Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 240000
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
800 PM EDT SAT MAY 23 2015

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 328 PM EDT SAT MAY 23 2015

AFTER A QUIET NIGHT...SCATTERED SHOWERS AND PERHAPS A FEW
THUNDERSTORMS WILL ARRIVE ON SUNDAY.  LAKE SHORE AREAS COULD SEE A
FEW SHOWERS AS EARLY AS SUNDAY MORNING...WITH THE REST OF THE AREA
SEEING SCATTERED SHOWERS BY AFTERNOON.  A BETTER CHANCE FOR
WIDESPREAD RAINS AND A FEW STORMS MOVES IN SUNDAY NIGHT AND MEMORIAL
DAY.  TEMPERATURES WILL REMAIN MILD WITH DAYTIME HIGHS IN THE UPPER
70S TO AROUND 80.

SCATTERED SHOWERS AND STORMS APPEAR TO REMAIN IN THE AREA WEDNESDAY
AND THURSDAY BEFORE WE FINALLY DRY OUT.  DAYTIME TEMPERATURES SHOULD
LARGELY BE IN THE 70S MUCH OF NEXT WEEK.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 328 PM EDT SAT MAY 23 2015

BELIEVE IT WILL REMAIN DRY TONIGHT...THEN PCPN CHANCES INCREASE LATE
SUNDAY...AND PEAK SUNDAY NIGHT AND MEMORIAL DAY.

HAVE KEPT TONIGHT DRY DESPITE SOME DECENT MOISTURE ADVECTION MOVING
INTO SW MI.  WE COULD SEE AN ISOLATED SHOWER...BUT BELIEVE THE
MOISTURE DEPTH REMAINS SHALLOW ENOUGH TO NOT INCLUDE THIS OUTSIDE
CHANCE IN THE FORECAST.  ANOTHER THING WORKING AGAINST ANY PCPN IS
THE UPPER RIDGE STAYS OVERHEAD THROUGH THE NIGHT.

MORE CLOUDS EXPECTED SUNDAY AS THE MOISTURE ADVECTION CONTINUES AS
THE GULF OPENS UP TO THE GREAT LAKES.  THE UPPER RIDGE ONLY SLOW
DRIFTS OFF TO THE EAST...BUT A WARM FRONT MOVES NORTH TOWARD THE
MI/IN BORDER BY THE END OF THE DAY.  THIS WILL GRADUALLY PRODUCE
MORE ISENTROPIC LIFT THROUGH THE DAY AND EXPECT SCATTERED SHOWERS TO
DEVELOP LATE MORNING INTO THE AFTERNOON.  SHOULD BE ENOUGH SURFACE
BASED INSTABILITY...WITH DEW POINTS RISING INTO THE MID 50S TO
MENTION SOME THUNDER.

THE WARM FRONT CONTINUES TO LIFT NORTH INTO THE CWA SUNDAY NIGHT.
THIS ALLOWS EVEN DEEPER MOISTURE TO ARRIVE.  MOST AREAS SHOULD SEE
MORE WIDESPREAD RAINS...WITH THE NORTHERN CWA HAVING THE HIGHEST
POPS.  THUNDER SHOULD REMAIN WIDELY SCATTERED AS THE INSTABILITY
REMAINS LOW.  MEMORIAL DAY SHOULD TURN OUT TO BE THE WETTEST DAY AS
THE DEEP MOISTURE REMAINS ALONG WITH PERIODS FAVORABLE ISENTROPIC
LIFT MOVING ALONG THE WARM FRONT.  I RAISED POPS BUT JET DYNAMICS
REMAIN UNFAVORABLE FOR ANY SEVERE STORMS.  WE MAY GET INTO A DRY
SLOT BY LATE IN THE DAY WHEN THE PCPN COULD MOVE OUT AND WE SEE SOME
SUNSHINE AS THE WARM FRONT LIFTS INTO NORTHERN LOWER.

REMOVED POPS FOR AREAS NORTH OF I-96 MONDAY NIGHT.  HOWEVER KEPT
POPS FOR THE SOUTHERN CWA AS ANOTHER SURGE OF MOISTURE FROM THE
SOUTH IS SUGGESTED BY THE MODELS LATE.

.LONG TERM...(TUESDAY THROUGH SATURDAY) ISSUED AT 328 PM EDT SAT MAY
23 2015

NEXT WEEK WILL BE A WARM AND SOMEWHAT HUMID WEEK WITH A CHANCE OF A
SOAKING RAIN TUESDAY NIGHT AND AGAIN TOWARDS NEXT SATURDAY. MOST
SIGNIFICANT CONCERN IS CONTINUED CONSENSUS OF ECMWF...GFS...AND
FIM IN FORECASTING 2 - 3 INCH RAINFALL AMOUNTS OVER THE NEXT 10
DAYS.

TUESDAY NIGHT A SIGNIFICANT BUT WEAKENING SHORTWAVE EJECTS FROM WEST
COAST U.S. TROUGH. SLOW MOVING FRONTAL SYSTEM ACTS AS TRIGGER FOR
LOW-MOD CAPE FED SHOWER / THUNDERSTORM ACTIVITY. PLENTY OF MOISTURE
ADVECTION TO WORK WITH SO WOULD BE A GOOD BET TO SEE AT LEAST SOME
LOCALIZED HEAVY RAINFALL ISOLATED FLOODING OF URBAN AREAS / SMALL
STREAMS.

FRIDAY - SATURDAY FEATURES A MORE INTERESTING LARGE SCALE
FRONTOGENETICAL SCENARIO WITH COOL AIR BUILDING ACROSS NORTHERN
LAKES ON HEAL OF NRN STREAM SHORTWAVE WHILE ANOTHER SURGE OF
MOISTURE ASSOCIATED WITH ANOTHER EJECTING SHORTWAVE OUT OF SRN
STREAM WEST U.S. TROUGH HEADS TOWARDS SOUTHERN LAKE MICHIGAN. THIS
COULD BE A GOOD SETUP FOR WIDESPREAD EXCESSIVE RAINFALL...BUT TIMING
IS EVERYTHING AND THERE IS PLENTY OF TIME FOR ALTERNATIVE EVOLUTIONS
AT THIS POINT.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 758 PM EDT SAT MAY 23 2015

VFR WEATHER IS EXPECTED THE NEXT 24 HOURS. MID AND HIGH CLOUDS
WILL GRADUALLY STREAM INTO THE AREA FROM THE WEST...ESPECIALLY
LATE TONIGHT AND ON SUNDAY. BASES TONIGHT WILL BE ABOVE 10000FT.
CEILINGS WILL LOWER INTO THE 5000-10000FT RANGE ON SUNDAY. CHANCES
FOR SHOWERS WILL INCREASE SUNDAY AFTERNOON AND EVENING. AT THIS
POINT THINK THE THUNDER THREAT IS QUITE LOW AND LEFT THAT OUT OF
THE FORECAST. VCSH WORDING AFTER 18Z ON SUNDAY IS WHAT WE
CURRENTLY HAVE FORECAST. IF ANY THUNDER OCCURS IT WILL BE ISOLATED
AND AT THE I-94 TAF SITES TOWARDS EVENING SUNDAY.

&&

.MARINE...
ISSUED AT 328 PM EDT SAT MAY 23 2015

OTHER THAN THE LOW RISK FOR THUNDER RATHER NICE CONDITIONS ON THE
LAKE EXPECTED THROUGH SUNDAY.  HIGHER DEW POINTS ARRIVING BY SUNDAY
NIGHT INTO MONDAY WHICH SHOULD BEGIN TO PRODUCE AREAS OF FOG ON THE
LAKE THAT COULD BECOME LOCALLY DENSE.  SOUTHERLY WINDS SHOULD ALSO
KICK UP AND THE WAVES SHOULD BEGIN TO BUILD AROUND DAYBREAK MONDAY.
WE MAY NEED A SMALL CRAFT ADVISORY BY LATE MONDAY MORNING AS THE
WAVES SHOULD CONTINUE TO BUILD WITH THE PERSISTENT SOUTHERLY BREEZE.
THESE ROUGHER WAVES SHOULD SUBSIDE INTO MONDAY NIGHT WITH LESSENING
WINDS.


&&

.HYDROLOGY...
ISSUED AT 1225 PM EDT SAT MAY 23 2015

A VERY DRY AIRMASS IS IN PLACE OVER LOWER MI THIS AFTERNOON WITH
RH VALUES IN THE 20S. THAT WILL BEGIN TO CHANGE THIS EVENING INTO
TOMORROW AS MOISTURE IS ADVECTED INTO THE REGION. MULTIPLE ROUNDS
OF SHOWERS AND POSSIBLY SOME STORMS WILL BE POSSIBLE SUNDAY
AFTERNOON THROUGH THE COMING WEEK. RAIN WILL BE POSSIBLE EACH
DAY...WITH HIGHER CHANCES IN PARTICULAR SUNDAY AFTERNOON THROUGH
MONDAY MORNING AND ALSO TUESDAY AFTERNOON AND EVENING. TIMING
POTENTIAL PRECIP FROM MIDWEEK ON REMAINS DIFFICULT AT BEST.

OVERALL...WIDESPREAD RAINFALL OF 0.75 TO 2.00 INCHES IS POSSIBLE
THROUGH THURSDAY MORNING...WITH THE HIGHEST AMOUNTS FURTHER NORTH
OVER THE MUSKEGON AND PERE MARQUETTE BASINS. LESSER RAINFALL IS
EXPECTED OVER THE KALAMAZOO BASIN. RIVER LEVEL RISES ARE
EXPECTED...BUT FLOODING REMAINS UNCERTAIN. WIDESPREAD SIGNIFICANT
FLOODING APPEARS UNLIKELY DUE TO RECENT DRY WEATHER AND DECLINING
RIVER LEVELS...BUT LOCALIZED HEAVY RAINFALL AND FLOODING ARE POSSIBLE
FROM STRONGER THUNDERSTORMS.

&&

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

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...COBB
AVIATION...DUKE
HYDROLOGY...EBW
MARINE...JK



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