Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
154 am EDT Thursday Jul 30 2015
high pressure remains offshore through Thursday morning...with
the next cold front crossing the area Thursday night. High
pressure builds back over the local area Friday into the weekend.
Near term /until 6 am this morning/...
another warm/mild night in store as dewpoints remain in the 70s
across the region. Temperatures late this evening still hovering in the
middle to upper 70s...with a few 80 degree readings near the coast and
urban areas. Stalled boundary remains over the northern middle-Atlantic
region this evening. Approaching cold front (located over the Ohio
valley) will produce pressure falls on the Lee side of the
Appalachians tonight...which could provide subtle low level
convergence in an already moist air mass (pwats ~2 inches). Will
maintain slight chance probability of precipitation over the northwest counties...but a lack of
appreciable forcing will keep much of the area dry. Sky averages
mostly clear to partly cloudy. Patchy fog possible again over the
northern Piedmont and northern Virginia. Otherwise...mild with lows in the middle
Short term /6 am this morning through Saturday/...
upper ridging retrogrades a bit 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 north-northwest areas during the afternoon...lowering to
10-20% across far southeast Virginia/coastal NE NC. Partly sunny with high temperatures
in the low 90s...except middle/upper 80s at the immediate coast.
Thursday night and Friday...
the cold front moves across the forecast area Thursday night before pushing
south into the eastern Carolinas on Friday. Have chance probability of precipitation
(30-50%) most areas with the passage of the front through early
Friday morning. Precipitation quickly pushes south/east by late Friday
morning...so that most places will be dry on Friday. Did maintain
20-30% probability of precipitation across southeast areas...however...even that threat is
primarily through the early afternoon before things dry out. This is a
change from previous forecasts as the front now looks like it
pushes farther south and quicker than previous model runs. Low
temperatures Thursday night in the upper 60s northwest to the middle 70s southeast. High temperatures Friday
in the upper 80s to low 90s.
Friday night and Saturday...
latest guidance now has the aforementioned front stalling farther
south along the Carolina coast heading into the weekend because
of a more pronounced upper trough over the Great Lakes and
northeast. Therefore...will go with a dry forecast Friday night
and Saturday. Lows Friday night in the 60s to low 70s. Highs Sat in
the upper 80s to low 90s.
Long term /Saturday night through Wednesday/...
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 night...then flatten
out sun with a weak shortwave pushing across the middle Atlantic by Monday.
Front stalls and dissipates over far southern Virginia/NC Sat night. 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 on sun/tapered to 20% far southern Virginia
and dry elsewhere). Will maintain 30-40% probability of precipitation NE NC for Monday due
to the shortwave moving through but not a lot of confidence as
this is 5 days out...probability of precipitation around 20% north. Keeping probability of precipitation around
20% all areas Tuesday. Typical summertime temperatures can be expected
with highs mainly ranging from the middle 80s/around 90 f along the
coast to the lower 90s inland. Lows generally ranging from the
middle 60s northwest to the lower 70s southeast through the period.
Aviation /06z Thursday through Monday/...
as of 06z...a mostly clear sky (sct to broken high clouds at or above 20kft)
prevails across taf terminals early this morning with weak high
pressure over the area. Southeast winds are forecast through middle morning
at 10 knots or less. There will be enough mixing to prevent
A cold front approaches from the west later today. Expect
increasing middle and high level clouds toward the end of the
period, especially north/west portions. There is a chance for thunderstorms late
this afternoon and this evening but with isolated-scattered areal coverage
expected ahead of the front, have kept mention out at this time.
Will re-evaluate with 12z tafs. Winds will be from the S/SW at
around 10 knots with a few higher gusts to around 15 to 18 knots
Outlook...a chance for thunderstorms continues tonight into early Friday, and
will end from north to south Friday morning. Mainly dry weather
is indicated through the weekend with a chance for thunderstorms mainly south
no headlines in the short term through Thursday...although as surface/Lee
trough over Virginia deepens slightly and helps S/southeast winds average near 15 knots
in the ches Bay there 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 later this eveng. Seas 2-3 feet.
A weak cold front approaches the waters late Thursday...then stalls
south-southeast of the area by late Friday. 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-northeast Friday morng into Friday afternoon...then turn to the east-southeast by late in
the day. Winds then turn back to the south-southwest for Friday night and Sat...as
the front dissipates south-southeast of the region. Waves 1-2 feet/seas 2-4 feet.