Severe Weather Threat thru Aug 2

Sat Jul 26 Convective Outlook
Storm Prediction Center Norman Ok

Mdt Risk Svr Tstms for Cntrl Illinois thru Cntrl & S Indiana –
includes St. Louis...Indianapolis...Louisville & Cincinnati...

Slgt Risk Svr Tstms around the Moderate Risk Area –
Includes much of the Mid Ms & Lower Ohio Valleys...

Severe Storms...Some Accompanied By Very Large Hail...Locally Strong Wind Gusts And A Couple Of Tornadoes Are Expected Today Into Tonight Across Parts Of The Middle Mississippi And Lower Ohio Valleys. One Or More Organized Convective Clusters Capable Of Generating Swaths Of Potentially Damaging Winds May Evolve Late This Afternoon And Evening Across Much Of Central Illinois Into Central And Southern Indiana...Perhaps Reaching The Central Appalachians By Late Tonight.

While Blocking Appears Likely To Remain Prominent Within The Westerlies Across The Higher Latitudes Of North America...Models Indicate Upper Troughing Either Side Of The High Center Over
Interior Northern Canada Will Begin To Undergo Amplification During This Period. As This Occurs... Subtropical Ridging Is Expected To Build Northward Through Much Of The Northern Intermountain Region And Rockies...And The Closed Low...Now Undercutting The Canadian High...Should Dig Southeastward Across The Central Canadian/U.S. Border Area.

Considerable Spread Lingers Within The Various Model Ensemble Output Concerning This Latter Development...But The 12z Ecmwf And 21z Ncep Sref Ensemble Means Suggest That The Remnant Upper Low/Trough Probably Will Not Reach The Upper Midwest Until Late This Evening Or Overnight. While The Main Transition To Strengthening And Increasingly Cyclonic Mid-Level Flow May Not Occur Until Well After Dark Across The Northern Plains And Upper Mississippi Valley...Deep Layer Shear Will Be More Than Sufficient For Organized Convective Development As Weak Mid-Level Height Falls Commence Within The Northwest Flow Regime Preceding It.

Beneath A Remnant Plume Of Very Warm And Capping Elevated Mixed Layer Air Along The Southern Edge Of The Stronger Northwest Flow...Low-Level Moistening Should Continue Across The Lower
Missouri/Middle Mississippi Valleys Into The Ohio Valley. This Is Expected To Contribute To Strong Destabilization Supportive Of Intense Convective Development And The Focus For The Primary Severe Weather Potential Today.

West Southwestward Along An Initial Surface Front Advancing Southward Into The Central Plains... Severe Weather Potential Appears Lower Due To Stronger Lingering Mid-Level Inhibition And Weaker Shear. However...Isolated Strong/Severe Storm Development May Not Be Out Of The Question Near Or Shortly After Peak Heating. Otherwise...Conditions May Also Become At Least Marginally Sufficient For Strong/Severe Storm Development In Response To The Evolving Upper Pattern...Across Parts Of The Upper Great Lakes Region This Afternoon Through Tonight...And Perhaps As Far East As The Lower Great Lakes/Upper Ohio Valley And Central Appalachians By Late Tonight.

Meanwhile...Monsoonal Moisture Across The Higher Terrain Of The Southern Plateau Into Central And Southern Rockies Will Again Support Considerable Thunderstorm Activity Today And Tonight.

Middle Mississippi Into Lower Ohio Valleys...

Convection Allowing Model Guidance Does Not Provide Clarity For This Forecast...Offering A Rather Broad Range Of Possible Solutions. However...A Fairly Consistent Signal Has Been Evident In The Nam And Ecmwf...Among Other Model Output...Suggesting That Potential Exists For The Evolution Of One Or More Organized Mesoscale Convective Systems Across Portions Of The Middle Mississippi Through Lower Ohio Valleys During This Period.

Given The Aforementioned Environment Conditions Anticipated Across This Region By Late Afternoon...Confidence Is Fairly High That A Significant Severe Weather Event Will Be Realized.

Along/North And Northeast Of An Axis Of Strong Surface Heating Across Central Missouri Into Central Illinois...Moistening Beneath The Axis Of Steepest Mid-Level Lapse Rates Will Contribute To Large Cape...Before Inhibition Gradually Erodes. Aided By Forcing Associated With Lower/Mid Tropospheric Warm Advection...Initiation Of Storms May Occur Prior To 21z Across Parts Of Southern Iowa And Northern Missouri. Initially Discrete...A Few Supercells Appear Possible With The Potential For Very Large Hail...Perhaps Tornadoes...Before Activity Gradually Consolidates Into An Organizing Mesoscale Convective System And Develops Southeastward Across Central Illinois And Central/Southern Indiana Through The Evening.

Although More Uncertain...As Initial Activity Continues To Spread Toward The Central Appalachians Overnight...Forcing Associated With The Digging Upstream Impulse May Support Renewed Convective Development Along The Trailing Outflow Boundary Across The Middle Mississippi Valley. At Least Some Guidance Suggests That This Could Evolve Into Another Southeastward Propagating Mesoscale Convective System...In An Environment That Should Remain Conducive To The Production Of Strong...Potentially Damaging Wind Gusts.


Sun Jul 27 Convective Outlook
Storm Prediction Center Norman Ok

Mdt Risk Svr Tstms for much of E Ky...S Oh...And Wv...

Slgt Risk Svr Tstms for Oh/Tn Valleys Ewd thru Mid Atl & New England...

Tornadoes...Damaging Winds And Large Hail Are Expected Across Much Of Eastern Kentucky... Southern Ohio And West Virginia During The Afternoon And Evening. Severe Weather Is Also Expected Across Much Of The Mid-Atlantic And Northeastern States With Mainly Damaging Winds And Hail.

Isolated Hail And Wind Is Also Possible Across Southeastern Arizona.

An Impressive Upper Trough Will Dive Sewd From The Upper Ms Valley Into The Oh Valley On Sunday With Mid To Upper Level Winds Increasing To 60-90 Kt Respectively. At The Surface...The Primary Surface Low Will Take Shape From Lower Mi Into Oh During The Day...With Surface Trough / Front From Oh Swwd Along The Oh River.

Preceding The Cold Front Will Be Clusters Of Storms...Perhaps A Severe Mcs...Over Srn Oh/Wv/Ern Ky In The Morning...And This May Affect Va Later In The Day. Outflow From This Potential Mcs May Aid Tornado Potential Across The Mdt Risk Area Later In The Day When Wswly Surface Winds And Cooling Aloft Strongly Destabilize The Area.

To The E...A Surface Trough Will Also Deepen E Of The Appalachians With S Winds Bringing Atlantic Moisture Nwd Across The Delmarva As Well As Into Srn New England During The Day. An Upper-Level Disturbance May Aid In Relatively Early Severe Storm Development From Ern Ny Into Srn New England With A Second Round Of Storms Occurring Overnight.

Moisture And Lift With A Wwd-Moving Disturbance Across Nrn Mexico/Srn Az May Result In Isolated Hail Or Wind.

Ern Indiana...Cntrl And Ern Ky...Oh...Wv...

A Morning Mcs Is Likely To Traverse This Area And Most Likely Affect The Srn Oh/Ern Ky/Wv Area In The Morning With An Ongoing Wind Threat. Behind This System...The Veered Nature Of The Low-Level Flow Should Allow For Rapid Destabilization With Upper 60s/Lower 70s F Dewpoints As Well As Eventual Cooling Aloft With The Upper Trough.

As Forcing For Ascent Increases During The Afternoon...Storms Should Form Along The Front Over Ern Ind...Wrn Oh...And Into Nrn Ky...Maturing As They Move Esewd Into Ern Ky...Srn Oh...And Again
Wv. Steep Lapse Rates Aloft And Long Hodographs Will Support Robust Supercells With Very Large Hail Likely.

Relatively Low Lcls And Enhanced Srh May Also Support An Appreciable Tornado Threat. A Strong Tornado Or Two May Occur... Although The Precise Area Will Not Be Known Until The Morning Activity Departs And Mesoscale Boundaries Setup.

Wv Into Pa And Nj Late...

A Severe Mcs Is Forecast To Evolve Out Of The Mdt Risk Area...With Damaging Winds And Hail Possible Along The Low Track...Aided By A Strong Vort Max And Enhanced Convergence With The Surface Low. A Tornado Cannot Be Ruled Out With This Activity Due To Better Low-Level Shear Near The Low.

Nrn Va...Md...De...Pa...Nj Late Afternoon Through Evening...

An Mcs Is Likely To Be Ongoing Somewhere Near Wv Sun Morning... And It Is Unclear Whether It Will Persist Into Va And Md During The Day. Even If It Does Not Remain Intact...Outflow Boundaries...As Well As Increasing Convergence With The Lee Surface Trough Should Provide Additional Focus For Severe Storms By Late Afternoon. Shear Profiles Will Become Quite Favorable For Supercells With Time...And Plenty Of Instability Will Be Present To Support Them.

Large Hail Will Be Likely...And A Couple Tornadoes Will Also Be Possible Given Cellular Storm Mode And Modestly-Looping Hodographs. There Is A Strong Convective Signal In Several Models Across Md...Ern Va And De Near 00z.

Ern Ny Into Srn New England...

A Leading Upper Disturbance Is Forecast To Affect Ern Ny Into Srn New England During The Late Morning/Early Afternoon Hours With Moisture Moving Nwd Off The Atlantic. Heating Upstream Across Ny... As Well As Lift Associated With Low-Level Warm Advection Should Result In At Least Isolated Storms. Shear Profiles Would Favor Supercells Capable Of Large Hail And Gusty Winds. Low-Level Shear May Be Weak Thus Any Tornado Threat Should Be Brief And Likely Weak. Other Storms With A Damaging Wind Threat May Approach The Srn Ny Area Late Sunday Night As Activity Develops Across Pa.

Sern Az...

A Weak Disturbance Embedded In The Easterlies Around The Upper High Will Move Wwd Across Nrn Mexico And Affect Srn Az By Afternoon. Meanwhile...Daytime Heating And A Moist Air Mass Will Lead To Mucape Up To 1500 J/Kg With Relatively Steep Lapse Rates Aloft. Ely Midlevel Flow Around 20 Kt Combined With Wly Surface Winds Will Help Maximize Hodograph Length And May Favor A Few Long-Lived Cells Capable Of Hail And Wind. Presence Of Early Convection And Clouds Lends Some Uncertainty To How Much Severe Coverage There May Be.


Mon Jul 28 Convective Outlook
Storm Prediction Center Norman Ok

Slgt Risk Svr Tstms for Far E Carolinas and Extreme Se Va...

Scattered Severe Storms Capable Of Large Hail And Damaging Winds Are Likely For The Far Eastern Carolinas And Across Extreme Southeastern Virginia. An Isolated Wind Threat May Exist Across New England Early...And A Few Severe Storms Are Possible Across The Central Gulf Coast States.

A Surface Low Will Deepen Over New England As The Primary Shortwave Trough Ejects Newd Off The Atlantic Coast. To The Sw...A Surface Front/Trough Will Extend From Far Ern Va Across The Ern Carolinas By Afternoon...Then Wwd Across The Cntrl Gulf Coast States. A Very Unstable Air Mass Will Remain Ahead Of This Boundary ...With Ample Shear For Organized Severe Storms for Ern Carolinas.

Ern Carolinas Into Extreme Sern Va...

Strong Instability Will Develop Ahead Of The Front...And Beneath 40-60 Kt Mid To Upper Level Wly Flow At The Base Of The Upper Trough. Given The Focused Forcing For Ascent...Perhaps Aided By A
Sea-Breeze Near The Coast...A Zone Of Vigorous Convection Is Likely In The Form Of Supercells Or Small Clusters. The Strongest Cells Should Be Capable Of Damaging Winds And Large Hail Up To Golf
Ball/Hen Egg Size.

New England Early...

What Remains Of An Mcs In Association With The Surface Low Will Quickly Move Nwd Across New England...And Forecast Soundings Suggest That These Storms Will Be Decoupled From A Relatively Stable/Cooler Boundary Layer. Still...Shear Profiles Will Be Very Strong At This Time...And A Localized Severe Wind Gust Cannot Be Ruled Out. If A More Unstable/Moist Boundary Layer Can Get Inland And Interact With These Early Storms...A Brief Window For A Tornado Could Exist But Confidence Is Too Low For A Slight Risk.

Cntrl And Srn Ms/Al/Ga...Fl Panhandle And Ern La...

Scattered Daytime Storms Along The Front Are Likely Mainly From Ms Into Ga. Steep Low-Level Lapse Rates And Substantial Instability Despite Marginal Shear Will Support Wind Damage And Hail Potential. A Few Swd-Moving Clusters Of Cells Will Be Possible.

Portions Of This Area May Be In A Minimal Slight Risk In Later Outlooks When Confidence Increases.


Jul 29-Aug 2 Convective Outlook
Storm Prediction Center Norman Ok

A Broad Area Of Cyclonic Flow Will Remain Essentially E Of The Ms River Through The D4-D8 Period ... With An Upper Ridge Centered Over The Four Corners States. High Pressure Will Exist Across The Plains And As A Result...Weak Nwwd Moisture Advection Into The Cntrl And Srn High Plains Will Persist For Daily Bouts Of Marginal / Isolated Severe Hail And Wind Initiating Across Ern Co And Nm.

On D4 And D5...The Tail End Of The Wrn Atlantic Cold Front Will Drift Swd Across Fl And Will Help To Focus Daytime Thunderstorms. However...The Severe Threat Is Low With Only A Few Strong Wind Gusts Expected.

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