Small Craft Advisory 70, NWS Grand Rapids, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1046 AM EDT SAT SEP 14 2013

LATEST UPDATE...
MARINE

.SYNOPSIS...
ISSUED AT 330 AM EDT SAT SEP 14 2013

WE/LL SEE PLENTY OF SUNSHINE TODAY AND TEMPERATURES WILL BE A BIT
WARMER COMPARED TO FRIDAY. SHOWERS ARE EXPECTED SUNDAY AHEAD OF
ANOTHER COLD FRONT WHICH WILL BRIEFLY DECREASE TEMPERATURES BEFORE A
WARMUP BEGINS MONDAY. TEMPERATURES WILL BE NEAR 80 BY THURSDAY.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 330 AM EDT SAT SEP 14 2013

FORECAST CONCERNS DEAL WITH PCPN POTENTIAL SUNDAY.

SHORT RANGE MODELS HAVE COME INTO PRETTY GOOD AGREEMENT WITH REGARDS
TO A COLD FRONT APPROACHING THE CWA SUNDAY. AFTER SEEING ABUNDANT
SUNSHINE TODAY...CLOUDS WILL INCREASE TONIGHT AS SHOWERS MOVE TOWARD
LOWER MICHIGAN. PCPN SHOULD BEGIN AROUND 12Z IN THE NW CWA AND THEN
SPREAD SEWD THROUGH THE DAY. MODELS SHOW VERY LITTLE INSTABILITY DUE
TO A SUBSTANTIAL INVERSION ABV 800 MB. THUS WE/RE LOOKING AT
SHOWERS. RIGHT ENTRANCE REGION OF THE UPPER JET WILL LIKELY PLAY A
ROLE IN ENHANCING PCPN POTENTIAL. THUS SOME AREAS MAY SEE GREATER
THAN A QUARTER INCH OF RAIN. CLOUDS AND PCPN SHOULD HOLD TEMPS DOWN
IN THE MID 60S. MONDAY LOOKS DRY AS A LARGE HIGH BUILDS INTO THE
GREAT LAKES.

.LONG TERM...(MONDAY NIGHT THROUGH FRIDAY)
ISSUED AT 330 AM EDT SAT SEP 14 2013

A MORE ACTIVE WEATHER PATTERN SEEMS TO BE SHAPING UP FOR THE MIDDLE
TO END OF NEXT WEEK. AS I HAVE BEEN WRITING FOR SEVERAL DAYS NOW IT
SEEMS TO ME WED THROUGH FRIDAY ARE LIKELY TO BE A VERY WET PERIOD
FOR SOUTHWEST MICHIGAN. THIS INCLUDES SHOWERS AND THUNDERSTORMS.
THERE IS EVEN THE SUGGESTION OF A FALL LIKE...DEEPLY OCCLUDED STORM
TOWARD THE WEEKEND.

THE PHASING OF THREE RATHER LARGE STORMS...ONE OVER EXTREME
NORTHEAST RUSSIA...ONE IN THE GULF OF ALASKA AND THE OTHER OFF THE
CALIFORNIA COAST INTO ONE POWERFUL SYSTEM OVER THE GULF OF ALASKA BY
MONDAY EVENING WILL BUILD THE LARGE UPSTREAM UPPER RIDGE OVER
CENTRAL NORTH AMERICA AS FAR NORTH A LAKE WINNIPEG. THAT OF COURSE
DEEPENS THE DOWNSTREAM TROUGH (OVER THE EASTERN GREAT LAKE BY THEN).
OVER TIME THE POWERFUL SYSTEM IN THE GULF OF ALASKA KICKS OUT A
MAJOR SHORTWAVE THAT TRAVELS EAST IN THE UPPER FLOW BRINGS BACK THE
DEEP MOISTURE AND PRECIPITABLE WATERS MORE THAN DOUBLE NORMAL BY
WEDNESDAY. HOWEVER A SECOND WAVE IS KICKED OUT BY THIS SYSTEM AND
BOTH THE 00Z ECMWF AND GFS NOW FORM A CLOSED UPPER LOW WITH THAT
SECOND SYSTEM. THE GFS VERSION COMES OUT FARTHER NORTH AND QUICKER
IN THE THU/FRI TIME FRAME WHILE THE ECMWF VERSION OF IT IS MORE
FRI/SAT AND THAT IS FARTHER SOUTH... OVER MICHIGAN. SUFFICE TO SAY
WE WILL BE WET THROUGH THIS TIME PERIOD. POSSIBLY VERY WET.

TEMPERATURES WILL START OUT COLDER THAN NORMAL BUT WILL WARM TO WELL
ABOVE NORMAL BY WED/THU. IT MAY TURN COLD BY EARLY NEXT WEEKEND
BEHIND THE SECOND SYSTEM. SEEMS WRAP AROUND LAKE EFFECT RAIN SHOWERS
WOULD BE LIKELY BEHIND BOTH THE GFS AND ECMWF SYSTEMS... JUST A
QUESTION OF FRI OR SAT.  WE WILL HAVE TO WATCH HOW THIS PLAYS OUT IN
THE MODELS OVER THE NEXT FEW DAYS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 748 AM EDT SAT SEP 14 2013

EXPECT LIGHT SOUTH WINDS WITH NEARLY CLEAR SKIES MOST OF THE DAY.
TONIGHT EXPECT INCREASING HIGH CLOUDS BY 00Z THEN MID CLOUDS BY
04-06Z. ANY PRECIPITATION WILL BE AFTER 12Z SUNDAY. FLOW BECOMES
NORTH TO NORTHEAST BEHIND THE FRONT FOR SUNDAY NIGHT. THIS WILL
ACT TO KEEP THE WAVES AT POTENTIALLY HAZARDOUS LEVELS FOR SMALL CRAFT.

&&

.MARINE...
ISSUED AT 1042 AM EDT SAT SEP 14 2013

SOUTH TO SOUTHWEST FLOW WILL INCREASE AS WE GO THROUGH THE
AFTERNOON. THIS WILL ALLOW FOR BUILDING WAVES. OVERNIGHT VALUES
MAY REACH SMALL CRAFT ADVISORY CRITERIA FOR LITTLE AND BIG SABLE
POINTS. WILL ADDRESS THIS WITH THE AFTERNOON FORECAST.

&&

.HYDROLOGY...
ISSUED AT 330 AM EDT SAT SEP 14 2013

QPF NEAR A QUARTER IN IS POSSIBLE SUNDAY AS ANOTHER COLD FRONT MOVES
THROUGH. HEAVY RAINFALL NOT EXPECTED THOUGH AS INSTABILITY IS RATHER
LOW.

&&

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

SYNOPSIS...93
SHORT TERM...93
LONG TERM...WDM
AVIATION...WDM
HYDROLOGY...93
MARINE...MJS

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