Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 061938
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
337 PM EDT MON JUL 6 2015

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

.SYNOPSIS...
ISSUED AT 337 PM EDT MON JUL 6 2015

SHOWERS AND EMBEDDED THUNDERSTORMS WILL MOVE THROUGH SOUTHWEST LOWER
MICHIGAN TONIGHT AND TUESDAY MORNING ALONG AND AHEAD OF A COLD
FRONT. RAINFALL AMOUNTS WILL VARY BETWEEN TWO TENTHS OF AN INCH TO
AROUND A HALF INCH IN SPOTS. THE RAIN WILL COME TO AN END TUESDAY
AFTERNOON AS THE COLD FRONT SLIPS OFF TO THE SOUTH AND EAST. DRY
WEATHER IS ON TAP FOR TUESDAY NIGHT INTO WEDNESDAY AS HIGH PRESSURE
TAKES CONTROL. COOLER WEATHER IS EXPECTED THE NEXT COUPLE OF DAYS AS
NORTH WINDS WILL KEEP HIGHS IN THE 70S.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 337 PM EDT MON JUL 6 2015

MAIN FOCUS IN THE SHORT TERM WAS ON CONVECTIVE TRENDS TONIGHT INTO
TUESDAY. CONVECTION ALLOWING MODELS ARE NOT BULLISH ON STORMS
TONIGHT. WE AGREE WITH THIS THINKING GIVEN BETTER INSTABILITY STAYS
TO THE SOUTH AND WEST OF LAKE MICHIGAN FOR THE MOST PART. IN
ADDITION...THE BETTER DYNAMICS ASSOCIATED WITH A STRONGER SHORTWAVE
MOVING ACROSS THE NORTHERN LAKES STAYS OFF TO THE NORTH OF THE
FORECAST AREA. WHAT IS GOING FOR CONVECTION TONIGHT IS A FAIRLY
STRONG LOW LEVEL JET VIA ALL THE MODELS AND MODEST 850MB MOISTURE
TRANSPORT. 0-6KM SHEAR LAGS THE FRONT HOWEVER WHICH SHOULD KEEP
STORMS SOMEWHAT DISORGANIZED. BOTTOM LINE WE ARE EXPECTING A SWATH
OF SHOWERS TO MOVE THROUGH THE REGION WITH EMBEDDED STORMS. SEVERE
CHANCES ARE QUITE LOW IN OUR OPINION. FEEL THREATS TONIGHT WOULD BE
LOCALLY HEAVY RAINS GIVEN HIGH PWAT AIR...SOME SMALL HAIL AND WIND
GUSTS TO POSSIBLY AROUND 50 MPH IN THE STRONGEST OF STORMS.

ON TUESDAY THE THREAT SHIFTS QUICKLY OFF TO THE EAST AS AN
INSTABILITY WILL BE MUTED BY OVERNIGHT CLOUDS AND RAIN. ANY THREAT
OF ORGANIZED STORMS TUESDAY SHOULD BE SOUTH AND EAST OF THE GRR
FORECAST AREA. CONDITIONS DRY OUT TUESDAY AFTERNOON AS THE FRONT
MOVES SOUTH.

HAVE RAIN CHANCES BACK IN THE FORECAST FOR WEDNESDAY NIGHT AS A WEAK
SHORTWAVE MOVES OUR DIRECTION OUT OF THE SOUTHERN STREAM. ALL THE
MODELS HAVE SOME SEMBLANCE OF A WAVE WITH A SURFACE LOW SPINNING UP
TOWARDS 12Z THURSDAY. MODELS DIFFER ON THE DEPTH OF BOTH THE UPPER
AND SURFACE FEATURES. HAVE PLAYED IT SOMEWHAT MIDDLE OF THE ROAD AT
THIS POINT WITH CHANCES POPS IN THE SOUTHERN HALF OF THE FORECAST
AREA.

.LONG TERM...(THURSDAY THROUGH MONDAY)
ISSUED AT 337 PM EDT MON JUL 6 2015

ECMWF/CANADIAN MODELS ARE IN AGREEMENT BRINGING WAVE THROUGH THE
SOUTHERN GREAT LAKES REGION THURSDAY...WITH HIGHEST PRECIPITATION
CHANCES OVER THE SOUTHERN HALF OF THE FORECAST AREA.

MID LEVEL FLOW TRANSITIONS FROM A HIGH OVER THE SOUTHEASTERN STATES
THURSDAY TO A LARGER HIGH OVER THE WESTERN UNITED STATES BY EARLY
NEXT WEEK.  SEVERAL WAVES WILL MOVE THROUGH THE NORTHWEST FLOW THAT
DEVELOPS OVER THE REGION AS A RESULT...BRINGING CHANCES OF SHOWERS
AND THUNDERSTORMS LATER SATURDAY THROUGH MONDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 129 PM EDT MON JUL 6 2015

A PLUME OF LOW LEVEL MOISTURE SPREAD INTO SOUTHWEST MICHIGAN LATE
THIS MORNING...BRIEFLY CAUSING MVFR CEILINGS AT KBTL. SATELLITE
AND MODEL DATA SHOW THIS AREA SCATTERING AS IT SPREADS EAST THIS
AFTERNOON...SO WILL MAINTAIN VFR CONDITIONS THROUGH EARLY
EVENING.

MODELS IN GOOD AGREEMENT BRINGING PRECIPITATION INTO THE WEST
MICHIGAN TAF SITES OVERNIGHT AHEAD OF COLD FRONT. LATEST MODEL
GUIDANCE THROWING SOME DOUBT INTO THE COVERAGE OF THE SHOWERS AND
THUNDERSTORMS OVERNIGHT. WILL MAINTAIN THE CURRENT THINKING AND
TRY TO NARROW DOWN THE TIMING SOMEWHAT.


&&

.MARINE...
ISSUED AT 337 PM EDT MON JUL 6 2015

MADE SOME ADJUSTMENTS TO THE GOING SMALL CRAFT ADVISORY AND BEACH
HAZARDS STATEMENT. FIRST ITEM IS THAT I EXTENDED THEM FURTHER INTO
TOMORROW EVENING...THROUGH 1100 PM. IT APPEARS THE NORTH FLOW WILL
BE STRONG TOMORROW BASED ON SOME OF THE HIGHER RESOLUTION GUIDANCE
AND THE WAVES SHOULD LAST FURTHER INTO THE EVENING. AT THIS POINT
COMFORTABLE WITH 1100 PM BUT COULD SEE THE NEED TO EXTEND FURTHER
INTO THE NIGHT...ESPECIALLY DOWN SOUTH. WE ALSO BUMPED BACK THE
START TIME OF THE SMALL CRAFT IN THE SOUTH TO OVERNIGHT TONIGHT.

SOUTHERLY FLOW IS CURRENTLY IN PLACE AHEAD OF THE COLD FRONT WITH
STRONGER WINDS OCCURRING NORTH OF MUSKEGON. 15-25 KNOT WINDS HAVE
BEEN COMMON THIS AFTERNOON AT MUSKEGON AND ESPECIALLY BIG SABLE
POINT AND MANISTEE. EXPECT THAT WAVES UP TOWARDS THE POINTS ARE
SOLIDLY IN THE 3-5 FOOT RANGE. THESE WAVES WILL SUBSIDE SOME TONIGHT
BEFORE RAMPING UP IN NORTH FLOW BEHIND THE FRONT LATE TONIGHT AND
TOMORROW MORNING. EXPECTING WINDS TO BECOME MORE UNIFORM AND AFFECT
ALL THE NEARSHORE ZONES WITH 15-25 KNOT WINDS WITH GUSTS POSSIBLY UP
TOWARDS 30 KNOTS. SO...SOLID 3-5 FOOTERS ON TUESDAY WITH THE
POTENTIAL FOR SOME 4-6 FOOT WAVES. WOULD NOT BE SURPRISED TO SEE 5-7
IN THE FAR SOUTH TUESDAY AFTERNOON/EVENING.

WINDS AND WAVES WILL SUBSIDE LATE TUESDAY NIGHT INTO WEDNESDAY AS
HIGH PRESSURE BUILDS IN. AREAS OF MARINE FOG CAN BE EXPECTED TONIGHT
AS THE HIGH DEW POINT AIR INTERACTS WITH A COOLER LAKE.

&&

.HYDROLOGY...
ISSUED AT 1119 AM EDT MON JUL 6 2015

NO SHORT TERM ISSUES ARE FORESEEN ON AREA RIVERS. LONG TERM
FORECASTS SPELL SOME CONCERN WITH HEAVIER RAINFALL THAT MAY COME
INTO THE PICTURE LATER THIS WEEK.

RIVERS ALL CONTINUE TO BE STABLE OR FALLING SLIGHTLY. CURRENT
LEVELS ARE A BIT HIGHER THAN NORMAL BY JULY STANDARDS DUE TO THE
HEAVIER RAINFALL EXPERIENCED IN JUNE. RAINFALL TONIGHT INTO
TUESDAY WILL GENERALLY BE ONE-HALF INCH OR LESS. WHILE LOCALIZED
AREAS COULD EXCEED THIS AMOUNT...WIDESPREAD HEAVY RAINFALL IS NOT
ANTICIPATED.

THE SECOND HALF OF THE WEEK BRINGS THE POSSIBILITY FOR MULTIPLE
WAVES OF RAINFALL ALONG A BOUNDARY THAT COULD SET UP SOMEWHERE
THROUGH THE GREAT LAKES REGION. CONFIDENCE IS LOW WITH EXPECTED
RAINFALL TOTALS...BUT CURRENT CONSENSUS WITH WPC GUIDANCE SUGGESTS
ONE TO TWO INCHES IS POSSIBLE RIGHT THROUGH NEXT WEEKEND...FROM
FRIDAY THROUGH MONDAY. FORECAST VARIABILITY WITH THE BOUNDARY WILL
REQUIRE A BIT MORE ATTENTION TO UPDATES THROUGH THE NEXT SEVERAL
DAYS.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...BEACH HAZARDS STATEMENT FROM 2 AM EDT TUESDAY THROUGH TUESDAY
     EVENING FOR MIZ056-064-071.

     BEACH HAZARDS STATEMENT THROUGH TUESDAY EVENING FOR MIZ037-043-
     050.

LM...SMALL CRAFT ADVISORY UNTIL 11 PM EDT TUESDAY FOR LMZ847>849.

     SMALL CRAFT ADVISORY FROM 2 AM TO 11 PM EDT TUESDAY FOR
     LMZ844>846.

&&

$$

SYNOPSIS...DUKE
SHORT TERM...DUKE
LONG TERM...MWS
AVIATION...MWS
HYDROLOGY...JAM
MARINE...DUKE


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