Severe Weather Outlook thru May 16

Fri May 9 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Of Svr Tstms for Ozark Plateau to Lower Oh Valley...
Slgt Risk Of Svr Tstms for parts of Tx...

Scattered Severe Thunderstorms Are Expected Over Parts Of
Central...Southern...And East Texas Today.

Elsewhere...A Few Severe Thunderstorms May Occur Over Parts Of The Ozarks And The Mid Mississippi And Ohio Valleys.

A Broad Cyclonic Flow Regime Will Be Maintained Over The Conus
Through The Day One Period To The South Of An Upper Low Which Will Remain Anchored Over Cntrl Canada.

Within This Large-Scale Regime...A Short-Wave Trough Comprised Of Multiple Vorticity Maxima Will Translate Newd Through The Upper Great Lakes...Mid Ms Valley And Ozarks In Tandem With A 80 Kt Jet Streak At 500 Mb Which Will Weaken While Moving From The Ozark Plateau Into Oh Valley.

Meanwhile...A Lower-Latitude Perturbation Will Track Across Nrn
Mexico Into Srn Tx. These Developments Will Occur Downstream From A Midlevel Trough Which Will Amplify Over The Pacific Nw Into Nrn Great Basin.

At The Surface...A Cold Front Associated With The N-Cntrl U.S.
Short-Wave Trough Will Advance Ewd Through The Great Lakes With The Segment Over The Ozark Plateau Remaining Quasi-Stationary.

Meanwhile...The Swrn Extension Of The Front Over The Srn Plains Will Weaken Today With The Prominent Surface Feature Being A Dryline Which Will Stretch From S-Cntrl/Sern Ok Swwd Into The Edwards Plateau Of Tx.

Tx Today Into Tonight...

12z Soundings Showed The Presence Of A Very Moist Air Mass /Lowest 100-Mb Mean-Mixing Ratios Of 15-17 G Per Kg/ Surmounted By An Eml Characterized By 700-500-Mb Lapse Rates Of 7.0-7.5 C/Km.

These Parameters Will Combine With Daytime Heating To Yield Moderate To Strong Afternoon Instability To The Se Of The Dryline With Afternoon Mlcape Approaching 2000-3000 J/Kg.

Relatively Weak Capping Shown On The 12z Drt Raob Coupled With Dcva Attendant To The Short-Wave Trough Moving Out Of Nrn Mexico Are Expected To Support A Gradual Increase In Tstms Today Across The Edwards Plateau Into The Hill Country Amidst A Kinematic Environment Featuring A Vertically Veering Wind Profile With 30-35 Kt Of Deep-Layer Shear.

The Given Setup Will Support Supercells And Organized Multicells With A Risk For Very Large Hail And Damaging Wind Gusts.

Storms May Eventually Grow Upscale Into Clusters Along Consolidating Outflows With The Threat For Damaging Winds And Large Hail Continuing Through The Evening.

Ozark Plateau Into Lower Oh Valley This Afternoon Into Tonight...

Tstms Have Recently Developed Along/S The Front Over Cntrl Mo As Of Mid Morning Within A Zone Of Stronger Forcing For Ascent/Dcva
Associated With The Srn-Most Vorticity Lobe And Midlevel Jet Streak
Attending The Parent Midlevel Trough.

Daytime Heating Coupled With Dewpoints In The 60s Should Allow For Downstream Air Mass To Further Destabilize By Afternoon With Mlcape Approaching 1000-2000 J/Kg. And While The Midlevel Jet Streak /Mentioned In The Synopsis/ Will Be In The Process Of Weakening...More Than Sufficient Deep-Layer Shear Will Exist For The Evolution Of Supercells And/Or Bowing Structures By Afternoon Over E-Cntrl/Sern Mo.

Expect This Activity To Move Develop Ewd/Newd Into Parts Of The Lower Oh Valley Later This Afternoon Into Tonight With The Primary Hazards Being Large Hail And Damaging Wind Gusts.

A Separate Cluster Of Tstms May Develop This Evening Into The
Overnight Hours Invof Of The Stalled Front Over Srn Mo/Nrn Ar As
Forcing For Ascent Is Enhanced By A Low-Amplitude Short-Wave Trough Moving Across Ks/Ok.

Sufficient Instability And Vertical Shear Will Exist For Organized Storms...Including Supercells With A Risk For Large Hail And Damaging Winds.

Arklatex Into Lower Ms Valley...

Morning Observations Indicate That Considerable Overturning Of The
Air Mass Has Occurred With Nocturnal Storms Which Will Likely Temper The Degree Of Destabilization That Occurs This Afternoon.

While Isolated Severe Storms Remain Possible Along Residual Convective Outflow Boundaries...More Organized Potential Appears To Be Limited.

As Such...The Categorical Slight Risk Has Been Removed From Some Locations.


Sat May 10 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Of Svr Tstms for Srn & Cntrl Plains...Ozarks to Mid-Ms Valley...

Isolated Severe Thunderstorms Are Possible From Central Oklahoma Northward Into East-Central Kansas To The Lower Missouri Valley Late Afternoon To Evening On Saturday.

Large Hail And Wind Damage Should Be The Primary Threats.

Srn And Cntrl Plains/Mid Ms Valley...

Mid-Level Flow Will Become Southwesterly Across The Cntrl U.S.
Saturday As An Upper-Level Trough Moves Sewd Into The Intermountain West.

In Response...A Sfc Low Will Rapidly Deepen Across The Cntrl High Plains Strengthening Moisture Advection Across Ern Ks Saturday
Afternoon And Evening As A Warm Front Becomes Established.

Moist And Unstable Air Will Exist Southwest Of The Front With Sfc Dewpoints Across Ern Ks And Mo Generally Ranging From The Upper 50s F To The Mid 60s F.

This Should Result In Moderate Destabilization During The Day Across Much Of The Slight Risk Area.

Although The Models Are In Disagreement...The Most Likely Location For Convective Development Saturday Afternoon Would Be Along The Instability Gradient From Ecntrl Ks Ewd Into Wrn Mo.

Additional Storms May Develop Ewd Across Cntrl And Ern Mo Late Saturday Afternoon.

Convective Coverage Should Markedly Increase During The Evening And Overnight Period From Ne Ks...Se Neb Ewd Across Ia And Nrn Mo Due To Strong Warm Advection Associated With A Strengthening Low-Level Jet.

Forecast Soundings At 00z/Sun For Kansas City Show A Deep Moist
Layer Below 850 Mb With Steep Lapse Rates In The Low To Mid-Levels.

This Should Contribute To Moderate Instability With Mlcape Estimated
In The 2000 To 2500 J/Kg Range.

The Sounding Also Shows Veering Winds With Height Below 700 Mb And Strong Speed Shear In The Mid-Levels Resulting In About 40 To 45 Kt Of 0-6 Km Shear.

This Along With The Steep Mid-Level Lapse Rates Should Make Conditions Favorable For Supercells With Large Hail.

Isolated Hail Greater Than 2 Inches May Occur With Any Dominant Supercell Close To The Max In Instability.

Have Added A Significant Hail Probability Contour Across Ern Ks And Wrn Mo Where The Potential For Very Large Hail Appears To Be Greatest.

In Addition...0-3 Km Lapse Rates Approaching 8.5 C/Km Should Be Supportive Of A Wind Damage Threat.

As A 50 To 65 Kt Low-Level Jet Strengthens Saturday Evening Into The Overnight Period...A Threat For Large Hail Should Continue Mainly Across Nern Ks...Se Neb...Nrn Mo And Far Sw Ia.

Oh And Tn Valleys...

A Subtle Upper-Level Trough Will Move Ewd Across The Oh And Tn
Valleys Saturday Afternoon.

At The Sfc...A Corridor Of Low-Level Moisture Should Be In Place From The Mid Ms Valley Newd Into The Upper Oh Valley.

Moderate Destabilization Should Occur Along This Corridor Saturday With Isolated Convective Initiation Possible During The Afternoon.

Forecast Soundings Along The Instability Axis At 21z/Sat Show Mlcape Around 1500 J/Kg With 0-6 Km Shear Of 45 To 55 Kt.

This Should Support A Severe Threat With Any Cell That Can Initiate In Spite Of Weak Low-Level Convergence.

In Addition...Subsidence Behind The Exiting Shortwave Trough Should Help Keep Any Severe Threat Very Isolated.

For This Reason...Will Maintain Severe Probabilities At 5 Percent.


Sun May 11 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Of Svr Tstms for Mid-Ms Valley to Srn Plains...

A Significant Severe Weather Episode Appears Probable Beginning
Sunday Afternoon From The Mid-Mississippi Valley To The Southern
Great Plains.

A Vigorous Shortwave Impulse Embedded Within An Amplified
Upper-Level Trough Will Track From The Srn Great Basin To The Srn

Attendant Mid-Level Speed Max Will Become Centered From The Srn High Plains To The Cntrl Plains Early Mon.

At The Surface...A Lee Cyclone Will Diurnally Deepen Over The Srn High Plains.

The Dryline Should Mix Towards The Ern Tx Panhandle/Wrn Ok Border S/Swwd Across The Permian Basin.

Guidance Differs On The Acceleration Of A S/Sewd-Progressing Cold Front Over The Cntrl/Srn Plains.

Mid-Ms Valley To Srn Plains...

Pervasive And Strengthening Swlys At 700 Mb Will Result In An
Expanding Eml Plume And Attendant Capping Inversion Early Sun...With Increasingly Rich Boundary Layer Moisture Given Strong Poleward Advection From The Wrn Gulf.

Middle To Upper 60s Surface Dew Points Should Become Established From The Lower Mo Valley Swd...Yielding A Broad Strongly Unstable Air Mass With Mlcape Aoa 2500 J/Kg Ahead Of The Dryline/Cold Front.

The Nrn Extent Of Strong Destabilization Should Be Delimited By Early Sun Waa-Driven Convection Over Parts Of The Lower Mo Valley.

Some Of This Activity May Continue E/Newd Through The Day With An Isolated Severe Risk...But More Probable Surface-Based Development Should Occur With Swrn Extent Where Greater Insolation Occurs.

Strong Convergence Along The Front Will Likely Yield Increasingly Numerous Storms Late Afternoon Into Evening From Ern Ks Into Srn Ia.

Large Hail /Some Significant/ And A Few Tornadoes Will Be Possible Initially.

The Potential For Undercutting By The Front Should Yield Cluster And Eventual Linear Modes With Severe Hail/Wind Hazards Persisting Into Sun Night.

A Large Mcs May Ultimately Evolve Given The Strengthening Large-Scale Ascent Downstream Of The Upper Trough And Broadly Unstable Warm Sector.

Farther S...Convergence Along The Dryline Will Strengthen / Especially Invof Triple-Point/ And Intense Surface Heating Should
Remove Inhibition...With Isolated To Scattered Storms Developing
Late Afternoon.

Although Hodographs May Not Be Overly Large...Cross-Boundary Deep-Layer Flow Will Be Favorable For Discrete Supercells Given The Degree Of Instability.

Relatively Large Surface Dew Point Depressions Suggest Very Large Hail Would Be The Primary Initial Hazard.

The Tornado Risk Should Be Maximized In Early Evening As A Sly Llj Strengthens And Spreads Lower.

Ewd Extent Of Overnight Severe Potential Is Uncertain Owing To Model Differences In Cold Front Evolution And Degree Of Nocturnal Warm Sector Inhibition.


May 12-16 Convective Outlook
Storm Prediction Center Norman Ok

At Least Low-End Severe Potential Is Evident On D4/Mon From The
Midwest To The Srn Plains.

However...Model Dispersion Grows From D3 With Differences In The Handling Of Individual Nrn And Srn-Stream Shortwave Impulses Within An Amplified Upper-Level Trough Over The Rockies Or Plains.

This Renders Below-Average Confidence In Placement Of The Surface Cold Front...Where Widespread Convection May Be Ongoing At 12z/Mon.

Coupled With Mid-Level Winds Largely Paralleling The Front...Overall Severe Intensity May Be Limited.

Beyond D4...Redevelopment Of Tstms May Occur Daily Along/Ahead Of The Cold Front...Which Should Be Slow-Moving Within A Fairly
Meridional Flow Regime.

This Type Of Pattern Should Also Preclude An Ern Extension Of A Plains Eml...Especially With Preceding Days Of Widespread Convection On D3-4.

This Would Likely Inhibit Strong Instability And Along With Large Spread In Guidance Yields Low Severe Probabilities.

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