Issued by NWS Marquette, MI
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000 FXUS63 KMQT 071204 AAA AFDMQT AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 703 AM EST FRI NOV 7 2008 UPDATED FOR 12Z AVIATION DISCUSSION .SYNOPSIS... 09Z WV IMAGERY AND RUC ANALYSIS SHOW A LARGE UPPER LOW ROTATING OVER SW MN WITH A FAIRLY BROAD UPSTREAM RIDGE OVER THE WRN CONUS. STACKED LOW PRESSURE RESULTING IN 998 MB SFC LOW PRES OVER SW MN. TIGHTLY PACKED PRESSURE GRADIENT BEHIND THE LOW IS STILL PRODUCING VERY STRONG NW WINDS (GUSTS OVER 40 MPH AT SOME LOCATIONS) ACROSS DAKOTAS AND BLIZZARD CONDITIONS OVER CENTRAL SD. OVER OUR AREA...THE INITIAL BAND OF WAA RAIN AHEAD OF THE LOW HAS GENERALLY EXITED ALL EXCEPT FAR ERN COUNTIES OF UPR MI. DRY SLOT AS DEPICTED ON FCST SNDGS AND NOTED ON WATER VAPOR LOOP IS MOVING ACROSS MUCH OF THE U.P EARLY THIS MORNING. THE DRY SLOT HAS EITHER ENDED THE RAIN OR DIMINISHED PCPN TO -DZ. && .DISCUSSION... GIVEN THE DRY SLOT MOVING OVER THE AREA AND THE SLOWER ADVANCE OF THE UPR LOW TODAY TOWARD THE GREAT LAKES AS DEPICTED BY THE 00Z MODELS...HAVE DECIDED TO TRIM BACK COVERAGE OF SHRA TO ISOLD FOR ALL BUT THE FAR SW FCST AREA FOR LATE IN THE AFTERNOON. AS THE UPPER LOW SLOWLY SLIDES SOUTH OF THE FCST AREA LATE TONIGHT LOOK FOR PCPN IN DEFORMATION ZONE/COMMA HEAD OF UPR LOW TO WRAP BACK TOWARD THE WRN FCST AREA ESPECIALLY TOWARD 12Z SAT WHEN MODELS SHOW INCREASING ISENTROPIC ASCENT ON THE 290-295K SFC. THUS...HAVE KEPT LIKELY POPS OVER THE FAR WEST BUT HAVE TRIMMED BACK POPS TO AROUND 40 PCT OVER THE FAR EAST DUE TO LACK OF DEEP MOISTURE AND ABSENCE OF GOOD ISENTROPIC ASCENT. GIVEN DEGREE OF WARM AIR AT 850 MB (-1 TO -2C TEMPS) THAT`S WRAPPING BEHIND THE LOW LOOK FOR PCPN TYPE TO BE MOSTLY RAIN TONIGHT. AS DEFORMATION ZONE WITH SYSTEM AND IMPRESSIVE 290-295K ISENTROPIC ASCENT SPREADS EAST SAT AFTERNOON INTO SAT NIGHT...GRADUALLY UPPED POPS TO CATEGORICAL ACROSS THE NRN AND ERN TIER. COLDER 850 MB TEMPS OF -8 TO -11C FLOODING ACROSS THE AREA LATE SAT INTO SAT NIGHT WILL ENSURE CHANGEOVER FROM LAKE ENHANCED RAIN TO LAKE ENHANCED SNOW. GIVEN THE IMPRESSIVE DYNAMICS LATE SAT INTO SAT NIGHT...WOULD EXPECT THE POTENTIAL FOR SOME HEAVY WET SNOW OVER WRN AND NCNTRL PORTIONS OF THE CWA IN NNW FLOW. ONLY LIMITATION FOR SNOW AMOUNTS IS EXPECTED LOW 10/1 SNOW/WATER RATIO AS MODEL SNDGS INDICATE BETTER MODEL OMEGA OCCURRING BELOW FAVORABLE DENDRITIC SNOW GROWTH REGION. THUS...AT THIS POINT...WOULD NOT ANTIPICATE WARNING SNOW AMOUNTS TO JUSTIFY A WATCH BUT I`M PRETTY CONFIDENT THAT ADVISORIES WILL BE NEEDED FOR SOME WRN AND PERHAPS NCNTRL COUNTIES. WILL ISSUE A SPS TO HIGHLIGHT POTENTIAL FOR SOME HEAVIER WET SNOW LATE SATURDAY INTO SUNDAY. ALTHOUGH PLAINS UPR LOW WILL BE PULLING EAST BY SUN...ANOTHER SHORTWAVE DIVING SOUTH THROUGH THE NRN PLAINS COULD PROVIDE ADDITIONAL ENHANCEMENT FOR LES AND THIS WILL NEED TO BE WATCHED ON LATER MODEL RUNS. LINGERING 850 MB TEMPS OF -9 TO -11C AND DEEP CYCLONIC NWRLY FLOW WILL STILL WARRANT LIKELY POPS FOR THE NW SNOWBELTS DOWNWIND OF LAKE SUPERIOR WITH CHC POPS OVER SRN COUNTIES. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... OTHER THAN LIGHT PATCHY FOG EARLY ON AT BOTH SITES...VFR CONDITIONS PREDOMINATE TODAY AS DRIER AIR SHIFTS IN FM THE SOUTH. EVENTUALLY ...WRAP AROUND MOISTURE AND PCPN CURRENTLY PUSHING ACROSS SE MN...PIVOTS INTO UPR MI FM THE SOUTH THIS EVENING. THE ARRIVAL OF THIS MOISTURE WILL LOWER CIGS TO MVFR LATE THIS EVENING THROUGH THE OVERNIGHT HOURS TONIGHT AND ALSO BRING A BETTER CHANCE OF RAIN SHOWERS. BASED ON LOW LEVEL THICKNESSES AND UPSTREAM OBS...SNOW MAY BEGIN MIX IN WITH THE RAIN AT SAW BY SUNRISE ON SATURDAY. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... SFC LOW OVER SOUTHERN MN DRIFTS NORTHEAST ACROSS THE UPPER GREAT LAKES THROUGH SATURDAY AFTN. LIGHT PRESSURE GRADIENT WITH THE LOW CENTER LEADS TO WINDS STAYING BLO 25 KNOTS INTO THIS EVENING. THEN...AS THE LOW BEGINS TO SHIFT EAST OF LAKE SUPERIOR ON SATURDAY...WINDS INCREASE FROM WEST TO EAST ACROSS LAKE SUPERIOR. COLD AIR FLOWING OVR THE WARMER LAKE LEADS TO UNSTABLE LOW LEVELS AND GOOD MIXING. THE BETTER MIXING AND TIGHT PRESSURE GRADIENT SHOULD RESULT IN 30 KNOT WINDS WITH POTENTIAL FOR A FEW GALE FORCE GUSTS TO 35 KNOTS SATURDAY AFTERNOON/EVENING BEHIND THE COLD FRONT. HIGH PRESSURE SLIDING ACROSS THE UPR GREAT LAKES LATER MONDAY THROUGH THURSDAY WILL KEEP WINDS LESS THAN 25 KNOTS. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ SYNOPSIS/DISCUSSION...VOSS AVIATION...JLA MARINE...JLA
