Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 191930
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
307 PM EDT TUE MAY 19 2015

LATEST UPDATE...
SYNOPSIS/SHORT TERM/LONG TERM/MARINE

.SYNOPSIS...
ISSUED AT 307 PM EDT TUE MAY 19 2015

A COOL AIR MASS HAS SETTLED INTO SOUTHWEST LOWER MICHIGAN AND FROST
AND FREEZING TEMPERATURES ARE A DISTINCT POSSIBILITY TONIGHT. A
FREEZE WARNING HAS BEEN POSTED FOR CENTRAL LOWER MICHIGAN AND A
FROST ADVISORY HAS BEEN HOISTED FOR THE REMAINING AREAS OF SOUTHWEST
LOWER MICHIGAN. DRY WEATHER IS EXPECTED THE REMAINDER OF THE WORK
WEEK. CONDITIONS WILL REMAIN ON THE COOL SIDE OF NORMAL THIS
WEEK...WITH A WARMUP AS WE MOVE THROUGH THE HOLIDAY WEEKEND. ALONG
WITH THE WARMER AIR WILL COME CHANCES FOR RAIN...ESPECIALLY SUNDAY
INTO MEMORIAL DAY.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 307 PM EDT TUE MAY 19 2015

MAIN FOCUS OF THE SHORT TERM WAS ON WHETHER TO EXPAND A FROST
HEADLINE INTO THE COUNTIES THAT WERE NOT COVERED BY THE FREEZE
WARNING ACROSS CENTRAL LOWER. DECIDED TO DO THAT...SO A FROST
ADVISORY IS NOW IN PLACE FOR THE REST OF THE FORECAST
AREA...ESSENTIALLY FROM INTERSTATE 96 TO THE SOUTH. DRIER AIR
CONTINUES TO POUR INTO THE AREA ON NORTHWEST WINDS...WITH THE DEW
POINT CURRENTLY AT GRAND RAPIDS AT 31 DEGREES. THINKING THE
STRATOCUMULUS WILL FADE WITH THE SETTING SUN THIS EVENING WHICH
SHOULD SET UP OK RADIATIONAL CONDITIONS. ONE ITEM OF CONCERN IS A
CORE OF WIND THAT IS SEEN IN NAM CROSS SECTIONS IN BUFKIT.
STILL...GIVEN A DECENT AMOUNT OF MAINLY CLEAR SKIES TONIGHT AND VERY
DRY/COOL AIR ALREADY IN PLACE FELT HEADLINES WERE WARRANTED ACROSS
THE FORECAST AREA.

THE REMAINDER OF THE SHORT TERM WILL BE QUIET. WE HAVE A DRY
FORECAST IN PLACE TONIGHT THROUGH THURSDAY NIGHT. THERE IS A
SHORTWAVE THAT SLIDES BY THE SOUTHERN GREAT LAKES TOMORROW NIGHT
INTO THURSDAY...BUT HAVE SIDED WITH THE DRY ECMWF AND GFS MODELS.
THE PRECIP SHOULD MISS US JUST TO THE SOUTH. ALSO ON THURSDAY...A
WEAK TROUGH MOVES THROUGH THE LOWER PENINSULA WITH SOME SPOTTY
PRECIP AMOUNTS BEING KICKED OUT BY THE MODELS. MOISTURE IS NOT ALL
THAT DEEP IN THE WED NIGHT THROUGH THURS NIGHT TIME FRAME SO AM
OPTING FOR DRY.

IT WILL BE COOL THE NEXT SEVERAL DAYS WITH NO MAJOR WARM ADVECTION
PUSH AT 850MB/S.

.LONG TERM...(FRIDAY THROUGH TUESDAY)
ISSUED AT 307 PM EDT TUE MAY 19 2015

THE MAIN FOCUS IN THE LONG TERM WILL BE THE POSSIBLITY FOR WET
WEATHER AND GUSTY WINDS GOING INTO THE HOLIDAY WEEKEND.

HIGH PRESSURE WILL BE IN CONTROL EARLY IN THE PERIOD FROM FRIDAY
THROUGH THE MAJORITY OF SATURDAY. AS HIGH PRESSURE PROGRESSES TO THE
EAST AN AREA OF LOW PRESSURE WILL BEGIN TO EJECT OUT OF THE
SOUTHWEST AND INTO THE CENTRAL PLAINS. A WARM FRONTAL BOUNDARY WILL
EXTEND OUT AHEAD OF THE SYSTEM...GIVING WAY TO SOUTHERLY INFLUENCE.
THIS SYSTEM WILL TAKE SOMEWHAT OF A SIMILAR TRACK TO LAST WEEKENDS
SYSTEM...THROUGH THE UPPER MIDWEST.

THE BEST PRECIPITION CHANCES WILL LIKELY BE LATE SATURDAY NIGHT INTO
SUNDAY MORNING AND AGAIN MONDAY AFTERNOON AND EVENING. SATURDAY
NIGHTS RAINFALL WILL BE ASSOCIATED WITH THE RESULTING ISENTROPIC
LIFT WITH THE PASSAGE OF THE WARM FRONT. LOW PRESSURE THEN
TRANSITIONS FROM A CLOSED LOW TO A SHORT WAVE THAT IS EVENTUALLY
CONSUMED AROUND THE MAIN CYCLONIC FLOW NEAR THE HUDSON BAY. THE WARM
FRONTAL BOUNDARY GETS HINGED UP OVER CENTRAL AND NORTHERN LOWER
MICHIGAN AND BECOMES NEARLY STATIONARY. WE MAY VERY WELL SEE A LULL
IN ACTIVITY SUNDAY AFTERNOON AS WE LOSE THE LIFT.

GOING INTO MEMORIAL DAY IS WHERE WE SEE THE POSSIBILITY OF GUSTY
WINDS AND THE POTENTIAL FOR THUNDERSTORMS. WHILE UPPER LEVEL WINDS
ARE NOT SO IMPRESSIVE...AN 850MB JET CORE OF 40-50KTS MOVES OVER THE
SOUTHERN PORTIONS OF THE FORECAST AREA. THIS IS SOMETHING THAT WOULD
USUALLY TRIGGER SOME CONCERN...BUT THERE ARE A COUPLE OF LIMITING
FACTORS TO ANY REAL ORGANIZED CONVECTION. THE BEST LIFT WOULD REMAIN
NORTH ALONG THE BOUNDARY...WHILE THE BEST CAPE STAYS SOUTHEAST OF
GRAND RAPIDS. THIS MAY BE SOMETHING TO WATCH AS WE CREEP CLOSER TO
MONDAY IF CONDITIONS BECOME BETTER ORGANIZED. OTHERWISE...IT SEEMS
THE HOLIDAY WILL HAVE SCATTERED AFTERNOON THUNDERSTORMS...SOME
LOCALIZED HEAVY RAINFALL AND GUSTY WINDS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 219 PM EDT TUE MAY 19 2015

DRIER AIR WILL CONTINUE TO WORK INTO THE REGION OVER THE NEXT
SEVERAL HOURS. MVFR CONDITIONS WILL GRADUALLY IMPROVE WITH VFR
CONDITIONS EXPECTED AREA WIDE. GUSTY WINDS SHOULD CALM THROUGH
LATE THIS EVENING AND OVERNIGHT TONIGHT. CLEAR SKIES WILL SETTLE
ALSO SETTLE IN. HIGH LEVEL SCATTERED/BROKEN CLOUDS MAY FILTER IN
NEAR DAWN ON WEDNESDAY WITH WINDS REMAINING AROUND OR BELOW 5KTS.
NO REAL IMPACTS ARE EXPECTED THROUGH 18Z WEDNESDAY WITH VFR
CONDITIONS EXPECTED.

&&

.MARINE...
ISSUED AT 307 PM EDT TUE MAY 19 2015

EXTENDED THE SMALL CRAFT ADVISORY THROUGH 800 PM. OBS ARE STILL GUST
TO AROUND 20 KNOTS IN MOST AREAS. THE BUOYS AT LAST CHECK ARE IN THE
3 TO 5 FOOT RANGE AT MUSKEGON...PORT SHELDON AND SOUTH HAVEN IN
TERMS OF WAVE HEIGHTS. EXPECTING THINGS TO DIMINISH TONIGHT. ONE
POSSIBLE ISSUE IS HIGH RESOLUTION GUIDANCE LIKE THE HRRR IS SHOWING
A SURGE IN WINDS FROM HOLLAND SOUTH AFTER DARK. THIS IS LIKELY DUE
TO SOME CHANNELLING AND FUNNELLING DOWN THE SHORELINE IN NORTHERLY
FLOW. THE EVENING SHIFT WILL BE MONITORING THE LATEST TRENDS IN THE
HIGH RESO GUIDANCE FOR A POSSIBLE EXTENTION IN TIME SOUTH OF
HOLLAND. THE SOUTH HAVEN GLERL OB ON THE PIER AND THE BUOY JUST
OFFSHORE WILL BE THE PIECES OF DATA TO WATCH AFTER DARK TO SEE IF
THE HRRR VERIFIES. OTHERWISE FAIRLY LIGHT WINDS THE NEXT FEW DAYS.

&&

.HYDROLOGY...
ISSUED AT 140 PM EDT MON MAY 18 2015

IN GENERAL...RIVER LEVELS ACROSS SOUTHWEST LOWER MICHIGAN ARE
GRADUALLY FALLING. THAT WILL CONTINUE TO BE THE CASE WITH LIMITED
QPF THIS WEEK. FAIR WEATHER WILL DOMINATE FOR THE REST OF THE WEEK
INTO AT LEAST SATURDAY. THE NEXT SIGNIFICANT CHANCE FOR WIDESPREAD
RAINFALL WILL BE LATE IN THE HOLIDAY WEEKEND INTO NEXT WEEK.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...FROST ADVISORY FROM MIDNIGHT TONIGHT TO 8 AM EDT WEDNESDAY FOR
     MIZ050-056>059-064>067-071>074.

     FREEZE WARNING FROM MIDNIGHT TONIGHT TO 8 AM EDT WEDNESDAY FOR
     MIZ037>040-043>046-051-052.

LM...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR LMZ844>849.

&&

$$

SYNOPSIS...DUKE
SHORT TERM...DUKE
LONG TERM...JAM
AVIATION...JAM
HYDROLOGY...EBW/CAS
MARINE...DUKE



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