Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 101131
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
731 AM EDT THU JUL 10 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 327 AM EDT THU JUL 10 2014

IT WILL REMAIN PLEASANT TODAY AND FRIDAY WITH SUNSHINE AND DAYTIME
TEMPERATURES IN THE 70S.  HOWEVER SHOWERS AND A FEW THUNDERSTORMS
WILL BE MOVING IN LATE FRIDAY NIGHT AND CONTINUE INTO SATURDAY.

ADDITIONAL CHANCES FOR RAIN WILL CONTINUE THROUGH MONDAY NIGHT...
THEN WE SHOULD DRY OUT INTO THE MIDDLE OF NEXT WEEK.  DAYTIME
TEMPERATURES SHOULD BE AROUND 80 SUNDAY AND MONDAY...BUT THEN COOL
TO AROUND 70 TUESDAY AND WEDNESDAY.

&&

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 327 AM EDT THU JUL 10 2014

LITTLE FORECAST CONCERNS FOR THE NEXT 36 HOURS.  HIGH PRESSURE WAS
CENTERED OVER LAKE MICHIGAN EARLY THIS MORNING AND IT WILL ONLY
SLOWLY MARCH TOWARD LAKE ONTARIO BY LATE FRIDAY.  TEMPS SHOULD BE A
COUPLE OF DEGREES WARMER EACH DAY...MOSTLY MID 70S TODAY...THEN
UPPER 70S TO AROUND 80 ON FRIDAY.

LATE FRIDAY NIGHT THROUGH SATURDAY IS LOOKING INCREASINGLY WET.  BY
THEN THE HIGH WILL BE OFF TO OUR EAST AND A COLD FRONT WILL ADVANCE
FROM THE NORTHWEST.  LATEST MODEL TRENDS SHOWS THIS FRONT CROSSING
THE CWA FROM NW TO SE SATURDAY AFTERNOON.  THE FRONT HAS GOOD UPPER
LEVEL SUPPORT TOO WITH A LOW LEVEL JET COMING IN AFTER MIDNIGHT
FRIDAY NIGHT...LINGERING INTO SATURDAY MORNING.  THEN AN
ANTICYCLONIC UPPER JET SHOULD PRODUCE UPPER DIVERGENCE OVER SOUTHERN
LOWER THROUGH MUCH OF SATURDAY LEADING TO PERSISTENT SHOWERS AND
SOME STORMS.  INSTABILITY REMAINS FAIRLY WEAK SO NOT ANTICIPATING
ANY SEVERE STORMS...BUT RATHER POCKETS OF HEAVY RAIN LOOKS MORE
LIKELY...ESPECIALLY SOUTH OF I-96.  HAVE KEEP POPS SOMEWHAT LOW FOR
NOW DUE TO TIMING ISSUES AND POOR AGREEMENT AMONGST SURROUNDING
OFFICES.  BUT THE TREND IS WETTER AND IF THIS HOLDS...POPS WILL NEED
TO BE INCREASED SUBSTANTIALLY.

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 330 AM EDT THU JUL 10 2014

OUR PRIMARY CONCERNS ARE THE CONVECTIVE THREAT INTO MONDAY THEN IT
GETS UNUSUALLY COLD FOR THIS TIME OF YEAR BY TUESDAY.

WE CONTINUE TO WATCH AN UNUSUALLY STRONG UPPER LEVEL STORM SYSTEM
MOVING SOUTH FROM THE CANADIAN ARCTIC INTO THE GREAT LAKES. ACTUALLY
THIS SYSTEM IS A MERGER OF A PACIFIC SYSTEM THAT HAS ALREADY MOVED
INLAND OVER NORTHERN BRITISH COLUMBIA AND SYSTEM MOVING SOUTH FROM
THE CANADIAN ARCTIC. THE SYSTEMS CONSOLIDATE IN THE SATURDAY TIME
FRAME AND CONTINUE TO MOVE SOUTHEAST INTO THE GREAT LAKES BY
TUESDAY. THE MODELS ARE NOW IN GOOD AGREEMENT ON THIS EVOLUTION.

BOTH THE 500 HEIGHTS AND THE 850 TEMPERATURES TUESDAY MORNING ARE
AROUND 3 STANDARD DEVIATIONS FROM NORMAL. THIS IS SIGNIFICANT
ANOMALY FOR THIS TIME OF YEAR... 850 TEMPS FALLING TO NEAR 5C. IT
ASSURES OF UNUSUALLY COOL WEATHER FOR BOTH TUESDAY AND WEDNESDAY.

THE ECMWF HAS BEEN MOST CONSISTENT WITH THE EVOLUTION OF THIS SYSTEM
AND GIVEN THE STRAIGHT OF THE FALLING UPPER LEVEL HEIGHTS SATURDAY
INTO SUNDAY...AND THE PROXIMITY OF THE POLAR JET TO LOWER MICHIGAN
HAVING THE LOW LEVEL JET AIMED AT SOUTHWEST LOWER MICHIGAN AS THE
ECMWF SHOWS MAKES MORE SENSE TO ME THAN WHAT THE GFS SEEMS TO WANT
TO DO. IN ANY EVENT... AT UPPER LEVELS BOTH MODELS SHOW SOUTHWEST
MICHIGAN IN THE JET ENTRANCE REGION SUNDAY SO I HAVE TO BELIEVE WITH
THE DIFLUENT 1000/500 THICKNESS PATTERN... PRECIPITABLE WATER
VALUES NEAR 2 INCHES (MORE THAN DOUBLE NORMAL) THERE WOULD BE A
SIGNIFICANT HEAVY RAIN THREAT AS WELL AS A STRONG THUNDERSTORM
THREAT. I CONTINUED THE HIGH CHANCE POPS FOR SATURDAY NIGHT AND
SUNDAY BUT AS WE GET CLOSER IN TIME I WOULD HAVE TO BELIEVE WE WILL
SEE THE POP INCREASE FOR THIS TIME PERIOD.

A STRONG UPPER LEVEL TROUGH MOVES THROUGH THE AREA MONDAY INTO
TUESDAY. I BELIEVE IN TIME WE WILL SEE THE POP INCREASE
SIGNIFICANTLY IN THIS TIME FRAME TOO. THE THUNDERSTORM THREAT WILL
CONTINUE MONDAY AS THE STRONG COLD FRONT MOVES THROUGH THE AREA.

TUESDAY WE WILL BE DEEP INTO THE COLD AIR VIA THE CLOSED UPPER LOW.
THIS SHOULD LEAD TO DAY TIME CONVECTION AND A POSSIBLE HAIL THREAT.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 731 AM EDT THU JUL 10 2014

VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH TONIGHT. WINDS WILL
BE LIGHT AND VARIABLE EXCEPT AT MUSKEGON WERE A LAKE BREEZE WILL
KEEP THE WINDS FROM THE WEST BETWEEN 5 AND 10 KNOTS.


&&

.MARINE...
ISSUED AT 327 AM EDT THU JUL 10 2014

NICE CONDITIONS EXPECTED ON THE LAKE WITH HIGH PRESSURE OVER THE
AREA THROUGH FRIDAY NIGHT.  HOWEVER SOUTH WINDS WILL INCREASE BY
SATURDAY AND KICK UP WAVES A BIT.  BELIEVE WE WILL STAY BELOW
SCA...BUT SOME 2-4 FOOT WAVES WILL BE POSSIBLE...ESPECIALLY NORTH OF
GRAND HAVEN.  THERE WILL ALSO BE THE RISK OF THUNDERSTORMS LATE
FRIDAY NIGHT INTO SATURDAY.


&&

.HYDROLOGY...
ISSUED AT 328 PM EDT WED JUL 9 2014

NO SIGNIFICANT CHANGES TO THE RIVER FORECASTS. IONIA SHOULD CREST
TONIGHT AND THE MAPLE RIVER AT MAPLE RAPIDS IS NEAR CREST RIGHT NOW.
DRY CONDITIONS OVER THE NEXT COUPLE DAYS SHOULD ALLOW THE OVERALL
SUBSIDING TRENDS TO CONTINUE. SHOWERS AND THUNDERSTORMS EXPECTED
THIS WEEKEND SHOULD RESULT IN AREAL PRECIPITATION AMOUNTS OF LESS
THAN HALF OF AN INCH...WHICH SHOULD HAVE LITTLE IMPACT ON AREA
RIVERS.

&&

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

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...WDM
AVIATION...WDM
HYDROLOGY...TJT
MARINE...JK






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