US Extended Forecast thru Dec 19

The Medium Range Will Be A Transition Period From A Ridge/Trough
To Trough/Ridge Across The Conus... Amid A Progressive Flow.

Polar Vortex Should Reorganize/Reform Over Far Northern Canada /Nunavut/ With Ridging Again Developing Over The Northeast Pacific Into The Gulf Of Alaska.

he Models Are In A General Synoptic Agreement But Their Reliability Drops Off Around Tue/D5 As The Swift Flow Invites Many Timing/ Amplitude Differences To Appear.

Relative/Normalized Ensemble Spread Starts Out Near To Below
Average/Recent Over Much Of The Conus But Then Increases To Above Average/Recent Over The West And Into The Central Conus By
Wed-Thu/D6-7 Per The Gefs/Ecmwf Ensembles... Respectively.

An Increased Reliance On The Ensemble Means Especially By
Wed-Thu/D6-7 Proved To Be A Best Middle Ground Considering The
Much Larger Sensible Weather Spread As Compared To The 500mb Or Pmsl Spread.

Slowly Moderating Trough In The East Will Swing Through Two
Relatively Minor Systems With Precip Confined To The Great Lakes/ Northeast Region And A Modest Fall/Rise Behind/Ahead Of Each
Cold Front... Respectively. Temperatures Should Rise Toward Climo
By Midweek After Several Chilly Days.

Of More Significance Will Be How The Western Trough Evolves Later
In The Period Downstream Ridge Amplification In The Ne Pac...
Which Has Not Been Handled Well By The Gfs/Ecmwf In Recent Runs
West Of About 95w.

In-House Model/Ensemble Flip-Flop Tool Shows Large Timing/ Amplitude/Orientation Differences Over The Past Few Cycles Especially In The Ecmwf... And Then The Gfs.

The Gefs Actually Shows Less Noise Than The Ecmwf Ensembles... But The Ecmwf Ensembles Often Handle An Amplified Pattern Better.

With Many Conflicting Signals... A 50/50 Gefs/Ecens Blend Was Used By Thu/D7 Which Allows Another Cold Airmass To Begin To Sneak Across The Us/Canadian Border.

Only Real Precip Of Interest Should In The Pac Nw And Northern Rockies As Shortwave Energy Pushes Through The Region.


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