Severe Thunderstorm Warning 54, NWS Wakefield, VA

Area Forecast Discussion
National Weather Service Wakefield VA
407 PM EDT Tue May 22 2018

.SYNOPSIS...
A warm front across the eastern part of the local area will move
northeast tonight. A cold front will cross the region on
Wednesday, followed by a period of dry weather Thursday and
Friday under the influence of high pressure.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
As of 300 PM EDT Tuesday...

Thunderstorms have developed this afternoon across the mountains of
northern VA/WV in association with the subtle short wave over the
Ohio Valley. Best flow aloft generally remains just north of the
area, but given the strong instability and marginal deep layer shear
profile of 25-30kt, a severe thunderstorm watch has been issued for
the northern part of the forecast area generally north of Richmond.
The best chance for severe weather would likely be across the far
north (Caroline/Louisa Counties through the northern neck) due to
the better kinematics, however overall the best severe threat seems
to be north of the area. Main concern could be another period of
locally heavy rainfall with storms possibly training across the
north this evening. These storms should diminish relatively quickly
after sunset due to loss of daytime heating.

Meanwhile, storms have also developed across the far south in
association with a weak surface trough. These are not expected to be
severe, but again, given the high precipitable water values of
around 1.75 inches, heavy rain is expected.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
As of 300 PM EDT Tuesday...

The surface front over the Ohio Valley will slowly move through the
area on Wednesday. Models suggest the front will take pretty much
the entire day to move through the region, and as a result much of
the southern half of the local area will remain south of the front
through the afternoon. This should allow for thunderstorms to once
again develop along the front in the afternoon. Winds aloft are only
marginal for severe storms in the afternoon with only about 20-25 kt
of shear during the afternoon. Could not rule out some line segments
with gusty winds but organized severe unlikely. After the front
passes through Wed evening, expect dry and seasonable weather Thu
into Friday.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 320 PM EDT Monday...

A strong surface ridge and northwest flow aloft with the upper
ridge axis to the west over the Mississippi Valley will provide
dry weather with moderate temperatures for the beginning of the
extended forecast. Expect highs in the low to mid 80s Friday and
the mid to upper 80s on Saturday. Overnight lows in the mid to
upper 60s Friday night. But the upper ridge will erode through
the holiday weekend with a gradual increase in moisture as it
appears that another area of low pressure will form in the
northeastern Gulf of Mexico by Sunday and push more tropical
moisture northward into the region. This could allow for more
showers and tropical downpours for Sunday and again on Monday.
The big model difference in the models is the handling of a
backdoor cold front between the 12z GFS and ECMWF with the GFS
pushing the front south through the area and the ECMWF keeping
the boundary well north of the area. In either case, the chance
for showers and some possibly heavy rainfall exist for the
second half of the Holiday weekend. If the GFS is right with the
front Monday could be a damp cool rainy day while the ECMWF
would lead to more periodic showers with some breaks. At this
time of year, seems more likely the for the front to hang north
of the area. So have kept the temperatures up more in the low to
mid 80s for Sunday and Monday.

&&

.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
As of 300 PM EDT Tuesday...

Mostly VFR conditions expected this afternoon, although localized
IFR possible early this afternoon at ECG with thunderstorms.
Otherwise, another round of showers and thunderstorms possible at
RIC and SBY late this afternoon and this evening as the storms
currently on the mountains move eastward. Localized IFR possible
especially at RIC, but timing is difficult. These should diminish
this evening due to loss of daytime heating. VFR expected overnight
into Wednesday, although additional storms possible across the far
south late Wed morning into Wed afternoon.

Outlook...The cold front moves through Wednesday/Wed evening with
high pressure building in for Thu/Fri. VFR conditions expected
beyond Wednesday.

&&

.MARINE...
As of 405 PM EDT Tuesday...

The surface warm front is straggling along the northeast coast
near OXB and it continues to gradually lift NE away from the
region. The flow is now turning to the south and southwest this
afternoon and evening. Some showers and thunderstorms may impact
the waters this evening as the lee side trough pulls away from
the mountains. But the winds will generally remain out of the
south to southwest at 5 - 10 KT overnight. The next cold front
will drop SE through the region on Wednesday afternoon and
evening. The flow will turn nw behind this front and there will
be a short increase in winds to about 15 KT as slightly cooler
and drier air pushes in behind front. Once the front clears the
area, high pressure will settle over the waters for Thursday
into Friday night. This will provide light winds and benign seas
through Friday night.

On Saturday, the flow will return to the south as the high
pressure system slides off the SE US coast. Expect some increase
in winds to 10 - 15 KT.

&&

.HYDROLOGY...
As of 625 AM EDT Tuesday...

Flood warning continues for the Appomattox River basin. Mattoax
is now forecast to reach moderate flooding by late tonight/early
Wednesday morning. Warning has been dropped at Stony Creek,
with river falling below flood stage earlier this morning.
Additional flood warnings continue for the Chickahominy,
Mattaponi rivers, as well as the Pocomoke River in MD. (allowed
South Anna/Pamunkey river to expire). See FLWAKQ or FLSAKQ for
more details.

&&

.CLIMATE...
As of 145 AM EDT Tuesday...

* RIC monthly rainfall total through 5/21 remains at 8.84"
  (already ranks as 5th wettest May on record). (precipitation
  records date back to 1880)

* SBY monthly rainfall total through 5/21 remains at 8.52"
  (already ranks as 3rd wettest May on record). (precipitation
  records date back to 1906)

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...None.

&&

SYNOPSIS...LKB/MRD
NEAR TERM...MRD
SHORT TERM...MRD
LONG TERM...BMS
AVIATION...MRD
MARINE...ESS
HYDROLOGY...
CLIMATE...

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