Severe Weather Threat thru Jul 14

Mon Jul 7 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Svr Tstms for NE US to Midwest/Oh Valley to Cntrl Plains...

Severe Storms -- With Damaging Hail...A Few Tornadoes And Potentially Widespread Wind Damage -- Are Expected To Affect Parts Of Nebraska And Kansas Into Missouri This Afternoon Into Tonight.

Elsewhere...Severe Thunderstorms Are Possible Over A Broad Swath
From The Northern Plains To The Northeast.

Changes Mn/Wi And Ny/Vt...

Lowered Tornado Probabilities Across The Northeast And Southern
Minnesota/Western Wisconsin Areas. Ongoing Convection Will Continue To Pose Wind/Hail And Very Brief/Weak Tornado Threats In These Areas Into This Evening.

Central Plains...

Considered Probability And Categorical Upgrades To Support A Mdt
Risk For Widespread Damaging Winds Over Parts Of Neb/Mo/Ia.
However...Early Afternoon Topeka And Omaha Raobs Suggest That
Moisture And/Or Capping Will Continue To Pose A Challenge For More
Intense Convective Development...At Least In The Short-Term.
Additionally...There Appear To Be A Variety Of Scenarios In Terms Of
Storm Evolution Across The Neb/Ks Areas Through Late Afternoon That Introduce Greater Uncertainty.

Storms May Evolve From At Least Two Different Mechanisms This Afternoon -
1) Activity Increasing Along Residual Frontal Segment Across Eastern Co And Western Ks May Grow Upscale And Pose Wind And Large Hail Hazards East Across Ks And Southern Neb;
2) Shortwave Trough Digging Southeast Across Sd May Sustain Convective Cluster Recently Intensifying Across Southwest Sd.

This Convection May Develop Into A Recovering Airmass Across Neb
Into Late Afternoon With Increasingly Strong Mid-Level West-Northwesterly Flow Contributing To A Forward-Propagating Mcs
With Wind And Hail Potential Into Eastern Neb/Southern Ia And
Northern Mo Into The Late Evening.

It Is Also Possible That A Combination Of Scenarios 1 And 2 Result In Higher-End Damaging Wind Threat Across Parts Of The Mo River Valley Through Late Tonight.

If The Greater Potential For Widespread Damaging Winds Become More Obvious With Time...It Remains Possible That A Mdt Risk Will Be
Issued Given Magnitude Of Instability And Developing Shear Expected
Across Neb/Ia/Mo Areas Through Tonight.

Midwest...

Extended 30 Percent Severe Wind Probability East Across Parts Of Il/Ind For Band Of Multicellular Storms Posing A Downburst Wind Threat Settling Into Corridor Of Strong To Locally Extreme Instability Over These Areas Through Evening.

Prev Discussion...

Nern Conus Swwd Across Oh Valley Region...

Multiple Rounds Of Convection Are Expected Through Period... Starting With Ongoing...Initially Elevated And Non-Svr Activity Over Nrn/Wrn Ny. Srn Fringe Of This Activity May Move Into At Least Mrglly
Sfc-Based Air In Regime Of Heating/Destabilization Effectively
Progressing Nwd Up Hudson Valley.

Otherwise...Tstm Coverage...Intensity And Organization Are Expected
To Escalate Gradually Through At Least Mid-Late Aftn Across This
Corridor...As Cold Front Impinges On This Region And Prefrontal Air
Mass Destabilizes. Bulk Of Convection Actually May Develop Ahead Of
Sfc Front...Within Confluence/Differential Heating Corridor Now
Evident In Vis Imagery From Central Ny To Central Portions of Oh/Indiana.

Tightening Midlevel Height Gradient Related To Mcv Passage Also May Enhance Deep Shear Across Portions Ern Ny And New England Where Sfc Flow May Remain Somewhat Backed Relative To Wlys Farther W. As Such...Will Maintain Relative Max In Supercell Potential And Related Probabilities For A Tornado Or Two Over Parts Of Ny/New England. Dominant Convective Mode...However...Should Evolve To Quasi-Linear With Damaging Wind Comprising Bulk Of Svr Reports... And Sporadic Hail Also Possible.

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Tue Jul 8 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Svr Tstms for Ohio River Valley to Northern Ar...

Severe Thunderstorms With Strong And Damaging Winds Will Be Most Likely On Tuesday Along A Corridor Stretching From Western And Central Portions Of New York And Pennsylvania...Southwestward Across The Ohio Valley...And Into Northern Arkansas.

Other Thunderstorms Capable Of Strong Wind Gusts And Reduced Visibility In Dust Will Be Possible Across Southern Arizona.

A Broad Zone Of Cyclonic Mid-Level Flow Exists Over Much Of Southern Canada And The Northern States...From The Dakotas Across The Great Lakes Region.

The Mid And Upper Flow Across The Great Lakes Will Undergo Amplification Through Tuesday. This Process Appears To Result From The Merger Of A Number Of Smaller Shortwave Disturbances
Embedded Within The Cyclonic Flow And Currently Tracking
Southeastward From Mt And The Southern Prairies Of Canada.

The Strongest 500mb Height Falls...Around 30-40m Per 12h...Are Forecast To Spread From The Upper Midwest To Eastern Great Lakes Through Tuesday Evening...Coincident With A Cold Front Advancing Across These Areas.

The Western Portion Of This Cold Front Will Extend From The Confluence Of The Oh/Ms Rivers Westward To Near The Ks/Ok Border.

Much Of The Surface Front Over These Areas Will Be More Removed From The Modest Large Scale Ascent And Faster Flow Aloft And Thus Settle Only Gradually South-Southeastward Over These Areas Through Early Wednesday.

Elsewhere...Breakdown In Upper Ridging Is Forecast Across The Northwest As A Short Wave Trough Develops Inland From The Northeast Pacific. Upper Ridging Will Persist Over The Nrn Rockies/Great Basin Areas While Weak Mid/Upper-Level Easterly Flow Is Forecast South Of The Four-Corners Region.

Northeast Oh Across Western Ny/Pa...

In The Wake Of Decaying Weak Frontal Passage Across These Areas
During The Day 1 Period...A Stronger Front Is Forecast To Evolve
Through Early Tuesday As Mid/Upper Flow Amplifies And Strengthens
From Lower Mi Across Oh And Lake Erie.

A Plume Of Steeper Mid-Level Lapse Rates...Currently Spreading East Across The Lower Oh Valley...Should Immediately Precede The Front And Stronger Height Falls And Contribute To A Corridor Of Stronger Mlcape In The Range Of 1500-2000 J Per Kg Extending From Southern And Eastern Oh Into Western Ny/Pa By Tuesday Afternoon.

Forcing Near And Ahead Of The Front...In Addition To A Frontal Wave Possibly Evolving Near Southern Lake Erie...Will Support Strong To Severe Storm Development Amidst Strengthening Mid-Level Flow And Shear.

Organized Line Segments And Possibly Even A Couple Of Supercells Are Possible Along With Attendant Threats Of Damaging Winds And Hail. Greater Tornado Potential May Evolve If A Frontal Wave Tracks Preferentially Into/Across Zone Of Stronger Surface-Based Instability And Promotes Backed Low Level Flow And Focused Area Of Higher Storm-Relative Helicity...From Northeast Oh To Near Western Ny/Pa Border...Around The Time Of Maximum Heating/Destabilization.

Oh/Wv West-Southwest Along/South Of Oh River To Northern Ar...

Much Of This Region Should Reside Beneath Aforementioned Plume Of Steep Mid-Level Lapse Rates Emanating From Central Great Plains. Daytime Heating Will Contribute To The Development Of Strong To Locally Extreme Destabilization With Mlcape Of 2500 To 4000 J Per Kg. A Belt Of Stronger Mid-Level Flow On The Order Of 50kt Will Accompany Trough Amplification Across Oh/Wv/Ky Through The Evening And Should Result In Organized Storms In The Form Of Fast-Moving Line Segments...And Perhaps Some Supercells... Evolving Through The Late Afternoon And Early Evening Hours. Large Hail And Damaging Winds Appear To Be The Primary Hazards With This Activity.

Farther West...From Southern Ind/Western Ky Westward...Stronger
Capping...In Addition To Relatively Weaker Forcing And Deep-Layer
Shear...May Delay Onset Of Storm Initiation And/Or Limit Storm
Coverage. Nonetheless...Locally Extreme Instability And Hot Surface
Temperatures In The Upper 80s To Near 90f...Should Compensate For Limitations In Shear And Forcing To Support Wind Damage Potential From Activity Developing And Possibly Consolidating Near/Along The Front.

Ozarks West Across Northern Ok...

While Strong Capping In These Areas May Also Delay Storm Initiation ... Weak Convergence And Heating Near Quasi-Stationary Front May Be Sufficient For Isolated Development By Evening With Some Potential For Downburst Winds. Greater Potential May Evolve After Sunset As Nocturnal Low Level Jet Strengthens And Enhances Mass Transport And Lift Across The Boundary. Locally Heavy Rainfall Could Occur With This Scenario...In Addition To Some Damaging-Wind/Marginal Hail Potential...Through Early Wednesday Morning.

Southwest...

Monsoon Moisture And Intense Heating Will Contribute To Strong
Destabilization Across Much Of Srn Az On Tuesday Beneath Weak
Easterly Flow In Mid-Levels. Storms Initiating On The Higher Terrain
Of Southeast And Central Az Will Have Some Potential For Spreading
West And Possibly Growing Modestly Upscale. At Least A Local
Strong/Damaging Wind Threat Appears Possible Along With The Chance For Reduced Visibility In Blowing Dust.

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Wed Jul 9 Convective Outlook
Storm Prediction Center Norman Ok
No Svr Tstm Areas Forecast...

Relatively Isolated Severe Thunderstorms Will Be Possible On Wednesday Across Parts Of The South-Central And Southeast United
States...In Addition To Portions Of The Southern Rockies And Central
High Plains.

A Moderately Strong Belt Of Westerlies Will Extend Over The
Northwest/North-Central Conus And Canada East-Southeastward To The Great Lakes And Northeast/Mid-Atlantic States On Wednesday.

Mid-Atlantic/Southeast States And Carolinas...

Relatively Strong Cyclonic Upper Flow Will Overspread The Region
Coincident With The Entrance Region Of A Northeast States Upper Jet. The Exact Degree Of Destabilization Is A Bit Uncertain...But A Sufficient Combination Of Moisture/Buoyancy And Vertical Shear Will
Allow For At Least An Isolated Potential For Damaging Winds/Severe
Hail Wednesday Afternoon/Early Evening.

Southern Plains/Arklatex To Tn Valley...

Although Upper-Level Forcing And Vertical Shear Will Be Weak /Especially West Of The Tn Valley/...Sufficient Heating/Destabilization Along And South Of A Semi-Stalled Front May Contribute To Pulse-Type Storms Capable Of Locally Damaging Winds And Possibly A Report Or Two Of Hail.

Central High Plains/Northern Intermountain West...

A Weak/Low-Amplitude Shortwave Trough Moving Eastward Over The
Northern Rockies May Contribute To A Few Stronger Storms...While
Other At Least Isolated Strong/Possibly Severe Tstms May Develop
Across The Central High Plains Wednesday Late Afternoon/Night.

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Jul 10-14 Convective Outlook
Storm Prediction Center Norman Ok

Guidance Continue To Generally Feature Prevalent Ridging Over The Western/Southern Conus With Stronger Westerlies Relegated To Canada And The Great Lakes/Northeast States Into The Weekend.

For Days 4/5 Thursday/Friday...Near/Southeast Of A Stalled Front ... Isolated Mainly Pulse-Type Or Multicellular Storms Could Pose A Downburst Risk Across The Southeast States/Carolinas.

While The Stronger Westerlies/Upper-Level Forcing Will Remain North Of The International Border...At Least Some Severe Risk Could Also Exist Thursday/Friday Across Parts Of The Dakotas/Upper Midwest As Moisture Steadily Increases Across The Region Ahead Of A Southeastward-Moving Cold Front.

Although Guidance Variability Increases By The Weekend...Some Severe Risk May Be Possible Across The Midwest Around Days 6/7 Saturday/Sunday.

In Each Of These Cases...A Combination Of Limited Potential / Predictability Precludes Any 30 Percent Severe Risk Areas.


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