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fxus61 klwx 271819 
afdlwx

Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
219 PM EDT Thu Apr 27 2017

Synopsis...

A weak cold front crosses the area from the west tonight. High
pressure over the area Friday, then dropping off the southeast
coast Saturday. A cold front will move over Pennsylvania
Saturday night before lifting north. A cold front will move
through the region from the west Monday night.

&&

Near term /tonight/...

After watching low clouds/fog slowly dissipate both of the last
two mornings this pattern should not repeat itself tonight. A
weak cold front will move west of the Appalachians this
evening...reaching the Bay around midnight. Showers can be seen
on regional radar across WV. Given that low clouds have eroded
temperatures are now climbing into the upper 70s/lower 80s.
Neither cape nor helicity look particularly good but Storm Prediction Center has
placed much of the western half of the forecast area in marginal
risk, and wpc has placed the area just west of our forecast
area in a marginal risk of excessive rainfall. Given the slow
movement of the line the latter may be the greater concern for
the evening shift team, but there is stronger convection over
Georgia/SC which may rob the line further north of energy.

Have chance pops/isolated thunderstorms forecast for the entire
area this evening.

Lows ranging from the upper 40s in The Highlands to the mid 60s
in the cities. Much of the area will drop to 55-60.

&&

Short term /Friday through Saturday night/...

Weak front will move offshore Friday morning. Light fog is
possible but not expected to be as dense/widespread as previous
two nights.

We will be in a warming trend heading into the weekend as high
pressure strengthens off the SC coast. This will pump warm air
into the mid Atlantic, and by Saturday temperatures will have a
decent shot at topping 90.

The record temperatures for April 29 - we'll be close to these
values:

Highs Max high min

Dca 91 68
BWI 91 67
iad 87 62

&&

Long term /Sunday through Thursday/...

High pressure to the southeast will break down with a warm front
sliding northward across the d.C. Area Sunday into Sunday night.
There is a chance for showers and a thunderstorm, mainly Sunday with
the warm front nearby.

An increasing southerly wind will usher in warmer and more humid air
to help fuel showers and thunderstorms, mainly Monday afternoon and
evening ahead of a strong cold front. A few thunderstorms could
contain strong winds.

Gusty westerly winds and drier and cooler air will filter into the
region Tuesday and Tuesday night behind the cold front as high
pressure builds in from the west.

High pressure moves offshore Wednesday, while keeping conditions
dry. A return flow will be an indication that a new warm front will
try to push across the region late Wednesday into Thursday.

The Thursday storm system that is expected to develop along the warm
front could intensify over the Ohio Valley before sending energy
eastward into the mid-Atlantic later in the day Thursday.

&&

Aviation /18z Thursday through Tuesday/...

VFR through the afternoon/early evening. Isolated showers and
thunderstorms will be possible at taf sites this evening. These
are expected to weaken while progressing east of the mountains.

Light fog possible Friday morning then VFR at all sites Friday
into Saturday.

MVFR to IFR conditions expected Sunday and Sunday night with showers
and a thunderstorm in the area near mrb, iad, mountain and BWI terminals.
VFR conditions elsewhere. IFR to LIFR conditions Monday and Monday
night with showers and thunderstorms. Winds east 5 to 10 knots
Sunday, southerly 5 to 10 knots Sunday night, then southwest 10 to
15 knots Monday, and southwest 10 knots Monday night.

&&

Marine...
Small Craft Advisory is in effect for all waters but is not currently occuring
anywhere. Will leave up but let evening shift consider if this
should remain. There is an approaching boundary but it is not
very strong - showers/isolated thunderstorms will be possible
around midnight.

No marine hazards expected Sunday and Sunday night. Small craft
advisories possible Monday and Monday night. Winds east 10 knots
Sunday, southeast 10 knots Sunday night, increasing southwest 15
knots gusts 20 knots Monday, and southwest 10 to 15 knots Monday
night.

&&

Tides/coastal flooding...

The evening high tide cycle is the lower of the two so no
coastal flood threat. Later shifts will have to contemplate the
Friday morning high tide.

&&

Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...none.
Virginia...none.
WV...none.
Marine...Small Craft Advisory until 5 am EDT Friday for anz531>534-537-
539>541-543.
Small Craft Advisory until midnight EDT tonight for anz530-535-
536-538-542.

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