Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 181755
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1255 PM EST THU DEC 18 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 330 AM EST THU DEC 18 2014

THERE WILL BE A CHANCE OF SOME LIGHT SNOW FLURRIES OR LIGHT
DRIZZLE/FREEZING DRIZZLE ACROSS THE AREA TODAY AS A WEAK FRONTAL
SYSTEM MOVES THROUGH. SKIES WILL BEGIN TO CLEAR LATER TODAY THROUGH
TONIGHT FROM NORTH TO SOUTH. A FAIR AMOUNT OF SUNSHINE WILL BE FOUND
ON FRIDAY BEFORE CLOUDS MOVE BACK IN ON SATURDAY.

THE WEATHER LOOKS TO BE A BIT MORE UNSETTLED BEGINNING ON TUESDAY
NEXT WEEK AND LASTING THROUGH CHRISTMAS DAY. A LOT OF UNCERTAINTY
EXISTS...HOWEVER SOME RAIN AND OR SNOW WILL BE POSSIBLE LEADING UP
THROUGH CHRISTMAS EVE.

&&

.UPDATE...
ISSUED AT 1107 AM EST THU DEC 18 2014

HAVE RECEIVED SOME ACCIDENT REPORTS IN THE LANSING AREA ASSOCIATED
WITH ICING FROM FREEZING DRIZZLE AND LIGHT SNOW. THERE HAS BEEN A
SLIGHT UPTICK IN RADAR RETURNS ALONG AND SOUTH OF I-96...LIKELY
ASSOCIATED WITH A WEAK UPPER DEFORMATION ZONE OVER SW LOWER MI.
THESE RETURNS ARE SOUTH OF A BOUNDARY THAT EXTENDED EAST THROUGH
HOLLAND AND GRAND RAPIDS AT 1045 AM. THIS BOUNDARY IS MOVING
SLOWLY SOUTH AND IS CO-LOCATED WITH A NARROW BAND OF SNOW THAT
MAY BE A FURTHER CATALYST FOR ICING...ESPECIALLY ON EXPOSED
ROADWAYS.

TEMPERATURES MAY INITIALLY BE SLOW TO RISE AHEAD OF THE BOUNDARY
AS VERY LIGHT PRECIPITATION FALLS INTO AIR WITH DEWPOINTS IN THE
MID-UPPER 20S. THE DELAYED WARMUP MAY KEEP TRAVEL HAZARDOUS INTO
EARLY AFTERNOON. WILL BE ISSUING A STATEMENT TO REFLECT THIS.

&&

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 330 AM EST THU DEC 18 2014

THE MAIN FCST CHALLENGE IN THE SHORT TERM DEALS WITH LIGHT
SNOW/DRIZZLE/FREEZING DRIZZLE CHCS FOR TODAY THROUGH THIS EVENING.
OTHERWISE...THE WEATHER LOOKS RATHER UNEVENTFUL FROM OVERNIGHT
TONIGHT THROUGH THE END OF THE SHORT TERM ON SATURDAY.

WE HAVE ADDED A CHC OF SNOW FLURRIES AND FREEZING DRIZZLE TO THE
FCST FOR THIS MORNING...CHANGING TO FLURRIES AND REGULAR DRIZZLE FOR
THIS AFTERNOON. THE DRIVING FORCE FOR THIS LIGHT PCPN IS IS A SFC
TROUGH THAT EXTENDS ACROSS NRN LOWER MI AND NRN WI. THIS TROUGH WILL
ONLY DRIFT SOUTH AS THE SUPPORTING UPPER TROUGH THAT EXTENDS FROM
THE LOW JUST OFFSHORE OF MAINE WILL ONLY SLOWLY MOVE OUT.

THIS TROUGH WILL ACT ON RELATIVELY SHALLOW MOISTURE THAT REMAINS IN
PLACE ACROSS THE AREA. THIS MOISTURE IS ON THE VERGE OF SATURATING/
NOT SATURATING THE DGZ. WE ARE SEEING SOME LIGHT ECHOES ON
THE RADAR WHICH SEEMS TO BE VERY LIGHT MIST THAT IS PATCHY IN
NATURE. WE ARE ALSO SEEING SOME LIGHT SNOW BEING REPORTED AT TIMES
AT SOME LOCATIONS. WE FEEL THAT THIS WILL CONTINUE TO BE THE CASE
UNTIL IT LIKELY ENDS AS THE TROUGH DROPS SOUTH THROUGH THE AREA. ANY
-FZDZ THIS MORNING WILL BECOME -DZ AS TEMPS SNEAK ABOVE FREEZING
TODAY.

WE WILL SEE IMPROVING CONDITIONS...AND LIKELY SOME SUNSHINE FOR
FRIDAY ACROSS THE AREA. DRIER AIR WILL MOVE IN FROM THE NORTH...AND
WE WILL SEE NICE RIDGING BUILD IN OVER THE AREA AT THE SFC AND
ALOFT. CLOUDS WILL INCREASE A BIT ON SAT AS HIGH CLOUDS ON THE NRN
FLANK OF THE SYSTEM MOVING THROUGH THE SE U.S. MOVE THROUGH THE
AREA. LOWER LEVELS WILL REMAIN DRY...SO PCPN CHCS ARE QUITE LOW FOR
THE AREA ON SAT.

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 330 AM EST THU DEC 18 2014

AFTER A QUIET WEEKEND WITH HIGH PRESSURE IN CONTROL...THE WEATHER
TURNS MORE ACTIVE NEXT WEEK. A PATTERN CHANGE TOWARD COLDER AND
SHOWIER WEATHER IS LIKELY AFTER CHRISTMAS BUT THE OPERATIONAL MODELS
ARE STRUGGLING... AND WILL PROBABLY CONTINUE TO STRUGGLE... WITH HOW
SOON THAT ARRIVES AND EXACTLY HOW THINGS PLAY OUT PRIOR TO THE
ARRIVAL OF COLD AIR.

DECENT MODEL CONSISTENCY EXISTS FOR THE SYSTEM ON MONDAY INTO
TUESDAY WHICH IS A SFC LOW AND TROUGH THAT EVOLVES IN THE MN/IA
AREA THEN TRACKS SLOWLY EAST/NORTHEAST. LIGHT MIXED PRECIPITATION IS
EXPECTED TO BREAK OUT IN THE WARM ADVECTION REGIME AHEAD OF THIS
FEATURE MONDAY WITH A TRANSITION TO PRIMARILY A LIGHT RAIN EVENT BY
TUESDAY. AFTER THAT IS WHEN FCST CONFIDENCE DIMINISHES... GOING INTO
CHRISTMAS EVE AND CHRISTMAS DAY.

PREVIOUS RUNS OF THE ECMWF WHERE SHOWING A PHASING OF THE
AFOREMENTIONED SYSTEM WITH ANOTHER SYSTEM LIFTING NORTH FROM THE
GULF LEADING TO A 965 LOW OVER MI FOR CHRISTMAS. THAT SOLUTION HAS
DISAPPEARED IN THE NEW 00Z RUN WITH THE MAIN CYCLOGENESIS NOW
OCCURRING WELL TO OUR EAST. EITHER WAY... COLDER AIR AND WINDY
CONDITIONS SWEEP IN ON THE BACK SIDE OF THE SYSTEM FOR CHRISTMAS EVE
AND CHRISTMAS DAY ALTHOUGH THE AIR IS NOT PARTICULARLY COLD AND SNOW
AMOUNTS SHOULD NOT BE TOO SIGNIFICANT.

THE REALLY COLD AIR DOES NOT FOLLOW DIRECTLY BEHIND THE CHRISTMAS
LOW. IT LOOKS TO HOLD OFF UNTIL AROUND 28DEC BEHIND A POTENTIAL
SYNOPTIC SYSTEM WHICH TRACKS NE THROUGH THE OHIO VALLEY REGION. SO
WE WILL LIKELY HAVE TO WAIT UNTIL THE WEEKEND AFTER CHRISTMAS FOR
THE PERSISTENTLY COLDER AND SNOWIER WEATHER TO SETTLE IN.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1255 PM EST THU DEC 18 2014

PILOTS WILL NEED TO BE AWARE OF THE THREAT OF AIRCRAFT ICING TODAY
AND INTO TONIGHT.  SOME REPORTS OF FREEZING DRIZZLE HAVE BEEN
RECEIVED.  AND THE IN CLOUD TEMP WILL BE IN THE -8 TO -11C RANGE
BETWEEN 3000 AND 5000 FT.  THIS IS AN IDEAL RANGE FOR SUPER-COOLED
LIQUID TO EXIST WITHIN THESE CLOUDS. CLOUD TOPS ARE EXPECTED TO BE
AROUND 10,000 FT MUCH OF THE DAY...SO IT MAY BE DIFFICULT TO CLIMB
OUT OF THE ICING. CLOUD TOPS ARE NOT EXPECTED TO LOWER UNTIL
02-04Z WHEN THE ICING THREAT SHOULD DIMINISH.

MUCH OF THE REGION REMAINED UNDER MVFR CONDITIONS EARLY THIS
AFTERNOON...WITH PATCHY IFR IN LOWER CEILINGS AND FREEZING
DRIZZLE. EXPECT LITTLE OVERALL CHANGE IN CONDITIONS...ALTHOUGH THE
FREEZING DRIZZLE THREAT SHOULD END ACROSS THE I-96 TAF SITES BY
21-22Z. THIS THREAT COULD LINGER NEAR THE I-94 TAF SITES UNTIL
ABOUT 01Z.

DRIER AIR SLOWLY MOVES IN FROM THE NORTH TONIGHT AND EXPECT AN
IMPROVEMENT IN CEILINGS PRIOR TO DAYBREAK TO MOSTLY VFR.

&&

.MARINE...
ISSUED AT 1107 AM EST THU DEC 18 2014

BASED ON LATEST WEBCAMS AND WW3 GUIDANCE...CANCELLED THE SMALL
CRAFT ADVISORY.


&&

.HYDROLOGY...
ISSUED AT 316 PM EST WED DEC 17 2014

NO SIGNIFICANT IMPACTS IN HYDROLOGY EXPECTED OVER AT LEAST THE
NEXT SEVEN DAYS AND LIKELY INTO THE NEW YEAR.

&&

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

$$

UPDATE...TJT
SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...MEADE
AVIATION...JK
HYDROLOGY...MACZKO
MARINE...TJT





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