Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
953 am EDT Tuesday Aug 4 2015
a cold front will continue to gradually shift southeast through
the area today. High pressure will build into the area later
tonight through Wednesday. The boundary will return north as a
warm front and stall out over the area for Thursday and Friday.
Low pressure will ride along the boundary...passing through the
region Thursday night and Friday. High pressure will gradually
build in behind the low next weekend.
Near term /through tonight/...
a weak cold front is stretched across the middle-Atlantic from phi to
cho. The region is recovering from the storms early this morning
and instability is on the rise. The frontal boundary is expected
to sharpen and move eastward by this afternoon. Winds should veer
to the northwest behind the front mainly west of the Blue Ridge advecting
in drier conditions. Along and east of the front...instability
will continue to rise as temperatures reach the low 90s and dewpoints reach
the middle to upper 60s. Showers and thunderstorms are expected to
form along the front and track eastward this afternoon.
Per the 12z iad radiosonde observation...little inhibition exists this morning and
after modifying the sounding for southern Maryland... where instability
is forecast to be higher...near 3k j/kg of MLCAPE is possible.
Bulk shear values of 35-45 kts are expected today while the jet
stream moves into the middle- Atlantic. This features will likely
enhance the threat of strong to severe thunderstorms. There is
some wiggle room where the cold front sets up early this
afternoon. Areas along and east of I-95 including the waters have
the potential of strong to severe thunderstorms late this afternoon
and into the early evening.
The boundary will continue to slide south tonight and high
pressure will build overhead...causing dry and comfortable
Short term /Wednesday through Thursday/...
high pressure will remain in control for Wednesday through
Wednesday night while the cold front stalls to our south. A west
to northwest flow will usher in dry and cooler conditions during
this time. Although...maximum temperatures Wednesday will still be near
climatology due to sunshine and a downsloping flow.
The boundary will return north as a warm front Thursday and it
will stall out overhead late in the day. Low pressure will ride
along the boundary and approach from the west late in the day.
Clouds will increase and there is a chance for showers and
isolated thunderstorms...especially during the afternoon hours.
Timing is still a little uncertain as of now due to divergence
with the guidance.
Long term /Thursday night through Monday/...
the wave of low pressure will pass through the area Thursday night
into Friday...and another one may ride along the boundary and pass
through later Friday into Saturday. This will bring a better
chance for showers and possible thunderstorms.
As the second wave of low pressure departs...the boundary will
slide to the south and high pressure may return later in the
weekend into early next week.
Aviation /14z Tuesday through Saturday/...
a cold front will pass through the terminals today and a few
thunderstorms are possible during the afternoon and evening
hours...mainly across the eastern terminals.
High pressure will bring VFR conditions tonight through Wednesday
night. Northwest winds may gust around 15 to 20 knots Wednesday
afternoon. The cold front will return as a warm front for Thursday
through Saturday. Waves of low pressure will ride along the
boundary...increasing the chances for showers and possible
thunderstorms. Subvfr conditions are likely during this time.
a cold front will pass through the waters later this afternoon
and evening. A few thunderstorms are possible...and gusty
winds/hail are possible in the stronger storms. High pressure will
build over the waters later tonight through Wednesday night as the
boundary stalls to our south. A Small Craft Advisory is in effect
for middle portions of the Bay and lower tidal Potomac through
this evening. Winds may approach also Small Craft Advisory criteria Wednesday.
The boundary will return north as a warm front for Thursday
through Saturday and it will stall out overhead during this time.
Waves of low pressure will ride along the boundary...increasing
the chances for showers and thunderstorms.
a south to southwest flow has caused anomalies to increase to
between one quarter and one half foot above normal.
However...water levels are expected to remain below minor flooding
District of Columbia...none.
Marine...Small Craft Advisory until noon EDT today for anz532-533-
Small Craft Advisory until midnight EDT tonight for anz534-537-