Area Forecast Discussion
Issued by NWS Blacksburg, VA

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118
FXUS61 KRNK 231127
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
727 AM EDT Thu Mar 23 2017

.SYNOPSIS...
High pressure will move southeast across our region today and slide
off the coast tonight into Friday. A warmer southerly flow will
develop Friday into the weekend ahead of a slow moving cold front
that will approach the region Sunday. A series of upper-level
low pressure areas will track across the central and southern
U.S. through next week keeping an unsettled weather pattern in
place.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 300 AM EDT Thursday...

High pressure over western Pennsylvania this morning will move
southeast this afternoon and drift east and off the Mid-
Atlantic coast tonight into Friday. Cool easterly flow will keep
the areas east of the Blue Ridge just as cool as the mountains.
High temperatures this afternoon will range from the mid 40
across the northern mountains to lower 50s in the Piedmont. The
far western mountains may make a run at the mid to upper 50s.
Clear to partly cloudy conditions are expected tonight. A warm
front will lift northward into the Ohio Valley late tonight into
Friday morning. Any showers associated with the warm advection
and warm front will remain to our north. With dry airmass across
our region, leaned towards the drier GFS/NAM solutions over the
ECMWF which clips the northern edge of Greenbrier and Bath
counties with some moisture about 12z Friday. Low temperatures
will range from the mid 20s in the northern mountains to the mid
30s in the western mountains.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
As of 400 AM EDT Thursday...

A pattern transition will be underway at the beginning of this
period taking us from the predominant northwest flow aloft we
have been in for much of March so far to a very active,
unsettled zonal flow with numerous embedded southern stream
vigorous upper-level lows. This pattern change will bring
frequent rain chances to the area, and some thunderstorms as
well, along with an extended period of unseasonably warm
temperatures. In fact, after Friday morning, we may have seen
the last of any freezing temperatures at most locations in the
RNK CWA for the rest of March. Looking at the global picture,
we can see the support for this pattern as a broad area of low
pressure covering much of the Pacific sends a steady stream of
disturbances eastward into the U.S. By the same token, this
zonal flow will keep the Canadian/Arctic air locked up north and
instead supply the U.S. with a steady stream of Pacific-based
air masses.

Friday will be the transition day as the current area of cold,
dry high pressure moves east off the coast allowing a return
southerly flow of warm, moist air from the Gulf to evolve across
the region. Temperatures will be on the order of 10-15 degrees
warmer than what will be seen on Thursday.

On Saturday, a short wave ridge across the eastern U.S. will
evolve in advance of the first deep upper low to lift out of the
Southern Plains. Thus, Saturday will be a warm day with
increasing clouds and possibly some late day showers advancing
from the Tennessee Valley into far southwest VA or southern WV.
The upper low will then take a more northward track into the
Ohio Valley and weaken as it encounters the upper ridge along
the eastern seaboard. Nonetheless, sufficient forcing,
instability, and moisture will exist as this system rotates with
a negative tilt into the Ohio Valley, for a good chance of
showers across the region Sunday. Therefore, have advertised
likely to categorical pops Sunday. Temperatures Sunday will be
just a tad cooler thanks to cloud cover and precipitation, but
will remain unseasonably mild.

The main questions during the period will be QPF for Sunday and
thunder chances. With regard to QPF, models are in fairly good
agreement that we should see 1/2 to 3/4 inch of rain Sunday with
this first system. Instability is meager and dynamics are
weakening. Have included a slight chance of thunder in the far
western areas where activity from the TN Valley could arrive
before weakening. Severe weather does not appear to be an issue
with this first system.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
As of 430 AM EDT Thursday...

The next in a series of upper-level low pressure areas will move
from the Southern Plains into the Tennessee Valley/Central
Appalachians late Monday into Tuesday. While this system will
again be weakening as it moves toward the western Atlantic upper
ridge, it will have somewhat better dynamics and instability to
work with than the Sunday system. Therefore, have included a
slight chance of thunder for all areas Tuesday afternoon. This
still does not look like a severe weather system, but slightly
better potential for such than the Sunday system. Rainfall
amounts again appear to be in the 1/2 to 3/4 inch range over all
with this event.

A quieter midweek period appears in order as the next upper-
level system deepens and slows as it moves into Texas and an
upper ridge amplifies across the eastern U.S. A weak area of
high pressure from the Great Lakes filters into the area for
midweek. By Friday, this aforementioned system will move into
the Mid-Atlantic region as yet another upper-level low pressure
area moves from the southwest U.S. into Texas.

Temperatures will remain unseasonably mild through the period
with no significant intrusions of Canadian air. A slight cooling
will be noted midweek, but temperatures will still be left above
normal. Look for maximum temperatures much of the week in the
60s west to the 70s east, with lows mainly in the 40s and 50s.

&&

.AVIATION /11Z THURSDAY THROUGH MONDAY/...
As of 720 AM EDT Thursday...

VFR conditions will continue through the TAF valid period as a
large area of Canadian high pressure drifts across the region,
then moves off the east coast Friday. Mid-level warm advection
will result in an increase in mid/high clouds after 06Z, otherwise
just looking for SCT cirrus through the day today. Visibility
will be VFR through the period with no fog development. Winds
will veer around from the northeast to the southeast through the
period at speeds of 4-7kts, generally less after 00Z.

High confidence in ceilings and visibilities through the TAF
valid period.
Medium to high confidence in wind speed/direction through the
TAF valid period.

Extended Aviation Discussion...

Good flying weather is expected to linger into Friday night before
moisture starts to increase over the weekend ahead of an upper-
level low pressure area moving northeast from the Southern
Plains. Precipitation is not expected until Sunday when sub-
VFR conditions become more of a possibility. Otherwise looking
at overall VFR to start the weekend with most lower cigs
remaining west of the area until later Sunday at this point.
Periods of unsettled weather will continue into the first half
of next week as a series of upper-level lows track from west to
east across the U.S.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.

&&

$$
SYNOPSIS...KK
NEAR TERM...KK/RCS
SHORT TERM...RAB
LONG TERM...PM/RAB
AVIATION...KK/RAB



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