FXUS63 KGRR 281649
AFDGRR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1145 AM EST SAT NOV 28 2009

LATEST UPDATE...AVIATION...

.SYNOPSIS...(346 AM EST SAT NOV 28 2009)
HIGH PRESSURE OVER THE AREA WILL RESULT IN QUITE A BIT OF SUNSHINE 
TODAY AND MILD TEMPERATURES. A COLD FRONT WILL MOVE THROUGH LOWER 
MICHIGAN LATE SUNDAY BRINGING LIGHT RAIN SHOWERS WITH IT. COLDER AIR 
BEHIND THE FRONT MAY GENERATE SOME LAKE EFFECT SNOW SHOWERS LATE 
SUNDAY NIGHT AND MONDAY BUT SIGNIFICANT SNOW IS NOT EXPECTED. 
ANOTHER SURGE OF COLDER AIR IS EXPECTED TUESDAY NIGHT. LAKE EFFECT 
SNOW SHOWERS ARE POSSIBLE FOR THE LATTER HALF OF THE WEEK.  

&&

.SHORT TERM...(346 AM EST SAT NOV 28 2009)
(TODAY THROUGH MONDAY)
FORECAST CONCERNS DEAL WITH PCPN TRENDS SUNDAY AND MONDAY. WE SHOULD 
SEE ABUNDANT SUNSHINE TODAY. LATEST IR LOOP SHOWS THE BACK EDGE OF 
THE STRATOCU HAS JUST CLEARED THE EASTERN CWA. HOWEVER...A SMALL 
AREA OF STRATOCU STILL EXISTS ALONG THE LAKE SHORE BUT THIS WILL MIX 
OUT SOON. H8 TEMPS CLIMBING TO +4C WILL HELP SFC TEMPS CLIMB INTO 
THE MID 40S TODAY AND SUNDAY.

A COLD FRONT WILL MOVE THROUGH SUNDAY. ALOFT...A SHARP TROUGH WILL 
ALSO MOVE ACROSS LOWER MICHIGAN. MOISTURE IS LIMITED WITH THIS 
SYSTEM BUT DPVA IS PRETTY STRONG SO WE/LL HAVE A CHC POP IN THE 
FORECAST. THE SHRA WILL MIX WITH AND CHANGE TO SNOW OVERNIGHT AS 
COLDER AIR FLOWS IN BEHIND THE FRONT. NOT LOOKING FOR MUCH. IN 
FACT...GIVEN THAT OMEGA IS NEGLIGIBLE AND THE DGZ LOOKS LIKE IT WILL 
NOT BE SATURATED SUNDAY NIGHT OR MONDAY...WE MIGHT SEE MORE 
FZDZ/FLURRIES THAN ANYTHING. HIGH TEMPS WILL COOL OFF INTO THE 30S 
BY MONDAY.

 

&&

.LONG TERM...(346 AM EST SAT NOV 28 2009)
(MONDAY NIGHT THROUGH FRIDAY)

THE MAIN CHALLENGE IN THE LONG TERM DEALS WITH TIMING THE 
ARRIVAL OF THE COLD AIR. DIFFERENCES ARE RATHER CONSIDERABLE AMONGST 
THE MODELS IN TERMS OF WHEN THE COLD AIR WILL ARRIVE.  THE GFS SHOWS 
A WEAK AND FAST MOVING MID LEVEL SHORTWAVE PUSHING THROUGH THE GREAT 
LAKES REGION TUE INTO TUE NIGHT.  THIS WOULD DRAW THE COLD AIR IN 
FOR WED.  THE ECMWF IS SLOWER AND STRONGER WITH THIS WAVE AND IS 
PHASING IT WITH THE SOUTHERN STREAM SYSTEM WED INTO THU.  THE ECMWF 
SCENARIO SUPPORTS A SURFACE LOW TRACKING UP WEST OF THE 
APPALACHIANS. THIS TRACK WOULD DELAY THE ARRIVAL OF THE COLD AIR 
UNTIL THU INTO FRI.  

I FAVOR THE ECMWF SOLUTION GIVEN THAT IT INITIALIZED THE MID TO  
UPPER LEVEL SYSTEM IN TERMS OF STRENGTH AND LOCATION...BETTER THAN 
THE GFS.  AS A RESULT I WILL FEATURE A RISE IN THE TEMPERATURES FOR 
WED...FOLLOWED BY COLDER AIR FOR THU AND FRI.

THE ECMWF SUPPORTS A BAND OF SNOW NORTHWEST OF THIS LOW TRACK ACROSS 
PARTS OF LOWER MICHIGAN LATER WED INTO WED NIGHT.  THIS WILL NEED TO 
BE MONITORED.  FROM ALL MODELS...LOOKS LIKE A SET UP FOR LAKE EFFECT 
SNOW AT SOME POINT IN THE THU TO FRI TIMEFRAME.  ALL MODELS SHOW 
MAINLY WESTERLY FLOW...SO THE LAKE EFFECT SNOW MAY END UP BEING 
LIMITED IN COVERAGE AND INTENSITY.  MOST  MODELS SHOW WARM AIR 
ADVECTION BY FRI NIGHT...BUT THE FIM SUPPORTS A LONGER DURATION OF 
THE COLD AIR.  

&&

.AVIATION...(1145 AM EST SAT NOV 28 2009)
VFR CONDITIONS WILL CONTINUE AT ALL TAF SITES THROUGH LATE THIS 
EVENING.  HOWEVER CONDITIONS ARE EXPECTED TO DETERIORATE RAPIDLY 
DURING THE EARLY MORNING HOURS SUNDAY (AROUND 09Z-10Z) AS LOW LEVEL 
MOISTURE INCREASES QUICKLY AHEAD OF THE APPROACHING COLD FRONT. THIS 
AND LIGHT WINDS WILL BE CONDUCIVE TO THE FORMATION OF A LOW STRATUS 
DECK WITH CLOUD BASES FROM AROUND 400 FEET TO A THOUSAND FEET AGL 
RESULTING IN A RAPID TRANSITION INTO IFR TO LIFR CONDITIONS. SOME 
LIGHT FOG IS ALSO POSSIBLE. 

WE EXPECT THE LOW STRATUS DECK WILL LINGER THROUGH 18Z RESULTING IN 
CONTINUED IFR TO LIFR CONDITIONS AT ALL TAF SITES THROUGH THEN. DRY 
CONDITIONS SHOULD PREVAIL THROUGH 18Z SUN. MOST OF OUR SHORT RANGE 
COMPUTER MODEL GUIDANCE SUCH AS LATEST SREF POPS AND 4KM WRF SIM 
REFLECTIVITY SUGGESTS LIGHT RAIN SHOWERS WILL NOT DEVELOP AT THE 
TERMINALS UNTIL JUST AFTER 18Z TOMORROW AFTERNOON. 

&&

.MARINE...(346 AM EST SAT NOV 28 2009)
HIGH PRESSURE OVER THE AREA WILL RESULT IN LIGHT WINDS AND 1-3 FT 
WAVES TODAY. 

&&

.HYDROLOGY...(346 AM EST SAT NOV 28 2009)
NO HYDRO ISSUES.

&&

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

&&

$$

SYNOPSIS:     93
SHORT TERM:   93
LONG TERM:    MJS
AVIATION:     LAURENS
MARINE:       93
HYDROLOGY:    93