Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 281912
AFDGRR

AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI
312 PM EDT THU MAY 28 2015

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

.SYNOPSIS...
ISSUED AT 312 PM EDT THU MAY 28 2015

AN EASTWARD MOVING COLD FRONT WILL GENERATE SHOWERS AND
THUNDERSTORMS FRIDAY INTO SATURDAY. COLDER AIR BEHIND THE FRONT MAY
RESULT IN SOME FROST ACROSS PORTIONS OF CENTRAL LOWER MICHIGAN
SUNDAY NIGHT. HIGH TEMPERATURES WILL ONLY REACH THE 60S SATURDAY AND
SUNDAY BEFORE WARMER AIR RETURNS EARLY NEXT WEEK. THE THUNDERSTORMS
THAT DEVELOP FRIDAY AND SATURDAY WILL HAVE THE POTENTIAL FOR
GENERATING HEAVY RAINFALL.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT)
ISSUED AT 312 PM EDT THU MAY 28 2015

FORECAST CONCERNS DEAL WITH THE CONVECTIVE POTENTIAL LATE TONIGHT
THROUGH SATURDAY.

CLEAR SKIES WILL GIVE WAY TO SOME HIGH CLOUDS TONIGHT AS A COLD
FRONT MOVES EAST FROM THE PLAINS. FRIDAY MORNING SHOULD BE MOSTLY
DRY. THE UPPER SUPPORT WITH THE FRONT ARE PROGD TO REMAIN ACROSS
IOWA AND WISCONSIN FRIDAY. THAT SUGGESTS TO ME THAT THE DRIER ECMWF
MAY BE A BETTER SOLUTION THAN THE WETTER GFS. SHRA/TSRA SHOULD
INCREASE FRIDAY AFTERNOON AND THEN CONTINUE FRIDAY NIGHT AS THE COLD
FRONT MOVES THROUGH THE CWA. SHORT RANGE MODELS SHOW THE FRONT
MOVING THROUGH THE CWA FRIDAY AFTERNOON. SHEAR VALUES FRIDAY MORNING
NORTH OF MUSKEGON ARE 30+ KTS...HOWEVER INSTABILITY IS LOW. BY THE
TIME THE INSTABILITY INCREASES DURING THE AFTERNOON THE SHEAR
DECREASES A BIT. HOWEVER FORECAST SOUNDINGS SHOW STEEP LAPSE RATES
AROUND 7.5 C/KM NEAR THE FRONT. THERE MAY BE A NARROW WINDOW EARLY
TO MID AFTERNOON ACROSS THE CENTRAL CWA WHERE A FEW OF THE STORMS
COULD BE STRONG. SPC HAS THE ENTIRE CWA IN A MARGINAL RISK FOR
SEVERE STORMS FRIDAY.

PCPN WILL DIMINISH FRIDAY NIGHT AS THE FRONT MOVES THROUGH AND
SATURDAY AND SUNDAY WILL BE CHILLY WITH HIGHS IN THE 60S. ADDED
FROST TO THE GRIDS OVER THE NRN CWA SUNDAY NIGHT AS LOWS WILL FALL
INTO THE 30S UNDER MOSTLY CLEAR SKIES.

.LONG TERM...(SUNDAY THROUGH THURSDAY)
ISSUED AT 312 PM EDT THU MAY 28 2015

FAIRLY QUIET WEATHER IN THE EXTENDED. A COOL SFC HIGH WILL HOLD SWAY
AT THE START WITH FROST FORMATION POSSIBLE ACROSS THE NORTHERN THIRD
OF THE FORECAST AREA SUNDAY NIGHT. THE HIGH WILL MOVES EAST EARLY IN
THE WEEK WITH A MOIST RETURN FLOW SETTING UP BY WEDNESDAY.

SOME SHOWERS AND POSSIBLY THUNDER CAN BE EXPECTED ACROSS THE
SOUTHERN ZONES BY WEDNESDAY AFTERNOON IN AREA OF WEAK ISENTROPIC
ASCENT AND THIS SHOULD EXPAND NORTHWARD ON THURSDAY WITH CONTINUED
MOISTURE RETURN AND SFC BASED INSTABILITY ON THE INCREASE. SEVERE
THREAT WILL BE LIMITED BY VERY WEAK SHEAR WITH ANY THUNDERSTORMS
EXPECTED TO BE SHORT LIVED.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 130 PM EDT THU MAY 28 2015

VFR CONDITIONS ARE EXPECTED THROUGH FRIDAY MORNING. THERE COULD BE
SOME SHALLOW FOG AT AZO AND JXN AGAIN TONIGHT BUT THIS WAS LEFT
OUT OF THE FORECAST FOR NOW. WINDS WILL BE SOUTH OR SOUTHWEST AOB
10 KNOTS THROUGH TONIGHT THEN INCREASE FRIDAY MORNING TO AOA 10
KTS WITH SOME GUSTS TO 20 KNOTS POSSIBLE BY EARLY AFTERNOON.
SHOWERS AND THUNDERSTORMS SHOULD HOLD OFF UNTIL AFTER 18Z.


&&

.MARINE...
ISSUED AT 312 PM EDT THU MAY 28 2015

A WEAK PRESSURE GRADIENT WILL RESULT IN LOW WAVE HEIGHTS TONIGHT.
SOUTH WINDS AHEAD OF THE COLD FRONT WILL RESULT IN WAVES BUILDING TO
1 TO 3 FEET NORTH OF GRAND HAVEN FRIDAY.

&&

.HYDROLOGY...
ISSUED AT 1220 PM EDT THU MAY 28 2015

TOTAL QPF FRIDAY THROUGH SATURDAY WITH THE NEXT ROUND OF SHOWERS
AND THUNDERSTORMS CONTINUES TO TREND DOWNWARD AT AROUND AN INCH
OR LESS. GIVEN THAT BASE FLOWS ARE NEAR NORMAL IN THE GRAND RIVER
BASIN AND BELOW NORMAL IN THE KALAMAZOO BASIN...WE EXPECT MODEST
RISES WITH SOME SITES PERHAPS REACHING BANKFULL BUT NOTHING OF
GREAT SIGNIFICANCE. THE COMING WEEK LOOKS DRY WHICH SHOULD ALLOW
LEVELS TO FALL ONCE AGAIN.

&&

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

$$

SYNOPSIS...04
SHORT TERM...04
LONG TERM...OSTUNO
AVIATION...OSTUNO
HYDROLOGY...TJT
MARINE...04


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