FXUS63 KMPX 250022 RRA
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
615 PM CST THU DEC 24 2009
.UPDATED FOR AVIATION DISCUSSION BELOW...
.DISCUSSION...
NEXT ROUND OF HEAVIER PRECIPITATION BEGINNING TO SHOW ITSELF ACROSS
W AND CENTRAL IOWA. 700 MB OMEGA FIELD ON 18Z NAM HAS A PRETTY
GOOD HANDLE ON THIS WITH STRONG UVV ACROSS THAT AREA AT 18Z THEN
EXPANDING BACK STRONGLY INTO CWA THIS EVENING AND THRU THE
OVERNIGHT HOURS. FOR THE NEXT 12 HOURS TRIMMED BACK SNOW AMOUNTS
IN WC WI WITH CURRENT METARS SHOWING MIXED PRECIPITATION AND
PROGGED SOUNDINGS...MAINLY OFF THE NAM SHOWING ELEVATED WARM LAYER
THRU MUCH OF THE NIGHT. INCREASED SNOW TOTAL SLIGHTLY FROM THE RWF
AREA THEN THRU ILL AND STC...BUT WITH THIS MUCH SNOW...ANOTHER
INCH OR TWO DOESN'T MAKE MUCH DIFFERENCE.
BJ COOKE 200 MB SNOW TECHNIQUES APPEARS TO HAVE A VERY GOOD HANDLE
ON SNOW SITUATION FOR NEXT 24-36 HOURS WITH B45 WARM POCKET
MOVING INTO S MO BY 12Z FRIDAY AND COLD POCKET ARND B65 OVR N
MN...WITH AN EXCEPTIONALLY STRONG GRADIENT MOVING ACROSS CWA. THIS
WOULD YIELD ANOTHER 10 INCHES OR SO OF SNOW ACROSS MUCH OF CWA.
THE AREA MOST LIKELY TO COME UP A BIT SHORT OF POTENTIAL SNOW
AMOUNTS IS IN WC WISCONSIN WHERE A MIX INTO TONIGHT...AND THEN
WATER EQUIVALENTS MORE IN THE 10:1 RANGE RATHER THAN THE 15:1
EXPECTED FARTHER WEST.
295K ISENTROPIC ANALYSIS YIELDS SNOW AMOUNTS SIMILAR TO COOKE
TECHNIQUE WITH BROAD AREA OF 3-4G/KG SPECIFIC HUMIDITY ACROSS AREA
AND UPGLIDE INCREASING OVERNIGHT AS WINDS BECOME ORIENTED MORE
ORTHOGONAL TO PRESSURE CONTOURS. NICE LIFT CONTINUES THRU MUCH OF
THE DAY ON FRIDAY.
ALL MODELS SIMILAR ON HANDLING OF MAJOR SYNOPTIC FEATURES THRU THE
EVENT WITH SFC LOW SHOWING SOME DEEPENING AS IT LIFTS INTO IA NEXT
24 HOURS AS DOUBLE BARRELED UPPER TROF COMES TOGETHER. SYSTEM
THEN WOBBLES AROUND IA BEFORE FINALLY LIFTING OUT LATER SATURDAY.
BY FRIDAY EVENING SIGNIFICANT SNOW SHOULD BEGIN TO BECOME MORE
DISPLACED TOWARD THE NW AS DRIER AIR WRAPS IN...AS IT COMMON WITH
FILLING LOWS.
SFC WINDS WILL ALSO INCREASE OVERNIGHT AND REMAIN GUSTY ACROSS WC
INTO CENTRAL MN AS PRESSURE GRADIENT TIGHTENS...BUT WILL REMAIN
BELOW THE 35 MPH NEEDED FOR BLIZZARD. WITH DRIER NATURE OF SNOW IN
WESTERN MINNESOTA...STILL DO EXPECT PROBLEMS TO DEVELOP WITH
BLOWING AND DRIFTING.
BOWLING BALL UPPER LOW FINALLY DEPARTS AREA SUNDAY LEAVING US IN
COOL NW FLOW. AS FLOW BECOMES MORE ZONAL ON WEDNESDAY...GFS/ECMWF
SHOW A SHORTWAVE MOVING THRU AREA BRINGING A CHANCE OF -SN.
&&
.AVIATION.../00Z TAF ISSUANCE/
THE TERMINALS STILL REMAIN IN A BIT OF A LULL PERIOD BEFORE THE NEXT
ROUND OF INTENSE PRECIPITATION ARRIVES...IN THE NEXT ONE TO TWO
HOURS OR SO AND CONTINUING INTO CHRISTMAS MORNING. SFC INVERTED
TROUGH EXTENDS FROM A LOW IN ARKANSAS RIGHT UP THROUGH THE KMSP
AREA. THE UPPER LEVEL LOW IS IN SOUTHWEST ARKANSAS MOVING NORTHEAST
AND WILL COMBINE WITH ANOTHER UPPER LOW LOCATED IN NORTHWEST SOUTH
DAKOTA DROPPING SOUTHWARD INTO THE WESTERN HIGH PLAINS. THIS AREA OF
LOW PRESSURE WILL WANDER AROUND THE UPPER MIDWEST FOR THE NEXT 36
HOURS. EXPECT COVERAGE AND INTENSITY OF SNOW TO INCREASE AS THE
EVENING PROGRESSES WITH THE MOST INTENSE SNOWFALL FROM 05 TO 10Z.
EXPECT WINDS TO INCREASE FROM THE NORTH TO NORTHEAST WINDS CAUSING
SOME BLOWING AND DRIFTING OF SNOW. IMPROVEMENT WILL ARRIVE FROM EAST
TO WEST STARTING FROM MID TO LATE FRIDAY MORNING BUT SNOW SHOWERS
WILL CONTINUE...JUST AT A LIGHTER INTENSITY.
KMSP...SNOW COVERAGE AND INTENSITY WILL INCREASE AFT 01Z WITH THE
HEAVIEST PERIOD OF SNOW AFTER 06Z FOR SEVERAL HOURS. SNOWFALL RATES
AROUND AN INCH PER HOUR ARE EXPECTED DURING THIS PERIOD. VSBY
IMPROVES TO 3SM AT 16Z BUT THIS MAY BE TOO OPTIMISTIC. LOWER
CONDITIONS MAY ALSO BE POSSIBLE THAN CURRENTLY FORECAST IN THE 12 TO
16Z PERIOD.
KRWF/KAXN/KSTC...SNOW COVERAGE AND INTENSITY WILL INCREASE AFTER
02Z WITH CONDITIONS AT KSTC SIMILAR TO KMSP. KRWF AND KAXN WILL SEE
THE HEAVIEST SNOW AFT 06Z AND CONTINUE TO 10Z. MAY SEE A 1/4SM +SN
FROM TIME TO TIME. WOULD NOT BE 1/2-1SM SN CARRY ON THROUGH MIDDAY.
KRNH/KEAU...KRNH WILL BE SIMILAR TO KMSP OVERALL BUT SEE HEAVIEST
SNOW ARRIVE AND DEPART A BIT SOONER. AT KEAU MIXED PRECIP WILL BE
THE PROBLEM WITH SLEET...FREEZING RAIN...AND SNOW. SFC TEMPS RIGHT
AT FREEZING AND ARE EXPECTED TO WARM A FEW DEGREES. IF THE LOWER
ATMOSPHERE STAYS WARM ENOUGH THEN PLAIN RAIN MAY EVEN OCCUR. WILL
KEEP THE MIX GOING WITH THE TEMPERATURE PROFILE RIGHT ON THE
THRESHOLD OF THE VARIOUS TYPES. AS A RESULT VSBY MAY BE BETTER THAN
ADVERTISED. THE ATMOSPHERE IS EXPECTED TO COOL OVERNIGHT AS FORCING
INCREASES SO A TRANSITION TO SNOW SHOULD OCCUR PRIMARILY AFTER
MIDNIGHT. MIGHT SEE SOME SLEET MIX IN FRIDAY MORNING.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...WINTER STORM WARNING UNTIL 6 AM CST SATURDAY FOR ANOKA-BENTON-
BLUE EARTH-BROWN-CARVER-CHIPPEWA-CHISAGO-DAKOTA-DOUGLAS-
FARIBAULT-FREEBORN-GOODHUE-HENNEPIN-ISANTI-KANABEC-
KANDIYOHI-LAC QUI PARLE-LE SUEUR-MARTIN-MCLEOD-MEEKER-MILLE
LACS-MORRISON-NICOLLET-POPE-RAMSEY-REDWOOD-RENVILLE-RICE-
SCOTT-SHERBURNE-SIBLEY-STEARNS-STEELE-STEVENS-SWIFT-TODD-
WASECA-WASHINGTON-WATONWAN-WRIGHT-YELLOW MEDICINE.
WI...WINTER STORM WARNING UNTIL 6 AM CST SATURDAY FOR BARRON-
CHIPPEWA-DUNN-EAU CLAIRE-PEPIN-PIERCE-POLK-RUSK-ST. CROIX.
&&
$$
BAP/DRL
