Area Forecast Discussion
Issued by NWS Sterling, VA
FXUS61 KLWX 190044
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
844 PM EDT Sun Sep 18 2016
A weakening boundary will stall out over the area tonight through
MOnday night. High pressure will build into the region for mid to
.NEAR TERM /THROUGH MONDAY/...
An upper-level trough will strengthen as it passes through the
Ohio VAlley overnight while a surface trough stalls out overhead.
A south to southwest flow ahead of this system has ushered in
plenty of moisture. Latest mesoanalysis shows a plume of PWATS
greater than 2 inches over North Carolina. This should advect
into the area overnight into Monday.
Best signal in terms of moisture convergence, deformation, and
omega fields, for widespread showers and embedded thunderstorms
will develop over the area toward morning with the best chance for
heaviest precipitation being near and east of Interstate 95. Jet
dynamics also become more favorable on Monday as region is
projected to lie in the right entrance region of the upper jet.
All of this means that showers/embedded thunder will develop
overnight into Monday morning. Total rainfall area-wide generally
0.5-1.5 inches, locally higher in any areas that see repeated
convective activity especially near and east of Interstate 95.
Because of dry antecedent conditions, flash flood guidance values
are quite high, from about 2-3" in 1 hour to 3-5" in 6 hours, so
flash flood threat remains low, however can`t rule out something
Shower activity tapers off a bit by Monday afternoon, especially
western areas. Lows tonight in the mid 60s to low 70s, with highs
Monday in the 70s to near 80F.
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
With frontal boundary washing out and dissipating near the region
and the remnants of Julia still meandering off of the Carolinas,
will see at least a chance for some rain showers continue into
Monday night and Tuesday across our southern and eastern regions.
High pressure should finally start to push southward into the area
by Tuesday night. Lows in the 60s and highs in the 80s for
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Surface high pressure keeps dry conditions over our region
Wednesday into parts of Saturday. Cold front pushes south Saturday
into Sunday, which could bring precipitation into our area. High
temperatures will be above normal... in the upper 70s and low 80s.
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
VFR at all TAF sites this evening. MVFR and possibly some
localized IFR conditions then likely again later tonight and into
Monday with showers and a few thunderstorms moving into the
region. Conditions should improve gradually by Monday night with
VFR returning Tuesday.
VFR conditions expected Wednesday into Friday with high pressure
dominating conditions over our area.
Southerly winds will increase ahead of a trough axis tonight. A
small craft advisory is in effect for portions of the lower tidal
Potomac and Chesapeake Bay from until 6 AM. Showers/t-storms also
expected later tonight and into Monday. Winds taper back off for
Monday through Tuesday.
High pressure keeps light winds and dry conditions over our area.
Therefore, small craft advisory conditions not expected Wednesday
into Friday as winds will be below 15 kts.
South flow across the waters has maintained positive water levels
of 0.75 to 1.0 ft above astronomical prediction (normal). Minor
coastal flooding is expected to continue at the sensitive sites in
Anne Arundel and St. Mary`s County as well as Washington DC and
Alexandria during the high tide cycle tonight into Monday morning.
Coastal flood advisories continue at this time. Minor flooding is
possible during the high tide cycle Monday afternoon into Monday
night as well.
DC...Coastal Flood Advisory until 2 AM EDT Monday for DCZ001.
MD...Coastal Flood Advisory until 10 AM EDT Monday for MDZ014.
Coastal Flood Advisory until 7 AM EDT Monday for MDZ017.
VA...Coastal Flood Advisory until 2 AM EDT Monday for VAZ054.
MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ531>534-