598  
FXUS63 KGRR 250234  
AFDGRR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND RAPIDS MI  
1034 PM EDT SUN MAY 24 2015  
 
LATEST UPDATE...  
UPDATE  
   
SYNOPSIS
 
 
ISSUED AT 329 PM EDT SUN MAY 24 2015  
 
WE WILL HAVE PERIODS OF RAIN ACROSS THE AREA TONIGHT INTO TUESDAY  
NIGHT. THE MOST WIDESPREAD RAINS SHOULD COME TONIGHT THROUGH MONDAY  
MORNING. THEN SHOWERS SHOULD BECOME SCATTERED MONDAY AFTERNOON AND  
NIGHT. ANOTHER ROUND OF STEADY RAINS IS EXPECTED TUESDAY AND  
TUESDAY NIGHT. A FEW RUMBLES OF THUNDER WILL ALSO BE POSSIBLE.  
TEMPERATURES WILL REMAIN MILD WITH HIGHS MAINLY IN THE 70S AND LOWS  
FROM 60 TO 65.  
 
THE AREA SHOULD DRY OUT MID WEEK...THEN ANOTHER PERIOD OF SHOWERS  
AND STORMS WILL BE POSSIBLE THURSDAY NIGHT THROUGH FRIDAY NIGHT.  
DAYTIME TEMPERATURE SHOULD REMAIN MILD...MAINLY 75 TO 80.  
 

 
   
UPDATE
 
 
ISSUED AT 1034 PM EDT SUN MAY 24 2015  
 
MAINTAINED SHOWERS IN THE FORECAST TONIGHT WITH ONLY A CHANCE OF  
THUNDERSTORMS. HRRR MODEL RUNS CONTINUE TO INDICATE SHOWERS  
GRADUALLY TAPERING OFF WITH LITTLE IN THE WAY OF THUNDERSTORM  
ACTIVITY. THE NOTION OF LIMITED CONVECTIVE ACTIVITY IS BACKED BY  
MODEL DATA INDICATING ONLY WEAK INSTABILITY TONIGHT DESPITE A  
FORMIDABLE LOW LEVEL JET OF 40 KNOTS AND STRONG 850MB MOISTURE  
TRANSPORT.  
 
HAVE 60-80 PCT CHANCES FOR SHOWERS ACROSS CENTRAL LOWER TAPERING  
TO 30-40 PCT CHANCES TOWARD INTERSTATE 94. DEEP LAYER WINDS ARE  
OUT OF THE SOUTH-SOUTHWEST TONIGHT WHICH WILL TEND TO KEEP THE  
PRECIPITATION TO THE WEST OF THE GRR FORECAST AREAS. THE NORTHWEST  
CWA UP TOWARDS LUDINGTON STANDS THE BEST CHANCES FOR SHOWERS AND  
AN EMBEDDED STORM. THE JACKSON AREA COULD BE DRY MOST OF THE  
NIGHT.  
 
TEMPERATURES WILL BE MILD IN THE 60S FOR THE MOST PART TONIGHT AS  
A WARM FRONT WILL BE LIFTING NORTH THROUGH THE AREA. WINDS WILL  
GRADUALLY BE PICKING UP TONIGHT IN RESPONSE TO A HIGH OFF THE EAST  
COAST AND A LOW TRACKING THROUGH THE WESTERN GREAT LAKES. IT LOOKS  
TO BECOME WINDY ON MEMORIAL DAY ESPECIALLY DURING THE MIDDAY AND  
AFTERNOON HOURS.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH TUESDAY NIGHT)  
ISSUED AT 329 PM EDT SUN MAY 24 2015  
 
WILL HAVE LIKELY TO CATEGORICAL POPS ACROSS THE CWA TONIGHT INTO  
MONDAY. THEN WE WILL GET WITHIN A DRY SLOT MONDAY AFTERNOON WITH  
SOME SUNSHINE DEVELOPING. ANOTHER SURGE OF RAIN...POSSIBLY HEAVY...  
MOVES IN TOWARD MID DAY TUESDAY AND LINGERS INTO TUESDAY NIGHT.  
 
AN AREA OF UPPER DIVERGENCE WAS MOVING INTO THE CWA THIS AFTERNOON  
AS WE ARE IN THE RIGHT ENTRANCE REGION OF THE UPPER JET. THIS WILL  
LINGER OVER THE REGION THROUGH 06Z BEFORE EXITING NE. THEREFORE WITH  
INCREASING MOISTURE AND LIFT EXPECT HIGH RAIN CHANCES EVERYWHERE.  
THE BEST MOISTURE POOLS OVER THE NORTHERN CWA DUE TO THE ISENTROPIC  
LIFT FROM THIS AFTERNOON. SOME AREAS MAY SEE OVER A HALF INCH OF  
RAIN NEAR HIGHWAY 10 TONIGHT. MEANWHILE THE I-94 CORRIDOR SHOULD  
ONLY SEE AROUND A TENTH OF AN INCH. THERE MAY BE A FEW EMBEDDED  
STORMS.  
 
THE WARM FRONT SWINGS THROUGH DURING THE FIRST HALF OF MONDAY. THIS  
WILL KEEP THE SHOWERS AND STORMS GOING. HOWEVER DRIER AIR ARRIVES  
BEHIND THE FRONT AND THE SHOWERS AND STORMS WILL BE REDUCED TO  
ISOLATED FOR THE AFTERNOON. WE SHOULD BREAK OUT INTO SOME SUNSHINE  
THROUGH THE AFTERNOON AND EVENING. THIS MAINLY DRY WARM SECTOR  
SHOULD CONTINUE OVER SOUTHWEST MI MONDAY NIGHT.  
 
THE FRONT STALLS ACROSS NORTHERN LOWER AND ANOTHER WAVE OF LOW  
PRESSURE MOVES ALONG IT WILL BRING MORE RAIN. PRECIPITABLE WATER  
VALUES CLIMB WHICH MAY LEAD TO AREAS OF HEAVY RAIN TUESDAY AFTERNOON  
AND EVENING. RAMPED POPS TO CATEGORICAL FOR TUESDAY AFTERNOON.  
 
OVERALL...MOST AREAS SHOULD SEE AROUND AN INCH OF RAIN WITH TONIGHT  
THROUGH TUESDAY NIGHT. BUT THERE IS THE THREAT OF LOCALIZED HEAVIER  
RAINS.  
   
LONG TERM
 
(WEDNESDAY THROUGH SUNDAY)  
ISSUED AT 329 PM EDT SUN MAY 24 2015  
 
AFTER TUESDAY NIGHT RAIN EVENT A WEAK SURFACE HIGH PRESSURE AREA  
WITH SHORTWAVE RIDGING ALOFT BUILD OVERHEAD WED AFTERNOON INTO  
THURSDAY. NEXT CHANCE OF RAINFALL STILL ON TRACK FOR FRIDAY INTO  
SATURDAY AS ANOTHER FRONT PUSHES THROUGH THE REGION. LATEST NWP  
TRENDING STRONGER WITH NORTHERN STREAM WHICH RESULTS IN A MORE  
PROGRESSIVE SYSTEM WITH LESS HEAVY RAIN POTENTIAL AND A GOOD PUSH OF  
SEASONABLY COOL CANADIAN AIR BY SUNDAY.  
 
THERE ARE SOME DIFFERENCES BETWEEN ECMWF AND GFS ON THE EVOLUTION  
AND EVENTUAL SHEARING OUT OF THE WEST U.S. SOUTHERN STREAM TROUGH  
BUT THEY HAVE MORE IN COMMON THAN NOT SO CONFIDENCE IS A BIT HIGHER  
TODAY THAN YESTERDAY. EITHER SOLUTION WOULD RESULT IN A ROUND OF  
FRONTAL THUNDERSTORMS WITH SOME SEVERE POTENTIAL FRIDAY AFTERNOON  
(GFS) OR ON SATURDAY (ECMWF). OVERALL ECMWF IS A BIT SLOWER WITH  
MORE POTENTIAL OF HEAVY RAINFALL. AS MENTIONED PREVIOUSLY...THERE  
WILL BE GOOD MOISTURE ADVECTION AHEAD OF THE FRONT WITH PWATS ABOVE  
1.5 INCHES.  
 
SEVERE WEATHER WISE...SHEAR LOOKS TO BE A LIMITING FACTOR AT THIS  
TIME WITH OVERALL RELATIVELY WEAK MID LEVEL FLOW AND A  
UNIDIRECTIONAL PROFILE OVERALL. CAPE VALUES ARE A BIT BETTER WITH  
500 TO 1500 J/KG DEPENDING ON AFTERNOON VERSUS MORNING FRONTAL  
PASSAGE.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)  
ISSUED AT 821 PM EDT SUN MAY 24 2015  
 
MAIN AVIATION ITEM FOR THE NEXT 24 HOURS WILL BE STRENGTHENING  
WINDS. WINDS WILL GRADUALLY INCREASE TONIGHT BUT REMAIN IN THE 10  
TO 20 KNOT RANGE. WINDY CONDITIONS ARE EXPECTED ON SUNDAY WITH  
SOUTHWEST WINDS OF 15-30 KNOTS DURING THE AFTERNOON. HIGHER GUSTS  
ARE POSSIBLE. A CROSS WIND WILL BE PRESENT ON EAST/WEST RUNWAYS.  
 
CEILINGS WILL GRADUALLY LOWER TONIGHT WITH MVFR CEILINGS  
DEVELOPING AT KMKG AND KGRR. SOME LIGHT FOG WILL LIKELY BRING MVFR  
CONDITIONS TO ALL AREAS OVERNIGHT. THE MVFR CEILINGS WILL PERSIST  
THROUGH THE MORNING HOURS AT KMKG AND KGRR WITH ALL AREAS BECOMING  
VFR IN THE AFTERNOON AS THE CEILINGS AND LIGHT FOG LIFT.  
 
RAIN WILL BE MOST PREVALENT NORTH OF THE TAF SITES IN THE 00Z TO  
06Z TIME FRAME THIS EVENING.  
 

 
   
MARINE
 
 
ISSUED AT 329 PM EDT SUN MAY 24 2015  
 
WILL GET AN ADVANCED NOTICE AND ISSUE MARINE HEADLINES FOR MEMORIAL  
DAY. SOUTH WINDS WILL RAMP UP LATE TONIGHT INTO MONDAY AND WAVES  
WILL BUILD BY MID MORNING MONDAY. WILL ALSO ISSUE A BEACH HAZARDS  
STATEMENT FOR ANY WILLING TO GO OUT AND SWIM IN MID 40 DEGREE WATER  
TEMPS.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 204 PM EDT SUN MAY 24 2015  
 
THREE MAIN ROUNDS OF RAIN ARE FORECAST FOR SOUTHWEST LOWER MICHIGAN  
THROUGH NEXT WEEKEND...THE FIRST OF WHICH IS ARRIVING NOW. RAINFALL  
TOTALS OF UP TO HALF AN INCH ARE POSSIBLE ACROSS CENTRAL LOWER  
MICHIGAN THROUGH MONDAY AFTERNOON...MAINLY OVER THE UPPER MUSKEGON  
BASIN AND PERE MARQUETTE BASINS. MONDAY AFTERNOON THROUGH MONDAY  
NIGHT LOOKS FAIRLY DRY. A SECOND ROUND OF SHOWERS AND A FEW STORMS  
WILL BE POSSIBLE TUESDAY AFTERNOON THROUGH TUESDAY NIGHT.  
 
THE BIGGEST HYDRO CONCERN COULD BE THE THIRD ROUND ON FRIDAY AND  
SATURDAY. A MORE UNSTABLE AND INCREASINGLY HUMID AIRMASS WILL BE  
MORE CONDUCIVE TO STRONGER THUNDERSTORMS CAPABLE OF HEAVY RAINFALL  
FRIDAY INTO SATURDAY. THE ECMWF EPS...GEM...AND GFS AGREE THAT 2 TO  
3 INCHES OF WIDESPREAD RAINFALL IS POSSIBLE THROUGH SUNDAY...WITH  
HIGHER AMOUNTS POSSIBLE IN STRONG THUNDERSTORMS. RIVER RISES ARE  
EXPECTED THIS WEEK AND ESPECIALLY NEXT WEEKEND. THE MAIN IMMEDIATE  
THREAT WILL BE MINOR NUISANCE FLOODING MIDWEEK WITH THE POSSIBILITY  
OF HEAVY RAINFALL TUESDAY AFTERNOON THROUGH TUESDAY NIGHT. THE  
FLOODING RISK IS HIGHER NEXT WEEKEND...ESPECIALLY IN URBAN AREAS AND  
ON SMALLER STREAMS.  
 

 
   
GRR WATCHES/WARNINGS/ADVISORIES
 
 
MI...BEACH HAZARDS STATEMENT FROM 9 AM EDT MONDAY THROUGH LATE MONDAY  
NIGHT FOR MIZ056-064-071.  
 
BEACH HAZARDS STATEMENT FROM 9 AM EDT MONDAY THROUGH TUESDAY  
MORNING FOR MIZ037-043-050.  
 
LM...SMALL CRAFT ADVISORY FROM 9 AM MONDAY TO 8 AM EDT TUESDAY FOR  
LMZ847>849.  
 
SMALL CRAFT ADVISORY FROM 9 AM MONDAY TO 1 AM EDT TUESDAY FOR  
LMZ844>846.  
 

 
 

 
 
UPDATE...DUKE  
SYNOPSIS...JK  
SHORT TERM...JK  
LONG TERM...COBB  
AVIATION...DUKE  
HYDROLOGY...EBW  
MARINE...JK  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab MI Page
The Nexlab IN Page Main Text Page