US Short Term and Extended Forecast thru July 20

Short Range Forecast Discussion
Valid 00Z Sun Jul 14 2013 - 00Z Tue Jul 16 2013

...Heavy rains and thunderstorms are in store for the Southern Plains...

...Flash flooding and severe weather possible across the Dakotas and Minnesota...

Cool and wet weather will accompany a closed low retrograding from the Ohio Valley to the Southern Plains this weekend.

Initially...precipitation will be rather sparse underneath the low...but
by Sunday morning...some moderate to heavy rains with embedded
thunderstorms are expected to develop over portions of Oklahoma and Kansas as the upper low dips more southward into a juicier airmass. These dumping rains...and potential for flash flooding...will gradually shift southwestward Sunday evening/Monday while the upper low slides into Texas.

Showers and thunderstorms will continue to breakout near a frontal
boundary stuck over the northern tier of the country. The best chance for organized convection will be across the Dakotas and into Minnesota. Given the abundance of moisture and instability in place across the region...these storms will have the potential to produce heavy downpours and severe weather.

Wet and stormy will remain the story across the Southeast... Tennessee Valley...and southern Mid-Atlantic states over the next few days. A stalled frontal boundary will serve as a focal point for convection...and storms should decrease in number as the front gradually weakens.

Farther north...conditions will begin to warm up and clear out as a ridge builds in over the northern Mid-Atlantic states. However...daytime heating and upslope flow against the Appalachians could lead to a few scattered showers and thunderstorms across the region.

Monsoonal flow will continue over the four corner states throughout the forecast period. Scattered showers and thunderstorms will be possible over the Great Basin and southern/central Rockies... especially during the late afternoon and early evening hours.

Extended Forecast Discussion
Valid 12z Tue Jul 16 2013 - 12z Sat Jul 20 2013

Few If Any New Wrinkles In The Medium Range.

Expansive Mid-Atlantic Ridge Axis And Bermuda High Will Be The
Prevailing Synoptic Feature In The East.

In The West...Broad Anticyclone And Monsoon Flow Will Be Aided By A Series Of Easterly Wave Migrations From The Western Gulf Of Mexico Into South Central Texas...The Rio Grande Valley And Northern Mexico. Rounding Out The Main Synoptic-Scale Features For The Day 3-7 Forecast Period...Will Be The Unusual H5-H7 Layer Circulation And Its Track Across The Southern Plains.

Model Preferences...

Through Day 5...The Deterministic 13/00z Gfs/Ecmwf Were Reasonable Approximations With The Primary Weather Features...And Were Well Within Their Means. Opted For More Of A Ec Ensemble Mean/Gefs Mean Approach After 5 Day Given The Operational Gfs/Ec And Canadian Began To Deviate With The Depth And Track Of An Upper-Level Low Off The Pacific Northwest Coast And The Southeastward Progression Of A Canadian Cold Front Through The Northeast And Ohio Valley.

Sensible Weather Highlights...

Wetter Than Normal Conditions Expected In The Upper Rio Grande
Valley...Sonora Desert And South Central Texas Interior In
Association With The H5-H7 Layered Circulation. This System
Becomes A 'Hybrid' Of Sorts As It Comes Into Contact With Gulf
Moisture Originating Along The Texas Gulf Coast And The South
Central Rockies.

Seasonal Weather Conditions Expected Across The Gulf Coast... Florida With Deep-Layered Fetch Of Easterlies Channeled Along The Southern Periphery Of The Bermuda High.

Four Corners Anticyclone Remains Intact...Though Monsoonal
Moisture Stream Gradually Drifts Into The Western Cordillera Of
Mexico And Gulf Of California Proper.

Along And South Of The Ohio Valley Westward To The Ozarks And
Lower Missouri Valley...Muggy Conditions Expected With The Least
Rainfall Nationwide Expected To Be In The Central Plains Of Kansas
And Nebraska.

Northern Tier States And Great Lakes...
(Broad Overview Of Conditions) A Series Of Mid-Level Impulses Steered Eastward Along The Northern Periphery Of The Broad Upper-Level Anticyclone Invof The Four Corners Is Expected To Bring Period Of Showers And Thunderstorms (Mcs-Type Nocturnal Rainfall) And A Slightly Cooler Airmass Into The Dakotas And Upper Midwest.

Downwind Over The Eastern Great Lakes...Upper Ohio Valley And Le Of The Appalachians...The Mid-Atlantic States/Northeast...Very Muggy
Weather. Appears The Region Will Be The Graveyard For The Dying
Mcs Clusters Developing Upstream Over The North Central States And Reaching The Central Great Lakes. Likely To Be More Cloud Debris Than Rainfall During This 3 To 7 Day Forecast Period.

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