US Extended Forecast thru Feb 1

...Overview And Preferences...

Albeit With Typical Detail Uncertainties... Model/Ensemble Guidance Is Consistent And Agreeable In Principle With The Idea That The Large Scale Pattern Will Evolve Toward Lower Hgts Aloft Over The West And Gradually Rising Ern Conus Hgts As A Ridge Becomes Established Over The Ern Pac Near 140w Longitude By Late Next Week/Weekend.

Within The Initial Deep/Amplified Ern Mean Trough There Are Still
Meaningful Diffs With A Shrtwv Crossing The East Mid-Week And
Supporting One Or More Wrn Atlc Sfc Waves... But Somewhat Better
Consensus With An Upstream System That May Reach Or Track N Of The Grtlks By Thu.

Solns Remain Varied With Ern Pac Energy Moving Into The West During The Latter Half Of The Period.

From Day 3 Tue Into Day 5 Thu The 12z Ecmwf Mean Is Preferred As The Starting Point For The Fcst As It Provides The Most Consistent Soln Off The East Coast And Is Reasonably Close To The Avg Of Operational Models With The Upstream System.

Days 6-7 Fri-Sat Employ A 70/30 12z Ecmwf Mean/18z Gefs Mean Weighting To Reflect The Most Agreeable Large Scale Evolution Sfc/Aloft While Awaiting Resolution Of Less Confident Details.

...Guidance Evaluation...

Another Day Of Data Still Leaves More Spread Than Desired With The
Evolution/Timing Of Ern Conus Shrtwv Energy And Assoc Wrn Atlc Low Pressure Around The Middle Of The Week.

The Past Couple Ecmwf Runs Are Not Quite As Far Wwd With The Sfc System And The 12z/00z Cmc Runs Are Not Far From The 12z Ecmwf Mean Track.

The 12z Gfs Was Close To This Track Though A Bit On The Slow Side... However The 18z/00z Runs Have Adjusted Faster Perhaps Due In Part To Becoming Faster With Its Upstream System.

The Ecmwf Mean Has Been The Most Stable Soln Over The Past 2-3 Runs And Is Preferred Given The Spread And Inconsistency Of Operational Guidance.

Although The 18z/00z Gefs Means Are Somewhat Ill-Defined At The Sfc... Their Mid Lvl Fcsts Add Support For Leaning To The Middle/Wrn Side Of The Spread.

Models Are Gradually Trying To Converge With The Next System Which Should Track Near Or N Of The Upr Grtlks By Day 5 Thu.

Recent Gfs Runs Have Been Waffling On Either Side Of Consensus... The 12z Run On The Slow Side And 18z/00z Runs Becoming Fast After Being Comparable To The 12z Ecmwf Into Wed.

The 12z Ecmwf Mean Has Support From The Latest Gefs Means For Frontal Timing While A Nudge Toward The 12z Ecmwf Is Reasonable For The Track Of The Anchoring Sfc Low.

There Is Still A Fair Amount Of Uncertainty/Spread Over The Exact
Shape And Timing Of Ern Pac Energy Fcst To Move Into The West By
Fri-Sat.

This Favors An Emphasis On The Ensemble Means Which Have
Been Fairly Stable And Similar Over The Past Day.

Teleconnections Relative To The Strong Core Of Positive Anomalies Over Nrn Alaska By D+8 Hint At The Potential For Slightly Flatter Mean Flow Than Depicted In The Guidance But Currently Enough Ern Pac Ridging Develops By The End Of The Period To Support The Consensus Soln.

Downstream From This Energy Is A Potential Wild Card In The Form
Of An Upr Low That May Form Near Srn Baja Calif And Eventually Be
Kicked Newd.

So Far Only Recent Gfs/Ukmet Runs Depict Such A Feature. Prefer To Lean Away From That Scenario Until Seen In More Guidance.

...Sensible Weather Highlights...

Expect Tue-Wed To Be Extremely Cold Over The Ern Half Of The Conus With A Sizable Area Seeing Min/Max Temps 15-30f Or So Below Normal... Which May Approach Or Exceed Daily Record Values At Some Locations.

Temps Will Moderate Thereafter Though Nrn/Ern Areas May Still Remain Somewhat Below Normal.

Meanwhile The Srn Half-2/3 Of The West May See Scattered Record Highs With Max Temps Up To 10-20f Above Normal Through Thu But Trending Cooler Thereafter As Flow Aloft Flattens.

This Trend Aloft Will Promote A Greater Flow Of Mstr Into The West... Mostly Lgt-Mdt Pcpn Cntrd Over Nrn/N-Cntrl Areas.

Farther Ewd The Potential Exists For A Band Of Wintry Pcpn Near The Sern/Srn Mid Atlc Coast Around Mid-Week Depending On The Track/Timing Of A Wrn Atlc Frontal Wave.

Also Anticipate A Period Of Rnfl Farther S Over Fl In The First Half Of The Period.

Snow Should Continue Downstream From Unfrozen Parts Of The Grtlks With The Thu System Providing A Period Of Synoptic Scale Snow.

Increasing Gulf Inflow May Support An Expanding Area Of Pcpn From The Wrn Gulf Coast/Lwr Ms Vly Newd By Fri Or Sat.

Significant Detail Diffs Aloft In That Time Frame Lower Confidence In Placement /Intensity Of This Pcpn.


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