Severe Storm Outlook Narrative (AC)
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379
ACUS11 KWNS 230209
SWOMCD
SPC MCD 230209
IAZ000-230415-

Mesoscale Discussion 1129
NWS Storm Prediction Center Norman OK
0909 PM CDT Thu Jun 22 2017

Areas affected...Central/Northeast IA

Concerning...Severe potential...Watch unlikely

Valid 230209Z - 230415Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated hail and damaging wind gusts are possible with
thunderstorms along the front as it moves across IA. A generally
limited severe threat is anticipated and a watch is not anticipated,
but convective trends will be monitored closely.

DISCUSSION...Thunderstorms have developed over the past hour along
the cold front extending from CCY (in northeast IA) southwestward to
CBF (in southwest IA). Airmass ahead of this cold front is
characterized by dewpoints in the low 70s, which, when combined with
steep mid-level lapse rates (i.e. around 7-7.5 deg C per km per the
latest mesoanalysis), is supportive of moderate instability.
Continued southeastward progress of the cold front into this airmass
is expected to result in continued thunderstorm development along
the cold front. This region is along the southern periphery of the
stronger flow aloft but enough shear (i.e. effective shear around 30
kt) exists to support some updraft organization and a supercell or
two, particularly across northern portions of the region where the
shear is strongest. Hail is possible with these more organized
storms. Farther south, a more multicellular mode is anticipated with
any hail likely a result of brief updraft intensification due to
cell mergers. Some upscale growth into a more linear system is
possible but the generally modest mid-level flow (and shear) are
expected to preclude anything but occasionally damaging winds. As a
result, a watch is not current expected but trends will be monitored
for upscale growth and a resulting increase in the damaging wind
threat.

..Mosier/Hart.. 06/23/2017

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

ATTN...WFO...DVN...ARX...DMX...OAX...

LAT...LON   41529527 42659365 43299270 43409152 42879114 41369267
            41089468 41529527




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