FXUS63 KGRR 100521
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1215 AM EST THU DEC 10 2009

LATEST UPDATE...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...(1035 PM EST WED DEC 9 2009)
(TONIGHT THROUGH THURSDAY)
NEW DATA ROLLING IN THIS EVENING REMAINS CONSISTENT FOR TONIGHT AND 
THURSDAY.  EARLIER SHEAR IN THE PROFILE...DUE TO THE SURFACE TROUGH 
PASSING THROUGH...HAS NOW EXITED TO THE EAST.  DELTA T/S ARE NOW 
APPROACHING 20 AS COLDER AIR CONTINUES TO FILTER IN.  INVERSION 
LEVELS REMAIN UNLIMITED.  AND WINDS IN THE LOW LEVELS STILL SUGGEST 
WE WILL MIX 35-40 MPH WINDS TO THE SURFACE.

SO THERE IS LITTLE DOUBT CONDITIONS WILL CONTINUE TO WORSEN FROM 
THIS POINT ONWARD AND REMAIN POOR THROUGH MUCH OF THURSDAY.  THE 
ONLY ELEMENT THAT CHANGES OVER THE NEXT 24 HOURS WILL BE THE MEAN 
FLOW IN THE CLOUD LAYER.  AT PRESENT THE FLOW IS 290...BRINGING THE 
STRONGEST SNOW BANDS INTO THE SW PORTION OF THE CWA.  THE FLOW 
BEGINS TO BACK TO 260-275 AROUND 09Z AS A SHORT WAVE MOVES INTO THE 
WESTERN GREAT LAKES.  THE SUBTLE TURN IN THE WINDS WILL PUSH THE 
LAKE BAND NORTH...NEAR I-96.  AND THE SHORT WAVE WILL ADD ADDITIONAL 
LIFT WHICH WILL HELP FURTHER INCREASE SNOW BAND COVERAGE AND 
INTENSITY.  NEW BUFKIT DATA SHOW A CROSS HAIR SIGNATURE OF OMEGA 
WITHIN THE DGZ AROUND DAYBREAK.  THIS SIGNATURE IS NOTED AGAIN 
THURSDAY AFTERNOON AS ANOTHER SHORT WAVE APPROACHES.  THE FLOW 
REMAINS 260-275 WITH THIS SECOND WAVE.

SO BOTTOM LINE IT STILL APPEARS WE WILL SEE CONDITIONS WORSEN 
OVERNIGHT AND CONTINUE MUCH OF THURSDAY.  THE MORNING COMMUTE 
APPEARS TO BE WITHIN THE HEART OF THE EVENT WHEN TRAVEL CONDITIONS 
WILL LIKELY BE SEVERELY IMPACTED.  THEREFORE...DESPITE THE SLOW 
PROGRESS OF THIS UNFOLDING EVENT...NO CHANGES IN HEADLINES WILL BE 
MADE.

&&

.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...(1215 AM EST THU DEC 10 2009)
FREQUENT IFR/LIFR CONDITIONS IN SNOW SHOWERS AND BLOWING SNOW CAN BE 
EXPECTED OVER THE NEXT 24 HOURS AS COLD AIR AND STRONG WINDS POUR IN 
BEHIND THE DEPARTING LOW PRESSURE CENTER. THE HEAVIEST SNOW BANDS 
WHICH WERE PRIMARILY SOUTH OF MKE... GRR... AND LAN AT 05Z ARE 
EXPECTED TO EVENTUALLY BECOME ALIGNED FROM MKG AND GRR TO LAN 
TOWARD/AFTER 12Z THURS. BLOWING SNOW WILL BECOME MORE OF AN ISSUE BY 
12Z THURSDAY ONCE THE LOW LEVEL COLD AIR ARRIVES.  
 
&&

.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:   JK
LONG TERM:    NJJ
AVIATION:     MEADE 
MARINE:       MJS
HYDROLOGY:    MJS