Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 240724
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
324 AM EDT THU JUL 24 2014

LATEST UPDATE...
SYNOPSIS/SHORT TERM/LONG TERM/MARINE

.SYNOPSIS...
ISSUED AT 324 AM EDT THU JUL 24 2014

HIGH PRESSURE WILL DRIFT OVER MICHIGAN TODAY RESULTING IN LOTS OF
SUNSHINE AND LOWER HUMIDITY. A WARM FRONT APPROACHING LATE FRIDAY
AND SATURDAY WILL PROVIDE THE NEXT OPPORTUNITY FOR SHOWERS AND
THUNDERSTORMS. ANOTHER STRONGER COLD FRONT WILL MOVE TROUGH THE
REGION EARLY NEXT WEEK DELIVERING ANOTHER SHOT OF COOL AIR TO THE
GREAT LAKES.

&&

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 324 AM EDT THU JUL 24 2014

ANOTHER QUIET WEATHER DAY IS EXPECTED AS HIGH PRESSURE SETTLES OVER
LOWER MICHIGAN. COOLER THAN NORMAL TEMPS IN THE MID 70S ARE EXPECTED
TODAY. DEWPOINTS AROUND 50 WILL PROVIDE VERY COMFORTABLE CONDITIONS.

AS THE HIGH MOVES EAST FRIDAY LOW PRESSURE IN THE PLAINS WILL PUSH A
WARM FRONT TOWARD LOWER MICHIGAN. IT LOOKS LIKE THE PCPN POTENTIAL
WILL BE FRIDAY NIGHT AND SATURDAY. INSTABILITY IS CLEARLY ELEVATED
FRIDAY NIGHT AS  IS TYPICALLY THE CASE AHEAD OF A WARM FRONT.
SHEAR VALUES AROUND 40 KTS SUGGEST THE POTENTIAL FOR SOME STORMS TO
ORGANIZE BOTH FRIDAY NIGHT AND SATURDAY. STORMS MAY BECOME MORE
SFC-BASED SATURDAY AS THE LOW PUSHING THE WARM FRONT PHASES WITH
ANOTHER STRONGER LOW MOVING SOUTHEAST FROM MANITOBA. SHEAR VALUES
REMAIN NEAR 40 KTS SUNDAY AND MUCAPE CLIMBS TO 2500 J/KG.

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 324 AM EDT THU JUL 24 2014

THE MOST SIGNIFICANT ASPECT OF THIS FORECAST IS THE COOLER THAN
NORMAL TEMPERATURES THAT WILL DOMINATE MOST OF THIS TIME PERIOD.
THE MOST LIKELY TIME FOR SHOWERS AND THUNDERSTORMS WILL BE SUNDAY
AFTERNOON INTO EARLY MONDAY AS THE COLDER AIR MOVES INTO THE AREA.
SOME OF THE STORMS SUNDAY AFTERNOON INTO SUNDAY EVENING COULD BE
STRONG TO SEVERE AS THE AIR AHEAD OF THE COLD FRONT WILL BE FAIRLY
UNSTABLE.

THE MODELS ARE IN GOOD AGREEMENT WITH THE DEVELOPMENT OF AN
UNSEASONABLY DEEP EASTERN CONUS TROUGH BY MONDAY. THIS TROUGH IS
AROUND 3 STANDARD DEVIATIONS FROM NORMAL AT 1000 MB...850 MB AND 500
MB BY MONDAY MORNING. EVEN BY WEDNESDAY THE 700 MB THROUGH 250 MB
HEIGHTS REMAIN OVER 3 STANDARD DEVIATIONS FROM BELOW NORMAL OVER
MOST OF THE EASTERN CONUS. NOT TO SURPRISINGLY THE SURFACE
TEMPERATURES ASSOCIATED WITH THIS WILL ALSO BE IN THE RANGE OF 2 TO
3 STANDARD DEVIATIONS BELOW NORMAL ONCE THE COLD FRONT COMES THROUGH
EARLY MONDAY.

AS I INDICATED YESTERDAY...IT SEEMS ROSSBY WAVE ROSSBY PROPAGATION
FROM THE RECURVING OF WESTERN PACIFIC TYPHOON MATMO IS HELPING THE
CAUSE OF DEEPENING THIS TROUGH. ONCE IN PLACE THERE IS NO UPSTREAM
SYSTEM STRONG ENOUGH TO DISLODGE IT THROUGH THE END OF NEXT WEEK. SO
FOR THE MOST PART... SOUTHWEST LOWER MICHIGAN WILL REMAIN UNDER AN
UNSEASONABLY DEEP UPPER LOW THROUGH MOST OF THE WEEK. ALSO LIKE
YESTERDAY... I FAVOR THE SLOWER AND DEEPER ECMWF SOLUTION. I HAVE TO
ADMIT THROUGH THE 00Z RUNS OF BOTH MODELS ARE SIGNIFICANTLY MORE
SIMILAR TONIGHT THAN LAST NIGHT.

THE PASSAGE OF THE COLD FRONT WITH SUCH A STRONG UPPER AIR SYSTEM
SUNDAY AFTERNOON INTO EARLY MONDAY WILL GIVE MOST AREAS SOME
THUNDERSTORM ACTIVITY. THE DIGGING UPPER LEVEL JET HELPING THE
DEEPENING OF THIS SYSTEM WILL BE SOUTH AND WEST OF LOWER MICHIGAN
SUNDAY EVENING. EVEN SO THE GFS SUGGEST SOUTHWEST LOWER MICHIGAN
WILL HAVE 40 TO 45 KNOTS OF DEEP LAYER SHEAR WITH 1500 J/KG OF CAPE
SUNDAY AFTERNOON INTO SUNDAY EVENING AHEAD OF THE COLD FRONT. SO WE
WILL HAVE TO WATCH OF THE POTENTLY OF STRONG THUNDERSTORMS NONE THE
LESS. ONE OTHER POINT HERE... SUNDAY COULD BE FAIRLY WARM...HIGHS
COULD WELL BE IN THE LOWER 80S BASED ON 1000/850 THICKNESS VALUES
AND 850 TEMPERATURES.

BEYOND SUNDAY... WITH A DEEP UPPER LOW LIKE THAT OVER THE GREAT
LAKES I WOULD HAVE TO IMAGINE AFTERNOON SHOWERS AND THUNDERSTORMS
WOULD BE POSSIBLE EACH DAY. THE MODELS SUGGEST A SHORTWAVE ROTATING
AROUND THE UPPER LOW WILL ENHANCE THE CONVECTION WEDNESDAY. HIGHS
WILL LIKELY BE IN THE UPPER 60S TO MID 70S MON THROUGH WED AND LOWS
WILL MOSTLY BE IN THE 50S BUT 40S ARE POSSIBLE IN THE NORMALLY
COOLER AREAS NORTH OF GRAND RAPIDS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1109 PM EDT WED JUL 23 2014

HIGH PRESSURE BUILDING INTO THE REGION WILL SUPPORT GENERALLY VFR
WEATHER THROUGH THURSDAY. SOME HIGH LEVEL CLOUDS ARRIVE THU NIGHT.
THE WEAKENING PRESSURE GRADIENT WILL ACT TO KEEP WINDS MOSTLY
UNDER 10 KNOTS. A SMALL RISK FOR FOG DOES EXIST LATE TONIGHT...BUT
THE POTENTIAL IS TOO SMALL TO ADD IT TO THE TAFS AT THIS TIME.


&&

.MARINE...
ISSUED AT 324 AM EDT THU JUL 24 2014

BASED ON BUOY OBS AND SFC WINDS WE CANCELLED THE SCA OVER THE
SOUTHERN NSH AREA. WAVES HAD BEEN DECREASING MUCH OF THE EVENING AND
ARE LIKELY AOB 3 FEET. LIGHT WINDS EXPECTED TODAY WITH HIGH PRESSURE
OVERHEAD.

&&

.HYDROLOGY...
ISSUED AT 329 PM EDT WED JUL 23 2014

NO HYDROLOGY ISSUES ARE EXPECTED THROUGH THE END OF THE WEEK AS DRY
WEATHER IS EXPECTED THROUGH FRI. RAINFALL FROM LAST NIGHT OF 1 TO 2
INCHES ALONG THE LAKESHORE DOES NOT LOOK TO HAVE CAUSED SIGNIFICANT
ISSUES. IT WILL JUST KEEP RIVER AND STREAM LEVELS ABOVE AVERAGE TO
MUCH ABOVE AVERAGE...WITHOUT ANY FLOODING EXPECTED AT THIS TIME.
RIVERS AND STREAMS WILL HAVE A CHANCE TO RECOVER A BIT THROUGH THE
END OF THE WEEK.

PCPN CHCS WILL RETURN TO THE AREA FRI NIGHT/SAT. PRECIPITATION
CHANCES AND AMOUNTS ARE STILL A BIT OF UNCERTAIN...SO EFFECTS ON THE
RIVERS ARE ALSO UNCERTAIN. THIS WILL CONTINUED TO BE MONITORED.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
&&

$$

SYNOPSIS...93
SHORT TERM...93
LONG TERM...WDM
AVIATION...MJS
HYDROLOGY...NJJ
MARINE...93








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