Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Wakefield Virginia
710 PM EDT sun Apr 22 2018
high pressure remains centered just off the mid Atlantic coast
through tonight. Low pressure will track from the Gulf Coast
states northeast up along the East Coast late Monday through
Near term /until 6 am Monday morning/...
as of 359 PM EDT Sunday...
Latest sfc analysis shows ~1030 mb high pressure centered just
offshore, and extending back northwest into the Great Lakes region. To
the north, a weak upper trough is sliding across the northeast
and northern mid-Atlantic. Farther west, a potent upper
level/closed low continues to slide slowly east across the
Southern Plains toward the lower Mississippi River valley, with
an inverted surface trough developing over the west-central Gulf
Coast region. Afternoon msas data continues to show pressure
falls over the deep south, in the vicinity of developing sfc low
pressure in east Louisiana into MS. It is this feature that will
slowly lift our way tonight through Monday, bringing steadily
increasing rain chances Monday evening through midweek.
Mid to high clouds have increased as expected, and will continue
to do so through late afternoon, especially inland. Clouds
briefly thin a bit with passage of upper trough and with loss
of heating early this evening. However, expect clouds to thicken
and lower all over again after midnight as the upper low nudges
closer into the mid-south.
Local area remains under the influence of sfc high pressure
positioned just off the coast. Another dry night with any pcpn
staying well west-SW of the local area. Expect a partly to mostly
clear night north, partly cloudy south with low temps ranging
through the 40s.
Short term /6 am Monday morning through Wednesday/...
as of 315 PM EDT Sunday...
Short term period characterized by gradually deteriorating
conditions Monday and Monday night, as aforementioned southern
stream low lifts out of the southeast through Monday night,
with the attendant sfc low sliding east-NE along the southeast
coast Monday afternoon through Tuesday, reaching a position
along the Carolina coast Tue night. This keeps the local area on
the cooler side of the system with a general light to moderate
rain expected to overspread the area.
Most of Monday will be dry across the local area, with the
exception of some low chc pops SW (for isolated to widely sct
showers after 18z) of the I-85 corridor. Otw, becoming cloudy
with highs in the 60s except for upr 50s at the beaches. Rain
overspreads the fa Mon night except for the lwr MD ern shore
where it may take until 12z Tue morning to reach. Pops ramp up
to categorical south of i64 Monday night/Tuesday morning, with
high end chc to likely pops to the north. Lows Mon night mid 40s
NW to mid 50s se. Tue looks breezy and wet, courtesy of strong
(albeit slightly weakening) onshore flow and upper forcing.
Still appears enough lift/moisture for periods of moderate to
heavy rainfall. Event total qpf ~1.5-2" inland, tapering to ~1
far NE sections. Highs Tue upr 50s NW to mid 60s se.
Drier, albeit with lingering clouds for Wednesday. Slightly
warmer with some peeks of sun likely. Still enough remnant low
to mid level moisture for a few showers, so will maintain chc
shower wording. Highs in the mid 60s to low 70s, with a few
mid 70s possible across the southern tier.
Long term /Wednesday night through Sunday/...
as of 355 PM EDT Sunday...
A fast moving shortwave is forecast to track from Georgia to ern
North Carolina Thursday-Friday am. 22/12z GFS has 999mb sfc
low pressure centered over southeast Virginia at 12z Friday with around 1 inch of
quantitative precipitation forecast over much of the County Warning Area. The most recent 12z European model (ecmwf) has a much weaker
low pressure system centered around 150 miles to the southeast
with less than a quarter inch of quantitative precipitation forecast confined to southeast Virginia/NE NC.
Kept pops between 25-35% with the highest values in the
southeastern County Warning Area given the differences between the guidance.
Highs in the upper 60s on the ern shore/low 70s elsewhere Thu-Fri.
A more potent mid-level shortwave is still forecast to track over
the northeastern US Friday into the weekend. This will set the stage
for another chance of rain late Friday-Saturday as a cold front
passes through the region. Once again, there are differences between
the guidance regarding the strength and timing of the storm system.
Therefore, have carried slight chc/chance pops from Friday
through 00z Saturday. Highs in the mid-upper 60s Saturday
warming to around 70 on Sunday. Lows in the mid 40s to around 50
Aviation /00z Monday through Friday/...
as of 7 PM EDT Sunday...
VFR through the forecast period with bkn to ovc high and mid
level cloudiness ahead of the system apprchg from the SW. Se
winds aob 10 kts. Cloud deck will eventually lower late Monday
afternoon and evening as the rain arrives from the SW.
expect conditions to deteriorate from SW to NE Monday night as a
large area of rain approaches the County Warning Area. This will result in flight
restrictions throughout the day Tuesday at all terminals.
Restrictions will likely last through ~12z Wed before conditions
slowly improve during the day.
East winds increase to between 15-20 kt (gusts to ~25 kt) at
orf/phf/sby/ecg during Tue and last through 00z Wed. Slightly
lower winds (e at 10-15 kt) expected at ric during this
timeframe. Winds decrease after 00z Wed and turn to the SW by
as of 315 PM EDT Sunday...
High pressure centered over New England will prevail across the
region through tonight, allowing for a southeast wind of 5-15. Waves/seas 1-
2 ft. High pressure pushes off the srn New England coast Monday and
Tuesday as low pressure lifts from the deep south into the Tennessee
Valley. This will result in increasing onshore flow. An east wind is
expected to reach 10-15kt by Monday, and then 15-25kt by
Tuesday/Tuesday night. Onshore flow will result in seas building to
5-9ft, with 4-5ft waves in the mouth of the Bay (2-4ft elsewhere in
the bay). Scas will eventually be needed for this time frame. Broad
low pressure lifts north of the region during Wednesday with south-southwest
winds 5-15kt becoming northwest in the wake of the low Wed night into thurs
morning. The next low pressure system then impacts the region