FXUS63 KGRR 280458
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1158 PM EST FRI NOV 27 2009

LATEST UPDATE...AVIATION...

.SYNOPSIS...(330 PM EST FRI NOV 27 2009)
AFTER QUIET WEATHER TONIGHT AND SATURDAY...RAIN WILL RETURN TO THE 
FORECAST SUNDAY WITH THE APPROACH OF ANOTHER COLD FRONT. THERE IS 
POTENTIAL FOR SIGNIFICANTLY COLDER CONDITIONS BY THE END OF THE 
COMING WORK WEEK...WITH LAKE EFFECT SNOW A DISTINCT POSSIBILITY. 

&&

.SHORT TERM...(330 PM EST FRI NOV 27 2009)
(TODAY THROUGH SATURDAY)
MAIN FORECAST CONCERN IS SKY COVER. NO SIGNIFICANT CHANGES WERE MADE 
TO THE PREVIOUS FORECAST. 

APPEARS THAT LAKE ENHANCED CLOUDINESS WILL PERSIST AT LEAST THROUGH 
THE AFTERNOON HOURS. KBIV HAD RECENTLY REPORTED LIGHT SNOW IN A 
HORIZONTAL CONVECTIVE ROLL INDUCED SNOW BAND. NO ADDITIONAL 
ACCUMULATIONS ARE EXPECTED. ANY LINGERING LAKE EFFECT PRECIPITATION 
WILL SHUT DOWN BY THIS EVENING AS INCREASINGLY ANTICYCLONIC FLOW 
WORKS INTO THE AREA. WE CONTINUE TO EXPECT CLEARING TO COMMENCE WELL 
BEFORE SUNRISE SATURDAY...ALLOWING FOR MINIMUM TEMPERATURES BELOW 
FREEZING. RELATIVELY CLEAR CONDITIONS SHOULD CONTINUE DURING THE DAY 
SATURDAY.

&&

.LONG TERM...(330 PM EST FRI NOV 27 2009)
(SATURDAY NIGHT THROUGH FRIDAY)

DRY WX IS ANTICIPATED SATURDAY NIGHT BEFORE A WEAK LOW PRESSURE 
SYSTEM BRINGS A CHC OF SHOWERS SUNDAY. A COUPLE OF SHORTWAVES WILL 
DIVE IN FROM THE NW AND BRING A CONTINUED CHC FOR PCPN SUNDAY NIGHT 
THROUGH MONDAY NIGHT...ALTHOUGH DUE TO LACK OF MOISTURE MOST OF 
THAT TIME PERIOD WILL BE DRY. PREDOMINANTLY DRY WX WILL CONTINUE 
TUESDAY THROUGH WEDNESDAY. 

12Z GFS GUIDANCE HAS TRENDED MUCH COLDER FOR LATE IN THE WEEK. 12Z 
ECMWF GUIDANCE CONTINUES TO LOOK COLD AND HAS 850 MB TEMPS DOWN TO 
-12 TO -14 C FROM THURSDAY NIGHT THROUGH NEXT WEEKEND. 12Z FIM 
GUIDANCE TAKES 850 MB TEMPS DOWN TO AT LEAST -10 C BY THURSDAY 
EVENING TOO. 

THEREFORE... BASED ON ALL OUR LATEST MEDIUM RANGE GUIDANCE AND 
TRENDS INFORMATION OUR CONFIDENCE IS INCREASING THAT OUR FIRST SHOT 
OF MUCH COLDER AIR AND POTENTIALLY OUR FIRST SIGNIFICANT LAKE EFFECT 
SNOW EVENTS WILL OCCUR LATE NEXT WEEK. LES POTENTIAL WILL BE 
MODULATED BY NUMEROUS OTHER FACTORS INCLUDING INVERSION HEIGHTS... 
DEPTH OF MOISTURE... UPSTREAM RH AND WIND SPEED/DIRECTION AND SHEAR 
BY THEN WHICH ARE MUCH TOO EARLY TO DETERMINE AT THIS TIME. 

&&

.AVIATION...(1158 PM EST FRI NOV 27 2009)
CLEARING LINE IS PROGRESSING EAST ACROSS THE CWA...WITH KJXN AND 
KLAN PROJECTED TO SCATTER OUT BY 09Z. KAZO AND KBTL HAVE ALREADY 
SCATTERED OUT. KMKG AND KGRR ARE A BIT MORE DIFFICULT. SOME LAKE 
EFFECT STRATOCUMULUS CONTINUES TO BE GENERATED OFF LAKE MICHIGAN 
BEHIND THE CLEARING LINE...AFFECTING BOTH KMKG AND KGRR. EXPECT 
SCT-BKN CONDITIONS TO PERSIST THE NEXT FEW HOURS AT KMKG AND KGRR 
WITH THEM BOTH CLEARING OUT FOR GOOD BY MORNING. AFTER THE 
STRATOCUMULUS EXITS THROUGH THE COURSE OF THE NIGHT...SATURDAY IS 
EXPECTED TO BE MAINLY CLEAR AND VFR. SOME STRATOCU MAY TRY TO PUSH 
BACK INTO THE TAF SITES TOMORROW EVENING IN THE 03Z-06Z TIME 
FRAME...BUT DID NOT TIME THAT INTO THE TAFS AT THIS POINT.

&&

.MARINE...(531 PM EST FRI NOV 27 2009)
HIGH PRESSURE RIDGE BUILDING INTO THE REGION THIS EVENING HAS 
BROUGHT WINDS DOWN UNDER 15 KNOTS AT ALL THE COASTAL SITES. WINDS 
THIS EVENING WILL BE UNDER 10 KNOTS...BECOMING SOUTHWEST AT 5 TO 15 
KNOTS LATE. THE SMALL CRAFT ADVISORY WAS ALLOWED TO EXPIRE AS 
WEBCAMS SHOWED WAVES HAD SUBSIDED ALONG WITH THE WINDS. WINDS 
SHOULD GENERALLY BE IN THE 1-3 FOOT RANGE THE REMAINDER OF THE 
NIGHT. 

&&

.HYDROLOGY...(330 PM EST FRI NOV 27 2009)
NO HYDRO ISSUES IN THE SHORT TERM. PRECIPITATION SUNDAY SHOULD 
REMAIN LIGHT.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.

&&

$$

SYNOPSIS:     TJT
SHORT TERM:   TJT
LONG TERM:    LAURENS
AVIATION:     DUKE
MARINE:       DUKE
HYDROLOGY:    TJT