Area forecast discussion
National Weather Service Wakefield Virginia
1027 PM EDT Sat may 18 2013
Synopsis...
a weak front remains nearly stationary over North Carolina tonight. This
front is expected to lift to the north on Sunday...and move north
of the region by Monday afternoon. A ridge of high pressure off the
southeast coast will prevail into the middle of the week.
&&
Near term /until 6 am Sunday morning/...
latest weather analysis continues to depict a stationary front/boundary
over NC...with a rather broad middle/upper level trough situated from
Kentucky down into the Carolinas. Latest radar shows the more organized
activity from earlier in the evening now off the coast...but with
another batch of moisture pushing north into south central Virginia from
central NC.
Tough call as to the evolution of this next round. Models generally
confine it to Piedmont counties south of fvx...but will broad-
brush some likely/60% probability of precipitation over S central Virginia as well as interior NE
NC through 07z...with 40-50% over most of the remainder of the County Warning Area
(except will also carry likely probability of precipitation across portions of the eastern
shore). Due to fairly weak middle/upper dynamics do not expect the
amount of coverage or intensity of precipitation as last night.
Concerning thunderstorms...will keep mention of isolated convection over
far southern Virginia/NE NC going after midnight where ml cape on the
order of 500 to 1000 j/kg persists (just rain showers farther north). Min
temperatures drop very little from current values with mainly overcast skies
and mixing...low to middle 60s for most locations. Added fog to northwest
sections of the County Warning Area per latest observation...although not expecting visibilities
to drop to much less than 1 mile due to cloud cover.
&&
Short term /6 am Sunday morning through Tuesday/...
wet weather will continue Sunday through Monday as the stalled front
begins to lift northward. Also an upper level trough over the Ohio/Kentucky area
will move across the middle Atlantic region Monday. Precipitation is expected to
be most widespread over western portions of the area Sunday per
model guidance where upper level support will be best. Probability of precipitation increase
once again Monday mainly across southern portions. As the trough moves
off to the east...precipitation decreases over western portions by Monday afternoon.
High temperatures Sunday and Monday will be warmer...generally in
the upper 70s to lower 80s with slightly cooler readings near the coast.
Lows will range through the 60s.
During the remainder of the short term...while the upper level
trough moves off to the east...further upper level impulses are
expected to impact the area. Precipitation diminishes by around midnight
Monday night. Some redevelopment of thunderstorms is expected Tuesday afternoon
mainly over southern Virginia/NE North Carolina. High temperatures Tuesday are
forecast to reach into the middle to upper 80s at most locations.
72 hour quantitative precipitation forecast totals forecast to range from 1 to 2 inches with
local amounts to 3 inches possible across the Piedmont to around
a half inch to an inch toward the coast. Some issues on area
rivers are possible early this coming week. See Hydro section below.
At this time...there are no plans for a Flood Watch but this will
continue to be monitored.
&&
Long term /Tuesday night through Saturday/...
models similar over this time period with the timing of another trough
deeping at 500 mb toward Friday and Saturday. This will usher a
stronger cold front through the region Friday into Saturday. The
front will have some showers and thunderstorms with it as it moves
through. Before that a frontal boundary remains nearly stationary
across the Great Lakes and New England. South of this area will have
general south to southwest flow across the area. Could see an
isolated afternoon thunderstorm. Any thunderstorms that form north
along the boundary could push into the northern part of the area
during the evenings. Temperatures will be at or above normal until
the front passes. Then temperatures will drop back on Saturday to at
or below normal.
&&
Aviation /02z Sunday through Thursday/...
scattered showers and a few thunderstorms continue to deveop over the region
as southeast-S flow brings lots of moisture into the area. A stationary front
over NC will slowly lift north of the area by late sun into Monday.
The front will enhance the development of shower/thunderstorms across the
region. Ceilings and visibility have been very difficult to forecast. IFR
conds now occuring at ric and sby while other terminals have
MVFR/VFR conds. More rain is expected to move into the County Warning Area from
the SW during the overnight hours and persist into early sun
before the front lifts north. Guidance suggests MVFR/IFR ceilings
during the overnight at most terminals which will be enhanced by
precipitation and southeast flow. Expect gradual improvement in conds by Sun
afternoon but there will continue to be a chance for showers/thunderstorms into Monday as
weak upper trough moves through the region. Think there might be chance
for IFR fog especially for Monday night as high moves over area.
&&
Marine...
difficult forecast initially to see if we get to small craft
conditions on the Bay. All high res models would support a period of
small craft winds into this evening. Seeing winds staying close but
just under small craft at 19z. Expect that by 20z most sites will
have small craft conditions. This wind increase seems to be
associated with a weak low pressure moving along the boundary south
of the area increasing the southeast winds. With continued east to
southeast winds tonight will see seas increase to 5 feet along the
northern coastal waters. Seas will drop back to under 5 feet on
Sunday. Winds will also diminish and gradually become more southerly
on Sunday and then southwest on Monday as a warm front moves slowly
north through the waters. The warm front will slowly lift north from
North Carolina tonight and Sunday and finally be north of the waters
on Monday a weak upper low will move slowly east from the Midwest
and eventually off the coast by Monday night. These features will
continue showers and thunderstorms at times through Monday.
&&
Hydrology...
rainfall over the Piedmont and ridges to the west are forecast to
bring significant rises to area rivers by Monday and Tuesday. Some
locations will likely experience action stage and may possibly
have minor flooding. This will depend on which basins locally
heavy rainfall sets up which is too early to determine.
&&
Equipment...
akq 88d radar is back in service.
&&
Akq watches/warnings/advisories...
Maryland...none.
NC...none.
Virginia...none.
Marine...Small Craft Advisory until midnight EDT tonight for anz630>632-
634-638.
Small Craft Advisory until 6 am EDT Sunday for anz650-652-654.
&&
$$
Synopsis...lkb
near term...lkb/lsa
short term...lsa
long term...jab
aviation...jef/jao
marine...jab
hydrology...akq
equipment...akq
