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000
FXUS63 KGRR 210352
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1152 PM EDT MON MAY 20 2013

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 238 PM EDT MON MAY 20 2013
THUNDERSTORMS AT TIMES THIS AFTERNOON THROUGH WEDNESDAY EVENING WITH
SOME SEVERE WEATHER POSSIBLE. COOLER TEMPERATURES EXPECTED THURSDAY
THROUGH MUCH OF THE HOLIDAY WEEKEND...WITH OVERNIGHT LOWS ON THE
WEEKEND POSSIBLY DROPPING INTO THE UPPER 30S.

&&

.UPDATE...
ISSUED AT 1017 PM EDT MON MAY 20 2013

ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS WERE MOVING ACROSS IL
THIS EVENING AND WILL BE HEADING INTO SW MI OVERNIGHT. THIS
COMPLEX WAS LARGELY BEING DRIVEN BY THE RIGHT ENTRANCE REGION OF
THE UPPER JET. THIS FORCING MOVES INTO SW MI AFTER MIDNIGHT...
ALTHOUGH THE PRIME FORCING REMAINS OVER WISCONSIN THROUGH 12Z.
LIKELY POPS ARE WARRANTED ACROSS MUCH OF THE CWA...HOWEVER I DID
LOWER POPS IN THE SE CWA...THE AREA FURTHEST REMOVED FROM THE BEST
FORCING.

ISOLATED SEVERE STORMS CAN NOT BE RULED OUT OVERNIGHT ACROSS THE
ENTIRE CWA. MUCAPE VALUES REMAIN AT 1-2K THIS EVENING. THE
COMBINATION OF INSTABILITY AND FORCING TEAMS UP BEST ACROSS AREAS
SOUTH OF I-96.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 238 PM EDT MON MAY 20 2013

THUNDERSTORM WATCH IN EFFECT THROUGH 8PM. STORMS SHOULD CONTINUE TO
DEVELOP MAINLY ALONG A LINE OF MID LEVEL MOISTURE THAT IS MOVING
INTO MICHIGAN FROM THE WEST/SOUTHWEST. LARGE HAIL APPEARS TO BE THE
MAIN THREAT SO FAR FROM ANY STORMS...ALONG WITH HEAVY RAINFALL.
WOULD EXPECT THOSE SAME THREATS THIS AFTERNOON...ALONG WITH SOME
DAMAGING WIND POTENTIAL AS WELL. FOCUS THIS AFTERNOON SEEMS TO BE
NEAR US131...SOME PROGRESSION EAST/NORTHEAST WITH THE THREAT
SHOULD BE EXPECTED THROUGH THIS EVENING.

ADDITIONAL ROUNDS OF STORMS POSSIBLE THIS EVENING AND
OVERNIGHT...ESPECIALLY NEAR AND NORTH OF THE WARM FRONT THAT IS
STRETCHING ACROSS NORTHERN LOWER MICHIGAN.  STORM POSSIBILITIES ALSO
REMAIN TUESDAY AFTERNOON THOUGH SEVERE POTENTIAL FOR TUESDAY
AFTERNOON DOES SEEM TO BE SOMEWHAT LIMITED...AND WOULD BE MORE SO IF
MORNING ACTIVITY LIMITS AMOUNT OF WARMING THAT COULD OCCUR DURING
THE DAY.

THE MAIN PUSH OF THE UPPER SYSTEM WORKS TOWARD THE GREAT LAKES
WEDNESDAY BRINGING COLD AIR ALOFT TO THE REGION AND RAMPING UP THE
INSTABILITY. MODELS ARE TRENDING MORE TOWARD THIS BEING MORE OF A
RAIN EVENT THAN A SEVERE EVENT.

.LONG TERM...(THURSDAY THROUGH MONDAY)
ISSUED AT 238 PM EDT MON MAY 20 2013

COOLER END OF THE WEEK AND WEEKEND STILL THE FOCUS OF THE LONG
TERM...WITH SOME FROST THREAT REMAINING FOR FRIDAY MORNING...AND
ESPECIALLY SATURDAY MORNING.  NORTHERN MOST COUNTIES REMAIN THE MOST
THREATENED BY FROST...ESPECIALLY NORTH OF US-10 ON SATURDAY MORNING.
WILL MONITOR FOR POTENTIAL HEADLINES LATER IN THE WEEK BUT FROST
POTENTIAL IS CERTAINLY THERE FOR THE FIRST HALF OF THE WEEKEND.

OTHERWISE...SOME LINGERING LIGHT RAIN SHOWERS THROUGH THE DAY
THURSDAY THE ONLY NOTABLE WEATHER IN THE LONG TERM. NO SIGNIFICANT
IMPACTS EXPECTED FROM THIS LINGERING RAIN ON THURSDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1150 PM EDT MON MAY 20 2013

SHOWERS AND THUNDERSTORMS WILL OVERSPREAD LOWER MICHIGAN BETWEEN
06Z AND 08Z. THESE STORMS SHOULD BRING AREAS OF MVFR CONDITIONS
AND POSSIBLY BRIEF IFR THROUGH 10 TO 12Z. THEN SCATTERED SHOWERS
AND THUNDERSTORMS ARE EXPECTED FOR MUCH OF TUESDAY.

&&

.MARINE...
ISSUED AT 238 PM EDT MON MAY 20 2013

THUNDERSTORMS WILL POSE HAZARDS TO MARINERS THIS EVENING THROUGH
WEDNESDAY. FOG IS ALSO EXPECTED TO BE A HAZARD AS WELL TONIGHT AND
TUESDAY NIGHT.


&&

.FIRE WEATHER...
ISSUED AT 238 PM EDT MON MAY 20 2013

WARM AND FAIRLY HUMID WEATHER IS EXPECTED THROUGH WEDNESDAY.
THUNDERSTORMS WILL BRING LIGHTNING AND GUSTY WINDS AT TIMES TODAY
THROUGH WEDNESDAY.  COOLER WEATHER WITH A DRIER AIR MASS FOR THE END
OF THE WEEK THROUGH THE WEEKEND.

&&

.HYDROLOGY...
ISSUED AT 238 PM EDT MON MAY 20 2013

SOME LOCALIZED FLOODING COULD OCCUR THROUGH WEDNESDAY AS SEVERAL
ROUNDS OF THUNDERSTORMS MAY BRING HEAVY RAINFALL TO SOME AREAS.
PLACES THAT SEE MULTIPLE SHOWERS/THUNDERSTORMS IN QUICK SUCCESSION
WOULD BE PARTICULARLY VULNERABLE TO LOCALIZED FLOODING.

&&

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

$$

UPDATE...JK
SYNOPSIS...MACZKO
SHORT TERM...MACZKO
LONG TERM...MACZKO
AVIATION...OSTUNO
FIRE WEATHER...MACZKO
HYDROLOGY...LAURENS
MARINE...MACZKO