042 FXUS63 KAPX 292010 AFDAPX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 410 PM EDT SUN APR 29 2012 .SYNOPSIS... ISSUED AT 408 PM EDT SUN APR 29 2012 CANADIAN HIGH PRESSURE WILL SLIDE INTO THE NORTHEAST STATES TONIGHT...WHILE WEAK LOW PRESSURE FORMS OVER MISSOURI. CLOUDS WILL THICKEN TONIGHT...AS THE LOW MOVES EAST...TRACKING ALONG THE SOUTHERN MICHIGAN BORDER MONDAY. AS THIS OCCURS...A PERIOD OF LIGHT RAIN WILL FALL...MAINLY IN THE MORNING. IMPROVEMENT WILL OCCUR TUESDAY...AS WEAK HIGH PRESSURE SLIDES OVER THE GREAT LAKES...AND TEMPERATURES TURN MUCH WARMER. SKIES WILL BE PARTLY TO MOSTLY CLOUDY FROM TUESDAY ALL THE WAY INTO NEXT WEEKEND...WITH PERIODIC CHANCES FOR RAIN AND SOME THUNDERSTORMS. && .SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT) ISSUED AT 408 PM EDT SUN APR 29 2012 AFTERNOON SYNOPSIS: CIRRUS BLOWOFF FROM ADVANCING PRECIPITATION SHIELD ACROSS NORTHERN MISSOURI/SOUTHERN IOWA/WESTERN ILLINOIS SPREAD ACROSS THE FORECAST AREA AT MID AFTERNOON...THOUGH STILL QUITE THIN WITH PLENTY OF SUN ACROSS NORTHERN MICHIGAN. TEMPERATURES HAVE WARMED INTO THE UPPER 50S/LOWER 60S ACROSS INTERIOR SECTIONS OF EASTERN UPPER/NORTHERN LOWER...WITH VARIOUS LAKE IMPACTS IN EVIDENCE ALONG THE LAKESHORES WITH ONSHORE BREEZES AND COOLER TEMPERATURES/HIGHER DEW POINTS. INTERIOR RELATIVE HUMIDITY VALUES HAVE DROPPED INTO THE 10-15 PERCENT RANGE. UPPER LEVEL RIDGE AXIS LYING ACROSS THE UPPER GREAT LAKES AT MID AFTERNOON...SANDWICHED BETWEEN UPPER LOWS OVER ATLANTIC CANADA AND THE DAKOTAS RESPECTIVELY. EASTERN UPPER TROUGH WILL GIVE WAY SLOWLY...ALLOWING HEIGHTS TO FALL ACROSS THE UPPER LAKES. WATER VAPOR IMAGERY SHOWS SHORT WAVE ENERGY LIFTING QUICKLY NORTHEAST ACROSS WESTERN KANSAS...AND WILL MAKE A BEELINE TOWARD FORECAST OVERNIGHT AND IS FORECAST TO CROSS MICHIGAN MONDAY. SURFACE HIGH ACROSS THE GREAT LAKES WILL ALSO SLIDE EAST TONIGHT...LOW PRESSURE NEAR THE OZARKS THIS AFTERNOON (WITH AN ATTENDANT WARM FRONT THAT EXTENDS EAST INTO KENTUCKY) WILL BE DRAWN NORTHWARD INTO THE OHIO VALLEY IN RESPONSE BY MONDAY MORNING. WILL BE WATCHING MIDWEST PRECIPITATION AREA AS IT TRACKS NORTHEAST TOWARD THE UPPER GREAT LAKES TONIGHT. CLOUDS WILL BEGIN TO THICKEN UP FROM THE SOUTHWEST THIS EVENING...BUT WILL TAKE SOME IMPROVED LOW LEVEL MOIST INFLOW TO OVERCOME EXISTING DRY AIR MASS IN PLACE ACROSS NORTHERN MICHIGAN...SO INITIAL PRECIPITATION WILL PROBABLY RESULT IN A DECENT VIRGA STORM. SYNOPTIC LOW LEVEL JET TAKES AIM ON LOWER MICHIGAN DURING THE PRE-DAWN HOURS MONDAY MORNING...PULLING 1 INCH PRECIPITABLE WATER VALUES INTO THE STATE. MID LEVEL SHORT WAVE TROUGHING WILL ADD SOME DYNAMIC SUPPORT TO PRECIPITATION CHANCES... PLAN TO CARRY CATEGORICAL POPS ACROSS MUCH OF NORTHERN LOWER STARTING AFTER 06Z MONDAY AND CONTINUING THROUGH MIDDAY. AS MID LEVEL SHORT WAVE PUSHES EAST... MID LEVELS EXPECTED TO DRY OUT FROM WEST TO EAST...THOUGH PLENTY OF LOW LEVEL MOISTURE REMAINS BEHIND. SO EXPECT MEASURABLE RAINFALL TO TAPER OFF TO PERIODS OF DRIZZLE DURING THE AFTERNOON WITH CLOUDS PERSISTING. .LONG TERM...(TUESDAY THROUGH SUNDAY) ISSUED AT 408 PM EDT SUN APR 29 2012 A WARMER AND MORE MOIST SOUTHERLY FLOW IS STILL EXPECTED TO KICK IN FOR TUESDAY THROUGH THURSDAY. EXTENDED MODELS THEN BRING A WEAK COLD FRONT ACROSS THE REGION SOMETIME LATER THURSDAY OR THURSDAY NIGHT. THE UPPER FLOW LOOKS LIKE IT WILL BECOME NEARLY ZONAL FOR FRIDAY AND CONTINUE INTO NEXT WEEKEND. THE MAIN LONG TERM FORECAST CONCERNS REVOLVE AROUND POPS AND THUNDER CHANCES PRETTY MUCH THROUGH THE ENTIRE FORECAST. MONDAY NIGHT...TOUGH CLOUD FORECAST AS WE GET INTO WEAK SURFACE RIDGING...BUT A LACK OF FLOW MAY NOT BE ENOUGH TO SCOUR OUT REMAINING LOW LEVEL MOISTURE. MODEL SOUNDINGS/CROSS SECTIONS LOOK NEARLY SATURATED. SO WILL ONLY GO WITH PARTIAL CLEARING (WHICH MAY END UP BEING OVERLY AMBITIOUS) WITH LOWS RANGING FROM THE MILDER MIDDLE 30S TO LOWER 40S. TUESDAY...THE WEAK SURFACE RIDGE MOVES OFF TO THE EAST BY MIDDAY. BETTER CHANCE TO SCOUR OUT LOW LEVEL MOISTURE WITH SLOWLY INCREASING SOUTHERLY WINDS. HOWEVER...MID LEVELS SLOWLY MOISTEN DUE TO WARM ADVECTION ALOFT. OVERALL...PARTLY TO MOSTLY CLOUDY SKIES SHOULD WORK. HIGHS RANGING FROM THE MILDER LOWER AND MIDDLE 60S NORTH TO THE UPPER 60S TO LOWER 70S SOUTH. TUESDAY NIGHT THROUGH SUNDAY...A WARMER AND MORE MOIST SOUTHERLY FLOW FINALLY KICKS. SHOWER AND THUNDERSTORM CHANCES INCREASE LATER TUESDAY NIGHT INTO THURSDAY WITH A WARM FRONT LIFTING INTO THE AREA....FOLLOWED BY A COLD FRONT AT SOME POINT LATER THURSDAY OR THURSDAY NIGHT. IT IS STILL PRETTY FAR OUT TO GLEAM THE FINER DETAILS...BUT WIND FIELDS LOOK MODEST (BRN SHEAR ABOUT 40 KNOTS) AND WET BULB ZERO HEIGHTS ARE 11,000 FEET OR SO ON WEDNESDAY...SO THE OVERALL SEVERE THREAT LOOKS LOW AT THIS POINT. A NEARLY ZONAL FLOW ALOFT FOLLOWS FOR FRIDAY INTO NEXT WEEKEND WHICH WILL LEAD TO TIMING ISSUES WITH POSSIBLE SHORT WAVES MOVING THROUGH THE FLOW. WILL RUN WITH SLIGHT OR CHANCE POPS FOR RAIN SHOWERS DURING THIS TIME AS INSTABILITY LOOKS LIKE IT WILL BE TOUGH TO COME BY DUE TO ABUNDANT CLOUD COVER. HIGHS IN THE 60S TO MIDDLE 70S WEDNESDAY AND THURSDAY THEN RANGE FROM THE UPPER 50S TO LOWER 60S NORTH TO THE LOWER TO MIDDLE 60S SOUTH FRIDAY THROUGH SUNDAY (MAYBE AS WARM AS THE LOWER 70S SOUTHEAST ON FRIDAY). MILDER THAN WHAT WE SEEN RECENTLY AT NIGHT WITH LOWS IN THE 40S AND 50S FOR THE MOST PART. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON) ISSUED AT 204 PM EDT SUN APR 29 2012 VFR CONDITIONS THROUGH MIDNIGHT...LOWERING CEILINGS OVERNIGHT AS RAIN APPROACHES FROM THE SOUTHWEST AND WILL OVERSPREAD THE TERMINAL MONDAY MORNING WITH MOSTLY MVFR CONDITIONS THOUGH MAY SEE IFR CEILINGS MID/LATE MONDAY MORNING. LOW LEVEL WIND SHEAR ALSO A CONCERN TONIGHT. && .MARINE... ISSUED AT 408 PM EDT SUN APR 29 2012 HIGH PRESSURE RIDGE CENTERED OVER THE UPPER GREAT LAKES THIS AFTERNOON WILL SLIDE TO THE EAST TONIGHT...BRINGING A TIGHTER SOUTHEASTERLY GRADIENT ACROSS NORTHERN MICHIGAN OVERNIGHT INTO THE FIRST PART OF MONDAY. MARGINAL SMALL CRAFT CONDITIONS ANTICIPATED AT THIS POINT LATER TONIGHT INTO MONDAY...LOOKS LIKE GREATEST THREAT WILL BE WITHIN LAKE HURON NEARSHORE ZONES UP INTO THE ST. MARY'S RIVER/WHITEFISH BAY. WINDS LOOK TO DIMINISH AGAIN MONDAY NIGHT. && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LH...NONE. LM...NONE. LS...NONE. && $$ SYNOPSIS...JH SHORT TERM...JB LONG TERM...AS MARINE...JB