Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Blacksburg Virginia
353 am EDT sun Oct 4 2015
cool Canadian high pressure is positioned to our north and is
wedged down the east side of the Appalachians. An upper level low
pressure system will remain centered over the southeast states
with a stationary surface front along the southeast Atlantic
coast. These features will continue to combine to result in cloudy
and damp weather into tonight.
Near term /through Monday night/...
as of 355 am EDT Sunday...
Closed upper level low over the southeast United States will slowly
move towards the east. The transport of deep moisture has shifts
further south into the southern Appalachians. The coastal front near
the southeast coast is serving as a focus for the best moisture
convergence and deepest convection.
Canceled the few remaining counties in a Flash Flood Watch for
today...with the latest radar/satellite loops supporting this
southward shift as the low continues to close off at upper levels.
The result will be a more of a west to east orientation of the most
favorable divergence aloft and associated warm conveyor belt and
moisture axis. While the ffg remain low with saturated soils...do
not believe we will have the rainfall rates need for widespread
With impressive 35 to 45 knot 850mb jet...will hold on to the Wind
Advisory today because of impact with saturated soils across the
region. A strong pressure gradient will persist across the region
between low pressure located to our south and high pressure located
near New England.
An easterly wind will continue to draw Atlantic moisture into the
region with clouds and rain today into tonight. On Monday...the flow
gradually back to nearly a northerly component. The result will be
advecting drier air into the region and shutting off the upslope
component. Anticipate a trend towards decreasing chances of rain
from northwest to southwest during the Sunday night into Monday
night. Monday night into Tuesday...surface high pressure will work
its way into the area from the northwest.
The combination of cloud cover and precipitation will keep this
afternoon high temperatures on the cool side with readings from the
middle 50s in the mountains to middle 60s in the far Southwest Mountains.
Rich cloud cover tonight will hold temperatures up on the mild side
with values from the upper 40s in the northern mountains to the middle
50s in the south. Cloud cover will start to gradually decrease
across the northern portions of the area. High temperatures will
moderate Monday to the lower 60s in the northern mountains to the
upper 60s to lower 70s in the far western mountains. Under partly
cloudy skies Monday night will low temperatures from the lower 409s
in the north to the lower 50s in the Piedmont.
Short term /Tuesday through Tuesday night/...
as of 400 PM EDT Saturday...
Tuesday through Tuesday night surface...high pressure will work
its way into the area from the northwest. No precipitation is
expected...cloud cover will be on the decrease...and temperatures
will be around normal.
Long term /Wednesday through Saturday/...
as of 400 PM EDT Friday...
Building surface high pressure...along with a strengthening ridging
aloft will continue our dry weather Wednesday through Thursday. By
Friday...both the surface high and the ridge aloft shift east of the
area in advance of an approaching cold front. Look for a trend
towards milder weather Wednesday through Friday. The cold front is
prognosticated to move into the region and then wash out over the region.
The result will be little if any change in airmass comparing Friday
to Saturday...with isolated to scattered showers possible...mainly
across the mountains.
Aviation /08z Sunday through Thursday/...
as of 130 am EDT Sunday...
Widespread MVFR/IFR conditions will persist this morning into
tonight with periods of light rain or drizzle. Low pressure
centered over the southeast Continental U.S. And high pressure centered over
eastern Canada will result in a persistent northeast to east wind
across the region through the remainder of the weekend with little
or no change expected until Monday.
Visibilities will be highly variable per periodic bands of rain
and drizzle. Ceilings on the other hand should be relatively stable
ranging from 300 feet to 1900 feet above ground level...ridges partially obscured.
Thus will attempt to maintain lower prevailing conditions in the
tafs with limited tempo groups to avoid chasing abrupt up and down
visibilities in bands of rain.
Winds aloft...3 to 5kft above ground level are rather strong...out of the east
northeast at 30 to 50 kts. This will result in strong surface
gusts...especially near the crest of the Blue Ridge and points
east through Sunday.
Medium confidence in ceilings...visibilities and winds during the
Weak high pressure looks to finally build in early next week with a
return to more in the way of VFR conditions Monday afternoon and
across the region Tuesday into Friday. A frontal boundary will
approach next weekend.
as of 630 PM EDT Saturday...
The primary threat for widespread heavy rain has shifted south of
the hydrologic service area. However...still dealing with the
runoff from the 1 to 2 inches of rain that fell near the
Virginia...North Carolina border since Friday. Also bands of
heavier showers have redeveloped along the Blue Ridge where flash
flood guidance remains quite low. This could lead to added minor
flooding in spots from southern Virginia into northwest North
Carolina but wont include back in a watch again for now.
Flood warnings are in effect for the Dan River with moderate
flooding likely from Danville to South Boston. Minor flooding is
still possible along the lower Roanoke. Significant rises are
also taking place on the Yadkin River and the Watauga river in
North Carolina...both of these rivers expected to rise to near
Rain amounts were considerably less across the remainder of Virginia
and West Virginia...with no flooding forecast. That being
said...there is still residual effects with roads being damaged
in places due to flooding from a few days ago. There are still
quite a few Road closures being reported in addition to reports of
roads being blocked by debris/mud or downed trees which are being
uprooted easier due to the combination of the soggy ground and
modest wind speeds.
Virginia...Wind Advisory until 8 am EDT Monday for vaz011>020-022>024-
NC...Wind Advisory until 8 am EDT Monday for ncz001>006-018>020.