Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 231500

Area Forecast Discussion
National Weather Service Blacksburg VA
1100 AM EDT Sun Jul 23 2017

A slow-moving cold front will drift southward over the Mid
Atlantic during today and Monday. High pressure should build to
the north by Tuesday and Wednesday. The aforementioned front
should stall to the south and begin heading back north as a
warm front later in the week.


As of 1030 AM EDT Sunday...

Upstream mesoscale convective systems are weakening as they
reach the Appalachian Mountains at this time. Scattered showers
are making it through Lewisburg to Amherst. Today will be
rather active with a slow-moving cold front sagging southward,
but our region has started with a fairly large amount of
residual cloud cover. There will be some breaks in the clouds
for sunshine to push temperatures into the 80s and 90s for
highs although not as hot compared to yesterday. Mesoscale
models reveal convection developing in the afternoon along the
southern Blue Ridge. The Storm Prediction Center has most of
our region in a slight risk for severe thunderstorms due to
damaging wind gusts. Given the environmental conditions, it
appears the best bet for any severe weather to develop will be
along the Blue Ridge toward the Piedmont south of Route 460.

For tonight, surface front still to our north and seems most
models are favoring some lull in storm coverage behind the
afternoons activity. However, there is enough agreement to keep
a better threat of storms in the west closer to higher theta-e
ridging and moisture transport. Will side with drier wx
overnight, with muggy temps continuing with lows in the mid to
upper 60s west, to lower 70s east.


As of 325 AM EDT Sunday...

Front looks like it stalls/slows over the forecast area Monday but
deeper moisture slides further south. Going to see a little drier wx
per most model solutions with a few showers/storms over the
mountains, and across the southern CWA, though isolated convection
seems plausible anywhere Monday. Staying very warm with a westerly
flow increasing, but dewpoints start to drop some. Highs should
range from the lower to mid 80s mountains, to lower to mid 90s east.

By Monday night into Tuesday the axis of the upper trough slides
east and shifts the frontal boundary further south. As this occurs,
high pressure over the Great Lakes shifts east Tuesday afternoon
into New York. Should see a shift in the winds from west/northwest
to northeast. Some drying to take place but with southeast flow
arriving on the backside of the front into the southern
Appalachians, showers/storms may stick around in a scattered fashion
over the High Country of NC into far Southwest Virginia, and
possibly east toward Martinsville/Reidsville.

Some noticeable change in dewpoints, but overall temperatures should
run at or just above normal.


As of 1100 AM EDT Sunday...

Wind flow around high pressure centered over New England will
result in an easterly breeze on Wednesday, bringing cooler
Atlantic air into the region. As such, afternoon high
temperatures will likely be the coolest of any day this week,
ranging from the mid/upper 70s west to low/mid 80s east. The
upslope wind flow will also support spotty showers/thunderstorms
during the afternoon and evening, with greater coverage across
the mountains and foothills.

High pressure will shift off the New England coast Wednesday
night, allowing winds to turn more southerly across the mid-
Atlantic by Thursday, making for a return of warmer, more humid
air. Strong daytime heating will support pulse variety showers
and thunderstorms, a few of which will likely become strong for
brief periods of time during the afternoon and evening.

A cold front will make its way across the mid Atlantic on
Friday, triggering more organized/widespread shower and
thunderstorm activity. Latest run of the weather forecast models
indicate that the front will clear our area to the south by
Saturday morning, bringing drier air in its wake. Have therefore
lowered rain chances for next weekend, though isolated
showers/storms cannot be ruled out.


As of 725 AM EDT Sunday...

Have showers affecting LWB/BLF and BCB between 12-14z, but
instability has weakened so thunder threat has diminished except
west of BLF, so left VCTS here.

Should be a lull after 15-16z, before more storms fire up in the
afternoon. Latest high-res models are mainly developing storms
east of the Blue Ridge but models also are developing more
organized convection over KY after 21z which could impact the
mountains afterwards. Confidence is medium that showers and
storms will be around the region this afternoon/evening but low
on which airports if any get affected. So for now will keep VCTS
in all tafs in the mid afternoon to early evening period.

Thereafter, after 03z, models showing less coverage so no
mention in the tafs. Will have to see if we clear out enough
late tonight for fog, but for now am leaning against it.

So in summary look for VFR outside of storms, with some MVFR or
IFR in storms.

Winds will pick up in the 6-12kt range after 16z from the west
or southwest, then drop off after dusk. Winds near or in storms
will be gusty and erratic, some storms could bring damaging
winds, so those with aviation interests should monitor latest
radar and forecasts.

Aviation Extended Discussion...

The cold front currently to our north should be near the NC/VA
border by Monday evening. This leaves a baroclinic zone in or
near the area through much of the extended period. Additional
upper- level disturbances are progged in northwest flow to
impact the area, leaving an unsettled weather pattern in place.
The most likely areas to see convection, at least during the
first part of the week would be near the NC/VA border, mainly
affecting KDAN. Late/night early morning fog can be expected in
the usual locations, otherwise outside these concerns and
scattered convection, mainly in the south, look for mostly VFR




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