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Area Forecast Discussion (AFD)

Issued by Baltimore/Washington (LWX)

                            
051 
FXUS61 KLWX 230804
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
404 AM EDT Sun Sep 23 2018

.SYNOPSIS...High pressure will continue to build across northern
New England through Monday, then move off the coast Tuesday. The
next cold front will move across the area during the middle part
of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...

Overrunning/warm advection pattern is expected to strengthen
later this morning and will be aided by RRQ jet dynamics to result
in a period of moderate rain today. Heaviest amts are expected 
across eastern WV (Grant, Mineral into Hampshire and Hardy 
counties). Rainfall amounts are likely to average around 0.75 
inches with up to 1.5 inches possible as suggested by GEFS and 
EPS members. Given that the rain is expected to be stratiform in
nature and fall in a 12-hr period, most places should be able 
to handle this amount of rain, so no flooding issues are 
anticipated.

Rain should become much lighter late tonight as upper forcing
weakens and shortwave ridge builds in. 

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...

Another round of light to moderate rain appears likely late Mon
into Tue morning as h85 warm front lifts through the area aided
by shortwave energy and h25 jet dynamics. Rain should taper off
Tue afternoon, but with low clouds remaining. 

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...

The upper levels during the second half of next week and into the 
weekend will be undergoing a change from a pattern featuring large 
scale ridging off the southeastern US coastline and large scale 
troughing over the upper midwest to a pattern that is much more 
zonal in nature.

A low pressure system will be intensifying and moving northeastward 
through the Great Lakes on Wednesday, placing the region in 
southwesterly flow out ahead of an approaching cold front. The cold 
front will make its way eastward during the day, likely crossing 
into the area during the afternoon and evening hours. Thus, there 
will be increased chances of showers/thunderstorms, especially 
Wednesday afternoon and evening. Temperatures should be above normal 
with morning lows in the 60s to near 70F and highs in the 80s.

The frontal boundary will likely stall or wash out near the region 
Wednesday night through Thursday night, although there is 
uncertainty with how far south/east the front can progress. With a 
possible frontal boundary nearby, good jet dynamics aloft, southwest 
flow in the mid/upper levels, and northeasterly surface flow induced 
by a strong high pressure over SE Canada, will favor model solutions 
depicting rain chances continuing on Thursday/Thursday night. 
Temperatures should cool behind the boundary to near normals, 
although will be dependent on evolution of clouds/rain.

As the pattern continues to transition, another system will pass 
near or north of the region on Friday, allowing high pressure to 
build into the area over the weekend. Will keep lingering shower 
chances (although lower) on Friday, with drying shown by Saturday. 
Highs in the 70s, lows in the 50s to near 60F.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...

Cigs expected to drop as the day goes on as sfc wedge 
strengthens and rain becomes a little heavier. Expect IFR cigs 
at all terminals by 18Z and remaining like that through Mon.
Some improvements in cigs are possible Tue as sfc wedge begins 
to weaken, but expect cigs to remain at least into MVFR
category.

Primarily VFR likely Wednesday, although chances for 
showers/thunderstorms will be increasing by the afternoon. Potential 
then exists for sub-VFR conditions to return Thursday as the front 
may stall near the region leading to areas of low clouds/showers.


&&

.MARINE...

Will likely be issuing SCA for the lower bay and lower Potomac,
winds then expected to strengthen later today and remain gusty
through at least Monday as pressure gradient tightens.

Potential exists for SCA conditions to develop by Wednesday 
afternoon ahead of an approaching cold front. Chances for 
showers/thunderstorms will be increasing as well. Sub-SCA conditions 
likely Thursday as a front stalls near or south of the waters.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 8 AM this morning to 6 PM EDT Monday 
     for ANZ532>534-537-541>543.

&&

$$
SYNOPSIS...LFR
NEAR TERM...LFR
SHORT TERM...LFR
LONG TERM...MM
AVIATION...MM/LFR
MARINE...MM/LFR