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000
FXUS63 KGRR 052333
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
633 PM EST THU DEC 5 2013

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 334 PM EST THU DEC 5 2013

COLDER AIR WILL CONTINUE TO MOVE INTO SOUTHWEST MICHIGAN INTO THE
WEEKEND. EXPECT SNOW FLURRIES WEST OF US-131 TONIGHT INTO FRIDAY
THEN SNOW SHOWERS WITH AN INCH OR TWO OF ACCUMULATION FRIDAY NIGHT INTO
SATURDAY. INLAND IT WILL STAY BELOW FREEZING THROUGH SATURDAY.

A STORM SYSTEM WILL BRING SOME SNOW TO THE AREA SUNDAY NIGHT INTO
MONDAY THEN THE COLDEST AIR OF THE SEASON WITH ADDITIONAL LAKE
EFFECT SNOW IS EXPECTED TUESDAY INTO WEDNESDAY.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT)
ISSUED AT 334 PM EST THU DEC 5 2013

WE ARE WATCHING TO SEE IF LAKE EFFECT SNOW SHOWERS CAN DEVELOP IN
THIS DRY WESTERLY FLOW TONIGHT INTO FRIDAY AS THE COLDER AIR
CONTINUES TO MOVE INTO SOUTHWEST MICHIGAN. SEEMS THE MOST LIKELY
TIME FOR ACCUMULATING SNOW IN THE LAKE SHORE AREAS IS FRIDAY
EVENING INTO SATURDAY MORNING. ANOTHER LESSER ISSUE IS THE TWO
JET LIFT RELATED SNOW EVENT PASSING OFF TO OUR SOUTH...THE FIRST
ONE TONIGHT AND THE SECOND ONE FRIDAY AFTERNOON.

THE MODELS HAVE BEEN VERY CONSISTENT ON THIS EVENT FOR MANY DAYS
NOW. SHALLOW COLD AIR LIMITING LAKE EFFECT SNOWS. THE 850 MB TEMPS
FALLS TO AROUND -10C BY FRIDAY MORNING AND -15C BY SATURDAY
MORNING. THAT IS MORE THAN ENOUGH FOR LAKE EFFECT SNOW SHOWERS
GIVEN THE 5-6C LAKE TEMPS. HOWEVER THE POLAR JET CORE IS NOT SOUTH
OF MICHIGAN SO WE ARE ONLY IN SHALLOW COLD AIR (INVERSION HEIGHTS BELOW
4000 FT AGL) THROUGH FRIDAY AFTERNOON. OVER TIME... AS THE JET CORE
SLIPS EAST FRIDAY INTO FRIDAY NIGHT THE INVERSION HEIGHTS DO
FINALLY INCREASE TO NEAR 5000 FT AGL. THAT IS STILL NOT GOOD BUT
SHOULD BE ENOUGH FOR SOME LAKE EFFECT SNOW SHOWERS TO GET GOING.
ALSO THERE IS THE ISSUE OF A SEEDER FEEDER EVENT OVER THE SOUTHERN
LAKE SHORE FRIDAY EVENING AS THE SECOND SNOW EVENT PASSES LARGELY
SOUTH OF HERE BUT THE MID CLOUDS WILL BE PASSING OVER THE SOUTHERN
CWA SO THAT MAY HELP THE CAUSE OF ACCUMULATING SNOW. THERE IS
DECENT LIFT IN THE DGZ FRIDAY NIGHT INTO SATURDAY MORNING EVEN
THROUGH THE INVERSION HEIGHTS STAY BELOW 5000 FT AGL. ALL IN ALL I
CAN SEE 1 TO 2 INCHES OF SNOW FALLING WEST OF US-131 FRIDAY NIGHT
AND MAYBE ANOTHER INCH SATURDAY MORNING.

ENOUGH DRY AIR MOVES IN HEAD OF THE NEXT SYSTEM TO END THE LAKE
EFFECT EVENT SATURDAY EVENING. IT WILL REMAIN COLD HOWEVER.

.LONG TERM...(SUNDAY THROUGH THURSDAY)
ISSUED AT 334 PM EST THU DEC 5 2013

CONSISTENCY REMAINS GOOD WITH THE SYSTEM EXPECTED TO IMPACT SW MI
EARLY NEXT WEEK.  THEREFORE ONLY MINOR TWEAKS WERE MADE TO THE
FORECAST.

CYCLOGENESIS DEVELOPS OVER THE WESTERN GULF EARLY SUNDAY AS AN
ARCTIC JET STREAM PLUNGES INTO THE CENTRAL ROCKIES.  THE SURFACE LOW
IS SHOWN TO CONTINUE TO MOVE NNE TOWARD THE GREAT LAKES BY EARLY
MONDAY.  THE LOW APPEARS A BIT WEAKER AND ALSO A BIT FURTHER
WEST...PASSING DIRECTLY OVER THE LOWER PENINSULA.  PCPN TYPE SHOULD
STILL BE ALL SNOW FOR SW MI...BUT THE HEAVIEST MAY OCCUR OFF TO OUR
WEST.  RIGHT NOW THIS LOOKS LIKE A 1-4 INCH TYPE SNOWFALL...HEAVIEST
OVER THE NW CWA.

THE ARCTIC BLAST FOLLOWS THIS SYSTEM BY MONDAY NIGHT AND LINGERS
THROUGH WEDNESDAY NIGHT.  H8 TEMPS ARE PROGGED TO BE AROUND -20C
WHICH IS QUITE SIGNIFICANT FOR THIS TIME OF YEAR.  DAYTIME TEMPS
SHOULD STRUGGLE TO REACH 20 WITH NIGHTTIME LOWS AROUND 10 ABOVE.
WIND CHILL READINGS SHOULD FALL BELOW ZERO AT TIMES FROM LATE MONDAY
NIGHT UNTIL EARLY THURSDAY MORNING...A SIGNIFICANT ARCTIC COLD BLAST
FOR SURE.  THIS ARCTIC AIR MASS SHOULD SUPPORT OCCASIONAL LAKE
EFFECT SNOW SHOWERS MONDAY NIGHT THROUGH WEDNESDAY.  TEMPS SHOULD
MODERATE A BIT ON THURSDAY AS HIGH PRESSURE MOVES INTO THE OH VALLEY
AND RETURN FLOW MOVES IN.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 629 PM EST THU DEC 5 2013

STRATOCUMULUS HAS HUNG AROUND THROUGH THIS EVENING AND AM GOING TO
CARRY THAT THROUGH THE TAFS INTO THE LATE NIGHT PERIOD AND
TOMORROW. SHOULD SEE SOME SLIGHTLY LOWER CIGS DEVELOP AT
MKG/GRR/AZO BY EARLY TO MID MORNING AS ADDITIONAL CLOUD COVER
EXPECTED TO GENERATE OFF LAKE MICHIGAN ALONG WITH A FEW SNOW
SHOWERS DEVELOPING. NOT EXPECTING ANY IFR CONDITIONS THROUGH 00Z
SATURDAY.

&&

.MARINE...
ISSUED AT 334 PM EST THU DEC 5 2013

WINDS WILL REMAIN STRONG ENOUGH TO KEEP THE LAKE SMALL CRAFT
ADVISORY GOING INTO FRIDAY AFTERNOON AND IT MAY HAVE TO BE
CONTINUED INTO SATURDAY AFTERNOON SINCE THE WINDS MAY NOT REALLY
DIMINISH ENOUGH INTO SATURDAY EVENING TO GET THE WAVE HEIGHTS
BELOW 4 FEET.


&&

.HYDROLOGY...
ISSUED AT 334 PM EST THU DEC 5 2013

WE WILL HAVE TO MONITOR RIVER ICE NEXT WEEK AS THE BELOW FREEZING
TEMPERATURES CONTINUE. RIVER ICE BUILDS UP MORE QUICKLY IF
AFTERNOON TEMPERATURES STAY IN THE 20S... WHICH IS WHAT WE ARE
FORECASTING NEXT WEEK.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 3 PM EST FRIDAY FOR LMZ844>849.

&&

$$

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