Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Blacksburg Virginia
753 am EDT Monday Mar 17 2014
low pressure was over the southeast United States and a strong
wedge of high pressure extended from New York into South Carolina.
The high pressure wedge will remain in place today while the
southeast low moves off the coast tonight. A large low pressure
system developing in The Rockies today will move east...and will
push a cold front through the area by Thursday morning.
Near term /through tonight/...
as of 300 am EDT Monday...
Very strong...very persistent wedge through tonight. Atmosphere
remains moist below 700 mb. Leading short wave over the lower
Mississippi Valley tracks across the southern Appalachians by this
evening. The closed upper low over Texas follows just behind this
wave and will weaken by the time it reaches the Carolinas on Tuesday
Models are shifting the deformation area that on the northwest side
of the system into the northwest County Warning Area this
morning...but this deeper moisture erodes by afternoon. This area
will have the better chance for accumulating snow through noon.
Models are bring deeper moisture to the south into the southern and
southeast County Warning Area this morning.
06z/2am sounding from rnk showed a warm nose around 760 mb at 2.5
degrees celcius which was warmer than at 00z/8pm. BUFKIT soundings
had depth of wedge remaining about the same through the day with
near surface layers becoming colder. Only minor increase to
temperatures from what they will be at sunrise. Sounding mainly
showing sleet except for far northern County Warning Area.
Middle and high level moisture are gone by late afternoon leaving no
potential for snow crystals in the clouds. Expect light freezing
rain and freezing drizzle to continue in most locations overnight.
Even the locations that were getting snow this morning in the
northern County Warning Area will be changing over to only light
freezing rain and freezing drizzle by the end of the day as moisture
in confined to low levels. Precipitation amounts will be light.
Will hold off of any change to headlines at this time. An extension
or additional Winter Weather Advisory will likely be needed tonight.
Short term /Tuesday through Thursday night/...
as of 345 am EDT Monday...
Wedge will try to last until a subtle cold front arrives Wednesday
night. Another strong disturbance moving off the Carolina coast
Tuesday with surface high strengthening over New England...will
serve to reinforce The Wedge and east to NE flow. This should create a
large change in temperatures as extreme SW Virginia may be in the 50s...with
parts of the Roanoke valley and southern Shenandoah crawling to 40f
on Tuesday. Chilly temperatures in place Tuesday morning may lead to very
light freezing drizzle with low clouds and upslope component along
the crest of the Blue Ridge. The sun should appear from blf to jfz
later Tuesday with some breaks even making it into the New River
valley late day Tuesday. However...abundant low level moisture will allow
the clouds to reform again Tuesday night. Expecting widespread light
rain and drizzle with fog Tuesday night...save some of the parts of
extreme SW Virginia and southeast West Virginia which will reside just outside The
Wedge. Again...especially along the Blue Ridge...temperatures may slip
to freezing after not much rise in temperature Tuesday afternoon with
freezing drizzle into Wednesday morning. Although a front will arrive
Wednesday and perhaps finally erase the easterly
component...experience says that strong wedges like this
one...will keep roa/lyh/cho perhaps much cooler than guidance even
on Wednesday...with low clouds remaining. Sunshine finally returns
across the entire region on Thursday...with downsloping winds and
highs near 60f at the warmest locations.
Long term /Friday through Sunday/...
as of 400 PM EDT Sunday...
Zonal flow will generally dominate much of the long range period. An
upper trough will race through the region Sat with a chance of
-shra. A substantial warmup is expected in advance of this system
with strong SW flow. We should see 60s and perhaps in a few low 70s
across the Piedmont Friday in advance of this system. Depending on the
degree of instability...an isolated thunderstorms and rain cannot be completely ruled
out...but it has not been advertised just yet as the dynamics are
weak and the best instability remains east and south of the County Warning Area.
This system heralds a return to colder northwest flow and a return to
normal or even below normal temperatures for sun into early next
week as a large Canadian high drops southeastward from the Great
Plains and Great Lakes region. Some weak embedded disturbances
appear inevitable...but none have strong enough signals at this
point to include mentionable probability of precipitation or significant upslope -shsn. A
southern stream system at this point is forecast to remain south of
the County Warning Area sun-Mon...but as always will need to be watched closely for
any winter weather potential as it creeps just south of our County Warning Area
Aviation /12z Monday through Friday/...
as of 745 am EDT Monday...
Surface low pressure was over Georgia with a strong wedge of high
pressure extending from New York into South Carolina. The Wedge
will remain over the region through Wednesday. The low will
move offshore tonight. A widespread mix of winter precipitation
will result in very poor flying conditions this morning. Sleet and
freezing drizzle are expected at kbcb/kroa/klyh/kdan and kblf.
Farther north where the cold air is deeper klwb will have snow and
sleet this morning.
Expecting a break in the precipitation this afternoon. However...
ceilings will remain IFR to low MVFR for the rest of the day. As
the deeper moisture erodes above 700 mb...the low level moisture
will remain. Temperatures will rise only a few degrees and most
locations will be below freezing overnight. With areas of
freezing drizzle...a glaze to a tenth of an inch of ice is likely.
Ceilings and visibilities will be IFR to LIFR.
This low cloud will likely remain across the area until deeper
mixing arrives with a cold frontal passage on Wednesday.
Extended aviation discussion...
VFR conditions are expected Wednesday night through Friday.
Virginia...Winter Storm Warning until 2 PM EDT this afternoon for
Winter Weather Advisory until 2 PM EDT this afternoon for
NC...Winter Weather Advisory until 2 PM EDT this afternoon for
WV...Winter Storm Warning until 2 PM EDT this afternoon for
Winter Weather Advisory until 2 PM EDT this afternoon for