Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 081853

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
253 PM EDT Sat Aug 8 2020

High pressure will build across the region over the next few
days. A cold front will approach from the northwest next week,
stalling in the area as the week progresses.


Isolated showers are develop along the southern Blue Ridge
Mountain near the stalled front. Additional showers and perhaps
a thunderstorm could develop over central Virginia late this
afternoon with additional daytime heating and instability. There
is a Marginal Risk for flooding rainfall from these showers and
thunderstorms due to the slow movement. High temperatures were
knocked down a couple of degrees as morning and midday cloud
cover played a big role in the lack of expected warmth.

High pressure will build into our region tonight. A few showers
could linger over our southeastern zones but should diminish
overnight. Low temperatures for tonight will be in the 60s and
low 70s.


High pressure will build overhead Sunday as the pattern remains
a zonal flow aloft. Conditions should remain dry in most areas
on Sunday, with maybe an isolated shower developing due to
terrain circulation over central Virginia. Dry conditions will
remain into Sunday night. High temperatures will be in the upper
80s and low 90s, with the highest heat index values reaching
into the mid 90s.

Weak high pressure will remain in control on Monday but a
shortwave trough aloft and southerly flow advecting moisture
into our region, could allow for the development of a few
isolated showers and thunderstorms. Heat index values could
reach the upper 90s over most areas across our CWA.


High pressure will remain over the Atlantic Ocean for Tuesday
and Wednesday, and a light southerly flow will allow for more hot
and humid conditions. The heat and humidity will likely lead to
isolated/scattered showers and thunderstorms each day, especially
during the afternoon and evening hours.

A cutoff low may develop to our west for Thursday through Sunday
while high pressure builds over New England, sending a backdoor
boundary toward the area. The exact details are uncertain this far
out, but with a boundary nearby combined with a possible easterly
component from the Atlantic along with more humid conditions. This
will provide a setup for unsettled conditions with showers and
thunderstorms possibly being more widespread. Locally heavy rainfall
is possible during this time. Again, confidence remains low this far


MVFR cigs remain near IAD for low clouds and CHO terminal for
low clouds and developing showers, while VFR conditions exist
at other terminals. VFR conditions at all terminals this
evening will shift to an MVFR low clouds and low visibility set
up due to low clouds and patchy fog again tonight and then again
Sunday night.

Patchy low clouds and fog are possible during the overnight and
early morning hours each day Tuesday through Thursday due to plenty
of moisture in place, and the possibility of it getting trapped
underneath the nocturnal inversion.

A few afternoon and evening showers and thunderstorms are possible
each day. Coverage may be more widespread Thursday as a boundary
interacts with the area.


Winds are expected to remain below Small Craft Advisory criteria
into Monday night. Some convection could bring gusty winds this
afternoon over the southern portion of the Bay, and lower Tidal
Potomac. This should improve tonight. There will be less chance
for any convection Sunday into Sunday night, a slight chance
for Monday afternoon/evening.

High pressure will remain over the Atlantic Tuesday through
Thursday, providing a southerly flow. Winds should remain below SCA
criteria for most of the time since the flow will be light. A few
afternoon/evening showers and thunderstorms are possible Tuesday and
Wednesday. There is a chance that convection may be more widespread
Thursday afternoon/evening as a boundary from the north and east


Elevated water levels will persist over the next few days. The flow
will be light, so the most likely scenario is that sensitive areas
will be around action stage.




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