US Final Extended Forecast thru Aug 30

Overview And Preferences...

Guidance Is Stable In Showing A Strong Plains Ridge Aloft With
Troughs Just Off The West Coast And Near The East Coast.

Preferences Continue To Lean In Favor Of The Ensemble Means To
Mitigate Ongoing Spread And Run To Run Variability With Embedded
Shrtwv Details Impacting The Sfc Pattern Across The Nrn Conus And
Srn Canada. The Updated Fcst Blend Incorporates A 70 Pct
Weighting Of The 00z Ecmwf Mean As Some Of Its Details Appear
Somewhat More Consistent Than Recent Gefs Means... While The 06z Gefs Mean Is Favored Over The 00z Version For The Remaining 30 Pct Due To A Slightly Better Fit To What Consensus Does Exist. Detail Enhancements Were Included Where Feasible.

Guidance Evaluation...

The Challenge In Resolving Amplitude And Timing Of Individual
Shrtwvs Flowing From The Ern Pac Trough Around The Plains Ridge
And Into The East Coast Trough Continues To Make It Difficult To
Incorporate A Meaningful Proportion Of Operational Models Into A
Deterministic Fcst.

The 00z Gfs Offers One Of The More Extreme Solns With Its Stg Shrtwv Reaching The Northeast On Day 4 Tue. 06z Gfs/00z Ecmwf Runs Also Offer Some Question Marks With Trailing Shrtwv Energy.

After Trending Weaker In The 12z/22 Run... The 00z Ecmwf Has Returned To Depicting A Rather Stg Sfc Wave Off The Nern Coast By Day 6 Thu Psbly With Some Feedback Influence. One Relative Point Of Agreement Is That Shrtwv Energy Assoc With Ern Pac Tropical Storm Ivo Should Reach The Vicinity Of The Us-Canadian Border/Upr Grtlks By Early Day 4 Tue. Consult Latest Nhc Products For Further Info Regarding T.S. Ivo.

While The Sfc Preference Leans 2/3 Toward The 00z Ecmwf Mean... It
Should Be Noted That The Ecmwf Mean Becomes Slightly Weaker And/Or Wwd With The Plains Ridge Aloft Versus The 00z Cmc Mean And Avg Of Latest Operational Solns By Late In The Medium Range Period. Thus It May Be Reasonable To Incorporate A More Even Weighting Of Guidance Aloft By Days 6-7.

The 00z Cmc Would Be The One Soln To Discard From Any Inclusion As It Develops A Deep/Swd Ern Pac Closed Low More Typical Of The Cold Season.

Sensible Weather Highlights...

Expect Hot And Dry Conds To Persist Over The Cntrl U.S. Near The
Strong Ridge Aloft... With Multiple Days Of Highs At Least 10-15f
Above Normal At Some Locations From The Ern Slopes Of The
Nrn-Cntrl Rockies Into The Mid-Upr Ms Vly.

Areas Of Convection Will Travel Around The Periphery Of The Ridge.

Within The Broad Monsoonal Flow Across The Interior West/Rockies There Should Be A Period Of Locally Heavier To Psbly Excessive Rnfl Assoc With Mstr From Ern Pac T.S. Ivo. The Mstr With This System May Begin To Affect Swrn Areas Immediately Before The Start Of The Medium Range Period.

Some Of This Mstr And Mid Lvl Energy Will Be Incorporated Into The Downstream Flow That Will Favor One Or More Episodes Of Convection From The Extreme Nrn Tier Into The Northeast And/Or Mid

Mid Lvl Impulses Flowing Around The Sern/Srn Side Of The Plains Ridge May Provide Some Local Enhancement To Gulf Coast/ Sern Conus Activity.

Meanwhile The Swly Flow Aloft Ahead Of The Ern Pac Trough May Bring Some Mstr To The Pac Nw Though With A Greater Emphasis On Vancouver Island.

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