Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 210456
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1156 PM EST TUE JAN 20 2015

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 330 PM EST TUE JAN 20 2015

ANOTHER ROUND OF LIGHT SNOW WILL IMPACT SOUTHERN LOWER MICHIGAN LATE
TONIGHT AND WEDNESDAY. EXPECT ACCUMULATIONS OF 1 TO 2 INCHES MAINLY
SOUTH OF A LINE FROM MUSKEGON TO ALMA AND AN INCH OR LESS NORTH OF
THERE. THE WEDNESDAY MORNING COMMUTE WILL BE SIMILAR TO TUESDAY
MORNING... WITH AREAS OF REDUCED VISIBILITY AND POTENTIALLY SLICK
CONDITIONS. TEMPERATURES WILL BE BELOW FREEZING FOR THE NEXT COUPLE
DAYS THEN REBOUND BACK INTO THE UPPER 30S FOR FRIDAY AND SATURDAY.

&&

.UPDATE...
ISSUED AT 1006 PM EST TUE JAN 20 2015

THE FORECAST IS STILL ON TRACK FOR SNOWFALL TO OVERSPREAD THE AREA
THROUGH LATE TONIGHT AND INTO WEDNESDAY. RUN TO RUN MODEL
CONSISTENCY HAS BEEN PRETTY GOOD UP THROUGH NOW. THE ONSET OF
PRECIPITATION SHOULD BE FAIRLY LIGHT WITH THE GREATEST CHANCES
MOVING IN AFTER 12Z. THE I-94 AREA RUNNING FROM ABOUT BATTLE CREEK
THROUGH JACKSON AND JUST SOUTH OF LANSING SEEMS TO BE THE BEST FOR
TOTALS THAT COULD EXCEED 2 INCHES. THIS WILL BE CONSIDERED IN
UPDATES TONIGHT...BUT ANY CHANGES TO SHOULD BE MINIMAL.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 330 PM EST TUE JAN 20 2015

MODELS HAVE BEEN CONSISTENT FOR SEVERAL RUNS NOW ON QPF AMOUNTS AND
PLACEMENT WITH THE NEXT CLIPPER DROPPING ESE FROM THE NRN PLAINS.
THERE IS ALSO NOT THE ISSUE OF DRY AIR TO OVERCOME AT THE ONSET AND
AN UPPER LOW THAT PASSES DIRECTLY OVERHEAD. CONFIDENCE IS THEREFORE
HIGHER THAN WITH THE EXITING WAVE ON WIDESPREAD 1 TO 2 INCH AMOUNTS
ALONG/SOUTH OF THE I-96 CORRIDOR. NO HUGE IMPACTS BUT ANOTHER
SLIPPERY AND SLOWER THAN AVERAGE MORNING COMMUTE.

WITH THE UPPER LOW BEING A CLOSED CIRCULATION AS IT COMES ACROSS SRN
LWR MI..THIS WILL LIKELY RESULT IN THE SNOW LINGERING LONGER AND
POSSIBLY EVEN PIVOTING A BIT FARTHER NORTH THAN THE CURRENT GUIDANCE
SUGGESTS. WILL KEEP HIGH POPS RUNNING ALL DAY WEDNESDAY OVER THE
BULK OF THE CWFA RATHER THAN MOVING IT OUT IN THE AFTERNOON LIKE
TUESDAY`S EVENT.

BETTER CHANCE OF PULLING DOWN SOME COLDER/DRIER AIR BEHIND THIS
SECOND CLIPPER WEDNESDAY NIGHT AND THURSDAY. THIS SHOULD LEAD TO
PARTIAL CLEARING ALTHOUGH PERHAPS SOME LAKE EFFECT SNOW SHOWERS
ALONG THE COAST. NOT SEEING ANY ACCUMULATION WITH THE LAKE EFFECT
SINCE MOISTURE IS VERY SHALLOW AND SFC RIDGING IS MOVING IN.

.LONG TERM...(FRIDAY THROUGH TUESDAY)
ISSUED AT 330 PM EST TUE JAN 20 2015

CHANCE OF A LIGHT SNOW EVENT SUNDAY OTHERWISE SEASONABLY WARM AND
DRY CONDITIONS INTO EARLY NEXT WEEK.

MEDIUM RANGE FORECAST GUIDANCE IS VERY SIMILAR TO YESTERDAY. MI WILL
REMAIN IN NORTHWEST FLOW ALOFT WITH AN UPPER RIDGE TO OUR WEST AND A
BROAD UPPER TROUGH TO OUR EAST. THIS FLOW IS TYPICALLY DRY WITH
QUICK MOVING "CLIPPER" LOWS THAT MOVE RAPIDLY TO THE EAST-SOUTHEAST
WITH THE MID LEVEL FLOW.

FRIDAY IS LOOKING MUCH LIKE LAST SATURDAY WITH WARM AND BREEZY
CONDITIONS. THE NEXT CLIPPER LOW WILL TRACK ACROSS SOUTHERN CANADA
WITH BROAD SOUTHWEST WARM ADVECTION SURFACE WINDS ACROSS THE MI LP.
CURRENT CONSENSUS INDICATES TEMPS IN THE MID 30S FRIDAY
AFTERNOON...BUT WOULD SAY THAT LOW 40S ARE NOT OUT OF THE QUESTION.
TRAILING COLD FRONT DROPS SOUTH OF THE STATE BY MIDDAY SATURDAY.
THERE WILL BE A FEW BRIEF RAIN/SNOW SHOWERS AS THE FRONT MOVES
THROUGH BUT NOTHING OF CONSEQUENCE.

THE MOST INTERESTING CLIPPER...RELATIVELY SPEAKING...MOVES SOUTH OF
THE REGION ON SUNDAY. STILL LIKING ECMWF ENSEMBLE MEAN WHICH HAS
BEEN CONSISTENT WITH A ROUGHLY 1-3 INCH SNOW THREAT ROUGHLY SOUTH OF
A MUSKEGON TO LANSING LINE ENDING EARLY MONDAY. DETERMINISTIC NWP
HAS BEEN LESS CONSISTENT WITH RUN-TO-RUN FLIP FLOPS.  BOTH 12Z ECMWF
AND GFS ARE STRONGER AND FARTHER NORTH...BUT GFS IS STILL DRY WHILE
ECMWF IS SIMILAR TO 00Z ENSEMBLE MEAN.

ONE LAST NOTABLE...THERE IS GOOD AGREEMENT ON ARCTIC AIR BUILDING IN
CENTRAL CANADA. THAT IS THE H85 25 - 35 BELOW PURE ARCTIC AIR...BUT
PRESENTLY THERE IS NOT A GOOD CONSENSUS ON WHEN IT MIGHT PLUNGE
SOUTH. LATEST FIM/ECMWF INDICATING BEST BET FOR A PLUNGE INTO THE
GREAT LAKES / MIDWEST WOULD BE LATE NEXT WEEK...JUST IN TIME FOR
GROUND HOG DAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1154 PM EST TUE JAN 20 2015

THE FORECAST LARGELY SEEMS ON TRACK THE SNOW CURRENTLY DEVELOPING
FROM GRR THROUGH LWA. EXPECT IFR CONDITIONS IN SNOW AT ALL TAF
SITES FROM AROUND 12Z THROUGH 16Z.  I WOULD EXPECT A PERIOD OF
MODERATE SNOW DURING THE MID MORNING AS THE MAIN UPPER WAVE ROTATES
THROUGH THE AREA. THE WESTERN TAF SITES WILL SEE THE SNOW END BY
MID AFTERNOON WHILE THE EASTER TAF SITE COULD SEE THE SNOW LAST
INTO THE EVENING.

THE LIGHT SNOW CURRENTLY DEVELOPING OVER SOUTHWEST MICHIGAN IS A
WEAK LEAD WAVE ROTATING THROUGH SOUTHWEST MICHIGAN. THE SNOW FROM
THIS LEAD WAVE SHOULD NOT BE ALL THAT SIGNIFICANT...STILL I WOULD
EXPECT IFR CONDITIONS EVEN WITH THIS SNOW BY 08Z AT THE MORE
WESTERN TAF SITES.



&&

.HYDROLOGY...
ISSUED AT 330 PM EST TUE JAN 20 2015

NEAR TO A LITTLE ABOVE NORMAL TEMPERATURES AND A LACK OF SIGNIFICANT
PRECIPITATION THIS WEEK WILL RESULT IN LIMITED ICE AND SNOW MELT.
THIS SHOULD RESULT IN A GRADUAL FALL IN RIVER LEVELS. ICE BREAKUP
IS NOT EXPECTED.

&&

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

$$

UPDATE...JAM
SYNOPSIS...MEADE
SHORT TERM...MEADE
LONG TERM...COBB
AVIATION...WDM
HYDROLOGY...63





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