Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 200127
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
927 PM EDT FRI SEP 19 2014

LATEST UPDATE...
UPDATE

.SYNOPSIS...
ISSUED AT 320 PM EDT FRI SEP 19 2014

A COLD FRONT MOVING THROUGH THE UPPER MIDWEST WILL GENERATE
THUNDERSTORMS SATURDAY...SOME OF WHICH MAY BE STRONG TO SEVERE.
SHOWERS WILL LINGER THROUGH SATURDAY NIGHT BEFORE HIGH PRESSURE
BUILDS SOUTH AND SKIES CLEAR. COOLER TEMPERATURES ARE EXPECTED
SUNDAY AND MONDAY BEFORE A WARMING TREND BEGINS MID WEEK.

&&

.UPDATE...
ISSUED AT 927 PM EDT FRI SEP 19 2014

STILL KEEPING AN EYE ON THE POTENTIAL FOR STRONG STORMS AND MAYBE
SOME SEVERE WEATHER TOMORROW AFTERNOON. LITTLE CHANGE TO THE
FORECAST THIS EVENING.

FIRST ROUND OF SHOWERS SHOULD BEGIN TO MOVE ON SHORE AROUND 6AM.
MODELS ARE MIXED IN HOW FAR SOUTH THIS FIRST BATCH OF SHOWERS WILL
MAKE IT. RECENT TRENDS IN HIGH RESOLUTION MODELS SHOW MAINLY
MUSKEGON TO CLARE AND NORTH WITH THE FIRST BATCH OF SHOWERS...WITH
THE REMAINDER OF LOWER MICHIGAN MISSING OUT ON THE EARLY BATCH.
SATELLITE TRENDS SEEM TO SUPPORT THIS NORTHERN TRACK AND MADE A
FEW ADJUSTMENTS TO PRECIPITATION CHANCES OVERNIGHT AND EARLY
SATURDAY MORNING TO ACCOUNT FOR THIS SHIFT FROM WHAT WAS EXPECTED
EARLIER. COULD STILL SEE SOME LIGHT RAIN ACROSS SOUTHERN MICHIGAN
MID MORNING FROM THIS FIRST ROUND...BUT FOR THE MOST PART THE BEST
SHOT AT STORMS FOR GRAND RAPIDS TO LANSING AND SOUTH SHOULD REMAIN
IN THE AFTERNOON TO EVENING.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 320 PM EDT FRI SEP 19 2014

FORECAST CONCERNS DEAL WITH CONVECTIVE TRENDS SATURDAY.

A COLD FRONT CURRENTLY MOVING THROUGH NORTH DAKOTA WILL MOVE INTO
LOWER MICHIGAN SATURDAY. SOME LIGHT SHOWERS ARE MOVING ACROSS NC
WISCONSIN ATTM IN CONJUNCTION WITH A PRE FRONTAL TROUGH AND WE/LL
PROBABLY SEE SOMETHING SIMILAR LATE TONIGHT/EARLY SATURDAY WHEN THE
TROUGH MOVES THROUGH. THE SIGNIFICANT WEATHER WILL PROBABLY HOLD OFF
UNTIL AFTER 1 PM OR SO WHEN THE COLD FRONT GETS CLOSER AND...MORE
IMPORTANTLY...A SHORT WAVE APPROACHES. MODELS ARE SHOWING SOME GOOD
DYNAMICS SHOWING UP DURING THE AFTERNOON. WHILE ELEVATED INSTABILITY
IS EVIDENT DURING THE MORNING...SFC BASED INSTABILITY DEVELOPS
DURING THE AFTERNOON. STRONG SHEAR NEAR 55 KTS IS PROGD ALONG WITH
SBCAPE NEAR 1000 J/KG. A 60-70KT MID LEVEL JET PUNCHES DOWN FROM THE
NW LATE IN THE DAY SUGGESTING THAT WIND WILL BE THE MAIN THREAT IN
THE FORM OF BOWING LINE SEGMENTS. GIVEN THE STRONG SHEAR THOUGH HAIL
WOULD BE A CLOSE SECOND.

A WAVE WILL DEVELOP ON THE FRONT IN RESPONSE TO A STRONG SECONDARY
SHORT WAVE DROPPING SOUTH FROM WESTERN ONTARIO. THIS WAVE WILL CAUSE
THE CAUSE THE COLD FRONT TO SLOW DOWN A BIT. ALTHOUGH INSTABILITY
DECREASES A BIT SATURDAY NIGHT...SHEAR VALUES INCREASE TO 75KTS...SO
THE SVR THREAT WILL LINGER UNTIL AROUND 6AM SUNDAY WITH THE FRONT
FINALLY MOVES THROUGH.

SKIES SHOULD CLEAR SUNDAY INTO SUNDAY NIGHT SETTING THE STAGE FOR
POTENTIAL FROST OVER THE NRN CWA AS LOWS FALL INTO THE 30S.

.LONG TERM...(MONDAY THROUGH FRIDAY)
ISSUED AT 320 PM EDT FRI SEP 19 2014

QUIET WEATHER EXPECTED IN THE EXTENDED PERIOD. THE WEEK SHOULD BE
DRY AS THE GREAT LAKES REGION IS DOMINATED BY STRONG RIDGING AT THE
SFC AND ALOFT. AFTER A COOL START TO THE WEEK...TEMPERATURES WILL
MODERATE AS HEIGHTS RISE. EXPECT WARMER DAYS AND LESS COOL NIGHTS
FOR THE LATTER HALF OF THE WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 731 PM EDT FRI SEP 19 2014

CHALLENGING SET OF TERMINAL FORECASTS THIS EVENING WITH POTENTIAL
FOR MULTIPLE ROUNDS OF SHOWERS AND THUNDERSTORMS...ESPECIALLY
AFTER 06Z. FIRST ROUND SHOULD STAY MOSTLY ACROSS NORTHERN LOWER
MICHIGAN AND HAS A HIGH POTENTIAL TO RESULT IN SOME HAZARDOUS
FLYING CONDITIONS IN MUSKEGON FROM 06Z THROUGH 12Z.

SECOND ROUND OF ACTIVITY WILL DEVELOP AFTER 14Z AND COULD RESULT
IN THUNDERSTORMS IMPACTING ALL TERMINAL FORECAST LOCATIONS ACROSS
SOUTHWEST LOWER MICHIGAN THROUGH THE END OF THIS TERMINAL FORECAST
PERIOD. CONFIDENCE REMAINS MODERATE IN THIS SECOND ROUND OF
ACTIVITY AT THIS TIME BUT ENOUGH CONFIDENCE IS THERE FOR VC AND
PROB30 MENTION OF TSRA.


&&

.MARINE...
ISSUED AT 731 PM EDT FRI SEP 19 2014

WINDS WILL INCREASE OVERNIGHT TONIGHT WITH HAZARDOUS WAVES AND
WINDS EXPECTED THROUGH SATURDAY EVENING. SMALL CRAFT ADVISORY
REMAINS IN EFFECT THROUGH 8PM SATURDAY.


&&

.HYDROLOGY...
ISSUED AT 320 PM EDT FRI SEP 19 2014

BASIN AVERAGE RAINFALL OF ABOUT A HALF INCH SATURDAY INTO EARLY
SUNDAY WILL LEAD TO MODEST RISES ON AREA RIVERS...THOUGH LEVELS
SHOULD REMAIN WELL BELOW BANKFULL. PRIMARY ISSUE IS SHORT DURATION
HEAVY RAIN PARTICULARLY IN THE SOUTHERN CWA WHERE STORMS WILL TEND
TO BE STRONGER AND MORE WIDESPREAD. LOCAL URBAN AND POOR DRAINAGE
FLOOD CONCERNS WILL EXIST WHERE HEAVY RAINFALL PERSISTS...BUT
GENERAL PROGRESSIVE NATURE OF THE CONVECTION WILL KEEP THE FLASH
FLOOD THREAT LOW. DRY WEATHER IS EXPECTED FOR MUCH OF NEXT WEEK.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 8 PM EDT SATURDAY FOR LMZ847>849.

     SMALL CRAFT ADVISORY UNTIL 8 PM EDT SATURDAY FOR LMZ844>846.

&&

$$

UPDATE...MACZKO
SYNOPSIS...93
SHORT TERM...93
LONG TERM...OSTUNO
AVIATION...MACZKO
HYDROLOGY...CAS
MARINE...MACZKO






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