US Short Term and Extended Forecast thru Nov 10

Short Range Forecast Discussion
Valid 00Z Mon Nov 04 2013 - 00Z Wed Nov 06 2013

...More snow for portions of the northern and central Rockies...

...Significant rains returning to the southern & central Plains on Tue...

...Below average temperatures for the East tonight and tomorrow...

In the Pacific Northwest, a weakening frontal system nearing the coast is expected to bring light precipitation into the region beginning later today and continuing into Tue.

Meanwhile, a pair of upper disturbances dropping out of western Canada and the eastern Pacific into the western U.S. are expected to produce mainly light snows across parts of the northern and central Rockies.

Across the central U.S., deep southwesterly winds across northern Mexico into the southern Plains are expected to carry moisture associated with tropical storm Sonia, fueling showers and thunderstorms across the Big Bend region on Texas into the central and northeastern parts of the state on Mon.

Precipitation is expected to become more widespread across the southern Plains by early Tue as this moisture becomes further fortified with moisture from the Gulf of Mexico moving inland along the western periphery of an area of strong high pressure centered over the eastern U.S.

Further to the north, a well-defined area of low pressure is forecast to
lift across central Canada, with its trailing cold front moving across the
northern and central Plains. Removed from any deep moisture, a mostly dry frontal passage is expected across these regions until early Tue when the front begins to slow and focus the previously noted moisture from the Gulf that is surging north into the central U.S.

By early Tue, expect moderate to locally heavy rains to develop across portions of the central Plains, mid Missouri and Mississippi valleys.

Further to the west, deeper into the cold air, light to moderate snows are expected across the central High Plains early Tue.

Across the eastern U.S., with the exception of some showers promoted by the onshore flow along the Southeast coast, high pressure and dry conditions are expected through the period.

After a chilly night tonight and day tomorrow, with below normal temperatures up and down much of the East Coast, temperatures will begin to moderate by Tue as the high pressure center shifts east, allowing southerly winds to return to the region.
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Extended Forecast Discussion
Valid 12z Wed Nov 06 2013 - 12z Sun Nov 10 2013

...Overview And Preferences...

Model/Ensemble Guidance Is Furthering The Idea Of Holding Onto
Progressive Ern Pac/Noam Flow Until A Larger Scale Mean Trough
Takes Shape Off The West Coast By Next Weekend In Response To
Strong Upstream Ridging.

Although Recent Gfs Runs And Other Solns Cluster Fairly Well For Most Aspects Of The Fcst Over The Conus And Srn Canada... The Gfs Deviates More From Consensus With A Couple Features Off The West Coast.

Thus Prefer To Use A Blend Of The 00z Ecmwf/Ecmwf Mean And 06z Gefs Mean As The Starting Point For The Days 3-7 Wed-Sun Fcst With Minor Detail Enhancements Where Appropriate.

...Guidance Evaluation...

Although Some Uncertainty Remains... There Is Increasing Agreement Toward Greater Splitting Of Ern Pac Trough Energy In The Late Short Range/Early Medium Range Time Frame. This Ultimately Leads To A Faster/Weaker Nrn Stream Shrtwv Progressing From The West Coast/Vancouver Island Ewd Across The Conus And Srn Canada From Day 4 Thu Onward.

The 06z Gfs Is Farthest Nwwd Of The Primary Model/Ensemble Cluster With The Sfc Low Reaching Vancouver Island Around 12z Thu While The 00z Gfs/Ecmwf Are In The Middle Of The Spread.

By Day 6 Sat There Is Better Than Average Clustering With The Sfc Low Crossing The Upr Grtlks But Confidence In The Fcst Downstream By Sun Is Lower As Finer Scale Details Aloft...
Typically Having Low Predictability At The Day 7 Time Frame...
Will Determine How Much Sfc Development Occurs Off The Coast Of
New England/Canadian Maritimes. A Compromise Between The
Operational Models And Less Defined Ensemble Means Seems Most
Reasonable At This Time.

Over The Ern Pac The 00z/06z Gfs Are Deepest And Farthest Ewd With A Closed Low Dropping Swd Toward 30n Latitude And Late In The Period Pull Nern Pac Closed Low Energy And Assoc Sfc Low Toward The Swrn Side Of The Guidance Spread. Latest Gefs Means Share The Gfs Ideas With The Early Period Closed Low But In Weaker Form While They Lean Away From The Gfs Off The Pac Nw Late In The Period.

Ahead Of The Above Systems There Is Good Consensus For The
Deepening Wave Tracking E/Ne From The Upr Ms Vly/Upr Grtlks Across Ern Canada Wed-Fri... And Trailing Cold Front Crossing The Ern States During Wed-Thu.

...Sensible Weather Highlights...

Cold Front Crossing The Ern States Wed-Thu Will Be Accompanied By A Band Of Mdt To Locally Hvy Rnfl With Highest Amts Expected From The Ms Vly Into The Grtlks Early In The Period.

Rnfl Along The Srn Part Of The Front Should Trend Lighter With Time As Dynamics Aloft Lift Newd And The Front Accelerates.

Expect Upstream Low Pressure Tracking Near The Us-Canadian Border Thu Onward To Bring A Period Of Rain And Higher Elev Snow To The Northwest And Then Spread A Band Of Snow N/Rain S Across The Nrn Tier Into New England. Favored Terrain In The Nw Should See Mdt Amts With Locations Downstream Likely Seeing Mostly Lgt Amts But With Potential For Localized Enhancement Depending On Exact Details Of Evolution Sfc/Aloft.

Mstr Should Return To The Northwest Next Weekend As The Large Scale Trough Aloft Evolves Off The West Coast.

Recent Trends Toward More Progressive Flow Aloft For Most Of The Period Suggest Moderate Temps With Highs Within 10 F Of Normal At Most Locations Through The Period.


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