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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
927 PM EDT Monday Jul 6 2015

a weak low pressure system and warm front will lift northeast out
of the area tonight. High pressure will dominate Tuesday. A cold
front will move in from the Great Lakes on Wednesday. The front
will slide slowly south across the area Thursday and Friday before
slowly moving back north over the weekend.


Near term /through Tuesday/...
it took a while to get together...but a line of storms just west of
the Bay at this time. Weak shear and poor middle level lapse rates precluded
severe potl. But precipitable water near 1.75 inches led to heavy rainers. Several of
these storms training...which is what has prompted flash flood

Based on current extrapolation...storms should clear County warning forecast area between 02-03
UTC. With loss of daytime heating/resulting not
forsee much rdvlpmnt. Could see lingering showers through the night
as the trough pivots to the east and north. Do plan on retooling
pop grids for the overnight period...cutting back on precipitation chances. However...wet
grnd and prtl clearing may lead to areas of fog. Would not rule out local
dense fog...but dont have high confidence in it either. Will let areas
cover it for now.

Tuesday looks to be relatively dry as the upper level trough pushes
to the north. Precipitation possible over the northeastern corners of the County Warning Area
where the southern edge of the trough will hover through most of the
day. At the surface...low pressure trekking through the Great Lakes will
drag the associated cold front near the region...reaching the
western areas overnight Tuesday. Chance of precipitation will accompany the


Short term /Tuesday night through Wednesday night/...
high pressure slides east to our south Tuesday night as cold front
approaches from the northwest. The front will cross into the County Warning Area
by Wednesday night. Clouds will start to increase Tuesday night but
think most showers or storms hold off until during the day
Wednesday. Main issue Wednesday are some timing differences with
the front. The slower guidance keeps the storms away early on and
allows temperatures to spike into the 90s...while faster modeling brings
storms in early on Wednesday and keeps temperatures down in the 80s.
Either way...storms should diminish or move away Wednesday night
with modestly cooler temperatures and lower dew points.


Long term /Thursday through Monday/...
frontal boundary will linger around the region Thursday into Friday.
Upper level disturbances will impact the County Warning Area on the weekend and
into next week. Isolated/scattered showers and/or thunderstorms are possible
each day. Temperatures will be near normal for this time of the year.


Aviation /01z Tuesday through Saturday/...
thunderstorms and rain impacts at BWI/mountain at this time. Most likely threat for the rest of the
terminals has ended. Humid air and wet grnd does lead to a
predawn fog threat. At this time have limited to MVFR iad/cho/mrb.
If skies remain mostly clear...IFR well within reason.

Any morning fog will burn off during the morning push. Rest of the day
should be VFR. While thunderstorms and rain threat not zero...its very low...and was
not mentioned in tafs.

Main concern Wednesday/Wednesday night has to do with approaching
cold front. Thunderstorms look likely...with a few periods of sub-
VFR ceilings/visible and perhaps a few strong wind gusts mixed in with
otherwise VFR conditions. Timing is still in question however.
Winds shifting from southwest early to northwest by Wednesday
night...possibly some non-storm gusts into the 20 knot range.

VFR conditions expected for Thursday night and Friday. Sub-VFR conditions
possible due to showers and/or thunderstorms.


winds have been sustained 15 knots or less thus far tonight. However...setup
conducive for southerly chanelling. Small Craft Advisory remains in effect through tonight
with gusts up to 20 kts possible. Mainly sub- Small Craft Advisory conditions on
Tuesday...though occasional gust up to 20 kts may be possible on the Chesapeake
Bay. Winds are too marginal at this time to up another Small Craft Advisory.

Main concern Wednesday/Wednesday night has to do with approaching
cold front. Winds will pick up ahead of the front with gusts
possibly reaching Small Craft Advisory levels. In addition...thunderstorms look
likely...with some stronger gusts and heavy rain et cetera. Timing is
still in question however. Winds shifting from southwest early to
northwest by Wednesday night.

Sub-Small Craft Advisory conditions expected for Thursday night and Friday. Possible showers
and thunderstorms across the waters during this period.


Tides/coastal flooding...
water levels running about 1/2 to 3/4 feet above normal. The lower of the two
astro tides appchg tonight. While this evngs tides have reached caution
stage in a cpl of problems obsvd or expeceted.

While the tide will be higher tmrw morning...we may be able to evacuate a
bit of the current slug of water. Therefore...forecasts keep all
levels below minor flood thresholds. Will need to monitor current levels
to ensure that indeed is what happens.


Lwx watches/warnings/advisories...
District of Columbia...none.
Marine...Small Craft Advisory until 8 am EDT Tuesday for anz533-534-537-


near term...hts/Sears
short term...rcm
long term...imr
tides/coastal flooding...heights

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