813
FXUS63 KGRR 121113
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
714 AM EDT MON MAY 12 2008
LATEST UPDATE...AVIATION...
SYNOPSIS
(326 AM EDT MON MAY 12 2008)
LOW PRESSURE IN EASTERN OHIO WILL CONTINUE TO MOVE AWAY FROM THE
REGION TODAY. WE/LL START OFF ON THE CLOUDY SIDE AND THEN SEE SOME
SUN FROM WEST TO EAST DURING THE LATE MORNING AND AFTERNOON.
TEMPERATURES WILL WARM INTO THE 70S TUESDAY AHEAD OF A COLD FRONT
THAT WILL MOVE THROUGH TUESDAY NIGHT AND WEDNESDAY. WE/LL SEE
SHOWERS AND THUNDERSTORMS ALONG AND AHEAD OF THE FRONT WEDNESDAY.
SHORT TERM
(326 AM EDT MON MAY 12 2008)
(TODAY THROUGH WEDNESDAY)
IR LOOP SHOWS THE BACK OF THE CLOUDS MOVING ACROSS LAKE MICHIGAN
ATTM. SKIES ARE CLEAR TO PT CLDY ALL THE WAY BACK TO THE PLAINS.
WE/LL SEE DECREASING CLOUDINESS TODAY AS A RIDGE MOVES OVERHEAD.
TODAY/S HIGHS WILL BE 10 DEGREES OR SO BELOW AVERAGE. THE NEXT WX
MAKER WILL BE A COLD FRONT THAT MOVES INTO THE REGION TUESDAY NIGHT.
THERE IS SOME ELEVATED INSTABILITY ALONG/AHEAD OF THE FRONT AS LI/S
FALL TO AROUND -4C. 0-6KM BULK SHEAR IS PROGD AROUND 50 KTS...WHICH
SUGGESTS THAT SOME OF THE STORMS THAT DO DEVELOP COULD BE CAPABLE OF
PRODUCING GUSTY WINDS. THERE IS ALSO A DECENT RIBBON OF MOISTURE
CONVERGENCE ALONG THE FRONT THAT/S AIDED BY A 45KT LLJ. ADDED
THUNDER TO THE WRN CWA TUE EVENING AND INCREASED POPS TO LIKELY OVER
THE WRN CWA AFTER MIDNIGHT. ON WED AS THE FRONT MOVES EAST...POPS
DECREASE FROM WEST TO EAST.
LONG TERM
(326 AM EDT MON MAY 12 2008)
(WEDNESDAY NIGHT THROUGH SUNDAY)
OVERALL THE TREND IS TOWARD A PERSISTENTLY COOLER THAN NORMAL
WEATHER PATTERN. THIS SEEMS LIKELY TO CONTINUE THROUGH THE REMAINDER
OF MAY FOR THE WESTERN GREAT LAKES. LARGELY THIS IS THE RESULT OF A
COMBINATION OF MJO TYPE CONVECTION NEAR INDONESIA AND INDIA PLUS THE
COOLER THAN NORMAL WATERS OF THE EASTERN PACIFIC ALONG BOTH THE NA
AND SA COAST (LA NINA /NEG PDO PATTERN) HELPING TO KEEP THAT
CONVECTION FROM PROGRESSING FAR ENOUGH TO THE EAST LIKE IT OTHERWISE
WOULD.
IN ANY EVENT THE ECMWF...GFS...GFS ENSEMBLES AND THE CANADIAN ALL GO
ALONG WITH THE IDEA OF A WESTERN RIDGE AND CENTRAL UNITED STATES
TROUGH THE FOR THE MOST PART IS PERSISTENT. PACIFIC SHORTWAVES SEEM
TO WANT TO CLIMB OVER THE WESTERN RIDGE THEN DIVE INTO THE CENTRAL
UNITED STATES. AN ESPECIALLY STRONG PACIFIC SHORTWAVE WILL CARVE OUT
AN UNSEASONABLY DEEP CLOSED UPPER LOW OVER THE GREAT LAKES BY LATE
THIS COMING WEEKEND. ONCE OVER THE WESTERN GREAT LAKES THE VERTICAL
TOTALS ARE NEAR 30C AND SHOWALTER INDEX IS NEAR 0C. THUS AFTERNOON
THUNDERSTORMS SEEM A GOOD BET IF ALL OF THE ABOVE ACTUALLY OCCURS.
ALSO BASED ON 1000 TO 925 MB THICKNESS FORECAST FIELDS... HIGHS
WOULD MOSTLY STAY IN THE 50S ONCE THIS ALL SETS UP LATE IN THE
WEEKEND INTO EARLY NEXT WEEK.
PRIOR TO THAT THOUGH THERE WOULD BE A SURGE OF WARMER AIR BEHIND THE
INITIAL COOL PUSH THURSDAY. FRI AND SATURDAY COULD END UP BEING
NEAR TO ABOVE NORMAL IN TEMPERATURE DUE TO THE SURGE OF WARM AIR
AHEAD OF THE POLAR FRONT. CLEARLY CONVECTION WOULD BE EXPECTED FRI
INTO SATURDAY AS MID LEVEL HEIGHT FIELD COLLAPSES DUE TO MID LEVEL
COLD ADVECTION ASSOCIATED WITH THE DIGGING PACIFIC WAVE (500 TEMPS
FALL WHILE 850 MB TEMPERATURES RISE). 500 MB TEMPERATURES FALL TO
NEAR -30C BY SUNDAY AFTERNOON OVER CNTRL GREAT LAKES.
MARINE
(326 AM EDT MON MAY 12 2008)
WE/LL KEEP THE SCA GOING TODAY AS WAVES WILL REMAIN IN THE 3-5 FT
RANGE DUE TO NORTHWEST WINDS.
AVIATION
(714 AM EDT MON MAY 12 2008)
A SURGE OF COLDER AIR AT LOW LEVELS (NEAR 925 MB) HAS BEEN
ACCOMPANIED BY LOW CEILINGS... IN THE 1000 TO 1500 FOOT RANGE. AS
THEY EAST COAST SYSTEM SLOWLY PULLS AWAY FROM THE COAST THE HIGH
PRESSURE RIDGE WEST OF HERE WILL MOVE IN AND TURN OUR LOW LEVELS
WINDS ANTICYCLONIC. THAT SHOULD ALLOW THE CLOUDS TO MIX OUT BY MID
DAY. THERE STILL WILL BE ENOUGH MOISTURE FOR SOME CU TO DEVELOP SO
SKIES WILL NOT CLEAR TILL EVENING WHEN THE SURFACE TO 850 MB RIDGE
AXIS OVERHEAD TONIGHT. SKIES SHOULD BECOME MOSTLY CLEAR BY SUNSET
ACROSS THE CWA.
HYDROLOGY
(326 AM EDT MON MAY 12 2008)
A HALF INCH TO AN INCH OF RAIN HAS FALLEN ACROSS THE AREA. THIS WILL
RESULT IN SOME RISES ON AREA STREAMS AND RIVERS BUT SHOULD OTHERWISE
NOT POSE A HAZARD.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LM...SMALL CRAFT ADVISORY IN EFFECT TODAY FROM ST JOE TO MANISTEE.
SYNOPSIS: 93
SHORT TERM: 93
LONG TERM: WDM
MARINE 93
AVIATION: WDM
HYDROLOGY: 93
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page