Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 230552

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

A large area of high pressure will settle across the region
tonight into Thursday. The high will slide off the coast
Thursday night and push offshore Friday. A warmer southerly
flow will develop Friday into the weekend ahead of a slow moving
cold front that will approach the region Sunday.


As of 152 AM EDT Thursday...

Made some minor adjustments in temperatures and dew points for
this morning. Overall, forecast is in good shape.

As of 840 PM EDT Wednesday...

Winds slowly diminishing and should become rather light after
midnight into sunrise on Thursday as the center of the surface
high slides about overhead by morning. Air remains very dry with
dewpoints still in the teens while evening soundings show only
about a tenth of an inch of PW. This should allow for an
accelerated drop in temps overnight once winds decrease more
under clear skies. Thus dropping lows a few degrees more across
the valleys and in spots out east with perhaps isolated upper
teens in some of the deeper valleys. Otherwise few changes with
a cold overnight for late March with lows mainly in the 20s.

Previous update as of 702 PM EDT Wednesday...

I`ve made essentially noise-level changes to winds and
dewpoints with this update. Ridging continued to extend
southeastward from a strong anticyclone centered near Cleveland
as of 22z. North- northwesterly gradient flow still continues
around 6-13 kts, and have tried to better account for this in
the grids through 10 pm. However wind speeds do steadily slacken
starting around mid/late evening along with a veer to a
northeasterly direction. Expect rapid hourly temperature falls
given the dry air mass with sunset and particularly after
midnight as winds decouple. Though dewpoints are quite low, only
little recovery anticipated as air mass further north is nearly
as dry, so I did lower these into the overnight.

Previous near-term discussion issued at 220 PM follows...

A strong area of high pressure will track from the Great Lakes
tonight and be centered over Virginia tomorrow morning. This high
will keep the area cool and dry with very little in the way of cloud
cover. Winds will subside this evening and under clear skies,
overnight lows will radiate down into the 20s. Cool northeast flow
will keep the areas east of the Blue Ridge just as cool as the
mountains. high temperatures Thursday will range from the mid 40s to
lower 50s.


As of 300 PM EDT Wednesday...

High pressure will drift east and off the Mid-Atlantic coast
Thursday night into Friday. Southerly wind flow will develop
on the back side of the high with increasing moisture aloft
resulting in mid/upper level cloudiness Friday into Saturday.
The boundary layer is forecast to remain dry, thus little or no
precipitation threat anticipated through Saturday, although
can`t rule out some virga or a sprinkle west of the Blue Ridge.

By Saturday night, enough moistening may take place for
measurable rainfall after midnight, but again threat will be
mainly along and west of the Blue Ridge with amounts less than a
tenth of an inch.

Temperatures through the weekend will gradually moderate with
lows in the 30s Friday morning, then into the 40s by Saturday
morning. Daytime highs will also inch upward with highs in the
50s to around 60 Friday then into the 60s to lower 70s by Sat.


As of 315 PM EDT Wednesday...

The models have come into fairly good agreement that a series of
upper level low pressure systems will track across the country
from the west coast this weekend and into next week. The first
in this series of upper lows is slated to track through the
central plains this weekend, then lift towards the northeast and
weaken as an open wave as it crosses the Ohio Valley Sunday. A
second low will take a similar track Monday into Tuesday, but
may offer a slightly different solution with respect to a shot
of colder air for mid week as it phases with a short wave moving
east along the U.S./Canadian Border. Both systems suggest an
unsettled but mild weather pattern for Sunday through Tuesday
with a potential brief intrusion of cooler weather Wednesday
before entertaining another round of unsettled weather toward
the end of the week. Due to the weakening nature of these
systems, the potential for thunderstorms and severe weather for
our CWA appears to be low.

For Sunday, the surface cold front, from the first area of low
pressure is forecast to enter the western CWA early, with clouds
and showers potentially entering the forecast area before
daybreak. Forecast consensus is for about a tenth to a quarter
of an inch of rain Sunday. The actual front is of pacific
origin, so anticipate little or no temperature change. If
anything, an increase in dewpoints may actually make it feel
warmer during the day, and will definitely be warmer at night
due to the higher dewpoints maintaining elevated temperatures
at night.

For Monday into Tuesday, the next upper low will track into the
Ohio Valley, resulting in another round of showers, favoring
Tuesday more so than Monday with respect to pops/qpf.


As of 152 AM EDT Thursday...

VFR conditions will continue through Thursday night under
strong high pressure. Clear skies will prevail through 23z
Thursday with some mid and high clouds. Light and variable
winds will veer to east to southeast 3-6 kts this afternoon as
ridge axis shifts east into eastern Virginia. A weak shortwave
passing to our north may generate some mid level clouds late
Tonight into Friday.

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

Extended Aviation Discussion...

Good flying weather is expected to linger into Friday night before
moisture starts to increase over the weekend ahead of a cold
front approaching from the west. However, 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. The potential for sub-vfr
conditions will continue into Monday with convection.




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