Severe Thunderstorm Warning 155, NWS Wakefield, VA

AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
427 PM EDT Thu Jul 11 2019

.SYNOPSIS...
A weak trough approaches from the west late this afternoon, with
the trailing cold front crossing the area Friday afternoon,
followed by weak high pressure building into the region for the
upcoming weekend.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 400 PM EDT Thursday...

Latest analysis indicating sfc high pressure well offshore of
the east coast, with sfc low pressure pushing across west
central QC and far northern New England. The attendant sfc cold
front extends S-SW across the interior northeast and into the
mid-south. Regional radar mosaic indicating ISO-widely scattered
thunderstorms just starting to develop over the Blue Ridge and
just E-NE to the Mason-Dixon line. Aloft, the upper level trough
continues to push across ERN Ontario and the upper Great Lakes
down into the ern Ohio Valley.

The upper level trough will progress to the ESE late this aftn
through tonight and will be the most pronounced from the
eastern Great Lakes to New England this evening. The trough will
extend S through the local area but the 500-700 mb winds over
the local area will only avg about 20-25 kt. It will however
provide enough forcing for ascent to produce some more
widespread convection later today. It does become rather
unstable after 19-20z/3-4pm EDT this aftn Thursday aftn. 0-1km
MLCAPE values reach 1500-2500 J/kg per 14z/11 RAP. PW values
increase to ~2" (representing around +2 S.D.) ahead of the
front.

The Day 1 slight risk has been amended to include areas mainly
along and north of a Louisa-Richmond-Salisbury MD line, which
makes sense given timing and orientation of best effective shear
(vast majority of the CWA is in a Marginal Risk). With the
shear modest at best and (typically) fairly weak mid-level
lapse rates, widespread severe weather appears unlikely.
However, given steep low level lapse rates, a few stronger
tstms are possible given aforementioned MLCAPE values combined
with the moisture pooling ahead of the approaching trough. Most
likely threat will be with potential for damaging wind gusts
initially, with threat evolving more to a heavy-rain threat as
the evening progresses. The 500-700 mb flow will be enough to
keep the storms from being stationary, but the low level jet
winds will be almost similar to the winds aloft which would
support training cells and the potential for some flooding,
especially this evening. WPC has oriented our northern third of
the area in a slight risk for excessive rainfall. Area of
greatest concern for our area at this time is the northern neck
and the eastern shore (mainly along and west of US-13). these
areas picked up some heavy rain in spots on Monday and have the
potential to receive some heavier downpours once again...so we
will have to watch these areas particularly closely this
evening.

PoPs for showers/tstms have been pushed into high end likely to
categorical given several successive runs HRRR and NMM. Chc pop
(SCT T wording) continues this evening for the southeast CWA
where timing will likely be later tonight with the main line.
Concern over these areas will be with popcorn/pulsy type
convection this aftn and early evening along the trough axis and
w/ any convective outflows from farther upstream. More humid
than yesterday with highs similar to or slightly higher, mainly
in the upper 80s to lower 90s. Diminishing PoPs late/overnight
from NW to SE with lows 70-75F.

The shortwave trough pivots offshore for Friday. Expect partial
clearing Friday morning. However, CU re-develops by late
morning, with the surface boundary expected to be in place along
the se third of the local area. Low-level moisture will linger
under WNW flow aloft, and some showers/tstms are expected to
trigger in vicinity of the surface boundary (mainly east of
I-95) with PoPs ~30% from Richmond to Northern Neck, and 40% for
Hampton Roads and NE NC during the aftn/evening. The 11/12Z NAM
and ECMWF have been followed in developing sct convection over
the middle peninsula and Tidewater areas. Slight chc or less PoP
has been maintained inland w/downsloping low- level westerly
flow. Still quite warm Friday with highs into the low-mid 90s
inland, and near 90 at the immediate coast. Heat indices are
expected to reach ~100F once again, especially over inland SE
VA/NE NC where the dew pts will be highest.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 400 PM EDT Thursday...

The NW flow aloft will persist through the weekend over the
area. There will be a slight chance of showers and tstm along a
boundary that will remain the in the area. Pops are 20-30%
(highest near the bay and NE NC) where the main lifting
mechanism will be the lingering boundary and sea breeze. High
temperatures on Friday will be in the low 90s with dewpts in the
low 70s. Therefore heat indices will approach 100 inland.
Overnight lows will drop into upper 60s far NW with drier air
filtering in but will be in the low 70s for most of our area. A
second cold front will move south into the area later on Sunday.
There will still be dry air aloft but showers may develop along
the seabreeze and the front Sunday afternoon. Pops are only
15-20% with temperatures climbing in the mid 90s along I-95 and
near 90 at the beaches with downslope flow and clear skies.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 400 PM EDT Thursday...

Still looks at a fairly seasonable with typical diurnally driven
showers/tstms through much of the extended period. The large-scale
pattern from early-mid next week will be characterized by upper
ridging centered over the Four Corners region, with another area of
upper ridging offshore of the Southeast CONUS. The remnant low of
Barry is progged to track slowly NNE invof the Mississippi River
from late Sun-Tue, while our region remains in WNW flow aloft.
Seasonably hot/humid conditions prevail on Mon-Tue with isolated
tstms. PoPs are mainly between 15-30% (highest during the
aftn/evening hours, lowest during the morning). Highs around 90F on
Monday, warming into the low 90s in most areas on Tue (still some
upper 80s on the Lower Ern Shore). Lows on Mon/Tue AM range from the
upper 60s-low 70s (mid 70s possible in coastal SE VA/NE NC).

Still quite a bit of uncertainty regarding the track of the remnant
low of Barry. 12z/11 model consensus has the remnant low approaching
the Appalachians late Tue-Wed before tracking across the Mid-
Atlantic by late Wed-Thu. Not expecting any major impacts from the
remnants of Barry across the local area. However, increased PoPs
slightly toward the end of the extended period (still highest during
the aftn-evening) to account for a potential increase in shower/tstm
coverage as the remnants of Barry approach the region. Continued hot
and humid conditions are anticipated through Wed-Thu with highs
mainly in the 89-93F range and morning lows between 70-75F.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
As of 125 PM EDT Thursday...

VFR conditions all areas from through 20Z. Isolated to widely
Scattered tstms have developed across the Appalachians and wl
slide E into the local area between 21-00Z. Along the coast, sct
tstms hv developed near the coast SW of PHF-ORF with the
seabreeze, and will push across SE VA/NE NC through early
evening. Overall, the highest probability for showers/tstms
will be after 22z/6pm late aftn through this evening. For now
have SHRA and/or VCTS mentioned at main terminals. Showers/tstms
could linger along the coast through 06Z/Fri.

OUTLOOK...A frontal boundary lingers over SE VA/NE NC Friday with
another chc (30-40%) of aftn/evening showers/tstms. Weak high
pressure builds into the area Saturday and Sunday for mainly;y
dry conditions (chance for any showers/tstms less than 20%).

&&

.MARINE...
As of 420 PM EDT Thursday...

No headlines in the short term tonight thru Sat. Late this aftn,
Southerly winds generally 5-15 knots with a few gusts up to 20
kt, were occurring over the waters as a sfc trough was
approaching from the west. Waves were 1-2 ft and seas 2-3 ft.

A sfc trough will approach and push thru the region this evening
and tonight, bringing at least sctd showers and storms. The
pressure gradient will tighten as the trough nears the area with
hi-res guidance showing a modest increase in SSE winds to 10-15
kt with a few gusts to near 20 kt this evening. A loosely
organized line of showers/storms moves out over the Bay and
offshore waters this evening into tonight, bringing a chance
for erratic gusty winds, otherwise SSW winds 10-15 knots can be
expected overnight into Fri morning. The actual cold front will
be slow to cross the region Fri night into Sat morning with
northerly flow, generally 5-10 knots, in its wake. Quiet marine
conditions are expected for the remainder of the weekend with
winds aob 10 knots, waves 1-2 ft and seas around 2 ft.

&&

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

&&

SYNOPSIS...MAM
NEAR TERM...MAM
SHORT TERM...CP
LONG TERM...ERI
AVIATION...MAM
MARINE...TMG

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Special Weather Statement
National Weather Service Wakefield VA
632 PM EDT Thu Jul 11 2019

VAZ064-075-076-519-521-112315-
Western King and Queen-Richmond-Westmoreland-Western Essex-Caroline-
632 PM EDT Thu Jul 11 2019

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT NORTHWESTERN KING AND
QUEEN...NORTHWESTERN RICHMOND...CAROLINE...NORTHWESTERN WESTMORELAND
AND NORTHWESTERN ESSEX COUNTIES...

At 632 PM EDT, radar indicated strong thunderstorms were located
along a line extending from near Fairview Beach to Fort A.p. Hill to
near Ladysmith. Movement was east at 25 mph.

Wind gusts in excess of 40 mph are possible with these storms.

Rainfall amounts of up to 1 inch are possible with these storms.

Locations impacted include...
Colonial Beach, Bowling Green, Montross, Champlain, Milford, Port
Royal, Ladysmith, Newtown, Newland, Loretto, Leedstown, Fort A.p.
Hill, Beazley, Golansville, Hustle, Potomac Beach, Corbin, Elevon,
Supply and Penola.

If you see lightning or hear thunder, you are at risk! Take shelter
indoors immediately. If you cannot find shelter in a building a
vehicle provides safety from lightning.

Strong wind gusts are possible with these storms. These wind gusts
are capable of knocking down tree limbs, small or weakened trees, and
blowing around trash cans, potted plants, lawn furniture, and other
light outdoor objects.

Motorists should use extra caution in the vicinity of these storms.
Be prepared for rapid changes in weather and road conditions. Heavy
rain could cause ponding of water on roads, and possible minor
flooding of ditches and poor drainage areas.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike more than 10 miles away from a thunderstorm.
Seek a safe shelter inside a building or vehicle.

LAT...LON 3821 7695 3817 7681 3806 7682 3801 7690
      3807 7692 3801 7691 3786 7713 3791 7723
      3788 7725 3796 7760 3812 7739 3823 7739
      3825 7735 3822 7729 3825 7723 3823 7725
      3819 7725 3814 7707 3826 7705 3828 7698
TIME...MOT...LOC 2232Z 278DEG 23KT 3827 7729 3810 7724 3797 7745

EI

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