000
FXUS63 KGRR 220743
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
343 AM EDT WED MAY 22 2013

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

.SYNOPSIS...
ISSUED AT 343 AM EDT WED MAY 22 2013

SOUTHWEST MICHIGAN WILL SEE A WET PERIOD STARTING TODAY AND LASTING
THROUGH MID DAY THURSDAY.  LOW PRESSURE WILL ONLY SLOWLY MOVE
THROUGH THE AREA AND THIS SYSTEM WILL PROVIDE THE PERSISTENT SHOWERS
ALONG WITH A FEW THUNDERSTORMS.  THE RAIN WILL COME TO AN END
THURSDAY AFTERNOON INTO THE EVENING FROM NORTHWEST TO SOUTHEAST.
FRIDAY WILL BE DRY WITH SUNSHINE RETURNING.

TEMPERATURES WILL COOL OFF SIGNIFICANTLY THROUGH THE REST OF THE
WORK WEEK.  AFTER HIGHS MAINLY IN THE LOW AND MID 70S TODAY...IT
WILL ONLY GET INTO THE UPPER 50S TO LOWER 60S FOR THURSDAY AND
FRIDAY.

THE HOLIDAY WEEKEND INTO EARLY NEXT WEEK LOOKS DRY.  TEMPERATURES
WILL BE NEAR NORMAL VALUES...IN THE UPPER 60S TO MID 70S.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 343 AM EDT WED MAY 22 2013

WE WILL BE ENTERING A WET PERIOD AS A BROAD AREA OF LOW PRESSURE...
NOW CENTERED OVER SW WISCONSIN ACROSS THE CWA THIS EVENING.  THE
RAIN SHOULD PERSIST INTO AT THE FIRST HALF OF THURSDAY AS THE
ASSOCIATED COLD FRONT MOVES THROUGH.

DESPITE THE INCREASE IN PCPN...FEEL WE WILL LARGELY MISS OUT ON
THE RISK OF SEVERE WEATHER TODAY.  THE BEST UPPER FORCING FROM THE
RIGHT ENTRANCE REGION OF THE UPPER JET MOVES FROM SOUTHERN IL THIS
MORNING...THROUGH INDIANA THIS AFTERNOON AND INTO OHIO BY EVENING.
IT WILL BE CLOSE ENOUGH TO NOT TOTALLY RULE OUT SEVERE...BUT CHANCES
THIS FAR NORTH LOOK SLIM.  THE BEST INSTABILITY TODAY STAYS EAST OF
A MOP-BTL LINE...WHERE AN ISOLATED SEVERE STORM IS POSSIBLE.

OVERALL HOWEVER WE ARE LARGELY LOOKING AT AN EXPANDING AREA OF
SHOWERS AND EMBEDDED THUNDERSTORMS THAT WILL BRING STEADY RAINS.
THIS IS ALREADY TAKING PLACE EARLY THIS MORNING AROUND THE SOUTHERN
LAKE MICHIGAN REGION.  POCKETS OF PCPN SHOULD GRADUALLY BECOME MORE
WIDESPREAD BY LATE AFTERNOON INTO TONIGHT AS THE DEEPEST MOISTURE
ARRIVES WITH THE LOW COMING IN.  PRECIPITABLE WATER VALUES REMAIN
BETWEEN 1.0 AND 1.5 INCHES THROUGH TODAY AND TONIGHT...SO LOCALIZED
HEAVY RAIN WILL BE LIKELY.  LOCALIZED PONDING OF WATER COULD BE AN
ISSUE.

THE LOW FINALLY PASSES EAST EARLY THURSDAY WITH THE COLD FRONT
COMING THROUGH INTO MID DAY.  THE STEADIEST RAINS SHOULD WIND DOWN
AND RAPID DRYING IS INDICATED FROM NW TO SE THROUGH THE AFTERNOON.
SO EXPECT CLEARING SKIES OVER AT LEAST THE NW HALF OF THE CWA.

MUCH COOLER BEHIND THE LOW FOR THURSDAY AND FRIDAY WITH HIGHS EACH
DAY ONLY UPPER 50S TO LOWER 60S.  COULD BE THE RISK FOR SOME PATCHY
FROST THURSDAY NIGHT OVER THE NORTHERN TWO ROWS OF COUNTIES INLAND
FROM THE LAKE.  WINDS MAY REMAIN HIGH ENOUGH EARLY ON INTO THE NIGHT
THAT TEMPS SHOULD NOT FALL TOO QUICKLY.  SO THERE MAY BE A SMALL
PERIOD...TWO TO FOUR HOURS...WHERE SOME FROST MAY OCCUR.

HIGH PRESSURE MOVES IN BY FRIDAY KEEPING US SUNNY BUT COOL.

.LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY)
ISSUED AT 343 AM EDT WED MAY 22 2013

FOR THE MOST PART IT LOOKS LIKE A COOL AND QUIET WEATHER PATTERN FOR
SOUTHWEST MICHIGAN THROUGH THE MEMORIAL DAY WEEKEND. THE THREAT OF
FROST FOR EARLY SATURDAY MORNING CONTINUES NEAR AND NORTH OF ROUTE
10. THAT FROST IS THANKS TO THE CANADIAN POLAR AIRMASS THE MOVES
INTO THE REGION FRIDAY AND REMAINS IN PLACE THROUGH MEMORIAL DAY.
LIGHT WINDS...COOLER THAN NORMAL TEMPERATURES AND DRY AIR WILL BE
THE IMPACT OF THIS AIRMASS.

THE UPPER AIR PATTERN FEATURES AN OMEGA BLOCK TYPE PATTERN ACROSS
THE UNITED STATES AND CANADA THROUGH THE WEEKEND. SOUTHWEST
MICHIGAN IS ON THE DOWN STREAM SIDE OF THE LARGE UPPER RIDGE. THIS
WILL KEEP US IN PERSISTENT NORTHWEST FLOW AT THE JET STREAM LEVEL.
THAT IN TURN WILL KEEP THE WARM FRONT FROM PUSHING BACK NORTH
INTO OUR AREA THROUGH THIS FORECAST PERIOD.

ANY SHORTWAVES ON THE SOUTHERN STREAM JET WILL STAY SOUTH OF
MICHIGAN THROUGH TUESDAY RESULTING IN MOSTLY CLEAR TO PARTLY CLOUDY
SKIES THROUGH THE PERIOD. A SLOW WARMING TREND IS EXPECTED STARTING
SUNDAY AND CONTINUING THROUGH TUESDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1147 PM EDT TUE MAY 21 2013

SCATTERED SHOWERS AND THUNDERSTORMS WILL MOVE IN FROM THE
SOUTHWEST OVERNIGHT...WITH MVFR CONDITIONS DEVELOPING BY 12Z
WEDNESDAY IN MORE WIDESPREAD SHOWERS AND A FEW THUNDERSTORMS. SOME
ISOLATED IFR IS POSSIBLE IN SOME OF THE HEAVIER RAIN BANDS OR
THUNDERSTORMS. WINDS WILL BE FROM THE SOUTHWEST AOB 10 KNOTS.

&&

.MARINE...
ISSUED AT 343 AM EDT WED MAY 22 2013

A BAGGY LOW WILL PRODUCE LIGHT WINDS TODAY INTO THIS EVENING.
HOWEVER BEHIND THE LOW NORTHERLY WINDS WILL INCREASE BY LATE TONIGHT
INTO THURSDAY.  A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED BY LATE
TONIGHT.  THE ADVISORY WILL PROBABLY NEED TO BE CARRIED INTO EARLY
FRIDAY MORNING UNTIL THE HIGH MOVES IN AND PRODUCES LOWER WAVE
ACTION.

&&

.FIRE WEATHER...
ISSUED AT 343 AM EDT WED MAY 22 2013

MANY AREAS WILL SEE OVER AN INCH OR MORE OF RAIN FROM NOW THROUGH
THURSDAY.  THIS WILL PRODUCING LOWERING FIRE RISK.

&&

.HYDROLOGY...
ISSUED AT 343 AM EDT WED MAY 22 2013

EXPECT AN UP TICK TO THE LARGER RIVER LEVELS WITH THE ENTIRE CWA
EXPECTED TO SEE BETWEEN 0.75 AND 1.75 INCHES OF RAIN THROUGH
THURSDAY.  HOWEVER THE MAIN HYDRO THREAT WILL BE LOCALIZED HEAVY
RAIN WHICH COULD PRODUCED LOCALIZED FLOODING IN LOW LYING AREAS AND
ALSO NEAR SMALL CREEKS AND STREAMS.

&&

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

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...WDM
AVIATION...OSTUNO
FIRE WEATHER...JK
HYDROLOGY...JK
MARINE...JK