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Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1600Z Apr 22, 2014)
 
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Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1200 PM EDT TUE APR 22 2014

VALID 12Z FRI APR 25 2014 - 12Z TUE APR 29 2014

...SEVERE WEATHER AND LATE SEASON SNOWS POSSIBLE THIS WEEKEND...

THE PATTERN IS SLOWING AS WE HEAD INTO LATE APRIL. PROGRESSION
SLOWS FURTHER BY SUNDAY AS AMPLIFICATION OF MEDIUM WAVELENGTH
TROUGHS BECOMES A THEME AROUND THE NORTHERN HEMISPHERE. THE U.S.
WILL BE AFFECTED BY AMPLIFICATION OVER NEW ENGLAND AND THE CENTRAL
ROCKIES...BRINGING A SPELL OF CHILLY WEATHER TO THE NORTHERN
ONE-THIRD OF THE COUNTRY. THE AMPLIFICATION OVER THE ROCKIES
RESULTS IN A COLORADO LOW WITH ASSOCIATED HIGHER-END SEVERE
WEATHER POTENTIAL IN THE PLAINS AND LATE SEASON SNOWS PERHAPS
SPILLING OUT OF THE HIGH ELEVATIONS INTO THE NORTHERN HIGH PLAINS
OF THE DAKOTAS AND MT/WY.


...MODEL EVALUATION...

THE FORECAST IS RELATIVELY STRAIGHT-FORWARD...WITH MODEL SPREAD
REDUCED VIA THE PATTERN OF MEDIUM WAVELENGTH CONSOLIDATED FLOW AND
EASILY DEFINABLE SYSTEMS. THE DAYTIME UPDATE TO THE WPC MEDIUM
RANGE PRODUCT SUITE MAINTAINS GOOD CONTINUITY WITH THE PREVIOUS
SUITE...WHILE LEANING MORE HEAVILY TOWARD THE ECMWF AND EC
ENSEMBLE MEAN AND INCORPORATING NONE OF THE 00Z/06Z GFS OR GEFS
AFTER DAY 4. IT WAS AT THAT TIME THAT THE OPERATIONAL GFS BEGAN TO
EXHIBIT ITS FAST BIAS AND THE GEFS MEAN WAS THE LEAST AMPLIFIED OF
ANY MODELING SYSTEM. THE CANADIAN ENSEMBLE CONTINUES TO OFFER A
HANDFUL OF SLOWER SOLUTIONS FOR THE TROUGH IN THE CENTRAL U.S.
THIS WEEKEND...BUT THE OPERATIONAL CANADIAN JUMPED TOWARD THE
ECMWF AND EVEN A LITTLE FASTER...MORE LIKE THE GFS. RUN TO RUN
CONTINUITY IS BETTER IN THE ECMWF AND THE ECMWF OPERATIONAL HAS
BEEN IN STRONG AGREEMENT WITH ITS ENSEMBLE MEAN FOR SEVERAL
CONSECUTIVE CYCLES. THIS...ALONG WITH SHORTWAVE RIDGING OVER
SOUTHERN CANADA...WHICH CALLS FOR A SLOWER MOVING CLOSED LOW IN
THE CENTRAL U.S...HAS US PLACING MORE WEIGHT ON THE ECMWF THIS
CYCLE.


...SENSIBLE WEATHER HIGHLIGHTS...

IN THE EAST...FOLLOWING AN INITIAL WIND SHIFT FROM THE WEST...A
SURGE OF LATE SEASON MODIFIED ARCTIC AIR IS FORECAST DOWN TO
BETWEEN I-70 AND I-40 THIS WEEKEND. THIS WILL ESTABLISH AN EAST TO
WEST BAROCLINIC ZONE THAT DOES NOT BUDGE MUCH THROUGH THE
EXTENDED...WITH BELOW OR MUCH BELOW AVERAGE TEMPERATURES TO THE
NORTH. THE DEEPENING TROUGH IN THE ROCKIES WILL EJECT AND CLOSE
OFF OVER THE CENTRAL PLAINS WHILE ALSO SLOWING BENEATH THE
SHORTWAVE RIDGE UP NORTH. THIS COULD BE AN IMPACFUL SYSTEM.
THERMAL PROFILES APPEAR SUFFICIENT FOR SNOW TO FALL AT LOWER
ELEVATIONS IN MT/WY/SD/ND. SEVERE WEATHER POTENTIAL IS OUTLINED BY
THE STORM PREDICTION CENTER WITHIN THE WARM SECTOR. AND REPEATED
ROUNDS OF MODERATE OR HEAVY RAIN COULD OCCUR DOWNSTREAM FROM THE
SEVERE WEATHER...FOCUSING ALONG THE EAST TO WEST BAROCLINIC ZONE
IN THE LOWER OHIO VALLEY.

BURKE