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000
FXUS63 KGRR 100449
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1155 PM EST TUE FEB 9 2010

LATEST UPDATE...AVIATION...

.SYNOPSIS...(458 PM EST TUE FEB 9 2010)
LOW PRESSURE WILL PIVOT ACROSS WESTERN LAKE ERIE TONIGHT AND MOVE
OFF THE EAST COAST OF THE UNITED STATES BY WEDNESDAY MIDDAY. THE LOW
WILL AID IN CONTINUING THE SNOW ACROSS LOWER MICHIGAN THROUGH
TONIGHT. AS THE LOW CLOSES IN ON THE SOUTHERN GREAT LAKES THIS
EVENING A BURST OF HEAVIER SNOW WILL OCCUR FROM THE LATE AFTERNOON
HOURS THROUGH THE EVENING. THE SNOW WILL LIGHTEN UP OVERNIGHT AND
TAPER OFF CONSIDERABLY TOWARD DAYBREAK ON WEDNESDAY. NORTHERLY WINDS
WILL INCREASE INTO THE 15 TO 30 MPH RANGE LATE TONIGHT AND WEDNESDAY
THOUGH CREATING AREAS OF BLOWING AND DRIFTING SNOW WHICH WILL
PERSIST THROUGH THE DAY ON WEDNESDAY. HIGH PRESSURE SLIDING THROUGH
THE GREAT LAKES REGION WILL PROVIDE QUIET...DRY WEATHER FOR THURSDAY
AND FRIDAY WITH TEMPERATURES IN THE 20S FOR HIGHS.

&&

.SHORT TERM...(1003 PM EST TUE FEB 9 2010)
(TONIGHT THROUGH WEDNESDAY NIGHT)
STORM CONTINUES TO UNFOLD AS FORECASTED...THEREFORE NO CHANGES
PLANNED WITH THE HEADLINES.  HAVE MADE ONLY MINOR TWEAKS TO THE
GRIDS...SO NO ZFP UPDATE IS PLANNED.  MUCH OF THE CWA WILL SEE AN
ADDITIONAL 2-4 INCHES OF SNOW OVERNIGHT...BRINGING STORM TOTALS OF 6
TO 10 INCHES...WITH ISOLATED SPOTS PERHAPS REACHING A FOOT OF SNOW
WITHIN THE WARNING AREA.

BASED ON GLERL OBSERVED WINDS...GUSTS HAVE LARGELY STAYED IN THE
20 TO 30 MPH RANGE  ALONG THE COAST.  WINDS SHOULD PEAK AROUND
MIDNIGHT...PERHAPS UP A SLIGHT TICK FROM PRESENT...BUT FREQUENT
GUSTS AT OR ABOVE 35 MPH ARE NOT EXPECTED.  THEREFORE CONSIDERABLE
BLOWING AND DRIFTING WILL CONTINUE OVERNIGHT...BUT BLIZZARD
CONDITIONS SHOULD NOT BE ACHIEVED.

00Z MODEL DATA SHOWS THE BEST LIFT WITHIN THE DEFORMATION ZONE
PULLING EAST AFTER ABOUT 08-09Z WHEN THE SNOW WILL BEGIN TO DIMINISH
IN INTENSITY.  ITS POSSIBLE WE WILL BE ABLE TO CANCEL THE HEADLINES
EARLY...BUT WILL DETERMINE THAT WITH THE 4 AM WED PACKAGE.


PREVIOUS DISCUSSION...
STORM SYSTEM EVOLVING ABOUT AS EXPECTED THIS AFTERNOON WITH PERIODS
OF LIGHT TO OCCASIONALLY MODERATE SNOW HAVING OCCURRED THROUGH THE
DAY. SNOWFALL TOTALS RANGE FROM 1-3 INCHES SO FAR ACROSS THE CENTRAL
LOWER MICHIGAN TO 2-4 INCHES THROUGH THE INTERSTATE 96 CORRIDOR AND
3-5 INCHES DOWN ALONG INTERSTATE 94.

A MORE PERSISTENT MODERATE TO OCCASIONALLY HEAVY SNOW WILL NOW OCCUR
THROUGH ABOUT 1000PM. THE SNOW HAS PICKED UP IN INTENSITY ALREADY
THIS AFTERNOON AND THIS SHOULD CONTINUE FOR THE NEXT 4-6 HOURS.
AFTER 1000-1100 PM THE SNOW WILL BEGIN TO GRADUALLY LIGHTEN UP WITH
ACCUMULATING SNOW CONTINUING INTO THE OVERNIGHT HOURS. THE SNOW WILL
THEN TAPER OFF SIGNIFICANTLY BETWEEN 500AM-900AM.

THE FORECAST LOOKS ON TRACK FOR STORM TOTAL SNOW AMOUNTS IN THE 3 TO
6 INCHES RANGE ACROSS THE ADVISORY AREA WITH 6 TO 10 INCHES OF SNOW
FALLING IN THE WARNING AREA.

THE SNOW IS BEING AIDED BY THE PERSISTENT ISENTROPIC UPGLIDE THAT
DOES NOT SHUT DOWN UNTIL LATE TONIGHT. THE MODELS HAVE BEEN VERY
CONSISTENT WITH THIS. ALSO...THIS EVENING THE 850MB LOW SLIDES BY TO
THE SOUTH MOVING FROM FORT WAYNE TO NEAR TOLEDO...WHICH IS A VERY
FAVORABLE TRACK FOR MODERATE TO HEAVY SNOW FOR LOCATIONS FROM
INTERSTATE 96 TO THE SOUTH.

DURING THE LATE OVERNIGHT HOURS AND WEDNESDAY TIME FRAME WINDS WILL
BEGIN TO INCREASE. IN GENERAL...A NORTHERLY WIND OF 15 TO 30 MPH IS
EXPECTED DURING THIS TIME FRAME. AREAS OF BLOWING AND DRIFTING SNOW
WILL OCCUR WITH THE HIGHEST LIKELIHOOD TOWARD THE LAKE MICHIGAN
COAST.

AFTER THE SYNOPTIC SNOW PUSHES EAST EARLY WEDNESDAY WE WILL SEE LAKE
EFFECT SNOW FIRE UP...BUT WITH A NORTHERLY FLOW WE ARE NOT EXPECTING
MUCH IN OUR FORECAST AREA. A DOMINANT BAND WILL LIKELY FORM PUSHING
INTO AREAS LIKE MICHIGAN CITY INDIANA. TEMPERATURES ACTUALLY BECOME
MARGINAL FOR LES INTO WEDNESDAY NIGHT.

&&

.LONG TERM...(458 PM EST TUE FEB 9 2010)
(THURSDAY THROUGH TUESDAY)
MAIN CONCERN IN THE LONG TERM WILL BE THE NEXT SYSTEM THAT IS
EXPECTED TO DROP SOUTH OUT OF CANADA THIS WEEKEND.

N/NW FLOW WILL HANG ON THROUGH THU NIGHT ON THE FAR WRN PERIPHERY OF
THE SYSTEM NOW AFFECTING THE AREA. AIR BEHIND THIS SYSTEM IS NOT
EXPECTED TO BE ALL THAT COLD...ONLY AROUND -8C TO -10C. THIS WILL
PROVIDE ONLY A LOW CHC OF SOME LIGHT LAKE EFFECT SNOW SHOWERS FOR
THE WRN HALF OF THE CWFA INTO THU EVENING WITH DELTA T/S ONLY 9 TO
12C. RIDGING WILL MOVE IN FOR FRI AND BRING DRY WX AND THE POTENTIAL
FOR SOME SUNSHINE.

MODELS ARE ALL IN AGREEMENT IN DROPPING A FAIRLY SIGNIFICANT PIECE
OF ENERGY SOUTH OUT OF CANADA LATE ON SAT AND DURING THE DAY ON SUN.
THIS SYSTEM HAS TRENDED STRONGER AND IS NOW EXPECTED TO PASS SOUTH
AND EVENTUALLY SOUTH OF THE AREA. THIS IS NOT SURPRISING CONSIDERING
SYSTEMS OUT OF CANADA USUALLY END UP STRONGER. WE HAVE A LOW CHC OF
SNOW IN FOR THE WEEKEND AND EVEN MON AS THE WRAP AROUND MOISTURE ON
THE BACKSIDE OF THE SYSTEM COULD IMPACT THE AREA. WE THINK THAT
MOST...IF NOT ALL OF THE PCPN WITH THIS SYSTEM SHOULD MISS THE AREA.

COOLER AIR WILL REMAIN IN PLACE THROUGH THE PERIOD...ALTHOUGH THERE
COULD BE A SLIGHT MODERATING TREND TOWARD THE END OF THE PERIOD. WE
HAVE STARTED NEXT TUE OUT DRY AS RIDGING BUILDS IN BEHIND THE
WEEKEND SYSTEM.

&&

.AVIATION...(1155 PM EST TUE FEB 9 2010)
THE MAIN CHALLENGE IN THE AVIATION FORECAST DEALS WITH THE TIMING OF
THE DEPARTURE OF THE LIFR AND IFR CONDITIONS.

THE BAND OF SNOW THAT HAS IMPACTED THE TAF SITE THROUGH THE
EVENING...IS WEAKENING.  IN ADDITION A WEDGE OF LOW LEVEL DRY AIR
WAS DROPPING SOUTH FROM KFFG AND KRQB TOWARD KMKG.  I WILL FEATURE
IMPROVING CONDITIONS TO MVFR PRIOR TO DAYBREAK FOR SEVERAL OF THE
WRN TAF SITES BECAUSE OF THIS TREND.  WHILE THERE STILL COULD BE
SOME LIFR OR IFR FOR THE REST OF THE NIGHT...BY DAYBREAK MOST TAF
SITES SHOULD BE IMPROVING TO MVFR.

DURING WEDNESDAY MORNING THE DEEPER MOISTURE PULLS EAST THROUGH THE
TAF SITES.  AS A RESULT...THIS WILL BRING AND END TO THE SNOW.

NORTHEAST WINDS SHIFT TO THE NORTH BY DAYBREAK AND
INCREASE ESPECIALLY WEDNESDAY.  NORTHWEST WINDS ARE LIKELY FOR
WEDNESDAY AFTERNOON.  DRIFTING SNOW IS EXPECTED.




&&

.MARINE...(458 PM EST TUE FEB 9 2010)
DROPPED THE GALE WATCH EARLIER AND EXTENDED THE SMALL CRAFT ADVISORY
INTO THURSDAY MORNING. WINDS DO NOT LOOK STRONG ENOUGH IN THE LOWEST
2K FEET TO PUSH A SUSTAINED WIND OR A LONG PERIOD OF FREQUENT GUSTS
TO GALE FORCE. THE MAY BE A FEW BRIEF GUSTS TO GALE FORCE LATE
TONIGHT AND EARLY WEDNESDAY MORNING...BUT NOT PERSISTENT ENOUGH TO
REQUIRE A GALE. SMALL CRAFT ADVISORIES SHOULD COVER THINGS WITH
WAVES BUILDING INTO THE 5 TO 10 FOOT RANGE IN THE NEARSHORE WATERS
ON WEDNESDAY.

&&

.HYDROLOGY...(458 PM EST TUE FEB 9 2010)
ALL AREA RIVERS ARE WITHIN BANK. ICE ON RIVERS CONTINUES TO
INCREASE SOME. RECENT OBSERVATIONS INDICATE THAT SYCAMORE CREEK AT
HOLT IS NOW COMPLETELY ICED OVER...BUT THE ICE IS SOLID AND NO ICE
JAMS EXIST. THE GRAND RIVER AT ROBINSON TOWNSHIP IS ALSO ICED
OVER...BUT THE ICE LOOKS STABLE. BELOW NORMAL TEMPS WILL PERSIST
INTO THE WEEKEND...BUT WE ARE NOT ANTICIPATING TO DEAL WITH ANY ICE
JAM PROBLEMS AT THIS POINT. NO KNOWN ICE JAMS EXIST PER RIVER
OBSERVATIONS.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...WINTER STORM WARNING ENTIRE CWA EXCEPT FOR MASON...LAKE...
     OSCEOLA AND CLARE COUNTIES WHICH ARE UNDER A WINTER WEATHER
     ADVISORY. TIME FRAME OF BOTH HEADLINES IS THROUGH 18Z WED.
LM...SMALL CRAFT ADVISORY THROUGH WEDNESDAY NIGHT FROM ST. JOSEPH TO
     MANISTEE.

&&

$$

SYNOPSIS:     DUKE
SHORT TERM:   DUKE JK
LONG TERM:    NJJ
AVIATION:     MJS
MARINE:       DUKE
HYDROLOGY:    DUKE