FXUS63 KBIS 220321
AFDBIS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
921 PM CST MON DEC 21 2009

.UPDATE...

IT IS A BIT SURPRISING THAT THIS ISENTROPIC EVENT WITH UPPER LEVEL
DYNAMICS THAT ARE WEAK AT BEST IS STILL GENERATING ACCUMULATING
SNOW IN THE AREA. SINCE IT WILL NOT GO AWAY...PRECIPITATION
CHANCES AND QPF NEEDED TO BE UPDATED TO INCLUDE ONGOING SNOWFALL.
OTHERWISE...EARLIER FORECAST LOOKS TO BE SOUND. 

&&

.PREV DISCUSSION... /ISSUED 345 PM CST MON DEC 21 2009/ 

SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT...
ACTIVE WINTER WEATHER REMAINS THE FOCUS OF THE FORECAST WITH ONGOING 
SNOW AND THE THREAT OF A SIGNIFICANT HOLIDAY STORM STILL LOOMING. 
LIGHT SNOW WILL LINGER INTO THIS EVENING...MAINLY ACROSS THE 
SOUTHWEST HALF OF THE FORECAST AREA. HAVE TRIMMED POPS/SNOW AMOUNTS 
TO THE NORTHEAST AS DRY AIR CONTINUES TO WIN OUT ACROSS AREAS FROM 
MINOT TO JAMESTOWN. GETTING MAX REPORTS AROUND 2.5 INCHES IN THE 
MARMARTH AREA IN SLOPE COUNTY...SO 3 TO 4 INCH STORM TOTALS THROUGH 
THIS EVENING STILL LOOK ON TARGET FOR THE SOUTHWEST...WITH LESSER 
AMOUNTS AS YOU HEAD TO THE NORTHEAST THROUGH THE WILLISTON AND 
BISMARCK/MANDAN AREAS. 

LIGHT SNOW WILL BE ON THE INCREASE LATE TUESDAY AS THE NORTHERN 
STREAM TROUGH BEGINS TO HEAD EAST...ALTHOUGH THE MOST SIGNIFICANT 
WEATHER FOR THE REGION WILL HOLD OFF UNTIL LATER WEDNESDAY AND 
ESPECIALLY THURSDAY. ALTHOUGH FINE DETAILS ARE YET TO BE 
DETERMINED...OVERALL MODEL/ENSEMBLE AGREEMENT IS MUCH BETTER 
TODAY...LENDING INCREASED CONFIDENCE THAT AT LEAST THE SOUTHEAST 
PORTION OF THE FORECAST AREA WILL BE UNDER THE GUN FOR HEAVY 
SNOWFALL AND STRONG WINDS AT TIMES FROM LATE WEDNESDAY INTO FRIDAY. 
A STRONG UPPER LEVEL JET...IMPRESSIVE MOISTURE TRANSPORT...AND 
ELEVATED INSTABILITY WILL ALL ACCOMPANY THIS STORM. HEAVY BANDED 
SNOW CROSS-SECTIONS INDICATE A NUMBER OF KEY INGREDIENTS FOR 
SMALLER-SCALE AREAS OF ENHANCED SNOWFALL. THESE DETAILS WILL BE 
WORKED OUT AS THE EVENT UNFOLDS. BOTTOM LINE...THROUGH THURSDAY 
NIGHT...MODERATE SNOWFALL AMOUNTS ARE A GOOD BET OVER NORTHERN NORTH 
DAKOTA...WITH HEAVY SNOWFALL OF 6 INCHES OR MORE POSSIBLE ACROSS 
CENTRAL AND SOUTHERN PORTIONS. THE IMPACTS TO HOLIDAY TRAVEL ARE 
OBVIOUS...AND EVEN HEAVIER SNOWFALL IS EXPECTED TO OUR SOUTH. WILL 
ISSUE ANOTHER SPECIAL WEATHER STATEMENT THIS AFTERNOON...AND WILL 
HAVE TO THINK ABOUT WATCH ISSUANCE OVERNIGHT OR TUESDAY. 

COOL EASTERLY FLOW WILL CONTINUE THROUGH WEDNESDAY WITH PLENTY OF 
CLOUDS AND MINIMAL DIURNAL TEMP RANGES EXPECTED. BY LATE WEDNESDAY 
THROUGH THURSDAY...COLDER NW FLOW WILL BECOME ESTABLISHED...AND SOME 
ADDITIONAL DOWNWARD ADJUSTMENTS MAY BECOME NECESSARY LATE 
THURSDAY...ESPECIALLY WEST...DEPENDING HOW FAST THE HOLIDAY STORM 
PUSHES EAST.

LONG TERM...FRIDAY THROUGH MONDAY
TWO UPPER LEVEL LOWS WILL COVER CENTRAL CANADA AND THE NORTH CENTRAL 
US FRIDAY WITH A SHARP RIDGE OVER THE ROCKIES.  THE ECMWF SHIFTS 
THIS PATTERN SLOWLY EAST WHILE THE GFS MOVES THE RIDGE EAST AT THE 
SAME TIME IT SHIFTS THE NORTHERN LOW DOWN OVER ONTARIO.  THIS WILL 
INITIALLY SHIFT ANY CHANCE OF PRECIP EAST...BUT LEAVES THE LATTER 
PART OF THE FORECAST UNCERTAIN. FOR NOW WILL FOLLOW THE TREND OF THE 
PREVIOUS FORECAST...WITH NO MENTION OF PRECIP...BUT KEEPING TEMPS ON 
THE COOL SIDE OF NORMAL. 

AVIATION...LOCAL RADARS CONTINUE TO SHOW A BROAD AREA OF PRECIP 
ACROSS EASTERN MONTANA AND WESTERN AND SOUTH CENTRAL NORTH DAKOTA.  
SURFACE OBSERVATIONS INDICATE IFR VISIBILITIES FROM ABERDEEN SOUTH 
DAKOTA THROUGH BISMARCK TO DICKINSON.  THE SNOW LESSENS TO THE NORTH 
OF THE LINE...WITH WILLISTON REPORTING 8 MILES AND ESTEVAN 
SASKATCHEWAN 15.  LOOKS LIKE THIS PATTERN SHOULD PERSIST WELL INTO 
THE EVENING HOURS...AND MAY LIFT INTO WILLISTON AND MINOT LATER 
TONIGHT. 

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...KINNEY 
LONG TERM/AVIATION...TSW
UPDATE...SCHECK