Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
407 PM EDT Tuesday Jul 28 2015
high pressure remains offshore through midweek...with the next
cold front crossing the area by Thursday night.
Near term /until 6 am Wednesday morning/...
slow moving (mainly pulse type) thunderstorms ongoing this afternoon from the
eastern Piedmont to the Northern Neck. Have seen isolated cells pop
across southeast Virginia/NE NC and the Eastern Shore but these have not be
able to sustain themselves. Severe threat remains low through the
evening given weak effective shear (<25kt). Main threat from these
storms will be locally heavy rain due to slow storm
motion/training of cells over the same areas. Dual-pol radar
already showing a few locations in Dinwiddie/southern Chesterfield
County with up to 3-4" of rain this afternoon with spotter reports
backing this up. Will maintain highest probability of precipitation 40-70% across the
western 2/3rds of the forecast area through the evening...with 20-30% probability of precipitation at
the coast...and this activity will gradually dissipate after
sunset. Otw...partly to mostly cloudy overnight. Lows in the mainly
in the 70s.
Short term /6 am Wednesday morning through Friday/...
upper level ridging continues to expand eastward from the
Southern Plains. This will help to limit afternoon convection while maximum
temperatures warm a couple of degrees. Have chance probability of precipitation (25-30%) along and
west of I-95. Partly sunny west/ high temperatures in the upper 80s to low
90s...with low/middle 80s at the beaches. Mild Wednesday night west/ low temperatures
in the low/middle 70s.
upper ridging retrogrades a bit Thursday as a trough moves across
the Great Lakes and pushes a cold front into the middle-Atlantic
region by late in the day. Due to the late arrival of the
front...chance probability of precipitation (30-50%) will remain across western areas during
the afternoon...lowering to ~20% at the coast. Maximum temperatures will reach
into the upper 80s to low 90s...except low/middle 80s at the immediate
Thursday night and Friday...
the cold front moves across the forecast area Thursday night before stalling
across far southeast Virginia and the eastern Carolinas on Friday. Have solid
chance probability of precipitation (30-50%) most areas with the passage of the front
through midday Friday...then focus chance probability of precipitation across southeast Virginia and NE NC
Friday afternoon. Dry weather should return to northwest areas by late morning or
afternoon. Lows Thursday night in the 70s. Highs Friday in the 80s to
Long term /Friday night through Tuesday/...
pattern begins with a middle/upper level ridge centered
over the SW Continental U.S. And an upper level low persisting across Hudson Bay
Canada. GFS/European model (ecmwf) into better decent agreement that an upper trough
axis will extend south into the Great Lakes Sat...then flatten out
sun with a shortwave pushing across the middle Atlantic by Monday.
Front stalls and weakens over far southern Virginia/NC late Friday into the
weekend. Best chance for precipitation looks to be across the far south/mainly
NE NC through the weekend but even here will only go with a 20-30%
probability of precipitation/primarily for the afternoon/evening timeframe (tapered to 20% far
southern Virginia and dry elsewhere). Did raise probability of precipitation a bit for Monday due to the
shortwave moving through but not a lot of confidence as this is 5-6
days out so will generally keep probability of precipitation only at 30-40% south to 20% north.
Keeping probability of precipitation around 20% all areas Tuesday. Typical summertime
temperatures can be expected with highs mainly ranging from the
middle/upper 80s along the coast to the upper 80s to lower 90s inland.
Lows generally ranging from the middle 60s northwest to the lower 70s southeast through
Aviation /19z Tuesday through Sunday/...
VFR/MVFR conditions prevail across all terminals early this
afternoon. Areas of showers/thunderstorms have developed mainly from
kric/kofp southward and westward. Main concern with these storms
is heavy rainfall...with local IFR conditions likely.
Elsewhere...shwrs/tstms expected to be more isolated...and have
kept all terminals dry except kric...and korf...where neaby shower
should move across the terminal before 19z. Some fog will be
possible overnight where rain falls...with kric the only terminal
currently at risk of fog. Mainly VFR conds expected Wed/Thu... as
high pressure builds westward into the region. Isolated
showers/thunderstorms possible Wednesday afternoon/evening...but little in the way
of organization expected. Next chance for more numerous showers/thunderstorms
and associated lower ceilings/visibilities will be late Thursday into Friday when
a cold front pushes into and across the area.
Mainly VFR flying weather expected in the Sat-Monday extended period.
weak surface high pressure is centered off the coast with
weak surface troughing inland across the Piedmont and coastal plain. S/southeast
winds average 10-15 knots this evening/overnight...and will drop off to
S/SW 5-10 knots Wednesday morning. Models suggest that winds may be a little
stronger late Wednesday afternoon/Wednesday night as surface/Lee trough over Virginia deepens
slightly and helps S/southeast winds average around 15 knots in the Bay. Could be
a few hours Worth of 20 knots gusts in the Bay but too marginal to
consider any Small Craft Advisory headlines for now. Waves generally 1-2 feet in the
Bay but will probably build to 2-3 feet Wednesday evening. Seas 2-3 feet.
A weak cold front approaches the waters late Thursday...then stalls south
of the area by late in the week. S/southeast winds average 10-15 knots...turning
south-southwest Thursday night. Not a strong cool surge on Friday as winds shift to the
north with the front dissipating over southern Virginia/eastern NC so will keep
winds in the 10-15 knots range. Flow gradually shifts to east/southeast into the
weekend with waves 1-2 feet/seas 2-4 feet.