Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Highlight Changed Discussion --
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FXUS61 KRNK 191759
Area Forecast Discussion
National Weather Service Blacksburg VA
159 PM EDT THU MAY 19 2016
High pressure over the Great Lakes will move slowly south and east
today and tonight. A large low pressure system will develop over
the lower Mississippi Valley on Friday then track into the Mid
Atlantic region on Saturday, then off the east coast by Sunday.
High pressure will cover much of the eastern United States Sunday
night and Monday.
.NEAR TERM /THROUGH TONIGHT/...
As of 1255 pm EDT Thursday...
Drier air continues to nose its way south into the region,
allowing for some dissipation of cloud over in the north along
with a ending drizzle in the same geographical region. The
southern third of the region still is expected to get some patchy
light drizzle and patchy light rain, but this too will be trending
towards less coverage. Temperatures will rise more quickly across
southeast West Virginia than elsewhere given the trend in cloud
cover. Have bumped forecast high temperature because of this.
As of 926 AM EDT Thursday...
Overall forecast looks on track. Light rain/drizzle mainly across
the Blue Ridge and points east and south will stay around through
at least early afternoon. Some sunshine will be creeping toward
Southwest Virginia west of I-77 north toward Western Greenbrier WV
later this afternoon, but most will be socked in for the day with
clouds. Lowered temps across the east, and as far west as the New
River Valley given cool start and lack of sun. This based off the
latest LAV as well.
Previous valid discussion...
Surface low pressure was moving away from the
east coast early this morning. An inverted trof was along the
western slopes of the Appalachians with high pressure in between.
Little change in this weather pattern is expected through tonight.
Subtle short wave tracking out of the Tennessee Valley will
trigger areas of rain today and tonight, mainly in the southern
half of the county warning area. Rainfall amounts today and
tonight will be light.
Models showed varying degrees of drier air advancing south into
the forecast area this afternoon and evening. Have slowed down any
clearing until later today. Based timing and southern extent of
any clearing mainly on the GFS. Best probability for any sun this
afternoon will be north of a Tazewell to Buckingham line. By late
tonight the clouds will be returning north.
Kept maximum temperatures closer to the cooler MAV guidance.
Little change in 850MB temperatures and increasing dew points will
hold minimum temperatures in the mid 40s to mid 50s tonight.
.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
As of 330 AM EDT Thursday...
High pressure to our north Friday morning will slide east into the
Atlantic ocean by Friday night. At the same time, a strong
disturbance will track out of the southern Mississippi Valley to the
Tennessee Valley Friday. Rich moisture and shortwaves tracking over
the wedge will bring rain back into the region starting in the
southwest and spreading east to the Piedmont Friday evening into
Friday night. High temperatures Friday will range from the upper 50s
in the mountains to near 70 degrees in the northeast.
Forecast through the long term has a very low confidence value. The
ECM has this low wobbling along the New England coast, while the GFS
has it off the Carolina coast.
Moderate to heavy rain will travel across the area Friday evening
into Friday night as a shortwave move over the wedge. Precipitable
water climb into the 1-1.5 inch range. the three hour FFG is
relatively high with values from 1.6 to 3.5 inches. If the rain
rates are high enough and training happen then there is a potential
for flooding issue. WPC day three excessive rainfall outlook
highlights the potential.
Rainfall amounts Friday into Saturday will range from 1 to 2 inches,
local higher amounts are possible along the eastern slopes of the
Blue Ridge. Low temperatures Friday night will drop into the upper
40s in the mountains to the mid 50s in the piedmont.
An upper level trough over the Ohio-Tennessee Valleys Saturday
morning will kick the moderate to heavy rain east of the area during
the afternoon. Whether this trough will be enough to completely
remove the wedge is a question yet to be answered. included the
mention of an isolated thunderstorm in the south Saturday afternoon
to match up with some instability shown on the GFS. Clouds and rain
will keep Saturday`s temperatures cooler than normal with highs from
the mid 50s in the north to the mid 60s along the southern Blue Ridge
Allowed for isolated to scattered showers Saturday night. Low
temperatures Saturday night will drop into the mid 40s in the west
to the lower 50s in the east.
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 330 AM EDT Thursday...
A closed low develops over the Mid Atlantic Coast by Sunday night
and drifts northward into midweek. Several shortwaves will rotate
around the upper low, this will generate mainly afternoon and
evening showers with heating under cold pool. An upper ridge will
try to build east for the end of the week.
Temperatures will remain cooler than normal until this low moves out
to sea. As the low pulls away, look for temperatures to moderate
towards the end of the week.
.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
-- Changed Discussion --As of 140 pm EDT Thursday...
Drier air will continue to work its way into the northern portion
of the area, bringing VFR conditions to that area. Flight
categories will slowly improve from north to south through the
remainder of the afternoon...with most locations at VFR by
22Z/6pm. The light rain and light drizzle that is near the NC/VA
border will also slowly erode. The light precipitation will
linger the longest across the northern mountains and foothills of
Overnight, the low level moisture will condense into IFR/MVFR
ceilings with some light fog possible as well in spots under a
developing wedge of high pressure. After about 13Z/9am Friday,
flight categories will again improve to VFR as the nocturnal
inversion breaks. Rain will again start progressing into the area
by the late morning across southwest portions of the forecast
area. At this time, none of the TAF locations are expected to be
impacted by 18Z/2pm.
Rain will overrun the region Friday afternoon into Friday night on
the east side of an approaching upper level trough and surface low.
This rain will help to strengthen the lee side wedge. Anticipate
cloud cover to trend to IFR/MFVR ceilings with MVFR visibilities
for rain and light fog.
Saturday, the precipitation will trend more showery as the axis of
the upper trough draws close and the surface low passes overhead.
Flight conditions will improve as the low level winds become
northwest and the lee side wedge erodes. Isolated afternoon
thunderstorms cannot be ruled out as surface instability increases,
especially in the west.
Sunday, mainly VFR conditions are expected along with some hit or
miss showers as the axis of the upper trough passes across the
region. The best potential for MVFR conditions will be across
southeast West Virginia where northwest upslope cloud cover is
Monday into Tuesday, most areas will experience VFR conditions as
an upper level shortwave ridge noses itself into the area.
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