Severe Weather Threat thru Jun 24

Tue Jun 17 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Svr Tstms for N Hi Plains to Great Lakes to Hudson Valley...

Isolated To Scattered Thunderstorms With Damaging Wind...Very Large Hail...And Few Tornadoes Are Expected From Eastern
Montana...Northeast Wyoming...And The Western Dakotas Into The

Damaging Wind And Hail Will Be The Primary Severe Weather Threats With Storms From The Great Lakes To Western New England.

Northern Plains Into Upper Midwest...

The Severe Threat Across Central/Ern Sd Into N/Nern Neb Appears To
Be Somewhat Conditional This Afternoon/Evening.

While A Very Unstable Airmass Exists Across The Region With Mlcape Greater Than 2000 J/Kg In Place...Strong Capping Remains.

This Is Due In Part To Cloud Cover Limiting Sfc Heating...With Current Temperatures In The 70s To Near 80 F Across Much Of Sd Into N-Cntrl Neb.

Increasing Low Level Flow Along Stalled Sfc Boundary And An Increasing Llj This Evening In The Vicinity Of The Sfc Dryline May Be Adequate For A Storm Or Two To Develop In The Moist/Unstable Airmass.

If Storms Do Develop...They Would Pose A Large Hail Threat.

More Likely...The Shortwave Impulse Will Provide Deep Layer Ascent For Development Across Mn/Ia Late This Afternoon Into This Evening.

As The Swly Llj Strengthens This Activity Should Grow Upscale Into An E/Se Propagating Mcs Overnight.

Given Uncertainty And Conditional Nature Of The Threat As Previously
Mentioned Over Parts Of Sd/Neb...The Only Changes Made Have Been To Trim The Eastern Edge Of The 30 Percent Hail Area Further To The West.

Prev Discussion...

Great Lakes To Wrn New England This Afternoon Through Tonight...

Latest Model Guidance Suggests That The Remnant Cold Pool Associated With A Decaying Mcs Over Lower Mi And/Or The Cold Front Trailing The Surface Low Will Be The Focus For Surface-Based Tstm Development By Afternoon Across Sern Lower Mi.

Storms Will Subsequently Grow Upscale Into A Broadly Bowing Qlcs Which Will Spread Ewd/Sewd Through The Lower Great Lakes And Upper Oh Valley...With This System Eventually Moving Into Parts Of New England And Perhaps The Nrn Mid Atlantic Region Later This Evening Into The Overnight Hours.

Damaging Winds Will Likely Be The Primary Hazard With These
Storms...Though Large Hail And/Or A Brief Tornado Remain Possible.

Midwest This Afternoon Into Tonight...

Model Guidance Is Suggestive That A Weak Perturbation Over The Cntrl High Plains This Morning Will Translate Into The Mid Mo Valley By This Evening.

This Feature Coupled With Persistent Waa To The N Of The Stalled Surface Front Are Expected To Promote Widely Scattered Tstm Development By Late Afternoon Or Early Evening Over Srn Mn Or Nrn Ia.

Similar To Monday...12z Region Soundings Sampled Very Steep Midlevel Lapse Rates /I.E. 700-500-Mb Lapse Rates Of 9.0-9.5 C Per Km/ Which Overlie A Very Moist Boundary Layer With Lowest-100-Mb Mean-Mixing Ratios Of Around 15 G/Kg Which Will Yield Afternoon Mlcape Of 4000-5000 J/Kg.

This Instability Will Align With A Vertically Veering Wind Profile With 40-50 Kt Of Effective Bulk Shear Which Will Be Quite Conducive For Supercells Capable Of Very Large Hail And A Few Tornadoes Within The First Few Hours Of Storm Initiation.

With Time...Coalescing Storm-Scale Cold Pools Will Promote Upscale Convective Growth Into A Swd Or Sewd-Moving Mcs Capable Of Damaging Winds And Large Hail Into Tonight.


Wed Jun 18 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Svr Tstms for N Plains E to Cntrl & S Hi Plains...

Severe Thunderstorms Are Expected Across Much Of The Northern And Central Plains Into The Upper Mississippi Valley...And From Lower Michigan Eastward Into Pennsylvania.

Isolated Severe Storms Are Also Possible From Central Kansas Into West Texas.

Large Hail And Damaging Winds Will Be The Main Threats...With The Most Significant Severe Storms Expected Across The Dakotas And Minnesota.

The Upper Low Over Western Mt Wednesday Morning Will Pivot E/Newd Across The Nrn Rockies...While The Attendant Shortwave Trough Moves Into The Nrn And Cntrl Plains By 12z Thursday.

At The Sfc...Low Pressure Over Sd Will Shift Ewd Toward Mn While A Sfc Trough Extends Swwd Across Wrn/Cntrl Ks Into The Srn High Plains.

A Cold Front Will Move Ewd Across Wrn Sd/Nd/Neb By 00z...With A Dryline Extending S/Sw From Wrn Ks Through W Tx.

Sly Low Level Flow Ahead Of These Features Will Maintain Abundant Moisture Across The Plains Into The Mid/Upper Ms Valley And Upper Great Lakes Region.

A Moist And Moderately To Strongly Unstable Airmass Will Be In Place And Severe Storms Are Expected Once Again Across Portions Of The Nrn Plains Into The Upper Midwest As Well As Along The Dryline From
Wrn/Cntrl Ks Into W Tx.

Further East...A Weak Shortwave Impulse Tracking Ewd Across Wi/Mi
During The Morning And Early Afternoon Will Likely Be A Focus For
Early Convection/Remnant Mcs At The Beginning Of The Period.

As This Feature Continues To Lift E/Ne It Will Become Absorbed In
Larger-Scale Trough Over Se Canada And The Nern U.S.

At The Sfc...Low Pressure Over New England Will Track E/Ne Into The Nw Atlantic And A Cold Front Will Drop S And E Across New England And The Great Lakes.

Widespread Thunderstorms Are Expected To Develop During The Afternoon Ahead Of The Cold Front And Along A Sfc Trough From Nrn Il Through The Great Lakes/Ohio Valley.

Nrn Plains Into The Upper Ms/Mid-Mo Valleys...

Thunderstorms Are Expected To Be Ongoing At The Beginning Of The
Period From Ern Mt Into The Wrn Dakotas and may Pose a Marginal Hail Threat Before The Focus Shifts Ewd During The Afternoon.

Additional Thunderstorm Development Is Expected Along The Sfc Trough From Wrn/Cntrl Nd Sewd Through Cntrl/Ern Sd Into Mn/Nrn Ia.

Strong S/Sely Low Level Flow Will Maintain Upper 60s/Lower 70s Dewpoints And Strong Sfc Heating Will Result In Moderate To Strong
Instability By Early Afternoon.

Steep Lapse Rates And Favorable Wind Profiles Will Favor Supercells Capable Of Very Large Hail...Strong Winds And...If Cells Can Remain Semi-Discrete...Tornadoes.

As A Swly Llj Strengthens During The Evening/Overnight...Upscale Growth May Occur With A Damaging Wind Threat Spreading Across Mn/Nrn Ia Into Wi.

Ern Neb Swwd Into W Tx...

Thunderstorm Development In The Vicinity Of The Dryline/Cold Front
In Neb Is A Little Uncertain With Forecast Model Soundings Indicating Capping May Be A Concern.

Further Sw Along The Dryline...Storms Should Remain More Isolated To Widely Scattered Further Removed From Stronger Forcing For Ascent And Stronger Deep Layer Flow.

That Being Said...Warm Sector Environment Will Be Very Moist / Unstable And Confluent Sly Flow/Increasing Llj Should Be Sufficient To Focus Development During The Afternoon/Evening In The Vicinity Of The Aforementioned Boundaries.

Steep Lapse Rates And Sufficient Effective Shear Will Favor Rotating Storms Capable OfLarge Hail...And Occasionally Strong Wind Gusts.

Nrn Il Through Pa...

Storms Should Be Ongoing Wednesday Morning From Se Wi Into Lower Mi As The Shortwave Impulse Lifts E/Newd Into Srn Ontario.

A Sfc Trough Will Extend Ewd From Nrn Il Into Pa And Thunderstorm Activity Should Continue/Develop Along This Feature In A Very Moist / Unstable Airmass.

Mainly Unidirectional Wind Profiles Should Favor Forward Propagating Storm Clusters/Lines Capable Of Damaging Winds. But
Sufficient Lapse Rates And Degree Of Instability Will Support
Instances Of Large Hail As Well.


Thu Jun 19 Convective Outlook
Storm Prediction Center Norman Ok
No Svr Tstm Areas Forecast...

Isolated Severe Storms With Hail And Wind Will Be Possible From The Upper Mississippi Valley Southward Across The Central Plains.

An Upper Trough Axis Is Forecast To Eject Newd Across The Nrn
Plains/Upper Ms Valley With Main Low Centered Over Srn Sk.

A Sfc Trough Attendant To This System Will Also Shift Newd Across Mn And Wi...With Gradually Veering Low-Level Winds And Decreasing Shear Profiles Overall.

Moisture And Instability Will Remain For A Few Strong Storms... Although Predictability Is Too Low For A Slight Risk In This Area.

To The S...An Old Front Will Become More Diffuse With Time From Ern
Neb Into Wrn Ks...But May Also Serve As A Focus For A Few Severe


Areas Of Thunderstorms Are Likely To Be Ongoing Across The Large
Area...From Nd Into Mn And Ia Ewd Across Il...Ind...And Oh.

The Most Favorable Shear Profiles Are Actually Going To Be During The Morning And Early Afternoon Across The Upper Ms Valley...Before The Upper Trough Axis Passes By.

Some Wind And Hail Threat May Exist...Assuming A Nocturnal Mcs Does Not Overturn The Entire Area.

The Dwindling Shear Will Counteract Any Further Destabilization From
Heating...But A Few Strong To Severe Storms Will Be Possible.

Ern Neb...Ks...Nw Ok Into Tx Panhandle...

A Moist Air Mass Will Remain S Of The Old Front...With Heating
Reducing Cin To Near Zero By Late Afternoon.

Sfc Winds Will Be Weak Near The Boundary...But Lack Of Capping And Weak Convergence Should Result In Scattered Storms.

Shear May Just Be Strong Enough For A Few Severe Multicells Or Weak Supercells Given Steep Lapse Rates Aloft And Ample Instability ... But They Should Be Slow-Moving And Affect A Relatively Small Area Mainly Across Srn Ks Into The Tx Panhandle.

A Slight Risk Is Not Out Of The Question In Later Outlooks For Large Hail Potential.


Jun 20-24 Convective Outlook
Storm Prediction Center Norman Ok

On D4...An Upper Low Over The Nrn Plains Will Shift Nwd Into Canada ... With Relatively Weak Zonal Flow Prevailing Over The Southern Two-Thirds Of The Conus.

This Low Will Become Absorbed By The Ern Canada Trough Which Will Lower Heights Across The Nern Conus Resulting In A Modest Wly Flow Regime From The Midwest Into The Nern States.

Weak Forcing With This Feature As It Travels Ewd Will Result In Thunderstorms Over From Il Into Lower Mi On Sat/D5...Then Into The Nern States On Sun/D6.

However...Shear Will Be Marginal And Potential Is Too Low For Any Risk Areas.

The Pattern Remains Relatively Inactive For The Remainder Of The
Outlook Period.

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