U.S. Severe Weather Forecast (Convective Outlook)

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Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1246 am CDT Wednesday Apr 23 2014 


Valid 231200z - 241200z 


..there is a slight risk of severe thunderstorms over the central/Southern Plains... 


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


... 
A shortwave trough over the Great Basin/northern intermountain west will 
eject northeastward towards the southern prairie provinces and northern plains. An 
upstream impulse just off the Pacific northwest coast will rotate through 
the base of the broader upper-level trough ... the southern 
rockies this evening. At the surface...a cold front will push across 
the Central High/northern plains with a dryline mixing into SW Nebraska to West Texas 
this afternoon. This front will progressively overtake the dryline 
and reach the lower MO valley to Southern Plains on Thursday morning. 


..cntrl/Southern Plains... 
The plume of richest low-level moisture /characterized by precipitable water values 
of 1.25-1.50 inch per 00z radiosonde observations and GPS data/ will likely emanate 
northward from deep S Texas within a north/S-oriented corridor ahead of the 
aforementioned cold front/dryline. Although this moisture influx 
will be relatively modest /especially with northern extent/...surface dew 
points should reach into the 50s north of the Red River with lower 60s 
across central Texas. 


Latest expectations remain similar to the previous outlook with two 
general regimes for severe thunderstorm development amidst quite steep 
tropospheric lapse rates this afternoon. Across central Nebraska into northern 
Kansas...storms will develop along the southeastward-advancing cold front. 
Beneath moderate-strong 500-mb swlys owing to the glancing influence 
of the northern plains shortwave trough...a few supercells should form 
producing severe hail. With largely unidirectional wind profiles and 
undercutting nature of the cold front...this convection should 
quickly organize into clusters and short-line segments. Severe 
hail/wind will be possible into the evening...with intensity waning 
overnight towards the MO valley. 


Farther S...scattered discrete thunderstorms will form along the dryline 
late afternoon to early evening. Initial activity should consist of 
high-based supercells with MLCAPE of 1000-2000 j/kg and effective 
bulk shear of 30-35 knots. Large hail /a few significant/ and isolated 
severe wind gusts should be the primary hazards. During the 
evening...low-level hodographs will become quite enlarged as flow 
strengthens. Potential for a few tornadoes may be realized between 
00-03z on the northern periphery of near 60 degree f surface dew points 
in vicinity of west OK/northwest Texas. Still...quality of boundary-layer moisture will be 
a limiting factor to a more robust tornado risk. With 
time...coalescing of updrafts and persistent low-level warm air advection may yield 
a small mesoscale convective system moving eastward across parts of OK and North Texas with severe 
hail/wind risks subsiding early Thursday. 


.Grams/Mosier.. 04/23/2014 

Mesoscale Discussion


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Storm Prediction Center mesoscale discussion 222307 
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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