Preview of NWS' New Version of Forecast
This preview is not operational and should not be used for support decisions.

Area Forecast Discussion (AFD)

Issued by Baltimore/Washington (LWX)

FXUS61 KLWX 241449

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1049 AM EDT Wed Apr 24 2019

A cold front will stall across southside Virginia or northern
North Carolina this afternoon. The front will return as a warm 
front Thursday before a low pressure system tracks across the 
Ohio Valley toward the northeastern United States. A second cold
front, attached to the low pressure system, will approach 
Friday. High pressure will build in behind this front for the 
early part of the weekend. Another storm system could approach 
the region during the second half of the weekend.


A stalled front is across southern Maryland and the Virginia
Piedmont. Clouds are eroding from north to south on the north
side of the front as drier air filters in behind the front.
The front will lift north as a warm front tonight and bring a
chance for showers mainly in the Potomac Highland.


A weak shortwave passage early Thursday will support scattered
to perhaps numerous showers as upglide from the advancing warm
front overspreads the region. While clouds may be plentiful
Thursday afternoon-evening, it appears as though there may be a
break in forcing mechanisms. 

Thursday night into Friday morning, heights drop as a trough
axis/surface cold front cross the area. Shear and moisture will
both be available in abundance. Minimal instability may be able
to develop as well. Will maintain slight chance/chance thunder
in forecast, primarily in advance of the trough axis.

Guidance suggests that wind fields increase in the wake of this
front...mainly for Friday night. Momentum transfer should be


Cooler and windy (gusts up to 30 mph) Saturday in the wake of 
deepening low pressure area over Downeast Maine. Weak high pressure 
returns for Saturday night before a weak cold front crosses the area 
Sunday afternoon. Not much in the way of moisture or instability 
available with this front, so the risk of showers appears isolated 
at best. Better convective potential appears possible right at the 
end of the month and the first few days in May as a sfc front 
becomes stationary near the area and multiple waves of low pressure 
ride along the front. High degree of uncertainty here with exact 
position of sfc front and thus temperatures and precip timing, but 
time of the year favors back door fronts to push farther south than 
models suggest.


VFR flight conditions will prevail this afternoon through tonight.
Winds from the northwest will gust 20 to 25 knots through this

Showers will affect the terminals Thursday, with perhaps a brief
break Thursday afternoon or early evening, before more showers
arrive Thursday night. A cold front will support additional
showers, with perhaps heavy rain and gusty winds Friday. Would
not rule out a thunderstorm on Friday either. 

Flight restrictions plausible Thursday night into Friday. 
NW winds will gust to around 25 kt Sat before diminishing to 10 kt 
or less Sat night.


A Small Craft Advisory remains in effect for the northern
Potomac and northern and central Chesapeake Bay through much of
this afternoon. 

Conditions will be quieter tonight into Thursday as the front
settles south of the Bay and then slowly marks its return.
Showers will affect the waters Thursday into Friday. A cold
front will be the triggering mechanism on Friday; a couple of
thunderstorms will be possible at that time. Would not rule out
associated gusty winds (Marine Warnings). Gradient winds will 
increase in the wake of the front Friday night; high confidence 
in Small Craft Advisories.

High end SCA conditions expected Saturday with an outside chance of 
gale conditions (1 in 10 chance) before winds diminish Sat night to 
10 kt or less.


MARINE...Small Craft Advisory until 6 PM EDT this evening for