U.S. Severe Weather Forecast (Convective Outlook)

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Storm Prediction Center ac 180548 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1148 PM CST Fri Nov 17 2017 


Valid 181200z - 191200z 


..there is a slight risk of severe thunderstorms across the lower 
Ohio Valley... 


..there is a marginal risk of severe thunderstorms across the 
greater Ohio Valley... 


... 
Thunderstorms capable of severe wind gusts, marginal hail, or a 
brief tornado will be possible Saturday mainly over the Ohio Valley 
region. 


... 


A vigorous mid-level trough will quickly move east from the plains 
toward the East Coast on Saturday. As this occurs, a surface cyclone 
near St. Louis will deepen and race to the northeast, reaching 
upstate New York by Sunday morning. Strong mid-level winds (nearing 
100 knots at 500 millibars) will overspread much of the Ohio Valley 
as a surface cold front pushes southeast. 


..lower Ohio Valley... 


Strong forcing for ascent along the southeastward-advancing cold 
front should allow for thunderstorms to develop in the 18-21z time 
frame. Despite widespread cloud cover, most-unstable cape values 
should still increase to between 500-1000 j/kg given the degree of 
Theta-E advection associated with the 50-60 knot low-level jet. The 
modest buoyancy and lower-tropospheric flow largely parallel to the 
front should result in thunderstorms organizing into one or more 
small, bowing segments. Damaging wind gusts will be possible with 
the strongest clusters/segments. Long hodographs with small loops in 
the lowest three kilometers suggest that a brief tornado cannot be 
ruled out within the larger thunderstorm clusters/segments. With 
time and eastward extent, thunderstorms should outrun the greatest 
buoyancy, diminishing the overall severe threat. 


..northeast Missouri eastward into Ohio... 


Strong, moist isentropic ascent on the nose of a 40-60 knot 
low-level jet should allow for elevated thunderstorms to occur along 
and north of the track of the surface low/warm front. Here, 
most-unstable cape values up to 1000 j/kg and mid-level-lapse rates 
between 7 and 8 c/km will support a marginal hail risk. 


.Marsh.. 11/18/2017 


$$ 

Mesoscale Discussion


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sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 061643 
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Mesoscale discussion 1767 
National Weather Service Storm Prediction Center Norman OK 
1043 am CST Mon Nov 06 2017 


Areas affected...northern Arkansas...southern Missouri...far western 
Tennessee and Kentucky 


Concerning...severe potential...watch unlikely 


Valid 061643z - 061915z 


Probability of watch issuance...20 percent 


Summary...a smattering of thunderstorms today will have the 
capability of producing marginally severe hail. 


Discussion...a small cluster of thunderstorms persists across 
northeast Arkansas in a zone of modest instability and supported by an 
elevated warm front. Flow aloft is strong out of the west, resulting 
in favorably long hodographs for sustained cells. These cells have 
mainly shown indications of hail less than 1.00" this morning. 


Behind this activity, satellite imagery shows new elevated 
development across far northern Arkansas into southwest MO, with lighting 
recently detected. Models suggest increasing lift from warm 
advection across this area today with backed 850 mb flow. In 
addition, temperatures aloft are cooler with northward extent which 
will aid destabilization as low-level warm advection continues. The 
result should be an additional rash of strong storms with a few 
containing hail up to 1.00". 


.Jewell/Hart.. 11/06/2017 


..please see www.Spc.NOAA.Gov for graphic product... 


Attention...WFO...pah...Meg...lsx...lzk...sgf...tsa... 


Latitude...Lon 35088963 35129127 35379235 35989304 36429346 36779361 
37109358 37359343 37619311 37839281 37909229 37879185 
37829038 37588974 37248921 36778887 36298871 35708880 
35348891 35088963