Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 270123
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
923 PM EDT WED AUG 26 2015

LATEST UPDATE...
MARINE

.SYNOPSIS...
ISSUED AT 328 PM EDT WED AUG 26 2015

THE STORM THAT HAS BROUGHT US CLOUDS AND UNSEASONABLY COOL
TEMPERATURES IS MOVING OUT OF THE AREA TONIGHT AND WILL BE
FOLLOWED BY A LARGE SURFACE HIGH PRESSURE AREA FOR THURSDAY
INTO FRIDAY. THAT IS EXPECTED TO BRING ABUNDANT SUNSHINE BOTH
DAYS WITH WARMER AFTERNOON TEMPERATURES. A STORM SYSTEM MOVING
THROUGH THE AREA SATURDAY MAY BRING SOME SHOWER AND A FEW
THUNDERSTORMS. MUCH WARMER WEATHER IS EXPECTED NEXT WEEK.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY NIGHT)
ISSUED AT 328 PM EDT WED AUG 26 2015

THE BIG QUESTION IS WHEN WILL THE CLOUDS CLEAR? I GENERALLY USE
TWO RULES FOR LOW CLOUDS... FIRST WE NEED TO BE ON THE
ANTICYCLONIC SIDE OF THE UPPER JET AND SECOND WE NEED ANTICYCLONE
FLOW AT LOW LEVELS. BOTH OF THESE OCCUR BETWEEN MIDNIGHT TONIGHT
AND SUNRISE THURSDAY. SO I WENT THAT WAY WITH THE CLOUDS AND AS A
RESULT HAVE LOWS MOSTLY IN THE 50S. IF IT CLEARS EARLIER WE COULD
SEE WIDESPREAD LOWS IN THE 40S.

ONCE THE SYSTEM IS OUT OF THE WAY SHORTWAVE RIDGING AND A LARGE
SURFACE HIGH MOVE OVER THE AREA SO SKIES SHOULD BE MOSTLY SUNNY
THURSDAY AND FRIDAY. THE SYSTEM THAT IMPACTS SOUTHWEST MICHIGAN
SATURDAY SHOULD BRING CLOUDS INTO THE AREA FRIDAY NIGHT. I PUT LOW
CHANCE POPS NORTH BUT I REALLY THINK THE SHOWERS WILL WAIT UNTIL
THE DAY TIME OF SATURDAY.

.LONG TERM...(SATURDAY THROUGH WEDNESDAY)
ISSUED AT 328 PM EDT WED AUG 26 2015

MAIN FOCUS IN THE LONG TERM IS TWO FOLD...THE CHANCES FOR
PRECIPITATION SATURDAY AND SATURDAY NIGHT AND HOW WARM WE GET NEXT
WEEK.

OVERALL...CONFIDENCE IS ON THE LOWER SIDE OF THE SCALE...AS
THE OPERATIONAL GFS AND ECMWF HANDLE THE WAVE EJECTING OUT OF THE
UTAH TODAY DIFFERENTLY. IT IS THIS WAVE THAT IS FORECAST TO BE
MOVING THROUGH THE GREAT LAKES REGION EARLY IN THE WEEKEND. THE
ECMWF IS MORE SHARP WITH THE SHORTWAVE ALOFT AND THEREFORE ITS
SURFACE LOW IS MORE DEVELOPED. THE GFS IS MUCH WEAKER AND FURTHER
SOUTH. BOTH MODELS BRING PRECIPITATION THROUGH THE STATE SATURDAY
AND SATURDAY NIGHT THOUGH...SO MAINTAINED THE CHANCES (30-50 PCT)
FOR SHOWERS AND STORMS IN THE FORECAST. NEIGHBORING OFFICES AGREE IN
THE PRECIP FORECAST...BUT OVERALL MY CONFIDENCE IS LOWER IN REGARD
TO A WEAK SHORTWAVE EJECTING THROUGH THE MEAN RIDGE IN THE WEST.
REMAINDER OF THE FORECAST IS DRY.

AS FOR NEXT WEEK...BOTH THE ECMWF AND THE GFS BUILD AND UPPER LEVEL
RIDGE OVER THE GREAT LAKES. 500MB HEIGHTS ARE SOME OF THE WARMEST OF
THE SUMMER. 500MB HEIGHTS ECLIPSE 590 DM/S OFF BOTH MODELS. 850MB
TEMPS RISE INTO THE UPPER TEENS. HAVE UPPER 80S IN THE FORECAST
EARLY NEXT WEEK. TEMPS COULD REACH 90...BUT HAVE NOT GONE THAT HIGH
YET. I WOULD LIKE TO SEE MORE IN THE WAY OF CONSISTENCY IN HOW THE
SHORTWAVE MOVES INTO THE GREAT LAKES AND HOW IT EXITS/DISSIPATES.
THE GFS AND ECMWF HAVE MUCH DIFFERENT SOLUTIONS IN WHERE THE 500MB
LOW MOVES AFTER SUNDAY. THIS COULD HAVE SOME RAMIFICATIONS ON THE
LOCATION OF THE UPPER RIDGE AND ASSOCIATED CLOUD COVER POSSIBLE IF
THE LOW FOR SOME REASON LINGERS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 655 PM EDT WED AUG 26 2015

THE VFR CLOUDS ALONG WITH SOME PATCHY MVFR WILL BREAK UP LEADING
TO DECREASING CLOUDS THROUGH THE TAF PERIOD. A SMALL RISK FOR FOG
EXISTS LATE TONIGHT AS CROSSOVER TEMPERATURES ARE SOMEWHAT
ELEVATED. NOT CONFIDENT ENOUGH THAT FOG WILL FORM...TO ADD IT TO
THE FORECAST AT THIS TIME.


&&

.MARINE...
ISSUED AT 921 PM EDT WED AUG 26 2015

THE PRESSURE GRADIENT WEAKENS OVERNIGHT. THIS WILL SUPPORT WAVES
CONTINUING TO DECREASE. OVERALL THE WINDS WILL REMAIN UNDER 15
KNOTS RIGHT INTO FRIDAY AS NO MAJOR SYSTEMS WILL BE HEADED OUR
WAY. THIS WILL ACT TO KEEP WAVES GENERALLY 2 FEET OR LESS.

&&

.HYDROLOGY...
ISSUED AT 227 PM EDT WED AUG 26 2015

WITH DRY WEATHER EXPECTED TONIGHT THROUGH FRIDAY AND ONLY LIGHT RAIN
FRIDAY NIGHT INTO SATURDAY... RIVER LEVELS SHOULD REMAIN LOW INTO
NEXT WEEK WITH NO FLOODING CONCERNS.

&&

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

$$

SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...DUKE
AVIATION...MJS
HYDROLOGY...63
MARINE...MJS



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