000
FXUS63 KGRR 050452
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1152 PM EST WED DEC 4 2013

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 355 PM EST WED DEC 4 2013

EXPECT SHOWERS WITH THE COLD FRONT TONIGHT THEN BREEZY AND COLDER
THURSDAY WITH A FEW FLURRIES. LAKE EFFECT SNOW SHOWERS AND COLDER
TEMPERATURES ARE EXPECTED THURSDAY NIGHT INTO SATURDAY. A SNOW
STORM IS EXPECTED LATE SUNDAY INTO MONDAY. THAT WILL BE FOLLOWED
BY THE COLDEST DECEMBER HIGH TEMPERATURES SINCE 2008 WITH
ADDITIONAL LAKE EFFECT SNOW SHOWERS INTO MIDWEEK.

&&

.UPDATE...
ISSUED AT 801 PM EST WED DEC 4 2013

WE HAVE GONE AHEAD AND UPDATED THE FCST TO LOWER RAIN CHCS
A BIT QUICKER THAN EARLIER ANTICIPATED. BAND OF SHOWERS AND
ISOLATED STORMS HAVE RAPIDLY PUSHED NORTH AND EAST OF THE CWFA
ALONG WITH THE SUPPORTING SHORT WAVE. SOME LIGHT DRIZZLE/A COUPLE
OF SHOWERS ARE FLOATING AROUND OUT THERE...HOWEVER THERE IS NOT
MUCH OF ANY CONSEQUENCE IN OUR CWFA OR ACROSS THE LAKE OVER IN WI
AND IL AHEAD OF THE COLD FRONT. UNTIL THE COLD FRONT MOVES
THROUGH...THE CHC WILL EXIST. HOWEVER THE BETTER THREAT OF ANY
ADDITIONAL RAINFALL WILL BE WELL NORTH OF THE AREA WHERE THE UPPER
WAVES WILL NOW BE LOCATED.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY NIGHT)
ISSUED AT 355 PM EST WED DEC 4 2013

THE MAIN ISSUE THAT IS SEE THE POTENTIAL FOR LAKE EFFECT SNOW
SHOWERS THURSDAY NIGHT INTO FRIDAY NIGHT AS THE COLD AIR COMES IN
ON WEST WINDS. THE FOG OVER THE NORTHERN CWA SHOULD QUICKLY LIFT
OUT THIS EVENING AS THE WARM FRONT SURGES NORTH.

SO FAR THE FORECAST IS LARGELY ON TRACK. SHOWERS WILL INCREASE
ACROSS THE AREA THIS EVENING AS THE COLD FRONT HEADS INTO THE
AREA. THE PROBLEM THOUGH IS THERE IS LIMITED MID LEVEL MOISTURE SO
EVEN THROUGH THERE IS A 50 KNOT LOW LEVEL JET THAT MOVES INTO
CENTRAL LOWER MICHIGAN THIS EVENING THE DARTH OF MOISTURE WILL
LIMIT WIDESPREAD SHOWERS. HOWEVER WHAT SHOWERS DO DEVELOP WILL BE
CONVECTIVE SO SOME BRIEF HEAVY RAIN IS POSSIBLE. SEEMS THE
INSTABILITY IS TO LIMITED FOR THUNDERSTORMS SO I AM NOT EXPECTING
THAT.

WE GET THE DRY SLOT BEHIND THE COLD COLD FRONT THURSDAY DURING THE
DAY. EVEN SO THE AIR BECOMES COLD ENOUGH FOR LAKE EFFECT SNOW
SHOWERS BY MIDDAY. SO I PUT LIGHT SNOW SHOWERS NEAR THE LAKE SHORE
AND CALLED THAT GOOD. MORE THAN ANYTHING IT WILL BE BREEZY WITH
SLOWLY FALLING TEMPERATURES ALL DAYS. WINDS COULD GUST TO 30 TO 35
MPH AT TIMES.

NOW THE TRICKY PART OF THE FORECAST. AS THE CORE OF THE COLD AIR
COMES IN THE INVERSION LEVELS ARE BELOW 5000 FT... HOWEVER THE DGZ
IS IN THE MOIST LAYER AND THERE IS LIFT IN THAT LIMITED MOIST
LAYER. ALSO BY FRIDAY EVENING WE HAVE THETA E DECREASING WITH
HEIGHT NEAR THE LAKE SHORE IN THE O TO 2 KM LAYER AND THERE IS
SOME AROUND 50 J/KG OF CAPE IN THAT SATURATED LAYER. ALSO OVER
THE SOUTHERN SECTIONS THERE IS SEEDER FEEDER EVENT AS SOME MID
LEVEL MOISTURE MOVES ACROSS THE SOUTHERN CWA FRIDAY INTO FRIDAY
EVENING. SO MY SPIN IS IT WILL SNOW WEST OF US-131 DUE TO THE
WEST WINDS. THIS WILL NOT BE A HEADLINE EVENT BUT STILL SOME MINOR
ACCUMULATIONS SHOULD BE EXPECTED.

.LONG TERM...(SATURDAY THROUGH WEDNESDAY)
ISSUED AT 520 PM EST WED DEC 4 2013

A COLD PERIOD CAN BE EXPECTED FOR THE LONG TERM...ALONG WITH THE
POTENTIAL OF A DECENT SYNOPTIC SNOW FROM SUNDAY AFTERNOON INTO
MONDAY MORNING.

MUCH OF THE WEEKEND LOOKS QUIET AND CHILLY AS HIGH PRESSURE MOVES
FROM THE UPPER MIDWEST ON SATURDAY TO QUEBEC BY SUNDAY.  WE WILL SEE
A PERIOD OF WARM ADVECTION BY SATURDAY NIGHT AS THE HIGH MOVES
EAST...SO HIGHS WILL WARM A BIT ON SUNDAY.

HOWEVER...BY SUNDAY WE SHOULD SEE A STRONG ARCTIC JET PLUNGE DOWN
THE WESTERN U.S.  THIS WILL CARVE OUT A DEEPENING UPPER LONG WAVE
TROUGH OVER THE HIGH PLAINS WHICH IN TURN PRODUCES CYCLOGENESIS OVER
THE WESTERN GULF.  THE MODELS ARE IN GOOD AGREEMENT BRINGING THE
SURFACE LOW TOWARD THE LOWER GREAT LAKES BY SUNDAY NIGHT AND
INTENSIFYING THE LOW AS IT MOVES NE ACROSS THE EASTERN LOWER
PENINSULA.  THIS COULD SPELL A DECENT SNOWFALL FROM MUCH OF THE
CWA...HIGHEST NW...ALONG WITH INCREASING WINDS INTO MONDAY.

ANOTHER BLAST OF ARCTIC AIR FOLLOWS FOR MONDAY NIGHT AND LASTING
THROUGH WEDNESDAY.  H8 TEMPS ARE PROGGED TO BE -18C TO -20C.  ALONG
WITH WEST NORTHWEST FLOW THIS COLD AIR WILL BE ACCOMPANIED BY
PERIODIC SNOW SHOWERS.  THIS PERIOD LOOKS PARTICULARLY BRUTAL FOR
EARLY/MID DEC WITH LOWS AROUND 10 AND HIGHS MAINLY 15 TO 20.  WIND
CHILL READINGS SHOULD OCCASIONALLY BE BELOW ZERO.  THE LAST WE SAW
HIGH TEMPS HOLD IN THE TEENS THIS EARLY IN THE WINTER SEASON WAS IN
2000...AND CLIMATE DATA SUPPORTS THAT WE ONLY SEE THIS ABOUT ONCE
EVERY 20 YEARS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1150 PM EST WED DEC 4 2013

CONDITIONS HAVE IMPROVED TO VFR IN MOST PLACES THIS EVENING BUT
EXPECT SOME MVFR CEILINGS IN THE 1500 TO 2500 FEET RANGE AT TIMES
TONIGHT. ONLY LIGHT SCATTERED SHOWERS WILL BE AROUND BUT SOUTHWEST
WINDS WILL GUST OVER 20 KNOTS AT TIMES...CONTINUING THROUGH
THURSDAY WHILE GOING WEST. SOME LAKE EFFECT SNOW SHOWERS WILL
DEVELOP THURSDAY AFTERNOON SO SOME AREAS OF MVFR AND EVEN IFR ARE
POSSIBLE ACROSS WESTERN LOWER MICHIGAN BY LATE AFTERNOON.

&&

.MARINE...
ISSUED AT 355 PM EST WED DEC 4 2013

WITH THE WINDS INCREASING TO NEAR GALES OVER THE NORTHERN SECTION
OF THE NEAR SHORE THIS EVENING I ISSUED A GALE WARNING THROUGH
THURSDAY. ELSEWHERE EXPECT WINDS TO 30 KNOTS AND WAVES TO 8 FEET
SO I HAVE A SMALL CRAFT ADVISORY FOR THAT. WINDS SHOULD DIMINISH
THURSDAY EVENING.


&&

.HYDROLOGY...
ISSUED AT 355 PM EST WED DEC 4 2013

WE WILL BE WATCHING FOR ICE JAMS NEXT WEEK AS THE COLD AIR
PERSISTS AND WE ALREADY HAD A PROBLEM ON THE MUSKEGON RIVER LAST
WEEK. WE WILL BE WATCHING RIVER WATER TEMPERATURES OVER THE NEXT
FEW DAYS TO SEE HOW THIS PLAYS OUT.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...GALE WARNING UNTIL 3 PM EST FRIDAY FOR LMZ847>849.

     SMALL CRAFT ADVISORY UNTIL 3 PM EST FRIDAY FOR LMZ844>846.

&&

$$

UPDATE...NJJ
SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...JK
AVIATION...OSTUNO
HYDROLOGY...WDM
MARINE...WDM