Scientific Forecaster Discussion
fxus61 klwx 181915
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
315 PM EDT sun Aug 18 2019
a weak surface boundary will remain over the area through the
middle of the week. Southerly flow will bring hot and humid air
into the region during this time. A cold front will sweep
through the area during the second half of the week, with high
pressure following for next weekend.
Near term /through Monday/...
as expected, isolated to scattered thunderstorms have developed
this afternoon. One in particular got caught and backbuilt over
Baltimore City, dropping two inches of rain, dime size hail,
and gusty winds of at least 30 mph.
With little in the way of synoptic forcing, the existing outflow
boundaries from ongoing convection, and terrain, will be the
primary drivers of convective initiation through the early
evening hours. Some of these storms will likely be as robust as
the one in Baltimore -- perhaps even stronger.
Overnight tonight, model guidance shows more fog than this
morning but not as much as Saturday morning. Have indicated that
in the forecast. Otherwise, the ongoing convection should end
with sunset, and guidance has backed off on the idea of
overnight showers...for now.
We will rinse and repeat this for Monday, most likely with
temperatures a degree or two hotter than today. This will put
heat index values very close to heat advisory criteria in the
eastern half or so of the forecast area. Due to ongoing storms,
will pass the advisory decision on to later shifts.
There should not be as much in the way of showers and storms on
Monday, but isolated activity -- perhaps with strong gusty winds
-- is still on The Table.
Short term /Monday night through Tuesday night/...
the only thing likely to hold Tuesday back from the extreme heat
will be increased cloud/storm coverage in the afternoon, before
it has a chance to get as hot or hotter than Monday. A heat
advisory could still be required. Things start to change
Tuesday as a stronger, deeper shortwave approaches, not to
mention a cold front from the Northwest. Cape remains plentiful
Tuesday and pw's near 2 inches. Thus, decided it was prudent to
insert a mention for severe weather and flooding into the severe weather potential statement
for this day, given the higher potential compared to prior days.
The Storm Prediction Center has also placed US in a marginal risk for severe
Long term /Wednesday through Saturday/...
a surface trof will be in place Wednesday while temperatures remain
hot in the middle 90s. A downward trend in convection is indicated
by model guidance. Substantial height falls are indicated on
Thursday as mid-upper level trof crosses the eastern great lks to
northern New England with the GFS being much more amplified with
this trof than the European model (ecmwf). Nevertheless, anticipating Thu we'll see
decent convective cvrg. Some drying will begin to take place Thu
night as front crosses the area, but expecting showers to linger
into Fri across the southern areas as front will be slow to clear
area. Dry conditions are likely for the weekend at least for
northern areas, although central Virginia and far southern areas could
still see chances of showers prevail as front stalls across southern
Aviation /19z Sunday through Friday/...
VFR expected through the valid taf period except in pop-up
showers and storms...which today seem to be popping up right
near the terminals. When those storms occur, lowered visibility
and gusty winds are possible.
This will repeat Monday afternoon but with less storm coverage
expected. Better chance again on Tuesday and Wednesday.
Enhanced risk of T-storms Thursday with passage of cold front.
models have backed off on the potential for southerly channeling
this evening that would reach Small Craft Advisory gust
criteria. But it will remain close and we will monitor.
Gusty winds possible in storms over the waters this afternoon
and early evening; same story Monday and Tuesday. Otherwise
light winds though with high pressure in control after today.
Small Craft Advisory conditions possible Wed and Thu as gradient tightens. Smws
may be required Thu.
District of Columbia...none.