Issued by NWS Gaylord, MI
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000 FXUS63 KAPX 240334 AFDAPX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 1034 PM EST MON NOV 23 2009 .SYNOPSIS.../ISSUED AT 357 PM/ RAIN CHANCES WILL INCREASE HEADING INTO TUESDAY NIGHT AND WEDNESDAY AS A PAIR OF UPPER LEVEL DISTURBANCES ROTATE TOWARD THE UPPER GREAT LAKES REGION THROUGH THANKSGIVING DAY. DOES APPEAR THAT THE PRE-HOLIDAY TRAVEL PERIOD WILL ONLY BE WET...WITH WINTRY PRECIPITATION NOT EXPECTED TO INTERFERE WITH TRAVEL PLANS THROUGH THANKSGIVING DAY. JPB && .SHORT TERM.../ISSUED AT 1034 PM/...OVERNIGHT SURFACE RIDGE AXIS IS HOLDING JUST NORTH OF MICHIGAN LATE THIS EVENING...WITH WEAK LOW LEVEL WAA UNDERWAY. ANY BRIEF BREAKS IN THE CLOUD COVER EARLIER THIS EVENING HAVE QUICKLY FILLED BACK IN AS LOW STRATUS HAS REDEVELOPED WITHIN THESE BREAKS. AREAS OF FOG LINGER ACROSS ERN AND SRN SECTIONS OF OUR CWA AHEAD OF AN APPROACHING WEAK WAVE CURRENTLY OVER SRN LOWER MICHIGAN. OBS ACROSS THE REST OF THE CWA SHOW LITTLE IN THE WAY OF FOG...BUT CERTAINLY QUITE A BIT OF STRATUS STILL IN PLACE. AS WEAK WAVE TO THE SOUTH LIFTS NORTHWARD OVERNIGHT...EXPECT AREAS OF FOG WILL SPREAD BACK INTO THE REST OF OUR CWA. HAVE REDUCED FOG WORDING FROM AREAS OF DENSE FOG TO AREAS OF FOG...AND HAVE SLIGHTLY INCREASED CLOUD COVER OVERNIGHT. REMAINDER OF THE FORECAST WILL BE UNCHANGED. && .LONG TERM.../ISSUED AT 357 PM/...TUESDAY AND BEYOND LARGE SCALE PATTERN FEATURES A NUMBER OF SHORT WAVE TROUGH ACROSS NORTH AMERICA EXTENDING BACK OUT INTO THE PACIFIC...A PROGRESSIVE 5 WAVE PATTERN WITH MEAN TROUGHING ROUGHLY ACROSS CENTRAL NORTH AMERICA. INITIAL FOCUS WILL BE ON A TROUGH DIGGING SOUTHEAST THROUGH THE CENTRAL ROCKIES THIS AFTERNOON...AND A FOLLOW UP TROUGH CURRENTLY CROSSING THE BRITISH COLUMBIA COAST. LEAD WAVE FORECAST TO BOTTOM OUT OVER THE CENTRAL PLAINS TUESDAY...THEN GET KICKED NORTHEAST AS TRAILING FEATURE DIGS INTO THE MIDWEST BEHIND IT BY THANKSGIVING. SO POTENTIAL IMPACTS ON HOLIDAY TRAVEL WITH THESE SYSTEMS WILL BE THE PRIMARY FORECAST ISSUE IN THE NEAR TERM. BEYOND THAT...SOME SMALL HINTS OF THE PATTERN TRYING TO SHIFT TO SOMETHING A LITTLE COLDER...BUT NOTHING REAL DEFINITIVE AT THIS POINT. AND WITH THE COLDEST AIR STILL PINNED NORTH OF THE ARCTIC CIRCLE (AND ACROSS MUCH OF ASIA...FOR THAT MATTER)...WILL NEED A STRONG BUCKLING OF THE FLOW TO TAP INTO THAT. TUESDAY...SHORT WAVE DIGGING ACROSS THE CENTRAL ROCKIES FORECAST TO BOTTOM OUT OVER KANSAS TONIGHT AND HEAD INTO THE MID MISSISSIPPI VALLEY DURING THE DAY TUESDAY. MAIN PROBLEM FOR TUESDAY WILL DEAL WITH CLOUD COVER...AFTERNOON VISIBLE IMAGERY SHOWS ANOTHER PUSH OF LOW CLOUDS LIFTING NORTHWARD ACROSS OHIO WITHIN A ZONE OF ISENTROPIC ASCENT AND SOME FRONTOGENETIC FORCING. LOOKS LIKE SOME OF THIS MOISTURE WILL GRAZE PARTS OF NORTHEAST LOWER AND EASTERN UPPER... POSSIBLY CONTRIBUTING ENOUGH MOISTURE/LIFT TO SQUEEZE OUT SOME DRIZZLE. OTHERWISE EXPECTING TO START THE DAY WITH MORE WIDESPREAD LOW CLOUDS/FOG...THOUGH MAY SEE CLOUDS THIN OUT AND ALLOW FOR SOME SUN LATER IN THE AFTERNOON ACROSS PARTS OF NORTHERN LOWER. MEASURABLE RAIN CHANCES WILL INCREASE TUESDAY NIGHT AS LEAD SHORT WAVE CROSSES THE MISSISSIPPI RIVER AND INTO NORTHERN ILLINOIS BY WEDNESDAY MORNING. NARROW AXIS OF LOW LEVEL MOISTURE INFLOW INTERACTS WITH INCREASING DIVERGENCE IN LEFT EXIT REGION OF A 100KT JET STREAK OVER THE OHIO VALLEY. RAIN EXPECTED TO SPREAD INTO THE REGION FROM SOUTHWEST TO NORTHEAST...NOT REACHING THE ST. MARY`S RIVER UNTIL NEAR DAYBREAK WEDNESDAY. WEDNESDAY...SHORT WAVE OVER ILLINOIS EXPECTED TO LIFT NORTHEAST ACROSS LOWER MICHIGAN DURING THE DAY...AS NEXT PIECE OF ENERGY DIGS IN BEHIND IT OVER IOWA. SOME HINTS OF MID LEVEL DRYING WITH ARRIVAL OF UPPER WAVE...THOUGH AT WORST WILL INCREASE CONVECTIVE INSTABILITY AND ALLOW PRECIPITATION TO BECOME MORE SHOWERY WITH FORECAST CROSS SECTIONS SHOWING A FAIRLY DEEP LAYER BELOW 600MB WITH WEAKER STABILITY. HIGH END POPS STILL JUSTIFIED FOR WEDNESDAY...PERHAPS EVEN AN EMBEDDED THUNDERSTORM WITHIN MID LEVEL COLD POOL. AS UPPER LOW OVER IOWA PIVOTS TOWARD THE UPPER GREAT LAKES WEDNESDAY NIGHT...EXPECT PRECIPITATION FOCUS TO MOVE AWAY FROM NORTHERN MICHIGAN AND TOWARD WISCONSIN/WESTERN UPPER BENEATH DEVELOPING DEFORMATION AXIS...WITH ANOTHER PUSH OF MID LEVEL DRYING POSSIBLE LATER WEDNESDAY NIGHT. WILL KEEP HIGHER POPS ACROSS EASTERN UPPER/FAR NORTHWEST LOWER CLOSER TO DEFORMATION AXIS. ASSOCIATED SURFACE LOW SHOULD TRACK ACROSS CENTRAL LAKE MICHIGAN UP TOWARD THE STRAITS/ EASTERN UPPER BY THURSDAY MORNING. UPSTREAM WAVE NOT EXPECTED TO HAVE MUCH OF A SURFACE RESPONSE WITH IT...BUT ASSOCIATED COLDER AIR WILL FILTER DOWN ACROSS THE CENTRAL U.S./OHIO VALLEY AND REINFORCE COLD FRONT ASSOCIATED WITH THE LOW MOVING THROUGH NORTHERN MICHIGAN WEDNESDAY NIGHT. WITH MAIN COLD AIR PUSH SOUTH OF THE STATE...LOOKS LIKE NORTHERN MICHIGAN WILL REMAIN ON THE WARMER SIDE OF THIS SYSTEM THROUGH WEDNESDAY NIGHT...AND THUS PRECIP TYPE EXPECTED TO REMAIN ALL RAIN AT THIS POINT. SO A WET PRE- THANKSGIVING TRAVEL DAY EXPECTED...BUT WINTRY PRECIPITATION NOT EXPECTED TO HAMPER THINGS. EXTENDED FORECAST (THURSDAY THROUGH MONDAY)...THANKSGIVING DAY LOOKS TO START WITH LOW PRESSURE IN THE VICINITY OF THE STRAITS/EASTERN UPPER MICHIGAN...WITH A DEFORMATION DRIVEN PRECIPITATION BAND ACROSS WISCONSIN/UPPER MICHIGAN (MAYBE SOME SNOW ON THE BACK EDGE). NORTHERN MICHIGAN WILL STILL BE ON THE WARM SIDE OF THE SYSTEM... WITH DRY SLOTTING POTENTIALLY COMPLICATING THE PRECIP/SKY FORECAST FOR THANKSGIVING DAY. IN GENERAL THE AFTERNOON MAY NOT TURN OUT THAT TERRIBLE (AT LEAST ACROSS LOWER MICHIGAN)...BUT WON`T WORRY ABOUT THE SMALLER SCALE DETAILS AT THIS POINT. RAIN CHANCES WILL CONTINUE FOR THURSDAY...THEN WITH WHAT REMAINS OF DEFORMATION ZONE PRECIP THURSDAY NIGHT INTO FRIDAY AS UPPER LOW OPENS UP AND SWINGS ACROSS THE LOWER GREAT LAKES. WILL MENTION MIXED RAIN/SNOW FOR THURSDAY NIGHT AS OPPOSED TO ALL SNOW. WILL EVENTUALLY NEED TO EVALUATE POTENTIAL FOR SOME LAKE INDUCED CONVECTION FRIDAY NIGHT GOING INTO SATURDAY... A LITTLE IFFY WHETHER ENOUGH COLD AIR WILL COME DOWN AND/OR WHETHER LOW LEVEL MOISTURE/CYCLONIC FLOW WILL HANG ON. FOR NOW WILL MAINTAIN CURRENT FORECAST CONTINUITY AND KEEP FRIDAY NIGHT/SATURDAY DRY. BIGGER ISSUES CREEP INTO THE FORECAST FOR THE START OF NEXT WEEK...WITH A MYRIAD OF POSSIBILITIES WITH NEXT ROUND OF PACIFIC ENERGY MOVING INTO THE WESTERN U.S. REGARDING TIMING/NORTHERN VERSUS SOUTHERN BRANCH EMPHASIS/DOWNSTREAM WAVELENGTH ISSUES. THOUGH SOME CONSENSUS LEANING TOWARD THE FASTER/MORE SOUTHERN BRANCH GGEM SOLUTION...NOT CONFIDENT ENOUGH IN BITING OFF ANYTHING AT THIS POINT. WILL INTRODUCE PRECIP CHANCES INTO THE SUNDAY NIGHT/MONDAY TIME FRAME...AND HOLD ONTO A DRY SUNDAY FOR NOW. TEMPERATURES LOOK TO CONTINUE TO AVERAGE NEAR TO A LITTLE ABOVE NORMAL THROUGH THE EXTENDED PERIOD...WITHOUT A SIGNIFICANT PUSH OF COLD AIR IN THE OFFING. JPB && .MARINE.../ISSUED AT 357 PM/ GENERALLY LIGHT SOUTH TO SOUTHEAST FLOW EXPECTED TUESDAY WITH THE UPPER LAKES BETWEEN HIGH PRESSURE TO THE EAST AND APPROACHING LOW PRESSURE FROM THE SOUTHWEST. WINDS WILL BACK AROUND TOWARD MORE OF AN EASTERLY DIRECTION TUESDAY NIGHT AS THE SURFACE LOW LIFTS NORTHEAST INTO LAKE MICHIGAN WEDNESDAY MORNING. LOW THEN EXPECTED TO CROSS THE AREA IN THE VICINITY OF THE STRAITS/EASTERN UPPER MICHIGAN WEDNESDAY NIGHT INTO THURSDAY. SO WIND DIRECTIONS WILL VARY ACROSS THE NEARSHORE ZONES RELATIVE TO LOCATION VERSUS SURFACE LOW POSITION. BUT HEADLINE CRITERIA CONDITIONS NOT ANTICIPATED THROUGH THANKSGIVING DAY MORNING. JPB && .AVIATION.../ISSUED AT 600 AM/...VALID FOR 00Z TAFS MVFR CONDITIONS WILL DETERIORATE TO IFR OVERNIGHT AND INTO TUESDAY MORNING AS LOW STRATUS AND FOG CONTINUE TO HANG OVER THE AREA. CONDITIONS WILL AGAIN IMPROVE TO MVFR BY MIDDAY TUESDAY. WINDS WILL REMAIN AOB 10 KTS. && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. LH...NONE. LS...NONE. && $$