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Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
405 am EDT sun Jun 25 2017

Synopsis...
high pressure to the west will remain in overall control through
Tuesday, but a series of weak cold fronts will be crossing the
region during this time. The high will then cross the region
Wednesday and settle over the western Atlantic Ocean late in the
week.

&&

Near term /through tonight/...
one cold front sits off to our southeast at present while
several more are located to our northwest. One of them will
cross the region late today into this evening, but with little
forcing aloft and limited moisture, no precip is expected. It
will simply bring a reinforcing shot of cooler and drier air
southward, with otherwise partly to mostly sunny skies
prevailing today and remaining clear to partly cloudy tonight.
Highs will be in the low to mid 80s with dew points in the
50s...quite nice for late June. Lows tonight will be mostly in
the 50s except 60s in the cities and along the Bay Shore.

&&

Short term /Monday through Tuesday night/...
another reinforcing shot of cooler air pushes south across the
area late Monday into Monday night. Forcing remains weak and
moisture remains limited so think precip will be hard to come
by. Clouds may be a bit more common though. Highs will slip down a
bit more with upper 70s to low 80s common. Dew points will slip into
the upper 40s during part of the day. Lows Monday night will drop
back into the 50s most spots, but still 60s in the warmest locales.

Strong upper trough will cross the region Tuesday with another
surface boundary. This trough is probably the most interesting
weather through the forecast period, with increased instability
associated with it. Some guidance is still dry with it (the
Canadian suite), but others, including the NAM and ECMWF, are
rather convective, so we could definitely see some scattered
showers and thunderstorms given the cold pool aloft and decent
positive vorticity advection. For now have kept probability of precipitation rather low east of the mountains,
but may need to be bumped if guidance comes into better
agreement. Highs Tuesday will be quite cool, with most places
failing to reach 80. Dew points will be slightly higher, with
most places staying in the 50s. Clearing Tuesday night behind
the trough, with lows into the 50s in most places, except near
60 in the cities and Bay Shore and 40s in the mountains.

&&

Long term /Wednesday through Saturday/...
the upper level trough axis shifts east of the mid-Atlantic
Tuesday night per global guidance consensus. The trailing
surface low will then be overhead Wednesday before shifting
offshore later that day. The streak of below normal temperatures
end Thursday with the return southerly flow that begins
Wednesday night.

The high becomes centered over Bermuda with a return to Summer-
like conditions (max temps around 90f) Thursday into the
weekend. The jet stream and associated low pressure looks to
stay north of the central mid-Atlantic/over the Great Lakes
through the weekend with continued low chance probabilities for
precipitation.

&&

Aviation /08z Sunday through Thursday/...
VFR through the period with winds generally below 18 knots.
Main concern will be an isolated shower or thunderstorm on
Tuesday. Otherwise, no significant winds, precipitation,
visibility or ceiling limitations expected.

&&

Marine...
winds below Small Craft Advisory criteria currently, but with deeper mixing and
another weak boundary passing through, expect some gusts to
marginal Small Craft Advisory levels later today. Therefore have maintained Small Craft Advisory
as inherited. Considered adding upper tidal Potomac but
confidence still not there for gusts this afternoon. It will be
close, however.

There is concern again for marginal Small Craft Advisory on Monday with another
weak boundary and good mixing, but given marginal event
expected, did not raise headlines yet.

On Tuesday, a passing trough may cause spotty showers and
thunderstorms, and given dry environment overall, some gusty
winds could accompany them.

Tranquil and cool weather Wednesday under surface high
pressure. Return southerly flow begins Wednesday night as the
high shifts to Bermuda.

&&

Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...none.
Virginia...none.
WV...none.
Marine...Small Craft Advisory from 1 PM this afternoon to 10 PM EDT
this evening for anz530>532-538>540.

&&

$$
Synopsis...rcm
near term...rcm

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