-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRNK 250130
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
930 PM EDT Thu May 24 2018

.SYNOPSIS...
High pressure will remain over the mid-Atlantic states tonight,
then moves offshore Friday. A tropical low in the Gulf of
Mexico will move ashore and wobble over the lower Mississippi
through the holiday weekend. Tropical moisture will stream
northward into the region through the holiday weekend, giving
the area a good chance for scattered afternoon and evening
showers and thunderstorms.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 930 PM EDT Thursday...

Did not see any showers or thunder in the southwest portion of
forecast area as previously forecast. After losing diurnal
heating, not a lot of confidence that anything will develop, but
small possibilities exist for something to advect up from the
south. Short range guidance continues to hint at the
possibility so leaving low PoPs for these areas at this time.

Otherwise, adjusted temps and DPs to match current obs and
trends with no other notable adjustments.


Previous Discussion...

Weak high pressure will remain wedged across the Blue Ridge
east into the piedmont through tonight. A weak inverted trough
sits along the western side of the Appalachains from the
Tennessee Valley north into the coal fields of West Virginia.
This trough with ample heating and in the vicinity of a wedge
boundary, may spark a few showers or storms this afternoon and
evening. There is some downsloping that could limit convection,
but it is weak, therefore kept pops in the low chance/scattered
range from the North Carolina High Country to the Mountain
Empire of southwest Virginia. High pressure will keep the rest
of the area dry with lower dewpoints mainly north of a Bluefield
to Danville line.

Tonight, not much change from previous forecast, models hinting
at the low threat of showers in the NC mountains/foothills,
with a better threat of patchy fog to the northeast as maritime
air continues to move in from the east/southeast. Models keeping
skies fairly clear north of the NC/VA border so will see if any
stratus forms, as NAM forecast soundings suggest this potential
along/east of the Blue Ridge. Lows tonight will be in the 50s
in the mountains, with upper 50s to lower 60s east.

The wedge erodes Friday which will allow warm moist southerly
flow to increase over the region. As inversion break by the
afternoon, scattered showers and thunderstorms are possible
across the mountains in the afternoon. With ridging aloft,
storms` life cycle may be limited to 30-60 minutes. Temperatures
Friday afternoon will warm into the 70s across the mountains to
lower to mid 80s east.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 115 PM EDT Thursday...

A vorticity maximum was trapped under the southeast upper ridge
will drift across the southern Appalachians on Saturday. Not
much forcing with this feature but may still trigger afternoon
and evening thunderstorms along the southern Blue Ridge. 500 MB
heights remain above 582dm and resulting in above normal
temperatures.

GFS lined deeper moisture up across Virginia and Tennessee on
Saturday and from Delaware to southern Kentucky on Sunday. No
well defined surface boundaries or upper support but enough
heating each day for isolated to scattered afternoon and evening
thunderstorms. Surface dewpoint approaching 70 degrees too by
Saturday afternoon so humid during the day with most unstable
Convective Available Potential Energy roughly around 2000 J/KG
and muggy at night. Thunderstorms may have the potential for
heavy rain on Saturday with storm motion from 10 to 20 mph and
precipitable water values of 1.5 to 1.8 inches.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 115 PM EDT Thursday

Models bring moisture and lift into southern Virginia and
northern North Carolina on Monday. Will have a higher
probability of rain for the afternoon and evening. Monday and
Tuesday will have upslope southeast wind and precipitable water
values around 1.5 inches so all that moisture will mean the
potential for heavy rain.

Potential tropical system will remain near the Gulf Coast
Monday through Wednesday between upper ridge over the southwest
then central United States and the off the southeast coast.
Thursday the low opens and fills and moves northeast. Models
have come into better agreement taking this feature into the
Tennessee Valley by Thursday morning. ECMWF has the deeper
moisture over Virginia and North Carolina again Wednesday and
Thursday.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
As of 725 PM EDT Thursday...

VFR conditions exist through most of the forecast area with some
MVFR ceilings noted through the mountain empire of VA and the
Northwest mountains of NC. These lower ceilings should begin to
erode in the next couple of hours after they lose their diurnal
support. As it stands, visible satellite give no indication
that these lower clouds will advect over any of the TAF
locations.

DPs remain rather high and with sufficient clearing tonight will
maintain a low chance for MVFR fog overnight. Will not advertise
fog at ROA and BLF as they do not appear as likely to reach the
crossover temp overnight.

Fog dissipates shortly after sunrise and conditions will be VFR
throughout as high pressure remains the main player for the
duration of the forecast period. Friday afternoon, isolated
showers and thunderstorms will be possible through the
mountains. Due to the isolated nature and the short life
expectancy of these storms have opted not to specifically
include in any TAF for now, but can likely be handled best with
TEMPO groups in future TAF runs.

Confidence high in cigs and winds thru the period, medium on
vsbys.

.Extended Aviation Discussion...

VFR Friday night. Tropical like moisture streams back north as
a warm front moves through Saturday with a return to
showers/storms and potential sub-VFR conditions and heavy rain
thru the holiday weekend.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.

&&

$$
SYNOPSIS...RCS
NEAR TERM...JR/RCS
SHORT TERM...AMS
LONG TERM...AMS
AVIATION...JR/RCS