Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 140001
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
801 PM EDT SAT SEP 13 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 312 PM EDT SAT SEP 13 2014

SKIES WILL PARTIALLY CLEAR TONIGHT...AND WITH LIGHT WINDS...
TEMPERATURES WILL PLUMMET.  LOWS ARE EXPECTED TO BE IN THE
30S TONIGHT NORTH OF I-96 WHERE FROST APPEARS TO BE LIKELY.
MEANWHILE FOR AREAS ALONG AND SOUTH OF I-96...THE TEMPERATURE IS
EXPECTED TO DIP INTO THE UPPER 30 TO AROUND 40.  ANY FROST ALONG AND
SOUTH OF I-96 IS EXPECTED TO BE PATCHY.

THE NEXT COUPLE OF NIGHTS WILL NOT BE AS COLD AS WE WILL SEE CLOUDS
INCREASING.  THERE WILL BE A CHANCE OF RAIN LATE SUNDAY NIGHT...
LIKELY INTO MONDAY...THEN THE SHOWERS WILL EXIT MONDAY NIGHT.

THE REST OF THE WEEK APPEARS TO BE MAINLY DRY.  TEMPERATURES SHOULD
WARM A BIT WITH HIGHS IN THE MID 60S TO LOWER 70S.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT)
ISSUED AT 312 PM EDT SAT SEP 13 2014

THE MAIN CONCERN IS FOR FROST TONIGHT AS SKIES CLEAR UNDER LIGHT
WINDS.

HAVE DECIDED TO GO WITH A FROST ADVISORY FOR THE NORTHERN ROW OF
COUNTIES AS WELL AS THE NEXT ROW DOWN...MINUS OCEANA COUNTY.  EXPECT
CLEARING TO OCCUR THIS EVENING AS CLOUDS ON THE VISIBLE SATELLITE
APPEAR LARGELY OPEN CELLULAR.  THERE IS ENOUGH LOW LEVEL MOISTURE
AROUND TO ASSUME SOME CLOUDS WILL LINGER...BUT FEEL WE WILL SEE
ENOUGH CLEARING TO SUPPLY SEVERAL HOURS OF IDEAL RADIATIONAL COOLING
CONDITIONS ACROSS THE CWA.  THE POTENTIAL FOR AN EARLY SEASON FROST
APPEARS HIGH FOR AREAS AWAY FROM THE LAKE AND NORTH OF HIGHWAY 10..
THE HIGHER ELEVATIONS HERE WILL COME INTO PLAY TOO.  THE COUNTIES
FROM NEWAYGO TO ISABELLA SHOULD ALSO SEE FROST...ESPECIALLY IN THE
LOW HOLLOWS.  ELSEWHERE...ALONG THE LAKESHORE AND ALONG AND SOUTH OF
I-96 EXPECT SOME PATCHY FROST WILL BE POSSIBLE BUT IT SHOULDN/T BE
WIDESPREAD ENOUGH TO WARRANT A HEADLINE.

AFTER A CHILLY START EXPECT A QUIET SUNDAY.  CLOUDS WILL BE ON THE
INCREASE SUNDAY EVENING AS HIGH PRESSURE DRIFTS EAST AND A COLD
FRONT MOVES SE ACROSS WISCONSIN THROUGH THE NIGHT.  WE WILL START
THE EVENING WITH DRY LOW LEVELS SO EXPECT IT WILL TAKE A WHILE
BEFORE WE SEE PCPN...HAVE LOW CHANCE POPS AFTER MIDNIGHT.

A MUCH BETTER CHANCE OF RAIN COMES MONDAY AS THE FRONT SLIDE ACROSS
THE CWA.  THE PCPN SHOULD PEAK DURING THE AFTERNOON AS THE RIGHT
ENTRANCE REGION OF THE UPPER JET COMES ACROSS SOUTHERN LOWER...THIS
LINGERS OVERHEAD UNTIL MID EVENING.  A 30 KNOT LOW LEVEL JET SHOULD
ALSO HELP THE CAUSE...AGAIN OVER SOUTHERN LOWER.  INSTABILITY LOOKS
MARGINAL SO KEPT THUNDER OUT OF THE FORECAST.  NOT EXPECTING TOO
MUCH PCPN OVERALL WITH AMOUNTS EXPECTED TO BE UNDER A QUARTER INCH.
THE SHOWERS SHOULD EXIT MONDAY EVENING AS THE FRONT AND UPPER
DYNAMICS MOVE EAST.

.LONG TERM...(TUESDAY THROUGH SATURDAY)
ISSUED AT 312 PM EDT SAT SEP 13 2014

REALLY THERE IS ONLY ONE MAJOR ISSUE FOR THIS PART OF THE FORECAST.
THE QUESTION IS WILL THE ARCTIC FRONT FORECAST BY ALL OF THE MODELS
MAKE IF FARTHER SOUTH THAN IT IS CURRENTLY FORECAST TO DO MID TO
LATE WEEK? THIS NEW AIRMASS IS MUCH COLDER THAN WHAT WE ARE NOW
EXPERIENCING. THIS CURRENT EVENT HAS 850 MB TEMPS IN THE -2 TO -4C
RANGE NEAR THE CANADIAN BOARDER. THIS NEXT SHOT OF COLD AIR HAS -8
TO -12C 850 AIR BEHIND IT. IF THIS AIRMASS CAN GET THIS FAR SOUTH
THIS WOULD LIKELY RESULTS IN BELOW FREEZING TEMPERATURES AT NIGHT
OVER A GOOD PART OR OUR CENTRAL AND NORTHERN CWA. GIVEN THAT THERE
ARE MANY FROST SENSITIVE CROPS STILL GROWING... THIS WOULD BE A
SERIOUS ISSUE FOR GROWERS.

CURRENTLY WE HAVE CLOSED UPPER LOW NEAR BAFFIN ISLAND WITH 70 KNOT
JET CORE ON THE WEST SIDE OF THE SYSTEM. THIS JET CORE DIVES NEARLY
DUE SOUTH INTO TUESDAY NIGHT... LOCATED JUST WEST OF SOUTHERN JAMES
BAY BY TUESDAY MORNING. TYPICALLY THE MODELS DO NOT DO WELL WITH
POLAR FRONTS THIS FAR OUT IN TIME. GIVEN HOW FREQUENTLY THESE EVENTS
HAVE MANAGED TO GET DOWN HERE THIS ENTIRE YEAR... FREQUENTLY WHEN
NOT FORECAST TOO OUT AT THIS FORECAST TIME RANGE... WE NEED TO WATCH
THIS VERY CLOSELY.

MY CURRENT GRIDS DO NOT IN ANY WAY REFLECT MY ABOVE THINKING SINCE
AT THIS POINT MY CONFIDENCE FOR THIS IS LESS THAN 50/50. EVEN SO...
THIS IS A REAL POSSIBILITY THAT WOULD HAVE A SIGNIFICANT IMPACT IF
IT DOES NEED HAPPEN.

IF THIS ARCTIC FRONT PASSAGE DOES NOT HAPPEN...WE WOULD SEE A
DISSIPATING BACK DOOR COLD FRONT DROP INTO THE AREA WEDNESDAY BUT IT
WOULD HAVE LITTLE IN THE WAY OF WEATHER WITH IT. ALL IT WOULD DO IS
SLOW DOWN THE WARM UP THAT WOULD OTHERWISE HAVE HAPPENED.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 759 PM EDT SAT SEP 13 2014

SKIES WILL CLEAR OUT THROUGH THE EVENING WITH VFR WEATHER TO
PREVAIL FOR THE MOST PART. KMKG WILL LIKELY SEE A PERIOD OF MVFR
CONDITIONS AS LAKE CLOUDS PUSH ONSHORE LATER TONIGHT. A SOUTHWEST
FLOW WILL DEVELOP SUNDAY...BUT WILL LIKELY REMAIN UNDER 20 KNOTS.

&&

.MARINE...
ISSUED AT 312 PM EDT SAT SEP 13 2014

WINDS AND WAVES WILL BE TRENDING DOWN THROUGH THIS EVENING.  WILL
KEEP THE SMALL ADVISORY GOING UNTIL 10 PM.  THERE COULD BE ANOTHER
MARGINAL SCA PERIOD MID DAY SUNDAY THROUGH MID DAY MONDAY.  A SW
FETCH SHOULD KEEP THE LAKE RATHER ROUGH.


&&

.HYDROLOGY...
ISSUED AT 312 PM EDT SAT SEP 13 2014

NO HYDRO CONCERNS AS THE PCPN FROM LATE SUNDAY NIGHT THROUGH MONDAY
EVENING SHOULD REMAIN UNDER A QUARTER INCH.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...FROST ADVISORY FROM 3 AM TO 9 AM EDT SUNDAY FOR MIZ037>040-
     044>046.

LM...SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR LMZ844>848.

&&

$$

SYNOPSIS...JK
SHORT TERM...JK
LONG TERM...WDM
AVIATION...MJS
HYDROLOGY...JK
MARINE...JK







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