US Extended Forecast thru Jun 14

...Thermal Trough To Disperse Across California...

...Overview...

Blocking Upper-Level Ridge Near The Davis Strait Holds The Key To
The Medium Range Pattern...With Much Of The Upstream Wave
Development In The Gulf Of Alaska...Eastern Pacific And Across The
Pacific Northwest Poised To Push Eastward During The Latter Half
Of This Medium Range Package.

...Guidance Preferences...

Overall...The 6/12z Cycle Offered Decent Agreement With Placement / Amplitude Of An Upper-Level Ridge Axis Along 60w---Into Labrador At Day 7.

No Sooner That The Guidance Starts To Reach Consensus...The Ensemble Members Themselves Quickly Attempt To Break Down The Ridge Around Day 8.

Will Have Another Day (2-4 Forecast Cycles) To Assess That Possibility.

Meanwhile...The Lower 48 Should Have A Reasonably Stable Forecast Through Day 7...And The Deterministic 6/12z Gfs/Ecmwf Appeared To Have Utility With A Compact Mid-Level Disturbance Tracking Across The Southern Sierra...With The 'Tuesday' Wave (Mentioned Yesterday) That Separates From The Primary Northern Stream Flow And Sets Out On A Slow Eastward Trajectory From The Confluence Of The Mississippi-Ohio Rivers On Tuesday Night...And With A Pacific Northwest Closed Low/Cold Trough Undercutting The Upper-Level Ridge Axis...Aligned From The 'Lee' Of The Canadian Rockies...Into The Yukon And North Slope Of Alaska.

The 6/12z Deterministic Gfs Actually Looked Better When Compared To The Ecens/Naefs Means Than To Its Own Mean With Its 500mb Trough Axis Along 120w Longitude At Mid-Point Day 6--13/12z.

Usually The Gefs Tends To Be A Faster Solution...But This Deterministic Run And Ensemble Package Supports A Tad More Downstream Ridging/Amplification Over South Central Canada Invof 53n 100w. To Me...That Actually Makes More Sense...Given The Downstream Block In The Davis Strait And A Trough Over Hudson Bay Are In The Way And Will Be In 'No Hurry' To Migrate Through The North Atlantic Towards Greenland.

So At This Point...I Could Make A Case That For Both...The Deterministic Gfs And Ecmwf...An Active Weather Period Is Setting Up Between Seattle...Boise...Bismarck And North To Calgary-Edmonton And Back To The West To Haida Gwaii.

...Sensible Weather Highlights...

Anticipate The Blocky Downstream Pattern Over Eastern Canada Will
Slow Down Any Serious Frontal Progression East Of The Appalachians And Drastic "Cool Down" East Of The Mississippi And South Of The Ohio This Period.

What Additional Cooling Looks To Be With The Presence Of Mid-Level Cloudiness And Areas Of Rain-Cooled Air.

Again...The Gfs/Ecmwf Provide Some Of The Smaller-Scale Details.

The Amplification Of The Pacific Trough After Day 5...Will Generate A Deepening Lee Side Cyclone Between Calgary And Great Falls...With A Gradual Deepening Of The Upslope Flow Across The Northern High Plains...And Allow A Hot/Dry West To Southwest Mid-Level Flow To Set Up Shop From The Four Corners Eastward Into Western Kansas And The Texas/Oklahoma Panhandles.

Normally...When The Pacific Begins To Dig A System Across The Four Corners...And A Diffluent Southwest Flow Streaming Off The Divide Is In The Offing...I Like Looking For An 'Open' Gulf Of Mexico To Generate
Longer-Range Qpf Precision.

But Those Prospects Appear Slim...And With The Upslope Component For The Northern High Plains Appearing To Be A Cooler And Dry Backdoor Front Originating In The Great Lakes...This Tends To Be More Clouds Than Rain (A Moist But Stable Low-Level Moisture Source).

In Particular...The Day 6-7 Qpf Forecast Will Focus On The Means And The Axis Of Confluent East-Southeast Flow To Net Rainfall Totals Along The Missouri Valley Into The Upslope-Favored Areas Of
Wyoming...Montana...Colorado And The Western Dakotas.

Along The West Coast...Great Basin And Across The Pacific Northwest ...One Extreme To Another Seems More The Norm Rather Than Have A Day Or Two Of Transition Between Hot/Dry And Cold/Dry.

In This Medium Range Period...This Appears The Case Except For The San Joaquin Valley...Southeast California And The Desert
Southwest...Where The Cooling Will Be Less Dramatic.

After Day 5...The Deepening Pacific Airmass Should Spread Through Much Of The Region...And Temperatures Should Fall Back At Night Into The 40s...With A Few 30s Across The Northwest States... Including The Great Basin...And Sheltered Valleys Of daho...Montana... Nevada And Oregon.


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