Scientific Forecaster Discussion
fxus61 krnk 140521
Area forecast discussion
National Weather Service Blacksburg Virginia
1221 am EST Thu Nov 14 2019
high pressure settles across the area tonight into Thursday. Low
pressure rides along the southeast coast Thursday night into Friday,
bringing some clouds and our next chance for precipitation, mainly
to the Piedmont areas. Temperatures will moderate during the next
Near term /through today/...
as of 222 PM EST Wednesday...
It is unseasonably cold this afternoon and some record cold
high temperatures may be challenged especially at Danville and
Roanoke. See climate section below for records.
High pressure over the region will move east tonight into Thursday.
A shortwave crossing portions of the plains will dig down across the
lower Mississippi and Tennessee valleys on Thursday.
Under mostly clear skies and light winds good radiational cooling
conditions are expected. Danville may be close to a record low
tonight. Southern stream energy moving across the Gulf Coast states
will advect high clouds northward. Low temperatures tonight will
vary from around 10 in the mountains to around 20 degrees in the
High pressure will push offshore on Thursday, while a low pressure
system moves into the Gulf of Mexico. Clouds will increase across
the mid Atlantic by the afternoon. Moisture streaming northward from
this low center could reach Southside Virginia and the North
Carolina Piedmont Thursday evening. Allowed for some light chance of
rain in the southeast portion of the forecast area. High
temperatures Thursday will range from the upper 30s in the mountains
to the mid 40s in the Piedmont.
Forecast confidence: high during the near term period.
Short term /tonight through Saturday/...
as of 250 PM EST Wednesday...
The northern and southern jet streams will phase Thursday night.
This will create a surface low that will track across northern
Florida to the Carolina coast on Friday. Majority of the convection
will remain south of the area across the southeastern states.
However, warm moist air riding over lingering shallow wedge across
the Piedmont may bring a tenth of an inch of rain to northwestern
North Carolina and Southside Virginia Thursday night into Friday
A cut-off low forms over the southern Mississippi Valley on Friday,
then tracks across the Gulf states Friday night. The upper low
catches up with the surface low off the Carolina coast on Saturday
to become an occluded low. Before these two systems merge, models
are advertising a deformation zone sitting over the southern
Appalachian Mountains to southeastern Virginia. This area includes
the southern portion of Blacksburg County Warning Area from the
North Carolina high country to Southside Virginia. This area may
receive a couple tenths of an inch of rain Friday afternoon into
Saturday morning. Amounts may vary if this zone moves north or south.
Temperatures will remain colder than normal. Highs Friday will range
from the mid 40s to lower 50s. On Saturday, temperatures will be in
the 40s across the entire area.
Long term /Saturday night through Wednesday/...
as of 250 PM EST Wednesday...
An occluded low may wobble off the southeast coast Saturday night
then moves out to sea on Sunday. High pressure wedges in from the
north and should keep the region dry through Monday night. A large
upper level trough will track across the US early next week and may
bring rain to the area Tuesday or Wednesday.
Models differ slightly on a disturbance coming out of the Gulf,
tracking north along the coast. The ecm has a more amplified trough,
swinging a closed low close to the area Tuesday night and Wednesday,
then becomes a noreaster off the New England coast on Thursday. The
GFS is less robust on the Gulf disturbance until it moves to the New
England coast to become a noreaster. Either way, both solutions
produce little to no rain for the area. Temperatures are also warm
enough that any precipitation will fall as rain.
Temperatures will remain cooler than normal through Tuesday.
Temperatures will be close to normal on Wednesday.
Aviation /05z Thursday through Monday/...
as of 1200 am EST Thursday...
VFR conditions expected through the entire taf valid period. A
large area of cold and dry surface high pressure will remain
over the area through early Friday as it pushes slowly southeast
during this time frame. High clouds will stream across northern
areas tonight from a northern stream disturbance moving from the
Great Lakes into New England while another batch of high clouds
skirts across the southern parts of the area due to a southern
stream system moving east-northeast out of Texas. The northern
stream system will move out to sea Thursday while the southern
stream system intensifies, begins to pick up deeper Gulf
moisture and spread northeast into Georgia/SC by early Friday and
then toward the NC coast by Saturday. Expect increasingly dense
mid/high clouds as a result toward the end of the taf valid
period, but cigs will remain aoa100. The latest GFS advertising
potential for low end VFR ceilings creeping north into the
Dan/mtv/w78 area late Thursday/Thursday evening. This seems a
bit agressive, but plausible. Thus, added a group for 050bkn at
kdan late in the taf valid period. Visibility will not be an
issue through 06z Fri anywhere and no precipitation was
advertised at this time.
Winds will be mostly light NE-southeast across the region tonight,
speeds 5kts or less, then light and variable Thursday, but
trending toward the SW 5kts or less.
/Confidence levels in forecast parameters/
ceilings - high,
visibilities - high,
winds - moderate.
Extended aviation discussion...
Models showing potential southeast coastal system moving
moisture toward Dan Thursday night-Friday which could bring
ceilings toward low end VFR. VFR conditions expected Saturday
and Sunday. Some rain on Monday may bring some MVFR conditions.
as of 645 PM EST Wednesday...
All of our climate stations except Danville set new record low
temperatures early Wednesday morning with roa=18, lyh=17,
bcb=12, and blf=6. Then Wednesday afternoon, three of our
climate stations set record low maximum temperatures with
roa=37, lyh=35, and dan=38. In most cases, records were broken
by more than one degree. So clearly a significant early cold
outbreak for the region. Fortunately, upcoming days will
moderate and there are not any signs at least in the next 7-10
days of another cold outbreak of this magnitude. There is minor
potential (mainly kdan it appears) for additional records
tonight, then we should be out of record low temperature
territory for a while.
site record lows/year