Severe Weather Threat thru Jun 2

Mon May 26 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Svr Tstms for W Tx...Far Swrn Ok...

Severe Thunderstorms Will Be Possible Across A Large Portion Of
Western Texas Into Far Southwestern Oklahoma...Mainly During The
Afternoon And Evening.

Elsewhere...Strong Storms Will Be Possible Across Parts Of The Northern High Plains...The Upper Midwest...And Portions Of New England.

A Split Flow Regime Across The Conus Will Feature A Srn Stream
Closed Low Slowly Progressing Ewd Across The Srn Plains.

Stronger Flow Aloft Accompanying A Shortwave Trough Will Overspread The Pac Nw And Nrn Rockies.

Farther Downstream...Upper Ridge Will Shift E Of The Ms Valley... While Broadly Cyclonic Flow Persists Across The Northeast.

Parts Of W And S Tx..

An Upper Impulse Noted In Early Morning Water Vapor Imagery Was
Moving Ewd Across Nwrn Mx...And Is Forecast To Reach The Tx Big Bend Area By Mid-Morning Mon.

Uncertainty Exists About The Prevalance Of Convection Developing In Conjunction With This Feature Across W/W-Cntrl Tx...Which Will Have Implications On Position Of Key Mesoscale Features /E.G. Outflow Boundaries/.

A Slight Ewd Displacement Of The Persistent Closed Mid/Upper-Level
Low Into The Srn High Plains Will Occur.

Midlevel Swlys Attendant To Surrounding Area Of Cyclonic Flow Are Forecast To Be Slightly Stronger Today Than Previous Days /E.G. 40 Kts At 500 Mb/.

A Moist Boundary Layer Is Already In Place...And With At Least Modest Sfc Heating /Temps 70s-80s F/...Mlcape Values Ranging From 1000-2000 J/Kg Appear Likely In Areas Unperturbed By Morning Convection.

Ample Deep-Layer Shear Of 35-45 Kt Will Be In Place To Support Supercells.

Convective Initiation Will Likely Be Focused Along Preexisting Outflow Boundaries Invof The Tx Permian Basin/Edwards Plateau Toward The Middle Rio Grande Valley.

A Sharper Moisture Gradient/Dryline Will Also Exist Across The Tx Panhandle Into Ern Nm...And Should Support Additional Convective Development In Conjunction With Larger-Scale Ascent Attendant To The Upper Low...Contingent On Sufficient Destabilization.

Primary Svr Threat Is Expected To Remain Large Hail Given The Presence Of Steep Midlevel Lapse Rates And Generally Weak Low-Level Flow.

However...The Risk For A Tornado Or Two May Exist With Supercells That Interact Favorably With Outflow Boundaries.

Locally Dmgg Winds Are Also Possible.

Wrn Nd Into S-Cntrl Mt...

Tstm Development Along A Sfc Trough/Cold Front Near The Nd/Mt Border Is Forecast To Occur In Response To Increasing Low-Level Convergence And Modest Diurnally Enhanced Destabilization.

Steep Low-Midlevel Lapse Rates Coupled With Effective Shear Near 25 Kt Could Result In Isolated Instances Of Large Hail And Locally Strong-Svr Wind Gusts.

Farther W...Convection Is Forecast To Develop During The Afternoon
Over The Higher Terrain Of S-Cntrl Mt...Aided By The Glancing
Influence Of A Weak Shortwave Trough Passing Through The Nrn
Rockies.

This Will Occur Amidst Strengthening Flow Aloft...With Tstms Likely To Progress Ewd Into The High Plains.

Deep-Layer Shear Will Be Sufficient For Tstm Organization...But A More Robust Threat Appears Limited By Somewhat Meager Boundary Layer Moisture And Instability.

Small Clusters Or Lines May Reach Sern Mt During The Evening Hrs.

New England...

Glancing Influence Of A Shortwave Upper Trough Passing Through
Nb/Me...Combined With Weak Destabilization...Will Support Isolated
Tstm Development During The Afternoon.

Steepening Low-Level Lapse Rates Via Diurnal Heating Amidst Strong Unidirectional Nwly Winds Could Result In An Isolated Threat For Strong-Svr Wind Gusts...And Perhaps Hail.

Primary Limiting Factors Will Be Marginal Buoyancy And Weak Low-Level Focus For Initiation And Storm Sustenance.

Upper Midwest...

A Weak Cold Front Is Forecast To Slowly Sag S/Ewd Across Ern
Portions Of The Nrn Plains Into The Upper Ms Valley.

Moderate Destabilization /Yielding Mlcape Values Of 1000-1500 J/Kg/ Is Likely To Support Pulse To Loosely Organized Multicell Tstm Development Along The Front...And Perhaps A Localized Threat For Hail Or A Strong Wind Gust...But Very Weak Deep-Layer Shear Will Limit A More Robust Threat.

Farther E...Near/E Of The Upper Ms Valley...Pre-Frontal Low-Level Waa May Result In Tstms Development.

Slightly Stronger Deep-Layer Winds /Swly At 20 Kt/ Will Be In Place... But Magnitude Of A Resultant Hail/Wind Threat Is Uncertain Due To Modest Midlevel Lapse Rates.

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Tue May 27 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Svr Tstms for parts of Srn Plains...
Slgt Risk Svr Tstms for parts of Nrn Plains...

Scattered Severe Thunderstorms With Isolated Wind Damage And Large Hail Are Expected To Develop Across Parts Of The Southern Plains On Tuesday.

Other Marginally Severe Thunderstorms With Strong Wind Gusts May Develop Across Parts Of The Northern Plains.

Srn Plains/Lower Ms Valley...

An Upper-Level Low Will Move Slowly Across The Srn Plains On Tuesday.

At The Sfc...Sely Winds And Dewpoints In The Mid To Upper 60s F Will Be In Place From Ern Ok Swd Across The Ern Half Of Tx.

As Sfc Temps Warm During The Day...Pockets Of Moderate Instability
Along With Scattered Thunderstorm Initiation Should Occur From Ne Tx Swd To The Tx Coastal Plain.

Forecast Soundings At Waco...Austin And Houston Tx At 21z Show Sbcape Around 1200 J/Kg With 35 To 40 Kt Of 0-6 Km Shear.

This Should Be Enough To Support Severe Thunderstorm Development Tuesday Afternoon.

Although Supercell Development Will Be Possible In Areas That Destabilize The Most...Multicell May Be The Dominant Storm Mode Type.

If Several Short Multicell Line Segments Can Merge And Organize Into A Cold Pool...Then A Wind-Damage Threat May Develop Tuesday Afternoon.

Additionally...Low-Level Lapse Rates Near 8.0 C/Km Will Also Support
A Potential For Damaging Wind Gusts.

Nrn Plains...

An Upper-Level Ridge Is Forecast To Amplify Some Over The Nrn Plains On Tuesday.

At The Sfc...A Cold Front Is Forecast To Move Sewd Into Wrn Nd With Dewpoints Ahead Of The Front In The Lower To Mid 60s F.

This Should Result In The Development Of Moderate Instability Across
Parts Of Cntrl And Swrn Nd.

Thunderstorms Appear Likely To Initiate Along The Front Tuesday Afternoon Due To Sfc Heating And Enhanced Low-Level Convergence.

Nam Forecast Soundings For Bismarck And Minot Nd At 21z/Tue Show Mlcape In The 1200 To 1500 J/Kg Range...0-6 Km Shear Of 35 To 40 Kt And Mid-Level Lapse Rates Near 8.0 C/Km.

This Environment Should Support The Development Of Supercells And Large Hail.

However...The Threat Should Remain Isolated Due To The Upper-Level Ridge And The Lack Of Large-Scale Ascent.

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Tue May 28 Convective Outlook
Storm Prediction Center Norman Ok
No Svr Tstm Areas Forecast...

A Threat For Marginally Severe Thunderstorms Capable Of Producing
Hail And Strong Gusty Winds Will Be Possible Wednesday Afternoon
From Central Montana Eastward Across The Northern Plains To Northern Minnesota.

Other Marginally Severe Thunderstorms With Strong Gusty Winds May Develop Across The Texas Coastal Plain And Southwest Louisiana.

Cntrl And Ern Mt/Nd/Nrn Mn...

An Upper-Level Ridge Is Forecast To Build Nwd Across The Nrn Plains On Wednesday.

At The Sfc...A Quasi-Stationary Frontal Boundary Should Be Located From Cntrl Mt Extending Ewd Across Nd Into Nrn Mn.

Sfc Dewpoints Along The Front Are Forecast To Be In The Lower 60s F
Which Should Result In The Development Of Moderate Instability By
Afternoon.

Due To The Upper-Level Ridge...Thunderstorm Initiation Along The Boundary Is Expected To Remain Isolated Wednesday Afternoon.

In Addition To The Moderate Instability...Forecast Soundings Near The Front Late Wednesday Afternoon Show Moderate Deep-Layer Shear Profiles And Steep Mid-Level Lapse Rates.

This May Be Enough For An Isolated Severe Threat In Areas Where Convection Can Initiate.

A Convective Cluster Could Become Persistent Early Wednesday Evening But This Will Depend Upon Mesoscale Influences.

Due To Convective Coverage Uncertainties...Will Leave Severe
Probabilities At 5 Percent.

Tx Coastal Plain/Sw La...

An Upper-Level Low Is Forecast To Move Slowly Across The Lower Ms
Valley On Wednesday And Become Weaker With Time.

A Very Moist Airmass Should Be In Place Along The Coasts Of Tx And La Where Sfc Dewpoints Are Forecast To Be The Upper 60s And Lower 70s F.

As Sfc Heating Takes Place Tuesday...Scattered Thunderstorms Should Initiate Along The Upper Tx And La Gulf Coast With More Isolated Coverage With Swwd Extent.

Although Deep-Layer Shear Is Forecast To Be Relatively Weak...Steep Low-Level Lapse Rates May Be Enough For Marginal Wind Damage Threat With The Stronger Multicells Around Peak Heating.

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May 29-Jun 2 Convective Outlook
Storm Prediction Center Norman Ok

The Ecmwf And Gfs Solutions Begin The Day 4 To 8 Period With An
Upper-Level Low Over The Lower Ms Valley And An Upper-Level Ridge In Place Across The Great Plains.

Southwest Mid-Level Flow Is Forecast Across The Nrn High Plains On Thursday/Day 4.

Isolated Severe Thunderstorm Activity May Develop Across The Nrn High Plains Thursday Afternoon As A Sfc Low Moves Across The Region.

Severe Thunderstorm Development Will Again Be Possible Across The Nrn Plains On Friday/Day 5 Along A Sewd Moving Cold Front.

This Boundary Is Forecast To Move Ewd Toward The Upper Ms Valley On Saturday/Day 6 Where Severe Thunderstorm Activity Will Be Possible Saturday Afternoon.

Both The Ecmwf And Gfs Solutions Develop An Upper-Level Ridge Across The Nrn Plains On Sunday/Day 7 As A The Models Move The
Front Into The Great Lakes Region.

Although Severe Thunderstorm Activity May Occur Along The Front Sunday...The Solutions Differ On Where The Front Will Be By That Time.

Although An Enhanced Area Of Severe Weather During The Day 4 To 8 Period Remains Possible...Uncertainty Remains Too Great To Warrant The Issuance Of A Severe Threat Area For This Outlook.


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