Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 021745
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
145 PM EDT TUE SEP 2 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 328 AM EDT TUE SEP 2 2014

AN ISOLATED SHOWER OR EVEN A THUNDERSTORM CANNOT BE RULED OUT
TODAY...BUT IN GENERALLY MOST AREAS WILL REMAIN DRY. HIGH PRESSURE
WILL PROVIDE DRY WEATHER TONIGHT AND WEDNESDAY. WEDNESDAY NIGHT
THROUGH FRIDAY ACTIVE WEATHER RETURNS TO THE AREA WITH CHANCES FOR
SHOWERS AND THUNDERSTORMS. THE BEST CHANCES FOR RAIN APPEAR TO BE
WEDNESDAY NIGHT INTO THURSDAY MORNING ASSOCIATED WITH A WARM FRONT
AND AGAIN ON FRIDAY ASSOCIATED WITH A COLD FRONTAL PASSAGE.
TEMPERATURES WILL BE NEAR NORMAL TODAY AND WEDNESDAY WITH WARM
READINGS EXPECTED ON THURSDAY SURGING WELL INTO THE 80S. A COOL DOWN
IS EXPECTED INTO THE WEEKEND BEHIND FRIDAY/S COLD FRONT.

&&

.UPDATE...
ISSUED AT 1101 AM EDT TUE SEP 2 2014

STILL THINKING THAT THERE WILL BE A FEW ISOLATED THUNDERSHOWERS
THIS AFTERNOON. THE BEST CHANCES WILL BE WELL NORTH OF I-96 BUT
ALSO A BIT OF A RISK ALONG AND SOUTH OF I-94. THE TIME OF CONCERN
FOR BOTH AREAS WILL BE BETWEEN 100 PM EDT AND 6OO PM EDT THIS
AFTERNOON. LOOKING AT TRACE UPWARDS TO A THIRD OF AN INCH POSSIBLE
WITH THESE SHOWERS...WITH MOST LOCATIONS RECEIVING NO RAIN AT ALL.

WIDELY SCATTERED SHOWERS / ISOLATED THUNDER NOW STRETCHING FROM
NORTHERN WISCONSIN SOUTH TO NORTH-CENTRAL ILLINOIS IS ASSOCIATED
WITH A FAIRLY TIGHT H5-H3 SHORTWAVE TROUGH. IT ALSO LOOKS FROM
RADAR LOOPS LIKE THERE IS A WEAK H7 MESO-CONVECTIVE VORTEX (MCV) ON
THE SOUTH END OF THE FEATURE MOVING EAST-SOUTHEAST ALONG THE
ILLINOIS/WISCONSIN BORDER. THE NORTHERN END OF THE AREA HAS BEEN
DEVELOPING OVER THE PAST COUPLE OF HOURS WHILE THE MCV PORTION HAS
BEEN WEAKENING.

RAP/HRRR/ECMWF INDICATE ML CAPES OF 250-750 J/KG WILL DEVELOP
ACROSS THE AREA AHEAD OF THE APPROACHING DISTURBANCE WITH BULK
SHEAR OF 30 KTS. UP NORTH LOW LEVEL CONVERGENCE IS WEAK...SO LAKE
BREEZE CONVERGENCE AND TERRAIN ROUGHNESS WILL BE THE KEY TO
CONVECTIVE INITIATION. LOW LEVEL CONVERGENCE MAY BE ENHANCED BY
OUTFLOW BOUNDARIES...MCV...AND INTERACTIONS WITH LAKE BREEZE ALONG AND
SOUTH OF I-94. BUT AGAIN...NOT EXPECTING ANYTHING MORE THAN
ISOLATED CONVECTION.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 328 AM EDT TUE SEP 2 2014

RAIN CHANCES ARE NOT NIL TODAY WITH A COOL FRONT STILL PROGRESSING
SOUTH OF THE AREA. THE FRONT IS LOCATED ACROSS SOUTHERN LOWER
MICHIGAN AT 07Z...BUT IT SHOULD SAG SOUTH OF THE AREA THROUGH THE
COURSE OF THE MORNING. ANOTHER CAVEAT TO KEEP AN EYE ON IS A
SHORTWAVE QUICKLY MOVING OUR DIRECTION FROM IOWA. A FEW
SHOWERS/STORMS ARE ASSOCIATED WITH THIS WAVE AS OF 07Z. HAVE
ISOLATED/SCATTERED WORDING IN THE FORECAST TAPERING OFF THIS
AFTERNOON TO DRY/ISOLATED AS DEW POINTS DROP IN THE WAKE OF THE
FRONT. DRY WEATHER IS EXPECTED TONIGHT AND WEDNESDAY WITH SURFACE
HIGH PRESSURE IN PLACE ACROSS THE GREAT LAKES.

FOCUS THEN SHIFTS TO A WARM FRONT SURGING OUR DIRECTION WEDNESDAY
NIGHT. WE WILL PROBABLY NEED TO NUDGE CHANCES FOR SHOWERS/STORMS UP
WEDNESDAY NIGHT INTO THURSDAY MORNING. BUMPED CHANCES UP SOME
ALREADY...BUT THEY MAY NEED TO GO HIGHER. SOLID MOISTURE ADVECTION
IS NOTED AT 850MB/S. THE 850MB DEW POINT ADVECTION SEEN IN ALL THE
MODELS DURING THIS TIME FRAME USUALLY EQUATES TO SOLID COVERAGE OF
SHOWERS/STORMS. ALL OF THE MODELS SHOW NEGATIVE LI/S ADVECTING INTO
THE WESTERN CWA...ESPECIALLY UP TOWARDS LUDINGTON WEDNESDAY NIGHT.

SHOWERS AND STORMS REMAIN POSSIBLE INTO THURSDAY AFTERNOON...BUT
FEEL WE MAY BE STABILIZED BY MORNING CONVECTION SOME. GIVEN
UNCERTAINTY THOUGH IN CONVECTIVE EVOLUTION...HAVE CHANCES RIGHT
THROUGH THE DAY. CLOUDS WILL BE A SIGNIFICANT FACTOR IN THURSDAY/S
HIGH TEMPERATURE FORECAST. AT THIS POINT PLAYING IT IN THE MIDDLE TO
UPPER 80S. WE COULD PUSH TO AROUND 90 THOUGH IF BETTER SUNSHINE IS
REALIZED.

.LONG TERM...(THURSDAY NIGHT THROUGH MONDAY)
ISSUED AT 328 AM EDT TUE SEP 2 2014

SEASONABLY WARM WEATHER WILL CONTINUE THURSDAY NIGHT AND FRIDAY.
A CONSENSUS OF LATEST 00 MEDIUM RANGE GUIDANCE SUGGESTS THAT A
STRONG COLD FRONT WILL BRING POTENTIAL FOR RAIN AND THUNDERSTORMS
THURSDAY NIGHT THROUGH FRIDAY.

HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT BEGINNING FRIDAY NIGHT
THROUGH THE WEEKEND RESULTING IN PARTLY CLOUDY TO MOSTLY CLEAR SKIES
AND MUCH COOLER TEMPS. MAX TEMPS THIS WEEKEND WILL ONLY REACH THE
UPPER 60S TO LOWER 70S WITH MIN TEMPS MAINLY IN THE 40S TO LOWER
50S. THE RIDGE SHOULD REMAIN IN CONTROL OF THE WX PATTERN FOR NEXT
MONDAY AND BRING FAIR WX WITH SEASONABLE TEMPS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 144 PM EDT TUE SEP 2 2014

AN UPPER DISTURBANCE MOVING ACROSS LOWER MICHGIAN WILL DEPART BY
LATE AFTERNOON. VFR EXPECTED THROUGH THE PERIOD.

&&

.MARINE...
ISSUED AT 328 AM EDT TUE SEP 2 2014

FAIRLY BENIGN CONDITIONS ARE EXPECTED OUT ON THE BIG LAKE TODAY INTO
WEDNESDAY AS HIGH PRESSURE SETTLES INTO THE AREA. WAVES FOR THE MOST
PART TODAY...TONIGHT AND WEDNESDAY WILL BE 2 FEET OR LESS.

WINDS AND WAVES LOOK TO RAMP UP WEDNESDAY NIGHT INTO THURSDAY AS
STRONG SOUTHERLY WINDS DEVELOP. THURSDAY COULD BE A BEACH
HAZARDS/SMALL CRAFT ADVISORY DAY WITH THE POTENTIAL FOR WARM BEACH
WEATHER AND LARGE WAVES/DANGEROUS CURRENTS. IT WOULD BE ANOTHER
SOUTH FLOW EVENT WHERE WIND DIRECTION IS CRITICAL. THERE IS A BIG
DIFFERENCE IN IMPACTS FROM A 180 DEGREE WIND AND A WIND DIRECTION
FROM 210 DEGREES.


&&

.HYDROLOGY...
ISSUED AT 1240 PM EDT TUE SEP 2 2014

RIVERS ARE RUNNING A LITTLE ABOVE NORMAL... BUT ARE STILL FAR BELOW
BANK FULL. EXPECTING PRECIPITATION TOTALS MOSTLY UNDER A HALF INCH
THROUGH THE REMAINDER OF THE WORK WEEK. THIS SHOULD LEAD TO SMALL
RISES ON AREA RIVERS WITH PEAK LEVELS WELL BELOW BANK FULL.

&&

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

$$

UPDATE...COBB
SYNOPSIS...DUKE
SHORT TERM...DUKE
LONG TERM...LAURENS
AVIATION...93
HYDROLOGY...63
MARINE...DUKE





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