US Final Extended Forecast thru May 16

...Overview And Preferences...

Continue To Expect A Transition From Amplified Flow Featuring High
Predictability Early In The Period Toward A Flatter Regime With Lower Fcst Confidence As More Zonally Oriented Pacific Flow Extends Ewd Across The Nrn Conus/Srn Canada By Tue-Thu.

A Blend Of The 06z Gfs/00z Ecmwf Provides A Good Representation Of The Ern Pac Trough/Wrn Noam Ridge/Ern Noam Trough Pattern Days 3-4 Sun-Mon. Thereafter An Even Blend Of The 00z Gefs/Ecmwf Ensemble Means Cancels Out Some Shrtwv Phase Diffs That Develop... While Also Accounting For Typical Ecmwf Ensemble Mean Verification Versus Teleconnection Considerations That Could Offer A Little More Support For The Gefs Mean.

This Soln Provides Decent Continuity In Light Of The Uncertainty In Some Aspects Of The Fcst Later In The Period.

...Guidance Evaluation...

Aside From Minor Detail Diffs Model/Ensemble Solns Agree Quite
Well From The Ern Pac Ewd Into The Wrn Atlc From Day 3 Sun Into
Day 4 Mon. Thus An Operational Consensus That Is Most Simply
Represented By The 06z Gfs/00z Ecmwf Provides The Most Reasonable Fcst For First Two Days Of The Medium Range Period.

Multiple Complexities Arise From Late Day 4 Onward. Models/ Ensembles Still Disagree Over Exactly How Much Separation May Occur With The Energy Nearing The West Coast On Mon.

The 00z/06z Gfs Runs And 06z Gefs Mean Maintain A More Phased Trough Than Most Other Solns As Well As A Number Of Earlier Gfs Runs. As A Result The Latest Versions Of The Gfs Lean A Bit On The
Amplified Side Of The Spread With The Trough As It Continues Ewd
Across The Nrn Half Of The Conus.

By Day 7 Thu The 00z Ecmwf And Weaker Ecmwf Mean Hint At A Ridge Over The Ern Pac And Trough Along/Just Inland From The West Coast... While Recent Gefs Means Show A Nearly Opposite Configuration. Over The Ern Half Of Noam At That Time The Ecmwf/Ecmwf Mean Display A Flatter And Faster Ern Canada/Nern Conus Trough Versus The Gefs Means.

For The Second Day In A Row The Majority Of Multi-Day Means By D+8
Emphasize A Negative Hgt Anomaly Center Just N Of Alaska And A
Positive Center E Of The Canadian Maritimes. Teleconnections
Relative To These Features Favor An Ern Canada Trough Extending
Swd Along The E Coast Of The Conus... Weak Mean Ridge Over The
Interior West... And Generally Broad Cyclonic Flow Over The Ern
Pac. Extrapolation Of The Gefs Mean Beyond Day 7 Thu Better Fits
The Teleconnection Favored Pattern And Has Support From The
Canadian Mean So It Appears Reasonable To Give It Half Weighting
With The Ecmwf Mean That Has Verified Best On Avg Over Recent
Months. Fortunately Sfc Diffs Between The Two Means From The Ern
Pac Into Wrn Noam Are Less Noticeable Than Those Aloft By Day 7.
The 00z Gefs Mean Was Favored Over The 06z Version Due To
Consensus Handling Of Shrtwv Energy Nearing The West Coast Day 4 Mon And Srn Canada Sfc Low Track Closer To Other Solns/Continuity.

Based On Ensemble Mean Prefs Toward Less Amplified Nrn Stream Flow Than The 00z/06z Gfs During The Latter Half Of The Period...
Expect The Upr Low Over Nwrn Mexico To Lift Newd Into The Plains
Somewhat Slower With Less Stream Interaction.

...Sensible Weather Highlights...

Expect Many Areas From The Interior West Into The Nrn-Cntrl Plains
To See Very Warm Temps Sun-Tue. Potential Exists For Daytime
Highs To Reach At Least 20f Above Normal At Some Locations Near
The Nrn Rockies On Sun And Nrn Plains On Mon. The Northwest Will
Moderate After Sun And Temps May Trend A Little Less Above Normal
Over The Remainder Of The West By Wed-Thu.

Ern Areas Should See A Modified Form Of The Wrn-Cntrl Warmth By Wed Or Thu... After A Couple Days Of Temps 10f Or More Below Normal Sun-Mon.

The Two Favored Areas For Pcpn With Greatest Confidence Will Be From The Pac Nw Ewd In Assoc With The Front Crossing The Nrn States During The Period... And Over The Rio Grande Vly. There Is Greater Uncertainty With The Rnfl Pattern Over The Plains/Ms Vly By Next Wed-Thu... Depending On Amplitude Of The Nrn Stream And Degree Of Interaction With The Upr Low Tracking Newd From Nwrn Mexico. Current Prefs Lead To Less Phasing Of The Two Streams And Less Coverage/Intensity Of Rnfl Than Fcst By The 00z/06z Gfs Runs.

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