Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 290545
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
145 AM EDT FRI AUG 29 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 328 PM EDT THU AUG 28 2014

A WARM FRONT WILL MOVE IN LATE TONIGHT BRINGING SHOWERS AND
THUNDERSTORMS FRIDAY AND SATURDAY. SUNDAY SHOULD BE RELATIVELY
QUIET BEFORE MORE SHOWERS AND THUNDERSTORMS ROLL THROUGH ON
MONDAY. SEVERE WEATHER APPEARS POSSIBLE WITH THE STORMS ON MONDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT)
ISSUED AT 328 PM EDT THU AUG 28 2014

LOOKS LIKE THE BULK OF THE RAIN WILL FALL ACROSS NORTHWEST LOWER
MICHIGAN ON FRIDAY IN AREA OF BEST ISENTROPIC ASCENT NORTH OF A
SFC WARM FRONT. INSTABILITY AND SHEAR ARE LIMITED SO SEVERE THREAT
APPEARS LOW. ONLY SCATTERED RAIN AND THUNDER EXPECTED ACROSS THE
SOUTH UNTIL SATURDAY...WHEN SFC LOW AND TRAILING COLD FRONT MOVES
INTO LOWER MICHIGAN BRINGING MORE WIDESPREAD SHOWERS.

.LONG TERM...(SUNDAY THROUGH THURSDAY)
ISSUED AT 317 PM EDT THU AUG 28 2014

THE MODELS ARE IN GOOD AGREEMENT THROUGH MONDAY NIGHT...THEN BEGIN
TO DIVERGE.

A COLD FRONT WILL BE MAKING IT/S WAY THROUGH THE STATE ON SUNDAY.
MOST OF THE DYNAMICS ARE WELL AHEAD OF THE FRONT...SO WE SHOULD SEE
A MOSTLY DRY DAY AND I TRIMMED BACK ON THE POPS.  HOWEVER I DID
LEAVE 20 POPS ACROSS THE NORTHERN HALF OF THE CWA FOR AN ISOLATED
SHOWER/STORM.

THE NEXT SYSTEM ALREADY ARRIVES INTO LABOR DAY WITH A RATHER
PROGRESSIVE ZONAL FLOW.  ALL MODELS AGREE THAT ANOTHER COLD FRONT
MOVES INTO THE WESTERN GREAT LAKES BY MONDAY AFTERNOON.  THE MORNING
MAY REMAIN DRY...BUT WE SHOULD HAVE INCREASING CHANCES OF
SHOWERS/STORMS INTO THE AFTERNOON.  THE THREAT OF PCPN SHOULD END
MONDAY NIGHT...OR INTO TUESDAY SE...AS THE FRONT EXITS.

POOR AGREEMENT IN THE MODELS INTO MID WEEK WITH THE ECMWF BUILDING A
RIDGE OVER THE EASTERN U.S. AND WARMING THE GREAT LAKES
SIGNIFICANTLY.  MEANWHILE THE GFS AND IT/S ENSEMBLES BRING ANOTHER
COLD FRONT THROUGH ON WEDNESDAY...KEEPING US COOLER AND WETTER.  I
SIDED WITH THE GFS THAT HAS SHOWN BETTER CONSISTENCY.  HOWEVER THE
FRONT APPEARS FAIRLY DRY...SO WILL KEEP ANY POPS LOW AND KEEP TEMPS
NEAR NORMAL.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 145 AM EDT FRI AUG 29 2014

TWO POTENTIAL PERIODS OF PRECIPITATION ARE THE MAIN ITEMS OF
INTEREST FOR AVIATION INTERESTS OVER THE NEXT 24 HOURS. MID/HIGH
CLOUDS ARE STREAMING IN OUT AHEAD OF THE SHOWERS AND STORMS THAT
HAVE BEEN ONGOING ACROSS WI AND IL LAST EVENING AND EARLY THIS
MORNING. WE WILL SEE THE THREAT FOR SHOWERS INCREASE MAINLY NORTH
OF KGRR BY 12Z AS A WAVE MOVES INTO THAT AREA. THIS WILL KEEP THE
THREAT IN THROUGH ABOUT 16Z OR SO.

THE NEXT THREAT WILL THEN BEGIN AFTER 00Z SAT AS ANOTHER WAVE OF
LOW PRESSURE WILL APPROACH THE AREA. SHOWERS AND A FEW STORMS WILL
BECOME POSSIBLE...ALTHOUGH THE MUCH BETTER THREAT WILL COME AFTER
06Z SAT. CONDITIONS SHOULD BE MAINLY VFR EXCEPT UNDER SOME HEAVIER
SHOWERS FURTHER NORTH.

&&

.MARINE...
ISSUED AT 328 PM EDT THU AUG 28 2014

WINDS WILL PICK UP TONIGHT INTO FRIDAY. WAVES WILL BUILD TO NEAR 4
FOOT NORTH OF WHITEHALL...WHERE SHOWERS AND THUNDERSTORMS ARE
EXPECTED FRIDAY THROUGH SATURDAY. STRONG TO SEVERE STORMS ARE
POSSIBLE ON MONDAY.


&&

.HYDROLOGY...
ISSUED AT 328 PM EDT THU AUG 28 2014

THE HEAVY RAIN THREAT APPEARS TO BE LIMITED TO THE MUSKEGON AND
PERE MARQUETTE BASINS AS AN INCH OF QPF CAN BE EXPECTED THERE BY
SUNDAY MORNING...WHICH WOULD RESULT IN RISES BY EARLY NEXT WEEK.
MUCH LESS RAIN IS EXPECTED IN THE GRAND AND KALAMAZOO RIVER
BASINS.

&&

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

$$

SYNOPSIS...OSTUNO
SHORT TERM...OSTUNO
LONG TERM...JK
AVIATION...NJJ
HYDROLOGY...OSTUNO
MARINE...OSTUNO





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