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fxus61 krnk 240852 
afdrnk

Area forecast discussion
National Weather Service Blacksburg Virginia
352 am EST Fri Feb 24 2017

Synopsis...
low pressure was over Missouri with a cold front trailing into
the Southern Plains. By Saturday morning this low will be in the
Great Lakes with front extending into western Virginia and into
the Gulf of Mexico. High pressure returns to the area on
Sunday.

&&

Near term /through tonight/...
as of 330 am EST Friday...

Satellite pictures showed some high clouds from Kentucky through
central Virginia this morning but cirrus was thin enough to
allow temperatures to drop to near the dew point. Patchy fog
had developed and will continue to expand in coverage through
sunrise. The fog that does develop will mix out and dissipate by
mid morning. Scattered to broken stratocumulus is expected this
afternoon.

Clouds will increase overnight as a cold front approaches the
region. Models have similar timing with the GFS a few hours
faster than the other models. Have slowed down the onset of
precipitation in southern West Virginia and southwest Virginia
until after 09z/4am. Lifted index forecast was just below zero
along the boundary late tonight with convective available potential energy as much as 300 j/kg
so have left slight chance of thunder in before 7am/12z.

As pressure lower over the mid Atlantic region today and the
narrow axis of high pressure retreats east, winds will turn to
the south-southwest. Wind speeds will increase at higher
elevations tonight as the pressure gradient tightens in advance
of the front.

Warmer guidance was used as the basis for maximum temperatures
today. Clouds and mixing will keep temperatures mild tonight.

&&

Short term /Saturday through Sunday night/...
as of 300 am EST Friday...

A shortwave trough will move from the Great Lakes region through
much of the northeast by early Sunday. A well advertised cold front
will move east across our area Saturday and push out into the
Atlantic Ocean Saturday night into Sunday. The main batch of
convection, a pre-frontal line will cross our area during the
morning into the early afternoon. The cold front to cross late
morning into the mid afternoon, and the associated 850 mb front to
cross the area late afternoon into the evening. The latest day 2
convective outlook from the Storm Prediction Center offers a
marginal risk of severe weather across the central and northeastern
sections of the forecast area with the passage of the cold front.
Instability will be the main limiting factor but a conditional risk
for localized damaging gusts is possible with the convective line
during the morning.

Winds will increase in the wake of this front, ushering in colder
air by the afternoon, especially in the west. Used an non-diurnal
temperature curve with areas in the west reaching early high
temperatures with temperatures falling off in the afternoon. Eastern
portions of the forecast area should realized their high
temperatures in the afternoon times, but still experience falling
temperatures before sunset. High temperatures on Saturday will range
from the lower 50s in the northwest mountains to near 70s across the
Piedmont. Actual highs will be dependent on the exact timing of the
front.

One of the challenging aspects of the forecast is whether there is a
break in the action like suggested by European model (ecmwf) before upslope kicks in.
Elected to keep continuity with lingering upslope showers across the
West Mountains persisting through the afternoon. Enough colder air
will reach the highest peaks in this region for a mix with, or
change over to, light snow. By Saturday night, snow showers and snow
flurries are expected for the western upslope locations. Given how
mild conditions will be prior to the arrival of snow showers, little
if any accumulation is expected. Western Greenbrier County in West
Virginia has the best chance for any measurable snowfall, with up to
one-half inch possible. Low temperatures Saturday night will vary
from the upper teens in the northwest mountains to the lower 30s in
the Piedmont.

The wind gusts at higher elevations may approach Wind Advisory
levels at the highest elevations during the Saturday afternoon and
Saturday night. However, most gusts across the mountains will be
more in the 25 to 40 mph range with 20 to 30 mph across the Piedmont.

High pressure builds over our area Sunday and shift east to the
Atlantic coast Sunday night. Dry weather is expected on Sunday
with plenty of sunshine. High temperatures Sunday afternoon will
warm into the upper 30s in the northern mountains to the mid 50s in
the Piedmont. On Sunday night, south to southwest winds will be on
the increase again as the influence of the high pressure wanes, and
another potential shortwave trough approaches from the west. At this
time, the European model (ecmwf) and GFS keep the moisture to our west. Low
temperatures Sunday night will have readings from the mid 20s across
the mountains to the lower to mid 30s across the Piedmont.

&&

Long term /Monday through Thursday/...
as of 300 am EST Friday...

There still remains difference in the model guidance regards the
precipitation potential on Monday and Monday night. The GFS has back
off on its agressive southern stream system heading northeast, and
has increased its moisture with the north stream shortwave heading
east out of the Ohio Valley. The European model (ecmwf) is weaker with northern
shortwave and slower regarding southern stream feature, with
precipitation arriving Monday night. Decreased pops for Monday as
suggested with superblend and continued chance of rain for Monday
night.

Through Wednesday, the region is expected to remain in a deep
southwest flow in advance of a developing trough across the Central
Plains states. The GFS continues to be more progressive in depicting
pieces of energy streaming across the area, each with the potential
for additional rounds of precipitation, especially on Wednesday. Our
forecast will continue to reflect the superblend solution that
accounts for these features, but on a diluted magnitude.

Wednesday afternoon into Wednesday evening, the main upper trough
and associated cold front are expected to race across the area. Look
for another a line of convection to move through the region, with
the potential for isolated thunderstorms. Gusty winds from the
northwest are again forecast to develop in the wake of the cold
front. Anticipate upslope rain and snow showers across portions of
southeast West Virginia, south into the northern mountains of North
Carolina late Wednesday night, into and through the day on Thursday.
Placed isolated to scattered pops in the northwest for Friday and
dry out Friday night.

Temperatures during this portion of the forecast will trend from
near normal on Monday to around 10 to 15 degrees above normal for
Tuesday and Wednesday. Thursday will be slightly cooler with
readings around five degrees above normal. Cooling trend expected
into Friday with temperatures returning towards normal.

&&

Aviation /09z Friday through Tuesday/...
as of 1137 PM EST Thursday...

Confidence is moderate through mid morning on cigs/vsby in
relation to fog and/or stratus. Confident enough to keep at
least MVFR to IFR fog in and think a bit of bkn/ovc stratus may
occur with the fog as well at times. Blf looks like the only
site that may escape any fog or low clouds with more mixing.

Any low clouds/fog will dissipate Friday morning followed by
redevelopment of VFR convective clouds by the afternoon.
Precipitation chances tomorrow appear limited with a cap evident
on model soundings. Winds will generally be light through the
period with no significant gusts expected.

Any showers or storms appear to hold off until after this taf
cycle.

Will continue to indicate amend not schedule at klyh due to
persistent ASOS equipment issues.

Extended aviation discussion...

Band of showers and isolated thunderstorms with MVFR conditions
arrive late Friday night into early Saturday along and ahead of
a strong cold front. Drier weather and increasing northwest
winds follow behind the front on Saturday afternoon through
Sunday.

Approach of another front Monday will provide increasing clouds
and possibly showers and MVFR cigs to blf/lwb late in the day.

A warm front is expected to stay near US into Tuesday keeping a
threat of showers around with sub-VFR possible.

&&

Climate...
as of 345 am EST Friday...

February 24 record highs:

Bluefield 71 (1961)
Danville 79 (2012)
Lynchburg 79 (2012)
Roanoke 80 (1985)
Blacksburg 73 (1975)

&&

Equipment...
as of 700 PM EST Thursday...

The automated observation system at Lynchburg (lyh) continues to
experience problems. Electronics technicians will investigate
further on Friday.

&&

Rnk watches/warnings/advisories...
Virginia...none.
NC...none.
WV...none.

&&

$$
Synopsis...air mass
near term...air mass
short term...kk

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