FXUS61 KLWX 191909

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
309 PM EDT Sun May 19 2019

A warm front will push northeast of the area. A cold front will
approach from the Ohio Valley Sunday night and cross the region
Monday. High pressure will return for the middle of next week.


Heavy showers and a few severe thunderstorms are moving
northeast across parts of eastern West Virginia and central
Maryland. So far, two Severe Thunderstorm Warnings have been
issued for parts of the eastern West Virginia Panhandle and
parts of central Maryland. Small hail, lightning and very heavy
rainfall has been occurring with this activity. A Severe
Thunderstorm Watch has been issued for western and central
Maryland and northern and eastern West Virginia. As we close in
on the 4pm to 6pm timeframe, additional heavy showers and severe
thunderstorms could develop over and east of the Potomac
Highlands and farther east toward the Blue Ridge Mountains.
Although the current Severe Thunderstorm Watch doesn't cover the
metro areas, a few strong thunderstorms could occur late this
afternoon and evening. Much of our CWA remains in a Severe
Thunderstorm Watch, except for southern Maryland.

Thunderstorms will be weakening and moving northeastward later
this evening and overnight. The chance POPs will likely linger
until early morning.


An associated cold front with the low pressure over the St.
Lawrence Valley Monday will move across our CWA Monday. While
instability will be less than today, decent CAPE and shear
profiles will coincide with frontal convergence. Hence, the
frontal zone should be marked by scattered showers and thunderstorms.
Again, gusty winds will be a threat--this time sub-severe--as
model soundings have indicated for a couple of days now a
potential to mix 30-40 kt. Our eastern one-third of our CWA is
under a Marginal Risk of severe thunderstorms Monday into Monday
evening. Any activity should push south/east of the area before
sunset as a cooler and drier airmass advects in. Monday night's
temperatures should be back in the 50s.

High pressure will build across the area from central Canada
Tuesday. Believe gusty northwest winds (15-20 kt) will continue
in the morning on the back side of the departing low. The cold
advection will be responsible for highs around 70.


A upper level high will build over our region through Saturday. High
pressure at the surface will be in place over the mid-Atlantic and
the southeast US. This set up will lead to a warming trend
throughout next week. As the upper level high remains over our
region, upper level shortwaves will move through the system and
affect our area periodically. There is still a lot of uncertainty on
when and where these disturbances will move through the mid-
Atlantic. The location of the disturbances will all depend on the
overall location of where the upper level high/ridge settles along
the east coast. The main result of this setup will be the potential
for scattered showers and thunderstorms to form and move through our
region each day.


Showers and a few severe thunderstorms will move near the MRB
and CHO terminals this afternoon. Showers and thunderstorms
could pose a brief MVFR or IFR threat to MRB and CHO, and
perhaps IAD the remainder of this afternoon.

Once shower and thunderstorm activity diminish this evening,
when patchy fog may develop again, there should be an uptick in
activity Monday (by midday) as the cold front crosses the
terminals. Fropa will clear all terminals before 00Z Tuesday,
likely by several hours.

The airmass will be substantially drier Monday night and
Tuesday. Higher confidence VFR will prevail.

VFR conditions are expected for all terminals next week as high
pressure builds into our region. Flight restrictions could be
possible within showers and thunderstorms.


A couple of stray thunderstorms could move across parts of the
Potomac River near D.C. or over the northern Chesapeake Bay
through mid evening. The gradient wind sufficient to support a
low-end Small Craft Advisory, but any stronger thunderstorm
likely will require a Marine Warning.

A cold front will cross the waters Monday. Once again, scattered
showers and thunderstorms anticipated to be coincident with the
front. Model soundings suggest deep mixing possible. While some
of this likely tied to showers/thunderstorms, believe there is
enough of a gradient component to issue a Small Craft Advisory
for Monday late morning through afternoon as well.

Winds likely to subside after dark due to the nocturnal
inversion, but the pressure gradient with the related low will
support a new round of mixing on Tuesday. More Small Craft
conditions possible. Quiet weather expected Wednesday-Thursday.


Positive water level departures will linger through tonight. The
wind regime will do nothing to change things through tonight.
If anything, water levels could rise slightly, making for a more
widespread minor flood with high tide early Monday morning. A
cold frontal passage Monday night hopefully will ease this
condition by Tuesday.


MARINE...Small Craft Advisory until 8 PM EDT this evening for
Small Craft Advisory from 11 AM to 6 PM EDT Monday for


Back to Main Forecast Discussion Page