Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 031349
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
949 AM EDT Wed Jun 3 2020

.SYNOPSIS...
A warm front will lift north of the area early this morning,
ushering in a much more summerlike air mass. A cold front will
approach from the north tonight but never quite reach the area,
stalling just to the north Thursday and Friday. A stronger cold
front will then sweep across the area late Saturday, with
Canadian high pressure building in for Sunday and Monday.

&&

.NEAR TERM /THROUGH THURSDAY/...
Partly cloudy across the region, with temperatures already in
the upper 70s to low 80s. Additionally, dew points in the low to
mid 60s have it feeling quite muggy out. Warm front has lifted
well to the north into northern PA at this hour, where severe
thunderstorms have started up already. For our region though,
remaining dry at this hour, with nothing really showing up on
radar over the region. The storms currently over central PA will
drop southeast through the early afternoon, but should pass to
our north.

PREVIOUS DISCUSSION: Aloft, a broad ridge dominates the
southern US while a closed low is in Atlantic Canada. Another
shortwave is crossing the western Great Lakes and northern
Plains, with a shortwave ridge pushing across the Appalachians
towards our region.

With the much warmer air mass being solidly in place and limited
cloud cover, today looks like the hot day it has long been
advertised, with highs reaching the low to mid 90s. Fortunately,
dew points will remain fairly low, in the 60s, so heat indices
are not expected to reach 100 or above anywhere. Still, this
heat may be a shock to the system, so caution should be
exercised on this first hot day of the year.

Shortwave energy and an approaching cold front from the north
will cause more thunderstorms to develop in PA this afternoon.
Some of these may try to reach our region, especially locations
near the PA border, late this afternoon and this evening, and
with adequate CAPE and shear, some severe weather is possible.
Biggest threat will be damaging winds and perhaps some hail.
Strong westerly downslope flow most likely helps storms to
weaken before approaching DC and Baltimore proper, but a
marginal severe weather risk exists down to the I-66/US 50
corridor, with a slight risk further north, primarily over
northern MD.

After storms wane overnight, warm and humid conditions will
prevail, with lows in the 60s to near 70.

On Thursday, the front stalls just to the north, so the warm and
more humid air mass will remain in place. Another weak shortwave
will approach from the west during the latter portion of the
day, which likely helps fuel a more home-grown round of showers
and storms. While CAPE and shear are not as impressive, some
isolated severe storms, probably more pulse-type, seem possible.
In addition, with the flow now parallel to the stalled front and
also weakening overall, slower moving, training storms will be
possible, which could pose an isolated flooding risk. SPC and
WPC both have our region in a marginal risk for severe weather
and excessive rain. Highs will be a bit lower due to more clouds
and better chance of rain, but still near 90.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
Shower/storm activity Thursday evening should diminish overnight
as the shortwave pushes east and insolation ends. Lows will
remain muggy, in the 60s to near 70.

The stalled front remains north of the region through Friday
night, in fact likely dissipating ahead of another cold front
approaching for Saturday. Air mass will remain very warm and
humid, but shortwave energy looks less without a significant
shortwave or vort max in the vicinity. Thus, while
shower/t-storm risk will continue Friday afternoon, odds look
slightly lower in coverage and significance. Highs will again be
near 90. Friday night will be fairly similar to Thursday night
aside from a bit less storm coverage to start the night, with
lows again in the 60s to near 70.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Showers and t-storms still look possible on Sat as area remains
in warm moist air mass ahead of a cold front that will be
crossing the area during the afternoon. However, models show
best low-level convergence across the eastern shore of MD, lower
Potomac River, and southeastern Virginia. T-storm coverage
definitely looks questionable given only weak forcing with
isolated to scattered cvrg at best and mainly over southeastern
areas.

Canadian high pressure builds over the region for Sun-Mon with
cooler temperatures and low humidity. The high then moves
offshore Tue with srly flow developing leading to increasing
warmth and humidity. The remnants of Cristobal will merge and
get absorbed by a low pressure center over the western Great Lks
and southern Canada by the middle portion of next week. The
Euro shows the remnant low of Cristobal strengthening due to
baroclinic forcing with its associated cold front passing
through the area next Wed.

&&

.AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
Mainly VFR through Friday night. Main concern is for scattered
thunderstorms, with best coverage likely Thursday
afternoon/evening. Any storm could drop cigs/vsby to IFR
briefly, and stronger wind gusts will also be possible.
Otherwise, locales which receive rain could see patchy fog the
following morning for a time, but odds on this are low.

Isolated to scattered t-storms possible Saturday afternoon
mainly southeast of terminals. Fair weather Sunday under
Canadian high pressure.

&&

.MARINE...
Southwesterly flow will increase today ahead of an approaching
cold front, but the hot air mass will mix poorly over the cooler
waters. Thus, have SCA for the more sheltered waters which get
more land influence, with lighter winds expected over the more
open waters. After this ends, winds look fairly light through
Friday night as the front stalls and then likely dissipates to
the north. Thus, biggest concern tonight through Friday night is
likely the potential for t-storms, which reach peak coverage
most likely late Thursday. Any storm could necessitate special
marine warnings, so boaters should remain alert, particularly
later in the day.

Isolated to scattered t-storms expected Sat mainly over lower
Potomac River. Possible SCA conditions Sunday in northerly flow
as high pressure builds over the region.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 7 PM EDT this evening for ANZ530-
     531-535-538-539-541-542.

&&

$$
SYNOPSIS...RCM
NEAR TERM...RCM/CJL
SHORT TERM...RCM
LONG TERM...LFR
AVIATION...RCM/LFR
MARINE...RCM/LFR



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