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August Discobs 2019


George BM
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2 hours ago, H2O said:

No clue what happened back home.  I’ve been down on the slower lower(deep DELMARVA) all week.  Had a nice storm here yesterday

It wasn't as much as people further north got, but still there were sheets of rain at times as the line went through (it was a bit fun to watch the heavy rain continually changing directions because of the wind), and a few instances of flash-bang (including one that happened when the skies had cleared).

(For the edification of others, I live a few miles away from H20)

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2 hours ago, MN Transplant said:

It should.

Interesting. I’d have thought the area around you would be a little less orange.

I’m definitely in that orange pixel south of Fairfax City though. It’s incredibly dry here right now. Lots of wilted shrubs, with a fairly healthy leaf drop, to boot.

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Tuesday continues to look potentially active. Mount Holly's thoughts this morning-

On Tuesday, the aforementioned low pressure, associated with a decaying MCS from the source region, will push a frontal boundary into the forecast area. The exact placement of this boundary will dictate the resulting convective evolution throughout the day Tuesday, nevertheless the environment is likely to be favorable for strong to severe thunderstorms developing during the afternoon. Being that this event will be driven by primarily by mesoscale processes, details are still a bit unclear at this range, however all severe weather modes (including damaging winds, tornadoes, and large hail) will be possible Tuesday afternoon and evening. Deep layer shear is forecast to be in the 35-40 kt range with MLCAPE values of 1000-2000 J/kg. Some guidance has impressive low-level wind shear profiles and low-level curvature to the hodographs for this time of year. Precipitable water values will be high as well (well over 2") so flash flooding will be a threat where the heaviest storms begin to train over the same areas.

 

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@high risk @Kmlwx @Eskimo Joe

LWX seems gung ho for Tuesday severe in their AFD:

Heat and humidity increase further on Tuesday as a strong area
of low pressure and associated cold front approach from the
north, potentially creating a volatile weather situation over
the Mid-Atlantic. 850/925 hPa temperatures approach 20 C/28 C
respectively, which in the presence of full mixing (assuming
little to no cloud cover) would yield surface high temperatures
in the mid to upper 90s. There will likely be some cloud cover
ahead of the approaching front however, especially over
northern Maryland, so currently forecasting upper 80s to near
90 over northern Maryland and eastern West Virginia, and low to
mid 90s for DC/northern and central Virginia. Dew points also
approach 20 C at 925 hPa, further indicating the increasingly
hot, humid and unstable airmass moving into the region. Heat
index values will likely approach 100 degrees near and south of
US-50 Tuesday, unless there`s more appreciable and widespread
cloud cover.

The hot and humid airmass advecting into the region is expected
to encompass a large area, with much of the eastern third of
the CONUS forecast to see 1.75-2+ inch PWATs. So even with
southwesterly low-level flow which often introduces a slight
downsloping/drying component locally, any drying should be
offset by the higher moisture content in the ambient low-level
airmass. Model soundings indicate 1500-2000+ J/kg MLCAPE later
Tuesday afternoon, as well as locally backed surface winds ahead
of a developing surface pressure trough (attendant to 4-5 mb
6-hr pressure falls), enhancing surface convergence and
mesoscale lift. Profiles indicate anomalously strong wind fields
for this time of year, with effective shear of 35-40 kts likely
over the warm sector. This environment could be conducive for
both supercells and bowing line segments, with all severe
threats possible (though damaging wind gusts may prove to be the
primary severe hazard). Flooding could also become a concern
due to steering flow parallel to a slowly southward advancing
cold front in a high PWAT environment.

Exactly when and if convection dwindles Tuesday night remains
unclear, and will be reliant upon small scale convective
evolution Tuesday afternoon not yet resolvable at this time
range. If a more cold pool dominant linear system were to
develop, it may dive southeastward and out of the area more
quickly. But persistent height falls/destabilization argue that
back-building or training storms could develop on the tail end
of any such system. Therefore, the above threats will likely
persist into Tuesday night, but with less coverage and certainty
than Tuesday afternoon and early evening.

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