000
FXUS63 KGRR 042055
AFDGRR

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

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

.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.

&&

.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 355 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
THIS TYPE AIR MASS THIS EARLY IN THE WINTER SEASON WAS IN 2008...AND
CLIMATE DATA SUPPORTS THAT WE ONLY SEE THIS ABOUT ONCE EVERY FIVE TO
TEN YEARS.




&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1257 PM EST WED DEC 4 2013

WIDESPREAD IFR/LIFR COVERED THE REGION EARLY THIS AFTERNOON IN FOG
AND RAIN SHOWERS ALONG WITH LOW CEILINGS. EXPECT CONDITIONS WILL
SLOWLY IMPROVE THROUGH THE AFTERNOON AS MORE MIXING OCCURS AND A
STEADIER RAIN MOVES IN. HOWEVER...MOST AREAS WILL ONLY IMPROVE TO
IFR...WITH A FEW POCKETS OF MVFR.

A COLD FRONT WILL BE PUSHING THROUGH THE AREA TOWARD MIDNIGHT.
PRIOR TO THIS MOVING IN MORE WIDESPREAD IFR/LIFR IS EXPECTED FOR
MUCH OF THE EVENING HOURS. HOWEVER...ONCE THE FRONT IS THROUGH
CONDITIONS WILL STEADILY IMPROVE AFTER MIDNIGHT. THE RAIN WILL END
AND CONDITIONS SHOULD IMPROVE TO MOSTLY MVFR BY ABOUT 09Z AND
REMAIN THERE INTO MID DAY THU.

WINDS WILL GRADUALLY INCREASE BY THIS EVENING AS THE FRONT
APPROACHES. INITIALLY THEY WILL BE FROM THE SOUTH AROUND 15 KTS...BUT
THEN TURN TO THE WEST SOUTHWEST AFTER MIDNIGHT.


&&

.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 FROM 7 PM THIS EVENING TO 3 PM EST FRIDAY FOR
     LMZ847>849.

     SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 3 PM EST FRIDAY
     FOR LMZ844>846.

&&

$$

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