FXUS63 KGRR 272354
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
654 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...(654 PM EST FRI NOV 27 2009)
LIMITED AVIATION CONCERNS IN THE NEXT 24 HOURS. MAIN ISSUE IS THE 
TIMING OF THE MVFR CEILINGS CLEARING OUT FROM WEST TO EAST. AS THE 
RIDGE OF HIGH PRESSURE MOVES ACROSS THE LAKE THIS EVENING WARMER AIR 
WILL BEGIN TO PUSH INTO THE REGION FROM THE WEST. THE WARMER AIR 
WILL KNOCK OUT THE LAKE EFFECT CLOUDS CURRENTLY STREAMING ACROSS THE 
TAF SITES. EXPECTATION IS THAT BETWEEN ABOUT 03Z AND 07Z THE CLOUDS 
SHOULD CLEAR FROM WEST TO EAST. AFTER ABOUT 07Z...VFR CONDITIONS ARE 
THEN EXPECTED TO PREVAIL ALL THE WAY INTO TOMORROW EVENING. WINDS 
SHOULD GENERALLY BE BELOW 10 KNOTS THE 24 HOURS AND NOT A CONCERN.

&&

.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