Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Remove Highlighting --
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FXUS61 KRNK 231934
Area Forecast Discussion
National Weather Service Blacksburg VA
334 PM EDT Thu Mar 23 2017
High pressure will 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 FRIDAY/...
-- Changed Discussion --As of 214 PM EDT Thursday...
Dome of high pressure along the east coast is going move offshore
tonight into Friday allowing for the area to move into warm
advection. Expect temperatures to drop again tonight to the upper
20s to lower 30s in the east and mountain valleys, except mid to
upper 30s across the higher terrain in the west with southerly winds
picking up more.
Late tonight through Friday, models are showing increasing moisture
in the mid and upper levels tracking from KY/TN into the mid-
Atlantic with some light precip being generated north of our
forecast area. Anticipate some increase in clouds late tonight into
Friday mainly over the west and north, but still looking at more
sun than clouds Friday as temperature warm into the 60s, except some
50s along the Blue Ridge.
-- End Changed Discussion --
.SHORT TERM /FRIDAY NIGHT 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
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 THURSDAY/...
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 /20Z THURSDAY THROUGH TUESDAY/...
As of 110 PM EDT Thursday...
Do not see any aviation issues this period with high pressure
exiting to our east. Will see some increase in clouds at the AC
to CS level overnight through Friday morning, with southerly to
southwesterly winds increasing some over the mountains.
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.