US Short Term and Extended Forecast thru Jul 19

Valid 12Z Fri Jul 12 2013 - 12Z Sun Jul 14 2013

...There is a slight risk of severe thunderstorms over parts of the
Northern Plains/Upper Mississippi Valley...

...Heavy rain possible over parts of the Upper Mississippi Valley...

...Heavy rain over parts of the Southeastern Coast...

Upper-level low over the Central Appalachians will move roughly westward to the Middle Mississippi Valley by Saturday evening. The energy will trigger showers and thunderstorms over parts of the Mid-Atlantic to the New England Coast and the Southeast/Eastern Gulf Coast through Saturday.

Meanwhile, a quasi-stationary front over the Northern Plains/Upper
Mississippi Valley extending westward to the Northern Intermountain Region will be the focus of showers and thunderstorms over the Northern Plains/Upper Mississippi Valley through Saturday. In addition, monsoonal moisture and diurnal heating will produce showers and thunderstorms over parts of the Central/Southern Rockies and parts of the Southwest/Great Basin on Friday, becoming much reduced on Saturday.

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Valid 12z Mon Jul 15 2013 - 12z Fri Jul 19 2013

...Overview And Model Preferences...

Model/Ensemble Guidance Is In Better Than Average Agreement In
Depicting A Developing 500 Mb Trough Just Off The Pacific Northwest Coast And Downstream Ridge Over The Northern To Central Rockies. This Eventually Merges With A Large And Persistent
Anticyclone Centered Over The Oh Valley And Mid Atlantic Until The
Middle Part Of Next Week Until It Drifts South Into The Tn Valley
By 12z Fri 19 Jul.

This Opens The Door To Lowering Heights South Of The Closed Low
Over Hudson Bay Downstream From The Northern Rockies Ridge And Allows A Cold Front To Move South Form Canada Into The Northern Plains To Upper Ms Valley/Lakes/Northeast Next Thu-Fri 18-19 Jul.

The Model Majority Shows The Upper Low Will Retrograde Move Across The Southern Plains And Into The Southwest By Day 7. The 18z Gfs Broke Continuity By Rotating The Low North Around The Periphery Of The Anticyclone Over The Mid Ms Valley To Oh Valley.
This Makes The 18z A Low Probability Solution With The Preference
To Use The Majority Forecast.

Likewise...The 12z Ecmwf Was Deeper/Higher Amplitude Solution Vs
The Model/Ensemble Majority Off The Pacific Northwest And The 12z
Gfs Was A Fast Solution In Moving This Trough Onshore And Inland.

Given Better Overlap/Agreement Of The 18z Gefs/12z Naefs/12z Ecmwf Ensemble Means...The Manual Forecasts Consisted Of A Consensus Of These Forecasts.

...Sensible Weather Highlights....

500 Mb Heights And 700 Mb Temps Are Fcst To Be 1-2 Std Deviations
Above Normal From The Northern Great Basin To The Northern Rockies...Northern Plains...Upper Ms Valley...Great Lakes And Northeast For Days 3-6. This Provides A Basis For Hotter Than Normal Conditions Until Relief Arrives Around Day 7 Fri 19 Jul As A Cold Front Enters The Northeast To The Great Lakes And Northern Plains.

The One Area With Below Normal Heights And Temps Was Near The
Upper Low Crossing The Southern Plains To The Southwest. Heavy
Rains Are Possible In The Confluence Zone East Of The Upper Low
Across Texas And Adjacent Ok And Nm...Continuing Into Az As The
Upper Low Approaches Next Thu 18 Jul-Fri 19 Jul.


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