Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 290114
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
914 PM EDT Sun Aug 28 2016

.SYNOPSIS...
High pressure will remain over the Mid Atlantic through
Monday before moving offshore. A cold front will move through the
area Wednesday night. High pressure returns for late in the week.

&&

.NEAR TERM /THROUGH MONDAY/...
Ridge of high pressure persisting over the region through tonight
with subsidence leading to generally dry conditions. A weak
surface trough over western PA combined with weak mid level
shortwave energy has triggered showers and thunderstorms across a
good portion of the state. However, airmass over our CWA stable
enough to preclude anything more than a stray shower or
thunderstorm into the far northwestern corner around midnight.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Upper level trough swings through Monday with a surface front
passing to the north, looking to be washed out south of the
Mason-Dixon. Region will then be on the eastern periphery of
surface high pressure as well as the eastern side of ridging
building across the central US. Moisture advection on the surface
flow which could result into a bit more of instability Monday
afternoon, so cannot rule out scattered showers and thunderstorms
over the higher terrain of the western CWA, but generally staying
west of the Blue Ridge. Anything that forms will weaken overnight
Monday.

The ridge weakens on Tue allowing for better chances of convection
especially west of the Blue Ridge, but still not likely to reach
the metros.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
A cold front will drop into the area from the northwest Wednesday
into Wednesday night. The operational GFS runs the last day or so
have wanted to push the surface front south ahead of the 850 mb
front, which means northerly low-level flow by the time any
forcing gets here. This is not totally out of the question given
the anomalously strong surface high building in behind the front,
but a few showers and thunderstorms will still be possible in the
frontal zone late Wednesday afternoon and Wednesday evening.

GFS/ECMWF have 850 mb temperatures dropping into the 12-15 C range
behind the front for the latter portion of the week indicating a
potential for temperatures several degrees below normal. The airmass
will be much drier on a northerly flow as well.

A few ensemble members of the GEFS/EC indicate a potential for some
shower activity moving north associated with Gulf of Mexico moisture
late in the upcoming weekend. Temperatures and humidity will begin
to rebound during this time as well.

&&

.AVIATION /01Z MONDAY THROUGH FRIDAY/...
Few aviation impacts expected through tomorrow afternoon with
generally light/variable winds. Only low chance of MVFR possible at
KCHO/KMRB due to patchy fog prior to sunrise. Low chance of TSRA
at KMRB tomorrow afternoon, though kept out of the TAF due to low
probability.

A shower or thunderstorm is possible late Wednesday afternoon or
evening along a cold front. Southerly flow less than 10 knots
Wednesday will become northerly Wednesday night and increase to 10
to 15 knots Thursday with a few gusts possible.

&&

.MARINE...
Occasional easterly gusts to 20 knots this evening, have covered
with MWS. Otherwise sub-SCA conditions on all waters through
Wednesday. Northerly flow behind the front could result in SCA
level gusts Thursday.

&&

.CLIMATE...
Ranking of summer 2016 in terms of average temperature (JUN 1 - AUG 27)

Site          Rank                    Average Temperature

DC   3   80.5
Balt          18  77.3
IAD            3                            77.3

&&

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

&&

$$
SYNOPSIS...LFR
NEAR TERM...Sears
SHORT TERM...Sears/LFR
LONG TERM...DFH
AVIATION...MSE/DFH
MARINE...Sears/DFH
CLIMATE...LWX



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