SPC MD 1448


MD 1448 Image

Mesoscale Discussion 1448
NWS Storm Prediction Center Norman OK
0918 PM CDT Fri Jul 12 2019

Areas affected...parts of western into southern North Dakota

Concerning...Severe potential...Watch unlikely 

Valid 130218Z - 130345Z

Probability of Watch Issuance...20 percent

SUMMARY...A slight increase in storm coverage/intensity may occur
over the next few hours, with large hail and damaging wind gusts
being the main threat. The severe threat is expected to be isolated
enough to preclude a WW issuance.

DISCUSSION...A supercell thunderstorm is ongoing across Mountrail
County, ND, and is moving southeast along a weak instability
gradient. This storm is accompanied by a modest surface cold pool
that continues to surge southward in an ambient environment
characterized by 1000-1500 J/kg MLCAPE and 60+ knots of effective
bulk shear. This supercell/cold pool is approaching a diffuse
confluence zone, extending along an east-west axis, from roughly
K2OU to BIS. Here, both low-level directional shear and deep-layer
speed shear are in place, with up to 300 m2/s2 effective SRH present
(as indicated by the most recent mesoanalysis and RAP forecast
soundings). Convection is already gradually increasing in
coverage/intensity along the aforementioned confluence zone, and
when the supercell and associated cold pool in northwest ND
interacts with the confluence zone, additional storm coverage and
associated intensification may be possible. Given the ample
deep-layer shear and modest directional shear in place, sustained
updrafts with deep (i.e. sustained mid-level and occasional
low-level) rotation will be possible. 

Large hail and damaging winds will be the primary threats for the
most intense cells. While a brief tornado cannot be completely ruled
out, a gradually stabilizing boundary layer will likely limit more
robust mesocyclone development/tornado threat. Boundary layer
stabilization will also likely play a role in tempering the overall
severe threat this evening, and given the expected brevity/localized
nature of the severe threat, a WW issuance is not anticipated at
this time.

..Squitieri/Hart.. 07/13/2019

...Please see www.spc.noaa.gov for graphic product...


LAT...LON   46550259 46970338 47680363 48190354 48470294 48490205
            48280121 47830050 47149981 46599957 46329978 46210113
            46280213 46550259 

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