Issued by NWS Twin Cities, MN
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000 FXUS63 KMPX 071413 AFDMPX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 416 AM CST FRI NOV 7 2008 .DISCUSSION... 09Z OBSERVATIONAL ANALYSIS AND SATELLITE/RADAR IMAGERY ILLUSTRATED A STRONG VORTEX PIVOTING ACROSS WEST CENTRAL AND SOUTHWEST MINNESOTA. THIS CYCLONE WILL SPIN ACROSS THE FORECAST AREA TODAY...AND BRING A WINTRY MIX OF PRECIPITATION. THE PRECIP TYPE OVER WEST CENTRAL AND SOUTH CENTRAL MN COUNTIES HAS TRANSITIONED TO SNOW...AND CORRELATES WELL WITH THE NAM 925MB SUB-ZERO TEMPERATURE DELINEATION. AS THE LOW ROTATES ACROSS SOUTHERN MN TODAY...A LOW LEVEL WARM TONGUE WRAPS AROUND ITS NORTHERN/WESTERN PERIPHERY...AND NOSES INTO THE NORTHERN/CENTRAL CWA. AS A GENERAL GUIDELINE...THE DOMINANT MORNING PRECIP TYPE IN AREAS SOUTH OF THE INTERSTATE 94 CORRIDOR SHOULD BE SNOW...PREDOMINATELY RAIN IN LOCALES TO THE NORTH...AND A MIX AT LOCATIONS SPANNING THE CORRIDOR. A RAIN SNOW MIX WILL THEN BE POSSIBLE ACROSS NORTH/EAST CENTRAL MN INTO WEST CENTRAL THIS AFTERNOON...WITH MAINLY TEMPERATURE PROFILES STILL INDICATING RAIN ACROSS THE EXTREME NORTHEASTERN PORTION OF THE CWA NEAR LADYSMITH AND RICE LAKE WI INTO THIS EVENING. WITH THE EXCEPTION OF THE AFOREMENTIONED SLIVER OF WEST CENTRAL WI COUNTIES...THE MAJORITY OF THE FORECAST AREA SHOULD SEE SNOW BY 00Z SAT. BRISK NORTHWEST WINDS WILL ACCOMPANY THE SNOWFALL TODAY AND TONIGHT...WITH SUSTAINED SPEEDS OF 20 TO 25 KNOTS ACCOMPANIED BY GUSTS TO AROUND 35 KNOTS. ATTENDANT VISIBILITY REDUCTIONS WITH THE SNOW AND WIND SHOULD BE AROUND 1 TO 2 MILES AT TIMES TODAY. HIGH POPS ARE WARRANTED ACROSS THE CWA THROUGH TONIGHT...ESPECIALLY ACROSS THE EAST...AS THE DEFORMATION AXIS SHIFTS INTO EAST CENTRAL MN AND WEST CENTRAL WI. CYCLONIC FLOW AND ASSOCIATED LIGHT SNOW/FLURRIES WILL LINGER THROUGH THE BETTER PORTION OF THE WEEKEND...AS THE LOW MEANDERS ACROSS THE GREAT LAKES REGION. THE BULK OF THE MEASURABLE SNOWFALL IS EXPECTED TO FALL BETWEEN 12Z TODAY AND 12Z SATURDAY. TOTAL SNOWFALL AMOUNTS BETWEEN ONE AND THREE INCHES WILL BE COMMON...WITH THE HIGHEST AMOUNTS LOCATED ALONG AND SOUTH OF A LINE FROM THE MN RIVER VALLEY TO THE SOUTHERN TWIN CITIES METRO...TOWARD EAU CLAIRE. ANY ACCUMULATIONS ON SATURDAY SHOULD BE AROUND ONE HALF INCH OR LESS...AND MAINLY OCCUR OVER WEST CENTRAL WI. NEARLY STEADY TO FALLING TEMPERATURES ARE EXPECTED AGAIN TODAY...WITH TEMPERATURES NOT ESCAPING THE 30S UNTIL NEXT WEEK. ANOTHER SHORTWAVE TROUGH WILL FOLLOW CLOSELY ON THE HEELS OF THE CURRENT ONE...BUT MEDIUM RANGE MODELS KEEP MOST OF THE RELATED PRECIPITATION SOUTH OF THE AREA THROUGH EARLY NEXT WEEK. && .AVIATION... /12Z TAF ISSUANCE/ IR IMAGERY QUITE CLEAR ON PLACING POSITION OF 996MB SURFACE LOW PRESSURE SYSTEM OVER EXTREME SW MN JUST SOUTHWEST OF THE BUFFALO RIDGE. COPIOUS AMOUNTS OF MOISTURE ROTATING AROUND SYSTEM DEPICTED WELL ON GFS40 290K ISENTROPIC ANAL. MVFR CIGS AND VSBYS GENERALLY THE RULE INSIDE BOTH LIQUID AND SOLID PRECIPITATION. AS NOTED ABOVE 925MB TEMPS PRETTY MUCH ROAD MAP FOR PLACEMENT OF SNOW VS RAIN/-DZ IN TAF REGIME THIS DAY. COLDEST TEMPERATURES ACTUALLY WRAPPING AROUND 50H LOW STACKED ABOVE SURFACE SYSTEM ACROSS FAR SOUTHERN MN. ODDLY NORTHERNMOST TAF SITES SUCH AS AXN AND STC WILL BE THE LATEST CHANGING OVER TO SNOW BY LATE THIS AFTERNOON. LOOKS LIKE A STEADY LIGHT SNOW EVENT ACROSS REGION INTO AT LEAST 06Z FOR WESTERN HALF OF FORECAST REGION...WITH SNOW CONTINUING INTO TONIGHT OVER EASTERN HALF. DRY AIR ALONG WITH TIGHTENING SURFACE GRADIENT WILL INSURE HIGHER CIGS AND VSBSYS OVR RWF...AXN...AND EVENTUALLY STC AIRPORT SITES BY SHORTLY AFTER MIDNIGHT. IFR CIGS AND MVFR VSBYS HOWEVER WILL CONTINUE ELSEWHERE INTO AT LEAST 10Z TIME FRAME. CONSIDERABLE LOW LEVEL DRYING WILL ENSUE AT STACKED LOW PRESSURE SYSTEM TREKS INTO SE WI BY DAWN ON SAT. RESIDUAL MOISTURE ORBITTING SAME WILL INSURE ADDITIONAL SCATTERED LIGHT TO MDT SNOW SHOWERS OVER WI AIRPORT SITES PRIOR TO 18Z SAT. PLENTY OF CAA AND TIGHT SURFACE GRADIENT ON SATURDAY INSURING PLENTY OF MVFR STRATOCU AND NW WINDS IN THE 15 TO 20 MPH SUSTAINED RANGE MAINLY DURING THE LATE MORNING AND EARLY AFTERNOON. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ LS/AZ
