Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 162031
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
331 PM EST TUE DEC 16 2014

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

.SYNOPSIS...
ISSUED AT 331 PM EST TUE DEC 16 2014

RAIN CHANGES TO LIGHT SNOW SHOWERS TOWARD MIDNIGHT. MOSTLY LIGHT
SNOW SHOWERS WILL CONTINUE INTO THURSDAY MORNING. QUIET WEATHER
WILL RETURN LATER THURSDAY AND CONTINUE THROUGH THE WEEKEND.
TEMPERATURES WILL BE NEAR NORMAL THROUGH THIS PERIOD. ANOTHER
SIGNIFICANT PRECIPITATION EVENT IS EXPECTED EARLY NEXT WEEK. THAT
SHOULD BE RAIN CHANGING TO SNOW. COLDER WEATHER WILL FOLLOW THAT
SYSTEM.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 331 PM EST TUE DEC 16 2014

NOT MUCH HAS CHANGED IN OUR FORECAST OVER THE PAST FEW DAYS AND
MY CURRENT THINKING IS AS IT HAS BEEN FOR SEVERAL DAYS NOW. THE
COLD AIR COMES IN TONIGHT TRAILING A SECONDARY COLD FRONT. THIS
WILL CHANGE THE RAIN SHOWERS TO SNOW SHOWERS BY MIDNIGHT ACROSS
THE AREA. THE SNOW SHOWERS MAY END FOR A WHILE SOUTH OF MUSKEGON
(AFTER MIDNIGHT) BUT WILL RESUME BY MORNING AND CONTINUE INTO
THURSDAY MORNING. ACCUMUATIONS WILL BE LIGHT BUT I DO EXPECT 1 TO
3 INCHES TO FALL OVER THE 48 HOURS OF THIS EVENT.

WE HAVE A CLOSED COLD CORE UPPER LOW DROPPING SOUTHEAST THROUGH THE
AREA WITH 850 TEMPS NEAR -10C. THE SURFACE AIR COMING OFF SHORE
FROM WISCONIN SHOULD HAVE TEMPERATURES IN THE MID TO UPPER 20S
TOMORROW SO THAT SHOULD BE COLD ENOUGH TO ALLOW ENOUGH SURFACE
INSTABLTIY FOR SHALLOW CONVECTION NEEDED FOR LAKE EFFECT. THE NAM
DOES SHOW SOME LIMITED CAPE (30 TO 50 J/KG OF MOST UNSTABLE CAPE).
THE CLOUD TOPS DO REACH THE DGZ BUT JUST BARELY SO I DO EXPECT
ACCULATING SNOW FROM THIS EVENT. WINDS WILL BE WEST TO NORTHWEST
SO MOST AREAS WEST OF US-131 SHOULD SEE SOME SNOW. THIS ALL COMES
TO AN END BY THURSDAY AFTERNOON AS THAT SYSTEM MOVES OUT OF THE
AREA.



.LONG TERM...(FRIDAY THROUGH TUESDAY)
ISSUED AT 331 PM EST TUE DEC 16 2014

CANADIAN HIGH PRESSURE SHOULD DOMINATE THE EARLY PORTION OF THE
EXTENDED FORECAST.  THIS STILL APPEARS TO KEEP A STORM SYSTEM OVER
THE GULF COAST STATES FROM REACHING OUR AREA.  WE MAY DRAG DOWN
ENOUGH COOL AIR FOR SOME LIGHT LAKE EFFECT SNOW AS THE GULF COAST
SYSTEM SLIDES UP THE EAST COAST LATE IN THE WEEKEND.  BUT WITH
SURFACE HIGH PRESSURE STILL NEARBY THESE WILL PROBABLY NOT END TO BE
MUCH MORE THAN JUST FLURRIES.

WE SHOULD BEGIN TO WARM ADVECTION SUNDAY NIGHT AS WE GET ON THE BACK
SIDE OF THE HIGH.  MAX TEMPS SHOULD INCH UP INTO THE 30S OR APPROACH
40 FOR MON/TUE.  GOOD AGREEMENT IN THE MODELS SHOWING A NORTHERN
STREAM SYSTEM DEVELOPING ACROSS THE PLAINS IN THIS TIME FRAME.  IT
APPEARS A COLD FRONT SHOULD ARRIVE TUESDAY OR TUESDAY NIGHT.  MIXED
PCPN COULD ARRIVE AS EARLY AS MONDAY AFTERNOON AND LINGER THROUGH
TUESDAY.  HOWEVER TEMP REGIMES SUGGEST ANY MIX SHOULD LARGELY TURN
TO JUST A COLD RAIN BY TUESDAY

&&

.WEEK TW0...(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 MICHGIAN 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 MEMEMBER ECMWF ENSMEBLE AND CFSV2
SHOW THE LAST WEEK OF DECEMBER AND THE FIRST FULL WEEK OF JANUARY
5 TO 10 DEGEREES 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 ENSEMLBE...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 NEED TO SET UP THE
SLOWER MOVING LONGWAVE PATTERN.


&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1231 PM EST TUE DEC 16 2014

THE ENTIRE AREA REMAINED UNDER IFR OR LIFR CONDITIONS AS OF 17Z.
EXPECT ONLY A SLOW IMPROVE IN THIS. COLDER AIR AND STRONGER WINDS
WILL ARRIVE EARLY THIS EVENING...AND ALONG WITH THESE FACTORS...
THE IFR SHOULD ALSO IMPROVE INTO THE EVENING. EXPECT THAT MOST OF
THE IFR WILL LIFT TO MVFR AROUND 06Z.

AS THE COLDER AIR CONTINUES TO POUR IN...LAKE EFFECT SNOW SHOWERS
SHOULD DEVELOP LATE TONIGHT/EARLY WEDNESDAY MORNING. THE MEAN LOW
LEVEL FLOW WILL BE 290-300 WHICH FAVORS AZO SEEING THE BEST CHANCE
OF SNOW SHOWERS WITH SOME IFR REDEVELOPING. MKG...GRR...AND BTL
MAY ALSO SEE SOME SNOW SHOWERS INTO WED MORNING.


&&

.MARINE...
ISSUED AT 331 PM EST TUE DEC 16 2014

NORTHWEST WINDS TO 30 KNOTS WILL CONTINUE THROUGH MOST OF
WEDNESDAY SO I WILL CONTINUE THE SMALL CRAFT ADVIOSRY AS IS. WINDS
ARE JUST COMING AROUND TO THE NORTHWEAST AS I WRITE THIS AND BY 7
PM I WOULD EXPECT TO SEE THE WINDS IN THE 20 TO 30 KNOT RANGE
ACROSS OUR NEAR SHORE AREA. THE STRONGEST WINDS WILL BE BETWEEN 7
PM TONIGHT AND 7 AM WEDNESDAY...THERE IS 30 TO 35 KNOTS IN THE
MIXED LAYER DURING THAT TIME. IT IS POSSIBLE SOME HIGHER GUSTS TO
GALE FORCE MAY OCCUR EARLY THIS EVENING AS THE COLD AIR STARTS TO
COME IN BUT IF IT DOES HAPPEN IT WILL BE BRIEF AND ISOLATED.

&&

.HYDROLOGY...
ISSUED AT 331 PM EST TUE DEC 16 2014

NO HYDRO IMPACTS EXPECTED OVER THE NEXT WEEK. 24 HOUR OBSERVED
RAINFALL TOTALS THROUGH TUESDAY MORNING WERE ALL LESS THAN A QUARTER
INCH. SMALL RISES CAN BE EXPECTED ON SMALLER RIVERS AND CREEKS...BUT
NOTHING MORE. ANY LIGHT PRECIP WILL CHANGE TO SNOW TONIGHT.

&&

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

&&

$$

SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...JK
AVIATION...JK
HYDROLOGY...EBW
MARINE...WDM






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