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01/03/11 8:42 PM

#121974 RE: fuagf #121885

all -- major cold outbreak on the way -- at least east of the Rockies

from the current 'Forecast Discussion' out of DFW ( http://forecast.weather.gov/product.php?site=NWS&issuedby=FWD&product=AFD&format=CI&version=1&glossary=1 ):

000
FXUS64 KFWD 032318 AAA
AFDFWD

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
518 PM CST MON JAN 3 2011

[...]

PREV DISCUSSION... /ISSUED 340 PM CST MON JAN 3 2011/

[...]

BEYOND DAY 7...MEDIUM RANGE GUIDANCE CONTINUES TO ADVERTISE A
MASSIVE ARCTIC INTRUSION INTO THE US NEXT WEEK AS AN ANOMALOUSLY
STRONG 500MB RIDGE BUILDS OVER NORTHERN ALASKA. BOTH THE GFS AND
ECMWF BUILD 500MB HEIGHTS TO NEAR 580DM OVER THIS REGION BY
MONDAY. DURING THIS TIME...CROSS POLAR FLOW WILL SET UP ALLOWING
EXTREMELY COLD AIR TO BUILD ACROSS NORTHWESTERN CANADA. THE LATEST
RUN OF THE ECMWF INDICATES A MASSIVE 1069MB SURFACE ANTICYCLONE OVER
WESTERN CANADA ON MONDAY...WHICH IS CONSIDERABLY STRONGER THAN ITS
00Z RUN AND STRONGER THAN THE 12Z GFS WHICH SHOWS A 1063MB HIGH.
THE FIRST SHOT OF SIGNIFICANTLY COLDER AIR WILL MOVE INTO TEXAS ON
MONDAY BUT THE TRULY ARCTIC AIR WILL REMAIN FARTHER TO THE NORTH
AT THAT TIME. WHAT MAKES THIS SETUP SO CONCERNING IS NOT SIMPLY
THE MODEL OUTPUT BUT RATHER THE IMPACT THE BLOCKING UPPER RIDGE
OVER ALASKA WOULD HAVE. THIS WILL ALLOW THE CROSS POLAR FLOW TO
REMAIN IN PLACE FOR SEVERAL DAYS. THE EXTREMELY COLD AND DENSE AIR
OVER WESTERN CANADA EARLY NEXT WEEK WILL LIKELY BE ALLOWED TO
SLIDE SOUTH OVER MUCH OF THE US BY THE MIDDLE OF NEXT WEEK. RAW
MODEL OUTPUT FROM THE ECMWF INDICATES HIGHS ACROSS NORTH TEXAS IN
THE 20S BY WED/THU WHICH IS VERY CONCERNING. PROLONGED
TEMPERATURES THIS COLD WITH COLDER OVERNIGHT LOWS CAN BEGIN TO
HAVE SERIOUS IMPACTS ON SOUTHERN INFRASTRUCTURE SUCH AS PIPES.
WHILE THERE IS SOME INDICATION OF POSSIBLE PRECIPITATION AFTER THE
COLD AIR HAS ARRIVED...THE MAIN CONCERN AT THIS TIME IS WITH THE
TEMPERATURES. THIS SYSTEM BEARS CLOSE WATCHING OVER THE NEXT
SEVERAL DAYS.

DUNN

&&

[...]