Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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385
FXUS63 KGRR 191128
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
728 AM EDT TUE MAY 19 2015

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 316 AM EDT TUE MAY 19 2015

A COLD FRONT MOVED THROUGH LOWER MICHIGAN LAST NIGHT AND
TEMPERATURES HAVE FALLEN INTO THE 40S. CLOUDS HAVE ALSO MOVED OVER
SW LOWER MI FROM WISCONSIN AND WILL LINGER THROUGH THE DAY. CLOUDS
WILL CLEAR THIS EVENING AND TEMPERATURES WILL FALL TO FREEZING OR
JUST BELOW MAINLY NORTH OF M-46. A FREEZE WARNING IS IN EFFECT IN
THAT AREA. CHILLY TEMPERATURES CAN BE EXPECTED TODAY AND WEDNESDAY
WITH HIGHS IN THE 50S. TEMPERATURES WILL WARM INTO THE 70S OVER THE
WEEKEND. SEVERAL DAYS OF DRY WEATHER IS ANTICIPATED WITH THE NEXT
DECENT CHANCE OF SHOWERS AND THUNDERSTORMS COMING SUNDAY AND MONDAY.

&&

.UPDATE...
ISSUED AT 636 AM EDT TUE MAY 19 2015
RETRANSMITTED.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 316 AM EDT TUE MAY 19 2015

FORECAST CONCERNS DEAL WITH CLOUD COVER TODAY AND TEMPS TONIGHT.

THE MAIN CHANGE TO THE FORECAST WAS TO ADD A FREEZE WARNING TONIGHT
TO THE NORTHERN CWA.

LATEST IR LOOP SHOWS STRATOCU MOVING OVER THE CWA FROM WEST TO EAST.
THESE CLOUDS ARE ASSOCIATED WITH AN UPPER TROUGH MOVING ACROSS THE
GREAT LAKES. H9 RH PROGS INDICATE THAT THE STRATOCU WILL BEGIN TO
DISSIPATE THIS EVENING ACROSS THE SW CWA AND THEN OVERNIGHT ACROSS
THE REST OF THE CWA. TEMPS SHOULD FALL QUITE A BIT GIVEN THE DRY AIR
IN PLACE. OPTED TO ISSUE A FREEZE WARNING FOR THE NORTHERN 8
COUNTIES PLUS MONTCALM AND GRATIOT TO GIVE PEOPLE PLENTY OF TIME TO
TAKE PRECAUTIONS. SOME LOW LYING AREAS COULD SEE 27-28 DEGREES
OVERNIGHT. NOT EVERYONE WILL SEE FREEZING TEMPS IN THOSE COUNTIES
BUT THE THREAT WAS ENOUGH TO RUN WITH A FREEZE WARNING.
ELSEWHERE...WE DOWNPLAYED THE FROST THREAT DUE TO WINDS STAYING UP
AROUND 5-6 MPH OVERNIGHT.

TODAY WILL BE RATHER CHILLY WITH H8 TEMPS NEAR -3C MOVING ACROSS THE
CWA. HIGHS IN THE 50S EXPECTED TODAY AND WEDNESDAY.

A TROUGH PASSING THROUGH WEDNESDAY NIGHT MAY GENERATE A FEW SHOWERS
OVER THE FAR SOUTHERN CWA. HOWEVER...THE RISK SEEMED SMALL ENOUGH TO
LEAVE OUT OF THE GRIDS. IT/S MORE LIKELY THAT THE SHRA WILL REMAIN
SOUTH OF THE CWA WEDNESDAY NIGHT.

THURSDAY LOOKS DRY AND A BIT WARMER WITH HIGH PRESSURE STILL IN
CONTROL HOWEVER...A BACKDOOR COLD FRONT IS PROGD TO SLIP SOUTH FROM
ONTARIO AND MOVE ACROSS THE CWA. GIVEN LOW DEWPOINTS AND NOT MUCH OF
A MOISTURE SOURCE AVAILABLE...THE FRONT SHOULD MOVE THROUGH DRY.

.LONG TERM...(THURSDAY NIGHT THROUGH MONDAY)
ISSUED AT 316 AM EDT TUE MAY 19 2015

ONLY IMPACT WEATHER IN THE EXTENDED IS EXPECTED SUNDAY AND MONDAY AS
ISENTROPIC ASCENT NORTH OF SFC WARM FRONT COULD BRING SOME RAIN AND
POSSIBLY THUNDER. LATEST GUIDANCE SHOWS POTENTIAL FOR THESE WARM
ADVECTION SHOWERS FORMING LATE SATURDAY NIGHT...BUT THE CHANCES RAMP
UP MORE SUNDAY AFTERNOON WITH DEEPER LIFT. WILL HAVE LIKELY POPS
SUNDAY NIGHT INTO MONDAY. LACK OF INSTABILITY WILL LIMIT THUNDER
POTENTIAL.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 728 AM EDT TUE MAY 19 2015

LOW PRESSURE WILL BRING STRATUS CLOUDS AND A FEW SHOWERS TODAY
WITH WIDESPREAD MVR AND SOME AREAS OF IFR. CONDITIONS WILL IMROVE
THIS AFTERNOON AS THE LOW PULLS AWAY. WINDS WILL BE NORTHWEST 10
TO 15 KNOTS WITH GUSTS OVER 20 KNOTS.

&&

.MARINE...
ISSUED AT 316 AM EDT TUE MAY 19 2015

COLD ADVECTION WILL HELP TO MAINTAIN 3-5 FT WAVES TODAY. THE SCA
WILL REMAIN IN PLACE.


&&

.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. ONLY A FEW SCATTERED SHOWERS/STORMS ARE POSSIBLE THIS AFTERNOON
ALONG AND AHEAD OF A COLD FRONT SWEEPING THROUGH THE STATE. FAIR
WEATHER WILL DOMINATE FOR THE REST OF THE WEEK INTO SATURDAY. THE
NEXT SIGNIFICANT CHANCE FOR WIDESPREAD RAINFALL WILL BE LATE IN THE
HOLIDAY WEEKEND INTO NEXT WEEK. 00Z ECMWF EPS PROBABILITY
INDICATES A 30 TO 40 PERCENT CHANCE FOR GREATER THAN HALF AN INCH
OF RAIN SOUTH OF I-96 IN A 24-HOUR PERIOD ENDING MONDAY
AFTERNOON.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...FREEZE WARNING FROM MIDNIGHT TONIGHT TO 8 AM EDT WEDNESDAY FOR
     MIZ037>040-043>046-051-052.

LM...SMALL CRAFT ADVISORY UNTIL 5 PM EDT THIS AFTERNOON FOR
     LMZ844>849.

&&

$$

UPDATE...OSTUNO
SYNOPSIS...04
SHORT TERM...04
LONG TERM...OSTUNO
AVIATION...OSTUNO
HYDROLOGY...EBW
MARINE...04



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