Area Forecast Discussion
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FXUS61 KAKQ 200621
Area Forecast Discussion
National Weather Service Wakefield VA
121 AM EST Fri Jan 20 2017
High pressure moves off the coast tonight. Low pressure tracks
across the Midwest and into the Great Lakes region Friday. The
associated warm front lifts north across the area Friday night.
A complex area of low pressure will affect the region early next
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Sfc hi pres sits near the immediate coast late this evening.
SCT-BKN mainly high clouds continue to spread E and over the FA
as lo pres tracks into the TN/OH valleys. Gradual increase in
clouds expected overnight. Based on trends and near term
guidance...will hold off on PoPs above 14% through 12Z/20. Lows
in the l30s on the (Lower MD eastern shore) to around 40F far S.
.SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY/...
A wet day ahead Fri as a decent slug of overrunning moisture
overspreads the entire FA during the morning hours ahead of the
advancing warm front. Best lift progged across northern most
zones for categorical pops, likely pops elsewhere. Best support
for pcpn quickly exits to to the E-NE after 21Z so will show
pops ramping down late across the west. QPF below one quarter
inch. Highs in the 50s except near 60 ivof Albemarle sound.
Any steady/lingering rain exits off the coast before midnight.
Otw, tsctns show plenty of low level moisture across the fa
Friday night. Given a nearly saturated airmass, added patchy
fog/drizzle to the grids. Lows 40 to 45.
Saturday starts out with fog/drizzle then remains cloudy.
Moisture from the approaching southern system progged a bit
slower to move north so have trimmed back pops a bit until after
20Z across the swrn most zones. Rather mild despite the cloud
coverage. Highs 55-60 near the water, 60-65 west of the bay.
Models begin to diverge with the approaching system from the south
Saturday night and especially Sunday. Initial low tracks NE along
spine of mts while a secondary low pressure develops on a advancing
frontal boundary from the south. Model differences lead to a low
confidence temp forecast but high confidence pop forecast. Yes it
will rain, but will it be a stratiformed event like the GFS/ECMWF
suggests as low pressure moves off the coast resulting in a insitu
wedge scenario or more of a convective event like the NAM suggests
as it has the warm front lifting north with abundant lift/moisture.
Not getting fancy at this time, will slowly increase pops from chc
to likely across the fa Saturday night with lows in the mid 40s to
lwr 50s. Categorical pops (for shwrs) Sunday but limit any thunder
chcs to southern most zones closer to where the boundary may end up
being. Given the progged lift, theta-e advection/increasing PW`s,
went ahead and indicated moderate pcpn rates in the grids. Locally
heavy downpours will also be possible. Highs mid-upr 50s north to
low to mid 60s south.
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Upper level energy currently over the Gulf of Alaska is forecast to
lift into the Mid-Atlantic region Sunday night. There are still some
spatial and timing differences in handling of the associated surface
low and frontal features in the 19/12Z guidance, but confidence is
high that widespread precipitation continues Sunday night. POPs have
been raised to categorical as upper level forcing and moisture are
plentiful. The surface low is progged to lift along the Mid-Atlantic
coast Monday as the upper low remains over the region. Best moisture
flux and theta-e advection progged to be offshore, but have included
a slight chance mention of thunder across the southeast local area
Monday. Have trimmed daytime highs back a few degrees into the mid
to upper 50`s. Upper/surface low pressure lifts northeastward away
from the region Monday night and Tuesday, with precipitation chances
winding down Tuesday afternoon. Upper/surface low pressure builds
into the region Tuesday, sliding offshore Tuesday night as the next
storm system approaches the region. Highs Tuesday generally in the
mid 50`s under a partly cloudy to mostly cloudy sky. A cold front
associated with an upper low lifting over the Great Lakes region
progged to push across the region Wednesday into Wednesday evening.
Moisture and forcing look rather meager at this point, so have kept
silent POPs. Warmer Wednesday, with highs in the upper 50`s north to
low 60`s south. Shortwave energy progged to push across the region
Thursday, but a lack of moisture and westerly flow will result in
ongoing silent POPs. Highs Thursday generally in the mid 50`s. Lows
during the period will generally be in the 40`s, with the next
chance for sub-freezing temperatures inland Thursday night.
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
As of 06z...High pressure over coastal portions of the Mid
Atlantic States will move off the coast early this morning. Low
pressure will over the Mid Mississippi Valley will move
northeast into Ohio. An upper level shortwave lifts northeast
through the Mid Atlantic States today. Included some low vsbys
that could last through mid morning for KECG where some fog has
already developed in the vicinity.
A broken layer of cirrus clouds over the area will increase
with lower clouds moving in later this morning. Precipitation
develops from the southwest this morning and spreads to the
coast in the afternoon. MVFR conditions are expected with the
precipitation. IFR ceilings are possible at RIC and SBY late in
the day. Winds will be light through the period.
OUTLOOK...IFR conditions are indicated for most of the area
tonight into Saturday morning with fog and drizzle possible.
Abundant low level moisture and weak surface flow will promote
reduced aviation conditions through much of the day Saturday.
Ceilings and visbilities will deteriorate again Saturday night
and Sunday morning with IFR possible at each of the TAF sites.
Periods of widespread rain are expected Sunday through Monday as
a strong low pressure system moves from the southern Great
Plains and across Virginia Monday to off the New jersey coast
Tuesday. This will result in unfavorable conditions for
aviators. The weather improves by Tuesday.
Latest surface analysis centers ~1017mb high pressure over the
Delmarva as low pressure deepens well offshore. Obs indicate light
northeast to east winds over the waters, generally at or below 10
knots. Long period swell associated with the offshore system has
resulted in seas of 3-4 feet. High pressure remains along the coast
overnight with winds remaining at or below 10 knots. A few 5 footers
are possible around 20nm out overnight. Sub-SCA conditions persist
through Saturday night behind a warm front and high pressure
offshore. Onshore flow ahead of a strong area of low pressure
Sunday, will increase to 15-25 knots Sunday night through Monday. A
period of low end gales is possible, especially across the northern
coastal waters. Onshore flow will push seas to 5-6 feet late Sunday,
and upwards of 7-10 feet into Monday. Waves 3-5 feet (6 feet mouth
of the bay). Sub-SCA conditions return Tuesday (although seas will
likely be slow to subside) as the low lifts northeastward, away from