Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
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

000
FXUS61 KLWX 141604 RRA
AFDLWX

Area Forecast Discussion...DELAYED
National Weather Service Baltimore MD/Washington DC
1204 PM EDT Mon May 14 2018

.SYNOPSIS...
A front over the area will lift north late today and tonight
then drop southward again Tuesday night and Wednesday when it
will become stationary across the area through Friday. The front
may lift north again during the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Currently, there are no echos being observed by the local
radars. Fog has mostly lifted, but low clouds linger, and it may
be a struggle today to completely mix them out. Temperatures
should rise significantly down towards CHO and west of the Blue
Ridge south of MRB, but MRB over towards NHK and points
northeast are much more questionable as far as how much the low
level cool air mixes out and temps warm up this afternoon.

The stationary boundary that has remained stretched across our
CWA the past couple of days has been expected to lift northward
today, but the speed this occurs at has a good shot of being
delayed. That said, with the assistance of passing mid level
energy this afternoon and the proximity of the boundary, we are
expecting another round of strong to severe thunderstorms this
afternoon. Showers and storms are expected to redevelop across
and northwest of the region this afternoon. An Enhanced Risk
for severe storms encompasses portions of our area, mainly south
of the I-70 corridor and west southwest of the District,
including much of the Shenandoah Valley and portions of the
Potomac Highlands, which is where the warm sector is forecast to
reside. Ample CAPE of 2000+ J/KG and sufficient 0-6km shear
values of 30- 40 kts will promote conditions favorable for
primarily damaging wind gusts and hail. Convection will wane
during the evening hours with a drier trend expected overnight.
Temperatures will settle in to the mid to upper 60s after seeing
highs top out today in the 80s, except northeast of DC where the
front will struggle and 70s are more likely. Later tonight, we
may get anothe round of low clouds and patchy fog.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
The stationary boundary will lift further northward on Tuesday,
residing across Pennsylvania by Tuesday afternoon. Much warmer
conditions expected on Tuesday as a result with highs reaching
the lower 90s, and humidity values well above normal. We may
start with some low clouds and patchy fog, but it should mix out
more efficiently than what we are seeing today. Continued
showers and thunderstorm chances expected Tuesday afternoon,
with another Slight Risk of severe storms possible for much of
the area. Shear values will be less on Tuesday, but CAPE should
be higher, so strong to severe storms will be possible. The
stationary front dips back southward across our area on
Wednesday, bringing continued threat for showers and afternoon
thunderstorms once again, but with less severe risk.
Temperatures will be cooler Wednesday with ample cloud cover and
showers around, with highs topping out around 80, and lows in
the mid to upper 60s both Tuesday and Wednesday nights.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Tropical moisture will be funneled northward across the mid
Atlantic states Thu-Fri between a mid-upper level trough over
the lower MS valley and a strong subtropical ridge over the
western Atlantic. A stationary front across the area will also
act to enhance rainfall over the area. In addition, largely
unidirectional flow Thu night also suggests potential for
training convection. The Thu night-Fri period looks like the
wettest period of the week particularly late Thu night into Fri
morning. Widespread amounts of 1 to 2 inches appear likely
during this period. 13/18Z MMEFS guidance show potential for
river flooding based on the 10 to 50th QPF percentiles. Given
all the ingredients described above and increasingly wetter
soils, some flooding appears likely this week, but location and
timing are still uncertain. It does appear though as the I-95
corridor would be the most vulnerable to flooding.

&&

.AVIATION /16Z MONDAY THROUGH FRIDAY/...
IFR/LIFR conditions being observed across the terminals this
morning with low CIGs, though VIS restritions are ending, while
winds remain light and variable. These restrictions will
slowly continue improving, likely returning to VFR early
afternoon. Showers and thunderstorms will return to the
terminals this afternoon, bringing episodes of sub-VFR condtions
once again, with winds favoring a more southerly trajectory. Low
clouds and fog may redevelop again tonight, but should be less
persistent tomorrow morning. Another round of showers and storms
is expected later Tuesday afternoon and evening.

The persistent stationary boundary will lingering across the
Mid Atlantic through midweek, bringing plenty of clouds and rain
chances to the terminals. Sub-VFR conditions will be possible
through this period as a result, with winds generally remaining
10 knots or less, outside of convection.

IFR conditions seem likely Thu night-Fri morning with heavy
rain.

&&

.MARINE...
No headlines expected through tonight with light winds
prevailing over the waters. Afternoon and early evening
showers/thunderstorms will once again cross the waters, bringing
the threat for gusty winds which could result in Special Marine
Warnings. SCA conditions possible during the day on Tuesday as
southerly winds increase and become gusty. Sub SCA conditions
likely return through Wednesday night as light winds prevail.
With the persistent stationary boundary remaining near the area,
periods of showers and thunderstorms will continue each day,
bringing the possibility for Special Marine Warnings should
conditions warrant.

SCA conditions possible Fri afternoon into Sat in southerly
flow.

&&

.TIDES/COASTAL FLOODING...
Minor coastal flooding possible at Annapolis and Straits Point
during the late evening/early morning high tide cycle next few
days. New minor coastal flood thresholds are expected to be
implemented on Tue for Annapolis and Straits Point assuming
there is no flooding ongoing which may temper the coastal flood
threat somewhat.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.

&&

$$
SYNOPSIS...LFR
NEAR TERM...BKF
SHORT TERM...BKF
LONG TERM...LFR
AVIATION...BKF/LFR
MARINE...BKF/LFR
TIDES/COASTAL FLOODING...



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.