US Final Extended Forecast thru Jul 28

...Overview And Preferences...

Expect A Nern Pac Closed Low To Settle Over/Near The Bc Coast
While Farther S A Mean Ridge Generally Cntrd Over The Southwest
Into Srn Plains Should Extend Into Parts Of The Interior West And
N-Cntrl Rockies On Some Days.

Over Ern Noam A Mean Trough Already In Place As Of Wed Is Fcst To Reload With Amplifying Flow Initially To The W/Sw Of Hudson Bay And Energy Rounding The Wrn Ridge Early In The Period.

There Is Currently Sufficient Agreement Among Models/Ensembles To Recommend A Blend Of The 06z Gfs/Gefs Mean And 00z Ecmwf/Ecmwf Mean As The Starting Point For The Fcst. The 06z Gfs/00z Ecmwf Show Some Timing Diffs That Cancel Out In Their Part Of The Blend But The Mdls Still Add Some Detail To The Ensemble Mean Evolution.

...Guidance Evaluation...

The Latest Cycle Of Guidance Displays No Egregious Outlier Solns.
However The 00z Gfs Strays A Little Nwd Of Majority Clustering With The Nern Pac/Bc Coast Closed Low And Develops More Swwd
Amplitude With Nrn Plains Into Mid-Upr Ms Vly Flow Around Late Thu
Into Sat. Some Gfs Runs Have Been Trying To Amplify Flow Over
This Area More Than Consensus And So Far Have Not Had Great
Support From Other Guidance. The 00z Gfs Appears More Reasonable Within The Ern Noam Trough By Day 7 Sun.

The Greatest Uncertainties In The Fcst Will Likely Be Over The
Cntrl-Ern Conus. One Involves How The Energy Rounding The Wrn
Ridge Early In The Period... Assoc With The Upr Low Now Over Nrn
Baja Calif And One Or More Nearby Impulses... Reflects At The Sfc
Once It Emerges Over The Plains. Then There Will Be The Question
Of How Amplifying Nrn Stream Flow Will Interact With This Wrn
Conus-Plains Energy.

Guidance Is Signaling Decent Potential For Hvy Convection Over The Plains By Late In The Week And Defined Sfc Wave. However Mdls Are Occasionally Biased Toward Using Such Convection To Develop A Sfc Low That Is Too Deep Relative To Dynamics Aloft. Inclusion Of Some Ensemble Mean Guidance Helps To Tone Down The Ecmwf Sfc Wave In Particular From The Plains Into Ms Vly. Typical Guidance Errors By The Days 6-7 Time Frame Lead To Fairly Low Confidence In Determining If/When/Where Phasing Between The Wrn-Plains Energy And Nrn Stream Flow Occurs... Though The Fcst Mean Trough Aloft By Day 7 Sun Suggests Maintaining A Well Defined Sfc Wave Into Sun Albeit In Weaker Form Than Given By The 06z Gfs/00z Ecmwf.

By Late In The Period The 06z Gfs May Become A Little Too Fast Sfc/Aloft Over The Cntrl/Ern States While The 00z Ecmwf May Be Slightly Slow Based On Consensus And Lagged Avg Fcst Of Ecmwf Runs.

Ahead Of This Evolution Expect A Complex/Wavy Frontal System Along
The East Coast With A Bndry Extending Back Through The Sern
States/S-Cntrl Plains. It Will Likely Take Until The Short Range To Resolve Some Localized Wave Details. Current Prefs Offer A Good Compromise Over These Areas And With A Front Progressing Sewd From The Nrn Plains Wed Onward.

...Sensible Weather Highlights...

Expect Energy Exiting The West To Support Potential For Some Hvy
Convection Progressing From The Cntrl Plains Into Oh Vly And/Or Tn
Vly Later This Week Into The Weekend.

It Will Likely Not Evolve In The Same Way As Depicted In Latest Model Runs But Enough Consecutive Runs Of Different Models Are Showing This Activity To Merit Attention. Even With The Departure Of This Energy From The West... Anticipate Continuation Of Diurnal Convection With Some Locally Significant Rnfl Over Parts Of The Interior West/Rockies.

Meanwhile A Nearly Stnry Wavy Front Near The East Coast And One Or More Mid Lvl Impulses Aloft Will Support Unsettled Conds Over
Extreme Ern Areas. A Front Progressing E-Se From The Nrn Plains
May Generate Some Convection From The Nrn Plains Ewd. The Most
Notable Anomalies For Daytime Highs Should Be Of The Cool Variety
From The Nrn-Cntrl Plains Spreading Gradually Ewd From Thu Onward Due To Aforementioned Convection And Canadian High Pressure Building Into The Nrn Tier/Ms Vly. Some Locations May See Highs 10-15 F Below Normal On One Or More Days.

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