Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
415 PM EDT Friday Jul 25 2014
high pressure drifts off the middle Atlantic coast over the weekend.
A warm front lifts north across the area Saturday night and Sunday.
A strong cold front moves across the region early Tuesday.
Near term /until 6 am Saturday morning/...
surface high pressure moves over the area tonight with any convection
remaining south of forecast area. Mainly clear with lows in the 60s.
Short term /6 am Saturday morning through Monday/...
a weak short wave tracks across the area Sat aftrn/eve. Meanwhile...the
old frontal boundary begins to move back north as a warm front by Sat
night. Models continue to differ with respect to returning moisture across the
Piedmont. Model soundings show a strong middle-level cap across most
of the forecast area. Given possible convective complex moving east across northern
Virginia...decided to add isolated probability of precipitation to Northern Neck & lower Maryland Eastern Shore Sat
afternoon. Dry elsewhere. 850 mb temperatures rise a bit resulting in high temperatures
in the u80s-l90s west of the Bay...m80s along the coast. Warmer and
more humid Sat night. Lows u60s-l70s.
Next short wave drops southeast from the Upper Middle west sun. This begins to carve
out an anomalously deep longwave trough into early-middle next week.
Associated surface front apprchs from the northwest late Sunday with the
initial short wave prognosticated to pass to the north of forecast area. Thermal trough develops
with enough moisture/instability prognosticated to allow convection to develop across
the mts then drift east-southeast across the forecast area Sun afternoon/night ahead of apprchg
cold front. Storm Prediction Center dy3 outlook has Virginia/Maryland in a slght risk for damaging
winds/large hail due to potential convective complex later in the
day. Kept chance probability of precipitation in forecast for now with the highest chance across
northwestern most counties. Heat / humidity return with highs u80s along
the coast...90-95 west of Bay.
Kept chance probability of precipitation going Sun night as cold front apprchs. Lows 70-75.
Mondays forecast rather problematic as strong cold front comes through
early enough for morning convection with possible drying by late in the
day. Kept chance probability of precipitation here with highest chances across the south. Highs
u80s-l90s given downsloping west winds & some afternoon htng behind frontal passage.
Long term /Monday night through Friday/...
going with a combination of the 12z GFS and 12z European model (ecmwf) for the
extended period. Longwave trough digs into and over the middle Atlantic region
Monday night into early Thursday...before retrograding back into the Ohio and MS
valleys Thursday afternoon through Friday. Cold front will push off the CST Monday night
and Tuesday...lingers farther off the CST Tuesday night through Thursday...then
possibly drifts back toward the CST late Friday. Other than a slight or small
chance for showers over extreme southeast Virginia and NE NC Monday night into Tuesday
morng...will have a dry forecast for the remainder of the extended
period. A more comfortable airmass will dominate the area Tuesday into
Thursday...before a little more humidity returns on Friday. Maximum temperatures will
generally be in the lower to middle 80s through the period. Min temperatures will
range from the lower 60s to lower 70s Tuesday morng...range from the upper 50s to
middle 60s Wednesday and Thursday morngs...and range through the 60s Friday morng.
Aviation /20z Friday through Wednesday/...
a stalling surface cold front along the NC coast will gradually wash
out/dissipate today. VFR conditions and light winds at or below 10 knots
will prevail through most of today as surface high pressure builds
just north of the area. Wind directions will be north-NE
today...turning east-southeast tonight through Saturday. Isolated showers
and thunderstorms may develop Saturday afternoon as a weak surface
trough and middle level wave pass through the mid-Atlantic.
S-SW winds gusting to 15kt expected Sunday as a cold front
approaches the region from the west. The front is expected to
cross the region on Monday.
Note: observations from ksby are not readily available due to a
communications problem. Return to service is unknown at this time.
However...current information may be obtained by calling into the
ASOS site directly. Amend not schedule will be appended to the ksby taf
until further notice.
no headlines in the short term tonight through sun. Hi pressure over the area
late this afternoon...will slide off the CST tonight. North through east winds 5 to
10 knots...will shift to the southeast or S tonight. S winds will increase to
10 to 15 knots Sat night...then become SW 10 to 15 knots for sun into Sun
night in advance of approaching cold front. Cold front will push
through the waters during Monday...then moves off the CST Monday night. Winds
will turn to the west-northwest behind the front at or below 15 knots into Tuesday.