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000
FXUS63 KGRR 241114
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
714 AM EDT FRI MAY 24 2013

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 327 AM EDT FRI MAY 24 2013

A COOL AND DRY AIR MASS WILL SIT OVER THE GREAT LAKES REGION TODAY
AND THROUGH THE HOLIDAY WEEKEND.  DESPITE THIS THERE WILL BE PERIODS
OF CLOUDS MOVING THROUGH.  MUCH OF SOUTHWEST MICHIGAN WILL SEE
INCREASING CLOUDS TONIGHT.  MOST OF THESE CLOUDS SHOULD ERODE ON
SATURDAY...HOWEVER THE FAR SOUTHWEST PORTION OF THE STATE MAY SEE A
FAIR AMOUNT OF CLOUDS BOTH SATURDAY AND SUNDAY.  A FEW SPRINKLES ARE
POSSIBLE SATURDAY AFTERNOON AND EVENING OVER THE EXTREME SOUTHWEST
PORTION OF THE STATE.  TEMPERATURES WILL BE SLIGHTLY COOLER THAN
NORMAL THROUGH SUNDAY WITH DAYTIME HIGHS MAINLY IN THE 60S.

LOOKING INTO NEXT WEEK...A CHANCE OF RAIN RETURNS MONDAY NIGHT INTO
TUESDAY...WITH ANOTHER CHANCE OF RAIN BY THURSDAY.  TEMPERATURES
WILL WARM INTO THE 70S FOR MONDAY AND TUESDAY...AND 80 TO 85 FOR
WEDNESDAY AND THURSDAY.

&&

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 327 AM EDT FRI MAY 24 2013

A COOL AND DRY AIR MASS HAS BEEN USHERED INTO THE CWA.  NORTHWEST
FLOW ALOFT WILL KEEP US FROM WARMING UP TOO MUCH OVER THE NEXT
COUPLE OF DAYS.  FROST WILL BE POSSIBLE AGAIN TONIGHT AND SATURDAY
NIGHT ACROSS CENTRAL LOWER.

SURFACE HIGH PRESSURE WILL SETTLE OVER THE REGION TONIGHT AND WILL
ONLY DRIFT SLOWLY EAST TO LAKE HURON BY SUNDAY.  THIS SYSTEM WILL
KEEP US SLIGHTLY COOLER THAN NORMAL ALONG WITH DRY WEATHER.  HOWEVER
THERE IS MORE OF A CONCERN FOR MORE CLOUD COVER OVER THE WEEKEND
EVEN THOUGH THE SURFACE HIGH SITS OVER US.

THE UPPER PATTERN REMAINS FAIRLY STATIC THROUGH THE WEEKEND WITH
AN OMEGA BLOCK IN PLACE ACROSS THE NATION.  AN UPPER LOW WILL REMAIN
OVER THE PACIFIC NORTHWEST WITH UPPER RIDGING OVER THE MIDDLE OF THE
NATION.  THE MODELS CONTINUE TO SHOW MOISTURE FROM THE PACIFIC
NORTHWEST SYSTEM COMING OVER THE RIDGE AND SLIPPING INTO THE GREAT
LAKES REGION.  THIS APPEARS TO ARRIVE BY TONIGHT...ESPECIALLY OVER
THE SW CWA.  BUT IT APPEARS THERE COULD BE ENOUGH CLOUDS EVEN IN THE
NORTH TO NOT JUMP ON A FROST ADVISORY JUST YET.  WILL LET THE DAY
SHIFT MONITOR CLOUD TRENDS.

A TOUGH CLOUD FORECAST FOR SATURDAY AND SUNDAY.  WILL TREND A BIT
CLOUDIER THAN THE PREVIOUS FORECAST...BUT IT DOES APPEAR DRIER MID
LEVEL AIR TRIES TO MOVE IN FROM CENTRAL CANADA WHICH MAY BUMP THE
CLOUDS A BIT FURTHER SW.  WILL CARRY THE MOST CLOUDS OVER THE SW CWA
WHERE A SPRINKLE COULD EVEN OCCUR SATURDAY AFTERNOON/EVENING.  WILL
GO PARTLY TO MOSTLY SUNNY ELSEWHERE THROUGH THE WEEKEND.

.LONG TERM...(SUNDAY NIGHT THROUGH THURSDAY)
ISSUED AT 327 AM EDT FRI MAY 24 2013

TIMING OF CONVECTION WITH THE WARM FRONT LIFTING THROUGH LOWER
MICHIGAN EARLY NEXT WEEK IS THE PRIMARY FORECAST PROBLEM IN THE
EXTENDED. MODEL AGREEMENT IS GENERALLY GOOD...SHOWING A SERIES OF
CONVECTIVE CLUSTERS PASSING JUST SOUTH OF LOWER MICHIGAN SUNDAY
NIGHT THROUGH MONDAY NIGHT. GFS IS QUICKER TO BRING THE FRONT
THROUGH THE FORECAST AREA ON MONDAY NIGHT...WHILE THE ECWMF HAS IT
VERY SLOWLY LIFTING THROUGH BETWEEN TUESDAY AND WEDNESDAY.

PERHAPS THE EFFECT OF CONVECTION TRAINING ALONG THE FRONT WILL
IMPEDE ITS NORTHWARD PROGRESS...SO WILL SHADE POPS HIGHER TUESDAY
NIGHT AND THEN FOCUS THE HIGHER POPS ACROSS THE NORTHERN FORECAST
AREA AFTER WEDNESDAY AS THE FRONT MOVES NORTH. ECMWF STILL SHOWS
POTENTIAL FOR CONVECTION THROUGH THURSDAY WHILE THE GFS HAS THE
FRONT WELL NORTH AND UPPER RIDGING ACROSS LOWER MICHIGAN. WENT WITH
SLIGHT CHANCE POPS FOR NOW.

OVERALL IT LOOKS LIKE A POTENTIALLY WET PATTERN...AND THE POPS COULD
BE UNDERDONE AS A RESULT OF LACK OF CONFIDENCE IN TIMING AND
COVERAGE OF PRECIP MOST OF THE PERIOD.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 714 AM EDT FRI MAY 24 2013

VFR CONDITIONS THROUGH SATURDAY MORNING. WINDS WILL GO FROM NORTH
TO NORTHWEST TODAY AROUND 10 KNOTS WITH SOME GUSTS CLOSE TO 20
KNOTS POSSIBLE THIS AFTERNOON.

&&

.MARINE...
ISSUED AT 327 AM EDT FRI MAY 24 2013

WINDS AND WAVES WILL GRADUALLY DIMINISH THIS MORNING AS HIGH
PRESSURE BUILDS IN.  SCA WILL BE CARRIED THROUGH NOON TODAY OVER THE
SOUTHERN PORTION OF THE LAKE.  THEREAFTER NORTHERLY WINDS WILL
CONTINUE BUT WILL REMAIN 15 KNOTS OR LESS THROUGH THE WEEKEND.


&&

.FIRE WEATHER...
ISSUED AT 327 AM EDT FRI MAY 24 2013

A MUCH DRIER AIR MASS HAS MOVED INTO THE REGION.  DAYTIME RH VALUES
WILL DROP INTO THE 25 TO 30 PERCENT RANGE TODAY THROUGH SUNDAY.
HOWEVER NORTHERLY WINDS WILL STAY 15 MPH OR LESS THROUGH THE SAME
TIME PERIOD.

&&

.HYDROLOGY...
ISSUED AT 327 AM EDT FRI MAY 24 2013

A DRY SPELL IS IN STORE FOR THE REGION.  THE NEXT DECENT CHANCE OF
RAIN SHOULD HOLD OFF UNTIL MONDAY NIGHT.  HIGH RIVER LEVELS WILL
SLOWLY SUBSIDE INTO EARLY NEXT WEEK.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL NOON EDT TODAY FOR LMZ844-845.

&&

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...OSTUNO
AVIATION...OSTUNO
FIRE WEATHER...JK
HYDROLOGY...JK
MARINE...JK