Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 020729
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
329 AM EDT THU APR 2 2015

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

.SYNOPSIS...
ISSUED AT 329 AM EDT THU APR 2 2015

PERIODS OF RAIN SHOWERS EXPECTED TODAY WITH PERHAPS SOME RUMBLES
OF THUNDER. MODERATE TO BRIEF HEAVY RAINFALL...ALONG WITH GUSTY
WINDS CANNOT BE RULED OUT INTO THE AFTERNOON AS A COLD FRONT
SWEEPS THROUGH THE REGION...BUT SEVERE WEATHER IS NOT EXPECTED.
MUCH COOLER WEATHER MOVES IN TONIGHT INTO THE WEEKEND...AND ACTIVE
WEATHER IS EXPECTED TO CONTINUE. RAIN CHANCES RETURN FRIDAY
AFTERNOON ACROSS SOUTHERN LOWER MICHIGAN WITH A CHANCE FOR A
RAIN/SNOW MIX FRIDAY NIGHT. FREQUENT BOUTS OF PRECIPITATION ARE
EXPECTED SUNDAY INTO THE MIDDLE OF NEXT WEEK.

&&

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 329 AM EDT THU APR 2 2015

PERIODS OF RAIN SHOWERS WITH PERHAPS A RUMBLE OF THUNDER TODAY
FOLLOWED BY MUCH COOLER WEATHER FRIDAY AND SATURDAY.

A DRY VERTICAL PROFILE IS NOTED ON A 05Z RAP SOUNDING...BUT HEALTHY
MID LEVEL MOISTURE ADVECTION WILL OCCUR FROM THIS WRITING THROUGH
THE NEXT SEVERAL HOURS. H925 TO H850 LAYER WAA IS ALSO ONGOING
DURING THIS TIMEFRAME WITH STRONG SOUTHWESTERLY FLOW AHEAD OF THE
H850 THERMAL TROUGH. AT THE LOW LEVELS...MUCH HIGHER THETA E AIR
ADVECTS IN AFTER 12Z THIS MORNING JUST AHEAD OF THE SURFACE COLD
FRONT. DEWPOINTS IN THE LOWER 50S ARE EXPECTED THIS AFTERNOON ACROSS
THE SOUTHERN HALF OF THE FORECAST AREA.

A WEAK SHORTWAVE NOTED OVER WESTERN IL ON WATER VAPOR IMAGERY WILL
CONTINUE TO TRACK NORTHEAST INTO OUR AREA BUT LOSE SOME OF ITS
PUNCH. NEVERTHELESS...WEAK ELEVATED INSTABILITY IS PRESENT AT THE
TIME OF ITS ARRIVAL AROUND 12Z. RAIN CHANCES...WITH PERHAPS A RUMBLE
OF THUNDER...INCREASE AFTER 11Z. THE COLD FRONT TRACKS THROUGH THE
CWA BETWEEN 16-22Z. DIURNAL HEATING JUST PRIOR TO THIS FRONTAL
PASSAGE WILL GIVE MOST AREAS THEIR BEST CHANCE FOR THUNDER AND
ASSOCIATED NON-SEVERE THREATS...SUCH AS MODERATE TO BRIEF HEAVY
RAIN...GUSTY WINDS...AND LIGHTNING. INSTABILITY IS MARGINAL AT
BEST...BUT HIGHEST SOUTH OF I-96. 0-6 KM BULK SHEAR INCREASES
THROUGHOUT THE DAY...WITH VALUES OF AROUND 35-45 KNOTS SOUTH OF I-96
AT 18Z. BOTTOM LINE...RAIN SHOWERS WITH A CHANCE OF THUNDER INTO THE
AFTERNOON.

BEHIND THE FRONT...DRY WEATHER EXPECTED TONIGHT WITH LOWS IN THE 30S
TO AROUND 40 DEGREES. ANOTHER PV ANOMALY AND SHORTWAVE MOVE INTO THE
AREA TOMORROW...SUPPORTING MAINLY A CHANCE OF RAIN ACROSS THE
SOUTHERN FORECAST AREA FRIDAY AFTERNOON AND A MIX OF RAIN AND SNOW
FRIDAY NIGHT. LOWER MI IS IN A FAVORABLE POSITION WITHIN A COUPLED
UPPER JET STRUCTURE DURING THIS TIMEFRAME...MEANING GOOD UPPER
DIVERGENCE IS RESPONSIBLE FOR STRENGTHENING OF THE MIDLEVEL
SHORTWAVE. LOWS FRIDAY NIGHT ARE EXPECTED TO PLUMMET INTO THE UPPER
TEENS AND 20S.

&&

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 329 AM EDT THU APR 2 2015

LOOKS LIKE AN ACTIVE STORM TRACK SETTING UP IN THE EXTENDED PERIOD
WITH FREQUENT BOUTS OF PRECIPITATION...INCLUDING SOME SNOW AT TIMES.

A PLAINS LOW MOVES EAST TOWARDS THE GREAT LAKES SATURDAY NIGHT AND
ISENTROPIC ASCENT OUT AHEAD OF IT SHOULD RESULT IN SOME LIGHT SNOW
AND RAIN SATURDAY NIGHT. IT TAKES UNTIL MONDAY AFTERNOON BEFORE THE
COLD AIR HAS ERODED ENOUGH TO ALLOW FOR A FORECAST OF ALL RAIN
ACROSS THE ENTIRE FORECAST AREA. BEST CHANCE FOR STEADY RAIN WILL BE
ON MONDAY NIGHT AS THE SFC WAVE TRACKS ALONG THE FRONT DRAPED ACROSS
LOWER MICHIGAN.

A SECOND WAVE PROLONGS THE PRECIP INTO TUESDAY NIGHT...AND ENOUGH
COLD AIR RETURNS TO BRING THE POSSIBILITY OF A MIX ACROSS THE
NORTHERN FORECAST AREA BEFORE THE PRECIP TAPERS OFF ON WEDNESDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1116 PM EDT WED APR 1 2015

MOISTURE RIDING NORTHEASTWARD AHEAD OF COLD FRONT WHICH IS LOCATED
IN MINNESOTA WILL TRACK INTO MICHIGAN LATE TONIGHT AND THURSDAY
MORNING. THIS WILL SUPPORT SHOWERS AND THUNDERSTORMS... BEGINNING
AROIUND DAYBREAK FOR KMKG. AS THE FRONT TRACKS THROUGH MI DURING
THE DAY ON THU...THERE WILL BE ADDITIONAL SHOWERS AND
THUNDERSTORMS WITH ASSOCIATED IMPACTS. IFR CONDITIONS LOOK LIKELY
TO DEVELOP AS THE WINDS BECOME MORE WESTERLY BEHIND THE FRONT. IT
IS NOT CLEAR HOW LONG THE IFR WILL LAST...BUT IMPROVEMENT IS
EXPECTED DURING THE EVENING.


&&

.MARINE...
ISSUED AT 315 PM EDT WED APR 1 2015

SOUTHERLY WINDS WILL INCREASE THROUGH THE EVENING HOURS AHEAD OF AN
APPROACHING COLD FRONT. SMALL CRAFT ADVISORY CONDITIONS ARE EXPECT
THROUGH THE NIGHT AND MUCH OF THURSDAY.  SHOWERS AND A FEW
THUNDERSTORMS WILL SWEEP ACROSS THE REGION THURSDAY MORNING AND
EARLY AFTERNOON.


&&

.HYDROLOGY...
ISSUED AT 1120 AM EDT TUE MAR 31 2015

RIVERS CONTINUE TO REMAIN WELL BELOW ADVISORY LEVELS WITH ONLY SMALL
AND MOMENTARY RESPONSES NOTED FROM RECENT PRECIPITATION. NORTHERN
SECTIONS OF THE FORECAST AREA WILL SEE SLOWER RESPONSES DUE TO
SNOW MELT WITH LAST NIGHTS SNOWFALL.

WE WILL SEE A RATHER ACTIVE PATTERN SET UP THROUGH THE NEXT 7
DAYS. MUCH OF THIS COMES IN TWO WAVES...ONE THURSDAY THEN THE
SECOND VERY LATE IN THE WEEKEND AND INTO THE NEXT WORK WEEK. GENERAL
AMOUNTS ON TOTAL PRECIPITATION THROUGH THE PERIOD ARE AROUND ONE
INCH OR SO. THIS IS FAIRLY EVENLY DIVIDED BETWEEN THE TWO WAVES
WHICH SHOULD BE FAVORABLE FOR RESPONSE TIMES. NO FLOODING IS
EXPECTED AT THIS TIME. HOWEVER...THE HEAVIER RAIN THAT IS
ANTICIPATED TO OUR SOUTH THROUGH THE OHIO VALLEY SHOULD BE WATCHED
IN THE EVENT THAT ANY ADJUSTMENTS ARE NEEDED IN PRECIPITATION
AMOUNTS.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 2 PM EDT THIS AFTERNOON FOR
     LMZ844>849.

&&

$$

SYNOPSIS...EBW
SHORT TERM...EBW
LONG TERM...OSTUNO
AVIATION...MJS
HYDROLOGY...JAM
MARINE...MANN





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