Severe Weather Threat thru Jul 20

Sun Jul 13 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Svr Tstms for Mid Ms Valley Into Ny/Pa...

Scattered Thunderstorms With Sporadic Damaging Gusts And Isolated Hail Are Forecast From Southeastern Missouri Up The Ohio Valley And Into Western Or Central New York This Afternoon.

Other Isolated Damaging Gusts Will Be Possible Over Oregon... Eastern Colorado...And Portions Of The Gulf Coast.

Added A Small Area Of Low Svr Wind Probs To Portions Of The Wrn Gulf Coast In The Vicinity Of The Wwd-Moving Weak Upper Low. Localized Clusters Of Tstms Will Have Some Enhanced Downburst Potential In An Environment Characterized By Weak Vertical Shear ...Pw Values Of Around 2 Inches...And Mid-Level Drying Evident On Water Vapor Imagery Wrapping Around Mid-Level Circulation Which May Serve To Enhance Downdraft Strength.

Minor Ewd Adjustments To The Slight Risk Were Made Over Portions Of Md/Wv/Pa Where Upstream Clusters Of Svr Tstms Have A Somewhat Higher Probability Of Moving Ewd With A Continued Threat For Mainly Damaging Winds.

Isolated Svr Tstms Have Developed Across Sern Wy...Aided By The Approach Of A Weak Shortwave Within Nwly Flow Aloft.

Prev Discussion...

Mid Ms Valley Into Ny/Pa...

A Large Upper Low Over Western Ontario Will Continue To Build Southward Today...With The Primary Surface Cold Front Sagging Southward Across The Great Lakes Region Into The Oh Valley. Moist And Unstable Conditions Are Present Ahead Of The Front From Mo/Il Into Ny/Pa...Where Dewpoints In The Upper 60s And 70s And Afternoon Temperatures In The 80s And 90s Are Expected.

Thunderstorms Are Expected To Develop During The Early Afternoon From Western Pa / Southern Ny Into Ind/Il Along/Ahead Of The Front. This Region Will Experience Mid Level Height Falls And Increasing Winds Aloft Through The Day...Promoting Organized Storms Capable Of Locally Damaging Winds And Some Hail.

Activity Is Expected To Spread Eastward Through The Day Into The Western Mid Atlantic And Oh Valley Regions.

Farther West Along The Surface Boundary...Convection Will Be More Isolated In Nature From Mo Into Ks/Ok. Nevertheless...Steep Low Level Lapse Rates And Moderate Cape May Result In A Few Strong / Severe Storms Capable Of Gusty/Damaging Winds.

Eastern Co...

Scattered Thunderstorms Are Expected Once Again Today Over Parts Of Central And Eastern Co. A Few Of These Storms May Become Organized With A Risk Of Hail And Gusty Winds This Afternoon.

Az...

Water Vapor Loops Show An Easterly Wave Tracking Across Northwest Mexico. Enhanced Easterly Mid Level Winds On The North Side Of The Wave Will Affect Az Today...Along With Sufficient Low/Mid Level Moisture For Scattered Afternoon Thunderstorms. It Appears That The Potential Exists For A More Active Thunderstorm Day Along The Mogollon Rim And Mountains Of Southeast Az. Favorable Steering Flow May Allow Outflows From These Storms To Propagate Westward Into The Lower Deserts This Evening.

This Scenario And Convective Trends Will Be Closely Monitored For A Possible Upgrade To Slight Risk.

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Mon Jul 14 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Svr Tstms for Ozarks/Low Oh/Tn Valley to Mid-Atl States / Southern New England...

Severe Thunderstorms Will Be Possible Primarily Across Parts Of the Ozarks...Lower Ohio Valley ... Tennessee Valley...Mid-Atlantic States and Southern New England On Monday. More Isolated Strong To Severe Storms Will Be Possible From The Southern Plains Northwest Into The Northern Rockies And Across Central And Southern Arizona.

Amplification Of The Large-Scale Upper Air Pattern Will Occur Monday As A Seasonably Strong Upper Level Trough Becomes Established From Ontario/Quebec Swd Across The Great Lakes And Ohio Valley.

A Series Of Impulses Over The Pac Nw/Nrn Rockies Will Move E/Se at the Crest Of A Ridge Of High Pressure Centered Over The Great Basin. A Pronounced Cold Front Will Extend From The Lower Great Lakes Across The Srn Plains Monday Aftn...While A Pre-Existing Surface Frontal Boundary...Reinforced By Prior Convective Outflows... Will Be In Place In Advance Of The Front From Srn New England Sw into Portions Of The Ohio Valley/Ozarks.

Ozarks/Low Oh Valley/Tn Valley to Mid-Atl States/New England...

Showers/Tstms Will Likely Be Present Along The Pre-Existing Composite Front/Outflow Boundary Early Monday And Will Likely Influence Subsequent Tstm Development Later In The Day. However ... An Increase In Tstm Coverage Is Expected Coincident With Aftn Heating Along Both The Swd-Surging Cold Front And The Pre-Existing Boundary As 60-90 Meter Height Falls Develops Across The Great Lakes/Ohio Valley. The Presence Of Strengthening Wind Fields And Heating Of A Moist Boundary Layer With Upper 60s/Lower 70s Dew Points Will Provide A Favorable Environment For Organized Multicells And Line Segments Capable Of Damaging Winds...With A Few Reports Of Large Hail Most Likely Over The Oh/Tn Valley Region Where Greater Instability/Stronger Updrafts Will Be Present.

The Slight Risk Area Was Extended Nwd Across Srn New England Where 35-40 Kts Of Shear Will Be Present By Aftn And Heating Of Lower 70s Dew Points Will Support Mlcape Of 1000-1500 J/Kg. Damaging Winds Are Also Likely With Tstms Along The Frontal Boundary In This Area.

Both Nam And Gfs Guidance Depict Somewhat Stronger Low-Level Winds Associated With A Weak Sfc Low That May Result In At Least Some Risk For A Tornado With Any Semi-Discrete Tstm.

Srn Plains Nwwd To Nrn Rockies...

Isolated To Widely Sctd Tstms Are Expected Driven Mainly By Diurnal Heating And/Or Upslope Flow From The Srn Plains Nwwd Across The Nrn Rockies. Stronger Effective Shear In Association With A Sewd-Moving Shortwave Across The Nrn Rockies May Result In a More Favorable Environment For Organized Svr Tstms.

Southwest...

Ely Flow In The Mid Levels And Strong Daytime Heating Will Allow Tstms Moving Wwd Into The Lower Elevations To Pose A Risk Of Damaging Winds In The Presence Of Steep Low-Level Lapse Rates / Dry Sub-Cloud Layer.

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Tue Jul 15 Convective Outlook
Storm Prediction Center Norman Ok
Slgt Risk Svr Tstms for Carolinas/Southern Va...
Slgt Risk Svr Tstms for parts of Co/Wy...

Isolated Severe Thunderstorms Will Be Possible On Tuesday Across the Central Rockies As Well As The Carolinas And Other Parts Of the Southeast United States.

Longwave Trough Amplification Will Continue To Occur East Of the Rockies On Tuesday...While The Upper Ridge Over the Great Basin Vicinity Modestly Weakens.

Carolinas/Southeast States...

The Region Will Be Influenced By Moderately Strong Cyclonic Upper Flow With One Or More Embedded Shortwave Troughs Likely Overspreading The Region. Some Guidance Variability Exists Regarding the Timing Of A Southeastward-Moving Cold Front And Details Of Preceding Destabilization. However...Expectations Are For A Sufficient Collocation Of Vertical Shear/Buoyancy Near The Front To Warrant A Categorical Slight Risk Across Parts Of The Carolinas / Southeast Va.

Other More Isolated/Marginal Strong To Severe Thunderstorms Will Be Possible Across Additional Parts Of The Southeast States/Gulf Coast Ahead Of The Cold Front. Locally Damaging Winds And Some Hail Will Be The Primary Hazards.

Central Rockies/Front Range...

A Shortwave Trough Is Expected To Spread Southeastward Over The North-Central Rockies On Tuesday Coincident With A Strengthening Belt Of Mid/High-Level Northwesterly Winds. As This Occurs...A Relatively Moist Boundary Layer Will Remain In Place Across The Front Range Vicinity Coincident With Low-Level Upslope Trajectories. Aided By Dpva/Orographic Lift...Thunderstorms Should Steadily Increase/Intensify During The Afternoon Across Much Of Wy/Co.

A Favorable Juxtaposition Of Buoyancy And Vertical Shear Will Allow For Severe Tstms...Including Some Supercells...Capable Of Severe Hail/Wind And Perhaps A Tornado Tuesday Afternoon/Evening.

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Jul 16-20 Convective Outlook
Storm Prediction Center Norman Ok

Relatively Modest Westerlies Coincident With A Weakly Cyclonic / Split-Flow Regime Over The Conus Are Expected Through The Middle Part Of The Week...With Some Re-Amplification/Strengthening of The Northern Tier Westerlies By The Weekend.

On Day 4/Wednesday...Mcs Development/Persistence Appears Possible Across The Southern Plains / Arklatex Vicinity In The Presence Of Moderate Northwesterly Winds Aloft And A Residual Frontal Zone.

At Least Some Severe Weather Potential /Mainly Wind/ Is Possible In This Scenario...But Mesoscale Uncertainties Preclude A 30 Percent Risk Delineation At This Juncture.

With 00z Ecmwf/Gefs Guidance In Relative Agreement...Early Indications Are That Severe Weather Potential Could Increase As Early As Day 6/Friday Across Parts Of Mt...But More So Across The
Northern Plains/Upper Midwest Into Days 7/8 Saturday/Sunday.

In This Scenario...Low-Level Moisture Should Gradually Increase Across The Region Late This Week Near An Amplifying Shortwave Trough And A Southeastward-Moving Cold Front.


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