Area Forecast Discussion
Issued by NWS Wakefield, VA

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000
FXUS61 KAKQ 230630
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
130 AM EST Tue Jan 23 2018

.SYNOPSIS...
High pressure slides farther off the coast tonight. A trough
crosses the region Tuesday morning, with the cold front lagging
behind and pushing through the region by late afternoon, before
pushing well off the coast by Tuesday night. High pressure
becomes centered over the south central states Wednesday and
builds east into the local area by Thursday.

&&

.NEAR TERM /THROUGH TODAY/...
Latest analysis places a potent upper low over the Midwest, with
a double surface low ~998 and 999mb one beneath the upper system
over SE IA and the other near Lake Michigan. Meanwhile, sfc
high pressure is pushing well off the mid-Atlantic.
Temperatures this evening are mainly in the 50s for most of the
CWA with the exception the Ern Shore where temperatures are in
the mid 40s to around 50F. Fairly thick cirrus shield remains
in place for the most part, with some low and mid clouds
arriving from the SW. Very mild overnight with temperatures
staying in the 50s just about everywhere (mid/upper 40s coastal
eastern shore, but these values should rise overnight).
Becoming cloudy overnight with increasing rain chances after
06Z mainly over the Piedmont, and will overspread likely PoPs to
the I-95 corridor between 09-12Z. Enough mid level instability
will move in late to include mention of isolated tstms late west
of I-95, though at this point these will be elevated.

High rain chances (60-90%) prevail Tue morning as main sfc low
pressure becomes occluded over Michigan and significant pressure
falls and a meso-low develop along the central Appalachians by
around 12Z. The strength of this feature will likely have a
significant affect on QPF and the potential for some embedded
convection in the morning in a high shear/minimal CAPE
environment. Latest GFS/NAM SHERB values are from +1 to +1.5
between 12-18Z, though this parameter does have some limitations
and the synoptic pattern (sfc low into Great Lakes), does not
typically favor a lot of tstms/severe threat for the AKQ CWA.
However, with significant shear and some instability aloft
(H7-H5 lapse rates of 6.5C/km) can`t rule out isolated strong
tstms mainly from 12-15Z west of i-95 and 15-18Z farther east.
SPC has most of the CWA in a marginal risk for severe, and if a
distinct line or some discrete cells do develop Tue morning,
they will need to be monitored closely. The current pattern
with convection across the deep south and Gulf of Mexico could
be a hint that a split in the precip shield is likely (and thus
most areas should expect only around 0.25" or less of total QPF
except for locally higher amounts in tstms and over the far N).
Models remain in good general agreement wrt timing and should
see PoPs taper off W-E quickly by aftn...w/ pcpn moving out of
the entire area by 21Z/Tue to 00Z/Wed. With partial aftn
sunshine, deep mixing, and a downslope flow highs Tue will be
breezy and unseasonably warm, possibly close to record highs.
Current forecast is for highs 70-75 F across much of central/SE
VA and NE NC, with 65-70 F on the eastern shore and over the
W/NW sections of the CWA.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
Dry cooler tonight/Wed w/ lows mainly in the 30s (around 40 F
SE). Mostly sunny with highs Wed u40s on the ern shore to 50-55
F elsewhere. Partly cloudy as an upper trough swings through Wed
night with lows in the u20s-l30s. Mostly sunny and seasonable
Thu w/ highs from the l40s NE to around 50 F south central VA.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Overall pattern continues to show the long term period beginning
with a shortwave ridge building eastward from the Mississippi
Valley into the Southeastern US and Mid-Atlantic states on
Friday into Saturday. This is followed by a full latitude trough
that moves in on Sunday into Monday. But today, the timing
between the models and strength of the cold front crossing the
area is different with the 12z GFS slower and weaker while the
12z ECMWF is slower, stronger and would provide more rain for
the region. The ECMWF right now has better run to run continuity
than the GFS as the 6z GFS was slower and wetter than the 12z
run. So for now have leaned a little more toward the slower
ECMWF for that part of the forecast.

On Thursday night through Friday, high pressure will be in
control of the regions weather with the high overhead expect to
see a very cool night with good radiational cooling, lows in the
m20s-l30s. Temperatures will begin to warm again on Friday as
warm advection begins with sw flow, expect highs in the u40s to
u50s. Mex guidance is a bit warmer and began to trend that
direction raising highs a few degrees above the other guidance.
The SW flow continues on Fri night with more dry weather and
maybe a few more clouds. Temperatures in the mid to upper 30s
are expected.

For Saturday through Sunday night, this is where the most
interesting portion of the extended lies as the quicker GFS has
the moisture and front approaching the area by late Sat
afternoon, which is about 6 to 12 hours faster than the 6z GFS
or ECMWF. At this range, did raise pops a touch, but kept the
forecast dry on Sat with temperatures getting back into the U50s
to l60s. But beginning Sat night did start to raise pops up to
high chance values. Some guidance suggest pops in the likely
range are possible now, but with timing issues and also the
questionable forcing have capped pops at 50% from Late Sat night
through Sunday with a slow clearing of the pops in Sunday
evening. Sunday looks like the most probably period for rain and
the ECMWF would indicate a beneficial rain, which would be good
for the drought areas, but at this range models have been
showing these types of events for the last few weeks, but the
plentiful rain has been materializing. Have kept temps mild on
Sat night and Sunday with lows in the 40s and highs still in the
60s.

The front should clear the area Sunday night with NW and high
pressure building in on Monday. The strength of the developing
upper trough will determine how strong the low over New England
gets Sunday night and this will impact temps on Monday. The
ECMWF would suggest temperatures cooler than the currently
forecast in the upper 40s to mid 50s on Monday. But for now will
not bit completely on the ECMWF.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
Lowering CIGS (to IFR/low end MVFR) through the early morning
period as moisture continues to increase on deep layered S
winds. A cold front is approaching from the W attm...and will
push across the FA this morning...then off the coast this
afternoon/eve. The front will be accompanied by SHRAs. Instability
with the front will also bring a lo prob for ISOLD tstms through
midday/early afternoon. Clearing/improving conditions expected
during the afternoon/eve. Sfc hi pres builds into the local area
from the SW through Thu.

&&

.MARINE...
High pressure over the waters is shifting east and offshore this
evening as low pressure moves into the Great lakes. A
tightening pres gradient ahead of the approaching cold front
tonight will increase winds to 15 to 25 kt from the S-SW prior
to daybreak Tues. These winds will persist thru midday/early
aftn Tue becoming rather gusty by mid morning. Seas on the
coastal waters building to 4-6 FT; waves 3-4 ft on the Bay
rather quickly in response to the SW winds. SCAs remain in
effect for all waters overnight into Tuesday. With the primary
surface low so far displaced to the north it will be hard to get
Gales with warm S-SW winds over cold water this time of year,
but did keep mention of a few gusts to 30 to 35 kt for our
northern coastal waters.

Once the front clears the area Tues afternoon, winds will shift
to the west 15 kt Tues night/Wed and then northwest on Thursday.
Waves/seas subside to 2-3 ft. There is another surge of cold
air Wed night into early Thu which will maintain the NW winds
of 15 kt with some higher gusts. Waves and seas may increase by
a foot to 2 to 4 ft with this surge Thu. Conditions improve by
Friday as weak high pressure builds into the area.

&&

.CLIMATE...
Record high temperatures today.

     Tuesday
RIC  76/1974
ORF  76/1999
SBY  73/1999
ECG  76/1937

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory until 6 PM EST this evening for
     ANZ630>632-634>638.
     Small Craft Advisory from 6 AM this morning to 6 PM EST this
     evening for ANZ633.
     Small Craft Advisory until midnight EST tonight for ANZ650-652-
     654.
     Small Craft Advisory from 6 AM this morning to 10 PM EST this
     evening for ANZ656-658.

&&

$$
SYNOPSIS...AJZ/LKB
NEAR TERM...AJZ/LKB
SHORT TERM...ALB/LKB
LONG TERM...ESS
AVIATION...ALB
MARINE...JDM
CLIMATE...


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