FXUS63 KGRR 092027
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
330 PM EST WED DEC 9 2009

LATEST UPDATE...ALL BUT AVIATION...

.SYNOPSIS...(330 PM EST WED DEC 9 2009)
A POWERFUL WINTER STORM WILL PULL AWAY FROM THE REGION TONIGHT AND 
THURSDAY.  ARCTIC AIR WILL MOVE IN BEHIND THE STORM.  THIS WILL LEAD 
TO WIDESPREAD LAKE EFFECT SNOW SHOWERS WHICH WILL CREATE HAZARDOUS 
DRIVING CONDITIONS.  HIGH PRESSURE WILL BUILD IN SATURDAY RESULTING 
IN DRY WEATHER.

&&

.SHORT TERM...(330 PM EST WED DEC 9 2009)
(TONIGHT THROUGH THURSDAY)

WILL MAINTAIN THE CURRENT HEADLINES.  AS THE DEEP LOW PRESSURE 
SYSTEM PULLS AWAY FROM THE REGION...CONSIDERABLE WRAP AROUND 
MOISTURE WILL PULL IN BEHIND IT ACROSS SOUTHWEST LOWER MI.  
CONTINUED COLD AIR ADVECTION WILL OCCUR THROUGH THE NIGHT...SETTING 
UP FAVORABLE CONDITIONS FOR WIDESPREAD SNOWFALL ACROSS THE FORECAST 
AREA.  LOW LEVEL CONVERGENCE WILL BE MAXIMIZED MAINLY ALONG AND WEST 
OF HIGHWAY 131...BUT A BAND OF BETTER CONVERGENCE WILL EXIST BETWEEN 
INTERSTATE 94 AND INTERSTATE 96 OVERNIGHT...WHICH WILL EXTEND EAST 
TOWARD LANSING ESPECIALLY AFTER 06Z TONIGHT.  WIND GUSTS OVER 40 MPH 
ARE LIKELY ESPECIALLY ALONG THE LAKESHORE AND ALONG INTERSTATE 94 AS 
BETTER MIXING HEIGHTS TAP THE STRONGER WINDS ALOFT.  

GIVEN THE TEMPERATURES FALLING INTO THE TEENS TO NEAR 20 DEGREES 
AROUND DAYBREAK...WIND GUSTS OVER 40 MPH AND STRONGER BANDS OF SNOW 
WILL MAINTAIN THE BLIZZARD WARNING THROUGH THURSDAY.  LOTS OF 
BLOWING SNOW IS EXPECTED AND THAT WILL ALLOW FOR VISIBILITIES TO 
IMPACT TRAVEL. WILL MAINTAIN THE SUBZERO WIND CHILLS FOR THURSDAY.

SNOW AMOUNTS WILL BE VARIABLE AS WILL THE SNOW INTENSITY TONIGHT 
INTO THURSDAY...BUT BY 00Z FRI MOST LOCATIONS IN THE WARNING AREA 
SHOULD SEE AT LEAST 6 INCHES OF SNOW. 

&&

.LONG TERM...(330 PM EST WED DEC 9 2009)
(THURSDAY NIGHT THROUGH WEDNESDAY)
PRIMARY FCST CONCERN IN THE LONG TERM PERIOD WILL BE LAKE EFFECT 
POTENTIAL THROUGH THE PERIOD...ALONG WITH A COUPLE OF WEAKER 
SYNOPTIC SYSTEMS MOVING THROUGH.

CONDITIONS WILL CONTINUE TO SLOWLY IMPROVE ACROSS THE AREA ON THU 
NIGHT AND FRI AS THE GRADIENT BETWEEN THE STRONG DEPARTING STORM AND 
HIGH PRESSURE TO OUR SOUTH RELAXES A LITTLE. DELTA T/S ARE EXPECTED 
TO REMAIN IN THE LOW TO MID 20S AND THE WRLY FLOW WILL CONTINUE...SO 
LAKE EFFECT SNOW SHOWERS WILL REMAIN LIKELY ON FRI BEFORE 
DIMINISHING A BIT BY FRI NIGHT AND WINDS RELAX. MOISTURE DEPTH WILL 
BE SHRINKING AS THE LOW PULLS AWAY. DGZ WILL BE BECOMING A LITTLE 
MORE FAVORABLE FOR SNOWFLAKE GENERATION AS TEMPS MODIFY A BIT AND 
THE DGZ RISES BACK INTO THE CLOUD LAYER.  

UPPER JET CORE IS STILL EXPECTED TO SHIFT NORTH OF THE AREA ON FRI 
NIGHT. SFC RIDGING IS EXPECTED TO MOVE ACROSS THE REGION LATE FRI 
NIGHT AND INTO SAT...WHICH WILL HELP TO REALLY LIMIT LAKE EFFECT 
POTENTIAL. LAKE EFFECT WILL LIKELY END FOR A SHORT PERIOD ON SAT AS 
THE RIDGE MOVES EAST OF THE AREA...AND WINDS DEVELOP AN SE 
COMPONENT. TEMPS WILL GRADUALLY MODIFY.

THE NRN STREAM OF THE JET LOOKS TO TAKE A BRIEF BREAK NORTH OF THE 
AREA LATE IN THE WEEKEND AND EARLY NEXT WEEK. A WEAK SRN STREAM WAVE 
IS EXPECTED TO MOVE E/NE TOWARD THE AREA WHICH WILL BRING ANOTHER 
CHC OF SOME LIGHTER SYNOPTIC TYPE SNOW AND TEMPS BACK TO NEAR 
NORMAL. 

THE NRN STREAM IS THEN EXPECTED TO DROP BACK DOWN INTO THE AREA FOR 
TUE AND WED NEXT WEEK AS A STRONGER JET STREAK ENTERS THE PICTURE.  
TIMING OF THESE SYSTEMS WILL BE A BIT PROBLEMATIC...HOWEVER COLDER 
AIR WILL MOVE BACK IN ALONG WITH LAKE EFFECT POTENTIAL.

&&

.AVIATION...(100 PM EST WED DEC 9 2009)
THE COLDER AIR WAS FILTERING IN FROM NORTHERN ILLINOIS AND 
INDIANA...CHANGING THE RAIN OVER TO SNOW.  WINDS WERE ALSO ON THE 
INCREASE WITH GUSTS OVER 30 KNOTS OCCURRING.  WIND GUSTS WILL LIKELY 
TOP 35 KNOTS AT MOST TAF SITES THIS AFTERNOON INTO TONIGHT.  THE 
SNOW WILL PERSIST THROUGH THE AFTERNOON AND INTO TONIGHT AS COLDER 
AIR CROSSING LAKE MICHIGAN ADDS MOISTURE TO THIS SYSTEM.  MANY 
LOCATIONS ARE EXPECTED TO SEE IFR CONDITIONS...TEMPORARILY FALLING 
TO LIFR THIS AFTERNOON.  IFR OR LOWER CONDITIONS WILL CONTINUE 
THROUGH NIGHT AND WITH TEMPERATURES FALLING BELOW FREEZING AND THE 
WINDS STAYING STRONG...BLOWING SNOW WILL BECOME AN ISSUE.  

LAKE EFFECT SNOW WILL DOMINATE ON THURSDAY...BUT BLOWING SNOW WILL 
CAUSE ISSUES AT TIMES.  GIVEN THE VARIABLE NATURE OF THE LAKE 
EFFECT...I WENT WITH MVFR CONDITIONS FROM KLAN TO KJXN...WITH IFR OR 
LOWER CLOSER TO THE LAKESHORE.

 
&&

.MARINE...(330 PM EST WED DEC 9 2009)
CONTINUED THE GALE WARNING.  WEBCAMS SHOW LARGE WAVES IMPACTING THE 
NEARSHORE WATER LOCATIONS.  STRONG COLD AIR ADVECTION THROUGH 
THURSDAY WILL CAUSE GALE FORCE WIND GUSTS TO CONTINUE. NOS SITES 
SHOW WATER LEVEL RISES OF AT LEAST A FOOT AT BIV AND LDM.  

&&

.HYDROLOGY...(330 PM EST WED DEC 9 2009)
NO HYDRO ISSUES EXPECTED AS COLD AIR WILL FREEZE ANY STANDING 
WATER.  

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...BLIZZARD WARNING WEST CWA THROUGH THURSDAY AFTERNOON.           
     WINTER WEATHER ADVISORY EAST CWA THROUGH THURSDAY 
     AFTERNOON.
     LM...GALE WARNING ST. JOSEPH TO MANISTEE THROUGH 
     THURSDAY.

&&

$$

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