Issued by NWS Gaylord, MI
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000 FXUS63 KAPX 071541 AFDAPX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 1041 AM EST FRI NOV 7 2008 .SYNOPSIS.../ISSUED AT 327 AM/ DEEP LOW PRESSURE WILL GRADUALLY MAKE ITS WAY EASTWARD THRU THE GREAT LAKES REGION THIS WEEKEND...USHERING IN COLDER AIR AND UNSETTLED WEATHER FOR ALL OF MICHIGAN. THE LAKES WILL BECOME ACTIVE AS THE COLD AIR ARRIVES...PROVIDING ENHANCEMENT TO ONGOING PRECIPITATION. RAIN SHOWERS WILL EVENTUALLY MIX WITH AND CHANGE TO SNOW SHOWERS OVER THE WEEKEND AS THE COLD AIR FILTERS INTO THE REGION. COOL AND UNSETTLED WX WILL PERSIST INTO MONDAY...WITH DRY WX RETURNING BY THE MIDDLE OF NEXT WEEK. && .SHORT TERM.../ISSUED AT 1041 AM/...THIS AFTERNOON 13Z SURFACE ANALYSIS SHOWS WRAPPED UP 997MB LOW ALONG THE MN/IA BORDER...OCCLUDED/COLD FRONT LOOPS ACROSS MN...BACK EAST/SOUTHEAST ACROSS LAKE SUPERIOR/UPPER MI...THEN DOWN ACROSS WESTERN LOWER MI INTO EASTERN IN. MUCH OF THE PRECIPITATION AHEAD OF THE COLD FRONT HAS MOVED OUT OF THE AREA...THOUGH SCATTERED SHOWERS CONTINUE TO GENERATE OVER THE THUMB/LAKE HURON. ADDITIONAL MORE WIDESPREAD SHOWERS MOVING NORTH-NORTHEAST OUT OF OH...ATTACHED TO A COUPLE STRUNG OUT VORTICITY MAXIMA PER WATER VAPOR IMAGERY. SKIES HAVE CLEARED OVER NORTHWEST LOWER...BUT LOW CLOUDS/FOG ARE SPREAD ACROSS THE HIGHER TERRAIN OF NORTHERN LOWER...AS WELL AS ACROSS EASTERN UPPER. FOR THIS AFTERNOON...HAVE MADE SOME ADJUSTMENTS TO CLOUD COVER FORECAST GIVEN THE AFOREMENTIONED STRATUS DECK. 12Z APX SOUNDING AND AIRCRAFT SOUNDINGS SUGGEST THIS IS PRETTY THIN...SO EVEN WITH A SHALLOWER NOVEMBER SUN ANGLE THIS STUFF SHOULD MIX OUT WITH TIME. ACROSS NORTHEAST LOWER AND FAR EASTERN UPPER...WITH LOW LEVEL COLD ADVECTION DEVELOPING THIS MORNING OVER TOP OF A STILL RELATIVELY MOIST BOUNDARY LAYER...DIURNAL CU/SC SHOULD DEVELOP AND WILL KEEP SKIES CLOUDIER IN THESE AREAS. NORTHWEST LOWER WILL SEE SUN FOR THE BALANCE OF THE AFTERNOON BEFORE ST/SC SPREADS IN FROM THE SOUTHWEST TOWARD EVENING. JPB && .LONG TERM.../ISSUED AT 327 AM/...TONIGHT AND BEYOND DEEP WRAP AROUND MOISTURE (1000-500 MB RH OF 90 PCT) WILL SWING INTO MICHIGAN TONIGHT AS THE DRY SLOT PUSHES EAST OF THE REGION. SURFACE LOW WILL MOVE INTO UPPER MICHIGAN AS THE UPPER LOW REACHES CENTRAL LAKE MICHIGAN BY 12Z SATURDAY. RATHER STRONG VORT MAX DIRECTLY UNDER THE UPPER LOW WILL APPROACH OUR CWA LATE TONIGHT...AND THEN MOVE RIGHT OVERHEAD SATURDAY AND SATURDAY NIGHT. COMBINATION OF DEEP MOISTURE...SHARP CYCLONIC FLOW AND UPPER SUPPORT VIA THE SHORT WAVE AND UPPER LOW WILL CERTAINLY PRODUCE PLENTY OF SHOWER ACTIVITY TONIGHT THRU SATURDAY NIGHT. LOW LEVEL CAA WILL CONTINUE TONIGHT... DROPPING 850 MB TEMPS TO AROUND -5 C BY LATE EVENING. CERTAINLY THIS WILL PROVIDE ENOUGH OVER-LAKE INSTABILITY TO PRODUCE LAKE ENHANCEMENT OF ONGOING PRECIP. HOWEVER...LOW LEVEL FLOW WILL REMAIN OUT OF THE S/SW...WHICH LIMITS LOW LEVEL TRAJECTORIES OF LAKE ENHANCEMENT TO MAINLY WRN MACKINAC COUNTY. LOW LEVEL FLOW WILL EVENTUALLY SHIFT WEST AND THEN NW SATURDAY NIGHT...INITIATING A MUCH BETTER TRAJECTORY FOR LAKE ENHANCEMENT AND PRECONDITIONING OF LAKE SUPERIOR. THE BIG QUESTION IS PRECIP TYPE. MODEL SOUNDINGS SUGGEST PRECIP SHOULD REMAIN LIQUID THRU TONIGHT. PRECIP WILL BECOME MORE STRONGLY CONVECTIVE IN NATURE ON SATURDAY AS 500 MB TEMPS DROP TO AROUND -26 C. MODEL SOUNDING STILL POINT TO LIQUID PRECIP ON SATURDAY...BUT CANNOT RULE OUT SOME SLEET WITHIN HEAVIER CONVECTIVE SHOWER ACTIVITY. PRECIP WILL MIX WITH AND THEN CHANGE TO SNOW SATURDAY NIGHT...ESPECIALLY WITHIN THE HIGHER ELEVATIONS. UPPER LOW WILL PUSH NE OF OUR CWA BY SUNDAY...BUT PLENTY OF DEEP MOISTURE...SYNOPTIC LIFT AND OVER-LAKE INSTABILITY WILL LINGER BEHIND THE LOW IN ONGOING LOW LEVEL CAA. NO DOUBT LAKE ENHANCED PRECIP WILL CONTINUE SUNDAY INTO MONDAY...WITH PRECIP TYPE MAINLY FALLING IN FROZEN FORM PER MODEL SOUNDINGS. SOME MINOR ACCUMULATION IS POSSIBLE SUNDAY NIGHT AS TEMPS FALL BELOW FREEZING. && .MARINE.../ISSUED AT 327 AM/ PASSAGE OF COLD/OCCLUDED FRONT THIS MORNING WILL RESULT IN A SMALL SHIFT IN THE WINDS FROM SOUTHEAST TO SOUTH/SOUTHWEST. MAY SEE A FEW STRONGER GUSTS...BUT AT THIS POINT DO NOT EXPECT SCA CONDITIONS THROUGH TONIGHT. && .AVIATION.../ISSUED AT 626 AM/...VALID FOR 12Z TAFS SHOWERS WILL EXIT NE LWR MICHIGAN EARLY THIS MORNING...WITH A STEADY DIMINISH IN CLOUD COVER FROM WEST TO EAST ACROSS ALL OF NRN LWR MICHIGAN AS THE DRY SLOT ARRIVES. EXPECT VFR CONDITIONS UNTIL THIS EVENING WHEN CLOUDS AND SHOWERS MOVE BACK INTO THE REGION JUST AHEAD OF THE UPPER LOW. EXPECT CONDITIONS TO DETERIORATE TO MVFR WITH THESE WRAP-AROUND SHOWERS TONIGHT. && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. LH...NONE. LS...NONE. && $$
