Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 271144
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
744 AM EDT MON APR 27 2015

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 330 AM EDT MON APR 27 2015

A HIGH PRESSURE RIDGE WILL REMAIN IN CONTROL OF THE WEATHER
PATTERN THROUGH THE UPCOMING WEEK AND PRODUCE FAIR WEATHER.
TEMPERATURES WILL BE SEASONABLY COOL EARLY THIS WEEK BUT WILL
UNDERGO A GRADUAL MODERATING TREND. TEMPERATURES SHOULD AVERAGE
SLIGHTLY ABOVE NORMAL BY THE WEEKEND.

&&

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 330 AM EDT MON APR 27 2015

HIGH PRESSURE WILL CONTINUE TO BRING FAIR AND SEASONABLY COOL WX
EARLY THIS WEEK. A COUPLE OF UPPER LEVEL DISTURBANCES DROPPING
DOWN FROM THE NORTH WILL BRING SOME CLOUD COVER LATER TODAY.
HOWEVER DRY WX SHOULD CONTINUE WITH A DRY AIRMASS IN PLACE AND ANY
LIGHT SCATTERED RAIN SHOWERS SHOULD STAY NE TO EAST OF OUR FCST
AREA.

SOME PATCHY FROST IS POSSIBLE DURING THE EARLY MORNING HOURS
TUESDAY WITH NEAR CALM TO CALM WINDS AND THE RIDGE IN PLACE. HIGH
PRESSURE WILL PRODUCE FAIR WX WITH A MIX OF SUN AND CLOUDS
TUESDAY.

UPPER LEVEL LOW PRESSURE WILL DROP DOWN FROM THE NNW AND SETTLE
OVER LWR MI ON WEDNESDAY BRINGING A FAIR AMOUNT OF CLOUD COVER.
THERE IS SOME POTENTIAL FOR A FEW LIGHT RAIN SHOWERS WITH THIS
FEATURE. HOWEVER FOR NOW WE WILL KEEP THE FCST DRY FOR WEDNESDAY
GIVEN THE DRY AIRMASS IN PLACE OVER OUR AREA AND VERY LOW 00Z
NUMERICAL GUIDANCE POPS/VERY LOW SREF POPS.

.LONG TERM...(WEDNESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 330 AM EDT MON APR 27 2015

IT SEEMS THE FORECAST IN THE LONG TERM HAS BECOME A BIT LESS CERTAIN
WITH EACH PASSING DAY. LOW CHANCES FOR RAIN SHOWERS ARE THE MAIN
STICKING POINT...WITH WEAK SYSTEMS PROVIDING THE FORCING. DECIDING
IN WHETHER TO KEEP CHANCES FOR RAIN IN THE FORECAST OR TO ADD RAIN
TO THE FORECAST WAS THE MAIN POINT OF CONTENTION.

THE OPERATIONAL GFS AND ECMWF ARE STILL AT ODDS WITH ONE ANOTHER ON
THE DEPTH OF THE UPPER LOW/TROUGH SWINGING SOUTH THROUGH THE GREAT
LAKES MID WEEK. THE GFS IS MUCH DEEPER AND CUT OFF WITH THE SYSTEM
AS COMPARED TO THE ECMWF. DECIDED TO USE SLIGHT CHANCES FOR RAIN
SHOWERS ON WEDNESDAY NIGHT AND THURSDAY...20 PCT...AS BOTH MODELS
SHOWS SOME LIGHT PRECIP IN THE FORECAST AREA. EVEN THE PREVIOUSLY
DRY CANADIAN GEM HAS SOME LIGHT PRECIP IN LOWER MI.

A DRY FRIDAY BEFORE THE NEXT SYSTEM FOR FRIDAY NIGHT AND SATURDAY.
NOT REAL CONFIDENT WE WILL SEE PRECIPITATION IN THIS TIME FRAME
EITHER. A WEAK SHORTWAVE TROUGH IS FORECAST TO SLIDE EAST THROUGH
THE NORTHERN GREAT LAKES PUSHING A SURFACE FRONT INTO OUR AREA. THE
GFS IS MUCH WEAKER WITH THE SYSTEM. OPTED TO HAVE A 20 PCT CHANCE
FOR LIGHT RAIN SHOWERS ONCE AGAIN.

SUNDAY INTO SUNDAY NIGHT THE FRONT COMES BACK AS A WARM FRONT WITH
ADDITIONAL CHANCES FOR RAIN SHOWERS.

OVERALL...A LOWER CONFIDENCE IN THESE FORECAST PERIODS AS OPPOSED
TO A COUPLE DAYS BACK. WEAK SYSTEMS WITH MODEL DISPARITIES ARE WHAT
LEAD TO THE LOW CONFIDENCE. WHAT CAN BE SAID THOUGH IS WE SHOULD
STILL SEE THE SLOW MODERATION IN TEMPERATURES AND WHAT PRECIPITATION
DOES FALL SHOULD BE ON THE LIGHT SIDE.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 744 AM EDT MON APR 27 2015

CLOUDS WILL CONTINUE TO DRIFT SOUTH THROUGH THE AREA TODAY.
CEILINGS SHOULD MAINLY BE VFR...ESPECIALLY TOWARDS LAKE MICHIGAN.
THE EXCEPTION WILL TOWARDS KLAN AND KJXN WHERE SOME MVFR CEILINGS
CAN BE EXPECTED THROUGH MIDDAY. THINKING THAT CEILINGS WILL LIFT
ENOUGH TO VFR EVERYWHERE THIS AFTERNOON. TONIGHT...THINKING SKIES
WILL SCATTER OUT. WINDS WILL BE NORTH TODAY AROUND 10
MPH...BECOMING LIGHT TONIGHT.

&&

.MARINE...
ISSUED AT 330 AM EDT MON APR 27 2015

NORTH WINDS WILL RAMP UP SOMEWHAT THIS AFTERNOON AND EARLY EVENING
CAUSING WAVE HEIGHTS TO BUILD TO 2 TO 4 FEET OVER OUR SOUTHERN
NEARSHORE ZONES. HOWEVER CONDITIONS SHOULD STAY BELOW SMALL CRAFT
CRITERIA. WAVE HEIGHTS WILL DIMINISH TONIGHT AS WINDS SUBSIDE.


&&

.HYDROLOGY...
ISSUED AT 1059 AM EDT SUN APR 26 2015

RIVERS ACROSS SOUTHWEST LOWER MICHIGAN ARE MOSTLY AROUND NORMAL
LEVELS AND STEADY OR SLOWLY FALLING. WITH DRY WEATHER FORECAST... NO
CHANGES ARE EXPECTED THIS WEEK.

&&

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

$$

SYNOPSIS...LAURENS
SHORT TERM...LAURENS
LONG TERM...DUKE
AVIATION...DUKE
HYDROLOGY...63
MARINE...LAURENS





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