US Short Term & Extended Forecast thru Feb 1

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
Valid 00Z Sun Jan 26 2014 - 00Z Tue Jan 28 2014

...Another surge of arctic air for the central and eastern U.S....

...Continued warm and dry for the West....

As the polar jet continues to dip well to the south across the eastern
U.S., temperatures will remain below average across much of the Midwest and eastern U.S.

Another significant reinforcing surge of arctic air is expected early next week, impacting much of the U.S. east of the Rockies.

Early in the period, an arctic cold front extending from the Great Lakes
back through the Ohio valley will continue to advance to the south and
east, with mainly light snows spreading out ahead the front through the middle Atlantic states and Northeast before the front moves offshore Saturday evening.

Snow accumulations are expected to be mainly light, with perhaps the exception of Down East into northern Maine where the inclusion of
Atlantic moisture may fuel some heavier totals.

Meanwhile further to the west, light to moderate snows with windy
conditions across the Dakotas this afternoon will shift east through the upper Mississippi valley into the upper Great Lakes tonight-early Sunday as a developing area of low pressure drops out of Canada into the upper Midwest.

Trailing this low will be a strong arctic front that will surge south and east through the central and eastern U.S., reaching both the Gulf and Atlantic coasts on Monday.

This will send overnight lows Sunday night into Monday into the single digits as far south as the central plains to the lower Ohio valley, while temperatures plunge as low as the minus 20s across the upper Mississippi valley.

West of the Rockies, the story remains quite different.

Dry with seasonal to above average temperatures are expected to persist across the region into the early part of next week.

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Extended Forecast Discussion
Nws Weather Prediction Center College Park Md
Valid 12z Tue Jan 28 2014 - 12z Sat Feb 01 2014

...Overview And Preferences...

Models/Ensembles Finally Agree Better In Principle With The
Transitional Idea That The Recent And Prolonged Highly Amplified
Large Scale Pattern Will Evolve Toward Lower Heights Over The West
And Gradually Rising Ern Conus Heights As A Ridge Becomes
Established Over The Ern Pac Near 140w Longitude By Late Next
Week/Weekend...Albeit With Typical Detail Uncertainties.

Within An Initial Deep/Amplified Ern Mean Trough There Are Still
Meaningful Differences With Shortwaves Crossing The East Into
Midweek Supporting One Or More Wrn Atlantic Sfc Waves...But
Somewhat Better Consensus With An Upstream System That May Reach Or Track N Of The Great Lakes By Thu.

Solutions Remain Varied With Ern Pacific Energy Moving Into The Wrn Us Heading Through Next Weekend.

Given Embedded System Emphasis/Timing Uncertainties...Wpc
Medium Range Guidance Was Primarily Derived From A 06 Utc Gfs
Ensemble Mean And 00 Utc Ecmwf Ensemble Mean Blend. These
Ensemble Means Seem The Most Compatable With Each Other And Wpc Continuity Days 3-7.

...Guidance Evaluation...

Another Day Of Data Still Leaves More Spread Than Desired With The
Evolution/Timing Of Ern Conus Shortwave Energy And Associated Wrn Atlantic Low Through Midweek.

The 06 Utc Gefs Ensemble Mean Has Trended Back To A Better Organized Low Pattern And The Ecmwf Mean Remains A Pretty Stable Solution Over The Past Few Days.

An Ensemble Approach Is Preferred Given The Spread And Inconsistency Of Deterministic Guidance...And Commonly Supportive Larger Scale Mid-Upper Level Flow Forecasts Seem To Support Leaning To Its Middle/Wrn Side Of The Low Spread.

Models Are Gradually Trying To Converge With The Energetic System
Which Should Track Near Or N Of The Upper Great Lakes By Day 5
Thu...Albeit With Lingering Model Timing Differences.

The Supporting Shortwave Has Been Trackable In Water Vapor Imagery Leading To Its Running Overtop And To The Lee Of The Amplified Upstream Ridge Aloft Over The Coming Days.

A Still Potent Composite Solution That Is In Line With The Latest Gfs/Ecmwf Ensemble Means Seems Reasonable.

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

This Favors Emphasis On The Ensemble Means Which Have Been Fairly Stable And Similar Recently.

Underneath...A Potential Wild Card Is In The Form Of An Upper Low That May Form Near Srn Baja Calif And Eventually Be Kicked Newd.

Prefer To Downplay That Scenario Given Limited Pattern Nor Common Guidance Support.

...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 Nw/ 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 Great Lakes 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/Lower Ms Valley Newd By Sat.

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


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