Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 181940
AFDGRR

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

LATEST UPDATE...
SYNOPSIS/SHORT TERM/HYDRO/MARINE

.SYNOPSIS...
ISSUED AT 240 PM EST THU DEC 18 2014

LIGHT SNOW AND FREEZING DRIZZLE ARE EXPECTED TO DIMINISH OVERNIGHT.
QUIET WEATHER IS EXPECTED THROUGH THE WEEKEND WITH SOME SUN ON
FRIDAY. HIGHS WILL BE IN THE 30S OVER THE WEEKEND WITH A WARM UP
INTO THE LOWER 40S EARLY NEXT WEEK.

UNSETTLED WEATHER IS EXPECTED NEXT WEEK...WITH MULTIPLE
OPPORTUNITIES FOR BOTH RAIN AND SNOW.  RAIN OR SNOW WILL BE POSSIBLE
BEGINNING SUNDAY AFTERNOON INTO SUNDAY NIGHT. THEN A PERIOD OF RAIN
IS EXPECTED MONDAY AND TUESDAY. COLDER AIR SHOULD ARRIVE ABOUT
TUESDAY NIGHT WHICH SHOULD CHANGE THE PRECIPITATION TO SNOW WHICH
SHOULD CONTINUE INTO CHRISTMAS DAY.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT)
ISSUED AT 240 PM EST THU DEC 18 2014

MAIN CONCERN IS DRIZZLE/FREEZING DRIZZLE THIS AFTERNOON LASTING INTO
THE EVENING. SURFACE BOUNDARY HAS STALLED ROUGHLY ALONG A HOLLAND TO
GRAND RAPIDS TO LANSING LINE. TEMPERATURES SOUTH OF THIS BOUNDARY
HAVE BEEN SLOW TO RISE...BUT EXPECT A SLOW CLIMB ABOVE FREEZING THE
REST OF THIS AFTERNOON. SHORT RANGE GUIDANCE INCLUDING THE HRRR
SHOWS THE BOUNDARY DROPPING SOUTH TO I-94 BY 10 PM. THERE IS A
NARROW WINDOW FOR FREEZING DRIZZLE AGAIN THIS EVENING AS
TEMPERATURES BEGIN TO FALL. PRECIPITATION IS MOST LIKELY TO OCCUR
OVER FAR SOUTHWEST LOWER MICHIGAN WHERE SPEED CONVERGENCE OF WINDS
OFF LAKE MICHIGAN WILL SUPPLEMENT BOUNDARY CONVERGENCE. LIGHT SNOW
WILL ALSO CONTINUE TO BE POSSIBLE EARLY TONIGHT IN THE VICINITY OF
THE BOUNDARY.

OTHERWISE NO SIGNIFICANT WEATHER IS EXPECTED THROUGH SATURDAY NIGHT
WITH HIGH PRESSURE IN CONTROL.

.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 240 PM EST THU DEC 18 2014

NO CONCERNS AT THIS TIME. WINDS AND WAVES WILL CONTINUE TO SUBSIDE
THIS EVENING AND STAY LOW INTO THE WEEKEND WITH HIGH PRESSURE IN
CONTROL.

&&

.HYDROLOGY...
ISSUED AT 240 PM EST THU DEC 18 2014

NO SIGNIFICANT HYDRO IMPACTS EXPECTED FOR THE FORESEEABLE FUTURE.

&&

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

$$

SYNOPSIS...EBW/JK
SHORT TERM...TJT
LONG TERM...MEADE
AVIATION...JK
HYDROLOGY...EBW
MARINE...TJT






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