Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 201619
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1220 PM EDT MON APR 20 2015

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 330 AM EDT MON APR 20 2015

A CHILLY WEEK IS DEVELOPING AS LOW PRESSURE HAS MOVED OVER THE GREAT
LAKES. COOLER AIR WILL FLOW INTO WEST MICHIGAN BEHIND THE LOW. RAIN
SHOWERS MAY MIX WITH WET SNOW AT TIMES. MINOR ACCUMULATIONS ARE
POSSIBLE TUESDAY NIGHT NEAR US 10. HIGHS WILL BE IN THE MID 40S TO
MID 50S THROUGH THE END OF THE WEEK.

&&

.UPDATE...
ISSUED AT 1152 AM EDT MON APR 20 2015

OVERALL THE ONGOING FORECAST LOOKS FINE. I DID SOME MINOR
ADJUSTMENTS TO THE POPS BASED ON RECENT RADAR TRENDS AND
CONSIDERING THERE IS ANOTHER SHORTWAVE THAT MOVES INTO THE AREA
THIS EVENING TO HELP INCREASE THE SHOWER ACTIVITY. IT WILL BE
BREEZY TODAY THROUGH TUESDAY BUT I DO NOT BELIEVE IT WILL BE WINDY
ENOUGH FOR A WIND ADVISORY.

&&

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 330 AM EDT MON APR 20 2015

FORECAST CONCERNS CONTINUE TO DEAL WITH THE EVOLUTION OF THE LOW
MOVING ACROSS LOWER MICHIGAN. OVERALL...THE FORECAST IS UNFOLDING AS
EXPECTED.

LOCAL AND REGIONAL RADAR SHOWS RAIN SHOWERS MOVING NORTH ACROSS THE
CWA. OVERALL COVERAGE THOUGH IS BEGINNING TO DECREASE SOUTH OF THE
MI/IN BORDER AS THE LOW MOVES NORTH. SREF SHOWS THAT PCPN WILL FILL
BACK IN ACROSS THE SOUTHERN CWA LATER THIS MORNING AS A SHORT WAVE
ALOFT PIVOTS TOWARD LOWER MICHIGAN BEFORE DIMINISHING AGAIN LATER
THIS AFTERNOON. AT THIS POINT THE HEAVIEST AND STEADIEST RAIN
APPEARS TO BE WINDING DOWN. WHAT WE/LL BE LEFT WITH IS SCATTERED TO
NUMEROUS SHOWERS TODAY AND A BIT LESS TONIGHT.

TUESDAY THE CORE OF THE UPPER LOW MOVES OVERHEAD. LOOK FOR PCPN TO
INCREASE IN COVERAGE AGAIN AS INSTABILITY ALOFT INCREASES A BIT DUE
STEEPENING LAPSE RATES COURTESY OF H5 TEMPS NEAR -30C MOVING OVER
THE CWA. THE COLDER AIR WILL REMAIN WITH US THROUGH TUESDAY NIGHT.
THAT/S WHEN WE COULD SEE SOME WET SNOW MIX IN WITH THE RAIN SHOWERS.
MINOR...LESS THAN AN INCH...ACCUMS SEEM POSSIBLE IN OSCEOLA/CLARE
COUNTIES TUESDAY NIGHT. THE UPPER LOW WILL BE VERY SLOW TO MOVE OUT
AND WE/LL SEE THE COOL SHOWERY PCPN CONTINUE WEDNESDAY AS A COUPLE
OF SHORT WAVES ROTATE AROUND THE UPPER LOW AND ACROSS LOWER MICHIGAN.

HIGHS WILL BE BELOW NORMAL THROUGH THE SHORT TERM RANGING FROM THE
MID 40S TO MID 50S.

.LONG TERM...(WEDNESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 330 AM EDT MON APR 20 2015

THE COLD UPPER LOW REMAINS OVERHEAD THROUGH THURSDAY THEN MOVES INTO
NEW ENGLAND/SRN QUEBEC FOR THE WEEKEND. A SLIGHT CHANCE OF LIGHT
RAIN AND SNOW SHOWERS WILL LINGER THROUGH ABOUT THURSDAY NIGHT WHILE
H8 TEMPS AROUND -7C AND CYCLONIC FLOW ARE STILL PRESENT... OTHERWISE
DRY BUT CHILLY WEATHER IS EXPECTED WITH SFC HIGH PRESSURE MOVING IN.

THIS WEEKEND WE WILL STILL BE ON THE WRN PERIPHERY OF THE BROAD NEW
ENGLAND UPPER LOW. THE CONFLUENT/SHEARING UPPER LEVEL FLOW OVERHEAD
ASSOCIATED WITH THIS FEATURE HELPS TO FEND OFF RAIN ASSOCIATED WITH
A SYSTEM MOVING EAST FROM THE CENTRAL PLAINS. GUIDANCE SHOWS QPF
REMAINING TO OUR SOUTH WITH WEAK SURFACE RIDGING PREVAILING OVER THE
WEEKEND. TEMPERATURES WILL RECOVER A BIT AND HIGHS IN THE 50S ARE
EXPECTED SATURDAY AND SUNDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY)
ISSUED AT 1220 PM EDT MON APR 20 2015

MAINLY IFR/MVFR CONDITIONS WILL CONTINUE THROUGH MID TO LATE
AFTERNOON DUE TO LOW CIGS AND SCATTERED SHOWERS AND PATCHY FOG
BEFORE GRADUALLY IMPROVING TO VFR THIS EVENING AND OVERNIGHT.

IT WILL BE BREEZY THIS AFTERNOON WITH SW WINDS OF 15 TO 25 KTS WITH
GUSTS TO AROUND 30 KTS. SOUTHWEST TO WEST WINDS WILL STAY UP AROUND
15 TO 25 KTS OVERNIGHT AND THEN VEER TO THE WEST AND INCREASE TO 20
TO 25 KTS WITH GUSTS TO AROUND 30 KTS BY MID TO LATE TUESDAY MORNING.

SCATTERED LIGHT RAIN SHOWERS WILL LINGER OVERNIGHT AND THEN BECOME
MORE PREVALENT ON TUESDAY. MAINLY VFR CONDITIONS ARE ANTICIPATED
TUESDAY ALTHOUGH SOME PATCHY MVFR IS POSSIBLE DUE TO LOWER CIGS AND
HEAVIER SHOWERS.

&&

.MARINE...
ISSUED AT 752 AM EDT MON APR 20 2015

ADDED AREAS OF DENSE FOG TO THE NEARSHORE FORECAST TODAY. DESPITE
GOOD MIXING... DEW POINTS IN THE 40S OVER THE COLD LAKE WATERS IS
PRODUCING FOG PER POST SUNRISE WEB CAMS AT MKG/HOLLAND.

LEFT THE SMALL CRAFT ADVISORY AS IS SOUTH OF WHITEHALL. AS THE LOW
MOVES FARTHER AWAY...WINDS WILL INCREASE FROM THE SOUTHWEST AND
WAVES WILL ALSO RESPOND. A SMALL CRAFT ADVISORY MAY ALSO BE NEEDED
NORTH OF WHITEHALL TONIGHT.

&&

.HYDROLOGY...
ISSUED AT 1156 AM EDT MON APR 20 2015

WIDESPREAD RAINFALL THROUGH 8 AM THIS MORNING PRODUCED 0.50 TO 0.75
INCHES ACROSS MOST OF THE GRAND AND MUSKEGON RIVER BASINS. FURTHER
SOUTH ACROSS THE KALAMAZOO RIVER BASIN...RAINFALL AMOUNTS WERE
HIGHER IN THE 0.75 TO 1.00 INCH RANGE. AS EXPECTED...GRADUAL RIVER
RISES HAVE BEGUN ON MOST AREA RIVERS. GENERAL HYDRO THINKING HAS NOT
CHANGED MUCH...MOSTLY WITHIN BANK RISES ARE EXPECTED. A FEW SITES
COULD EXCEED BANKFULL. BUT WITH RAIN TODAY AND TONIGHT BEING OF THE
SCATTERED AND LIGHT VARIETY...SIGNIFICANT FLOODING IS NOT EXPECTED.

FORECAST RAINFALL TODAY AND TONIGHT IS IN THE 0.10 TO 0.25 INCH
RANGE. EVEN LIGHTER PRECIP AMOUNTS ARE EXPECTED TUESDAY
INTO WEDNESDAY. A SLIGHT CHANCE OF LIGHT RAIN AND SNOW WILL LINGER
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT. BUT MAINLY DRY AND CHILLY
WEATHER IS EXPECTED TOWARD THE END OF THE WEEK.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 6 PM EDT TUESDAY FOR LMZ844>847.

&&

$$

UPDATE...WDM
SYNOPSIS...04
SHORT TERM...04
LONG TERM...MEADE
AVIATION...LAURENS
HYDROLOGY...EBW
MARINE...04







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