SPC MD 1518


MD 1518 Image

Mesoscale Discussion 1518
NWS Storm Prediction Center Norman OK
0224 PM CDT Mon Aug 17 2020

Areas affected...Portions of central and eastern Oregon

Concerning...Severe potential...Watch possible 

Valid 171924Z - 172130Z

Probability of Watch Issuance...40 percent

SUMMARY...With mid-level ascent increasing across northern
California and southern Oregon, widely-scattered to scattered storms
are expected in central/eastern Oregon this afternoon. Storms will
pose a threat for damaging wind gusts. Lack of greater buoyancy and
some question on storm coverage reduces confidence in WW issuance.
Trends are being monitored.

DISCUSSION...Mid-level ascent is increasing across northern
California and south-central Oregon. The leading and weaker edge of
this ascent is across south-central Oregon and will continue
north-northeastward this afternoon. Stronger ascent lags southward
just north of the Bay Area. While this leading area of cloud cover
creates some uncertainty as to where the strongest storms will
develop, areas downstream of this ascent have already warmed into
the low 90s F. Even if storms may initially be elevated, continued
boundary layer mixing should lead to surface-based storms by 3 PM
PDT. Storm intensity will be mitigated by fairly weak buoyancy with
only 250-500 J/kg MLCAPE expected. Despite this, 30-40 kts of
effective shear and a deep, dry boundary layer should allow a few
organized storms to transport some of the 40-50 kt cloud-bearing
flow to the surface. As such, widely-scattered to scattered storms
will pose some risk for damaging wind gusts. Lingering uncertainty
with regard to storm intensity and coverage reduces confidence in
the need for a WW. Trends will continue to be monitored over the
next few hours.

..Wendt/Grams.. 08/17/2020

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


LAT...LON   43221811 42811855 42821954 43122020 43632053 44801967
            45651835 45491730 44641709 43221811 

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