Scientific Forecaster Discussion
fxus61 kakq 211111
Area forecast discussion
National Weather Service Wakefield Virginia
711 am EDT Mon Oct 21 2019
weak high pressure builds into the area through this evening.
A strong cold front will cross the region Tuesday. High
pressure returns for the midweek period.
Near term /through tonight/...
as of 345 am EDT Monday...
Latest sfc analysis shows ~1006 mb low pressure centered
offshore of the Delmarva coast. In its wake, overcast
skies/gusty north winds continue to prevail across the area. Cirrocumulus/z
radar product showing some very light rain/drizzle prevailing
along the Lower Bay/Tidewater this morning.
Weak sfc high pressure over the Piedmont will slowly build east
into the area today. However, low and mid levels remain moist.
And given light north winds, no real mechanism in place to quickly
dislodge clouds quickly this morning. Will likely see some
breaks in the overcast and perhaps some opaque sunshine across
the Piedmont by afternoon. Otherwise, grids will average out
mostly cloudy for most...partly cloudy well inland. Highs today
mid- upr 60s.
Clouds may briefly start to thin this evening, but will increase
all over again overnight ahead of next system currently over the
Ohio/Tennessee River valleys this morning. Remaining dry early, but some
weak overrunning will start to push toward the area late
tonight. We will have a chance of showers return to the forecast
over the western third of the area late tonight, after 06z/2a
EDT Tuesday. Increasing clouds and a bit milder with lows in the
50s to near 60.
Short term /Tuesday through Thursday/...
as of 345 am EDT Monday...
Another active weather day expected on Tuesday. Deepening low
pressure will pivot across the Great Lakes region early Tuesday,
becoming occluded as it moves into into ern Canada Tuesday aftn.
The attendant sfc cold front will be approaching the area to
begin the day on Tuesday, and will cross the local area late
Tue into Tue night. Ample Gulf moisture is progged to stream NE
toward the region ahead of the front, and indeed pops are in
likely to categorical range (60-80%) over the western half of
the area or showers/occasional rain through much of Tuesday
morning/aftn W/an additional quarter to half-inch of rainfall
expected. However, the main complicating factor is with several
weak perturbations out ahead of the front, which could lead to
another sfc low forming along the approaching boundary over the
Cams each handle approaching front...and the pre-frontal wave...
a little bit differently, but all can agree that Theta-E ridge
will lift SW to NE glancing the southeast coastal plain late Tuesday
afternoon, then slipping offshore Tuesday night. This feature
will provide a quick influx of moist llvl air (td climbs into
the upper 60s to ~70 ahead of the front along the southeast coast
Tuesday aftn). Given the resultant marginal sfc instability and
favorable forcing for ascent, potential does exist for a short-
lived round of strong to severe storms across the far southeast corner
of the local area (mainly NE NC and possibly into the eastern
Tidewater area) after 18z/2pm on Tuesday into early Tuesday
evening. The Storm Prediction Center has now placed this area in a day 2 slight
risk, and this will need monitoring over the next day or so.
Farther inland, forecast soundings look quite stable, with
lifted indices remaining neutral to positive through the day and
clouds/showers ongoing through Tue aftn. While a rumble or two
of thunder cannot be totally discounted across central
Virginia/Northern Neck/ern shore, will keep thunder confined to the southeast
corner of the local area at this time and will maintain mention
in severe weather potential statement.
Behind the front, rain clears out from west to east late. Lows
low 40s NW...mid 40s to mid 50s elsewhere.
Cooler and drier for Wed/Thu, as cool high pressure builds
in from the west-SW Post-frontal and becomes centered over the
local area on Thu. Highs in the mid 60s to around 70 on
Wednesday, and in the upper 60s to low 70s on Thursday. Chilly
early morning lows in the upper 30s to mid 40s Wed night.
Long term /Thursday night through Sunday/...
as of 345 PM EDT Sunday...
Sfc high slides offshore Thursday night. Model solutions then
diverge with respect to the evolution of the trough from Friday
through next weekend. The European model (ecmwf)/Gem are forecasting an upper low
to form near the base of the trough in the srn plains and very
slowly move ewd through the weekend (with our area remaining dry
through most of sat). The GFS has a more progressive solution
(w/ rain moving into the area by late Fri before the trough axis
crosses the region Sat night). For now, went with a model blend
with no higher than chc pops for the Fri night-sun timeframe.
Will continue to monitor model trends during the next few days.
High temperatures will be in the upper 60s to low 70s on Thu/Fri
and lows mainly in the 40s inland with low 50s near the coast
(some upper 30s possible on Thu with the high near/over the
area). Slightly cooler next weekend W/ highs mainly in the 60s
(low 70s possible in far southeast Virginia/NE nc).
Aviation /11z Monday through Friday/...
as of 705 am EDT Monday...
IFR ceilings prevail across the area this morning, with some
lingering -ra/dz near the coast. -Ra/dz slowly tapering off over
the next few hours as low pressure offshore of the Delmarva
coast continues to pull farther offshore later this morning.
Still noting some patchy 4sm br west of ric terminal but visibility
restrictions should remain in the Piedmont and have held out of
taf for the time being.
Mostly cloudy conditions persist through the day today, with
ceilings improving to at least high-end MVFR by aftn (vfr possible
after 18z...especially at ric). Winds become light and veer to
the NE-east by evening.
scattered showers and isolated tstms are expected ahead of a
cold front Tue which may result in brief periods of sub-VFR
conditions. High pressure builds into the area for the midweek
as of 330 am EDT Monday...
Low pressure continues to lift NE off Delmarva early this morning
and will continue to drift further away from the region throughout
the day. High pressure will build in for Monday. Wind directions
this morning will be north/northwest and eventually become north/NE by later in the
day. Wind speeds continue to slowly decrease as the pressure
gradient relaxes however remain gusty this morning. Most locations
are now below gale criteria and will allow the warning to expire at
08z and will replace with a Small Craft Advisory. While wind gusts will diminish
below 20kts later this morning, elevated waves/seas will take much
longer to diminish. Small Craft Advisory for the Bay will go until 20z for 3-5ft
waves, by later this afternoon waves should diminish to 2-3ft. Small Craft Advisory
for the coastal waters will initially go until 06z Tuesday but may
have to be extended further if seas are stubborn to subside. Seas
this morning will be 5-9ft, 4-7ft late this evening, and 3-5 ft
Cold front crosses the area late Tuesday. Gusty northwest winds 10-20kts
are expected through Wednesday morning in the wake of the frontal
passage. Small Craft Advisory winds/seas are possible for a small window Wednesday
morning. High pressure then returns for Thursday and early
Marine...Small Craft Advisory until 4 PM EDT this afternoon for
Small Craft Advisory until 2 am EDT Tuesday for anz650-652-654-