Scientific Forecaster Discussion
fxus61 klwx 221852 cca
Area forecast discussion...corrected
National Weather Service Baltimore Maryland/Washington District of Columbia
252 PM EDT Tue Aug 22 2017
High pressure is centered well off the North Carolina coast. A
cold front over western Ohio will track across the mid-
Atlantic tonight into Wednesday morning. Reinforcing upper level
energy will help to push the front offshore and allow for high
pressure to build in from the northwest Thursday into Friday.
Near term /tonight/...
Temperatures in the lower 90s and dewpoints in the low 70s have
led to another day with CAPES of 1000-2000. It is a different
synoptic situation from yesterday as we have our eyes on a
front/line of storms stretching from Ontario to southern Illinois.
Watches are in effect to our west and north. Aside from any
isolated cells that fire ahead of the line the main possibility
of convection looks to be from around 9 PM over the mountains to
after midnight by the Bay. Models have consistent in weakening
the cells once these move east of the Blue Ridge. Yes heating
will be over/cape will be diminishing but think given the
amount of energy in the atmosphere still believe severe storms
could be possible through midnight.
Storms should weaken after midnight with pops decreasing from northwest
Lows in the mid to upper 60s west of the mountains...low to mid
Short term /Wednesday through Thursday night/...
Showers/isolated thunderstorms will be possible across the
southern 2/3 of the forecast area Wednesday. By Wednesday
precipitation should be well offshore. Tonight's fropa will
bring an end to this recent heat wave. Highs Wednesday back
into the mid 80s/dewpoints beack into 60s. Conditions will
continue to become more comfortable Wednesday night and
Long term /Friday through Monday/...
The long term period looks fairly dry with surface high
pressure dominating the weather conditions over our area. Some
diurnally or terrain driven showers and thunderstorms could
develop at times with shortwaves moving through, but at this
moment looking at mostly dry weather conditions. Temperatures
will be slightly below normal, with highs around 80 degrees,
near 70 at higher elevations.
Aviation /18z Tuesday through Sunday/...
The concern is the cold front across the Ohio Valley. While the
strongest activity is expected to be to our north showers and
thunderstorms could reduce visibilities to IFR in heavy rainfall
VFR conditions expected at all terminals after midnight through
Mainly VFR conditions expected Friday into Sunday with high
pressure building over our area.
Small craft advisories in effect through 11 PM tonight.
Thunderstorms are expected to be weakening tonight by the time
these reach the waters but smw wind gusts may still be possible.
No marine hazards expected Wednesday through Thursday night.
Wind gusts are expected to stay below the Small Craft Advisory
Anomalies are around 0.5 to 0.6 ft this afternoon. The coming high
tide is lower astronomically and no flooding is expected. Then
northwest winds will arrive Wednesday morning. We will have to see
if that will be soon enough to preclude another borderline situation
at Annapolis, Straits Point, and District of Columbia early Wednesday.
District of Columbia...none.
Marine...Small Craft Advisory until 11 PM EDT this evening for