Severe T-storm US Outlook Through Sep 16

Day 1 Convective Outlook
Nws Storm Prediction Center Norman Ok
0241 Pm Cdt Wed Sep 15 2010

Valid 152000z - 161200z

...There Is A Slgt Risk Of Svr Tstms From The Upper Ms Valley To Wrn

Based On Latest Trends...Have Made A Few Significant Changes To
Portions Of The Nrn And Srn Plains Regarding The Increased Potential
For Severe Thunderstorms This Afternoon. Severe
Thunderstorms...Supercellular In Nature...Are Developing Along The
Cold Front Across Ern Sd...A Bit Farther West Than Earlier
Anticipated. This Evolution Will Require A Wwd Expansion Of The
Slight Risk Into Sd. Likewise...Have Raised Tornado And Hail
Probabilities Into The Plains Of Ern Sd Where Low Level Flow Remains
Backed With 60s+ Sfc Dew Points.

Farther South...Strong Sfc Heating Across The Srn Plains Has Forced
Temperatures To Near 100f Along The Dryline Over Wrn Ok Into Extreme Swrn Ks. Latest Vis Imagery Indicates Cu Field Is Expanding Along An Outflow/Dryline Intersection West Of Ict...Then Swwd Into Nwrn Ok. Diagnostic Data Indicates The Cap Has Weakened Considerably And Mlcape Values Are Now In Excess Of 3000 J/Kg. Given These Trends...Have Extended The Slight Risk Swwd Along The Dryline To Account For Isolated Severe Storms Capable Of Producing Primarily Damaging Winds. The Greater Threat For Hail And Isolated Tornadoes Will Remain Confined To Portions Of Ks Where Cooler Boundary Layer And Stronger Shear Exist.

Darrow.. 09/15/2010

Day 2 Convective Outlook
Nws Storm Prediction Center Norman Ok
1223 Pm Cdt Wed Sep 15 2010

Valid 161200z - 171200z

...There Is A Slgt Risk Of Svr Tstms Across The Oh/Tn Valley Into
Upstate Ny...

...There Is A Slgt Risk Of Svr Tstms Across The Srn High Plains...

...Oh/Tn Valley To Srn New England...

Strong Height Falls...On The Order Of 90m/12hr...Will Overspread The
Great Lakes Into The Upper Oh Valley During The Day As A Pronounced Shortwave Trough Ejects Across The Region. By 18z This Feature Should Extend From Lower Mi Into Ind...Coincident With A Sharp Sfc Front That Should Progress Into Upstate Ny-Wrn Pa-Swwd Along The Oh River By Late Afternoon. It Appears A Narrow Wedge Of Strong Boundary Layer Heating Will Contribute To Enhanced
Instability...More Than Adequate For Frontal Convection Fairly Early
In The Period. Focused Ascent Should Easily Contribute To Squall
Line Development By 18z Across Oh Where Forecast Soundings Suggest Storm Motions Could Exceed 40-50kt. Damaging Winds Are Certainly Possible Given That Sbcape Is Expected To Approach 1000 J/Kg Prior To Convective Overturning. Once Developed...A Strongly Forced Squall Line Will Move Across The Oh Valley Before Gradually
Weakening Due To Increasingly Hostile Boundary Layer Over Cntrl Pa. There Is Some Concern That A Marked Increase In Low Level Moisture During The Overnight Hours Will Enhance The Prospect For Sfc Based Convection Over Srn New England. If Mid-Upper 60s Dew Points Do In Fact Return To This Region A Slight Risk Will Certainly Be Warranted As Very Strong Flow Just Off The Sfc Would Enhance The Damaging Wind Potential For Any Storms That Develop During The 06-12z Time Frame.

This Region Will Be Monitored For A Possible Upgrade.

...Srn High Plains...

Strong Convection...Possibly Severe...Is Expected To Develop Along
Trailing Sfc Front Over The Srn High Plains Thursday. Latest Model
Guidance Strongly Imply That Upslope Flow Along With Strong Diurnal
Heating Will Remove The Cap Across The Tx/Ok Panhandles Into Sern
Co. Forecast Shear Across This Region Is Supportive Of Deep Rotating Updrafts As Sely Low Level Flow Veers Into The Wnw At Mid Levels.

Additionally...Latest Wv Imagery Suggests A Well Defined Shortwave
Trough Ejecting Across Srn Ca Will Spread Into The High Plains
Around Peak Heating. This Should Enhance The Convective Potential
With Early Supercells Evolving Into Several Thunderstorm Clusters By
Evening. Large Hail - Damaging Winds And Perhaps An Isolated
Tornado Are The Severe Threats With This Activity.

..Darrow.. 09/15/2010

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