US Final Extended Forecast thru Jun 19

...Overview And Preferences...

The Large Scale Pattern Shows Moderate To Slightly Slower Than Avg
Progression During The Period. Behind A Departing Ern Canada/Wrn
Atlc Shrtwv... A Ridge Over The Ms Vly As Of Early Sat Will Quickly Collapse As Srn Canada/Nrn Tier Conus Flow Evolves Toward An Ern Noam Mean Trough. Meanwhile An Ern Pacific Trough/ Embedded Closed Low Is Fcst To Drift Inland By Next Wed While A Downstream Ridge Builds Into The Plains.

Overall Models/Ensembles Show Reasonably Good Agreement/ Continuity With A Blend Of 06z Gfs/Gefs Mean And 00z Ecmwf/Ecmwf Mean Solns Providing The Best Account For Detail Issues That Tend To Have Lower Predictability In The Medium Range Time Frame. This Yields Relatively Modest Continuity Changes From Prior Issuance.

...Guidance Evaluation...

Within The Agreeable Large Scale Flow... The Greatest Discrepancies Appear With The Sfc Evolution From Just N Of The
Plains Across The Grtlks/Northeast And Sern Canada. These Diffs
Correspond To Uncertainty In How Canadian Flow Will Interact With
A Compact Closed Low Initially To The N Of The Nrn Plains. Based
On Continuity And The Center Of Ensemble Distribution... Prefer A
Sfc System That Is Between The Somewhat Slower/Swrn 00z Ecmwf And Faster/Nern 00z/06z Gfs.

Interestingly By Late In The Period The Ecmwf Mean Actually Becomes Slower Than The Operational Run And Most Other Solns But The Ecmwf Mean Has Been Fairly Consistent With Timing Thus Far. Fortunately The Impact Of These Diffs With The Sfc System Decreases As One Goes Swwd Along The Trailing Front That Extends Into The Plains.

By The Latter Half Of The Period The 06z Gfs Evolution Over Ern Canada Is A Question Mark But Its Ern Conus Trough Compares Better To Consensus Than The 00z Gfs. The Latter Extends Its Trough Farther E/Se While Also Being Stronger/Newd With Its Upstream Ridge.

Good Clustering Exists For The Ern Pac Trough/Embedded Closed Low Drifting Into The West By The Middle Of Next Week. Over The Past 1-2 Days The Gfs/Gefs Mean/Ecmwf Have Generally Trended A Tad Faster While The Ecmwf Mean Has Been Stable. Given Diffs That Are Fairly Small By Day 7 Standards And Well Within Typical Errors At That Time... A General Model/Ensemble Mean Blend Offers A
Reasonable Soln.

A Somewhat Peripheral Source Of Uncertainty By Late In The Period
Is With A Closed Low/Surrounding Flow Extending Into Nrn-Cntrl
Canada. This Feature Has Become Pronounced Only In The Past 12-24 Hrs Of Ensemble Mean Runs. Ecmwf Runs Have Been Indicating Such A Feature In Multiple Runs But Nwd Of The Latest 00z Run. Gfs Runs Before 12z/11 Had Much Higher Hgts Than Currently Fcst. Currently Issues With This Flow Over Nrn-Cntrl Canada Do Not Appear To Have Too Much Impact Through Day 7 Wed But Will Have To Be Watched In Future Runs.

...Sensible Weather Highlights...

Sfc Low Pressure Working Its Way Ewd Over Or Near Srn Canada Along With Its Trailing Front Will Be A Focus For Convection From The
Cntrl Plains-Grtlks Progressing Toward The East Coast During The
Weekend Into Next Mon-Tue.

The Wrn Part Of The Front Will Likely Stall Over The Cntrl Plains... Offering Potential For Multiple Episodes Of Convection In That Region.

Expect Diurnally Favored Convection Over Fl During The Period And A Narrow Band Of Convection From The Rio Grande Vly Into Srn Plains Early In The Weekend.

Trough/Closed Low Aloft Moving Into The West Late In The Period Will Bring Cool And Unsettled Weather Into The Northwest By Next Mon-Wed.

Daytime Highs Should Be Warmest Relative To Normal Over The Cntrl-Srn Rockies Under The Influence Of Ridging Aloft.

By Late In The Period Some Locations May See Highs At Least 10 F
Below Normal Over The Northwest... With Less Extreme Neg Anomalies From The Nrn Tier Into The Northeast One Or More Days.

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