Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 121052

Area Forecast Discussion
National Weather Service Blacksburg VA
652 AM EDT Tue Jun 12 2018

Backdoor cold front will move south today into tonight, then return
as a warm front Wednesday. A cold front will move across the region
from the west on Wednesday night.


As of 300 AM EDT Tuesday...

Frontal boundary will continue to drop south into the Southeast
into tonight. High pressure centered over southern New England this
morning will move southeast into tonight. An easterly flow will
result in plenty of clouds with area of light rain, drizzle and
fog. High temperatures will range from the lower 60s in the north
to the mid 70s in the far west.

A shortwave trough will rotate east across the region tonight. This
will bring its associated frontal boundary east across the region as
well. The combination of light winds and residual moisture will
generate some patchy fog, especially across the Piedmont. Isolated
to scattered showers will develop in the mountains with their closer
proximity to the front. Low temperatures will vary from around 60
degrees in the northwest mountains to the mid 60s across the


As of 500 AM EDT Tuesday...

The cool air wedge will quickly erode Wednesday as a frontal
system approaches from the west aided by a northwest flow upper
disturbance moving southeast from the Ohio Valley. Warm, moist
unstable air will spread back into the area quickly Wednesday
and help support scattered to numerous showers and thunderstorms
once again. The best coverage should be along and west of the
Blue Ridge during peak heating as the disturbance and front move
through the area. SPC has indicated a marginal risk for severe
storms in the far western areas Wed afternoon, but seeing how
instability drops off dramatically east of the Alleghany front,
confidence in the severe moving very far eastward into the CWA
is low. The NAMNest for example, shows any linear organized
convection completely dissipating by evening as it moves off the
Alleghany front. The air mass behind the front will actually be
warmer, yet drier than the wedge air mass currently enveloping
the area.

Thursday will bring increasing amounts of sunshine and push any
threat for showers and thunderstorms mainly to our south. The
southwest part of the CWA, roughly from Watauga to Grayson, will
still be subject to a slight chance of mainly afternoon/evening
convection as the front stalls just to our south. However, most
parts of the CWA should remain dry Thursday. Friday, the front
will drift a bit further south keeping the threat of convection
mainly across GA into SC and then back into TN. With 850mb
temperatures on the increase into the +16C to +18C by the
weekend, look for slightly above normal temperatures with highs
in the 80s, 70s mountains, and lows in the upper 50s to lower
60s Thursday warming to mainly 60s by Saturday. Humidity levels
will definitely be on the increase by the end of the week.

/Confidence Levels/
Temperatures - Moderate
Precipitation Chances - Moderate
Thunderstorm Chances - Moderate
Severe Thunderstorm Threat Wednesday - Low
Wind - Moderate


As of 630 AM EDT Tuesday...

Models are coming into better agreement that a large subtropical
ridge will slowly shift eastward from the central U.S. into the
eastern U.S. during the period. It appears now that the upper
ridge will be close enough to the region, centered over east TN,
to shunt any convective activity across the Great Lakes and into
the northeast. The various models are in good agreement on this
scenario as a tropical low pressure area tracks northward around
the west side of the upper ridge into Texas. This will leave the
Fri-Sun period mostly dry for our area.

With respect to temperatures, indications are that we will be
flirting with the +20C range at 850mb over the weekend,
potentially as warm as +22C. Initially, northeast to east
surface flow will temper the warming, but late in the weekend
into early next week, temperatures could be as much as 10
degrees above normal across much of the CWA with 80s west to
lower 90s east. With dewpoints closing in on 70, it will
definitely feel hot and humid for much of the CWA outside of
the mountains.

By Monday, there are signs that the ridge may shift a bit to the
south and east as an upper trough approaches the Great Lakes and
the tropical disturbance tracks around the west side of the
subtropical ridge into OK/AR. This deeper moisture may combine
with the approaching front toward mid week and bring our region
the next widespread/good chance for rainfall.

Forecast confidence during this portion of the forecast is moderate
on the broader scale pattern but low on the finer details.

/Confidence Levels/
Temperatures - Moderate
Precipitation Chances - Low
Thunderstorm Chances - Low


As of 547 AM EDT Tuesday...

Low clouds,fog and light rain and drizzle will hinder aviation
operations today and tonight. Backdoor cold front will
continue to drift south today and then lift north on Wednesday.
A cool air wedge will settle across our region today into
tonight. MVFR/IFR stratus clouds (isolated pockets of LIFR) will
prevail this morning into this afternoon. Sub-VFR conditions
will continue this evening into tonight.

Enough moisture should be able to collect in the clouds to
continue periods of light showers and drizzle this morning
along with areas of fog. Fog may mixed out in some areas
especially in the west this afternoon, but isolated
thunderstorm may be possible in the far west. The cool
wedge will linger into tonight.

Winds will be light, and mainly from the East.

High confidence in ceilings, visibilities and winds during the
taf period.

.Extended Aviation Discussion...

Wedge will retreat on Wednesday. Conditions are expected to
improve a bit through the later half of next week, but still a
threat of at least diurnally driven showers/thunderstorms with
daily potential for late night fog/low clouds each day during
the period.




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