Mesoscale Discussion 1520
NWS Storm Prediction Center Norman OK
0627 PM CDT Mon Aug 17 2020
Areas affected...Northeast Oregon...far southeast Washington...and
western Idaho
Concerning...Severe Thunderstorm Watch 446...
Valid 172327Z - 180100Z
The severe weather threat for Severe Thunderstorm Watch 446
continues.
SUMMARY...The severe weather threat continues across severe
thunderstorm watch 446. Severe wind gusts are the primary hazard.
DISCUSSION...Several severe wind gusts were reported earlier this
afternoon in Harney county, but no severe wind has been measured
since. However, the loosely organized cluster of storms in eastern
Oregon is moving into a more favorable airmass in northeast Oregon
in the next 1 to 2 hours. Temperatures ahead of this activity are
around 100F with dewpoints around 50F. This is yielding MLCAPE
around 250 J/kg with mid-level moisture supporting MUCAPE above 500
J/kg. Therefore, these storms are likely a combination of surface
based and elevated at this time. Instability is the primary limiting
factor at this time, but if storms can continue to grow upscale and
organize, severe winds are likely given the moderate to strong lower
tropospheric flow and very steep low-level lapse rates per SPC
mesoanalysis.
While this portion of northeast Oregon may pose the greatest severe
threat over the next few hours, an additional, more isolated severe
threat will also persist farther west. A multicell cluster of storms
has formed near Madras, OR in an area with poor radar coverage,
however, lightning and satellite trends suggest a strong-well
organized updraft. Low to mid-level moisture is higher in this area
yielding MLCAPE around 500 J/kg and MUCAPE around 1000 J/kg, and
mid-level flow is somewhat stronger. Storm coverage may remain more
isolated in this area, but any sustained updrafts may pose a threat
for severe winds.
..Bentley.. 08/17/2020
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MSO...BOI...OTX...PDT...
LAT...LON 44412157 45482095 46061945 46411764 46641611 46591540
46101519 45261555 44541618 43801654 43431692 43451734
43621775 43961826 44071879 44141937 44412157
Read morefrom SPC Forecast Products http://www.spc.noaa.gov/products/md/md1520.html
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