Area Forecast Discussion
Issued by NWS Wakefield, VA

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FXUS61 KAKQ 190821

Area Forecast Discussion
National Weather Service Wakefield VA
321 AM EST Sun Nov 19 2017

A strong cold front moves across the area this morning then
pushes off the coast by midday. High pressure builds into the
area this afternoon through Monday, before sliding offshore
Monday night through midweek. The next cold front crosses the
area on Wednesday.


Front now just to the west of the local area this morning, with
pre-frontal showers now pushing across the piedmont toward the
I-95 corridor. With the moisture being pinched off from the
south, the expectation is that the rain showers will be
diminishing as they move through the area. Still, QPF looks to
be on track w/Western sections of the forecast area could see
up to a quarter inch of rainfall. By the time the front reaches
the coast, the expectation is of just scattered showers.

Hi-res models jiving very well with obs thus far, and a period
of rather gusty winds (30-40 mph) still anticipated over the
next few hours, with winds maxing out immediately behind the
frontal passage across the entire area, as some of the cold air
surge gets mixed down by strong subsidence behind the front.
Winds decrease slightly later this morning, but remain breezy
through the day, owing to still-tight pressure gradient and
mixing up to 875 mb. NW winds gusting to 25 to 35 mph (strongest
far north and MD eastern shore) through the afternoon before
they drop off.

Temperatures at 08z remain in the low to mid 60s (upper 50s far
west) across the local area. Temperatures do fall off quickly
behind the front over the piedmont, reaching the upper 40s/low
50s by sunrise.

Cold front and sct showers along the coast just after sunrise
will push offshore by mid-morning. Subsequent subsidence will
allow for quick scouring out of the vertical column, with mostly
sunny conditions most zones by late morning. Blustery with
gusty W-NW winds and only a slow rise in temps despite the
plentiful sunshine. Highs in the mid 50s- lwr 60s.

Sfc high settles over the sern states tonight through Monday,
sliding offshore Monday night into Tuesday. look for early
morning lows in the mid/upper 20s piedmont to mid 30s far SE
zones under a mainly clear sky.


Rather benign weather pattern to start the holiday week.
Aforementioned high pressure sliding offshore of the southeast
coast will maintain dry weather across the Mid-Atlantic and
southeast. Model thicknesses recover nicely and should allow for
a pair of pleasant late fall days. Highs Mon in the upr 40s to
low 50s eastern shore. low to mid 50s west of the bay. Partly to
mostly clear Mon night. Not quite as cool as flow turns around
to the W-SW, with some increasing mid to high clouds late. Early
morning lows in the 30s to near 40 se. Warmer in return flow on
Tuesday. Could see a few showers in association with a weak low
pressure sliding along the coastal Carolinas, but have kept the
daylight hours dry and held to slight/low end chance Tuesday
night for now. Highs Tue in the upr 50s to lwr 60s. Lows in the
40s to low 50s SE zones.


Model differences make for a challenging mid week and holiday
fcst. The next cold front progged to cross the area Tues nite.
Challenge comes from just how much moisture gets entrained ahead
of the front from a trof off the Carolina coast and weak low
progged to move ne along it? GFS much more aggressive with the
moisture than the ECMWF. For now, elected to keep measurable
rainfall east of I95 Tue nite and Wed with slight chc pops
across the east Thurs. Lows Tue nite in the 40s to near 50 se.
Highs Wed 55-60. Lows Wed nite in the 30s to lwr 40s se. Cool
Thurs with highs mid 40s-lwr 50s.

Dry and cool Fri and Sat as high pressure builds into the area.
Highs Fri 50-55. Lows mid 30s-lwr 40s. Highs Sat 55-60.


VFR conditions across area terminals early this morning with
lowering/thickening clouds out ahead of approaching cold front.
The front crosses the region through 12z this morning, and is
bringing some pre-frontal showers to the terminals during this
period. Overall, expect VFR conditions through this timeframe,
with some short-lived MVFR VSBYs possible in heavier showers.
Otherwise, main concerns will be the potential for gusty winds
and wind shear this morning. Models continue to show 35 to 50
knots at 2000 feet, thus continued the mention of wind shear
ahead of the cold front in the forecast. The front exits the
region by or shortly after sunrise on Sunday with winds becoming
W-NW post frontal. VFR conditions are expected through the day
today, but winds will remain gusty out of the W/NW with gusts
as high as 30 to 35 knots.

Outlook: High pressure builds over the region Sunday evening
through Monday, then tracks off the Southeast coast on Tuesday.
VFR conditions are expected during this time frame.


Late this aftn, sfc high pressure was cntrd off the Mid Atlc
coast, while sfc low pressure was cntrd over extrm wrn OH. A
cold front extended SW fm the low thru srn IN and down into the
lower MS valley. SSW winds were 10-20 kt with gusts into the
upper 20s (kt) late this aftn over the waters. The pressure
gradient between the high offshore and the approaching cold
front will tighten this evening into early Sun morning,
resulting in SW winds increasing to 20-30 kt with gusts ranging
from 25-40 kt. The cold front will cross the waters generally
between 11Z-14Z Sun morning, with winds then shifting to the NW
behind the front. On the late this aftn fcst, have decided to go
ahead and hoist the Gale warning (one headline) for the entire
coastal waters, due to gale conditions (gusts) expected within
the next 12 hrs. Also, for now, have kept SCA`s in effect for
all the other waters, even though there could be isolated gusts
to 35 kt at the mouth of the Ches Bay or the Currituck Snd.

Decent cold air advection, a persistent tight pressure gradient,
and rapid pressure rises (5-9mb) behind the front will all
contribute to a continuation of strong NW winds 20-30 kt with
gusts of 25-40 kt through Sun. Breezy to windy conditions will
prevail over much of the area on Sun, and generally uniform
with slightly stronger winds occurring over the warmer waters.
Winds should remain generally unchanged Sun night with NW winds
averaging 15-25 kt with gusts averaging 30 kt. Will still have
to monitor for possible gale gusts at the mouth of the Ches Bay
or the Currituck Snd during Sun. A secondary surge in NW winds
may be possible Sun night, as the coldest part of the airmass
swings across the area. However, relaxing pressure gradient with
high pressure building over the Gulf coast States into the TN
valley will likely prevent a very strong surge from happening.
High pressure continues to build over the Southeast States into
the srn Mid Atlc region Mon/Mon night, then sliding out to sea
on Tue. Calmer sub-SCA conditions anticipated Mon aftn into Wed.


The fan on the temperature sensor at the Richmond ASOS (KRIC)
has likely failed, causing erroneous temperature readings. The
contract observer is augmenting the official METAR observations
(Hourly METAR and SPECIs). However, the 5-min high resolution
data is automated directly from the sensor and is subject to
reporting this erroneous data. As such, do not rely on the 5 min
temperature data from KRIC until our techs can repair the
sensor, likely on Monday.


MARINE...Small Craft Advisory until 7 AM EST Monday for ANZ633-635>638.
     Gale Warning until 3 PM EST this afternoon for ANZ634-656-658.
     Small Craft Advisory until 10 AM EST Monday for ANZ630>632.
     Gale Warning until 4 AM EST Monday for ANZ650-652-654.


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