Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 291829

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
229 PM EDT SUN MAY 29 2016

Tropical Depression Bonnie will linger along the Carolina coast
line through the first part of this week while an upper level
trough will track north of the area through Monday. High pressure
briefly builds in before a surface boundary impacts the region
Tuesday. High pressure returns for the second half of the week
with a cold front moving through late in the week.


Bonnie remains down along the South Carolina coast with moisture
streaming to the north from the system. Please refer to the NHC
for official forecasts.

Rain impacting portions of the western CWA this afternoon and is
timed to reach southern fringes of the area by 3 pm. Upper lvl
trough is noted on water vapor imagery over the western Great
Lakes region, which will aid in the placement of the moisture
advection from the tropical system up across the Mid- Atlantic as
it approaches from the west, producing a narrow conduit for the
moisture in combination with the ridge sitting just to the east of
us. As such, still anticipating more widespread rains to move in
late this afternoon and into tonight, with latest hi-res model
runs showing the best chance for moderate to periods of heavy rain
coming this evening and then again late tonight mainly east of
the Blue Ridge. While 1-2 inches of rain is expected, thinking
that it will mostly occur over a temporal period that will keep
flash flooding threats to a minimum. The main flooding concerns
will be the typical urban, low lying areas.


The previously mentioned upper level trough will pass to the north
Monday with ridging persisting just off shore. Energy associated
with Bonnie will split off from the main area of low pressure and
round the western fringe of the ridge, getting caught up with the
passing trough and move through the Mid-Atlantic during the day.
This will act as a trigger for afternoon convection across the CWA
Monday with plenty of moisture and warmth leading to increased
instability. Shear still on the weaker side so thinking it will
just be another day of pulsey thunderstorms for areas west of the
I-95 corridor. To the east where the bulk of the upper level
forcing looks to align will be more persistent showers with
embedded thunderstorms.

Monday night ridging from the west begins to build in as high
pressure returns at the surface. The precip will begin to taper
off from west to east with the building subsidence.

Many areas will see dry weather on Tuesday, though showers will be
possible central Virginia into southern Maryland depending on how
far north the remnants of Bonnie push. 12Z guidance is keeping
these remnants to the south on the Carolina coast through midweek
so not anticipating the precip to push much further north/west.


Low pressure over the North Carolina coast will slowly move
north- northeast along the Mid-Atlantic coast Wednesday into
Thursday. Moisture advection will allow for showers and
thunderstorms for both days... but it will mainly depend on
location of the low pressure system.

Slow moving cold front will approach from the west late on Thursday
into early Friday... and move across our CWA later on Friday. Front
will stall through Saturday to our east as upper trough over
the Great Lakes pushes east. These systems will allow for a
continued pattern of showers and thunderstorms through the end of
this period.

High temperatures will be in the upper 70s and low to mid 80s... and
low temperatures in the 50s and 60s.


VFR conditions initially today with increasing clouds. As the
rain moves in late this afternoon, should see diminishing cigs and
vis. Holding at MVFR for now during the periods of heaviest rain,
mainly evening/overnight, but cannot rule out periods of IFR
tonight. Isolated thunderstorms possible during the evening hours.
Winds 10 knots or less. Conditions improve back to VFR on Monday.

VFR conditions expected for Wednesday through Friday, with some
showers and thunderstorms possible, bringing periods of sub-VFR


Generally winds expected to remain below SCA values today through
Tuesday. Rain will overspread the waters this afternoon, heavy at
times tonight and Monday. With the rain comes the potential for
gusts up to between 20-25 knots.

Sub-SCA conditions expected as winds will be below SCA criteria.
Showers and thunderstorms possible over the waters during this




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