Severe Weather Threat thru Jun 23

Mon Jun 16 Convective Outlook
Storm Prediction Center Norman Ok
Mdt Risk Svr Tstms SE Sd…E Neb…S Mn...N/Cntrl Ia to SW Wi...
Slgt Risk Svr Tstms for N and Cntrl Plains to Mid-Upper Midwest...

Severe Thunderstorms Capable Of Potentially Widespread Damaging
Wind...Very Large Hail And Tornadoes...Will Occur Today Into Tonight
From Parts Of Southeast South Dakota And Central And Eastern
Nebraska Eastward Across Much Of Iowa...Southern Minnesota...Into
Wisconsin.

Of Particular Concern Will Be From Portions Of Northeast Nebraska Into Adjacent Parts Of South Dakota And Iowa That Afternoon And Evening...Where A Few Significant And/Or A Violent Tornado In Addition To Large...Damaging Hail And Winds Will Be Possible.

Nrn/Cntrl Plains Into Upper Midwest Through Tonight...

Most Of The Ongoing Forecast Remains On Track.

The Slight Risk Has Been Extended Into Portions Of W-Central Into Central Il.

Additionally...Tornado Threat Appears To Be Increasing Across Portion Of Neb/Far Se Sd And Adjacent Portions Of Ia.

19z Observed Raob From Oax Indicates Strong Low Level Shear With Large Cyclonically Curved Hodograph And Extreme Instability.

With The Added Focus Of An Outflow Boundary From Earlier Convection ...Several Sig Tors And/Or A Violent Tornado Can Not Be Ruled Out.

As Such...Upgrade To 15% Sig Tornado Probabilities Appear Warranted.

Prev Discussion...

Oh Valley To Mid Atlantic This Afternoon/Evening...

Abundant Sunshine And A Modestly Strong Unidirectional Wind Profile May Support A Gradual Intensification Of Storms With A Risk For Locally Strong Wind Gusts.

Additional Strong To Marginally Severe Storms Will Be Possible Over The Mid Atlantic As Forcing For Ascent Is Enhanced By A Weak Vorticity Maximum Currently Over The Upper Oh Valley Which Should Turn Se.

Vertical Shear Will Remain Rather Weak...But The Presence Of A Moist...Moderately Unstable Air Mass May Promote A Few Severe Storms Capable Of Strong Winds.

Cntrl Mt This Afternoon/Evening...

A Series Of Weak Perturbations Will Rotate Around The Parent Upper
Low Over The Pacific Nw...Enhancing Vertical Shear And Forcing For
Ascent Across The Region.

Cool Midlevel Temperatures Coupled With Some Daytime Heating Along An Inverted Trough May Promote Pockets Of Weak Instability And The Potential For Isolated Severe Storms Later Today.

Fl This Afternoon...

Seasonably Cool Midlevel Temperatures In Concert With A Very Moist
Air Mass Will Yield Moderate Afternoon Instability With Mlcape Of
1500-2500+ J/Kg.

Convergence/Uplift Along Developing Sea Breeze Fronts Will Be Augmented By The Presence Of A Swwd-Moving Vorticity Maximum To Foster Scattered To Numerous Afternoon Storms Capable Of Isolated Damaging Wind Gusts.

Wrn Tx This Afternoon/Evening...

Strong Heating Along The Dryline May Support Isolated Tstm Development Later Today Amidst A Steep-Lapse-Rate Environment With Mlcape Of 2000-3000 J/Kg.

While Vertical Shear Will Remain Weak...The Degree Of Instability Will Promote Strong Up/Downdrafts Capable Of Damaging Winds And Large Hail.

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

Isolated To Scattered Storms Producing Wind And Hail Will Be
Possible From The Upper Mississippi Valley And Great Lakes Westward Across The Northern Plains.

A Potent Upper Low Over The Intermountain West Will Slowly Shift
Eastward Across Western Mt On Tuesday.

Strong Deep Layer S/Swly Flow Ejecting Through Attendant Trough Will Overspread The Central Rockies Into The Northern High Plains.

A Moist And Unstable Airmass Will Exist Downstream Of The Upper Low From Ern Mt Across The Northern Plains...On The Northern And Eastern Fringes Of Broad Sfc Low Over The Central Plains.

Severe Thunderstorms Are Expected To Develop In The Vicinity Of A Nearly Stationary Boundary From Eastern Mt Through Srn Nd/Nrn Sd Into Srn Mn During The Afternoon.

An Mcs May Develop Overnight Across Srn Mn And Track E/Se Into Portions Of Ia And Wi.

Downstream Of The Upper Low...A Shortwave Impulse Will Track Ewd
Across Great Lakes And Srn Ontario During The Afternoon And Into Ny
Overnight.

A Moist/Unstable Airmass Will Aid In Maintaining Ongoing Ewd Propagating Mcs Over Wi/Mi Into Afternoon And Eventually Into Wrn Ny/Nw Pa/Ne Oh Into The Evening.

Strong To Severe Storms Capable Of Damaging Winds And Hail Will Be Possible With This Convection.

Ern Mt Into The Wrn Dakotas...

Upslope E/Sely Low Level Flow Along A Sfc Trough Extending From Ern Mt Into Ne Wy And Wrn Sd Will Transport Mid 50s To Near 60 F
Dewpoints Into Ern Mt.

While A Midlevel Cap Should Initially Inhibit Convective Development Into Early Afternoon...Forcing For Ascent Will Increase As A Shortwave Impulse Ejects From Western Upper Trough...Resulting In Falling Heights And Midlevel Thermal Ridge To Shift Ewd And Deamplify.

Thunderstorms Should Develop By Mid To Late Afternoon In The Vicinity Of The Sfc Trough.

Initial Development May Remain Cellular/Discrete...Initially Posing A Large Hail Threat And Perhaps Marginal Tornado Threat.

As Deep Layer Shear And Forcing Increases Into The Evening / Overnight...Convection May Evolve Into A Better Organized Line Into The Wrn Dakotas...With An Attendant Wind/Hail Threat.

Ern Dakotas...Mn...Ia...Wi...

Forecast Here Is More Complex And Perhaps Conditional.

While A Warm/Moist And Unstable Boundary Layer Will Exist... Capping May Suppress Convection Near The W-E Oriented Warm Front/Stationary Boundary For Much Of The Day.

As Forcing Increases Later In The Afternoon Into The Overnight Hours...Isolated Convection May Develop Near The Boundary.

Any Convection Developing Near This Boundary That Can Maintain Semi-Discrete Status Will Pose A Large Hail And Wind Threat As Well As A Tornado Threat.

As A Swly Low Level Jet Oriented Across Ern Portions Of The Cntrl Plains Into Ia Strengthens Overnight...An Mcs May Organize Across Srn Mn And Track E/Se Along Instability Gradient Into Nrn/Ern Ia And Sw Wi.

Wi/Mi This Afternoon...Ne Oh/Nw Pa/Wrn Ny Evening/Overnight...

Model Guidance Continues To Indicate Potential Mcs Ongoing Across
Parts Of Wi/Lower Mi Tuesday Morning.

The Airmass Will Become Moderately To Strongly Unstable With
Strong Sfc Heating Expected Over Srn Lower Mi.

This Should Aid In Maintaining/Strengthening Mcs this Afternoon Across Lower Mi And Srn Ontario.

Damaging Winds And Large Hail Are Possible With This Activity.

Downstream Of Lakes Erie And Ontario...A Similarly Moist/Unstable Airmass Will Be In Place With Sfc Dewpoints In The Mid To Upper 60s F Forecast.

Should The Mcs Be Maintained Across Srn Ontario And Across The Lakes...Strong Winds And Large Hail Will Be Possible During The Late Afternoon/Early Evening Across Ne Oh/Nw Pa/Wrn Ny.

Portions Of The Cntrl/Srn Plains...

Isolated Storms May Develop In S/Sely Low Level Flow Near The Sfc
Dryline From Cntrl Ks S/Sw Into Far Ern Nm/Wrn Tx.

Steep Lapse Rates And Sufficient Deep Layer Shear Will Pose A Marginal Hail Threat.

While Midlevel Flow Is Not Particularly Strong...Deeply Mixed
Boundary Layer And Steep Low Level Lapse Rates May Pose An Isolated Strong Wind Threat As Well.

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Wed Jun 18 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Svr Tstms for N Plains and Upper Ms Valley East to Pa...

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 Western Kansas Into West Texas.

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

An Amplified Upper Trough Is Forecast To Emerge Across The Cntrl And Nrn High Plains Late On Wed...Although The Ecmwf Is A Bit Slower And Keeps The Thermal Gradient Aloft Farther W Than The Gfs Or Nam.

Still...Meridional Flow Aloft Will Overspread The Region...With A Low Pressure Trough Developing From Sd Swd Into The Cntrl High Plains.

Sely Low-Level Winds Will Maintain Substantial Moisture And Instability Over Much Of The Upper Ms Valley Wwd Toward The Sfc
Trough.

To The E...Models Indicate A Shortwave Disturbance May Affect The
Lower Mi To Pa Corridor...Where It Will Be Sufficiently Moist And
Unstable For Strong To Severe Storms.

Ern Dakotas...Mn...Neb...Ia...Wrn Wi...

Areas Of Storms May Be Ongoing Or Form Relatively Early In The Day
Across Srn Mn/Ia Due To Rapid Moisture Advection As 850 Mb Flow
Backs And Increases In Response To The Deepening Low.

These Storms Could Pose A Localized Wind/Hail Threat.

The Greatest Threat Of Severe Should Materialize Over Nd And Nrn Sd By Late Afternoon Coincident With The Strongest Lift Near The Pressure Trough/Cold Front.

This Front Is Not Expected To Move Quickly...And With Backed Low-Level Flow...Supercells May Form In This Area With Large Hail
And A Few Tornadoes.

With Time...Increasing Lift From Warm Advection Should Lead To A Sewd-Moving Mcs Across Mn And Sd...With Other Activity Developing Along The Surging Cold Front Into Neb With Wind And Hail.

Lower Mi And Oh Ewd Into Pa...

A Ribbon Of Low-Level Moisture Will Be Maintained Form The Midwest
Ewd Across The Oh Valley With Wly Sfc Flow And A Weak Sfc Trough.

Models Indicate A Shortwave Disturbance Traveling From Lower Mi Into Pa During The Day...On Srn Periphery Of The Upper Low Over Quebec.

This Suggests There Will Be A Corridor Of Mcs Activity...With Damaging Winds Possible.

Instability Will Be Sufficient...But Not Extreme...Thus Significant Severe Is Not Anticipated.

Unidirectional Profiles Aloft Also Suggest That The Tornado Threat Should Be Low...But Cool Temperatures Aloft Would Still Favor Marginally Severe Hail.

Wrn Ks Swd Into W Tx...

With The Upper Trough Moving Across The Rockies...Some Height Falls Will Affect The Cntrl Plains...And Perhaps The Srn Plains Depending On Which Model Solution Verifies.

Low Pressure Will Be Situated Over Sern Co With A Lee Trough Across The Srn Plains.

Heating And Ample Moisture Should Lead To Isolated Thunderstorms.

Veering Winds With Height Would Create Small...But Favorable Hodographs For A Few Longer-Lived Cells Capable Of Hail...But Predictability Is Too Low For A Slight Risk Given Potential For Upper Trough To Not Extend This Far S.

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Jun 19-23 Convective Outlook
Storm Prediction Center Norman Ok

On Thu/D4...Guidance Is In Good Agreement Depicting An Upper Trough Across The Nrn Plains...And Ejecting It In A Negative-Tilt Fashion Across The Upper Ms Valley.

During This Time...There Will Be Ongoing Precipitation Ahead Of The Primary Cold Front And In Association With Previous Days Convection.

This Should Bring Instability Levels Down To More Modest Levels Compared To Previous Days.

While Some Wind Or Hail Will Be Possible Across Nd...Mn...Ia And Wi...Potential Is Too Low For A Day 4 Area.

From D5 And Beyond...Aforementioned Shortwave Trough May Meander Ewd Toward The Great Lakes...Enhancing Thunderstorm Chances But With Only A Marginal Severe Threat.

Models Agree On A Belt Of 30-40 Kt Midlevel Wly Flow Spreading Across The Nern States...But With Little If Any Focused Severe Threat.

Elsewhere...Upper Flow Will Substantially Weaken Across Most Of The Conus.


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