Area Forecast Discussion - VPWW's Weather Forecast Office Detroit/Wyandotte


AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 134 PM EDT SAT APR 24 2010 .AVIATION... VFR CONDITIONS WILL CONTINUE THROUGH MOST THE EVENING AS DRY AIR IN THE LOW LEVELS HAS MANAGED TO KEEP CEILINGS AOA 5000 FT. A SECOND LINE OF SHOWERS IS CURRENTLY CROSSING INTO EXTREME SOUTHERN MICHIGAN AND HAS THE POTENTIAL TO BRIEFLY LOWER CEILINGS INTO MVFR CATEGORY BUT WITH ALL THE DRY AIR IN PLACE...DECIDED TO LEAVE OUT OF THE TAF AT THIS POINT. MUCH BETTER CHANCES FOR HEAVY RAIN WILL OCCUR LATER TONIGHT AS A STRONG LOW PRESSURE SYSTEM MOVES INTO THE ILLINOIS AREA AND LIFTS A WARM FRONT ACROSS SOUTHEAST MICHIGAN. CEILINGS WILL LIKELY DROP TO LOW END MVFR/HIGH END IFR BY EARLY TOMORROW MORNING AND CONTINUE THROUGH MOST OF THE DAY. A FEW THUNDERSTORMS CAN NOT BE COMPLETELY RULED OUT ACROSS THE SOUTHERN TAF SITES WITH THE PASSAGE OF THIS FRONT. && .PREV DISCUSSION...ISSUED 1150 AM EDT SAT APR 24 2010 UPDATE... KDTX RADAR THIS MORNING SHOWING POCKETS OF SHOWER ACTIVITY BREAKING OUT ACROSS SOUTHEASTERN MICHIGAN ALONG/WITHIN LEAD MIDLEVEL (850-700MB) THETA E PUSH. THERE HASN`T BEEN MUCH MEASURING GOING ON WITH THE TIPPING BUCKETS...HOWEVER...AS THE ONLY STATIONS REPORTING A HUNDREDTH OR GREATER THIS MORNING HAS BEEN AT ADG/ARB/YIP. BULK OF THE ORGANIZED ACTIVITY THE PAST HOUR OR TWO HAS ACTUALLY BEEN OVER THE TRI CITIES REGION. THIS APPEARS TO BE IN RESPONSE TO ARRIVAL OF THE MOISTURE WITHIN ZONE OF GREATER DEFORMATION TUCKED UNDER WESTERN FLANK OF UPPER LEVEL RIDGE AXIS. SURFACE DEWPOINT DEPRESSIONS REMAIN SIGNIFICANT EVERYWHERE...UPWARDS OF 20 DEGREES...SO EXPECTING QUITE A BIT OF VIRGA ACTIVITY. NEVERTHELESS...WILL RAMP POPS FOR THE TRI CITIES FOR THE EARLY AFTERNOON HOURS. DETERMINISTIC AND HI RESOLUTION RUNS HAVE A VERY POOR HANDLE ON THIS ACTIVITY...BUT WOULD NOT BE SURPRISED TO SEE THIS LINGER ON RADAR IMAGERY FOR A FEW HOURS. AGAIN...NOT EXPECTING MUCH MORE THAN SPRINKLES OR LIGHT RAIN SHOWERS GIVEN SUB 7000 FT AGL DRY LAYER. A SWATH OF LARGE SCALE SUBSIDENCE WILL LIFT INTO SOUTHEASTERN MICHIGAN DURING THE AFTERNOON HOURS FROM SOUTH TO NORTH. THIS WILL REINTRODUCE DRY AIR BACK INTO THE LAYER ABOVE 600MB AND EXPECT THIS TO REALLY SERVE AS A LIMITING FACTOR IN SHOWER GENERATION THIS AFTERNOON. A VERY WEAK SHORTWAVE IS LOCATED OVER EAST CENTRAL INDIANA ATTM. WILL WATCH THIS FEATURE AS IT LIFTS INTO FAR SOUTHEASTERN MICHIGAN THIS AFTERNOON FOR SHOWER DEVELOPMENT AS MODEL GUIDANCE SUPPORTS AN UPTICK IN PRECIPITATION ALONG AN ASSOCIATED THERMAL GRADIENT. GIVEN THE DRAMATIC ERODING OF REFLECTIVITIES IN NE IN - NW OH...NOT CONVINCED MUCH WILL HAPPEN. WILL BACK OFF ON POPS FOR THE AFTERNOON...BUT WILL MAINTAIN A TOKEN CHANCE PROBABILITY FOR ALL AREAS TO ACCOUNT FOR ONGOING ISENTROPIC LIFT REGIME. WILL MAKE POP AND OBSERVATIONAL CHANGES TO THE GRIDS AND SEND OUT AN UPDATED ZONES FORECAST. PREV DISCUSSION...ISSUED 400 AM EDT SAT APR 24 2010 SHORT TERM...TODAY A DRY EASTERLY FEED CONTINUES TO KEEP THE MIDDLE AND LOWER LEVELS QUITE DRY ACROSS THE CENTRAL GREAT LAKES AS EVIDENCED BY THE 00Z DTX RAOB SOUNDING AND CLOUD DECKS AT OR ABOVE 10K FT. DESPITE RADAR ECHOES ACROSS MUCH OF THE SOUTHERN GREAT LAKES AT THE PRESENT TIME...MUCH OF THIS ACTIVITY IS NOT REACHING THE GROUND PER THE SURROUNDING METAR OBSERVATIONS. MOISTURE ADVECTION FROM THE SOUTH ASSOCIATED WITH THE WARM FRONT LIFTING NORTH FROM THE OHIO VALLEY WILL BRING INCREASED MOISTURE AND CHANCES FOR RAIN AS IT LIFTS TOWARDS THE SOUTHERN GREAT LAKES. THE BATTLE BETWEEN THE DRY AIR AND INCOMING MOISTURE WILL PLAY OUT ACROSS SOUTHERN MICHIGAN TODAY...WITH THE DRY AIR HAVING THE UPPER HAND FOR MUCH OF THE DAY ACROSS THE NORTH. THE BEST CHANCES FOR PRECIPITATION WILL BE ACROSS THE SOUTH CLOSER TO THE APPROACHING FRONT. WHERE TO DRAW THE PRECIPITATION CHANCES WILL BE THE BIGGEST CHALLENGE TODAY AS THE NAM KEEPS THINGS QUITE DRY FOR MOST IF NOT ALL OF TODAY WHILE THE GFS RAMS THE MOISTURE AND ASSOCIATED QPF ALL THE WAY TO THE INTERSTATE 69 CORRIDOR THIS AFTERNOON. THE CURRENT FORECAST LOOKS TO BE A GOOD BLEND OF THESE TWO SCENARIOS AS THE NAM SEEMS A BIT TOO DRY DESPITE THE ABUNDANT DRY AIR IN PLACE ACROSS SOUTHEAST MICHIGAN GIVEN THE RECENT UPTICK IN THE RADAR REFLECTIVITIES ACROSS NORTHERN INDIANA AND THE GFS SEEMS TOO WET GIVEN THE DRY AIR EXPECTED TO HOLD STRONG ACROSS THE NORTHERN CWA FARTHER AWAY FROM THE FRONT AND BEST MOISTURE. SOME RUMBLES OF THUNDER ARE POSSIBLE ALONG AND SOUTH OF THE M-59 CORRIDOR TODAY WITH ELEVATED THUNDERSTORMS NORTH OF THE WARM FRONT. LONG TERM...TONIGHT THROUGH FRIDAY UPPER SHORTWAVE OVER WEST TEXAS WILL RACE NORTHEAST AND BECOME ABSORBED IN THE LARGE UPPER LOW OVER THE CENTRAL PLAINS TONIGHT. THIS WILL ALLOW AN AREA OF SURFACE LOW PRESSURE TO DEEPEN AS IT LIFTS NORTHEAST TOWARDS THE SOUTHERN GREAT LAKES OVERNIGHT. AS THE LOW APPROACHES...A SECONDARY SURGE OF WARM AIR AND MOISTURE WILL OCCUR. MODELS REMAIN IN GOOD AGREEMENT WITH STRONG CONVERGENCE DEVELOPING ALONG THE SECOND 925MB FRONT TONIGHT AS LIFTS NORTHWARD THROUGH LOWER MICHIGAN. THIS WILL PROVIDE THE NECESSARY FORCING FOR THE DEVELOPMENT OF WIDESPREAD RAIN ACROSS SOUTHEAST MICHIGAN...WITH TOTALS RANGING FROM 0.5 TO JUST OVER 1.0 INCHES. STRONG AND DRY EASTERLY FLOW INTO NORTHERN LOWER MICHIGAN SHOULD BRING ABOUT A SHARP CUTOFF TO THE PRECIPITATION SHIELD...BUT DO THINK THIS EDGE WILL LIFT NORTH OF THE THUMB OVERNIGHT AND LIE ACROSS SOUTH-CENTRAL LAKE HURON BY DAYBREAK. BOTTOM LINE...EVERYONE SHOULD GET WET BY 800 AM AND CHANCE OF RAIN OVERNIGHT IS 100 PERCENT. CONVECTION/THUNDERSTORMS WILL ALSO BE POSSIBLE TONIGHT SOUTH OF THE I-69 CORRIDOR WHERE GOOD ELEVATED INSTABILITY WILL BE LOCATED...WITH A SLIGHTLY BETTER CHANCE TOWARDS THE OHIO BORDER WHERE INSTABILITY MAY BECOME MORE SURFACE BASED. HEAVY RAIN WILL BE THE BIGGEST THREAT FROM ANY STORMS THAT DO DEVELOP GIVEN LIMITED INSTABILITY. RAIN...AND A FEW THUNDERSTORMS ALONG AND SOUTH OF M-59...WILL CONTINUE TO PLAGUE THE AREA SUNDAY AS THE LOW PRESSURE SYSTEM TRACKS VERY SLOWLY EASTWARD THROUGH NORTHERN INDIANA AND OHIO. AREA OF DEFORMATION ON THE NORTH SIDE WILL CONTINUE TO RESIDE OVERHEAD...AND ALTHOUGH ASCENT WITHIN THIS ZONE WILL START TO WEAKEN....IT SHOULD STILL BE ENOUGH TO GENERATE UP TO 0.5 INCHES OF ADDITIONAL RAINFALL. RAIN SHOULD START TO TAPER OFF SUNDAY NIGHT AND MONDAY AS THE LOW CENTER TRACKS ACROSS EASTERN OHIO AND TOWARDS THE EAST COAST. WILL BEGIN TO SEE A REAL DECREASING TREND TO ACTIVITY FIRST ACROSS THE TRI-CITIES AND THUMB SUNDAY NIGHT...THEN CONTINUING NORTHWEST TO SOUTHEAST THROUGH THE REMAINDER OF THE AREA ON MONDAY. HAVE KEPT A MENTION OF SHOWERS THROUGHOUT THE DAY ON MONDAY TO TAKE INTO CONSIDERATION SLOWER TIMING OF SOME MODEL SOLUTIONS WITH THE EASTERLY MOVEMENT TO THE LOW...BUT THE RAIN MAY BE OUT OF HERE BY MID-AFTERNOON. THE FORECAST FOR TUESDAY THROUGH THURSDAY REMAINS DRY AS UPPER RIDGING BUILDS INTO THE GREAT LAKES. HIGH TEMPERATURES WILL MODERATE ONLY SLIGHTLY FROM MONDAY TO TUESDAY...RISING ONLY A FEW DEGREES INTO THE UPPER 50S TO NEAR 60. SHOULD SEE A MORE PRONOUNCED WARMUP AFTER THAT HOWEVER AS BETTER INSOLATION AND LACK OF COLD AIR ADVECTION ALLOW TEMPS TO WARM INTO THE LOW 60S ON WEDNESDAY AND THEN THE MID TO UPPER 60S ON THURSDAY. ONLY CONCERN FOR THIS PERIOD LOOKS TO BE CHILLY TEMPERATURES TUESDAY NIGHT AND ASSOCIATED FROST POTENTIAL. MODELS HAVE BECOME MORE DIVERGENT WITH THE SYNOPTIC PATTERN OVER NORTH AMERICA BY THE END OF THE WEEK...PARTICULARLY WITH THE GFS TRENDING TOWARDS A MORE AMPLIFIED LONGWAVE PATTERN ACROSS THE CONUS. WILL LEAN TOWARDS THE BETTER...AND LESS AMPLIFIED...CONSENSUS OF THE EURO/UKMET/GEM. THESE MODELS ARE LESS AGGRESSIVE WITH RIDGING OVER THE CENTRAL GREAT LAKES...AS BOTH UPSTREAM AND DOWNSTREAM UPPER LOWS ARE LARGER. THIS KEEPS THE BEST CHANCE TO SEE SHOWERS AND THUNDERSTORMS ON FRIDAY...ALTHOUGH IF THE MORE AMPLIFIED GFS PANS OUT FRIDAY WOULD INSTEAD BE DRY BUT VERY WARM. MARINE... A DEVELOPING LOW PRESSURE SYSTEM ACROSS THE CENTRAL PLAINS WILL MOVE EASTWARD TOWARDS THE SOUTHERN GREAT LAKES BY SUNDAY. THE WARM FRONT ASSOCIATED WITH THE LOW WILL LIFT NORTH OUT OF THE OHIO VALLEY AND INTO THE SOUTHERN GREAT LAKES TONIGHT. THIS SYSTEM WILL LEAD TO SEVERAL ROUNDS OF SHOWERS AND SOME POSSIBLE THUNDER THROUGHOUT THE WEEKEND. MODEL GUIDANCE SUGGESTS THAT SURFACE LOW PRESSURE WILL BECOME STRONG...29.00 INCHES...BY SUNDAY MORNING AS IT CROSSES ACROSS THE SOUTHERN LOWER MICHIGAN STATELINE. THIS WILL UNDOUBTEDLY CAUSE WIND CONCERNS ACROSS ALL OF THE GREAT LAKES AS THE GRADIENT INCREASES. THE FIRST TIME PERIOD OF CONCERN WILL BE TODAY FOR THE MICHIGAN WATERS OF LAKE ERIE AS A LONG EASTERLY FETCH SETS UP DOWN THE LONG AXIS OF LAKE ERIE. A SMALL CRAFT ADVISORY IS IN EFFECT FROM 10 AM THROUGH 4 AM SUNDAY MORNING FOR THIS ZONE AS THE HIGH WAVES LOOK TO LAST FOR MUCH OF THE OVERNIGHT HOURS. ATTM..IT APPEARS THE WINDS WILL REMAIN BELOW GALE FORCE FOR THE ENTIRE EVENT GIVEN THE STRONGLY STABLE CONDITIONS THAT WILL BE IN PLACE. IMPRESSIVE...THE NAM AND GFS GENERATE 950MB WINDS THAT REACH 45 KNOTS WITH THE HEIGHT OF THE SYSTEM ON SUNDAY. NOT EXPECTING WINDS QUITE THAT STRONG AT THE SURFACE...HOWEVER...AS AN INCREDIBLY SHARP INVERSION WILL EXIST JUST OFF THE DECK KEEPING WINDSPEEDS BETWEEN 25 AND 30 KNOTS. SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED ACROSS THE LAKE HURON AND SAGINAW BAY ZONES DURING THESE HIGH WINDS. HOWEVER THE CONDITIONS ARE NOT EXPECTED TO REACH SMALL CRAFT ADVISORY CRITERIA UNTIL LATE TONIGHT SO WILL HOLD OFF ON ISSUING ANY HEADLINES FOR NOW. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...NONE. LAKE ST CLAIR...NONE. MI WATERS OF LAKE ERIE... SMALL CRAFT ADVISORY...UNTIL 4 AM SUNDAY. && $$ AVIATION.....CB UPDATE.......CB SHORT TERM...KURIMSKI LONG TERM....HLO MARINE.......KURIMSKI

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