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2018 Mid-Atlantic General Severe Discussion


Kmlwx

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I'm definitely no expert but I would think that with some "okay" looking inverted-v profiles and fairly swift cloud layer motion any storms that do manage to pop may bring down some stronger wind gusts......Any storms that do manage to pop. The obvious limiting factor today is CAPE.

hrrr_2018050414_007_39.0--77.37.png

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The CAM signals for later today are inconsistent, but some do get some decent cells into our area.    As noted above, the profiles may support some damaging wind threat.    But wow, check out the shear profiles up in VT for later today - remarkable.    If they had a little more instability, it would be a MDT risk day.     When northern New England gets into the SVR threat before our area does, it's time to wave the white flag.

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LWX AFD from this morning... probably a meh for Thursday afternoon, but still:

Quote

Surface dew points should rebound to near 60 F during the
afternoon on southerly return flow, especially near and west of
the Blue Ridge. This couple with modestly steepening mid-level
lapse rates around 6 C/km in association with the approaching
500 hPa shortwave yields CAPE values between 750-1500 J/kg
(lower to the east where warm/moist return flow commences a few
hours later). Modest shear for storm organization appears
possible as well given 40-50 kts of mid-level flow. There may be
at least a marginal risk for a few strong to severe
thunderstorms with gusty winds being the main threat, if the
current forecast holds. Early morning stratus or patchy fog is
indicated by some guidance, and that coupled with broken mid
level clouds expected much of the day would hamper instability
some, so especially given that this is a day 4 forecast, there
remains considerable uncertainty.
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From SPC Day 4- 8 OTLK

For Saturday, the medium-range
   models develop an upper-level ridge in the central Plains and show
   zonal mid-level flow across the eastern third of the U.S. A severe
   threat would be possible with thunderstorms that can develop
   Saturday afternoon along a front. The front is forecast to be
   located from the mid Missouri Valley into the southern Great Lakes
   region. The ECMWF, GFS and FV3 move this front southward into the
   central Plains and mid Mississippi Valley on Sunday but show the
   upper-level ridge across the central states. If thunderstorms can
   develop further east along the front from the Ohio Valley into the
   Mid-Atlantic Sunday afternoon, then a severe threat would be
   possible. Overall, confidence in the models from Friday to Sunday
   concerning the exact location of the front and instability is too
   small to add a 15 percent contour.

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LWX morning disco re Thursday severe risk:

Quote

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Mid-upper level ridging will build over the area Wed on
backside of departing mid-upper level closed low while sfc
ridging remains in place. This will support dry conditions Wed
into Wed evening. Some lingering low level moisture could touch
a stray shower over the highest terrain in the PM, but it should
be very isolated.

Southerly flow begins to strengthen late Wed night ahead of
shortwave trough moving across the eastern Great Lks Thu.
Showers are expected to overspread the area Thu morning well
ahead of the front with nmrs-widespread showers and scattered
t-storms expected Thu afternoon into early evening as cdfnt
crosses the area. 0-6 km shear of 40 kt, moderate instability,
and steep low-mid level lapse rates suggest a risk of some
severe t-storms with damaging winds and large hail the primary
threats. SPC Day 3 Outlook has area along and west of the Blue
Ridge under a marginal risk of severe wx. Cdfnt clears the area
late in the afternoon or early in the evening with svr threat
ending by 8PM Thu although showers could linger a little longer.
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Oh come on... LWX afternoon AFD re Thursday potential:

Thursday we continue to watch any severe weather threat.
However, its notable that with the potential for weakening
showers to limit insolation during the morning, and then dry air
aloft becoming dominant later in the afternoon, plus dominant
westerly flow aloft, its possible much of our CWA ends up
missing out on significant convection. That said, CAPE and shear
could both potentially be fairly signficant, and SPC has placed
western portions of the CWA in a marginal risk. Warm advection
ahead of the front should allow most spots to rise into the 80s
on a gusty southwest breeze.

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14 minutes ago, Kmlwx said:

This sounding is from the 3km NAM in Central Maryland during the later afternoon (20z) on Thursday. I could draw up worse soundings. Lots of results in SARS too. 

2018050818_NAMNST_050_39.16,-77.03_severe_ml.png

I like all the SIG in the Supercell portion of the SARS

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12z NAM NEST sim radar decent... drives in some crappy showers around 15z... then blows up storms over us around 20z to 21z... has what looks to be maybe a sup in C MD at 22z... then drives one more small line or cell through DC around 02z

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3 minutes ago, Kmlwx said:

Tuesday is even better :lol: - of course I'm getting on a flight Tue morning at 7am to Florida. 

Incoming derecho that evening :lol:

That's exactly how I missed the last derecho -- traveling to FL that morning for vacation with family

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3 minutes ago, yoda said:

Incoming derecho that evening :lol:

That's exactly how I missed the last derecho -- traveling to FL that morning for vacation with family

The only way I'd be okay with that is if I got tropical action down south. 

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