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-- Discussion containing changed information from previous version are highlighted. --
954
FXUS61 KAKQ 231819
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
219 PM EDT Tue May 23 2017

.SYNOPSIS...
A frontal boundary draped across northeast North Carolina this
morning will lift back north into southeast Virginia this
afternoon, as a potent low pressure system tracks along the
boundary through this evening. Unsettled conditions continue
Wednesday and Thursday as an upper level trough approaches from
the west.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A frontal boundary is just south and east of the local area this
morning with high pressure situated over the OH Valley. As of
1000 am, light rain is moving across central/ern VA, with
moderate to heavy rain across NE NC. The frontal boundary to
our south will gradually creep back northward into SE VA this
afternoon and will be the focusing mechanism for our well-
advertised rain event through tonight. A series of low pressure
systems will ride NE along this boundary today allowing for
multiple bouts of rain, some of which may be heavy at times. The
most potent of these sfc lows is expected to move across SE
portions of the FA late this aftn and evening, and should
provide our best chance of locally heavy rain. With deep layer
moisture returning, categorical PoPs overspread most of the
area through this afternoon, but may wait until late aftn and
the evening for the MD Ern Shore. 23/00z suite of models
(NAM/GFS/GEFS/ECMWF) still all over the place with timing and
placement of heaviest QPF today and exact track of the strongest
low late today into tonight. As mentioned above, the general
consensus is for this low to track across southeast portions of
the VA late today into tonight and so that is when/where we`ll
show our highest QPF amounts. The threat for heavy rain and
possible minor flooding will continue to be mentioned in the
HWO, but have opted against a flood watch at this time as 6hr
FFG is generally 4-6" across much of the area, with some values
of 3-4" across the Piedmont and MD Ern Shore. QPF through 06z
Wednesday averages 0.5-1" north to 1-3" south, and higher
amounts are possible. Highs today will range from the mid/upper
60s across much of the area to the low 70s along the Albemarle
Sound.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
The potent shortwave/surface low pushes offshore Tuesday
evening with a secondary wave moving offshore around/after 06z.
Will carry likely/categorical PoPs (55-85%) in the evening, then
tapering off overnight into Wed morning. Lows Tues night in the
mid 50s west to mid 60s SE coast.

Yet another wave approaches from the SW Wednesday aftn as an
upper low approaches from the W. This wave tracks across the
region Wednesday evening through the early overnight hours
bringing another round of likely PoPs along with a chc of
embedded thunderstorms. Current 00z guidance suggests the best
instability remains southeast. However, the potential for some
strong to severe storms will need to be monitored with 500mb
height falls and strengthening/veering flow at the 500mb level.
SPC currently has our SE counties in a marginal risk. Unsettled
conditions continue into Thursday with chc to likely PoPs
continuing along with a chc of thunder. Mostly cloudy to
overcast Tuesday night through Thursday. Highs Wednesday/Thursday
ranging through the 70s most places. Lows Wed night in the 60s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Trough axis tracks across the region Thursday night as the
surface low tracks just north of the region. Will keep mention
of chance POPs across the northeast portion of the local area
Thursday night. Dry conditions and a clearing sky is forecast
Friday as the trough axis and deepest moisture push offshore and
westerly flow aloft commences. Temperatures Friday generally
around average in the mid to upper 70`s. Upper level flow
becomes northwest Friday night and Saturday ahead of an upper
level ridge building over the Ohio Valley. A warm front lifts
into the region Saturday, providing a focus for showers and
thunderstorms, but overall moisture is expected to be limited.
Will keep only slight chance POPs for the Piedmont Saturday at
this time. Warmer, with highs in the upper 70`s to low 80`s.
Better chances for showers and thunderstorms are expected
Saturday night as upstream convection develops and tracks along
the frontal boundary and into the region. However, spatial and
timing differences exist so have capped POPs in the low end
chance range. Thereafter, unsettled conditions persist Sunday
through Monday as an upper level trough tracks across the
Midwest into the eastern CONUS. A great deal of uncertainty
exists in the medium range guidance, but it appears moisture
return will be limited. Will keep mention of low end chance POPs
in the forecast. Highs both days generally in the low to mid
80`s.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
-- Changed Discussion --
Poor aviation conditions will continue through much of the TAF
period. A frontal boundary is currently located just south of the
region with waves of showers riding along the boundary. A more
potent low pressure system will track along the boundary this
evening. MVFR to IFR conditions with low clouds and reduced
visibilities due to periods of moderate/heavy rain will persist
through tonight. Heavier rain departs the area mainly after 06Z, but
low ceilings and the potential for fog will persist through
Wednesday morning.

Outlook: A cold front is expected to impact the region Wednesday
afternoon and into Wednesday night bringing the chance for more
showers and thunderstorms/adverse aviation conditions. Scattered
afternoon showers, and potentially a few thunderstorms, are expected
to develop on Thursday allowing for the chance of more sub-VFR
conditions. Dry/VFR conditions return for Friday and Saturday.
-- End Changed Discussion --

&&

.MARINE...
Rather challenging forecast with respect to confidence and timing of
any SCA level winds due to a wide range of model solutions even in
the short term. Low pressure progged to lift NE along a frontal
boundary late today / tonight. The actual strength of the low as it
tracks across the lwr Ches Bay and off the Delmarva will determine
just how strong the NNE winds will be. Believe there is just enough
agreement for a 6-10 hour period of SCA winds across the Ches Bay
from 22Z through 08Z tonite to post marginal SCA headlines. Not
enough confidence hoist any headlines along the coastal waters so
held off there. This includes seas as they are running about a foot
below current forecast. Seas may eventually reach 5 feet out near 20
nm, but expect this would be more swell driven from the low moving
offshore rather than wind driven.

The next front pushes offshore Thursday night, with increasing
southwest winds Thursday ahead of the front. Minimal SCA conditions
are possible.

&&

.TIDES/COASTAL FLOODING...
Higher astronomical tides results in above normal water levels
this week. Rather wide spread in model guidance as to where the
low actual tracks makes for a difficult forecast. Expect some
northern sites to reach action stage during the afternoon high
tide cycle today.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory until 10 AM EDT Wednesday for ANZ630>632-
     634.
     Small Craft Advisory until 4 AM EDT Wednesday for ANZ638.
     Small Craft Advisory from 10 PM this evening to 4 PM EDT
     Wednesday for ANZ650-652-654.
     Small Craft Advisory from 10 PM this evening to 4 AM EDT
     Wednesday for ANZ656-658.
-- End Changed Discussion --

&&

$$
SYNOPSIS...JDM
NEAR TERM...AJZ/JDM
SHORT TERM...AJZ/JDM
LONG TERM...SAM
AVIATION...AJB
MARINE...MPR
TIDES/COASTAL FLOODING...