Area Forecast Discussion
Issued by NWS Sterling, VA

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
000
FXUS61 KLWX 120136
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
936 PM EDT Fri Aug 11 2017

.SYNOPSIS...
A cold front will move through the area Saturday
evening and become stationary across the Carolinas early next
week. Weak high pressure builds over the area Sunday and holds
through the end of next week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
A cold front will slowly track through the Ohio Valley overnight
while high pressure remains over the Atlantic. A southerly flow
between these systems has ushered in plenty of moisture across
our area. The deep moisture and forcing from a surface trough
has led to showers and thunderstorms this afternoon. The trough
will remain in place overnight while an upper-level disturbance
passes through in the southwest flow aloft. This is likely to
trigger more showers and isolated thunderstorms
overnight...especially across northern and central Virginia
toward the Washington and Baltimore Metropolitan areas into
southern Maryland. This is where moisture will be deepest near
and east of the pressure trough. Localized flood/flash flooding
is possible due to heavy rainfall. At this point...it appears
that flash flooding should be localized so a Flash Flood Watch
has been issued with this package...but it will have to be
monitored overnight for the urban areas into southern Maryland.

Patchy dense fog is possible overnight due to the rainfall and
high amounts of moisture.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
The cold front over the Ohio Valley will approach the area
Saturday morning before passing through during the afternoon and
evening hours from west to east. Nmrs showers and t-storms are
expected along and ahead of the boundary. Greatest risk for
flash flooding and severe wx appears over srn MD, the Chesapeake
Bay and the Delmarva. Showers should move east and south of the
area by Sat evening.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Uncertainty remains in place early next week with models diverging
on the track of a wave of low pressure progged to move east along
the stalled front to our south. The 0Z ECM continued to track it
further north, moving across our region, while others such as the
latest GFS and 0Z Canadian continue to allow high pressure to the
north to build south and generally dominate. However, even with the
drier solutions, an easterly flow may result in some clouds and
perhaps some upslope showers in the mountains. Overall, however,
temperatures will be near to perhaps a bit below normal early in the
week.

By Wednesday, high pressure dominates on most guidance including the
ECM, with temperatures starting to warm a bit. By late Thursday and
particularly Friday however, the high shifts off the coast and the
next front is approaching, with a gradually increasing risk of
showers and t-storms.

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
Showers likely with isolated thunderstorms
overnight...especially across the eastern terminals. Low clouds
and areas of fog will cause MVFR/IFR conditions overnight.
SubIFR conditions are possible due to fog across the western
terminals toward morning. Another round of showers/t-storms
expected again Sat with fropa.

Depending on the strength of easterly flow and the path of a low
pressure system moving eastward along the front stalled to the
south, a period of sub VFR conditions may occur early next week due
either to low clouds or rain. Uncertainty remains high, however.

&&

.MARINE...
Srly winds will continue overnight with SCA conditions
expected. Winds may diminish a bit Saturday...but gusts close to
SCA criteria are expected. Have capped gusts around 15 knots for
now. T-storms Sat may require SMWs.

Uncertainty exists regarding early next week on the strength of an
easterly flow as a front remains south of the region and a wave of
low pressure pushes east along it. However, at this time SCA
conditions are not expected.

&&

.TIDES/COASTAL FLOODING...
Southerly flow has caused tidal anomalies around one-half to one
foot above normal. This will likely cause water levels to reach
caution stage for sensitive areas near high tide tonight and
again on Saturday. Latest forecasts keeps water levels below
minor flooding since the flow will be weakening a bit...but it
will be close during the high tide cycle near Straits Point and
Annapolis Saturday morning.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 6 AM EDT Saturday for ANZ530>534-
     536-537-539>543.

&&

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



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