Area Forecast Discussion
Issued by NWS Wakefield, VA-- Remove Highlighting --
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FXUS61 KAKQ 261403
Area Forecast Discussion
National Weather Service Wakefield VA
1003 AM EDT MON SEP 26 2016
High pressure over New England will move off the coast early today.
A strong cold front will cross the region onTuesday. An upper level
low will track across the area later in the week.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --Sat loop / sfc obs show the BKN-OVC SC deck Btwn 3-5K ft advancing
eastward toward the coast late this morning. In addition, some
light echoes developing out across the piedmont well ahead of the
old frontal boundary now beginning to move back north as a warm
front. Thus, not much in the way of sun expected this afternoon
with isltd shwrs mainly west of I95. Becoming mstly cldy coastal
areas. Highs in the 70s.
Closer to home, will continue to see low clouds linger across the
piedmont as cool air wedge lingers inland, reinforced by onshore
flow out of the SE (veering to the S late). High-Res models in
relatively good agreement in taking some sct showers across the sw
third of the area (mainly west of I-95). QPF with these showers
would be low given minimal lift and PW still ~1-1.5 (highest along
and south of the VA/NC border per Blended TPW Satellite product
and supported by regional 00z soundings. As this happens, sfc high
pressure will slide east to the coast as the strong cold front
reaches the mtns by late in the day. Kept a slight chc in out west
in the aftn, but lift is minimal for the aftn, and thus areal
coverage of any showers would be quite low. Highs today in the mid
to upr 70s, warmest along the coastal plain just west of the Bay
where some more peeks of sun are expected.
-- End Changed Discussion --
.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/...
Models continue to slow frontal timing slightly, with frontal
passage looking to wait until after sunrise Tuesday. Will continue
to orient best pops along pre-frontal trough tonight.
Complex forecast for Tuesday, with models still struggling to
diagnose position of the mid/upper trough. Models can agree that
front will stall across the eastern half of the area on Operational
ECMWF has up until now been nudging the trough a bit farther south
than the GFS. However, latest 00z ECMWF has trended a bit farther
toward the GFS solution. At the sfc, front will slow/stall across
the coastal plain Late Tuesday, with showers likely focused along
the boundary as weak s/w energy slides along it Tuesday
afternoon and night. Good feed of moisture along and ahead of it
with PW`s climbing to around 1.75 inches. Instability is marginal,
but kept low chcs for thunder in place. Models show drier air
filtering across NWRN zones Tues afternoon to lower areal coverage
of pcpn there. Kept high chc pops across the SE into Wed night.
QPF btwn 1/2 to 1 inch inland...1.25 to 1.75" along the MD
counties and Northern Neck of VA.
Forecast for the mid week period becomes problematic, and a
conditional strong storm threat exists across the SE coast on
Wednesday. Uncertainty continues to revolve around
location/orientation of the Upper Low and resultant available
moisture. Blending the GEFS and WPC preferred UKMET solution,
thinking at this time is that front stands a good chance of
lingering along the SE coastal plain on Wednesday. Much
uncertainty attm, so will keep grids as general as possible.
However, Thunder wording has been added across the southeast,
with chc pops inland as upper low lingers just to the west. Highs
each day in the 70s (near 80 SE coast).
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Still some uncertainty in the extended due to the presence of
anomalous heights over the higher latitudes and an (possibly cut
off) upper-level closed low over the eastern CONUS. Latest consensus
digs the upper low over the central Appalachians Wednesday night and
Thursday. The upper low then meanders over the region Friday into
Saturday (possibly later) until an upstream deepening trough kicks
the low northeastward. At the surface, a frontal boundary remains
along the coast in southwesterly flow aloft. Height falls and energy
rounding the upper low will produce waves of low pressure along the
front. The end result will be unsettled weather conditions into the
weekend. Have increased cloud cover and POPs Thursday to mostly
cloudy and solid chance, respectively. Surface low pressure shifts
to the north Friday, with lower POPs and less cloud cover forecast.
Will retain slight chance to chance POPs due to uncertainty, but the
GFS/GEFS indicates less moisture. Confidence is increasing for a
dry/cool weekend, but it will depend on how the upper low is
absorbed into the approaching trough. Will keep mention of slight
chance across the northeast half of the forecast area Saturday, and
remaining dry Sunday.
Highs through the period will be below normal, generally in the low
to mid 70`s. Temperatures may struggle to get out of the 60`s inland
Thursday and Friday. Lows generally in the mid/upper 50`s to low
.AVIATION /14Z MONDAY THROUGH FRIDAY/...
High pressure over the Northeast States will move off the coast
early this morning, with low level flow becoming S-SE by late
morning/afternoon. A moist layer around 2-4K ft continues to
result in sct-bkn clouds this morning, mainly over inland
locations west of KRIC. As moisture increases through the period
ahead of a complex frontal system...expect that MVFR cigs over the
Piedmont will expand slowly east through the late afternoon and
evening on Monday. Some sct showers are possible across the
piedmont this morning, but will likely not impact terminals before
this afternoon, and have therefore held out of the TAF for the 06
OUTLOOK...The next chance for widespread precipitation arrives
late tonight into Tuesday ahead of a strong cold front. Periods
of IFR can be expected especially at RIC and SBY. Showers will
linger through much of the work week ahead as an upper level low
tracks across the region.
Surface ridge axis currently located over the waters this morning,
with generally east to southeast winds observed. Speeds are
generally at or below 10 knots. Waves 1-2 feet and seas 3-4 feet.
High pressure shifts offshore later this morning, with flow becoming
southeast 10-15 knots. A warm front lifts over the waters late today
ahead of a cold front approaching from the northwest. Gradient winds
ramp up, with models indicating favorable low level lapse rates to
produce low end SCA conditions in the Chesapeake Bay. South winds
increase to 15 to 20 knots tonight. Have raised SCA headlines for
the Bay and Rappahannock River. Strongest winds expected in the
upper Bay and Rappahannock River. Waves build to 2-3 feet and seas
up to 4 feet north of Parramore Island. The cold front crosses the
region late tonight, reaching the waters Tuesday. The front then
stalls just offshore Tuesday night. High pressure briefly builds
into the region Tuesday night as another area of low pressure drops
over the Great Lakes region. Perhaps a modest surge is possible
Tuesday night, but a lack of gradient winds and limited cold air
advection will generally produce sub-SCA conditions. Flow becomes
briefly onshore Wednesday and the southerly Wednesday night as low
pressure drops just west of the waters. Seas build to 3-4 feet
Wednesday. Low pressure remains over the waters through the end of
the work week, resulting in unsettled weather conditions.
MARINE...Small Craft Advisory from 6 PM this evening to 4 AM EDT
Tuesday for ANZ632-634-635.
Small Craft Advisory from 6 PM this evening to 7 AM EDT
Tuesday for ANZ630-631.