Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 162333
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
733 PM EDT Mon Jul 16 2018

.SYNOPSIS...
An upper level disturbance will track across the region this evening
into tonight. A cold front will pass through the area Tuesday.
High pressure will build in for Wednesday.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 720 PM EDT Monday...

Not much coverage overall, but several small areas of
showers/thunderstorms, especially along the southern Blue Ridge
and into NE TN close to upper shortwave. Should see more of a
scattering of shower/storms this evening in the west and
isolated in the east if any. Things will subside in the east by
midnight, then more showers/storms are expected ahead of an MCV
by dawn Tuesday in the WV mountains.

Previous discussion...

An upper level disturbance, shortwave aloft will travel east across
the region this afternoon into tonight. Cooling aloft associated
with this feature will create steepening mid level lapse rates this
afternoon. After a lull in convection this morning due to cloud
cover, coverage in showers and thunderstorms will increase this
afternoon into this evening. The primary focus of storms will be
along and west of the Blue Ridge with the best low level convergence
from southerly winds as supported by NAM,GFS and ECMWF.  The Namnest,
SPC HRRR3 and HRRR were hinting at slightly better coverage across
the north. With slow moving deeper convection, there is the
potential for localized heavy rainfall. With high PWATs between 1.50
to 2.00 inches and slow moving storms, rain rates may exceeding 3
inches in an hour. Antecedent conditions are dry with stream levels
at or below normal, however, high rates can/will quickly compromise
storm drains and poor drainage areas. WPC Day 1 excessive rainfall
highlights the flood potential with the marginal threat area. An
isolated strong to severe pulse thunderstorm may also be
possible this afternoon. However, with little shear and
organization present, most storms will remained well below
severe criteria.

Overall areal coverage of showers and thunderstorms is expected to
decrease tonight with loss of solar heating, but threat will not
entirely go away due to the soupy airmass, lingering outflow
boundaries, and an approaching cold front from the Ohio Valley, all
of which will provide as a lifting mechanism for nocturnal showers
in the west. Areas of low clouds and fog will develop overnight into
Tuesday morning. It is going to be another mild night with low
temperatures ranging from the mid 60s in the mountains to the lower
70s in the piedmont.

A cold front should reach the western mountains Tuesday morning and
rotate east Tuesday afternoon across area. Convergence from frontal
boundary and a weakly defined lee trough just east of the Blue Ridge
should foster scattered to numerous showers and thunderstorms. The
potential for locally heavy rains will continue Tuesday with high
PWATs. The severe threat will be limited mainly by the instability
and timing of the boundary. The Day 2 convective outlook placed the
greater severe threat to our northeast with marginal to slight
from mason- dixon line north into New England. High temperatures
Tuesday will vary from the mid 70s in the west to around 90
degrees in the east.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 210 PM EDT Monday...

A cold front will clear the mountains and foothill counties by the
evening then Southside VA around midnight. Most of the forecast area
will stay rain-free through the rest of the period as dry high
pressure wedges south into the Carolinas. The only exception will be
across the Mountain Empire to the Bluefield WV where the wedge will
erode and an inverted surface trough stretches north from the
Tennessee Valley to the southern Ohio Valley Thursday. Coverage of
convective will be scattered. Shower will fade during the evening.

Models are not quite as dry with the wedge in the lower level as
previous run have been. The theta-E boundary stalls along the 460
corridor Wednesday, then drops to the VA/NC border Wednesday night.
With more moisture in the lower level, we can expect thick stratus
clouds along and east of the Blue Ridge to hang around through the
morning, possibly into the afternoon. Temperatures Wednesday morning
will range in the 60s with the higher values being south of 460. If
clouds burn-off by the early afternoon, temperatures will range from
the upper 70s to lower 80s across the mountains to mid 80s east.
With the theta-E boundary moving south Wednesday night, slightly
cooler temperatures are possible with mid to upper 50s across the
mountains and lower 60s east. The theta-E boundary retreats north on
Thursday but the area will maintain a cool easterly flow. This setup
along with thick low clouds will have uniform temperatures across
the area Thursday, ranging from the upper 70s to lower 80s west of
the Blue Ridge to the mid 80s east.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 230 PM EDT Monday...

The wedge will hang around again on Friday, but will erode from the
west and southeast. An upper level trough is expected to become a
close low over the Great Lakes on Friday. This low will send short
waves into the Ohio Valley and erode the wedge from the west. Across
the Southeastern states, a tropical disturbance is expected to track
along the wedge boundary, then off the North Carolina coast Friday
night. As this disturbance advances north, it will erode the wedge
from the southeast. By the end of the day Friday, the wedge may be
nestled along the VA foothills and linger into the night. Areas
outside of the wedge Friday could see scattered showers in the
afternoon and evening hours.

On Saturday, the closed low expands into the Deep South and covers
most of the US from the Mississippi Valley eastward. In the
afternoon, there is a negative tilt to the trough in the eastern US
that could bring active weather to the region. A weak cold front
will then slide across the region Saturday night. Sunday and moreso
Monday, could be active days with heating occuring under the cold
pool.

The area will remain under a trough through most of next week as a
strong blocking ridge drifts westward in the Western Atlantic.
Afternoon and evening showers and thunderstorms are likely each day
from this weekend into the following week. Temperatures will run at
or cooler than normal through the period.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 723 PM EDT Monday...

Expect showers, maybe thunderstorm in vicinity of most sites
this evening for another hour before activity weakens or
diminishes. Should be mainly VFR with at times MVFR/IFR cigs.

Fog again possible overnight in the mountains, but cloud cover
ahead of front will act to keep it limited. Still going LIFR at
LWB for a small window in the 10-12z time frame. Confidence is
medium on this happening.

A cold front will reach the mountains Tuesday morning and move
east across the region Tuesday afternoon. There is a continued
threat of MVFR/IFR with storms associated with the cold front.

Medium confidence in ceilings, visibilities and winds during the
taf period.


Extended Aviation...

The cold front will continue to move east into Tuesday night with
post frontal drying Wednesday. Return flow will bring moisture
back into the area Thursday and Friday. Scattered showers and
thunderstorms with sub-VFR conditions are expected Saturday and
Sunday.

&&

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

&&

$$
SYNOPSIS...KK/PM
NEAR TERM...KK/WP
SHORT TERM...RCS
LONG TERM...RCS
AVIATION...KK/PM/WP



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