Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Highlight Changed Discussion --
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FXUS61 KRNK 251747
Area Forecast Discussion
National Weather Service Blacksburg VA
147 PM EDT Tue Apr 25 2017
Low pressure centered over the eastern Carolinas will slowly
drift northeast and off the coast by tonight. Today will be the
last wet and unsettled weather day before warming and drying
begins Wednesday. High pressure will build across the
southeastern U.S. for the second half of the week. This will
result in a considerable boost to the temperature with above
seasonal warmth expected by the weekend.
.NEAR TERM /THROUGH TONIGHT/...
As of 1021 AM EDT Tuesday...
The flood watch was allowed to expire this morning because the
widespread heavy rainfall has ended or shifted east of area. A
few rounds of moderate rain may still pass across the Southside
of Virginia and the Piedmont of North Carolina this morning.
Flood warnings remain in effect until 1215 PM EDT for ROCKINGHAM
and CASWELL counties. River flood warnings continue today,
please refer to latest FLWs and FLSs. The crest of Danville on
Dan River at 26.8 would put the river at major flood. Several
flood advisories are in effect this morning including Roanoke
and Montgomery counties.
Surface low was centered over eastern North Carolina this
morning with the upper low centered along the SC coast. This
almost vertically stacked system will gradually fill and weaken
as it drifts off the coast today into tonight. HRRR, Hiresw-
arw-east and NAM showed rain tapering off this afternoon from
west to east. Made some minor adjustments in pops and weather
for late morning into this afternoon. Modified temperatures with
the latest surface obs and shaped readings towards the Glamp
for late morning into this afternoon. More changes later...
As of 500 AM EDT Tuesday...
Pronounced cut-off area of low pressure and stream of
moisture/rain continues to impact the Mid-Atlantic Region.
The actual surface low (998 mb) was centered over eastern North
Carolina with the upper low centered along the SC coast. This
almost vertically stacked system is expected to gradually fill
and weaken as it drifts off the coast later today. However, it
will likely take another 24 hours to completely rid its
influence. Until then expect another cloudy day with periods of
light rain or drizzle. The moderate to heavy rain threat has
pretty much come to an end, although can`t rule out an
additional quarter to half inch of rainfall south and east of
Will allow the flood watch to expire this morning. River flood
warnings will continue for the next day or two along some of the
main stem rivers with the greatest impact along the Dan River.
Temperatures today will be 5 to 8 degrees warmer than yesterday,
nudging 60 in many areas, but still well under where we could be
for late April.
For tonight, any clearing will set the stage for fog formation.
Unless the stratus persists, anticipate development of fog per
wet ground, diminishing winds and radiational cooling from the
departing mid/upper level cloud cover.
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 500 AM EDT Tuesday...
The lawn mowers will start humming Wednesday. Anybody that
fertilized their lawn prior to this rain event will have a hay
field to maintain. Temperatures Wednesday are expected to be a
full 15 to 20 degrees warmer with the return of the sun and
warming southwest wind flow aloft.
An upper level ridge of high pressure is expected to begin
building over the southeastern CONUS. This will result in
increasing heights and warming thicknesses with 85h temperatures
climbing to near +15 deg C Wednesday. This will support surface
temperatures well into the 70s, and testing 80 degrees across
southside VA and the Piedmont of NC. Temperatures could
potentially be a degree or two warmer, but think a lot of this
initial surge of warmth will go into latent heating and an
attempt to evaporate all of this moisture laying around from the
multiday rain event.
As we transition into the second half of the week, will have to
keep our eyes on a surface trough/front that will play tag with
our area late Thursday. A trough of low pressure moving out of
the Rockies will spawn an area of low pressure that will track
from the central Plains into the upper Mid-West and western
Great Lakes Wednesday into Thursday. The associated surface
front is forecast to move east, crossing the Ohio/TN valleys
Wednesday night, then across the Appalachians on Thursday. The
front is expected to weaken with time as it encounters the
building ridge of High pressure over the southeast CONUS, so any
shower/storm activity associated with the front is expected to
cross our CWA in a sub-severe stance with the primary threat for
wetting showers across our mountain counties, and little or no
impact to areas east of the Blue Ridge.
.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 530 Am EDT Tuesday...
Surface front will exit or wash out across the forecast area
Friday. Lingering clouds may knock the temperature down a degree
or two Friday, but this will likely be temporary as the Upper
Ridge over the southeast CONUS builds stronger for the weekend.
Models suggest 85h temperatures will warm into the +16 to +19
degree C range by Saturday. This will likely yield temperatures
well above normal with highs in the upper 70s to near 80 in the
mountains and mid to upper 80s for the foothills and piedmont.
With low level moisture combined with these warm temperatures,
this will result in just enough instability for the possibility
of isolated to scattered mainly mountain diurnal convection.
Models hinting at potential for some warm frontal showers just
to our west on Saturday so will need to keep a an eye on that as
we get closer. Otherwise, digging trough to the west approaches
and models in general agreement that associated cold front
approaches late on Monday and should be quite a big stronger
than the one late this week. If the front moves through during
max heating Monday afternoon will need to watch potential for
severe weather as well, and this will be a fairly fast moving
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
-- Changed Discussion --As of 147 PM EDT Tuesday...
MVFR ceilings with pockets of IFR with rain,drizzle and fog
will prevail this afternoon into tonight. The upper level low
will slowly drift northeast tonight and away from the area
Wednesday. An increasing pressure gradient around the area of
low pressure will also result in stronger gusty northeast winds
this afternoon into this evening, then winds become light and
variable tonight into Wednesday morning.
Areas of low clouds and fog will develop tonight with IFR
conditions expected into Wednesday morning. Conditions will
become VFR by Wednesday afternoon. Winds will remain light
High confidence in ceilings, visibilities and winds during the
Extended Aviation Discussion...
Better flying weather is expected for the second half of the
week, though another front may bring scattered MVFR
showers/storms Thursday afternoon and evening across the
mountains. Drier and much warmer weather will return for Friday
and Saturday with temperatures much above normal for the
weekend. Can not completely rule out an isolated MVFR
thunderstorms along the southern Blue ridge. Scattered MVFR
showers and thunderstorms are possible Sunday and Monday.
-- End Changed Discussion --
As of 600 AM EDT Tuesday....
Rainfall totals since 8AM Friday through this morning were in
the 2 to 6 inch range, with the main impact from heavy rainfall
roughly south of a line from Bluefield West Virginia to
Lynchburg VA. Runoff from this rainfall had resulted in small
stream flooding with numerous roads and low water crossings
closed due to flooding. Many trees fell due to the saturated
ground and several minor rock and mud slides were reported.
All of this runoff has now flowed into the rivers where there
is ongoing river flood warnings for sections of the Roanoke,
and Dan River Basins. The Flood warning for the NEW river has
been canceled, the crest now moving downstream and out of the