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000
FXUS63 KGRR 101145
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
645 AM EST TUE DEC 10 2013

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 329 AM EST TUE DEC 10 2013

COLD AND SNOWY CONDITIONS ARE ANTICIPATED FOR THE REST OF THE WEEK
AS SEVERAL ROUNDS OF LAKE EFFECT AND LAKE ENHANCED SNOW IMPACT LOWER
MICHIGAN. SOME LOCATIONS DOWNWIND OF LAKE MICHIGAN THROUGH THURSDAY
WILL SEE SNOWFALL AMOUNTS ON THE ORDER OF 6 TO 12 INCHES.
TEMPERATURES WILL STAY WELL BELOW NORMAL AND NOT REACH THE FREEZING
MARK THROUGH THE WEEKEND INTO EARLY NEXT WEEK.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY AFTERNOON)
ISSUED AT 329 AM EST TUE DEC 10 2013

LAKE EFFECT SNOW SHOWERS WILL RAMP UP SIGNIFICANTLY BY MID TO LATE
MORNING THROUGH THIS AFTERNOON ENHANCED BY A STRONG UPPER LEVEL
DISTURBANCE CURRENTLY EASILY SEEN ON IR SAT IMAGERY OVER MN THAT
WILL CONTINUE TO MOVE ESE INTO OUR AREA LATER TODAY. THERE WILL BE
PLENTY OF LIFT WITH OMEGAS ON THE ORDER OF 10 TO 15 MICROBARS/SEC IN
THE DGZ AND DEEP MOISTURE THROUGH THE DGZ. IN FACT A BUFKIT
X-SECTION FOR KMKG OFF 00Z GUIDANCE SHOWS 20 MICROBARS/SEC OMEGA BY
LATE MORNING WHEN HEAVY SNOW IS LIKELY TO DEVELOP OVER OUR NW FCST
AREA. STRONG 1000-850 MB CONVERGENCE IS NOTED NW OF KGRR LATER TODAY
AND INVERSION HEIGHTS SHOULD BRIEFLY RISE TO AROUND 7-8 KFT AGL.

HEAVIEST SNOWFALL LATER TODAY IS EXPECTED NEAR TO ESPECIALLY
WEST/NORTHWEST/NORTH OF KGRR WHERE TOTAL SNOW ACCUMULATIONS FROM
AROUND 3 TO 5 INCHES LATER TODAY. THIS IN CONJUNCTION WITH STRONG
WEST WINDS THAT WILL INCREASE TO 20 TO 30 MPH BY LATE MORNING AND
AFTERNOON COULD PRODUCE NEAR WHITEOUT CONDITIONS AT TIMES ACROSS THE
ADVISORY AREA. THE WINTER WX ADVISORY HEADLINE LOOKS EXCELLENT AND
WILL REMAIN UNCHANGED.

LAKE EFFECT SNOW SHOWERS WILL CONTINUE TONIGHT WITH H8 TEMPS DOWN
AROUND -16 TO -18 C AND WITH DEEP MOISTURE STILL IN PLACE. HOWEVER
INTENSITY OF SNOWFALL WILL LIKELY DECREASE SOMEWHAT THIS EVENING.
HOWEVER ANOTHER STRONG SHORTWAVE WILL BRING ANOTHER ROUND OF HEAVIER
LAKE ENHANCED SNOW WEDNESDAY... PARTICULARLY ACROSS ROUGHLY THE
SOUTHERN THIRD OF OUR FCST AREA.

H8 TEMPS STAY DOWN AROUND -16 TO -18 C WEDNESDAY NIGHT ALONG WITH
SUFFICIENT MOISTURE SO WEST TO WSW FLOW LAKE EFFECT SNOW SHOWERS
WILL CONTINUE. THE LAKE EFFECT SNOW SHOWERS WILL CONTINUE THURSDAY
ALTHOUGH H8 TEMPS WILL SLOWLY MODERATE. LOW LEVEL MEAN FLOW BACKING
TO THE SW WILL CAUSE THE LAKE EFFECT TO BECOME FOCUSED MAINLY NW OF
KGRR THURSDAY.

.LONG TERM...(THURSDAY NIGHT THROUGH MONDAY)
ISSUED AT 329 AM EST TUE DEC 10 2013

COLD AND SNOWY RULES THE EXTENDED...AND BEYOND. WINTER IS HERE TO
STAY A WHILE AND IT LOOKS LIKE SEVERAL INCHES OF SNOW IS POSSIBLE ON
SATURDAY. BUMPED UP POPS TO LIKELY SATURDAY AS THE 00Z GUIDANCE HAS
TRENDED FURTHER NORTH WITH THE LOW COMING OUT OF THE SOUTHERN
PLAINS. MID LEVEL F-GEN COULD BE STRONG ENOUGH TO PRODUCE MESOSCALE
BANDS OF LIGHT TO MODERATE SNOW FOR SEVERAL HOURS SATURDAY AFTERNOON
AND EVENING ACROSS CENTRAL AND SOUTHERN LOWER MICHIGAN.

THE LOW MOVES EAST SATURDAY NIGHT...BUT LOWER MICHIGAN REMAINS IN
THE TROWAL INTO SUNDAY. SO THE SNOW WILL LESSEN IN INTENSITY BUT NOT
END. ANOTHER SHOT OF ARCTIC AIR...WITH 850 MB TEMPS NEAR MINUS 20C
MOVES IN FOR SUNDAY AFTERNOON. LAKE EFFECT SNOW SHOWERS WILL
CONTINUE INTO SUNDAY NIGHT BUT WILL BE CONFINED CLOSE TO THE LAKE
MICHIGAN COAST AS FLOW GOES NORTHERLY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 645 AM EST TUE DEC 10 2013

IFR IN SNOW AND BLOWING SNOW EXPECTED TO DEVELOP LATE THIS MORNING
AS CLIPPER MOVES THROUGH. SNOW WILL DIMINISH AND EXPECT MVFR TO
VFR IN LIGHT SNOW SHOWERS THIS EVENING. SOUTHWEST WINDS WILL GO
WEST THIS AFTERNOON AND GUST TO NEAR 30 KNOTS AT TIMES BEFORE
DECREASING THIS EVENING.

&&

.MARINE...
ISSUED AT 329 AM EST TUE DEC 10 2013

A SMALL CRAFT ADVISORY REMAINS IN EFFECT THROUGH MID MORNING
FOLLOWED BY A GALE WARNING FOR THE REST OF THE DAY THROUGH THIS
EVENING. WINDS BY LATE MORNING WILL REACH GALE FORCE CAUSING WAVE
HEIGHTS TO BUILD TO 8 TO 12 FEET. SIGNIFICANT WAVE ACTION IS
EXPECTED ON LAKE MI THROUGH THE REST OF THE WEEK DUE TO BRISK WINDS
AND COLD AIR ADVECTION.


&&

.HYDROLOGY...
ISSUED AT 329 AM EST TUE DEC 10 2013

WELL BELOW NORMAL TEMPERATURES WILL RESULT IN POTENTIAL FOR ICE JAMS
THROUGH THE REST OF THE WEEK AND WEEKEND AND EVEN INTO NEXT WEEK.
THE TREND TOWARD MORE ICE IN AREA RIVERS WILL CONTINUE GIVEN THE
SNOW AND COLD IN THE FORECAST AND TEMPERATURES WILL NOT REACH THE
FREEZING MARK THROUGH AT LEAST THE NEXT SEVEN TO TEN DAY PERIOD. WE
ARE CLOSELY MONITORING GIVEN THE FORECAST.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR MIZ037-
     038-043-044-050-056-057-064-071.

LM...SMALL CRAFT ADVISORY UNTIL 9 AM EST THIS MORNING FOR LMZ844>849.

     GALE WARNING UNTIL 11 PM EST THIS EVENING FOR LMZ844>849.

&&

$$

SYNOPSIS...LAURENS
SHORT TERM...LAURENS
LONG TERM...OSTUNO
AVIATION...OSTUNO
HYDROLOGY...LAURENS
MARINE...LAURENS