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2022 Mid-Atlantic Severe Wx Thread (General Discussion Etc)


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Hmmm... sneaky severe tomorrow?

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...


As the initial front continues to sag on Friday, it will likely
start to be pushed along by a stronger cold front later Friday
into Saturday. Showers and a few rumbles of thunder are
possible both Friday and Saturday afternoons and evenings. Given
some of the recent rainfall totals in the early 12z guidance
late Friday into Saturday morning, flooding is starting to
become a real concern. There is still a lot of uncertainty with
exactly what happens though given ongoing MCS`s potentially
moving into the area or nearby. Lots of moving parts to take
into account. Some guidance even brings in a remnant MCV into
the region and tries to spin up a low along the stalled frontal
boundary. Guidance is really struggling to pick up on much
instability obviously given the time of day, but should this
occur at the right time (perhaps even into the day Saturday), we
could be looking at an isolated severe threat as well. Again,
lots of uncertainty here, but some guidance has a conditional
tornado threat on Saturday should that above scenario play out,
so it is something we are watching. For now, now outlook from
SPC, but may have to revisit that with the overnight update
should that trend continue. For now though, given the
antecedent conditions coupled with any slower moving, training
showers and thunderstorms, flooding/flash flooding appears to be
the primary concern. This is highlighted by WPC`s Excessive
outlooks in the D2 and D3 periods. May be looking to collaborate
some changes there if the 12z guidance continues to come in
bullish on precipitation amounts. Hoping for some more details
with the afternoon package, but keep an eye on the forecast for
any significant changes.
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Afternoon disco from LWX about the threat 

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Confidence is increasing in a potentially high impact heavy
rainfall event Friday night into Saturday morning. A slow-moving
cold front remains situated over the region, meanwhile a
reinforcing cold front will be pushing in from the NW.
Additionally, a potent shortwave will be sliding by overhead
during the Friday night into Saturday timeframe. This results in
almost all guidance developing a low either overhead or very
closeby. There will also be an abundance of low-level
convergence given the two frontal boundaries colliding as well.
Almost all guidance dumps heavy rainfall over some portion of
our region especially after midnight on Saturday morning. The
question still remains as to exactly where this occurs. A lot of
the uncertainty is related to exactly how the system evolves to
our northwest. Flash flooding will certainly be a concern,
especially given the antecedent conditions as a result of the
heavy rainfall over the past several days in different parts of
the region. The QPF forecast has come up greatly, and it is
anticipated that our ERO category from WPC will likely expand
and/or increase in coverage with the afternoon update.

In addition to the flooding rainfall threat, starting to grow a
bit more concerned with the severe thunderstorm threat as well.
Timing will be key with this system, and if it comes through a
bit slower into Saturday, could even have some decent CAPE to
work with. The environment will be very well-sheared with the
frontal boundaries nearby and decent upper-level support. Most
concerned with a few damaging wind gusts, and perhaps even an
isolated tornado along the boundary itself.

The majority of the rainfall should be to our south by Saturday
afternoon as the front marches south. However, given the
remaining uncertainties, going to keep some chance POPs in the
forecast for now as things can and likely will change to some
degree.
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Yea some of the CAMs are really starting to hit in on the 4"+ mark for spots. If that happens, especially in the metro areas, that's going to be a problem.

EDIT: Even the Euro has a stripe of 3" - 5" from DC up through Baltimore and over to the eastern shore.

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8 minutes ago, Eskimo Joe said:

Yea some of the CAMs are really starting to hit in on the 4"+ mark for spots. If that happens, especially in the metro areas, that's going to be a problem.

EDIT: Even the Euro has a stripe of 3" - 5" from DC up through Baltimore and over to the eastern shore.

Particularly if the jackpots are in areas that have recently been deluged. 

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8 minutes ago, southmdwatcher said:

3 to 5 inch plus jackpots along Sligo Creek and the Little Patuxent River would be problematic

Sligo Creek flashes quickly, but it also goes down fast. The USGS gauge in Takoma Park shows we're down to baseline.

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