FXUS63 KGRR 241250
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
750 AM EST THU DEC 24 2009

LATEST UPDATE...SYNOPSIS/SHORT TERM...

.SYNOPSIS...(750 AM EST THU DEC 24 2009)
A DEEP LOW OVER THE PLAINS WILL DRAW ABUNDANT MOISTURE NORTH FROM 
THE GULF OF MEXICO. FREEZING RAIN AND SLEET WILL MOVE INTO LOWER 
MICHIGAN TODAY AND TONIGHT...RESULTING IN SOME ICY ROADS. THESE ICY 
CONDITIONS WILL CONTINUE INTO FRIDAY MORNING BEFORE WARMER AIR WILL 
ARRIVE AND TURN THE PRECIPITATION OVER TO RAIN. HOWEVER NORTH OF 
M-46...THE FREEZING RAIN MAY LINGER INTO THE AFTERNOON. COLDER AIR 
WILL THEN WRAP INTO LOWER MICHIGAN FROM THE SOUTH CHRISTMAS 
AFTERNOON. LIGHT RAIN WILL TURN TO SCATTERED SNOW SHOWERS. THE 
COLDER AIR WILL LINGER THROUGH THE WEEKEND ALONG WITH SNOW SHOWERS. 

&&

.SHORT TERM...(750 AM EST THU DEC 24 2009)
(TODAY THROUGH SATURDAY)
FREEZING RAIN AND SLEET HAVE TAPERED OFF FOR NOW AND THE ADVISORY 
FOR THE WESTERN FORECAST AREA WILL BE CANCELLED AN HOUR EARLY. 
HOWEVER...THERE IS A SOLID AREA OF PRECIPITATION SEEN ON RADAR 
ACROSS CENTRAL AND SOUTHERN INDIANA ASSOCIATED WITH STRONG 
WAA/ISENTROPIC UPGLIDE AND THIS IS MOVING NORTH. IF IT HOLDS 
TOGETHER THE START TIME FOR THE ADVISORY FOR TONIGHT WILL NEED TO BE 
BUMPED UP A FEW HOURS. REST OF PREVIOUS DISCUSSION FOLLOWS.

CONFIDENCE IS HIGH THAT WE/LL SEE FREEZING RAIN TONIGHT. SLEET IS A 
GOOD BET TOO. FORECAST SOUNDINGS SHOW A PRONOUNCED WARM INTRUSION 
AROUND H8. PCPN WILL FORM AS RAIN AND HIT THE GROUND AS FZRA/SLEET. 
TIMING IS IN QUESTION. THE GFS BRINGS IN THE PCPN PRIOR TO 00Z. SO 
DOES THE FIM. BUT THE NAM/ECMWF/SREF DON/T REALLY BRING IN PCPN 
UNTIL AFTER 06Z. GIVEN THE UNCERTAINTY...WE ISSUED A WINTER WX 
ADVISORY BEGINNING AT 00Z. IT RUNS THROUGH 22Z FRIDAY. 

TEMPS ARE FCST TO WARM TOWARD 12Z FRIDAY. THIS SHOULD TURN THE FZRA 
TO RAIN. THE DRY AIR ADVECTING IN FROM THE EAST MAY DELAY THE TURN 
OVER HOWEVER. IT/S ALSO POSSIBLE THAT SECONDARY ROADS MAY REMAIN 
SLICK FOR A WHILE LONGER. RATHER THAN ISSUE MULTIPLE ADVISORIES FOR 
TONIGHT AND FRIDAY FOR BASICALLY THE SAME TYPE OF WEATHER AND 
CONFUSE THINGS WE/LL RUN WITH ONE AND MENTION THE TIMING ISSUES IN 
THE TEXT. WE CAN ALSO CANCEL COUNTIES FROM SOUTH TO NORTH FRIDAY AS 
CONDITIONS PERMIT.

THIS IS AN OCCLUDED SYSTEM SO COLDER AIR WILL WRAP IN AROUND IT AND 
WE/LL SEE IT DEVELOP FROM SOUTH TO NORTH. ACROSS THE SRN CWA FRIDAY 
AFTERNOON THE RAIN WILL CHANGE BACK TO SHSN. OVER THE NORTH...WHERE 
THE FZRA HAS THE HIGHEST CHANCE OF LINGERING THE LONGEST...THE FZRA 
WILL TURN BACK TO SHSN AFTER 18Z. BY THAT TIME THE DRY SLOT WILL BE 
WORKING IT/S WAY INTO THE CWA...SO ANY ACCUMS WILL BE KEPT TO A 
MINIMUM. 

WE EXPECT WINDS TO KICK UP...ESPECIALLY ALONG THE LAKE SHORE. 3HRLY 
PRESSURE RISES IN THE 4-5MB RANGE ARE PROGD. THIS IS AN INCREASE 
OVER YESTERDAY/S RUNS. ANY ICING WE GET WILL BE EXACERBATED BY THE 
WIND. THIS MAY LEAD TO SPORADIC POWER OUTAGES. 

SHSN WILL CONTINUE THROUGH SATURDAY AS THE UPPER LOW MOVES TOWARD 
THE CWA AND COLD AIR REMAINS IN PLACE.

&&

.LONG TERM...(310 AM EST THU DEC 24 2009)
(SATURDAY NIGHT THROUGH WEDNESDAY)
OCCLUDED LOW MOVING THROUGH OVER THE WEEKEND WILL BRING SNOW SHOWERS 
AND POSSIBLY SOME ACCUMULATIONS IN THE 2 TO 4 INCH RANGE WITH LAKE 
ENHANCEMENT. WILL HAVE 50 POPS FOR SATURDAY NIGHT AND SUNDAY BUT 
WILL PROBABLY NEED LIKELY ONCE THE TIMING IS PINNED DOWN A LITTLE 
BETTER. LAKE EFFECT SNOW SHOWERS ON THE BACK SIDE OF THE UPPER LOW 
PASSAGE BUT THESE WILL BE WINDING DOWN BY TUESDAY AS SFC RIDGING 
BUILDS IN.

.AVIATION...(621 AM EST THU DEC 24 2009)
SOME LOW CLOUDS OFF LAKES HURON AND ERIE HAVE MADE IT INTO JXN AND 
LAN SIMILAR TO YESTERDAY...SO CEILINGS WILL BE DOWN AOB 1500 FEET 
AT TIMES THROUGH THE DAY. FREEZING RAIN SHOULD ARRIVE LATER THIS 
AFTERNOON OR EVENING AND CONTINUE TONIGHT...SO ICING WILL BE A 
PROBLEM UNTIL TEMPS GET ABOVE FREEZING AFTER MIDNIGHT TONIGHT.

&&

.MARINE...(310 AM EST THU DEC 24 2009)
GALE WARNING REMAINS FOR ENE WINDS GUSTING TO 40 KNOTS THROUGH 
CHRISTMAS DAY. 
&&

.HYDROLOGY...(310 AM EST THU DEC 24 2009)
QPF POTENTIAL THURSDAY NIGHT AND FRIDAY WILL NOT BE HIGH ENOUGH TO 
CAUSE HYDRO ISSUES.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY TONIGHT AND FRIDAY ENTIRE CWA. 

LM...GALE WARNING FROM MIDDAY TODAY THROUGH FRIDAY AFTERNOON FOR 
     THE ENTIRE NEAR SHORE.

&&

$$

SYNOPSIS:     93/OSTUNO
SHORT TERM:   93/OSTUNO
LONG TERM:    OSTUNO
AVIATION:     OSTUNO
MARINE:       93
HYDROLOGY:    93