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000
FXUS63 KGRR 181734
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1234 PM EST WED DEC 18 2013

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 322 AM EST WED DEC 18 2013

THE ACTIVE WEATHER PATTERN WILL CONTINUE FOR THE NEXT SEVERAL DAYS
AFTER A BRIEF LULL TODAY. SNOW SHOWERS WILL DIMINISH TODAY AND
WARMER AIR IS ON TAP FOR THURSDAY WITH HIGHS IN THE MID 30S. MIXED
RAIN AND SNOW IS POSSIBLE THURSDAY NIGHT THROUGH FRIDAY. SOME SLEET
AND FREEZING RAIN IS POSSIBLE TOO BEFORE COLDER AIR MOVES BACK IN
FOR THE WEEKEND. SNOW IS SET TO RETURN SATURDAY NIGHT INTO SUNDAY.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 322 AM EST WED DEC 18 2013

FORECAST CONCERNS DEAL WITH PCPN POTENTIAL THROUGH THE PERIOD.

LATEST RADAR SHOWS A DIMINISHING TREND AS THE CORE OF THE ARCTIC AIR
MOVES EAST. AS SUCH WE CANCELED THE WINTER WX ADVISORY. THE REST OF
THE DAY LOOKS FAIRLY QUIET OUTSIDE OF A FEW LINGERING SNOW SHOWERS
THIS MORNING.

THE NEXT CLIPPER MOVING TOWARD THE UP WILL PUSH SOME WARM AIR INTO
LOWER MICHIGAN THURSDAY. ISENTROPIC LIFT AHEAD OF THE COLD FRONT
WILL RESULT IN SOME PCPN DEVELOPING. FORECAST SOUNDINGS SHOW LIGHT
RAIN POSSIBLE SOUTH OF I-94 WITH MIXED RAIN AND SNOW NORTH OF
THERE. THE PCPN WILL CONTINUE INTO THURSDAY NIGHT. CHANCES ARE
LOW...BUT POSSIBLE...THAT SOME SLEET COULD MIX IN WITH THE PCPN
ACROSS THE CENTRAL CWA.

THE COLD FRONT WILL STALL OVER LOWER MICHIGAN THURSDAY NIGHT AND
ALLOW ANOTHER LOW TO RIDE NORTHEAST ALONG IT. THIS WILL RESULT IN
PCPN CONTINUING THROUGH FRIDAY. SOUNDINGS SUGGEST THAT PCPN WILL BE
MAINLY RAIN SOUTH OF I-96 WITH MIXED RAIN/SNOW NORTH OF THERE. GIVEN
THE COLD GROUND TEMPS...SOME FREEZING RAIN MAY BE POSSIBLE.
CONFIDENCE IN THAT IS LOW HOWEVER AND WAS LEFT OUT OF THE GRIDS.

.LONG TERM...(FRIDAY NIGHT THROUGH TUESDAY)
ISSUED AT 322 AM EST WED DEC 18 2013

THE MAIN CONCERN IN THE LONG TERM DEALS WITH THE POTENTIAL STORM
OVER THE WEEKEND.  CONFIDENCE CONTINUES TO GROW CONCERNING THE
PROBABILITY FOR MODERATE OR HIGHER IMPACTING WINTER STORM EVENT SAT
NIGHT INTO SUN.

MODELS SHOW THE RIGHT ENTRANCE REGION OF A VERY  STRONG UPPER
JET...SITUATED OVER LOWER MI SAT NIGHT INTO SUN.  IN ADDITION MOIST
FGEN IS NOTED.  SW LOWER MI WILL BE ON THE COLD SIDE OF THE TIGHT
FRONTAL ZONE WITH ABUNDANT GULF MOISTURE ALONG IT.  MODELED QPF
VALUES ARE  HIGH HERE IN MY CWA...WITH THE GFS SHOWING AROUND A HALF
INCH...AND THE HIGH RES EURO WELL OVER AN INCH.

A COUPLE OF CONCERNS DO EXIST THAT MAY LIMIT/ALTER THE IMPACT OF
THIS POTENTIAL STORM FOR PARTS OF THE REGION.  FIRST IS THAT A
CONSIDERABLE MID LEVEL DRY SLOT STILL SHOWS UP FROM THE MODELS
MAINLY FOR SUNDAY.  FORECAST SOUNDINGS SOUTH OF A LWA TO LAN LINE
SHOW THIS AND WOULD SUPPORT A CONSIDERABLE LULL IN THE PRECIPITATION
FOR MUCH OF SUN...WITH PERHAPS FZDZ.  ALSO FOR JXN SOUNDINGS  SHOW
THE ONSET SAT NIGHT TO BE A MIX WITH A WARM LAYER AROUND 850 MB.
THE TROWAL DOES END UP PIVOTING THROUGH THE DRY SLOTTED AREA LATER
SUN INTO SUN NIGHT.

I ENDED UP ADDING A MIX TO THE FORECAST FOR MY SOUTHERN COUNTIES SAT
NIGHT.  OTHER THAN THAT CHANGE I DID NOT WANT TO PUT DOWN TOO MANY
SPECIFIC DETAILS AS THE POTENTIAL STORM IS STILL A WAYS OFF.  I DID
INCREASE POPS FOR SAT NIGHT INTO SUN...SHOWING MAINLY A IMPACTING
SNOW EVENT FOR THE REGION.

AS FOR THE REST OF THE FORECAST...WILL NEED TO MONITOR THE FZDZ
POTENTIAL LATE FRI NIGHT INTO SAT AM SOUTHEAST OF GRR AND LAN.  KEPT
IT R/S AT THIS POINT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1234 PM EST WED DEC 18 2013

HAD REMOVED IFR CIGS FROM THE INHERITED TAFS AND EXPECT A GRADUAL
IMPROVEMENT FROM MVFR TO VFR. WE DO NOT EXPECT IFR CONDITIONS OR
EVEN FUEL ALTERNATE THRESHOLDS TO BE MET THROUGH THIS EVENING.

CEILINGS ARE EXPECTED TO DROP BELOW FUEL ALTERNATE THRESHOLDS
LATER TONIGHT WITH A SLIGHT CHANCE FOR CIGS BELOW 1000. THERE
ALSO IS A SLIGHT CHANCE FOR DRIZZLE OR FREEZING DRIZZLE AFTER 09Z
THURSDAY...ESPECIALLY AT THE KGRR...KAZO...KBTL...KJXN...AND KLAN
TERMINALS. THIS IS A LOW CONFIDENCE POSSIBILITY FAR OUT IN TIME SO
HAVE NOT INCLUDED IN THE TAFS AT THIS POINT.

&&

.MARINE...
ISSUED AT 325 AM EST TUE DEC 17 2013

HAZARDOUS WINDS AND WAVES ARE ANTICIPATED OVER LK MI TODAY.


&&

.HYDROLOGY...
ISSUED AT 1046 AM EST WED DEC 18 2013

AREA RIVERS CONTINUE TO HAVE THICK ICE BUILD UP BUT HAVE MAINTAINED
STABILITY. THE FOCUS CONTINUES TO BE ON THE POSSIBLE WINTER STORM
OVER THE WEEKEND. THIS STORM BRINGS A GREATER POTENTIAL TO YIELD
HIGHER THAN NORMAL PRECIPITATION AMOUNTS. PRECIPITATION TYPES ARE
STILL IN QUESTION AND HIGHLY DEPENDENT ON THE EXACT TRACK OF A
FORECAST THAT IS STILL EVOLVING. IN THE MEANTIME...A BRIEF WARM
PERIOD IS EXPECTED THURSDAY AND FRIDAY WITH HIGHS IN THE LOW TO MID
30S. TODAY WILL REMAIN QUIET WITH LITTLE OR NO ADDITIONAL
PRECIPITATION. A LIGHT MIX OF RAIN AND/OR SNOW WILL MOVE INTO THE
AREA THURSDAY AND PART OF FRIDAY. OVERALL TOTALS THURSDAY AND FRIDAY
SHOULD BE RATHER LIGHT AND SHOULD NOT HAVE ANY GREAT EFFECT ON
WATER LEVELS.

ABOVE FREEZING TEMPERATURES THURSDAY AND FRIDAY COULD INCREASE THE
LIKELIHOOD OF ICE MOVEMENT. THE POTENTIAL FOR FLOODING INCREASES
DUE TO ICE JAMS CREATED BY ICE MOVEMENT. AT THIS TIME IT DOES NOT
APPEAR THAT TEMPERATURES WILL REMAIN ABOVE FREEZING LONG ENOUGH TO
CREATE ICE MOVEMENT. HOWEVER...PROPERTIES ALONG RIVER BANKS SHOULD
MONITOR RIVERS AND NOTE ANY MOVEMENT OF ICE WHICH COULD LEAD TO
RISING WATER LEVELS.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 7 PM EST THURSDAY FOR LMZ844>849.

&&

$$

SYNOPSIS...93
SHORT TERM...93
LONG TERM...MJS
AVIATION...TJT
HYDROLOGY...JAM
MARINE...MEADE