Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 271646
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1246 PM EDT WED MAY 27 2015

LATEST UPDATE...
HYDRO

.SYNOPSIS...
ISSUED AT 310 AM EDT WED MAY 27 2015

AN AREA OF LOW PRESSURE OVER LAKE SUPERIOR WILL TRACK AWAY FROM
THE REGION TODAY. THIS SYSTEM COULD STILL PRODUCE SOME SHOWERS AND
THUNDERSTORMS FOR THE REGION. TONIGHT AND THURSDAY A RIDGE OF HIGH
PRESSURE WILL BUILD IN FROM THE WEST. THIS SHOULD SUPPORT
RELATIVELY DRY AND WARM CONDITIONS. A SLOW MOVING COLD FRONT WILL
TRACK THROUGH THE GREAT LAKES REGION FRIDAY INTO SATURDAY CAUSING
SHOWERS AND THUNDERSTORMS FOR THE AREA.

&&

.UPDATE...
ISSUED AT 1152 AM EDT WED MAY 27 2015

CURRENT FORECASTS LOOK ON TRACK. SOME EVIDENCE THAT SEVERE THREAT
WILL SHIFT SLIGHTLY MORE TO THE SOUTHEAST. ONE THING TO WATCH IS
STRONG HORIZONTAL CONVECTIVE ROLL EXTENDING NORTHEAST FROM EXTREME
SOUTHWEST LOWER MICHIGAN THAT IS LIKELY BEING SOLENOIDALLY
ENHANCED BY LAKE MICHIGAN. THIS WILL LIKELY MARK THE NORTHWESTERN
EDGE OF THUNDERSTORM EXTENT THIS AFTERNOON SINCE THE STABLE
MARINE BOUNDARY LAYER HAS MOVED ONSHORE NORTH OF THIS BOUNDARY.
EXPECT SHOWERS AND STORMS TO DEVELOP SHORTLY ALONG THIS BOUNDARY.
HOWEVER...MORE DEVELOPED LINE EXTENDS ACROSS NORTHERN INDIANA INTO
FAR SOUTHEAST LOWER MICHIGAN AND IS IN A MORE FAVORABLE AREA FOR
SEVERE WEATHER. STILL THINKING IN LINE WITH SPC THAT THE MAIN
THREATS WILL BE GUSTY WINDS.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 310 AM EDT WED MAY 27 2015

THE MAIN CHALLENGE IN THE SHORT TERM DEALS WITH THE POTENTIAL FOR
THUNDERSTORMS TODAY.

MODELS SHOW THE ATMOSPHERE BECOMING UNSTABLE AGAIN
TODAY...PRIMARILY SOUTHEAST OF A HOLLAND TO MOUNT PLEASANT LINE.
NORTHWEST OF THIS LINE FORECAST SOUNDINGS THIS AFTERNOON DO NOT
SHOW MUCH CAPE ABOVE THE FREEING LEVEL. AS A RESULT I WILL
DOWNPLAY THE THUNDER RISK THERE. FURTHER SOUTHEAST SURFACE BASED
INSTABILITY LOWERS TO AT LEAST -3 DEG C AND SHOULD SUPPORT SOME
STORMS. DEEP LAYER SHEAR IS STILL FAVORABLE FOR ORGANIZED
CONVECTION...ESPECIALLY TOWARDS JACKSON. THUS AN ISOLATED SEVERE
STORM COULD OCCUR THERE.

I DO HAVE HIGHER POPS NORTHWEST OF GRAND RAPIDS...TOWARD
LUDINGTON. MODELS SUGGESTS THE TROWAL WILL PIVOT INTO THE
LUDINGTON REGION THIS AFTERNOON.

WILL MAINTAIN A MAINLY DRY FORECAST FOR TONIGHT THROUGH THURSDAY.
WILL NEED TO MONITOR THE POTENTIAL FOR AN ISOLATED STORM ON ANY
LAKE BREEZE THAT FORMS. SHOULD BE WARM GIVEN THE STRENGTHENING
WARM AIR ADVECTION THAT SHOWS UP IN THE AFTERNOON.

HIGH POPS WARRANTED FOR FRIDAY AS THE DEEPER MOISTURE ARRIVES FROM
THE WEST WITH A SLOW MOVING COLD FRONT APPROACHING. BETTER
INSTABILITY COULD SUPPORT SOME STRONGER STORMS

.LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY)
ISSUED AT 310 AM EDT WED MAY 27 2015

A SLOW MOVING COLD FRONT WILL COMBINE WITH HIGH PRECIPITABLE WATER
VALUES AND STRONG LOW LEVEL CONVERGENCE TO BRING POTENTIAL FOR HEAVY
RAIN AND THUNDERSTORMS FRIDAY NIGHT. RAINFALL TOTALS OF AN INCH OR
TWO WITH LOCALLY HIGHER AMOUNTS ARE POSSIBLE.

A CONSENSUS OF LATEST MEDIUM RANGE GUIDANCE CONTINUES TO INDICATE
HIGH PRESSURE WILL BUILD IN FROM THE NORTH AND BRING CLEARING SKIES
SATURDAY AND COOL AND FAIR WEATHER SATURDAY AFTERNOON THROUGH SUNDAY
INTO EARLY NEXT WEEK.

TEMPERATURES COULD DROP INTO THE 30S ACROSS COLDER LOCATIONS OF
ROUGHLY THE NORTHERN HALF OF OUR FORECAST AREA DURING THE EARLY
MORNING HOURS SUNDAY AND MONDAY. TEMPERATURES WILL THEN UNDERGO A
GRADUAL MODERATING TREND FOR THE MIDDLE OF NEXT WEEK.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 702 AM EDT WED MAY 27 2015

IFR AND LOWER CLOUDS WILL MOVE IN OFF OF LAKE MI IMPACTING MAINLY
KMKG THIS MORNING. CONDITIONS SHOULD IMPROVE IN THE AFTERNOON.
THUNDERSTORMS WILL LIKELY DEVELOP EARLY THIS AFTERNOON CLOSE TO
KBTL AND KLAN...BUT TRACK QUICKLY EAST. THE MAIN IMPACT SITE
SHOULD BE KJXN. EVEN WITHOUT STORMS...THE WIND WILL BE GUSTY
THROUGHOUT SW LOWER WITH SOME VALUES OVER 30 KNOTS LIKELY TODAY.

MVFR FOG COULD DEVELOP LATER TONIGHT. CONFIDENCE IS NOT THAT HIGH
ON THIS HAPPENING.

&&

.MARINE...
ISSUED AT 1152 AM EDT WED MAY 27 2015

CANCELED THE SMALL CRAFT ADVISORY AND BEACH HAZARDS STATEMENT
BASED ON LATEST BUOY OBSERVATIONS AND WEBCAMS. HOWEVER...DID ISSUE
A DENSE FOG ADVISORY THROUGH TODAY BASED ON LOW VISIBILITIES SEEN
ON AREA WEBCAMS.

&&

.HYDROLOGY...
ISSUED AT 1246 PM EDT WED MAY 27 2015

RIVER LEVELS ARE LOW AND STABLE ACROSS THE AREA. HAD 1/2 TO 3/4
OF AN INCH OF PRECIPITATION WITH THIS MOST RECENT SYSTEM... AND
SOME SMALL UP TICS NOTED ON AREA RIVERS. EXPECTING NO FLOODING
THROUGH THE WEEK.

A POTENTIAL FOR MORE RAIN FRIDAY INTO SATURDAY (OVER AN INCH) MAY
PUSH SOME STREAMS AND RIVERS ABOVE BANKFULL BY NEXT WEEK... IF
THESE AMOUNTS ARE REALIZED.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...DENSE FOG ADVISORY UNTIL 8 PM EDT THIS EVENING FOR LMZ845>849.

&&

$$

UPDATE...TJT
SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...LAURENS
AVIATION...MJS
HYDROLOGY...63
MARINE...TJT



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