FXUS63 KMPX 030946
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
346 AM CST THU DEC 3 2009

.DISCUSSION...

A COUPLE BIG CHALLENGES EXIST IN THE FORECAST PERIOD. ONE IS
ONGOING...WITH SNOW ACROSS SOUTHWEST AND SOUTH CTRL MN THROUGH
TODAY AND THE OTHER IS A POTENTIAL SYSTEM DURING THE LATTER HALF
OF THE WEEKEND.

GOES WV LOOP...AREA PROFILERS...AND RUC ANALYSIS ARE SHOWING AN
IMPRESSIVE UPPER TO MID LEVEL CIRCULATION MOVING FROM ERN SD INTO
SWRN MN. CONCENTRATED BANDS OF MODERATE SNOW SHOWERS ACROSS WEST
CTRL MN HAVE GIVEN 1 TO 2 INCH SNOW AMOUNTS IN YELLOW MEDICINE
COUNTY EARLY THIS MORNING. THESE BANDS ARE NOT ONLY WITHIN THE
COMPACT AREA OF PV ADVECTION FROM THIS WAVE BUT ALSO IN PLACE DUE
TO CONVERGENCE IN THE LOW TO MID LEVELS...PER RADAR AND LOW LEVEL
WIND ANALYSIS. OMEGA IS LARGE WITHIN THE DENDRITIC GROWTH ZONE AND
GIVEN H5 TEMPS OF -39C AT KBIS LAST EVE...RATIOS ARE HIGH AT 18-25
TO 1. IN ADDITION...STEEP LAPSE RATES IN A GOOD PORTION OF THE
TROP ARE KEEPING BANDS FURTHER ENHANCED...HIGHLIGHTED BY TOTAL
TOTAL INDICES IN THE LOWER TO MID 50S.

THIS ENTIRE AREA OF FORCING NEAR THE SAME MAGNITUDE SHIFTS
SOUTHEAST THEN EAST THROUGH TODAY...JUST NORTH AND NORTHEAST OF
THE CIRCULATION CENTER WHICH DROPS FROM SW MN INTO NRN AND
EVENTUALLY NE IOWA. THIS PLACES SOUTH CENTRAL MN IN A FAVORABLE
CORRIDOR FOR PERIODS OF SNOW AND/OR SNOW SHOWERS TODAY. THE 06Z
NAM AND 00Z GFS ARE IN GOOD AGREEMENT ON THIS...WITH SREF MEMBER
CONFIDENCE BULLS-EYING THIS PORTION OF THE FORECAST AREA. SO HAVE
GONE WITH CATEGORICAL POPS. QPF STILL FAIRLY LOW /0.07 OR
LESS/...BUT GIVEN A BLEND OF NUMERICAL AND HPC RATIO DATA SNOW
AMOUNTS OF 1 TO 2 INCHES ARE DERIVED NEAR ST JAMES AND
FAIRMONT...POSSIBLY EAST TOWARDS ALBERT LEA AS WELL. ABOUT A FOUR
TO SEVEN COUNTY AREA IN THE CWA. WILL HAVE MENTION IN THE HWO
CONSIDERING IT IS ONE OF THE FIRST ACCUMULATING SNOWS SINCE
OCTOBER FOR THIS AREA. OTHERWISE...OCCASIONAL LIGHTER SNOW TO
FLURRIES EXPECTED ACROSS THE REST OF THE CWA TODAY. THERE MAY BE 
SOME LAKE-DRIVEN SHOWERS OFF THE LARGER LAKES SUCH AS MILLE LACS.
HIGH TEMPS ABOUT 5 DEGREES COOLER THAN YESTERDAY WITH 925MB COLD
POCKET EXPECTED TO MOVE OVER THE REGION TODAY.

WHILE THE VORT DEPARTS THROUGH SRN WI TONIGHT...DEEP CYCLONIC FLOW
REMAINS OVER THE AREA THROUGH FRI. WEAK FORCING FOR MAINLY
FLURRIES EXISTS DURING THAT TIME. THE NAM CU RULE IS STILL
FAVORING BKN TO OVC CLOUD COVER THROUGH FRI. TEMPS ON FRI WILL BE
SIMILAR TO THU...MAYBE A COUPLE DEGREES COOLER WITH A LOWER
STARTING POINT FRI MORNING. WITH DECREASING WINDS BY FRI NIGHT AND
A LITTLE BIT OF SNOW COVER IN WRN TO SRN MN...SOME LOWS IN THE
SINGLE DIGITS ARE LIKELY IF CLOUDS PART...WHICH IS EXPECTED IN
THESE AREAS.

THE NEXT CHALLENGE IS THIS WEEKEND. NUMERICAL GUIDANCE IS IN
DISAGREEMENT WITHIN THE UPPER AND MID-LEVEL FORCING FIELDS...BUT
OTHER MASS FIELDS OF MSLP AND TEMPS ARE IN GENERAL AGREEMENT. IN
THE WAKE OF THIS LOW...A SURFACE TROUGH IS EXPECTED TO LINGER OVER
THE AREA SAT AND SUN...WITH DEEPENING PRESSURES SUN AS A MID-LEVEL
LOW/TROUGH ENTERS FROM NRN CANADA. THE GFS HAS BEEN MORE ROBUST
WITH THIS...WITH A SLOWER PASSAGE AND LONGER LASTING SNOW CHANCES.
THE 02/12Z AND 03/00Z ECWMF ARE QUICKER WITH MORE OF AN OPEN
WAVE WHICH THE 00Z GEM RESEMBLES. WHAT THE MODELS DO AGREE ON IS
THAT SUN NIGHT THERE ARE UPPER LEVEL HEIGHT FALLS ACROSS THE AREA
WITH DEEPENING PRESSURE TO THE SOUTHEAST AND FORCED ISENTROPIC
UPGLIDE INTO NRN IA AND SE MN. THE GULF APPEARS OPEN AS WELL IN
THE 850MB LEVEL. HAVE ENHANCED POPS OVER SRN MN DURING THAT TIME
ALONG WITH SRN WFO NEIGHBORS...GIVING MOST WEIGHT TO THE ECWMF AND
CANADIAN. WILL NEED TO WATCH TO SEE IF EVEN MORE ENHANCEMENT IS
NEEDED SOON IF MODELS TREND THE GFS WAY.

THERE CONTINUES TO BE AN ACTIVE PATTERN...EL NINO
LIKE...ADVERTISED ACROSS THE CTRL TO SRN PART OF THE COUNTRY IN
THE ERLY TO MIDDLE PART OF NEXT WEEK. THIS SHOULD GENERALLY KEEP
TEMPS IN THE MON-WED TIME FRAME AT LEAST SLIGHTLY BELOW NORMAL
WITH NRLY FLOW PREVAILING.

&&

.AVIATION.../06Z TAF ISSUANCE/ 

MAIN AVIATION CONCERN DEALS WITH FAIRLY ACTIVE SHORT WAVE
CURRENTLY ACROSS NE SD...WITH A STRONG OMEGA FIELD IN SW/WC MN.
THIS HAS PRODUCED BRIEF PERIODS OF -SN WITH VSBY DROPPING TO 1SM
AT RWF. HOWEVER...THIS WAVE WILL LIKELY ONLY AFFECT RWF FOR THE NEXT
FEW HRS AND THE BEST LIFT AND MOISTURE WILL RESIDE IN FAR SW MN
OVERNIGHT. THEREFORE...KEPT VSBY MVFR OR HIGHER. THERE MAY BE A
PERIOD BETWEEN 06/12Z WHERE RWF MAY BRIEFLY DECREASES TO IFR VSBY
IN -SN...BUT AM NOT FORECASTING THIS SCENARIO AT THIS TIME.
ELSEWHERE...-SN IS LIKELY DURING THE FIRST 18 HRS...BUT DUE TO THE
DEPTH OF THE STRONGEST LIFT SOUTH OF THE AREA...NOT EXPECTING MUCH
TOO MUCH. CEILINGS WILL BE PROBLEMATIC DUE TO PERSISTENT MOISTURE
FEED FROM THE NORTH AND RH FIELD BELOW 85H STILL HIGH ENOUGH TO
WARRANT MVFR CEILINGS. ..JLT..

&&

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

$$

MTF/JLT