Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 180140

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
940 PM EDT Wed May 17 2017

High pressure will remain centered over Bermuda through Saturday.
A cold front will move south through the area late Friday
before stalling to our south on Saturday. The boundary will
return north as a warm front Sunday before a stronger cold front
from the west passes from the west through Monday into Monday
night. High pressure looks to return to the region Tuesday.


Models did a great job of identifying the low chance for thunder
from the northern Shenandoah Valley NW to PA this afternoon over
the past few days. That activity has waned. South winds and high
clouds will keep temps up; generally mid to upper 60s inland to
low 70s near shore.

A nocturnal 35-40kt jet at 950 mb is expected to develop tonight in
response to the contrast between the cold Atlantic and the warm
air mass in place. However, inversion is quickly setting up and
will not allow much of this wind to translate to the surface.


Thursday will start out much like today, but with surface
dewpoints increasing 5-10 degrees above today, expecting more of an
afternoon cumulus field. MAV guidance has decreased max temps
by a couple of degrees for Thursday, but still expecting 90F+
in most areas. Blended ER Superblend with MAV/MET for temps.

A weak trough in advance of the low crossing the Great Lakes
Thursday provides slightly more forcing than today. Will add
low chances for late afternoon/evening thunderstorms.

Friday looks to have a good chance of showers and thunderstorms
as a cold front drops through the region right about peak
heating. Models CAPES are around 1000-1500 j/kg but only 20 kts
of 0-6km shear, so expecting mainly non-severe day and evening.


Ridging aloft will persist over the area as high pressure wedges in
from the northeast at the surface Saturday. The cold front that is
forecast to cross the area from north to south at the end of the
week will stall near the VA/NC border during this time, then return
slowly north as a warm front by late Sunday. A broken overcast is
likely over the weekend with easterly flow off the ocean. This will
result in cooler temperatures closer to normal for this time of year
(highs in the 70s, lows in the 50s). Despite the clouds,
precipitation chances should be minimal over the weekend.

Models continue to oscillate with regards to the timing of frontal
passage on Monday. This front will bring the next chance of showers
and possibly thunderstorms, but convective potential will rely
heavily 1) on the exact timing of frontal passage, and 2) the amount
of cloud cover/cloud debris from prior day`s convection over the
Midwest. Moisture and shear both increase along/ahead of the cold
front/shortwave driving it so storms that do develop will have the
potential for organization if there is enough instability present.

Behind the front, a slightly cooler/noticeably drier airmass will
move in for later Tuesday into Wednesday of next week.


VFR conds continue through Thursday. Low chances for
thunderstorms across the DC metros Thursday evening as a weak
trough crosses.

Chances for thunderstorms Friday as a cold front crosses from
the north late.

Sub-VFR psbl at times over the weekend w/ lower CIGS in
moist ELY flow 10-15 kts.


South winds generally 10 to 15 knots. Shrank SCA to southern MD
waters where a few 18kt gusts have occurred. Midnight shift
will continue to monitor and make adjustments as necessary.

Southerly flow continues Thursday with more channeling
possibility Thursday evening.

Cold front pushes south through the waters late Friday. SCA
possible Friday night.

Small Craft Advisory conditions may continue for portions of
the waters over the weekend in easterly flow between high pressure
to the north and a stalled front to the south.


Near record heat is expected to continue through Thursday. Below are the
highs for today and record high temps for Thursday, May 18.

Today`s (5/17) High and Record Highs:
DCA: Today: 91F. Record remains 92 in 1974, 1896 and 1877
BWI: Today: 93F. Ties record with 1896
IAD: Today: 92F. Beats former record 89 in 1986

Thursday (05/18) Record Warm Lows:
DCA: 72 in 2015
BWI: 68 in 1900 and 1896
IAD: 68 in 2015

Thursday (05/18) Record Highs:
DCA: 96 in 1877
BWI: 97 in 1962
IAD: 91 in 1987


MARINE...Small Craft Advisory until 10 AM EDT Thursday for ANZ533-534-


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