Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 050427
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1227 AM EDT TUE MAY 5 2015

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 325 PM EDT MON MAY 4 2015

FAIR WEATHER IS EXPECTED INTO TONIGHT THEN SOME SHOWERS AND
THUNDERSTORMS WILL RETURN LATE TONIGHT INTO TUESDAY AS LOW
PRESSURE TRACKS ALONG A FRONT STALLED JUST SOUTH OF LOWER
MICHIGAN. MOSTLY FAIR AND WARM WEATHER IS EXPECTED FOR WEDNESDAY
AND THURSDAY WITH SHOWERS AND THUNDERSTORMS OVER THE WEEKEND AS
ANOTHER LOW MOVES THROUGH.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 325 PM EDT MON MAY 4 2015

WENT WITH LOWER POPS AND LESS QPF THAN PREVIOUS FORECASTS IN THE
NEAR TERM AS THE TREND IN THE MODELS HAS BEEN DRIER. THE SFC
BOUNDARY IS STALLED TO THE SOUTH OF THE FORECAST AREA AND WE DO
NOT EXPECT ANY SHOWERS OR THUNDERSTORMS UNTIL MID LEVEL
ISENTROPIC ASCENT RAMPS UP LATE TONIGHT INTO TUESDAY MORNING. MAIN
FOCUS WILL BE ACROSS THE SOUTHERN FORECAST AREA LATE TONIGHT THEN
SPREADING NORTH ON TUESDAY.

SHEAR PROFILES AND INSTABILITY DO NOT SUPPORT SEVERE STORMS BUT
THUNDER IS EXPECTED ALONG AND JUST NORTH OF THE BOUNDARY... WHICH
LIFTS NORTH AND WASHES OUT BY LATE TUESDAY. SHORTWAVE UPPER
RIDGING BUILDS IN ON WEDNESDAY AND THIS SHOULD MEAN PRECIP CHANCES
ARE LIMITED. DECIDED TO GO WITH A DRY FORECAST FOR WEDNESDAY
ALTHOUGH AN ISOLATED SHOWER OR THUNDERSTORM CANNOT BE RULED OUT.
WE TWEAKED MAXES A BIT HIGHER ON WEDNESDAY GIVEN THAT UPPER
RIDGING SHOULD ALSO MEAN SUBSIDENCE AND MIXING OUT OF LOW CLOUDS.

.LONG TERM...(THURSDAY THROUGH MONDAY)
ISSUED AT 325 PM EDT MON MAY 4 2015

A CONSENSUS OF LATEST MEDIUM RANGE GUIDANCE CONTINUES TO SUGGEST
THAT TEMPERATURES WILL AVERAGE ABOVE TO MUCH ABOVE NORMAL THROUGH
THE LONG RANGE FORECAST PERIOD. MAX TEMPS SHOULD REACH THE UPPER 70S
TO LOWER 80S THURSDAY WITH STRONG SOUTHERLY FLOW WAA AND THE UPPER
RIDGE IN PLACE.

TEMPS WILL CONTINUE TO AVERAGE ABOVE NORMAL FRIDAY THROUGH THE
WEEKEND WITH INCREASING POTENTIAL FOR SCATTERED SHOWERS AND
THUNDERSTORMS AS LOW PRESSURE AND A BOUNDARY MOVES INTO OUR REGION.
THE BOUNDARY SHOULD THEN STALL OUT ACROSS THE GREAT LAKES REGION AND
PROVIDE A FOCUSING MECHANISM FOR CONVECTIVE INITIATION TO OCCUR WITH
A WARM AND FAIRLY HUMID AIRMASS IN PLACE BY THEN.

WEAK TO MODERATE INSTABILITY IS ANTICIPATED BY THEN WITH SB CAPE
VALUES POTENTIALLY REACHING AROUND 1000-2000 J/KG. THE RELATIVELY
BETTER CHANCE FOR THUNDERSTORMS WOULD LIKELY COME SATURDAY THROUGH
MONDAY WITH A QUASI STATIONARY FRONTAL BOUNDARY ALREADY IN THE
REGION AND AS THE MAIN LOW PRESSURE SYSTEM AND UPPER TROUGH AXIS
SLOWLY APPROACH FROM THE WEST BY SUNDAY/MONDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1224 AM EDT TUE MAY 5 2015

MODELS HAVE SHIFTED TOWARDS MORE IN THE WAY OF RAIN AND LOWER
CLOUDS AS WE HEAD INTO THE DAY ON TUESDAY. MUCH OF THE REST OF THE
NIGHT SHOULD CONTINUE TO BE VFR AND RAIN FREE. AS WE HEAD TOWARDS
12Z...SHOWERS AND A FEW EMBEDDED THUNDERSTORMS WILL BE ENCROACHING
ON KMKG AND KAZO. PERIODS OF SHOWERS AND A FEW STORMS ARE EXPECTED
ON TUESDAY WITH CEILINGS AND VISIBILITIES TRENDING DOWNWARD. IT
APPEARS WE WILL BE TRENDING TOWARD IFR AS WE WILL BE LOCATED JUST
NORTH OF A WARM FRONT IN EASTERLY WINDS.

BOTTOM LINE...DETERIORATING AVIATION CONDITIONS BEGINNING AROUND
DAYBREAK TUESDAY LASTING RIGHT INTO TUESDAY EVENING. CEILINGS WILL
BE TRENDING TO IFR IN ALL AREAS TUESDAY MORNING.

&&

.MARINE...
ISSUED AT 325 PM EDT MON MAY 4 2015

SOME AREAS OF FOG WILL PERSIST INTO THE EVENING SOUTH OF MUSKEGON.
THE FOG SHOULD DIMINISH LATER THIS EVENING AS DRIER AIR MOVES IN
FROM THE WEST. WINDS AND WAVES  WILL BE RELATIVELY LIGHT BUT SOME
THUNDERSTORMS ARE POSSIBLE LATE TONIGHT AND EARLY ON TUESDAY.

&&

.HYDROLOGY...
ISSUED AT 1137 AM EDT MON MAY 4 2015

THE FOCUS WILL BE ON THE ADDITIONAL BOUTS OF RAINFALL POSSIBLE IN
THE WEEK AHEAD.

WHILE THE PATTERN STILL LOOKS ACTIVE IT IS NOT PROMISING THAT WE
WILL SEE ANY WIDESPREAD HEAVY RAIN. BENEFICIAL AMOUNTS SHOULD
AVERAGE OUT TO A QUARTER INCH OR SO WITH EACH EPISODE THROUGH THE
WORK WEEK. THAT MAY LEAD TO DECENT TOTALS IN THE GRAND SCHEME BUT
NOTHING THAT PUTS RIVERS OVER THEIR BANKS.

THE NEXT CHANCE OF RAIN COMES WHEN THE STALLING FRONT TO OUR SOUTH
RETURNS AS A WARM FRONT TUESDAY AND INTO EARLY WEDNESDAY. EVEN
THIS LOOKS TO COME IN A PIECE-WISE FASHION...ONCE LATE TONIGHT AND
AGAIN LATE TUESDAY INTO EARLY WEDNESDAY. THE BEST CHANCE AT RAIN
THEN ENTERS THE PICTURE LATE IN THE WEEK AND INTO NEXT WEEKEND WITH
AN APPROACHING SYSTEM. THIS IS WHEN WE COULD PICK UP OUR HIGHEST
TOTALS...PENDING THE NORTHERN EXTENT OF THE WARM FRONT OUT AHEAD
OF THE SYSTEM. SEVEN DAY TOTALS ON THE ORDER OF AN INCH TO AROUND
AN INCH AND A HALF KEEP CONCERNS LOW AS IT IS RECEIVED IN CHUNKS
WITH SEVERAL HOURS OF DRY TIME BETWEEN. LOCALIZED HEAVIER RAINFALL
CANNOT BE RULED OUT...BUT DURATION AND COVERAGE IS NOT LOOKING
EXTENSIVE AT THIS POINT.

&&

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

$$

SYNOPSIS...OSTUNO
SHORT TERM...OSTUNO
LONG TERM...LAURENS
AVIATION...DUKE
HYDROLOGY...JAM
MARINE...OSTUNO





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