FXUS63 KMPX 031813
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1213 PM CST THU DEC 3 2009
.UPDATE...
ADDED AVIATION DISCUSSION FOR 18Z TAFS BELOW...
&&
.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.../18Z TAF ISSUANCE/
UPPER LEVEL LOW PRESSURE ROTATING OVER SOUTHWEST MN CONTINUES TO
GENERATE SNOWFALL OVER FAR SOUTHWEST AND SOUTH CENTRAL
MINNESOTA...GENERALLY SOUTH OF THE TERMINALS. COLDER AIR MOVING
INTO THE AREA CONTINUES TO BRING MVFR CLOUD COVER THIS AFTERNOON.
CLOUD COVER WILL BE THE MAIN CHALLENGE THROUGH THE PERIOD. SNOW
FLURRIES OR LIGHT SNOW SHOWERS WILL CONTINUE ON AND OFF THROUGH
THE PERIOD WITH THE BEST CHANCE BEING TODAY AND THEN AGAIN AFTER
MIDNIGHT AT KAXN/KSTC AS ANOTHER UPPER LEVEL DISTURBANCE PASSES.
NORTH WINDS WILL BACK WESTERLY STARTING THIS EVENING AND
CONTINUING INTO FRIDAY MORNING.
KAXN...CEILINGS WILL BE THE MAIN CHALLENGE WITH MVFR CIGS
EXPECTED THROUGH THE PERIOD. BREAKS IN THE CLOUDS DO APPEAR
UPSTREAM BUT THIS LOOKS TO STAY MAINLY JUST WEST OF THE TERMINAL
THIS AFTERNOON. SHOULD SEE SOME RISING OF CLOUD BASE LATER THIS
AFTERNOON AND THIS EVENING BUT WILL NEED TO WATCH FOR BREAKS. AN UPPER
WAVE WILL PASS AFTER MIDNIGHT AND MAY BRING LIGHT SNOW WHICH MAY
BRING VSBY DOWN TO MVFR.
KSTC...EXPECT CEILINGS TO REMAIN MVFR THROUGH THE PERIOD WITH
ISOLATED/SCATTERED SNOW FLURRIES/SHOWERS MOVING IN YET THIS
AFTERNOON. MVFR VSBY IN -SN IS POSSIBLE AFTER MIDNIGHT WITH THE
PASSAGE OF AN UPPER WAVE.
KRWF...MAIN CHALLENGE WILL BE SNOW EARLY THIS AFTERNOON THEN CIGS
THRU THE PERIOD. RADAR AND SFC OBS CONTINUE TO SHOW BAND OF SNOW
JUST WEST OF THE TERMINAL AND HEADING SLOWLY EAST. EXPECT THIS
BAND TO CROSS THE FIELD OVER THE NEXT FEW HOURS AND BRING VSBY TO
AROUND 2SM. SNOW WILL TAPER OFF TO FLURRIES BY LATE AFTERNOON WITH MVFR
CIGS CONTINUING TONIGHT WITH SOME SCATTERING BELOW 3000 FT FRIDAY
MORNING.
KMSP...CEILINGS IN THE 1800 TO 2100 FT RANGE ARE EXPECTED TO
CONTINUE THROUGH THE AFTERNOON WITH SCATTERED FLURRIES OR LIGHT
SNOW ALSO POSSIBLE...ESPECIALLY AFTER 20Z OR SO. LOWER CONFIDENCE
IN CLOUD BASES TONIGHT AND CIGS IN TAFS MAY BE A BIT LOW SO WILL
CONTINUE TO MONITOR. CEILINGS AROUND 2000 FT EXPECTED FOR FRIDAY.
WINDS ARE EXPECTED TO BE IN THE 240 TO 270 DEGREE RANGE AROUND 10
KTS FRIDAY MORNING.
KEAU...VFR CEILINGS EXPECTED TO DECREASE TO MVFR AROUND 2000 FT
YET THIS AFTERNOON WITH AN INCREASING CHANCE OF SCATTERED FLURRIES
OR LIGHT SNOW. MVFR CIGS EXPECTED TO CONTINUE THROUGH FRIDAY.
KRNH...MVFR CIGS WILL CONTINUE WITH HEIGHT OF BASES THE MAIN
CHALLENGE. EXPECT BASES TO CREEP UP TO AROUND 2000 FT THIS
AFTERNOON. LOWER CONFIDENCE IN THE TREND THIS EVENING AND TONIGHT
BUT EXPECT MVFR WILL PREVAIL THROUGH FRIDAY. ..MDB..
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
MTF/MDB
