Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 220014

Area Forecast Discussion
National Weather Service Blacksburg VA
814 PM EDT Mon May 21 2018

A southerly flow will continue to push warm and humid air into
our region early this week. The nearly stationary front to our
north will finally push south across our area Wednesday. High
pressure will follow the front Wednesday night and keep the area
mostly dry through Friday.


As of 200 PM EDT Monday...

A blocking ridge centered over Bermuda stretches westward to cover
portions of the southeast and Mid Atlantic states tonight. This
ridge is expected to sink south Tuesday, losing its influence on the
region and allowing an upper level trough and a cold front to
approach the area from the northwest. Over the Gulf states north
into the Tennessee Valley, a weak upper level trough will continue
to draw Gulf and Atlantic moisture northward into the area tonight
and tomorrow.

From this afternoon into this evening, storms will track from the
southeast to the northwest. Tomorrow the steering flow shifts with
storms moving from the southwest to the northeast. All storms will
be slow moving and with the addition of tropical moisture, heavy
downpours are likely this afternoon and evening and again tomorrow
afternoon and night. Since the ground remains wet and creeks,
streams and rivers are elevated, there is a chance for renewed
flooding this evening and tomorrow.

As far as severe threat, model soundings suggest very moist layer
with SBCAPEs around 1000 J/KG this afternoon. Cannot rule out some
isolated wet microbursts but main threat is localized flash flooding.

Temperatures will remain muggy overnight with readings in the 60s.
Temperatures Tuesday will range in the 70s across the mountains to
low to mid 80s east.


As of 300 PM EST Monday...

Scattered to widespread showers and thunderstorms are expected
Tuesday evening into early Wednesday as an upper level
disturbance pushes across the central Appalachians toward the
coast ahead of an approaching cold front. Right now, instability
appears to be modest with this disturbance such that it wouldn`t
be a surprise to see a few cells become strong to severe before
midnight Wednesday, mainly across the Piedmont, but the threat
of widespread severe storms overall appears limited.

The cold front will sink southward, advancing to the Interstate
81 corridor around dawn before loosing speed somewhat as it
continues a southward drift. Believe we will see a
redevelopment of showers across the mountains in the northwest
flow upslope regions, however instability will be limited.
Greater instability will be found in the vicinity of the front
across extreme southern Virginia and northern North Carolina,
where scattered strong storms may redevelop with afternoon
heating where CAPEs may exceed 2000 J/Kg. Outflows from any of
these storms will help to push the front further southward by
evening, clearing the boundary through our area after sunset

High pressure will shift toward New England Wednesday night,
causing winds across the Mid Atlantic to swing more easterly by
Thursday morning. Though instability will be very modest within
the weak high pressure wedging across the region, may see a few
showers/isolated storms develop along the Blue Ridge with
afternoon heating as marine air off the Atlantic is forced into
the mountains.


As of 300 PM EST Tuesday...

Winds will shift more southerly on Friday as high pressure
slides off shore. Though moisture and instability will remain
limited, expect slightly greater coverage of spotty, daytime
heating-driven showers and thunderstorms. Coverage of showers
and thunderstorms will increase during the weekend as a warm
front lifts northward through the mid Atlantic, bringing a
return of deeper moisture from the Gulf coast region. Afternoon
temperatures will range from the mid 70s to the mid 80s each
day, while overnight lows will generally be in the 60s areawide.


As of 800 PM EDT Monday...

Numerous thunderstorms will continue east of a KDAN to KLYH line
this evening where the air mass is still unstable. KLYH will be
starting the TAF forecast period with MVFR conditions and
erratic winds due to a strong thunderstorms. Hi-Res guidance and
HRRR indicated areal coverage of showers and thunderstorms will
diminish after 06Z/2AM.

High confidence of MVFR fog overnight in areas where there has
been rain this afternoon across much of southwest Virginia,
northern North Carolina and southeast West Virginia. Medium
confidence that KLWB will lower to LIFR in dense fog after
08Z/4AM. Ceilings across much of the region will lower to IFR
late tonight.

The fog and stratus that forms overnight will be gone by
12-14Z/8-10AM Tuesday. More thunderstorms are expected Tuesday
afternoon and evening. Confidence low as to the location where
the storms will first develop. MVFR conditions are likely with
any of the storms, otherwise high confidence of a scattered to
broken VFR stratocumulus layer.

.Extended Aviation Discussion...

MVFR showers and thunderstorms are likely again Wednesday.
Conditions are will be drier and are expected to be VFR Thursday
and Friday.




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