FXUS63 KGRR 292022
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
322 PM EST SUN NOV 29 2009
LATEST UPDATE...ALL SECTIONS EXCEPT AVIATION...
.SYNOPSIS...(322 PM EST SUN NOV 29 2009)
LOW PRESSURE WILL EXIT THE REGION THIS EVENING BRINGING AN END TO
THE LIGHT RAIN AND SNOW OVERNIGHT. MONDAY MORNING WILL BE DRY...
HOWEVER ANOTHER TROUGH OF LOW PRESSURE WILL MOVE TOWARD THE STATE
LATE IN THE DAY AND COULD BRING SCATTERED LIGHT SNOW BACK TO THE
AREA. THE SNOW WILL BECOME ENHANCED BY LAKE MICHIGAN MONDAY
EVENING. AREAS NORTH OF INTERSTATE 96 AND INLAND FROM THE LAKE
COULD SEE UP TO AN INCH OF SNOW ACCUMULATION BY EARLY TUESDAY
MORNING. TUESDAY AND TUESDAY NIGHT LOOK DRY AS HIGH PRESSURE FLOATS
BY.
&&
.SHORT TERM...(322 PM EST SUN NOV 29 2009)
(TONIGHT THROUGH TUESDAY NIGHT)
THE MAIN FORECAST FOCUS WAS ON THE DEPARTING SYSTEM TONIGHT. THEN
THE ATTENTION TURNS TO A SURFACE TROUGH THAT WILL MOVE ACROSS THE
REGION MONDAY NIGHT. IN BETWEEN THESE SYSTEMS LAKE EFFECT POTENTIAL
NEEDED TO BE EVALUATED.
WILL BUMP POPS UP FOR THIS EVENING ACROSS MUCH OF THE CWA AS THE
DEEPER MOISTURE LINGERS OVER THE AREA. THE SHORT WAVE TROUGH DOES
NOT PIVOT THROUGH UNTIL AFT 06Z WHEN THE MOISTURE FINALLY SUBSIDES.
WILL CONTINUE TO MENTION A RAIN/SNOW MIX AS THICKNESS VALUES FALL
WITH THE APPROACHING WAVE. IT IS DOUBTFUL THERE WILL BE ANY
ACCUMULATION SINCE SURFACE TEMPS WILL BE STAYING ABOVE FREEZING MUCH
OF THE NIGHT. ONCE THE WAVE IS THROUGH...ANY LAKE EFFECT WILL BE
MINIMAL MAINLY DUE TO SURFACE RIDGING ALREADY BUILDING IN PRIOR TO
DAYBREAK MONDAY.
WILL REMOVE THE LOW CHANCE POPS MONDAY MORNING AS THE SURFACE RIDGE
WILL BE IN PLACE. HOWEVER...BY LATER IN THE DAY A SURFACE TROUGH
WILL APPROACH THE AREA. A RATHER SHEARED UPPER SHORT WAVE
ACCOMPANIES THE TROUGH. NOT AN OVERLY IMPRESSIVE SYSTEM...SO WILL
JUST LEAVE LOW CHANCE POPS IN FOR THE AFTERNOON.
THE SHORT WAVE ITSELF AND DEEPER MOISTURE ARRIVES MONDAY NIGHT. WE
SHOULD ALSO SEE A BOOST FROM THE LAKE. HAVE DECIDED TO INCREASE
POPS TO LIKELY ALONG THE LAKE AND ACROSS THE NORTHERN HALF OF THE
CWA. THIS APPEARS TO BE MAINLY AN EVENING EVENT...WITH THE PCPN
DIMINISHING AFTER MIDNIGHT AS THE WAVE PASSES. PCPN TYPE SHOULD BE
MAINLY SNOW...WITH A MIX OVER THE SW CORNER. SOME AREAS NORTH OF
I-96 AND INLAND FROM THE LAKE COULD SEE UP TO AN INCH OF SNOW
ACCUMULATION ON GRASSY AREAS BY EARLY TUESDAY MORNING.
WILL MAINTAIN THE DRY FORECAST FOR TUESDAY AND TUESDAY NIGHT. THERE
WILL BE A NORTHERN STREAM SYSTEM APPROACHING...BUT THIS SHOULD
MAINLY IMPACT NORTHERN LOWER AND THE U.P.
&&
.LONG TERM...(322 PM EST SUN NOV 29 2009)
(WEDNESDAY THROUGH SUNDAY)
VERY FEW LONG RANGE FCST CHANGES WERE NECESSARY. 12Z GFS/ECMWF/FIM
GUIDANCE CONTINUES TO SUGGEST THAT THE GULF COAST LOW WILL STAY FAR
ENOUGH EAST OF OUR AREA (ALONG THE APPALACHIANS) LATE WEDNESDAY
NIGHT AND THURSDAY SUCH THAT WE WILL MISS OUT ON THE SYNOPTIC PCPN
FROM THAT SYSTEM.
HOWEVER WE WILL BE IN A STRONG WNW FLOW CAA REGIME THURSDAY THROUGH
FRIDAY LEADING TO LAKE EFFECT SNOW AS 850 MB TEMPS FALL TO AT LEAST
-10 TO -12 C BY THURSDAY NIGHT. MAX TEMPS THURSDAY AND FRIDAY WILL
ONLY REACH THE LOWER 30S. WE HAVE EXPANDED THE AREA OF LIKELY POPS
FOR LAKE EFFECT SNOW SHOWERS TO ENCOMPASS THE WESTERN HALF OF OUR
CWFA...WITH HIGH CHC POPS FURTHER INLAND. THE THOUGHT IS THAT WNW
WINDS WILL BE BRISK ENOUGH TO CARRY SNOW SHOWERS WELL INLAND.
THIS CERTAINLY HAS POTENTIAL TO BE THE FIRST SIGNIFICANT LAKE EFFECT
SNOW EVENT OF THE SEASON FOR PORTIONS OF OUR CWFA...PARTICULARLY IN
OUR FAVORED WNW FLOW SNOW BELT AREAS. MUCH WILL DEPEND ON NUMEROUS
OTHER FACTORS THOUGH INCLUDING INVERSION HEIGHTS...DEPTH OF MOISTURE
AND UPSTREAM RH AND AMOUNT OF WIND SPEED/DIRECTIONAL SHEAR WITH
HEIGHT. IT IS STILL A LITTLE TOO EARLY TO DRILL DOWN INTO THOSE
TYPE OF SPECIFICS.
&&
.AVIATION...(1230 PM EST SUN NOV 29 2009)
MAINLY IFR CONDITIONS ARE ANTICIPATED THIS AFTERNOON AT ALL THE
TERMINALS DUE TO LOW CLOUDS AND LINGERING LIGHT RAIN SHOWERS.
CONDITIONS WILL GRADUALLY IMPROVE INTO THE MVFR FLIGHT CATEGORY
OVERNIGHT AS CEILINGS BEGIN TO IMPROVE.
A FEW VERY LIGHT LAKE EFFECT SNOW SHOWERS OR FLURRIES MAY CLIP THE
MUSKEGON TERMINAL OVERNIGHT. HOWEVER WE DID NOT FEEL CONFIDENT
ENOUGH IN THE PCPN POTENTIAL TO INCLUDE MENTION OF IT IN THE FCST
FOR THE MUSKEGON TERMINAL. IT SEEMS THE BETTER CHANCE FOR LAKE
EFFECT PCPN WILL BE NORTH OF MKG.
PREDOMINANTLY VFR CONDITIONS ARE ANTICIPATED MONDAY AS CIGS IMPROVE
TO GREATER THAN 3000 FEET AGL. THERE MAY BE SOME ICING IN THE LAYER
FROM 1000 FT TO 8000 FT DURING THE DAY MONDAY.
&&
.MARINE...(322 PM EST SUN NOV 29 2009)
A SMALL CRAFT ADVISORY WAS ALREADY IN EFFECT. WINDS AND WAVES WILL
BE BUILDING THIS EVENING AND WILL REMAIN HAZARDOUS TO SMALL CRAFT
INTO TUESDAY AFTERNOON.
&&
.HYDROLOGY...(322 PM EST SUN NOV 29 2009)
NO HYDRO ISSUES.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...SMALL CRAFT ADVISORY THROUGH TUESDAY AFTERNOON FROM ST JOSEPH
TO MANISTEE.
&&
$$
SYNOPSIS: JK
SHORT TERM: JK
LONG TERM: LAURENS
AVIATION: LAURENS
MARINE: JK
HYDROLOGY: JK
