|Mesoscale Discussion 1218|
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Mesoscale Discussion 1218
NWS Storm Prediction Center Norman OK
0804 PM CDT Sun Jul 02 2017
Areas affected...southwest NE into northwestern KS
Concerning...Severe Thunderstorm Watch 390...
Valid 030104Z - 030200Z
The severe weather threat for Severe Thunderstorm Watch 390
SUMMARY...There appears to be an increasing risk (scattered
coverage) for severe gusts (60-75 mph) as a squall line matures and
intensifies as it moves south into southwestern NE and northwestern
KS during the next several hours.
DISCUSSION...Radar mosaic trends over the past 1-2 hours has shown
cellular storms merging and upscale growth occurring near I-80 in
west-central NE near North Platte. The 00Z LBF raob exhibited steep
lapse rates from the surface through the mid levels (8.3 degrees
C/km in the 850-500 mb layer) with a well-mixed boundary layer
beneath 700 mb. Southeasterly low-level flow veering to westerly in
the mid and high-levels is resulting in around 40-kt effective
shear---supportive of storm organization. A fairly sharp gradient
in moisture is evident in 01Z surface observations with dewpoints in
the mid 40s to mid 50s near the CO border to the lower-mid 60s near
Hill City, KS. A mesonet site at Kingsley Dam in Keith County, NE
recorded a 77 mph gust at 0144Z.
Given the favorable low-level thermodynamic profile featuring a
well-mixed/steep lapse rate profile and an organizing MCS, there is
an expectation for severe gusts becoming spatially more expansive
during the next several hours. A recent model run of the HRRR takes
this MCS south of the I-70 corridor around 05Z. A spatial
extension-in-area may need to be considered in the short term for
Thomas, Sheridan, Graham, and Rooks counties in KS.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 39000153 40750269 41310124 41059937 39119903 39000153
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