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000
FXUS63 KGRR 142355
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
755 PM EDT TUE MAY 14 2013

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 237 PM EDT TUE MAY 14 2013

A WEAK COLD FRONT WILL PUSH THROUGH LOWER MICHIGAN TONIGHT. A FEW
THUNDERSTORMS COULD DEVELOP ALONG THIS FRONT AS IT PUSHES THROUGH.
WEAK HIGH PRESSURE WILL MOVE IN BEHIND THE FRONT AND REMAIN ACROSS
MICHIGAN THROUGH THURSDAY NIGHT. A WARM FRONT WILL MOVE IN FROM
THE SOUTH FOR THE END OF THE WEEK AND INTO THE WEEKEND LEADING TO
MILD AND UNSETTLED WEATHER.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 237 PM EDT TUE MAY 14 2013

THE MAIN CHALLENGE IN THE SHORT TERM DEALS WITH THE POTENTIAL FOR
SHOWERS AND THUNDERSTORMS TONIGHT AND WEDNESDAY.

WILL KEEP A LOW CHANCE GOING TONIGHT...BUT DRY FOR WEDNESDAY. THE LOW
LEVEL JET WHICH FOCUSED LAST NIGHTS CONVECTION IN THE UPPER PLAINS
ARRIVES IN MI TONIGHT. ALONG WITH IT WILL BE SOME ELEVATED
INSTABILITY. THE CURRENT SHOWER ACTIVITY IN WI CONTINUES TO DROP
SOUTHEAST AND WEAKEN. THIS COULD LEAD TO A FEW LIGHT RAIN SHOWERS
IN SOUTHWEST MI THROUGH MIDNIGHT. AFTER MIDNIGHT WE WILL SEE MORE
STORMS DEVELOPING IN WI...WHICH SHOULD TRACK EAST SOUTHEAST ON
THE NOSE OF THE LLJ. THIS LLJ...WHILE STRONGER...IS AIMED MORE
INTO IN AND OH...SO IT REMAINS UNCLEAR AS TO WHETHER WE WILL
ACTUALLY SEE RAIN HERE IN LOWER MI TONIGHT. HUMIDITY WILL ALSO BE
A LIMITING FACTOR FOR RAIN CHANCES AS THE LOW LEVELS REMAIN FAIRLY DRY.

BY 12Z THE INSTABILITY AXIS IS EAST OF LANSING. SO WILL FEATURE A
DRY FORECAST FOR WED. AS MIXING DEVELOPS IT WILL BECOME WINDY. I
HAVE INCREASED THE WINDS. TEMPERATURES WERE NUDGED SLIGHTLY
DOWNWARD GIVEN THE WESTERLY FLOW FROM LAKE MI.

TEMPERATURES THIS EVENING WILL BE WARM. SOUTHWEST FLOW AND
UPSTREAM TEMPERATURES IN THE 80S TO NEAR 90 SUPPORT THIS.

.LONG TERM...(FRIDAY THROUGH TUESDAY)
ISSUED AT 237 PM EDT TUE MAY 14 2013

MEDIUM RANGE MODELS HAVE TRENDED DRIER FOR THE WEEKEND AS THE UPPER
RIDGE REMAINS STOUT.  THEREFORE HAVE TRENDED POPS DOWN SLIGHTLY...
BUT HAVE NOT COMPLETELY ABANDON THE RISK OF SHOWERS.  HOWEVER...THE
MAIN RISK OF SHOWERS AND STORMS LOOKS TO BE DELAYED UNTIL EARLY NEXT
WEEK.

EARLY ON IN THE EXTENDED PERIOD THERE WILL BE A SHORT WAVE THAT WILL
TRY TO BREAK THROUGH THE UPPER RIDGE...PRODUCING LOW CHANCES POPS
FOR FRIDAY NIGHT.

HAVE GONE DRIER HOWEVER FOR SATURDAY AND SUNDAY AS THE RIDGE SHOULD
REESTABLISH ITSELF.  THE MEAN FLOW WILL BE SSE WHICH MAY BRING UP
SOME GULF MOISTURE...BUT THIS APPEARS MUCH WEAKER NOW.  WILL LOWER
POPS TO 20 PERCENT FOR MUCH OF THE WEEKEND.

THE RIDGE FINALLY PUSHES EAST BY SUNDAY NIGHT ALLOWING THE MEAN FLOW
TO BECOME MORE SOUTHERLY BRINGING DEEPER GULF MOISTURE NORTHWARD.
THIS REMAINS THE PATTERN RIGHT INTO TUESDAY AS UNSETTLED WEATHER
APPEARS TO DOMINATE.  WILL HAVE TO CONTINUE TO MONITOR TRENDS OF
THIS UPPER RIDGE AS SOME ADDITIONAL SLOWER TWEAKING MAY BE NEEDED
WITH FUTURE FORECASTS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 755 PM EDT TUE MAY 14 2013

THE MAIN AVIATION CONCERN IS THE POTENTIAL FOR A FEW TSTMS
OVERNIGHT. THE CHANCE/COVERAGE OF STORMS SHOULD BE RATHER LIMITED...
BUT STILL WORTHY OF A 4 TO 6 HOUR MENTION OF VCTS/CB IN THE TAFS.
PRETTY MUCH KEPT CONSISTENCY WITH THE 18Z TAFS.

OUTSIDE OF THE TSTM RISK... VFR CONDITIONS WILL CONTINUE TONIGHT
AND WEDNESDAY. EVEN ANY CB/S THAT DEVELOP OVERNIGHT SHOULD HAVE
HIGH CLOUD BASES AOA 6K FEET.

SFC WINDS ARE EXPECTED TO INCREASE FROM THE SOUTH TO 10 TO 20
KNOTS AFTER MIDNIGHT THEN SHIFT TO THE WEST/NORTHWEST ON WEDNESDAY
MORNING.

&&

.MARINE...
ISSUED AT 237 PM EDT TUE MAY 14 2013

AS THE LAKE IS RELATIVELY STABLE THIS TIME OF THE YEAR...WAVES
WILL REMAIN UNDER SMALL CRAFT ADVISORY CRITERIA EVEN THOUGH THERE
WILL BE SOME GUSTY CONDITIONS THIS EVENING AND AGAIN ON WEDNESDAY.


&&

.FIRE WEATHER...
ISSUED AT 237 PM EDT TUE MAY 14 2013

CONDITIONS MAY APPROACH RED FLAG CRITERIA ON WEDNESDAY. THIS
LIMITING FACTOR IS EXPECTED TO BE THE HUMIDITY. HOWEVER MODELS DO
TYPICALLY STRUGGLE WITH THE SURFACE MOISTURE...AND I DID LOWER
DEWPOINTS BY SEVERAL DEGREES TO ACCOUNT FOR THIS. STILL ENDED UP
WITH AFTERNOON HUMIDITY LEVELS IN THE 30 PERCENT RANGE.

&&

.HYDROLOGY...
ISSUED AT 237 PM EDT TUE MAY 14 2013

ANY SHOWER ACTIVITY SHOULD BE LIMITED OVER THE NEXT SEVERAL DAYS.
RUNOFF IS NOT EXPECTED TO CAUSE RIVER LEVELS TO RISE. GULF
MOISTURE ARRIVES FOR THE WEEKEND INTO EARLY NEXT WEEK. AS A RESULT
A BETTER RISK FOR HEAVIER SHOWERS WILL EXIST.

&&

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

$$

SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...JK
AVIATION...MEADE
FIRE WEATHER...MJS
HYDROLOGY...MJS
MARINE...MJS