Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 021932
AFDGRR

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

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

.SYNOPSIS...
ISSUED AT 308 PM EDT TUE SEP 2 2014
FAIR WEATHER WILL CONTINUE THROUGH WEDNESDAY WITH WEAK HIGH
PRESSURE IN CONTROL. THUNDERSHOWERS AND A RETURN TO MUGGY WEATHER
WILL FOLLOW ON THURSDAY INTO FRIDAY AS LOW PRESSURE MOVES WEST TO
EAST ACROSS SOUTHERN CANADA. SEASONABLY COOL AND DRY WEATHER THEN
FOLLOWS AS A CANADIAN HIGH PRESSURE SYSTEMS MOVES OVERHEAD FOR THE
WEKEND.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 308 PM EDT TUE SEP 2 2014

H5-3 SHORTWAVE AXIS NOW MOVING EAST OF THE REGION WITH DRIER AIR
CONTINUING TO FILTER IN AT THE SURFACE...BUT STILL EXPECTING A
FEW ISOLATED SHOWERS WELL NORTH OF I-96 THROUGH 800 PM EDT WITH
CAPE AROUND 250-500 J/KG.

WARM FRONT SUPPORTED BY HEALTHY LOW-LEVEL-JET APPROACH REGION
EARLY THURSDAY WITH THUNDERSTORM THREAT. SO FAR THE
ECMWF...FIM...AND GFS HAVE BEEN PRETTY CONSISTENT WITH MCS
FORMATION OVER NORTHERN WISCONSIN WED NIGHT THAT THEN MOVES EAST
AFFECTING NORTHERN HALF OF LOWER MICHIGAN BY MIDDAY THURSDAY. THIS
LOOKS REASONABLE GIVEN SUPPORTING MID-LEVEL FRONTOGENESIS
ASSOCIATED WITH WARM FRONT.

STRONG STORMS AND LOCALLY HEAVY RAIN WILL BE GOOD POSSIBILITIES
BEGINNING THURSDAY NIGHT AS THE COLD FRONT PUSHES INTO THE
REGION. STORMS WILL BE SUPPORTED BY FRONTAL CONVERGENCE...DEEP
CAPE OF 2000 J/KG...BULK SHEAR OF 30 KTS...AND UPPER DIVERGENCE
WITH MID-LEVEL FRONTOGENESIS. FURTHER...LOCALLY HEAVY RAINFALL
WITH FAIRLY HIGH PERCIPITABLE WATER.

.LONG TERM...(FRIDAY THROUGH TUESDAY)
ISSUED AT 308 PM EDT TUE SEP 2 2014
A COLD FRONT MOVING ACROSS MICHIGAN SHOULD BRING A ROUND OF SHOWERS
AND THUNDERSTORMS TO THE CWA FRIDAY. WE/LL HAVE TO WATCH OUT FOR THE
POTENTIAL FOR SEVERE STORMS FRIDAY LATE MORNING AND AFTERNOON. HIGH
INSTABILITY WITH LI/S NEAR -7 AND MUCAPE 3K+ J/KG COUPLED WITH
30-35KT SHEAR VALUES SHOULD LEAD TO SOME CELL ORGANIZATION. IT/S NOT
A SLAM DUNK THOUGH. THE LLJ IS MOVING AWAY FROM THE CWA BY MID
MORNING FRIDAY WHICH MAY LIMIT THE SEVERE POTENTIAL. FAVORABLE UPPER
JET DYNAMICS THOUGH MAY MITIGATE THE DEPARTING LLJ HOWEVER. IF MODEL
TIMING IS ACCURATE...AND SO FAR BOTH THE GFS AND ECMWF ARE IN PRETTY
GOOD AGREEMENT...THE PCPN SHOULD END BY FRIDAY EVENING. AFTER
THAT...COOLER AND DRIER AIR WILL MOVE INTO THE GREAT LAKES AND THE
WEEKEND LOOKS VERY PLEASANT WITH HIGHS IN THE LOWER 70S AND LOWER
HUMIDITY. AS THE HIGH MOVES EAST TUESDAY A WARM FRONT WILL MOVE
TOWARD THE CWA AND THE CHANCES FOR SHOWERS AND STORMS WILL INCREASE.

&&

.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 308 PM EDT TUE SEP 2 2014

NO SIGNIFICANT WEATHER THROUGH WEDNESDAY. EXPECT SMALL CRAFT /
BEACH HAZARD WILL BE NEEDED ON THU AS 15-25 KT SOUTH FLOW
DEVELOPING AS WARM FRONT PUSHES NORTHEAST ACROSS THE LAKE EARLY
THURSDAY. WAVES SHOULD REACH 3 TO 6 FEET WITH A RATHER CHOPPY
PERIOD FRIDAY AS WINDS SHIFT TO WEST AND THEN NORTHWEST BEHIND
COLD FRONT.

&&

.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.
&&

$$

SYNOPSIS...COBB
SHORT TERM...COBB
LONG TERM...93
AVIATION...93
HYDROLOGY...63
MARINE...COBB





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