Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 020728
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
328 AM EDT SAT MAY 2 2015

LATEST UPDATE...
SYNOPSIS/SHORT TERM/LONG TERM/MARINE

.SYNOPSIS...
ISSUED AT 328 AM EDT SAT MAY 2 2015

PLEASANT WEATHER WILL HOLD THROUGH THE WEEKEND.  70S CAN BE EXPECTED
EACH DAY.  THE REGION WILL SEE PLENTY OF SUNSHINE TODAY...BUT A FEW
MORE CLOUDS WILL BE AROUND BY SUNDAY.  SHOWERS AND A FEW
THUNDERSTORMS WILL MOVE INTO SOUTHWEST MICHIGAN SUNDAY NIGHT INTO
MONDAY.  THE STORMS ARE NOT EXPECTED TO BE SEVERE.

THE FRONT THAT PRODUCES THE SHOWERS AND STORMS STALLS TO OUR SOUTH
INTO MID WEEK.  THIS MAY RESULT IN LINGERING RAIN THROUGH WEDNESDAY.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 328 AM EDT SAT MAY 2 2015

WE WILL SEE A VERY PLEASANT WEEKEND THAT WILL BE FOLLOWED BY SHOWERS
AND A FEW STORMS SUNDAY NIGHT INTO MONDAY.

RATHER DRY AIR MASS IN PLACE AGAIN TODAY.  THE CI CLOUDS OVERHEAD
THIS MORNING SHOULD GRADUALLY THIN ALLOWING FOR PLENTY OF SUNSHINE.
THIS WILL ALLOW FOR DEEP MIXING...MUCH LIKE WHAT WE SAW FRIDAY...AND
TEMPS SHOULD RESPONSE.  RAISED MAX TEMPS SEVERAL DEGREES...MAINLY IN
THE MID 70S AWAY FROM THE LAKESHORE.  MUCH OF THE SAME STORY FOR
SUNDAY...ALTHOUGH MIXING SHOULDN/T BE AS STRONG GIVEN AN INCREASE IN
MID LEVEL WARM ADVECTION CLOUDS.  BUT WILL STILL BUMP TEMPS SLIGHTLY
INTO THE MID AND UPPER 70S AWAY FROM THE LAKE.

BY SUNDAY NIGHT A COLD FRONT WILL BE CUTTING ACROSS WISCONSIN AND
INTO THE CWA ON MONDAY.  THE JET DYNAMICS WEAKEN QUITE A BIT AS THE
FRONT SLIDES OUR WAY.  A LOW LEVEL JET OVER WISCONSIN SUNDAY NIGHT
WEAKENS CONSIDERABLY BY MONDAY AS THE FRONT GRADUALLY BECOMES MORE
ALIGNED WITH THE UPPER FLOW.  MEANWHILE THE FAVORABLE UPPER JET
DIVERGENCE DOES MAKE IT HERE MONDAY...BUT ALSO IN A WEAKENING
STATE.  ALONG WITH THE THIS WE DON/T APPEAR TO BECOME TOO UNSTABLE
ON MONDAY DUE TO ABUNDANT CLOUD COVER...SO A SEVERE THREAT LOOKS
VERY LOW TO NONE.

ON THE POSITIVE SIDE THE FRONT WILL BE RUNNING INTO A FAIRLY
MOISTURE AIR MASS WITH DEW POINTS IN THE LOWER 50S...SO RAIN CHANCES
LOOK LIKE A GOOD BET.  RAISED POPS TO LIKELY ACROSS THE NORTHERN
CWA...AND CATEGORICAL ACROSS THE CENTRAL AND SOUTH.  THE FRONT
SHOULD PUSH SOUTH TO NEAR THE MI/IN BORDER BY THE END OF THE
DAY...SO MOST OF THE SHOWERS SHOULD END NORTH OF I-96 THROUGH THE
MID AFTERNOON/EARLY EVENING.

.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 328 AM EDT SAT MAY 2 2015

THE MAIN CHALLENGE IN THE LONG TERM WILL BE DETERMINING CHANCES FOR
PRECIP MONDAY NIGHT AND TUESDAY WITH GROWING CONFIDENCE IN OUR FIRST
80 DEGREE READINGS BY THURSDAY AND MAYBE FRIDAY TOO.

WAS HOPING FOR BETTER MODEL CONSENSUS FOR MONDAY NIGHT AND TUESDAY`S
FRONTAL BOUNDARY PLACEMENT BUT DIVERGENCE REMAINS. AT 12Z
TUESDAY...THE H850 THERMAL GRADIENT AND WIND FIELDS FROM THE ECMWF
REVEAL THE BOUNDARY STAYS OVER NORTHERN INDIANA AND SUBSEQUENTLY
THAT IS WHERE ANY SHOWERS/STORMS WOULD BE. THE GEM HAS THE BOUNDARY
FROM KALAMAZOO TO JACKSON WHILE THE GFS HAS IT FROM GRAND RAPIDS TO
LANSING. I BELIEVE THE 00Z GFS IS STRAYING FROM REALITY WHEN LOOKING
AT THE ABRUPT H850 THERMAL PLUNGE ACROSS THE CENTRAL CWA FROM 06Z TO
12Z TUESDAY. THERE IS A MINIMUM BULLSEYE FROM GRR TO MOP WITH TEMPS
DROPPING 5-6C IN 6 HOURS. NOT BUYING THAT...AND WONDERING IF THIS IS
A CONVECTIVE FEEDBACK MISCUE AND IF THE PRECIP SHIELD IS TOO FAR
NORTH WITH THE 00Z RUN (AND THE PRIOR 12Z RUN).

ALL THIS SAID...THE BEST FORCING FOR PRECIP SHOULD BE ACROSS OUR
SOUTHERN CWA AND INTO NORTHERN INDIANA MONDAY NIGHT AND TUESDAY WHEN
CONSIDERING A GEM/ECMWF COMPROMISE. WITH A WEAK LLJ IN PLACE IT
APPEARS THE THREAT FOR HEAVIER RAINFALL IS LIMITED...AND PW VALUES
ARE NOT EXCEPTIONALLY HIGH NEAR/SOUTH OF THE BOUNDARY. ON
WEDNESDAY...THE BOUNDARY LIFTS NORTH AS A WARM FRONT AND PRECIP
SHOULD BE WIDELY SCATTERED WITH DRY CONDITIONS MUCH OF THE TIME.

BY THURSDAY...WE WILL BE SQUARELY IN THE WARM SECTOR WITH HIGHS OF
80 CERTAINLY ACHIEVABLE. ALTHOUGH SFC BASED CAPE WILL BE PRESENT
THERE IS LITTLE FORCING AVAILABLE SO SHOWERS/STORMS WILL BE QUITE
SPOTTY AND MUCH OF THE DAY SHOULD BE DRY. WITH H850 TEMPS POSSIBLY
NEAR 14C NEXT FRIDAY...HIGHS INTO THE LOW 80S ARE POSSIBLE BUT
CURRENTLY PLAYING IT CONSERVATIVE WITH MID-UPPER 70S.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1128 PM EDT FRI MAY 1 2015

VFR CONDITIONS ARE EXPECTED TO PREVAIL AT ALL TAF SITES THROUGH AT
LEAST SUNDAY MORNING. THE HIGH CLOUD COVER WILL MOVE OUT OF THE
AREA BY MID MORNING SATURDAY. WINDS WILL BE LIGHT FROM THE
SOUTHWEST INTO SUNDAY MORNING.

&&

.MARINE...
ISSUED AT 328 AM EDT SAT MAY 2 2015

SOUTH SOUTHWEST WINDS WILL PREVAIL THROUGH THE WEEKEND AND WILL BE
FAIRLY BREEZY.  GIVEN THE FETCH AND INCREASING WINDS BY SUNDAY INTO
SUNDAY NIGHT...AREAS NORTH OF GRAND HAVEN SHOULD SEE WAVES
INCREASING TO AROUND 3 FEET...BUT FEEL WE WILL STAY BELOW A SMALL
CRAFT ADVISORY.

THE WINDS WILL SHIFT AROUND ON MONDAY AS THE FRONT COMES
ACROSS...STARTING OFF FROM THE SW...BUT FINISHING THE DAY FROM THE
NORTH.  DUE TO THE BAGGIER WINDS NEAR THE FRONT...WAVES SHOULD
DIMINISH THROUGH THE DAY.

&&

.HYDROLOGY...
ISSUED AT 315 PM EDT FRI MAY 1 2015

RIVERS ARE RUNNING NEAR TO BELOW NORMAL AND NO ISSUES ARE EXPECTED
THROUGH THE WEEKEND. PERIODS OF RAIN AND THUNDERSTORMS DURING THE
FIRST HALF OF NEXT WEEK MAY LEAD TO SOME LOCATIONS RECEIVING AN INCH
OR MORE OF RAINFALL. WITH THE RECENT DRY WEATHER AND THE GREEN-UP
UNDERWAY... THIS WATER IS LIKELY TO BE ABSORBED BY SOIL... PLANTS...
AND RIVERS WITH NO NEGATIVE CONSEQUENCE.

&&

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

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...HOVING
AVIATION...WDM
HYDROLOGY...CAS
MARINE...JK








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