000 FXUS63 KMQT 050539 AAB AFDMQT AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1240 AM EST FRI DEC 5 2008 UPDATED AVIATION DISCUSSION FOR 06Z TAF ISSUANCE .UPDATE... ISSUED AT 700 PM EST UPDATED FCST TO EXTEND LAKE EFFECT SNOW WARNING UNTIL 7 AM FRI FOR ONTONAGON COUNTY. CURRENTLY...KMQT AND KDLH RADAR IMAGERY INDICATE HEAVIER BANDS OF SNOW IMPACTING THE AREAS FROM THE PORCUPINE MOUNTAINS TO BERGLAND AND ALSO N OF MASS CITY. WHILE WINDS WILL BEGIN TO BACK TONIGHT...IT WON`T BE ENOUGH TO SHIFT HEAVIER SNOW N OF THE COUNTY UNTIL EARLY FRI MORNING. ALSO...AS THE BACKING BEGINS AND LAND BREEZES BECOME STRONGER DURING THE NIGHT...LOW-LEVEL CONVERGENCE WILL STRENGTHEN AND BECOME FOCUSED ACROSS NRN ONTONAGON COUNTY. SO...SNOW WILL LIKELY INCREASE INTENSITY DURING THE NIGHT ACROSS THE NRN PORTION OF THE COUNTY. && .SYNOPSIS... ISSUED AT 350 PM EST UPPER AIR PATTERN CONSISTS OF A 500 MB RIDGE OFF THE WEST COAST AND EAST COAST AND A BROAD 500 MB TROUGH ACROSS THE REST OF THE U.S. WITH SOME SHORTWAVES EMBEDDED IN THIS TROUGH. ONE STRONG WAVE IN THIS TROUGH IS ACROSS CENTRAL ONTARIO AND THIS IS DROPPING SOUTH TODAY AND WILL AFFECT THE AREA TONIGHT. && .SHORT TERM THROUGH 00Z SAT... ISSUED AT 350 PM EST UPPER LEVEL TROUGH REMAINS ACROSS THE REGION. NAM SHOWING 850-500 MB Q-VECTOR CONVERGENCE MOVING OUT BY THIS EVENING. A CLIPPER TYPE SYSTEM WILL AFFECT THE AREA FRI NIGHT. NAM SHOWING WEAK ISENTROPIC LIFT ON I270K-I285K AND SOME MOISTURE ACROSS THE CWA TONIGHT AND THIS IS MOSTLY ACROSS THE NORTHERN AND EASTERN CWA. THIS LIFT AND MOISTURE REMAIN ACROSS THE NORTH AND EAST IN THE LOW LEVELS ON FRI AS WELL ON I270K-I275K SURFACES. DID NOT MAKE TOO MANY CHANGES TO THE GOING FORECAST AS PREVIOUS FORECAST HAD THINGS WELL IN HAND. LAKE EFFECT SNOW LOOKS TO CONTINUE AS THE WIND SLOWLY BACKS TO THE WEST AND WSW LATE TONIGHT AND ALSO FOR FRI. 850 MB TEMPERATURES WARM UP A BIT AND INVERSION HEIGHTS FALL BEFORE THE CLIPPER SYSTEM ARRIVES FOR FRI NIGHT...SO COMBO OF WINDS AND LOWERING INVERSION HEIGHTS SHOULD KEEP LAKE EFFECT SNOW IN CHECK LATE TONIGHT AND ALSO FOR LATE FRI AFTERNOON. OVERALL...DID NOT CHANGE MUCH. .LONG TERM...00Z SAT - 00Z MON GUIDANCE REMAINS IN STRONG AGREEMENT THROUGH DAY 4. GFS STILL LOOKS FAVORABLE THROUGH DAY 6. MODELS SHOWING CONSIDERABLE DIVERGENCE THERE AFTER CONTRIBUTING TO LOWER CONFIDENCE IN THE MODELS. THEREFORE, WILL FOLLOW HPC RECOMMENDATION OF GOING WITH GFS THROUGH DAY 6 AND A BLEND OF THE ENSEMBLE MEANS DAY 7. A WEAK SHORTWAVE TROUGH ROTATING THROUGH THE BASE OF THE MID LEVEL LOW OVER HUDSON BAY WILL SWEEP THROUGH UPPER MICHIGAN FRIDAY NIGHT AND SATURDAY. THE SURFACE LOW OVER SOUTHERN MANITOBA WILL ALSO SWEEP ACROSS UPPER MICHIGAN AND REACH LAKE HURON BY SATURDAY EVENING. A RIDGE DEVELOPING OVER CENTRAL CANADA WILL DIVE INTO SOUTH CENTRAL CANADA AND THE NORTHERN PLAINS BY SATURDAY EVENING. Q-VECTOR CONVERGENCE AND ISENTROPIC ASCENT ASSOCIATED WITH THIS SYSTEM WILL PRODUCE SYSTEM SNOW OVER THE AREA. THE SHORTWAVE WILL DEEPEN INTO A LONGWAVE TROUGH AND PUSH EAST INTO SOUTHWEST QUEBEC. A WEAK RIDGE AND A PRONOUNCED SURFACE RIDGE WILL PUSH INTO WISCONSIN AND WESTERN LAKE SUPERIOR BY SUNDAY EVENING. THE SYSTEM SNOWS WILL WEAKEN AS THE NORTHERLY WINDS BRING AN 850MB THERMAL TROUGH INTO THE AREA INCREASING THE DELTA-T`S TO AROUND 23C AND INCREASING THE POTENTIAL FOR LES OVER THE AREA. THE AREAS MOST LIKELY TO RECEIVE THE HEAVY LES WILL BE THOSE MOST AFFECTED BY NORTHWEST WINDS FLOWS. STRONG WINDS COMING OFF OF LAKE SUPERIOR ALONG WITH SNOWFALL POTENTIAL OF 4 TO 6 INCHES. THUS PLAN TO GO WITH A WINTER STORM WATCH FOR THE KEWEENAW PENINSULA. LIMITING FACTORS OF LES WILL BE THE STRONG WINDS AND THE DURATION BEFORE THE DRY AIR MOVES INTO THE AREA. AS THE LONGWAVE TROUGH LIFTS NORTHEAST INTO THE CANADIAN MARITIME...ANOTHER LONGWAVE TROUGH WILL DEVELOP OVER THE CENTRAL PLAINS ON SUNDAY NIGHT AND MONDAY INTO MONDAY NIGHT. THE SURFACE RIDGE WILL SHIFT EAST AS COLD FRONT TRACKS INTO THE U.P. ON MONDAY AND PROGRESS ON TO LOWER MICHIGAN MONDAY NIGHT. WINDS WILL VEER NORTHWEST FOLLOWING THE FROPA. THIS WILL PRODUCE A LAKE-850MB DELTA-T OF AROUND 18C. THIS WILL LEAD TO A LES PRODUCTION ACROSS MUCH OF THE NORTHERN PART OF THE AREA. AS DRY AIR DESCEND ON THE AREA AND WINDS BACK SOUTHWEST ENDING THE CHANCES OF LES. A MID LEVEL LOW WILL SHIFT OUT OF NORTHERN MANITOBA INTO NORTHERN ONTARIO...IN ASSOCIATION WITH A LONGWAVE TROUGH TRACKING THROUGH THE UPPER MISSISSIPPI RIVER VALLEY. THE LONGWAVE TROUGH WILL SWEEP THROUGH THE FORECAST AREA TUESDAY NIGHT AND WEDNESDAY WHILE DEEPENING. MEANWHILE...ANOTHER RIDGE WILL SETTLE SOUTH OUT OF CENTRAL CANADA COLD AIR ADVECTION AHEAD OF THE RIDGE WILL CONTINUE TO PRODUCE DELTA-T`S OF 23C TO 27C OVER LAKE SUPERIOR. THIS IS PLENTY UNSTABLE AT THE LOW LEVELS TO KEEP THE CHANCES OF LAKE EFFECT SNOW SHOWERS GOING. THIS WILL ALSO PRODUCE VERY COLD TEMPERATURES ACROSS THE AREA. TUESDAY NIGHT LOW TEMPERATURES WILL DIP TO NEAR ZERO OVER THE WESTERN U.P. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... WITH LAKE EFFECT -SHSN CONTINUING AT KCMX...EXPECT CONDITIONS TO VARY BTWN IFR AND LIFR THRU THE MORNING. THERE MAY BE SOME BRIEF PERIODS OF MVFR AND PERHAPS VFR...BUT THOSE PERIODS WILL BE VERY INFREQUENT. AS WINDS BACK MORE TO THE SW VERY LATE IN THE NIGHT INTO THE MORNING...ENHANCING LOW-LEVEL CONVERGENCE...EXPECT A PREVAILING PERIOD OF VLIFR CONDITIONS IN HEAVIER SHSN. AS WINDS CONTINUE TO BACK...EXPECT CONDITIONS TO IMPROVE TO MVFR LATE MORNING AND TO VFR IN THE AFTN. NEXT LOW PRES SYSTEM DROPPING INTO THE UPPER LAKES REGION WILL BRING A RETURN TO MVFR CONDITIONS WITH -SN DURING THE EVENING. AT KSAW...WITH LOW-LEVEL W TO SW WINDS...LAKE EFFECT -SHSN WILL NOT BE AN ISSUE. EXPECT VFR CONDITIONS TO PREVAIL OVERNIGHT THRU THE AFTN. MVFR CONDITIONS SHOULD DEVELOP IN THE EVENING AS -SN SPREADS INTO THE AREA IN ASSOCIATION WITH APPROACHING LOW PRES SYSTEM. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... GALES POSSIBLE ON SAT AND SATURDAY NIGHT...OTHERWISE WINDS LOOK TO STAY BELOW 30 KNOTS THROUGH THE PERIOD WITH A COUPLE OTHER PERIODS CLOSE TO GALES THOUGH. WINDS DIMINISH BY SUNDAY AS HIGH PRESSURE MOVES ACROSS THE GREAT LAKES. SRLY GALES POSSIBLE ON MONDAY...MAINLY ERN SECTIONS OF LK SUPERIOR...AHEAD OF LOW PRESSURE SYSTEM DROPPING INTO THE REGION FM CNTRL CANADA. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... LAKE EFFECT SNOW WARNING UNTIL 7 AM EST FRI MIZ002. LAKE EFFECT SNOW WARNING UNTIL 10 AM EST FRI MIZ006-007. LAKE EFFECT SNOW WARNING UNTIL 7 PM EST FRI MIZ003. LAKE EFFECT SNOW ADVISORY UNTIL 7 PM EST FRI MIZ001. WINTER STORM WATCH SAT MORNING THRU SUN MORNING MIZ001>003. WINTER STORM WATCH SAT AFTN THRU SUN AFTN MIZ006-007-085. LAKE SUPERIOR... GALE WARNING UNTIL 4 AM EST FRI LSZ250-251-266-267. LAKE MICHIGAN...NONE. && $$ UPDATE...ROLFSON SYNOPSIS/SHORT TERM...GM LONG TERM...DLG AVIATION...ROLFSON MARINE...GM