US Extended Forecast thru Nov 30

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Valid 12Z Sat Nov 23 2013 - 12Z Mon Nov 25 2013

***Arctic front will bring coldest weather so far this season***

***Active weather pattern over the Southwestern U.S.***

***Sleet and freezing rain for the Southern Plains***

A highly amplified upper level flow pattern will allow for a large trough
to build over the Central and Eastern U.S. for the weekend.

A huge surface high behind a strong cold front will bring near record cold temperatures for late November from the Great Plains to the Ohio Valley.

It will continue to be quite cold for Texas and the Deep South this
weekend with the front dropping into the southern Gulf of Mexico.

The mild weather is over for the East Coast as well with the front moving off the coast Saturday morning, and very cold weather is expected to arrive on Sunday.

The weather will be active from the Desert Southwest to the Southern
Plains with significant moisture over-running cold air at the surface.

A concentrated area of moderate precipitation is expected over the
Four-Corners on Saturday as a pronounced upper level low slowly moves eastward. Deep moisture transport ahead of this feature, interacting with the surface front, will allow for periods of rain for the lower elevations of Arizona and New Mexico, and heavy snow for the higher elevations, including Utah and Colorado.

Elsewhere, widespread sleet and freezing rain is likely for much of
central and western Texas, along with parts of Oklahoma, as a shallow layer of cold air surges under a warmer layer aloft. Most of this precipitation should be light, but there may be some areas that receive up to a quarter inch of ice accumulation.

Lake effect snow showers are also expected downwind of the Great Lakes this weekend as the Arctic air flows over the warmer lake waters.

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Extended Forecast Discussion
Nws Weather Prediction Center College Park Md
1151 Pm Est Fri Nov 22 2013
Valid 12z Tue Nov 26 2013 - 12z Sat Nov 30 2013

...Continued Stormy Pattern Along Both Coasts...

...East...

Focus In The Medium Range Will Continue To Revolve Around The
Southern Stream Closed Low Exiting The Southern Plains Tue/D3 And Then Phasing... To Some Degree... With Northern Stream Energy
Moving Through The Great Lakes And Northeast.

The Models Are Very Sensitive To The Exact Timing/Strength Of Each System Within Each Stream So The End Results Have And Will Vary For At Least A Couple More Days.

The Odds Seem To Favor A Less Intense And More Elongated System With Multiple Waves Along The Sfc Boundary But That Has Room To Change In Future Model Cycles. The Ongoing Wpc Preference Remains Tied To An Ensemble Mean Compromise Which
Includes Some Details From The Nearby Deterministic Ecmwf/Gfs.

Just About Any Way You Slice It... A Healthy Swath Of Precip Should Fall From The Southeast Into The Mid-Atlantic Coast And Possibly Into New England.

At Least Some Snow Should Fall On The Far Nw Side Of The Precip Shield But This Is Dependent On The Exact Track/Interaction/Thermal Profile.

System Should Pull Away From Maine Late Thu/D5 Allowing Another Cold Airmass To Slide In From The Lakes... With Temperatures Continued Below Normal

...West...

Models And Ensembles Remain In Good Synoptic Agreement With
Another Closed Low Approaching California Toward The End Of Next
Week.

Typical Timing/Strength/Track Differences Are Seen Among The Models/Ensembles Over The Past Few Cycles... So An Ensemble
Compromise Offered A Reasonable Starting Point.

This Should Push Another Cold Front Through Southern California And The Baja Presuming That The Closed Low Continues An Eastward Progression.

The 12z Ecmwf Lied On The Much Slower/Western Side Of The Ensemble Spread Which Would Lessen The Qpf Impact To Southern California Into Arizona.


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