FXUS63 KMPX 051815
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1215 PM CST SAT DEC 5 2009

.UPDATE...

UPDATED FOR AVIATION DISCUSSION BELOW.

&&

.DISCUSSION...
/ISSUED 336 AM CST SAT DEC 5 2009/

UPPER AIR PATTERN QUITE AMPLIFIED AND BLOCKY YIELDING FAIRLY
STAGNANT WEATHER FOR THE FIRST 36 HOURS OR SO. SURFACE RIDGING
OVER THE WESTERN CWA HAS CLEAR LOW CLOUDS AND FLURRIES FROM THAT
AREA. VERY WEAK WAA PATTERN DEVELOPING DURING THE DAY...WILL HELP
CONTINUE TO PUSH LOW CLOUDS/FLURRIES NORTHEAST. MEANWHILE...A WEAK
SFC LOW AND TROUGH WILL RIDE EAST INTO IA/SRN MN BY LATE IN THE
DAY. THIS MAY PROHIBIT TOTAL CLEARING OVER THE NORTHEAST CWA INTO
THE AFTERNOON. HIGH CLOUDS WILL MOVE EAST OVER THE REST OF THE
REGION DURING THE DAY...ASSOCIATED WITH THIS SYSTEM. COLD
START...SOME SNOWCOVER...WILL LIMIT SIGNIFICANT TEMPERATURE
RECOVERY TODAY. WENT A COMBINATION MET/MAV GUIDANCE...WITH THE MAV
BEING WARMEST. 

WEAK TROUGH WILL MOVE EAST INTO WI FOR SUNDAY. CLOUDS SHOULD
GRADUALLY INCREASE/GATHER AHEAD OF NEXT WEAK SHORT WAVE PROGGED TO
MOVE THROUGH THE AREA SUNDAY NIGHT. NAM_WRF REMAINS THE FARTHEST
NORTH WITH ITS DEVELOPMENT OF SNOW INTO SOUTHERN MN DURING THIS
PERIOD. 03Z SREF IS INDICATING BEST POTENTIAL MAINLY SOUTH OF A
MML-RGK-EAU LINE OVERNIGHT. FURTHER MODEL DIAGNOSIS INDICATED 280K
ISENTROPIC ANALYSIS SHOWING NORTHERN EXTENT OF SNOW POTENTIAL
CLOSE TO THIS BNDRY. FULL WIND FRONTOGENESIS WAS PROGGED TO MOVE
ALONG NORTHERN IOWA OFF THE NAM_WRF AND THE GFS WAS SIMILAR BUT
WEAKER. WILL HOLD POPS MAINLY SOUTH OF THIS LINE. SNOW AMOUNTS
EXPECTED TO REMAIN GENERALLY 1-2 INCHES...WITH THE HEAVIEST
AMOUNTS MAINLY ALONG AND SOUTH OF INTERSTATE 90.

NEXT WEATHER SYSTEM CONTINUES PREVIOUS TREND WITH PERHAPS A
SLIGHT SOUTHWARD MOVEMENT OF THE SFC LOW...TOWARD INDIANAPOLIS
REGION BY 12Z WED. THE GFS ENSEMBLES WERE CLUSTERING CLOSE TO
THIS REGION BY THAT TIME AND LOCATION IS SIMILAR TO THE 00Z
ECMWF. THIS WOULD KEEP THE HEAVIER SNOW BAND FARTHER
SOUTH...MAINLY OVER IA AND SRN WI DURING THE EVENT. THERE SHOULD
BE ENOUGH FORCING WITH THE UPPER TROUGH PASSAGE AND ISENTROPIC
LIFT AS IT MOVES THROUGH TO GENERATE SEVERAL INCHES OF SNOW OVER
THE SOUTHERN AND EASTERN PORTION OF THE CWA. DRY/COLD SFC HIGH WILL
BE IN PLACE OVER THE DAKOTAS TO LIMIT SIGNIFICANT DEVELOPMENT OVER
THE NORTHWEST CWA. OVERALL HOWEVER...THIS SHOULD PROVIDE A
SNOWCOVER FOR MOST/IF NOT ALL OF THE CWA BY WEDNESDAY EVENING.
IT WILL PROVIDE SETUP FOR COLDER THAN NORMAL WEATHER THROUGH THE
END OF NEXT WEEK...ALONG WITH THE THREAT OF SOME SUBZERO LOW
TEMPERATURE READINGS IN AREAS WITH HEAVIER SNOW COVER.

&&

.AVIATION.../18Z TAF ISSUANCE/ 

IFR CLOUDS DEVELOPED IN CENTRAL MN IN COL AREA AT SFC...BUT THESE
WERE GRADUALLY DIMINISHING DURING MIDDAY HOURS. MAIN FEATURE IS
UPPER LOW IN NORTHWEST ONTARIO WITH SHORT WAVE EXTENDING WESTWARD
INTO ND. AS UPPER LOW MOVES AWAY...MN/WI WILL BE LEFT IN WEAK FLOW
PATTERN THROUGH THE NEXT 24 HOURS. WEAK SFC LOW IN NWRN SD AND
ANOTHER IN NERN NEBRASKA WITH LIGHT NE WINDS FROM SW INTO CENTRAL
MN.

KAXN/KSTC...PATCHY SCATTERED CLOUDS BLO 1000 FEET STILL IN THE
VICINITY OF BOTH SITES AND WILL NEED TO CARRY THE POSSIBILITY OF
BROKEN IFR CIGS INTO EARLY AFTERNOON. OTHERWISE...12Z NAM
SUGGESTS IFR WILL REDEVELOP LATE AFTERNOON OR THIS EVENING IN WEST
CENTRAL AND SOUTHWEST MN...BUT GFS DOES NOT. LATEST RUC KEEPS
PUTTING IT OFF AND DOES NOT INDICATE IFR UNTIL LATE EVENING. WITH
RUC TREND OF DELAYING THE IFR CIGS...WILL NOT MENTION ANY AT THIS
TIME BUT WILL NEED TO WATCH IN CASE THAT TREND REVERSES.

KRWF...12Z NAM SUGGESTS IFR WILL REDEVELOP LATE AFTERNOON OR THIS
EVENING IN WEST CENTRAL AND SOUTHWEST MN...BUT GFS DOES NOT.
LATEST RUC KEEPS PUTTING IT OFF AND DOES NOT INDICATE IFR UNTIL
LATE EVENING. WITH RUC TREND OF DELAYING THE IFR CIGS...WILL NOT
MENTION ANY AT THIS TIME BUT WILL NEED TO WATCH IN CASE THAT TREND
REVERSES.

KMSP/KRNH/KEAU...BKN/OVC MID-HIGH CLOUDS THROUGHOUT THE PERIOD.
12Z NAM DOES SUGGEST BKN DECK AROUND 8000 FEET MOVING IN FROM THE
SOUTH DURING THE LATE AFTERNOON OR EVENING AND HAVE ADDED THAT.
LIGHT WINDS WILL GRADUALLY SHIFT FROM SE TO ENE THIS AFTERNOON AND
EVENING AS ONTARIO LOW AND SD/NE LOWS MOVE EAST OR NORTHEAST.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&

$$
DWE/TDK