has been confined mainly to the warm front just
south of the NC/SC border, tracking west to east and likely
hindering better southerly return flow north into the wedge airmass
analyzed in the central Piedmont, where models had indicated
potential for elevated convection owing to steep mid-level lapse
rates on the north periphery of a EML over the SE US. The storms
continue to move off to the ESE and pose no additional threat to the
southern Piedmont/coastal plain.
Meanwhile, scattered convection has been moving through the Blue
Ridge from the instability axis west of the mountains and just ahead
of the cold front analyzed over eastern TN. These elevated storms
have actually held together as they track through the northern
Piedmont, with an uptick in lightning strikes since 9pm, but should
remain sub-severe given that they are out of ahead of better large
scale forcing and not likely to be organized enough to produce large
hail. Latest HRRR suggests they will track off to the ENE out of
the CWA by 05Z.
A few scatted showers may linger through 09Z before the front pushes
through the area. Lows 51-61 NW to SE.
.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
As of 230 PM Tuesday...
The surface low will lift northeast away from NC toward New England
while the trailing cold front surges eastward off the coast. Cool,
dry air will advect into the area in the wake of the front, though
the better push of cold air will occur Wednesday night. An upper
level shortwave will swing through the region Wednesday afternoon,
which could provide enough forcing for showers to develop. The big
question is if showers develop, where will they and what will the
coverage be. High-res models suggest scattered showers across
central NC between noon and sunset, thus will introduce a slight
chance for showers during the aft/eve. Highs will likely top out in
the mid 60s NW to mid 70s SE. Lows will bottom out in the low to mid
40s, though a few of the usual cooler spots could dip into the upper
.LONG TERM /THURSDAY THROUGH TUESDAY/...
As of 300 PM Tuesday...
Thursday and Thursday night will largely be dry in the wake of the
departing upper wave and the next one approaching. Surface high
pressure will build east through the Deep South and off the
Southeast US coast by Friday morning. Highs will likely top out in
the mid to upper 60s with lows again bottoming out in the 40s.
Friday and Friday night: A deepening upper low will slip southeast
through Canada into the Great Lakes Thursday and Friday before
progressing east through the Great Lakes and into the Northeast
Friday night through Saturday. A shortwave disturbance swinging
around the base of the trough the Plains and MS Valley will move
through the mid-Atlantic late Friday into Saturday. At the surface,
a low will develop off the southern Rockies Thursday night and move
through the Midwest and into the TN Valley by Friday afternoon.
Latest model solutions indicate the low strengthening as it lifts
northeast along the Appalachians toward the Northeast US Friday
eve/night. There is still a descent chance for some showers and
storms Friday aft/eve, however there is still some uncertainty
regarding the coverage and strength. Largely expect any showers to
move out of the area overnight as cold, Canadian high pressure
builds into the area. Temperatures are also still somewhat
uncertain, with highs ranging from mid 60s to mid 70s and lows
generally in the 40s.
Saturday through Tuesday: Cool high pressure will build eastward
into, over and through the mid-Atlantic over the weekend while
generally westerly flow persists aloft. Expect cool, dry weather
Saturday and Sunday, with below normal temperatures. A shortwave
aloft will swing through the Great Lakes, OH Valley and Northeast US
early next week, but for now do not expect any significant weather
impacts across central NC as a result. Dry weather should dominate
through Tuesday and while some moderation is expected, temperatures
should remain below normal for the duration.
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 745 PM Tuesday...
MVFR ceilings linger around GSO/INT, while strong storms are
tracking west to east along the NC/SC border. Expect the bulk of
the storms to remain near the SC border, likely impacting FAY by
03Z, with decreasing chances of storms near GSO/INT/RDU/ since the
previous TAF issuance. An isolated shower is still possible at
those sites, and some forecast guidance suggests storms may congeal
and track far enough north to impact RWI by 04Z...though confidence
in this is low. Most MVFR ceilings are expected in showers and
storms, with a period of IFR indicated between 06-10Z at all sites
before a cold front sweeps across the area.
VFR conditions are expected on Wednesday with NW winds that will
gust to 20-25kt during the afternoon
Outlook: VFR conditions will continue through Friday. A cold front
moving east through the area will bring the next chance of rain and
sub-VFR flight restrictions late Friday and Friday night. VFR
conditions will return by early Saturday
Area Forecast Discussion
National Weather Service Blacksburg VA
958 PM EDT Tue May 5 2020
A warm front across northeastern Tennessee and draped down
through South Carolina will shift slightly northward bringing
some unstable air into far southwest Virginia tonight. A low
pressure center will move east across northern Virginia by
Wednesday morning and drag a cold front through the Appalachian
region by the morning and then off the coast by Wednesday
evening. High pressure then builds in Thursday, before another
front arrives Friday.
.NEAR TERM /THROUGH WEDNESDAY/...
As of 957 PM EDT Tuesday...
Made some additional adjustments to temperatures tonight
capturing the cooler air sinking southward. Modified pops for
tonight into Wednesday morning, slowed the exit of the
convection late tonight into Wednesday morning. Extended the
duration of the thunderstorms across the south a few hours.
The threat for stronger convection will remain to our south
tonight. Low temperatures tonight will vary from the lower 30s
in the northwest mountains to around 50 degrees.
As of 758 PM EDT Tuesday...
Made some minor adjustments in temperatures and dew points for
this evening into Wednesday morning utilizing the latest surface
obs, their trends and blended in the NBM. In general, held up
this evening temperatures in the west before allowing the drop
overnight into Wednesday morning. Scattered showers and
thunderstorms are forming in the unstable air to our west
and translating into western portions of the forecast area.
SPC Mesoscale analysis showed surface based cape of 500 to 1000
j/kg pushing into far southwest virginia and eastern Tennessee.
Latest region radar images showed scattered showers and
isolated thunderstorms from southern West Virginia southward to
Western North Carolina. Decided to expand the isolated
thunderstorms into western areas of the forecast area tonight,
basically around I77 corridor. Shaped pops and weather towards
a blend of the HRRR and nam for this evening into tonight. more
As of 225 PM EDT Tuesday...
Mid afternoon radar and observations show area of rain has
moved east of the RNK county warning area with some scattered
showers reforming in the mountains, but any thunder with these
will be from elevated instability as surface wedge remains
firmly in place and temperatures in the lower 50s and even some
upper 40s. However, warm frontal boundary in NE Tennessee is
still expected to move north late this afternoon into the
evening and may still sneak into our far SW Virginia counties
as well as NW NC, to allow some surface-based instability and a
few more storms to develop. With plenty of wind shear to work
with and storms forming near the boundary, still cannot rule out
a severe threat, with an isolated tornado possible. Thinking
now that if these do get into our area it will be limited to
southwest of a line from Bluefield to Wytheville down to
Wilkesboro, but may even more limited to areas like Richlands to
Marion to Boone. Any severe threat will likely be also be
limited in time to very late afternoon and into early evening. A
few thunderstorms will likely shift up into the more stable air
before weakening but would not pose any severe weather threat.
Farther east, the warm front will remain well south of the RNK
county warning area but a few storms could sneak up to near the
Virginia border this evening before moving east by midnight.
Any scattered stronger storms with high rainfall rates could
pose a localized flash flood threat if they move over the same
areas that picked up 0.50-1.00 inches of rain earlier
today, mainly southwest of a line from Bluefield to Hillsville.
Threat not widespread or significant enough for flash flood
Otherwise for tonight, showers and lingering storms move east
after midnight with some remaining upslope showers in the far
west late tonight behind surface cold front as winds shift to
the west and northwest.
Wednesday behind the front and upper trough with cool air aloft,
some isolated showers may once again form during the afternoon,
with latest hi res guidance suggestion that associated weak
upper wave may favor an area of showers across the southern
third of the forecast area, with only very limited thunder
threat given very marginal mid-level instability. Although at
least a slight chance of a few showers really anywhere by
afternoon, and still some lingering lighter showers with the
upslope flow on far western slopes. Did not include any mention
of thunder for any shallow convection on Wednesday. Another
cool day with wide temperature ranges of lower to mid 40s far
west and lower to mid 60s far east with more sun, but not sure
how long sun will last as cumulus field may fill back in quickly
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 100 PM EDT Tuesday...
A broad upper level trough will cross over the Mid Atlantic during
Wednesday night. Lingering upslope moisture should eventually come
to an end overnight as drier air arrives. Colder air should allow
temperatures to come close to the freezing mark by Thursday morning,
but mixing from the northwest breeze will likely inhibit any frost
development. High pressure will bring lighter winds and dry weather
on Thursday before departing offshore by Thursday night. Meanwhile,
a low pressure system will form over the Plains and push a cold
front toward the Ohio River Valley.
By Friday morning, the cold front should reach the Appalachian
Mountains. Rain chances have been increased for Friday due to the
higher confidence portrayed in the model solutions regarding the
widespread coverage of moisture. This cold front should exit on
Friday night, but winds will pick up from the northwest as cold air
advection increases. Lingering upslope rain showers could change to
snow showers or flurries overnight across the higher elevations from
Boone to Lewisburg. However, any snowfall accumulations appear to be
light. Freeze headlines are also becoming increasingly likely for
Friday night along and west of the Blue Ridge.
.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 100 PM EDT Tuesday...
After a cold start to Saturday, temperatures will continue to run
well below normal for early May due to persistent troughing across
the eastern United States. Winds may become more gusty during the
day as boundary layer mixing taps into the higher momentum air
aloft, so speeds have been adjusted upward to indicate an increase
in confidence for the potential of 30-40 MPH gusts along the Blue
Ridge. High pressure should settle over the Mid Atlantic by Saturday
night and bring dry weather through Sunday.
A weak low pressure system will emerge from the Great Lakes on
Sunday night, and it should bring the next chance of rain mainly
west of the Blue Ridge by early Monday morning. Lingering showers
could persist into Monday afternoon before another area of high
pressure clears out the moisture by Monday night. Tuesday appears
generally dry according to the GFS with high pressure under control
as the flow aloft becomes more zonal, but the ECMWF shows another
frontal boundary arriving from the west that could introduce a
slight chance of rain west of the Blue Ridge by Tuesday afternoon.
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
As of 736 PM EDT Tuesday...
SCT to BKN MVFR clouds will transition to MVFR/IFR ceilings
tonight in areas of convection, low clouds and fog. A few
thunderstorms are possible for the next couple of hours from far
Southwest Virginia, across the Northwest North Carolina mountains,
and into the Piedmont of North Carolina. Development of storms
to the west of KBLF, may move across the KBLF taf site. Kept the
mention of thunder at KDAN as scattered storms are forming in
Northwest North carolina this evening.
East to southeast winds will relax this evening and then shift
to West to Northwest and pickup Wednesday morning and gust from
15-20 kts on Wednesday as MVFR and IFR conditions do not lift
until later Wednesday morning. May remain MVFR at KBLF and KLWB
much of the day due to the Northwest upslope flow and some
continuing scattered showers, but may lift and break out at KBCB
and portions of the New River Valley eventually.
Medium confidence on ceilings,visibilities and winds during the
Extended Aviation Discussion...
High pressure arrives by Wed night-Thu to allow VFR to return to
even the western TAF sites, before a front moves in with more
shower chances Friday though mostly expecting VFR with some MVFR
in the mountains. Drier weather is expected Saturday with gusty
NW winds. Scattered MVFR showers may be possible in the
northwest mountains on Sunday.