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000
FXUS63 KGRR 030359
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1059 PM EST MON DEC 2 2013

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 331 PM EST MON DEC 2 2013

AN AREA OF LIGHT SNOW...POSSIBLY MIXED WITH SLEET SHOULD MOVE INTO
AREAS WEST OF US-131 BEFORE SUNRISE. THE PRECIPITATION WILL THEN
SPREAD ACROSS REST OF SOUTHWEST MICHIGAN BY EARLY AFTERNOON AND
SLOWLY CHANGE TO LIGHT RAIN. SOME SLEET MAY MIX IN WITH THE
PRECIPITATION AT TIMES IN THE MORNING. OCCASIONAL RAIN IS EXPECTED
TUESDAY NIGHT INTO WEDNESDAY EVENING AS TEMPERATURES WARM INTO THE
50S.

A STRONG COLD FRONT CROSSES THE AREA THURSDAY MORNING BRINGING
MUCH COLDER TEMPERATURES AND THE THREAT OF SNOW SHOWERS INTO THE
WEEKEND.

&&

.UPDATE...
ISSUED AT 934 PM EST MON DEC 2 2013

UPDATED THE GRIDS TO REFLECT A FZRA/SLEET POTENTIAL TONIGHT.
HRRR/NAM BOTH SHOW THAT POTENTIAL. DON/T THINK QPF WILL BE HIGH
AND SO IMPACT SHOULD BE ON THE LOW SIDE. AS A RESULT...NO
HEADLINE. HOWEVER...THAT COULD CHANGE OVERNIGHT IF PCPN RAMPS UP
MORE THAN EXPECTED. THINK PCPN WILL BEGIN AS LIGHT SNOW AND THEN
BEGIN TO TRANSITION TO MORE OF A SNOW/SLEET/FREEZING RAIN
POTENTIAL AS WARMER AIR OVERRUNS THE COLDER AIR NEAR THE SFC.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 331 PM EST MON DEC 2 2013

THE MAIN ISSUES THIS FORECAST CYCLE ARE THE THREAT OF A MIXED
PRECIPITATION EVENT LATE TONIGHT INTO MID AFTERNOON TUESDAY AHEAD
OF THE WARM FRONT. NEXT IS THE POTENTIAL FOR RAIN TUESDAY NIGHT
INTO WEDNESDAY AHEAD OF THE COLD FRONT. FINALLY THERE IS THE ISSUE
OF THE TIMING OF THE COLD FRONT LATER WEDNESDAY INTO EARLY THURSDAY.

THERE IS CURRENTLY AN AREA OF SNOW AND RAIN OVER EASTERN IOWA
HEADING EAST NORTHEAST AHEAD OF THE WARM FRONT TOWARD LOWER
MICHIGAN. AS TYPICAL THERE IS A CONSIDERABLE AMOUNT OF LOW LEVEL
DRY AIR AHEAD OF THIS PRECIPITATION AREA. I EXPECT THIS TO SLOW
DOWN THE ADVANCE THE PRECIPITATION AS IT MOVES INTO LOWER
MICHIGAN. EVEN SO THE MODELS ALL SHOW DEEP MOISTURE IN PLACE BY
SUNRISE TUESDAY SO I EXPECT ALL AREAS NORTH OF INTERSTATE 94 WILL
SEE SOME PRECIPITATION IN THE NEXT 24 HOURS. LIKELY IT WILL START
AS SNOW THEN CHANGE QUICKLY TO LIGHT RAIN BEFORE ENDING. NEAR
ROUTE 10 THE MIXED PRECIPITATION MAY LAST A LITTLE LONGER. SINCE
THE SYSTEM LIMITED ON MOISTURE I DO NOT EXPECT MUCH ACCUMULATION
OF SNOW WITH THIS. THERE IS SLIGHT THREAT OF FREEZING RAIN NEAR
ROUTE 10 MID MORNING TUESDAY BUT IT IS MARGINAL SINCE TEMPS SHOULD
BE WARMING ABOVE FREEZING BY THEN.

AS FOR WEATHER HEADLINES... SEEMS THE QPF IS TO LIMITED TO REALLY
WORRY ABOUT SIGNIFICANT IMPACTS FROM THIS EVENT.

THE MAIN ISSUE OTHER THAN THE RAIN AHEAD OF THE COLD FRONT
WEDNESDAY IS THE TIMING OF THE COLD FRONT WEDNESDAY NIGHT OR EARLY
THURSDAY. SINCE THE TYPICAL GFS ERROR IS TO BRING SHEAR UPPER LOWS
OUT TO QUICKLY AND SINCE THE FIM MODEL...ECMWF...UKMET AND
CANADIAN HAVE BEEN VERY CONSISTENT WITH NOT CREATING AS STRONG
LEAD WAVE LIKE BOTH THE GFS AND NAM DO I AM TOTALLY NOT BUYING THE
GFS OR NAM (THEY ARE BOTH TRENDING TOWARD THE ECMWF ANYWAY). SO I
HAVE THE CHANGE FROM RAIN SHOWERS TO SNOW SHOWERS LATER WEDNESDAY
NIGHT.

MY CLASSIC THICKNESS TOOLS TELL ME HIGHS SHOULD BE IN THE LOWER
TO MID 50S WEDNESDAY. I PUSHED THE HIGHS UP SOME IN THAT TIME
FRAME.

.LONG TERM...(THURSDAY THROUGH MONDAY)
ISSUED AT 331 PM EST MON DEC 2 2013

A WINTRY PATTERN IS EXPECTED THROUGH THE LONG RANGE FORECAST PERIOD
WITH BELOW NORMAL TEMPS AND LAKE EFFECT SNOW SHOWERS. NORTHWEST FLOW
COLD AIR ADVECTION BEGINS THURSDAY WHEN MAX TEMPS WILL ONLY REACH
THE 30S. COLDER AIR WILL CONTINUE TO MOVE IN FRIDAY THROUGH THE
WEEKEND WHEN MAX TEMPS WILL ONLY REACH THE 20S.

LAKE EFFECT SNOW SHOWERS ARE EXPECTED THROUGH MOST OF THE LONG RANGE
FORECAST PERIOD. THE RELATIVELY BEST CHANCE FOR THOSE SHOULD COME
FRIDAY THROUGH SATURDAY WHEN H8 TEMPS WILL BE DOWN AROUND -16 C.

TEMPS MAY MODERATE JUST A BIT SUNDAY INTO MONDAY (BUT REMAIN BELOW
NORMAL). A CONSENSUS OF LATEST MEDIUM RANGE GUIDANCE INDICATES
ANOTHER SURGE OF ARCTIC AIR SHOULD MOVE IN MONDAY NIGHT OR TUESDAY
THROUGH AT LEAST THE MIDDLE PORTION OF NEXT WEEK WITH BELOW NORMAL
TEMPS AND LAKE EFFECT SNOW SHOWERS EXPECTED.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1058 PM EST MON DEC 2 2013

THE MAIN AVIATION ISSUE TONIGHT IS WITH THE LIGHT MIXTURE OF
SNOW... FREEZING RAIN.. AND SLEET WHICH IS EXPECTED FROM ROUGHLY
08Z TO 14Z. THIS WILL IMPACT THE MORNING RUSH WITH THE LIKELIHOOD
FOR ICING AS WELL AS SLIPPERY RUNWAY CONDITIONS. THE ICING THREAT
IS EXPECTED TO END BY 15Z AS SFC TEMPS WARM ABOVE FREEZING AND THE
PRECIPITATION CHANGES TO ALL LIGHT RAIN.

WIDESPREAD VFR CONDITIONS AT 04Z WILL LOWER FAIRLY QUICKLY INTO
THE MVFR/IFR CATEGORY 06Z-09Z AS THE LIGHT WINTRY MIX DEVELOPS AND
SPREADS EAST/NORTHEAST. PRECIPITATION WILL CHANGE TO ALL RAIN BY
MID MORNING TUESDAY ALTHOUGH WIDESPREAD IFR CONDITIONS ARE EXPECTED
FOR TUESDAY AFTERNOON AND EVENING DUE TO PERSISTENT LOW CIGS/VSBYS
IN LINGERING LIGHT RAIN/FOG.

&&

.MARINE...
ISSUED AT 331 PM EST MON DEC 2 2013

WE MAY NEED A SMALL CRAFT ADVISORY FOR THE NORTHERN NEAR SHORE
TUESDAY AFTERNOON INTO TUESDAY NIGHT DUE TO THE 15 TO 25 KNOT
SOUTHERLY WINDS. THE MIDNIGHT SHIFT CAN LOOK AT THIS MORE
CLOSELY.


&&

.HYDROLOGY...
ISSUED AT 331 PM EST MON DEC 2 2013

PRECIPITATION AMOUNTS SHOULD NOT BE ENOUGH TO RESULT IN HYDRO
ISSUES.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
&&

$$

UPDATE...93
SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...LAURENS
AVIATION...MEADE
HYDROLOGY...WDM
MARINE...WDM