Scientific Forecaster Discussion
fxus61 kakq 171147
Area forecast discussion
National Weather Service Wakefield Virginia
747 am EDT Thu Aug 17 2017
a weak frontal boundary remains over the mid Atlantic today as
high pressure builds over the northeast states. The next cold
front affects the area Friday into Saturday.
Near term /until 6 PM this evening/...
latest sfc analysis shows a weak stalled frontal bndry over the
area with high pressure over the northeast states. Expect some
patchy fog this morning especially over eastern areas, with
vsbys quickly improving later this morning. Deep layer moisture
increases today, and with the sfc bndry in the vicinity and weak
impulses aloft, there will be a chance of shras/tstms especially
inland with dry conditions expected near the coast. Otws, some
increasing cloudiness today with high temps in the upr 80s to
near 90 inland and mid 80s near the coast.
Short term /6 PM this evening through Saturday/...
frontal boundary remains in the vicinity tonight. Enough
moisture and support noted to keep slight chc-chc pops across
the area, with the best chance over nrn areas. Low temps in the
low to mid 70s.
Plenty of moisture around the region Friday with a sfc trof providing
the trigger for convection to develop. Not expecting a washout, but
do think the chc for pcpn will be around all day. More humid as
well with heat indices reaching at least 100 in many spots.
Widespread severe wx is not expected at this time, but gusty
winds and locally heavy downpours are possible. Highs upr 80s
to lwr 90s.
Frontal boundary slowly drifts se across the region Friday night and
Saturday keeping the chc for pcpn going. Drier air behind the front
will likely cut off any convection across nwrn most zones Sat. Lows
Fri night 70-75. Highs Sat 85-90.
Long term /Saturday night through Wednesday/...
cold front remains stalled near the mid Atlantic coast Sat
night into Sun morning before sagging well south of the area
by sun aftn. Any showers/storms invof the front will diminish
as the front moves farther south of the region. For the rest
of sun into Sun night, sfc high pressure builds north of the
area, and although temperatures should experience little to
no change, dewpoints will drop around 5 degrees thus feeling
a tad cooler. High pressure slides off the coast on Mon...
bringing a return to warm air advection and increasingly more
humid conditions. Sfc features rather diffuse during the
early part of next week, however seabreeze boundaries with
plenty of moisture present will keep a chance for
thunderstorms in the forecast during this time.
Highs generally mid-upper 80s to lower 90s; low-mid 80s
beaches. Lows Sat/sun nights generally upper 60s northwest to around
75f southeast. Lows Mon/Tue nights generally 70-75f.
Aviation /12z Thursday through Monday/...
patchy fog to start the 12z taf period. Any sub-VFR aviation
conditions will improve this morning as the fog dissipates
quickly after sunrise with VFR conditions returning to the
region. Early visible imagery suggests fog/IFR conditions will
be most persistent in the area straddling the I-95 corridor
including kric, and northeastward toward kxsa. Could linger as
long as 14z. Widely scattered showers and thunderstorms will
once again develop this afternoon, particularly across the
Piedmont. Generally light and variable winds are anticipated
this morning with winds becoming southerly and increasing to
5-10 knots this afternoon.
Outlook: a cold front approaches the region Friday into Saturday
bringing another chance for showers, thunderstorms, and sub-VFR
conditions. High pressure builds back into the region Sunday.
latest obs reflect light S-SW flow over the waters this morning. A
weak boundary stalled just north of the waters and extending back
into the Ohio Valley will lift farther north into the northeast
today, as low pressure crosses the upper Great Lakes today through
tonight. Pressure gradient begins to tighten today across the local
area as the associated (slow-moving) cold front tracks into the Ohio
Valley today, eventually crossing the mountains Fri before reaching
the waters late Fri night into Saturday morning. Winds speeds
increase to an average of 10-15kt this aftn...initially southeast and then
veering to S-SW late tonight/early Fri morning into Fri evening as
the front approaches. Hi-res models indicate some southerly
channeling late tonight through Friday, bringing winds to near Small Craft Advisory
thresholds late tonight thru Fri morning and again Fri aftn.
However, have held winds at 15kt for now with probabilities favoring
predominate sub-Small Craft Advisory winds. Some elevated winds possible with T-
storms Friday aftn and night. This surge of winds would be short-
lived and convective in nature and therefore likely better addressed
with targeted smw/mws. Seas average 2-3ft through this period, but
may touch 4ft out near 20nm as the front crosses the waters Fri
Winds become more west-SW Post-frontal with speeds aob 10kt early Sat
morning into Sun morning as the front stalls near the mid Atlantic
coast Sat night and early Sunday, and then become more onshore sun
aftn into Mon as the front sags farther south of the area.
Latest data indicating long second periods have largely abated with
distant Hurricane Gert accelerating farther NE away from the conus,
and well southeast of Atlantic Canada. One more day of elevated (moderate)
rip current risk over northern area beaches, with low rip risk
across southeast Virginia/NE NC Outer Banks. Given a mid to late morning low tide
cycle, rip risk should be lower for northern beaches for the
afternoon and evening.