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000
FXUS63 KGRR 051720
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1220 PM EST THU DEC 5 2013

LATEST UPDATE...
AVIATION

.SYNOPSIS...
ISSUED AT 338 AM EST THU DEC 5 2013

COLDER AIR IS IN THE PROCESS OF MOVING IN ACROSS THE AREA THIS
MORNING. THIS COLDER AIR WILL REMAIN OVER THE AREA THROUGH THIS
WEEKEND. SOME LAKE EFFECT SNOW SHOWERS WILL BE AROUND THROUGH
SATURDAY FOR WESTERN AREAS WITH LIMITED SNOW ACCUMULATIONS.

A SYSTEM WILL MOVE ACROSS THE AREA LATE SUNDAY INTO EARLY MONDAY.
THIS WILL BRING SOME LIGHT SNOW TO MOST OF THE AREA. EVEN COLDER AIR
WILL FOLLOW NEXT WEEK WITH A MUCH BETTER POTENTIAL OF ACCUMULATING
LAKE EFFECT SNOW SHOWERS.

&&

.UPDATE...
ISSUED AT 1207 PM EST THU DEC 5 2013

I DROPPED THE MENTION OF SNOW THIS AFTERNOON AS THE LOW LEVELS ARE
TO DRY. FOR THE REST OF THE FORECAST ( TONIGHT THROUGH SATURDAY) I
USED A COMBINATION OF LOW LEVEL WIND TRAJECTORIES... OMEGA AND
CAPE IN THE 0 TO 2 KM LAYER AND THE OMEGA IN SATURATED DGZ TO
FIGURE OUT WHERE TO PUT LAKE ENHANCED SNOW SHOWERS. THIS SHOWS THE
BEST SHOT AT SNOW SHOWERS THAT WILL ACCUMULATE WILL BE LATE FRIDAY
AFTERNOON INTO MIDDAY SATURDAY. DURING THIS TIME THERE WHILE THE
MOISTURE DEEP IS VERY SHALLOW... THERE IS DECENT LIFT IN THE DGZ WITH
THTE DECEASING WITH HEIGHT BELOW 2 KM AND CAPES TO AROUND 50 J/KG
IN THE TYPICAL NORTHWEST FLOW LAKE ENHANCED COUNTIES. I FIGURE 1
TO 2 INCHES COULD FALL FRIDAY NIGHT IN THOSE AREAS. MAYBE ANOTHER
INCH SATURDAY MORNING.

&&

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 338 AM EST THU DEC 5 2013

MAIN ISSUE IN THE SHORT TERM IS DETERMINING LAKE EFFECT TRENDS
THROUGH SAT WITH THE COLDER AIR MOVING IN ACROSS THE AREA. WE
CONTINUE WITH THE SAME GENERAL IDEA THAT THERE WILL BE SOME LAKE
EFFECT SNOW SHOWERS AROUND. HOWEVER THERE WILL BE LIMITED
ACCUMULATION POTENTIAL WITH LIMITED MOISTURE DEPTH AND UPPER SUPPORT
OVERHEAD.

TEMPERATURES WILL SLOWLY DROP MOST OF THE DAY WITH THE COLDER AIR
MOVING IN BEHIND THE COLD FRONT. THE COLD FRONT IS NOW ACROSS THE SE
CORNER OF THE CWFA...AND WILL BE EXITING THE AREA OVER THE NEXT HOUR
OR SO. WE CAN EXPECT DRY CONDITIONS THROUGH THE FIRST PORTION OF THE
DAY TODAY...EVEN AS THE COLDER AIR MOVES IN.

WE EXPECT TO SEE A FEW SNOW SHOWERS DEVELOP THIS AFTERNOON FOR THE
WRN FAVORED LAKE EFFECT AREAS. WE DO NOT EXPECT TO SEE MUCH IF ANY
SNOW ACCUMULATION OF SNOW. IT IS THIS AFTERNOON THAT THE AIR IS COLD
ENOUGH THAT THE DGZ IS SATURATED. DELTA T/S WILL BE SUFFICIENT FOR
LAKE EFFECT DEVELOPMENT AS THEY SHOULD INCREASE TO AROUND THE MID
TEENS THIS AFTERNOON. MOISTURE PROFILES ON ALL MODELS INDICATE THAT
MOISTURE DEPTH WILL BE QUITE LIMITED TO AROUND 3K FT. THIS IS AS THE
DRY SLOT RESULTING FROM THE 165 KNOT UPPER JET WILL BE OVERHEAD.

LAKE EFFECT SNOW SHOWERS WILL CONTINUE FROM TONIGHT RIGHT ON THROUGH
THE DAY ON SATURDAY WITH LITTLE CHANGE IN THE SETUP. SOME
ACCUMULATIONS WILL BE POSSIBLE...HOWEVER WE CONTINUE TO THINK THEY
WILL REMAIN LIMITED. DELTA T/S WILL INCREASE TO THE UPPER TEENS
C. THE COLDER AIR COMING IN WILL INCREASE THE DGZ LAYER A LITTLE TO
HELP THE CAUSE FOR SNOW SHOWERS. THE FLOW WILL TRANSITION TO MORE OF
A WNW FLOW. SOME MID LEVEL MOISTURE FROM THE SYSTEM TO OUR SE WILL
TRY TO AID THE SRN PORTION OF THE LAKE EFFECT AREA. HOWEVER IT MAY
BE JUST A LITTLE TOO HIGH TO ASSIST IN A SEEDER FEEDER TYPE OF
SCENARIO.

MOISTURE DEPTH WILL CHANGE VERY LITTLE AS THE UPPER JET MOVES TO A
POSITION PUTTING THE ENTRANCE REGION OVERHEAD AND PLENTY OF
SUBSIDENCE EVIDENT. THE SFC FLOW WILL RESULT IN A ANTI-CYCLONIC
LOOKING FLOW...WHICH WILL OVERCOME THE TENDENCY FOR SOME LAKE
INDUCED TROUGHING. THIS WILL LIMIT THE AMOUNT OF LOW LEVEL
CONVERGENCE/MOISTURE CONVERGENCE NEEDED FOR GOOD LAKE EFFECT BANDS.

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 338 AM EST THU DEC 5 2013

COLD AND SNOWY ARE THE OPERATIVE WORDS FOR THE LONG TERM PERIOD.

THIS ALL GETS KICK STARTED BY A SYNOPTIC SYSTEM MOVING NORTHEAST
ALONG THE BAROCLINIC ZONE OVER THE OHIO VALLEY SUNDAY NIGHT INTO
EARLY MONDAY. THE SYSTEM DOES NOT LOOK PARTICULARLY STRONG BUT
SHOULD PROVIDE A WIDESPREAD 1-3 OR 2-4 INCH TYPE SNOWFALL.

MORE IMPORTANTLY IT IS THE PASSAGE OF THIS LOW WHICH HELPS TUG
DOWN THE MUCH COLDER/BLUSTERY ARCTIC AIR FOR THE EARLY TO MIDDLE
PART OF NEXT WEEK. HIGHS OF ONLY 15 TO 20 ARE EXPECTED FOR TUESDAY
AND WEDNESDAY WITH NUMEROUS LAKE EFFECT SNOW SHOWERS ALONG AND
WEST OF HIGHWAY 131.

LAKE EFFECT ACCUMULATIONS MAY NOT BE TOO EXCESSIVE MONDAY THROUGH
WEDNESDAY SINCE THE UPPER JET DOES NOT FULLY DIP SOUTH OF THE STATE
AND MOISTURE MAY BE LACKING DUE TO THE VERY COLD AIR MASS. THIS WILL
NEED TO BE WATCHED HOWEVER ESPECIALLY FOR THE TUESDAY AND TUESDAY
NIGHT PERIOD WHEN A CLIPPER/SFC LOW TRACKS EAST ACROSS LK
SUPERIOR. THIS SYSTEM COULD BRING A GOOD SOUTHWEST FLOW LAKE
ENHANCED EVENT FOLLOWED BY MORE NORTHWEST FLOW SNOWS BEHIND IT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1220 PM EST THU DEC 5 2013

MVFR CEILINGS COVERED THE REGION AS OF 17Z. HOWEVER THERE WAS SOME
CLEARING OCCURRING OVER LAKE MICHIGAN AND POINTS WEST. EXPECT THE
LOW CLOUDS TO GRADUALLY ERODE THROUGH THE AFTERNOON...BUT IT MAY
TAKE UNTIL CLOSE TO SUNSET FOR SOME AREAS TO CLEAR. OTHERWISE THE
WESTERLY WINDS WILL CONTINUE TO GUST AROUND 25 KNOTS...DROPPING
OFF INTO THIS EVENING.

THERE COULD BE SOME LIGHT LAKE EFFECT SNOW SHOWERS THAT DEVELOP
FRIDAY MORNING. WITH THE NW FLOW...AZO WOULD BE MOST PRONE TO
SEEING THESE...BUT VSBYS SHOULD ONLY BE REDUCED TO MVFR AT TIMES.
ALSO...THERE MAY BE AN AREA OF LIGHT SNOW THAT MOVES NORTH OUT OF
INDIANA TOWARD MID DAY FRI. THINKING THAT IF THIS OCCURS THE PCPN
WILL REMAIN LIGHT...FIGHTING DRY LOW LEVEL AIR. FOR NOW PUT IN
SOME LIGHT SNOW AT JXN.

&&

.MARINE...
ISSUED AT 338 AM EST THU DEC 5 2013

WE WILL BE DOWNGRADING THE NRN MARINE ZONES TO A SMALL CRAFT
ADVISORY TO MATCH THE SRN MARINE ZONES. THE STRONGEST SURGE OF WIND
WITH AND RIGHT BEHIND THE FRONT HAS NOW PASSED. WE WILL CONTINUE TO
SEE ROUGH CONDITIONS OUT ON THE LAKE...HOWEVER IT WILL BE QUITE
DIFFICULT TO REACH GALE CRITERIA WITH THE GRADIENT WEAKENING SOME.
THIS WIND WILL LAST INTO TONIGHT BEFORE DIMINISHING MORE.


&&

.HYDROLOGY...
ISSUED AT 338 AM EST THU DEC 5 2013

NO HYDROLOGY ISSUES EXPECTED IN THE NEAR TERM...HOWEVER WE ARE
WATCHING THE POTENTIAL FOR ICE RELATED ISSUES OVER THE WEEKEND AND
NEXT WEEK. THE RECENT RAINFALL OVER THE PAST COUPLE OF DAYS WAS NOT
ENOUGH TO CREATE ANY NOTEWORTHY ISSUES ON THE RIVERS. ALL RIVERS AND
STREAMS ARE AT AVERAGE TO A LITTLE ABOVE AVERAGE FLOWS.

WE ARE QUITE CONCERNED ABOUT ICE DEVELOPMENT ON THE AREA RIVERS THIS
WEEKEND AND NEXT WEEK. WE WILL SEE MANY DAYS WHERE THE AVERAGE DAILY
TEMP /AVERAGE OF MAX/MIN/ WILL BE AT OR BELOW 20 DEGREES F. THIS IS
A FAVORABLE SCENARIO FOR ICE DEVELOPMENT ON RIVERS THAT HAVE ALREADY
HAD ICE ON THEM THIS YEAR. THE POTENTIAL FOR ICE JAMS WILL EXIST AT
THE NORMAL TROUBLE SPOTS.

&&

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

&&

$$

UPDATE...WDM
SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...MEADE
AVIATION...JK
HYDROLOGY...NJJ
MARINE...NJJ