Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 301504
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1104 AM EDT TUE SEP 30 2014

LATEST UPDATE...
MARINE

.SYNOPSIS...
ISSUED AT 335 AM EDT TUE SEP 30 2014

LOW CLOUDS WILL HANG ON TODAY AND TONIGHT BEHIND A FRONTAL PASSAGE
THAT MOVED THROUGH THE AREA MONDAY EVENING. THE FRONT USHERED IN
MORE FALL LIKE COOL AIR ON NORTHERLY WINDS. THE CLOUDS WILL BREAK ON
WEDNESDAY AS HIGH PRESSURE SLIDES THROUGH THE AREA. A COLD FRONT
WILL PUSH THROUGH THE STATE THURSDAY AND THURSDAY NIGHT WITH SHOWERS
AND THUNDERSTORMS EXPECTED. COOL AND SHOWERY WEATHER IS EXPECTED IN
THE WAKE OF THIS FRONT FOR NEXT WEEKEND.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 335 AM EDT TUE SEP 30 2014

PRECIPITATION IS SHIFTING SOUTH OF THE AREA THIS MORNING...AND
EXPECTING A MAINLY DRY DAY. CLOUDS WILL HANG ON TODAY AND THINKING
THEY WILL LIKELY REMAIN TONIGHT AS WELL. CLIMATOLOGY AND COOL
CYCLONIC FLOW TREND THE FORECAST IN THAT DIRECTION. NAM12 BUFKIT
OVERVIEW SHOWS EXTENSIVE CLOUDS...POTENTIALLY LASTING INTO WEDNESDAY
AS WELL. AT THIS POINT HAVE MOSTLY CLOUDY SKIES FOR BOTH TODAY AND
TONIGHT AND WE TREND THE FORECAST TO PARTLY CLOUDY ON WEDNESDAY.
WOULD NOT BE SURPRISED TO SEE THE CLOUDS HANG IN THOUGH.

NEXT FORECAST FOCUS IS ON THURSDAY AS MOISTURE SURGES INTO THE AREA
FROM THE SOUTH AND SOUTHWEST. MOST UNSTABLE CAPE VALUES INCREASE TO
AROUND 1000 J/KG OVER SOUTHWEST LOWER MICHIGAN THURSDAY AFTERNOON ON
THE NOSE OF A 30-40 KNOT LLJ. HAVE SHOWERS AND STORMS IN THE
FORECAST GIVEN THE STRENGTH OF THE LOW LEVEL JET AND THE INSTABILITY
PRESENT. AT THIS POINT NOT EXPECTING SEVERE WEATHER AS THE FRONT IS
STILL WELL WEST OF THE AREA DURING THE DAY AND INSTABILITY IS NOT
ALL THAT IMPRESSIVE. WIDESPREAD SHOWERS AND STORMS SHOULD BE ONGOING
BY THE END LATE AFTERNOON AND EVENING.

SHOWERS WILL LIKELY START LATE WEDNESDAY NIGHT IN THE WEST AS THE
MOISTURE STARTS TO MOVE IN. THURSDAY WILL BE THE WARMEST DAY OF THE
NEXT 7 IN THE SOUTHERLY WINDS AHEAD OF THE FRONT. HIGHS WILL RANGE
FROM NEAR 70 NORTH TO THE MIDDLE 70S SOUTH.

.LONG TERM...(THURSDAY NIGHT THROUGH MONDAY)
ISSUED AT 335 AM EDT TUE SEP 30 2014

THE LONG TERM PORTION OF THE FCST IS EXPECTED TO EXPERIENCE MUCH
COOLER AND MORE UNSETTLED WEATHER COMPARED TO THE WARM AND DRY
PERIOD THAT IS COMING TO AN END TODAY.

WE WILL SEE QUITE A WET PERIOD WITH A FEW STORMS POSSIBLE FOR THE
THU NIGHT INTO FRI PERIOD. THE STRONG UPPER TROUGH COMING ONSHORE
OVER THE PACIFIC NW THIS MORNING WILL DIG ACROSS THE CENTRAL ROCKIES
AND PLAINS STATES BEFORE LIFTING OUT TO THE NE LATE THU AND INTO
FRI. THIS SYSTEM DIGGING S WILL ALLOW IT TO TAP GULF OF MEXICO
WARMTH AND MOISTURE AND ADVECT IT NORTH INTO THE AREA.

RAIN LOOKS LIKE THE BIGGEST THREAT WITH THIS SYSTEM. THERE IS STRONG
DEEP LAYER SHEAR AND LOW LEVEL /0-3KM/ SETTING UP...HOWEVER
INSTABILITY IS FAIRLY LIMITED PER FCST SOUNDINGS. AT THIS POINT WE
ARE NOT EXPECTING A WIDESPREAD SEVERE EVENT. THE FRONT WILL MOVE
THROUGH DURING THE FIRST HALF OF FRI...WHICH WILL ALLOW THE RAIN AND
STORMS TO DIMINISH DURING THE SECOND PORTION OF THE DAY.

THE REMAINDER OF THE WEEKEND AND INTO EARLY NEXT WEEK LOOKS TO BE
COOL AND UNSETTLED THEN. WE SEE THE SYSTEM LIFTING OUT OF THE PLAINS
INTO THE AREA...AND ADDITIONAL STRONG ENERGY WILL DIVE IN ON THE
BACKSIDE OF THE TROUGH. THIS...ALONG WITH A STRONG UPPER RIDGE
BUILDING OVER THE ERN PACIFIC AND WRN U.S. COAST...WILL HELP TO FORM
A STRONGER LONG WAVE TROUGH THAT IS EXPECTED TO SIT OVER THE REGION.
ADDITIONAL SHORT WAVE ENERGY WILL OCCASIONALLY MOVE THROUGH
ENHANCING THE THREAT FOR SOME RAIN SHOWERS AT TIMES. THERE WILL
LIKELY BE SOME LAKE ENHANCEMENT WITH H850 TEMPS DOWN TO NEAR OR JUST
BELOW ZERO C.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 747 AM EDT TUE SEP 30 2014

EXTENSIVE LOW CLOUDS ARE IN PLACE ACROSS LOWER MICHIGAN IN THE
WAKE OF A COLD FRONTAL PASSAGE YESTERDAY EVENING. EXPECTING AT
BEST MVFR CONDITIONS TO PERSIST FOR THE BULK OF THE TAF PERIOD
(TODAY AND TONIGHT). IFR CEILINGS ARE IN PLACE AT 12Z ACROSS MUCH
OF THE AREA...BUT EXPECT THESE TO LIFT TO MVFR LEVELS THROUGH THE
COURSE OF THE MORNING. BY 15Z OR SO...ANTICIPATING THE CEILINGS
BELOW 1000FT TO LIFT INTO THE 1000-2000FT LAYER. CEILINGS WILL
LIKELY LIFT INTO THE 2000-3000FT LAYER LATER THIS AFTERNOON AND
REMAIN THERE THROUGH THE NIGHT. THERE MAY BE SOME BREAKS IN THE
OVERCAST TONIGHT...BUT SIDING TOWARDS THE PESSIMISTIC SIDE OF
THINGS GIVEN THE TIME OF YEAR AND THE PATTERN.

&&

.MARINE...
ISSUED AT 1104 AM EDT TUE SEP 30 2014

WINDS HAVE BEEN SLOWLY DIMINISHING THIS MORNING AND ARE ALSO
ALREADY TURNING TO THE NNE. AS A RESULT AREAS FROM PENTWATER TO
SOUTH HAVEN ARE BECOMING INCREASINGLY SHELTER FROM THE BRUNT OF
THE WIND. WAVES ARE ALREADY DOWN TO 3 FEET AT PORT SHELDON AS OF 11
AM. WILL CONTINUE THE ADVISORY HERE...BUT BRING THE ENDING TIME UP
TO 3 PM. AREAS NORTH OF PENTWATER AND SOUTH OF SOUTH HAVEN WILL
REMAIN ROUGHER THROUGHOUT THE DAY...SO WILL MAINTAIN THE SCA
THROUGH 8 PM THERE.

&&

.HYDROLOGY...
ISSUED AT 335 AM EDT TUE SEP 30 2014

PRECIPITATION WAS ABOUT AS EXPECTED WITH AMOUNTS RANGING FROM TRACE
VALUES TO AS MUCH AS A COUPLE TENTHS OF AN INCH. THE RAIN IS
PRESSING SOUTH OF THE AREA CURRENTLY AND SHOULD BE SOUTH OF THE
FORECAST AREA BY 12Z. THE LIGHT PRECIPITATION WILL NOT AFFECT RIVER
LEVELS MUCH. SO NO HYDRO CONCERNS AT PRESENT OR INTO WEDNESDAY
EITHER.

THE NEXT CHANCE FOR RAIN COMES WITH A FRONTAL BOUNDARY THAT
TRAVERSES THE REGION THURSDAY AND THURSDAY NIGHT. PRECIPITABLE WATER
VALUES RISE TO IN EXCESS OF 1.50 INCHES WITH MAX VALUES NEAR TOWARDS
1.75 INCHES. MOISTURE WILL BE STREAMING NORTHWARD OFF THE GULF AND A
WIDESPREAD RAINFALL OF AT LEAST 0.50 TO 1.00 INCHES IS EXPECTED.
THIS TYPE OF PRECIP WILL BE ABLE TO BE HANDLED BY AREA RIVERS AS
THEY ARE QUITE LOW AT PRESENT GIVEN THE RECENT DRY WEATHER.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR LMZ844-849.

     SMALL CRAFT ADVISORY UNTIL 3 PM EDT THIS AFTERNOON FOR
     LMZ845>848.

&&

$$

SYNOPSIS...DUKE
SHORT TERM...DUKE
LONG TERM...NJJ
AVIATION...DUKE
HYDROLOGY...DUKE
MARINE...JK






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