FXUS63 KBIS 231001
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
400 AM CST WED DEC 23 2009
.SHORT TERM...TODAY THROUGH FRIDAY NIGHT...
A SHORTER THAN NORMAL AFD THIS MORNING WITH IMPENDING MAJOR WINTER
STORM. MODEL DATA STILL IN GOOD AGREEMENT IN DEVELOPING TWO
SURGES OF SIGNIFICANT SNOWS. THE FIRST IS ASSOCIATED WITH AN UPPER
LOW DROPPING SOUTH FROM CENTRAL ALBERTA. AND THE SECOND IS OVER
THE FOUR CORNERS THIS MORNING. THE FORMER WILL MOVE SOUTHEAST INTO
EASTERN MONTANA TODAY DEVELOPING SNOW ACROSS WESTERN NORTH DAKOTA
THIS MORNING AND THEN EAST DURING THE DAY. SNOW WILL CONTINUE
TONIGHT AND THURSDAY. MAY SEE A LITTLE LULL THURSDAY NIGHT AS THE
INITIAL LOW MERGES WITH THE FOUR CORNERS LOW OVER THE SOUTHERN
PLAINS. IN DOING SO...A MAJOR WINTER STORM OVER THE MIDWEST WILL
DEVELOP CHRISTMAS DAY. THE END RESULT WILL BE FOR A SECOND AND
MORE POTENT SURGE OF SNOW AND WIND TO CENTRAL AND PORTIONS OF
WESTERN NORTH DAKOTA FRIDAY INTO SATURDAY. THUS THE DECISION WAS
TO ISSUE A WINTER WEATHER ADVISORY ACROSS THE WEST AND NORTHWEST
WITH SNOW AND BLOWING SNOW THROUGH 12Z FRIDAY. FOR CENTRAL NORTH
DAKOTA...A WINTER STORM WARNING WITH SNOW AND BLOWING SNOW THROUGH
12Z FRIDAY HAS BEEN ISSUED. A BLIZZARD WATCH HAS ALSO BEEN HOISTED
FOR ALL OF WESTERN AND CENTRAL NORTH DAKOTA FRIDAY INTO SATURDAY.
THIS CAN BE REVIEWED IN SUBSEQUENT SHIFTS. OVERALL THROUGH 12Z
FRIDAY...EXPECT 3 TO 6 INCHES OF SNOW IN THE WEST...4 TO 8 INCHES
CENTRAL...AND 6 TO 12 INCHES FAR SOUTH CENTRAL. ADDITIONAL SNOW
ACCUMULATION LIKELY FRIDAY INTO SATURDAY. AT THE SAME TIME STRONG
NORTHWEST WINDS OF 20 TO 30 MPH WITH GUSTS OF 35 TO 40 MPH WILL
LIKELY CREATE BLIZZARD CONDITIONS. NEEDLESS TO SAY THIS WILL BE A
A PROLONGED EVENT.
.LONG TERM...
MODELS BEGIN IN DECENT AGREEMENT EARLY...BUT QUICKLY DIVERGE DURING
THE EXTENDED TERM. GFS/ECMWF CONTINUE TO SHOW LINGERING SNOW SHOWERS
OVER THE CWA ON SATURDAY...AS THE VERTICALLY STACKED LOW SLOWLY
WORKS EAST THROUGH THE SOUTHERN PART OF THE GREAT LAKES REGION. BY
SUNDAY...THE LOW BEGINS TO OPEN TO THE NORTH AND MOVE QUICKLY
OFFSHORE. SHOULD THEREFORE SEE AN END TO PRECIP CHANCES AS THIS
PROCESS OCCURS...AND RIDGING WORKS ITS WAY IN FROM THE ROCKIES.
BIGGEST ISSUE FOR EARLY IN HOLIDAY WEEKEND WILL BE WINDS. SURFACE
GRADIENTS VERY STRONG THOUGH DEEP DIRECTIONAL LINKAGE IS LACKING.
EARLY NEXT WEEK THE MODELS DIFFER SIGNIFICANTLY IN THEIR SOLUTIONS.
THE GFS BRINGS A CLIPPER SYSTEM AND A CHANCE FOR SNOW TO THE CWA ON
TUESDAY...WHILE THE ECMWF MAINTAINS THE RIDGE AND KEEPS THE AREA
DRY. AS CONFIDENCE IS LOW...HAVE LEFT OUT ANY MENTION OF POPS PAST
SATURDAY.
TEMPERATURES SHOULD REMAIN AROUND SEASONAL NORMALS THROUGH
THE PERIOD...SOME BELOW NORMAL TEMPS EXPECTED BEHIND THE MAJOR STORM
SYSTEM OVER THE WEEKEND...AND THE POSSIBILITY OF A SLIGHT WARMING
TREND AT THE BEGINNING OF NEXT WEEK.
&&
.AVIATION...
VERY MOIST AIRMASS ON EAST SIDE OF INVERTED TROUGH WILL CONTINUE
SOUTHEAST TO EAST WINDS WITH GOOD LOW LEVEL MOISTURE ADVECTION.
MVFR/IFR FORECAST WILL CONTINUE.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM NOON CST /11 AM MST/ TODAY TO 6 AM CST
/5 AM MST/ FRIDAY FOR NDZ003>005-011>013-019>022-034-035-042-045-
046.
BLIZZARD WATCH FROM FRIDAY MORNING THROUGH SATURDAY AFTERNOON
FOR NDZ001>005-009>013-017>023-025-031>037-040>048-050-051.
WINTER WEATHER ADVISORY UNTIL 6 AM CST /5 AM MST/ FRIDAY FOR
NDZ001-002-009-010-017-018-031>033-040-041-043-044.
WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 AM CST FRIDAY
FOR NDZ023-025-036-037-047-048-050-051.
&&
$$
KS/BPN/HW
