Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 181504
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1004 AM 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.

&&

.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 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 1004 AM 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 MID
EVENING.

WIDESPREAD OVC STRATUS DECK WITH BASES OF 1500-2500 FT AND TOPS
AROUND 5000 FT EXPECTED TODAY ALONG WITH A FEW FLURRIES OR
PERHAPS A BIT OF DRIZZLE. ANY PRECIPITATION THAT OCCURS SHOULD BE
VERY LIGHT WITH NO SIGNIFICANT REDUCTIONS TO VISIBILITIES
ANTICIPATED. CIGS SHOULD IMPROVE TO VFR LATE TONIGHT AS DRIER AIR
ARRIVES FROM THE NORTH.

&&

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

HAZARDOUS WINDS AND WAVES CAN BE EXPECTED ON LAKE MICHIGAN THROUGH
EARLY THURSDAY. CONDITIONS THURSDAY AFTERNOON THROUGH AT LEAST THE
EARLY PART OF NEXT WEEK ARE EXPECTED TO BE FAIRLY QUIET.


&&

.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...SMALL CRAFT ADVISORY UNTIL NOON EST TODAY FOR LMZ844>849.

&&

$$

SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...MEADE
AVIATION...MEADE
HYDROLOGY...MACZKO
MARINE...MACZKO









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