000
FXUS63 KGRR 150426
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1226 AM EDT WED MAY 15 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 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1226 AM EDT WED MAY 15 2013

ISOLATED TSTMS ARE EXPECTED THROUGH ABOUT 10Z MAINLY FROM GRR
SOUTH AND EAST. OTHERWISE VFR CONDITIONS WILL PREVAIL OVERNIGHT
AND WEDNESDAY. EVEN ANY CB/S THAT DEVELOP OVERNIGHT SHOULD HAVE
HIGH CLOUD BASES AOA 5K FEET AND HAVE LITTLE IMPACT ON VSBYS.

SFC WINDS ARE EXPECTED TO INCREASE FROM THE SOUTHWEST TO 10 TO 20
KNOTS OVERNIGHT THEN SHIFT TO THE NORTHWEST EARLY WEDNESDAY
MORNING AND BECOME GUSTY BY MID MORNING.

&&

.MARINE...
ISSUED AT 1003 PM EDT TUE MAY 14 2013

WE HAVE ISSUED A SMALL CRAFT ADVISORY FOR THE ENTIRE NEARSHORE FOR
THE OVERNIGHT HOURS TONIGHT. THE NEXT LOW LEVEL JET WILL MOVE IN
OVERNIGHT TONIGHT. A LOOK BACK AT OBS FROM THIS MORNING WITH THE
INITIAL LOW LEVEL JET SHOWED THAT MOST LOCATIONS SAW A PERIOD OF A
FEW HOURS OF WINDS BETWEEN 20-25 KNOTS EVEN WITH STABLE CONDITIONS
IN PLACE. WE EXPECT A SIMILAR SCENARIO TONIGHT. WINDS SHOULD
DIMINISH TOWARD DAYBREAK WED MORNING.


&&

.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...SMALL CRAFT ADVISORY UNTIL 10 AM EDT THIS MORNING FOR LMZ844>849.

&&

$$

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