Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 181906
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
306 PM EDT THU SEP 18 2014

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

.SYNOPSIS...
ISSUED AT 306 PM EDT THU SEP 18 2014

QUIET AND PLEASANT WEATHER WILL CONTINUE THROUGH FRIDAY.  IT WILL BE
A SLIGHTLY WARMER WITH HIGHS ON FRIDAY IN THE MID 60S TO LOWER 70S
WITH A MIX OF CLOUDS AND SUNSHINE.  THE RISK OF SHOWERS AND
THUNDERSTORMS RETURN LATE FRIDAY NIGHT AND ARE EXPECTED TO LINGER
INTO SATURDAY AND SATURDAY NIGHT.  A FEW OF THESE STORMS COULD BE
STRONG TO SEVERE SATURDAY AFTERNOON AND EVENING.  TEMPERATURES ON
SATURDAY WILL RANGE FROM THE UPPER 60S OVER CENTRAL LOWER TO AROUND
80 OVER FAR SOUTHERN LOWER.

MUCH OF NEXT WEEK APPEARS TO BE DRY.  TEMPERATURES ARE EXPECTED TO
BE NEAR NORMAL WITH HIGHS IN THE MID 60S TO LOWER 70S AND LOWS IN
THE UPPER 40S TO AROUND 50.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT)
ISSUED AT 306 PM EDT THU SEP 18 2014

A COUPLE CONCERNS PERSIST IN THE SHORT TERM...THE POTENTIAL FOR
FROST TONIGHT...AND THE POTENTIAL FOR SEVERE STORMS SATURDAY.

THE FROST POTENTIAL SEEMS REDUCED TONIGHT AS THE LOW AND MID LEVELS
BEHIND A DIEING COLD FRONT REMAIN MOIST.  CLOUD COVER SHOULD HELP
KEEP THE AREA A BIT WARMER OVERNIGHT SO RAISE MINS SLIGHTLY AND WILL
ONLY MENTION PATCHY FROST OVER THE INTERIOR NORTH LATE TONIGHT.

ATTENTION THEN TURNS TO THE COLD FRONT THAT IS PROGGED TO REACH THE
CWA SATURDAY EVENING.  HOWEVER STILL QUITE A BIT OF DIFFERENCES
SHOWING UP IN THE MODELS WITH THE TIMING OF THE FRONT AND JUST HOW
UNSTABLE WE BECOME.  WITH A QUICKER FRONT...AS THE GFS SHOWS...WE
WOULD CLOUD OVER WITH SHOWERS SPREADING IN THROUGH SATURDAY MORNING.
THIS WOULD NOT ALLOW FOR MUCH INSTABILITY.  THE ECMWF AND NAM BOTH
SHOW A SLOWER FRONT...ALLOWING FOR MORE INSTABILITY AND THE BETTER
POTENTIAL FOR SEVERE STORMS.  AS LONG AS WE ARE ABLE TO BECOME
UNSTABLE THE 0-6KM BULK SHEAR VALUES OF 35-40 KTS SUPPORT ORGANIZED
CONVECTION.  WIND FIELDS SHOULD BE IN THE 40-50 KTS RANGE FROM THE
MID LEVELS DOWN TO ABOUT 2K FT SUGGESTING A WIND THREAT WITH ANY
STRONGER STORM.  AT THIS POINT I AM LEANING TOWARD A BETTER CHANCE
OF SEVERE WITH THE MOST LIKELY WINDOW OCCURRING BETWEEN 20Z SAT AND
02Z SUN.  DAMAGING LINE SEGMENTS SHOULD BE THE MODE...BUT SOME
SEVERE HAIL COULD BE POSSIBLE TOO.  SHOWERS AND STORMS WILL
GRADUALLY DIMINISH IN INTENSITY AND COVERAGE AFTER SATURDAY EVENING.

UNTIL THEN FRIDAY APPEARS TO BE A VERY NICE DAY. SOME CLOUDS MAY
LINGER THROUGH THE MORNING...BUT THEN EXPECTING A MOSTLY SUNNY
AFTERNOON...BEFORE CLOUDS RETURN AGAIN TOWARD MIDNIGHT FRIDAY
NIGHT.  SOUTHERLY RETURN FLOW WILL PUSH TEMPS TOWARD NORMAL VALUES
FOR THE FIRST TIME IN OVER A WEEK.  TOUGH SATURDAY MAX TEMP FORECAST
DUE TO TIMING ISSUES STATED ABOVE.  HAVE UPPER 60S OVER THE NW WHERE
THE SHOWERS ARRIVE FIRST...WHILE SOME AREAS IN THE SOUTHERN CWA MAY
HIT 80 IF THERE IS A DELAY IN THE PCPN THERE.

.LONG TERM...(SUNDAY THROUGH THURSDAY)
ISSUED AT 306 PM EDT THU SEP 18 2014

QUIET WEATHER EXPECTED IN THE EXTENDED PERIOD. THERE COULD BE A FEW
SHOWERS ON SUNDAY AS SHARP UPPER TROUGH AXIS MOVES THROUGH ALTHOUGH
MOISTURE IS LIMITED. THE REST OF THE WEEK SHOULD BE DRY BUT WE WILL
HAVE TO WATCH MONDAY NIGHT AS ANOTHER NORTHERN STREAM SHORTWAVE
TROUGH MOVING THROUGH COULD BRING SOME SHOWERS TO NORTHERN ZONES. AT
THIS POINT IT APPEARS ANY SHOWERS WILL REMAIN NORTH OF THE FORECAST
AREA. AFTER A COOL START TO THE WEEK...TEMPERATURES WILL MODERATE AS
HEIGHTS RISE WITH UPPER RIDGING BY THE END OF THE PERIOD.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 156 PM EDT THU SEP 18 2014

MVFR CONDITIONS WILL BE ACROSS CENTRAL LOWER MICHIGAN THIS
AFTERNOON WITH CEILINGS AROUND 2500 FEET AGL. THE CLOUDS WILL
DECREASE LATER THIS AFTERNOON AND EVENING AS DRIER AIR MIXES IN.
SOME LIGHT FOG IS POSSIBLE ONCE AGAIN LATE TONIGHT. WINDS WILL BE
GENERALLY FROM THE EAST OR NORTHEAST BLO 10 KNOTS.

&&

.MARINE...
ISSUED AT 306 PM EDT THU SEP 18 2014

SOUTHERLY WINDS WILL BE INCREASING ON FRIDAY.  WE MAY NEED A SMALL
CRAFT ADVISORY NORTH OF GRAND HAVEN BY AFTERNOON DUE TO THE LONG
FETCH.  THESE WINDS PERSIST INTO FRIDAY NIGHT AND HIGHER WAVES
SHOULD BUILD OVER THE ENTIRE NEARSHORE WATERS.  IT WILL LIKELY STAY
ROUGH UNTIL SATURDAY EVENING WHEN A COLD FRONT PUSHES THROUGH.  THE
WINDS LIGHTEN UP SATURDAY NIGHT ALONG WITH SHIFTING TO THE NW.

&&

.HYDROLOGY...
ISSUED AT 306 PM EDT THU SEP 18 2014

PCPN LATE FRIDAY NIGHT INTO EARLY SATURDAY NIGHT WILL BE CONVECTIVE
IN NATURE...SO RAINFALL AMOUNTS WILL VARY GREATLY.  OVERALL
EXPECTING MOST AREAS WILL SEE A QUARTER TO HALF INCH OF RAIN.
HOWEVER PRECIPITABLE WATER VALUES PEAK NEAR TWO INCHES SATURDAY
EVENING...SO THERE IS POTENTIAL FOR LOCALIZED HEAVY RAIN WHICH COULD
LEAD TO SOME URBAN AND POOR DRAINAGE ISSUES.

&&

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

$$

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








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