U.S. Severe Weather Forecast (Convective Outlook)

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Storm Prediction Center ac 231627 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1127 am CDT Wednesday Apr 23 2014 


Valid 231630z - 241200z 


..there is a slight risk of severe thunderstorms over parts of the southern and Central 
Plains... 


... 
Severe thunderstorms are expected this afternoon into tonight across 
parts of the central and southern Great Plains. Large hail will be 
the primary initial hazard...with damaging winds and a few tornadoes 
also possible. 


..synoptic setup... 
Progressive/moderately amplified pattern will prevail this 
period...with Great Basin trough the main factor affecting severe weather 
potential into Thursday. The trough should continue east to the High Plains by 
12z Thursday as downstream ridge reaches the lower Ohio Valley. 


Within the trough...main shortwave impulse now entering the lower Colorado 
valley should pivot east to the Arizona-nm border this evening and into West Texas early 
Thursday. At the same time...weaker downstream impulse over nm should 
lift NE across the Central High plains today and into the middle MO valley 
early Thursday. In the northern part of the trough...disturbance now over Wyoming 
will track NE into ND by evening...advancing an associated cold front 
east-southeastward across the Central Plains. Farther S...Lee trough/dry line 
segments should mix east into western portions of central and Southern Plains this 
afternoon...before being overtaken by the cold front tonight/early Thursday. 


Both the Central Plains cold front and the dry line/Lee trough segments 
farther S will promote strong to severe storm development...beginning 
this afternoon and continuing into tonight. 


..cntrl plains cold front this aftn/eve... 
Thunderstorms should form along cold front from S central/southeast South Dakota southwestward into northwest 
Kansas as the boundary accelerates east-southeastward. Current observations suggest 
that moisture will remain somewhat limited...with precipitable water around 1 inch 
and average surface dewpoints around 50 f. Low to middle-level lapse rates 
will...however...be fairly steep...contributing to MLCAPE on the 
order of 500 j/kg in northestern Nebraska to above 1000 j/kg in northwest Kansas. Deep 
shear will vary across the region...ranging from 40 knots west-southwesterly in Kansas 
to 50 knots south-southwesterly in northern Nebraska. 


Overall setup appears favorable for relatively high-based sustained 
storms/supercells capable of damaging wind and hail as northern stream 
impulse glances region and weaker disturbance approaches from the 
SW. The activity should merge into an east-southeast-moving mesoscale convective system in southern Nebraska/northern 
Kansas by early tonight. A gradually diminishing damaging wind threat may 
persist in association with embedded forward-propagating 
segments/small bows through early Thursday. 


..cntrl/Southern Plains Lee trough/dry line this afternoon into tonight... 
Clouds associated with lead upper impulse should clear region along 
Lee trough/dry line segments over western parts of the central and Southern 
Plains by early afternoon...allowing for substantial heating. At the same 
time...boundary layer moisture should continue to slowly increase 
through advection. Surface dewpoints should average in the upper 50s to 
around 60 over West Texas...with somewhat lower values extending northward into 
western Kansas. Coupled with steep middle-level lapse rates...expect MUCAPE to 
range from 1000 j/kg in Kansas to 2000 j/kg in Texas. 


Surface heating and height falls associated with progressive nature of 
large-scale trough should Foster scattered storm development along Lee 
trough/dry line segments beginning late this afternoon and continuing 
into tonight from western Kansas to west central Texas. More widely scattered activity may 
extend S to the Texas Big Bend. Coupled with 40-45 knots west-southwesterly deep shear 
and steep middle-level lapse rates...environment should be favorable for 
supercells with large hail...some possibly very large...and locally 
damaging wind. A risk for tornadoes also may develop...particularly this 
evening/early tonight over northwest Texas/SW OK...as nocturnal and dynamic 
strengthening of southerly low level jet enlarges hodographs. This window of 
opportunity should diminish later tonight as the storms merge into 
short line/clusters...although a limited risk for severe wind/hail may 
persist near the Red River through early Thursday. 


.Corfidi/cohen.. 04/23/2014 






Mesoscale Discussion


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Storm Prediction Center mesoscale discussion 222307 
njz000-paz000-dez000-mdz000-dcz000-vaz000-wvz000-230100- 


Mesoscale discussion 0384 
National Weather Service Storm Prediction Center Norman OK 
0607 PM CDT Tuesday Apr 22 2014 


Areas affected...southeast PA...cntrl/srn New Jersey...northern Maryland...northern Delaware 


Concerning...severe potential...watch unlikely 


Valid 222307z - 230100z 


Probability of watch issuance...20 percent 


Summary...isolated damaging wind gusts are possible with thunderstorms along 
a southeastward progressing cold front. Isolated nature of the threat is 
expected to preclude the need for a ww. 


Discussion...temperatures across the Maryland area are generally in the 
upper 60s to lows 70 with 0-3 km lapse rates above 7 degree per km 
noted in recent mesoanalysis. Instability is marginal but 0-6 km 
bulk shear from 40 to 50 knots will continue to support at least modest 
thunderstorm activity along the frontal boundary. With the shear vector 
oriented perpendicular to the frontal boundary across much of the 
area...activity along the cold front will have the potential to 
produce occasional damaging wind gusts as it continues southeastward. Some 
small hail is also possible in the strongest updrafts. 
Isolated/marginal nature of the severe threat will likely preclude the 
need for a ww. 


.Mosier/Mead.. 04/22/2014 


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


Attention...WFO...okx...phi...ctp...lwx... 


Latitude...Lon 40317640 40877511 40607446 40307422 39277508 38857606 
39027794 39417823 39687747 40317640