Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 010337
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1137 PM EDT THU APR 30 2015

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 329 PM EDT THU APR 30 2015

HIGH PRESSURE WILL BRING FAIR WEATHER THE REMAINDER OF THE WEEK AND
INTO MUCH OF THE WEEKEND. TEMPERATURES WILL GRADUALLY MODERATE EACH
DAY...REACHING THE UPPER 60S ON FRIDAY AND THE LOWER 70S ON SATURDAY
AND SUNDAY. THE PATTERN LOOKS TO TURN WET LATE IN THE WEEKEND AND
EARLY NEXT WEEK AS A FRONTAL BOUNDARY WILL BE DRAPED ACROSS THE
REGION. SHOWERS AND STORMS ARE IN THE FORECAST FROM SUNDAY AFTERNOON
THROUGH WEDNESDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT)
ISSUED AT 329 PM EDT THU APR 30 2015

VERY LITTLE IN THE WAY OF SHORT TERM FORECAST ISSUES WITH HIGH
PRESSURE IN CONTROL OF THE WEATHER. THERE MAY BE A STRAY SHOWER THIS
EVENING TOWARD BATTLE CREEK AND JACKSON...BUT OTHERWISE EXPECTING
DRY WEATHER FROM TONIGHT THROUGH SATURDAY NIGHT. TEMPERATURES WILL
BE SLIGHTLY ABOVE SEASONAL NORMS FOR THIS TIME OF YEAR WHICH WILL BE
A CHANGE FROM WHERE WE HAVE BEEN OF LATE. OVERALL SKIES WILL BE
MOSTLY CLEAR TO PARTLY CLOUDY THROUGH THE PERIOD.

.LONG TERM...(SUNDAY THROUGH THURSDAY)
ISSUED AT 329 PM EDT THU APR 30 2015

ITS CONTINUING TO LOOK RATHER ACTIVE THROUGH THE LONG TERM PERIOD
WITH SHOWERS AND THUNDERSTORMS BEING THE MAIN FOCUS.

THE INITIAL ONSET OF PRECIPITATION IS LOOKING TO HOLD OFF RATHER
LATE IN THE WEEKEND. AS HAS BEEN THE CASE FOR THE LAST FEW
DAYS...THE GFS AND ECMWF HAVE THEIR DISAGREEMENTS WITH TIMING AND
PLACEMENT OF THE FRONTAL BOUNDARY THAT WILL ULTIMATELY BE
RESPONSIBLE FOR WET CONDITIONS. THE ECMWF IS QUITE PERSISTENT ON
PUSHING AN AREA OF LOW PRESSURE EAST OF THE HUDSON BAY. A WEAKER
DISTURBANCE DEVELOPS AND ROTATES AROUND THE MAIN LOW AND ATTEMPTS TO
PUSH COOLER AIR SOUTHWARD. THE GFS IS SLOWER AND FURTHER WEST WITH
THIS MAIN LOW AND KEEPS THE BOUNDARY FURTHER NORTH. THIS WOULD PLAY
A LARGE ROLE IN NOT ONLY PRECIPITATION AMOUNTS THROUGH THE AREA BUT
ALSO THE TEMPERATURE SPREAD FROM NORTH TO SOUTH. THE PERSISTENCE OF
THE ECMWF WOULD NORMALLY BE COMFORTING...BUT RECENT EVENTS HAVE
ACTUALLY BEEN WON OUT BY THE GFS. THEREFORE...THE CONFIDENCE ON THE
FRONTAL BOUNDARY PLACEMENT IS STILL RATHER LOW.

WHILE THE ECMWF IS LESS AMPLIFIED WITH THE UPPER LEVEL RIDGE...THE
GFS HAS A TROUGH OVER THE WEST...WHICH WOULD EXPLAIN THE REASONING
FOR THE NORTHWARD EXTEND OF THE FRONTAL BOUNDARY AND MORE AMPLIFIED
PATTERN.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1137 PM EDT THU APR 30 2015

AS I SUGGESTED WITH MY 00Z TAF SET...THE MID CLOUDS FROM THE UPPER
LOW WOULD LINGER FOR THE MORE EASTERN TAF SITES TILL AROUND 06Z
THEN SKIES WILL CLEAR EVEN THERE. I STILL BELIEVE THIS TO BE TRUE
AS THE TREND OF THE CLOUD SHIELD OF MID CLOUDS SINKING SOUTHWARD
CONTINUES. MAYBE IT MAY TAKE TILL 08Z AT JXN AND BTL ACTUALLY BUT
SKIES WILL CLEAR BY 09Z FOR SURE AT ALL TAF SITES. THERE IS NOT
ENOUGH LOW LEVEL RH IN THE MODEL SOUNDING FOR MORE THAN ISOLATED
CUMULUS CLOUDS FRIDAY AFTERNOON SO I DID NOT INCLUDE THEM IN THE
TAFS. I DID HOWEVER FEATURE THAT WIND SHIFT FOR THE LAKE BREEZE AT
THE MORE WESTERN TAF SITES (MKG AND GRR).

&&

.MARINE...
ISSUED AT 933 PM EDT THU APR 30 2015

ALLOWED THE SMALL CRAFT ADVISORY TO EXPIRE NORTH OF GRAND HAVEN.
MEANWHILE...SOUTH OF GRAND HAVEN TRENDS ARE DOWNWARD...WITH 4-5
FOOT WAVE AT THE PORT SHELDON BUOY AT 22Z...DOWN TO 3-4 FEET AT
THE LAST REPORT. WINDS REMAIN AROUND 15 KNOTS...SO THE TREND IS
DOWN THERE TOO. ALTHOUGH SOMEWHAT MARGINAL NOW...WE WILL LEAVE THE
SCA GOING THROUGH 3 AM FOR AREAS SOUTH OF GRAND HAVEN.

WINDS AND WAVES SHOULD BE FAIRLY TAME AFTER TONIGHT AS HIGH PRESSURE
BUILDS IN THE NEXT COUPLE DAYS.


&&

.HYDROLOGY...
ISSUED AT 139 PM EDT THU APR 30 2015

RIVERS ARE RUNNING NEAR TO BELOW NORMAL. NO ISSUES ARE EXPECTED
THROUGH THE WEEKEND. WE ARE MONITORING THE POTENTIAL FOR OVER AN
INCH OF RAINFALL DURING THE FIRST HALF OF NEXT WEEK. CONFIDENCE IS
CURRENTLY NOT HIGH ON WHERE THE AXIS OF HEAVIEST RAIN WILL BE. WITH
THE GREEN-UP UNDERWAY... PLANTS AND SOIL ARE ABLE TO ABSORB A
GREATER AMOUNT OF RAIN THAN EARLIER IN THE SPRING. THIS WILL BUFFER
RIVER RESPONSE TO SOME EXTENT.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 3 AM EDT FRIDAY FOR LMZ844>846.

&&

$$

SYNOPSIS...DUKE
SHORT TERM...DUKE
LONG TERM...JAM
AVIATION...WDM
HYDROLOGY...CAS
MARINE...JK





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