Area Forecast Discussion
Issued by NWS Wakefield, VA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS61 KAKQ 221429

Area Forecast Discussion
National Weather Service Wakefield VA
929 AM EST Sun Jan 22 2017

One area of low pressure will track from eastern North Carolina
northeast and off the Delmarva coast during today. A second
stronger area of low pressure over the Lower Mississippi Valley
will lift east northeast and across the Mid Atlantic region
tonight through Monday night. That low will move away just off
the New England coast during Tuesday.


Some quick developments over the past few hours have lead to
some necessary adjustments to the grids this morning. First off,
fog had reared its ugly head across the area once again as the
region remains wedged in a rather stable airmass. Locally dense
fog in some areas west of the Ches Bay, but not widespread enuf
for a dense fog advisory. Did issue an SPS though.

Expanded and extended the dense fog advisory across the lower
Ches Bay/James River and adjacent coastal waters through 18Z
based off current obs and web cams.

Second, with the fa wedged in, went ahead and dropped thunder
from the grids this afternoon and replaced it with stratiformed
rain as moisture from the second s/w overspreads the fa over the
next few hrs. Also increased pops to categorical most areas.
All the best support for tstrms this afternoon remains south of
the fa. Lowered max temps much like yesterday by a few degrees.
Highs in the 50s, possible reaching 60 across NE NC zones late.

With respect to tstrms (potential for severe) across the AKQ
fa, latest data suggests any threat will be with the more potent
low and warm front tonight (after 00Z) as it approaches the
area. SPC has adjusted its slght/mrgnl risk a bit. Went ahead
and addressed this in the HWO.


The second area of low pressure will then lift fm ESE TN east
northeast and acrs the Mid Atlc region tonight thru Mon night.
This low and its associated warm front will provide strong lift
and pull in deeper Atlc moisture, resulting in showers (slgt chc
of tstms srn third) with heavy downpours possible tonight into
Mon morning. Lows in the upper 40s to lower 50s. QPF averages
between 0.5 inch to 1 inch with locally higher amounts possible in
any banded convection that may occur.

Sfc triple point progged to move north of the area Mon morning
with the trailing upr level low crossing the region Mon aftn
into early Tue morning. Pops will still range fm slght chc to
likely fm later Mon morning into early Tue morning, as the upper
level low slowly moves NE acrs the area to just off the NJ
coast. Highs on Mon will range fm the mid 50s to the mid 60s.

The low moves away just off the New England coast during Tue.
NW winds usher in drier air with increasing sunshine fm SW to NE
expected. Highs in the 50s.


Overall, the models are in good agreement in the extended period
with only a few minor differences on the timing of the frontal
passage on Wed night into Thursday. But those differences are
minor and the 12z GFS has moved closer to the 00z ECMWF.

In the wake of the storm that will move through by Tuesday, a
shortwave ridge builds in Tues night into Wednesday. This will
allow for W to SW flow and should be a mild dry period. However,
the upper level pattern will begin to flip with a broad trough
developing over the eastern half of the country for the second
half of the week. This trough will enter the region Wed night
into Thursday as a sfc cold front slides into the area. This
front will be lacking moisture so have limited the pops to
slight chance to chance range. The best opportunity for rain
looks to be in the southeastern part of the area where a little
additional Atlantic moisture may be available. The timing on the
front is still a little up in the air. The ECMWF moves the
boundary through more quickly, while the GFS develops a wave and
is slower. But the trend has been toward the ECMWF timing so
focused the highest chance on Thursday. Will also need to watch
the timing on the cold air arrival as well as this could impact
the pcpn type, but for now don`t think the cold air will arrive
until after any pcpn is gone.

For Thursday night into Saturday, the region will be dominated
by strong NW flow which will drop temperatures back down into
the 40s for highs and lows in the upper 20s to low 30s. Have
kept the fcst dry too, but will have to monitor shortwaves
rotating through the upper trough as with this polar airmass, if
one of these waves amplifies a bit, some snow showers would not
be out of the realm of possibility.


A complex upper level trough is affecting much of the
Southeastern Conus and Mid-Atlantic early this morning. One wave
of low pressure is passing off the VA capes as of 06z with an
area of rain extending from central VA to the Ern Shore, with
some lingering showers across coastal SE VA/NE NC. IFR/LIFR
cigs prevail, although the lower cigs occasionally scatter and
reveal a 1.5-2.5kft layer, and this trend of lower cigs
occasionally scattering should continue the next 6-9 hours. Some
improvement in cigs is possible by aftn, but should fall again
tonight. Vsby drops to 1-3sm in heavier rain, with some fog
developing at ECG, which could expand to RIC/PHF after 09z.
Another wave of low pressure will bring occasional showers by
midday into early aftn, with the main frontal system lifting
across the region tonight into early Monday morning bringing
periods of moderate to heavy rain and reduced vsby. The wind
will generally be E to NE at 5-10kt today into this evening,
and is expected to increase to 10-15kt (locally 15-25kt at SBY)
late tonight into early Monday morning.

The upper system will lift across the area Monday aftn bringing
another chc of showers. Drier air gradually returns Monday
night into Tuesday as high pressure builds in from the NW. Low
pressure tracks through the Great Lakes Wednesday, and pulls a
cold front through the area later Wednesday night into early
Thursday. This will bring a chc of rain, before drier air
arrives from the NW later Thursday.


A complex low pressure system extends from the Gulf Coast States
across the Carolinas and into the Mid-Atlantic early this morning.
One individual wave of low pressure is pushing off the VA Capes
coast early this morning, with a stationary front extending back
into central NC. The wind is generally NNE 10-15kt N of the boundary
and SW 5-10kt S of the boundary. (Near) Coastal obs indicate vsby of
1sm or less S of Cape Henry, so the marine dense fog advisory has
been extended through 10 am for the ocean S of Cape Charles and the
Currituck Sound. Another wave of low pressure will track along the
front today, with the primary low tracking newd across the area late
tonight through midday Monday. A strong pressure gradient and modest
pressure falls develop late tonight through midday Monday and will
be strongest N of Cape Henry, and especially for the ocean N of
Parramore Island. The SCA N of Parramore Is. has been upgraded to a
gale warning for and E-NE wind of 25-35kt with gusts to around 40kt,
with the SCA to the S extending through Monday night as seas remain
aob 5ft. Seas build to 8-12ft N to 4-7ft S Monday in response to the
period of strongest wind. SCA flags have been issued for the
Bay/Lower James/York/Rappahannock. The wind will be strongest
in the Bay N of New Point Comfort, and low-end gale gusts are
possible N of Windmill Point. The low stalls in vicinity of the
NJ coast Monday aftn into Monday night as high pressure builds
in from the NW. The wind should by NW 10-15kt/15-20kt ocean.
High pressure gradually builds into the region Tuesday night and
slides offshore Wednesday ahead of a cold front. This cold
front crosses the coast later Wednesday night into early


Low pressure pushes off the Delmarva coast late Sunday night
through midday Monday resulting in a brief but modestly strong
onshore wind. This has the potential to push tidal anomalies to
1.5-2.5ft above normal Monday into Monday night. Some locations
including the Atlantic coast from Chincoteague to Ocean City and
portions of the middle and upper Bay may come within 0.5ft of
minor flooding thresholds during high tide, but the current
forecast generally keeps water levels below minor flooding.


MARINE...Small Craft Advisory from 4 AM to 10 AM EST Monday for ANZ635-
     Dense Fog Advisory until 1 PM EST this afternoon for
     Small Craft Advisory from 1 AM to 1 PM EST Monday for ANZ630-
     Small Craft Advisory from 1 AM to 10 AM EST Monday for ANZ632.
     Small Craft Advisory from 1 AM to 7 AM EST Monday for ANZ638.
     Small Craft Advisory from 1 AM Monday to 6 AM EST Tuesday for
     Gale Warning from 1 AM to 1 PM EST Monday for ANZ650-652.


TIDES/COASTAL FLOODING...akq is the U.S. government's official web portal to all federal, state and local government web resources and services.