Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 171748
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1248 PM EST WED DEC 17 2014

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 330 AM EST WED DEC 17 2014

COLDER AIR AND GUSTY WINDS HAVE FOLLOWED A LOW THAT IS MOVING EAST
TOWARD THE ATLANTIC. LIGHT LAKE EFFECT SNOW SHOWERS WILL BE POSSIBLE
TODAY AND TONIGHT BUT ACCUMS WILL MAINLY BE LIMITED TO AROUND AN
INCH OR LESS...MAINLY WEST OF US-131. TEMPS WILL REMAIN IN THE LOWER
30S THROUGH SATURDAY BEFORE WARMING A BIT AS WE HEAD INTO NEXT WEEK.

&&

.UPDATE...
ISSUED AT 1105 AM EST WED DEC 17 2014

NO SIGNIFICANT CHANGES TO THE FORECAST THIS MORNING.

FLURRIES WITH OCCASIONAL LIGHT DRIZZLE MIXED IN WILL CONTINUE OFF
AND ON THROUGH THE DAY..ESPECIALLY NORTH OF INTERSTATE 94. MAIN
FORCING FOR EXISTING PRECIPITATION MOVES OFF THIS AFTERNOON AND
EVENING MOVING ANY LINGERING SNOW OUT OF MOST OF LOWER MICHIGAN
TONIGHT...WITH THE LAKE SHORE CONTINUING TO SEE SOME LIGHT SNOW
SHOWERS THROUGH THURSDAY. BREEZY CONDITIONS TO PERSIST THROUGH
THIS EVENING AS WELL WITH A GRADUAL DIMINISHING OF WINDS
OVERNIGHT.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 330 AM EST WED DEC 17 2014

FORECAST CONCERNS DEAL WITH LAKE EFFECT SNOW CHANCES TODAY AND
TONIGHT.

WINDS HAVE BEEN GUSTY OVERNIGHT AS COLD AIR POURS INTO LOWER
MICHIGAN BEHIND THE DEPARTING LOW. LIGHT SYNOPTIC SNOW CONTINUES
MAINLY OVER NORTHERN LOWER ATTM AS THE UPPER LOW ROTATES INTO THE
STATE. MODELS CONTINUE TO SHOW H8 TEMPS NEAR -12C MOVING ACROSS THE
LAKE TODAY. THAT NORMALLY CREATES ENOUGH INSTABILITY FOR SHSN. THE
ISSUE TODAY THOUGH IS THE MEAGER DGZ. THE MODELS HAVE BEEN PRETTY
CONSISTENT SHOWING THE DGZ HUGGING THE TOP OF THE CLOUD LAYER AROUND
4K FT. IT DOESN/T LOOK TO ME THAT THE DGZ IS SUFFICIENTLY DEEP TO
PRODUCE DECENT SNOWFLAKES. WE/LL PROBABLY GET SOME BUT I/M
COMPLETELY UNDERWHELMED BY THIS SETUP. AS SUCH I/VE CUT BACK ON POPS
A BIT TODAY AND TONIGHT BUT STILL RETAINED THE HIGHEST VALUES WEST
OF US-131. THE BOUNDARY LAYER COLD AIR BAILS LATE THURSDAY AND SO
WHATEVER LAKE EFFECT SNOW IS STILL GOING SHOULD WIND DOWN TO
FLURRIES.

HIGHS DURING THE NEXT FEW DAYS WILL BE QUITE A BIT COLDER THAN WE/VE
SEE LATELY WITH LOWER 30S EXPECTED.

.LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY)
ISSUED AT 330 AM EST WED DEC 17 2014

BENIGN WEATHER WITH SLIGHTLY ABOVE NORMAL TEMPERATURE IS EXPECTED
THIS WEEKEND INTO EARLY NEXT WEEK AS A SFC RIDGE OF HIGH PRESSURE
DOMINATES OUR WEATHER. THE PATTERN TURNS MORE ACTIVE BY NEXT TUESDAY
AS A LONGWAVE TROUGH TAKES SHAPE OVER THE CENTER OF THE NATION. WARM
ADVECTION/ISENTROPIC LIFT AHEAD OF A DEVELOPING LOW OVER THE CENTRAL
PLAINS BRINGS A THREAT OF LIGHT MIXED RAIN AND SNOW MONDAY NIGHT
WHICH LOOKS TO CHANGE TO MOSTLY ALL RAIN ON TUESDAY AS GUIDANCE
SHOWS HIGHS NEAR 40.

LOOKING FARTHER AHEAD.. PRESENT INDICATIONS ARE FOR A LOW TO LIFT
NORTH FROM THE GULF COAST ON TUESDAY NIGHT AND WEDNESDAY... THEN
DEEPEN AND OCCLUDE OVER THE GREAT LAKES REGION ON CHRISTMAS EVE. THE
00Z ECMWF SOLUTION OF A 965 LOW OVER THE THUMB BY CHRISTMAS MORNING
SUPPORTS QUITE A BIT OF WIND WITH RAIN CHANGING TO SNOW. HOWEVER
THIS POTENTIAL SYSTEM IS STILL A WEEK OUT IN TIME SO CONFIDENCE ON
THE SPECIFICS IS LOW AND WE WILL LIKELY SEE VARYING SOLUTIONS OVER
TIME.

WEEK TWO...(WEDNESDAY THROUGH TUESDAY)
ISSUED AT 331 PM EST TUE DEC 16 2014

WINTER TYPE WEATHER WILL DOMINATE THE LAST WEEK OF DECEMBER OVER
ALL OF SOUTHWEST LOWER MICHIGAN. AT THIS POINT THERE ARE SOME
INDICATIONS SNOW MAY FALL ON CHRISTMAS DAY (MOST OF THE
OPERATIONAL MODELS TO GIVE SOUTHWEST MICHIGAN SNOW ON CHRISTMAS
BUT EACH HAS A SLIGHTLY DIFFERENT REASON FOR THAT TO HAPPEN). THE
TIMING OF THE RETURN OF THE REALLY COLD AIR HAS SOME VARIANCE FROM
MODEL RUN TO MODEL RUN OVER THE PAST WEEK BUT ALL OF THE MODELS
AGREE THAT BY AROUND THE 28TH IT WILL GET COLD AND STAY THAT WAY
INTO THE NEW YEAR. BOTH THE 51 MEMBER ECMWF ENSEMBLE AND CFSV2
SHOW THE LAST WEEK OF DECEMBER AND THE FIRST FULL WEEK OF JANUARY
5 TO 10 DEGREES BELOW NORMAL. THE PATTERN FAVORS LAKE EFFECT SNOW
EVENTS OVER SYNOPTIC SNOWFALL EVENTS. AREAS NEAR LAKE MICHIGAN
WOULD GET THE MOST SNOW WITH THIS SETUP.

BASED ON THE ECMWF 51 MEMBER 32 DAY ENSEMBLE...THE CFSV2 5 DAY
MEAN TEMPERATURE FORECASTS...THE OPERATIONAL RUNS OF THE
GFS...ECWMF...THE FIM ZEUS AND THE PARALLEL GFS ALL TURN TOWARD
MUCH COLDER TEMPERATURES IN AND AROUND CHRISTMAS. IT SEEMS A SYSTEM
CURRENTLY COMING OFF THE AREA OF ASIA NEAR KOREA... CROSSES THE
PACIFIC OVER THE NEXT WEEK...REACHING THE GULF OF ALASKA BY
SUNDAY. IT IS THAT POINT IT STARTS BUILDING AND UPSTREAM RIDGE
OVER THE WESTERN UNITED STATES AND THAT RESULTS IN THE DOWN STREAM
TROUGH WHICH IN TURN BRINGS THE COLD AIR BACK. UNLIKE THE LAST
WEEK OR TWO WE DO NOT HAVE A STRONG EXTENDED EAST ASIAN JET BEHIND
THIS SYSTEM TO THAT GIVES THE WAVELENGTH NEEDED TO SET UP THE
SLOWER MOVING LONGWAVE PATTERN.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1248 PM EST WED DEC 17 2014

MVFR CEILINGS PREVAILED ACROSS THE ENTIRE REGION EARLY THIS
AFTERNOON. THIS WILL CONTINUE...HOWEVER LATER THIS AFTERNOON OR
TOWARD EVENING AN UPPER LEVEL DISTURBANCE WILL CROSS LAKE MICHIGAN
AND WILL PERK UP LAKE EFFECT SNOW SHOWERS. THESE SHOULD GET GOING
AROUND 21Z WITH POCKETS OF IFR VSBYS DEVELOPING. THE FLOW FAVORS
AZO HAVING THE MOST IMPACT...BUT MKG...GRR...AND BTL WILL ALSO SEE
OCCASIONAL IFR VSBYS. THE DISTURBANCE MOVES EAST BY AROUND 03Z
WHEN THE SNOW SHOWERS SHOULD LET UP AND A RETURN TO MOSTLY MVFR
CONDITIONS. MVFR IS EXPECTED TO BE MAINTAINED THROUGH 18Z THU.

WEST NORTHWEST SURFACE WINDS WILL REMAIN BRISK...GUSTING TO 20-25
KNOTS THROUGH THE AFTERNOON...BUT THEN DIMINISH BY LATE EVENING.
LIGHTER WINDS ARE EXPECTED TO CONTINUE INTO THURSDAY.

&&

.MARINE...
ISSUED AT 330 AM EST WED DEC 17 2014

NO CHANGES TO THE SCA. GUSTY NW WINDS WILL CONTINUE INTO THURSDAY
RESULTING IN 5 TO 10 FT WAVES.


&&

.HYDROLOGY...
ISSUED AT 330 AM EST WED DEC 17 2014

NO HYDRO ISSUES.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL NOON EST THURSDAY FOR LMZ844>849.

&&

$$

UPDATE...MACZKO
SYNOPSIS...93
SHORT TERM...93
LONG TERM...MEADE
AVIATION...JK
HYDROLOGY...93
MARINE...93






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