Area Forecast Discussion
Issued by NWS Wakefield, VA-- Remove Highlighting --
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FXUS61 KAKQ 230812
Area Forecast Discussion
National Weather Service Wakefield VA
412 AM EDT Sun Apr 23 2017
A frontal boundary becomes nearly stationary across the Carolinas
today. A strong low pressure system will cross the region
through midweek...and bring periods of moderate to heavy
rainfall to the region Monday and Tuesday.
.NEAR TERM /THROUGH TONIGHT/...
Latest upper air analysis features a deepening upper level low
digging from the Mid-Mississippi Valley into the Mid-south.
This feature will slowly slide e-se into the southeast today. At
the surface, quasi-stationary boundary extended from E SC back
into the Deep South at 07z. This boundary will slowly edge
farther south through the day.
Regional radar mosaic showing a widespread light showers
moving across the area at 08z. These showers will continue to
push E-SE across central and southern VA into NC, as a
dampening/weakening upper shortwave drops across. Expect a brief
lull in areal coverage of showers around sunrise through mid
morning. At that point, expect showers to redevelop as surface
low over E TN/N GA pushes across the boundary to the south.
Resultant DVPA/weak overrunning moisture should push in our
direction and bring another round of showers to the central and
southern portions of the area from Mid-morning into the
afternoon, eventually reaching the lower MD Eastern Shore this
afternoon into the evening hours. POP slowly increases to
categorical all zones by this afternoon. QPF today 0.5-1" SW
(I-85 corridor)...to a quarter inch or less south of I-64. Light
amounts from there north through early evening. Highs upper 50s
to low 60s Coastal east...low to mid 50s as cool air wedge sets
in over the piedmont.
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
A cloudy and wet period to begin the work week. Periods of mdt
to hvy rainfall expected Monday night and Tuesday. QPF btwn 1.5
to 3.5 inches (highest across the southern third of the area).
Models in general agreement that aforementioned upr-level low
cuts off as it tracks SE across the southeast and the coastal
Carolinas. System then takes on a neg tilt Mon night that
spawns a coastal low off the se coast Monday. Resultant strong
coastal front will be conducive for heavy rainfall across the
southeast CONUS, which will eventually move in our direction
Late Monday night and Tuesday.
Look for mainly cloudy skies with periods of mdt to locally hvy
rainfall Mon/Tue as copious amounts of deep Atlantic moisture
gets entrained north and rotates around the system. Thus,
confidence remains high enough to go with likely to categorical
pops each period. Kept high pops but low chc thunder along the
Highs Mon in the mid 50s-mid 60s except 65-70 sern coastal
areas. Lows Mon nite in the upr 40s-lwr 60s. Highs Tue in the
lwr 60s-lwr 70s.
Hydro wise, no flood headlines anticipated attm with numerous breaks
in between bouts of rain expected. Do expect some healthy rises in
local river by early next week, especially if the heavy rainfall
falls over the headwaters. Given the forecasted QPF and after coord
with the RFC, expect minor flooding at Lawrenceville on the Meherrin
River by Tue. Again, this based on QPF so plenty of time to adjust
Rain tapers off from south to north Tuesday night as the upper
low pivots offshore and NE of the Delmarva overnight into
Wednesday morning. Early morning lows 55-60.
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Long term period will feature a trend towards drier and warmer
conditions. For Tue night, mid-level cutoff low and associated
sfc low start to progress offshore, with some pcpn psbl on the
backside of the systm. PoPs range from 20-40%. Warming trend
then commences for Wed as deep SWly flow develops across the
eastern seaboard, lasting through the end of the week with temps
in the 70s Wed reaching the 80s most areas Thu and Fri.
.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
As of 06Z...An east to west oriented quasi-stationary frontal
boundary was oriented to the south of the terminals. North of
the front, north/northeast winds and widespread MVFR/IFR
ceilings were present in and around the TAF sites. The forecast
calls for slow improvement for northern portions overnight into
Sunday including SBY/RIC with MVFR deteriorating to IFR
elsewhere during the afternoon/evening Sunday 00Z TAF period.
The IFR will be mainly due to low ceilings but IFR visibility
can be expected during heavier rain. Confidence in details is
moderate with indication that temporary improvement may occur
from time to time. This will be difficult to pin down time and
Northeast winds will prevail during the period. These winds
will occasionally gust to around 20 to 25 knots southeast
portions at ORF and ECG.
OUTLOOK...A well organized low pressure system will linger just off
the Carolina coast from Sunday night into early this coming week.
Unsettled weather continues into Tuesday with widespread
rainfall falling heavily at times w/degraded aviation
conditions. Current forecasts have the low moving off to the
northeast Wednesday with a high pressure ridge building into the
Southeast States from the Atlantic. Wednesday through Friday
are expected to be dry and mainly VFR.
Northeast flow prevails over the marine area, between high pressure
building into the Northeast and low pressure over the Southeast.
Speeds are generally 15-20 knots, with marginal SCA conditions in
the bay. Waves generally 2-3 feet and seas 3-6 feet (highest
southern coastal waters). High pressure builds in from the northwest
today as low pressure remains over the Southeast. Gradient winds
relax later this morning into the afternoon, resulting in a brief
lull in SCA conditions. Longer reprieve expected in the upper Bay,
so have opted to drop the headlines mid morning. In the southern
bay, marginal SCA conditions expected today with occasional gusts to
20-23 knots. Gusts of 20-25 knots also expected in the sound and
southern coastal waters today. Seas average 4-6 feet. High pressure
slides offshore tonight as low pressure slides toward the Southeast
coast. The result will be an uptick in northeast winds tonight, with
speeds of 15-25 knots. Gusts up to 30 knots in the coastal waters.
Seas increase to 5-8 feet. Am concerned guidance is not handling the
northeast flow and long period swell the best, so have opted to go
above guidance on wave heights. There is the potential for high surf
conditions as well, but there remains some uncertainty so have held
off on high surf headlines. SCA headlines return for the rivers late
tonight. Low pressure slides off the Southeast coast Monday and
deepens. Strongest gradient winds begin to expand northward Monday,
with speeds of 15-25 knots expected from the mouth of the bay
northward. A brief lull is possible for the sound Monday. Seas
remain 5-8 feet, but subside to 4-6 feet in the southern coastal
waters. Waves 3-6 feet (highest in the mouth of the bay).
Low pressure slowly lifts along the Southeast coast Tuesday and
offshore the Mid-Atlantic coast Tuesday night. Onshore flow and SCA
conditions persist. Seas build upwards of 6-9 feet Tuesday. Flow
becomes northerly Tuesday night as speeds diminish at or below 15
knots as the low lifts over the waters. Seas subside to 4-6 feet
late Tuesday night. Waves 1-2 feet. The low weakens and lifts away
from the region Wednesday as sub-SCA conditions return. Seas
forecast to drop below 5 feet late Wednesday. The next front
approaches the waters Friday.
An extended period of onshore flow will result in increasing
tidal departures thru mid week. Tidal departures will reach +1
to 1.5 feet through Sunday night along the Atlantic coast and in
the lower Chesapeake Bay and James River. Northeast flow
increases Monday, with tidal departures of 1.5 to 2 feet. Minor
flooding is expected Monday night thru Tuesday during high tide.
Flow becomes offshore Wednesday.
MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ632-634-638-
Small Craft Advisory until 10 PM EDT this evening for ANZ633.
Small Craft Advisory until 10 AM EDT this morning for ANZ630-