Area forecast discussion
National Weather Service Blacksburg Virginia
118 PM EDT Wednesday Jun 19 2013
Synopsis...
a weak cold front will drift south into the area today. Weak high
pressure will build into the area from the north later Wednesday
night and Thursday...resulting in somewhat drier weather into the
end of the week.
&&
Near term /through tonight/...
as 0f 110 PM EDT Wednesday...
Kfcx 88d image indicated isolated showers forming mainly along
the Blue Ridge this afternoon. Showers developing near
Christiansburg at 17z. Adjusted probability of precipitation to allow for a slight chance
in the west. Main focus on 12z runs still expected to be in the
northeast and east this afternoon into this evening. Adjusted
temperatures and cloud cover for the latest trends.
As of 915 am EDT Wednesday...
Surface chart displayed cold front from Lex to ekn to dov this
morning.This front will drop south across our region today. This
morning 8am/12z rnk sounding showed precipitable waters down to around 1 inch
with northerly flow. The 06s rnk WRF arw and NAM support current
initialization of the few showers across the Alleghany front east
to the Blue Ridge...then flow turns north sending the showers
south across the Piedmont. There is enough instablity to mention
scattered thunderstorms especially in the foothills and Piedmont.
Any diurnally-driven convection would dissipate early this
evening into tonight.
Low clouds and fog slowly mixing out/lifting this morning.
Modified cloud cover across to latest satelitte trends. Made some
minor adjustments in late morning into early afternoon
temperatures and dew points. Enjoy the pleasant afternoon.
As of 330 am EDT Wednesday...
Pair of fronts currently across the region. First with the deep
convection has moved south of US and was located from northern Georgia to NE
NC early this morning. The secondary front with drier air behind it
was layed out from cvg-crw-nrn Virginia. Some lower dewpoints have seeped
southward into the mountains...with temperatures close to them allowing fog to form
given wet ground and scattering out of clouds. This fog will be
lingering through middle morning before dissipating.
Showers have been scarce and mainly north of the mountains of southeast WV this
morning. The 00z NAM/local WRF along with Storm Prediction Center WRF was followed
through the day given its initialization of the few showers. There
is agreement that those earlier showers will leave enough of a
boundary to refire more by midday across the Alleghany front east to
the Blue Ridge...then flow turns north sending the showers south
across the Virginia foothills and Piedmont with instability increasing
this afternoon allowing for some thunderstorms to form. At the
moment confidence not high enough to go likely probability of precipitation and think will
see more scattered in nature to the convection...but still looks
like areas from Hot Springs and Lexington Virginia south through the
Roanoke valley and into Southside have a better chance today than
areas further west. Have broadbrushed some lower chances in the west
with little to no coverage west of I-77. By late afternoon into
evening the flow turns more east and models turn showers more to the
southwest across the NC counties. Once the sun sets...think showers
and storms weaken but enough convergence along dying front to keep a
few showers around until midnight across the NC counties/Virginia border
counties. Models even hinting of keeping a few showers around the
Blue Ridge into Thursday morning but given the lack of coverage this
morning the threat should be gone after midnight.
Again really moist ground and clearing in places with light/calm wind
should lead to the development of fog.
Temperatures forecasted to be a little cooler than MOS as the flow turns
north. Tricky given cloud cover where there will be some periods of
sunshine and clouds...especially across the eastern County Warning Area this afternoon.
Looking at highs from the middle to upper 70s across the west to lower
80s southeast.
Tonight...will be cooler but wet ground will keep it from dropping
further so looking at lows in the middle to upper 50s west to lower 60s
east.
&&
Short term /Thursday through Friday night/...
as of 240 am EDT Wednesday...
Surface high pressure off the middle Atlantic coast will continue to
extend inland through the period and gradually strengthen in
response to building 500 mb heights by the weekend. This will allow for
a low level easterly fetch around the high...with the flow veering
more southeast along and west of the Blue Ridge espcly Thursday into Thursday night.
Models continue to show a low level convergence zone along the
mountains Thursday...that will gradually shift westward Friday in
response to drier advection out east...and more of a NE wind
component driven by possible low pressure off the Outer Banks. Any
organized or widespread convection likely hindered by continued
drying aloft as well as with increasing subsidence with low level
moisture underneath a weak inversion aloft. Appears best
diurnally driven chances Thursday afternoon...so running with low chance
scattered probability of precipitation western third...then more isolated coverage mainly I-
77 corridor on Friday. Otherwise more clouds west early Thursday with range
from pc west to mainly sunny east Thursday...and again Friday when
should be more sun all sections.
Low level drying should push dewpoints lower...and make for lower
humidity through the period...with a good diurnal spread in temperatures
from the upper 70s-middle 80s for highs...to pleasant 50s/low 60s for
lows most nights.
&&
Long term /Saturday through Tuesday/...
as of 345 PM EDT Tuesday...
Moderating temperatures expected over the weekend and into early
next week as the upper level ridge continues to build...850 temperatures
creeping toward +2oc for Monday and Tuesday. This suggests surface
temperatures will top out mainly in the 80sf...testing 90f degrees for
the urban areas. No real focus for deep convection during the
period except for convergence over the mountains...so kept any precipitation
threat mainly diurnal and primarily targeted to the mountains
&&
Aviation /18z Wednesday through Sunday/...
As of 115 PM EDT Wednesday...
Scattered to broken MVFR clouds expected this afternoon as flow
slowly turns more east to southeast espcly along and east
of the the Blue Ridge. Latest models include rnk wrfarw
and NAM suggest some rain showers/thunderstorms and rain potential mainly kroa/klyh/kdan.
Highlighted this potential with thunderstorms in the vicinity in taf. Taf site with the
best chance for a thunderstorm is lyh. Otherwise leaving out precipitation
mention given isolated nature elsewhere. Leftover clouds and widely
scattered convection may linger into tonight along the Blue Ridge
corridor with most of this coverage likely ending up south of the
terminals before ending later Wednesday night. Fog/stratus expected
tonight into Thursday morning. Confidence high on sub VFR at most
sites. MVFR ceilings with IFR/LIFR visibilities are possible in favored
locations.
For Thursday into the weekend...continued diurnal
convection...especially along the Appalachians...with locally
brief MVFR-IFR ceilings/visibilities in thunderstorms and rain. Areas of MVFR-IFR visibilities
br...locally IFR fog...also possible during the morning hours. Otherwise
overall VFR during the daytime hours before/after any ridge
oriented convection develops.
&&
Rnk watches/warnings/advisories...
Virginia...none.
NC...none.
WV...none.
&&
$$
Synopsis...wp
near term...kk/wp
short term...jh
long term...PM
aviation...jc/jh/kk/wp
