FXUS61 KBUF 240847
AFDBUF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
347 AM EST THU DEC 24 2009

.SYNOPSIS...
HIGH PRESSURE CENTERED JUST WEST OF JAMES BAY WILL MOVE SLOWLY TO 
THE EAST AND BRING DRY WEATHER TODAY THROUGH MOST OF CHRISTMAS 
MORNING. MEANWHILE...LOW PRESSURE OVER THE LOWER MISSISSIPPI VALLEY 
WILL LIFT NORTH ACROSS THE MIDWEST AND SPREAD PRECIPITATION 
EAST ACROSS THE AREA CHRISTMAS AFTERNOON. TEMPERATURES WILL BE NEAR 
OR JUST ABOVE FREEZING ON CHRISTMAS DAY...WITH AREAS OF FREEZING 
RAIN POTENTIALLY IMPACTING TRAVEL.

&&

.NEAR TERM /THROUGH TONIGHT/...
REGIONAL RADARS SHOWING ONLY VERY LIGHT RETURNS AND SURFACE REPORTS 
SUGGESTING ONLY WIDELY SCATTERED FLURRIES. COULD SEE SOME FLURRY 
ACTIVITY LINGERING THROUGH SUNRISE BUT THAT SHOULD BE IT.

11-3.9 MICRON SATELLITE IMAGERY SHOWING ABUNDANT LOW LEVEL 
CLOUDINESS CONTINUING TO LINGER OVER THE AREA EARLY THIS MORNING. 
MODEL SOUNDINGS SHOWING A STRONG LOW LEVEL INVERSION WHICH WILL 
KEEP THIS MOISTURE TRAPPED UNDERNEATH FOR A GOOD PART OF THE 
MORNING...BEFORE THERE WILL BE A CHANCE FOR DRIER AIR TO MIX IT
OUT. MID AND UPPER LEVEL CLOUDINESS WORKING NORTHEAST ACROSS THE
MID MISSISSIPPI VALLEY AND OHIO VALLEY WILL SPREAD OVER THE AREA
THIS AFTERNOON AND TONIGHT. THEREFORE...THE COMBINATION OF LOW
CLOUDINESS THIS MORNING AND INCREASING MID AND UPPER CLOUDINESS
THROUGH THE DAY WILL RESULT IN GENERAL OVERCAST CONDITIONS THROUGH
TONIGHT...ALTHOUGH THERE WILL LIKELY BE A PERIOD FROM LATE THIS
MORNING THROUGH MID AFTERNOON WHERE SOME PARTIAL CLEARING WILL BE
POSSIBLE...IF THE UPSTREAM CLOUDINESS CAN THIN OUT SOME AS IT
APPROACHES THE LOWER LAKES.

DESPITE THE CLOUD COVER TODAY...TEMPERATURES WILL BE WARMER THAN 
THE PAST SEVERAL DAYS. HIGHS SHOULD BE MAINLY IN THE LOWER TO MID 
30S. THE LAST TIME BUFFALO...ROCHESTER AND WATERTOWN CRACKED THE 
FREEZING MARK WAS DECEMBER 15TH.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
MAIN FOCUS CONTINUES TO BE ON THE POTENTIAL FOR A MIX OF RAIN AND 
FREEZING RAIN ON CHRISTMAS DAY. LOW PRESSURE CENTERED OVER EASTERN 
TEXAS EARLY THIS THURSDAY MORNING WILL LIFT SLOWLY TO THE NORTH AND 
STALL OVER IOWA CHRISTMAS DAY AND NIGHT. A POTENT LOW LEVEL JET 
SURGING AHEAD OF THIS SYSTEM IS ALREADY PRODUCING A VARIETY OF PCPN 
...EXTENDING FROM THE LOWER MISSISSIPPI VALLEY TO THE UPPER
MIDWEST.

BY THE TIME THE PCPN REACHES OUR CWA FRIDAY...TEMPERATURES ALOFT 
(850 TEMPS AVERAGING AROUND +3C) WILL BE WARM ENOUGH FOR RAIN. 
THE MAIN QUESTION IS HOW COLD WILL THE SURFACE TEMPERATURES BE WHEN 
THE RAIN ARRIVES. THE OPERATIONAL MODELS AND LATEST SFEF GUIDANCE 
ARE IN GOOD AGREEMENT THAT LIGHT RAIN WILL REACH THE WESTERN 
SOUTHERN TIER FRIDAY MORNING...THEN SPREAD NORTHEAST ACROSS THE REST 
OF THE AREA DURING THE AFTERNOON...WHILE STAYING JUST WEST OF KART 
THROUGH 00Z. 

THE LATEST TEMPERATURE GUIDANCE SUGGESTS THAT SURFACE TEMPERATURES 
WILL REMAIN AT OR JUST BELOW FREEZING THROUGH MID AFTERNOON ACROSS 
THE INTERIOR SECTIONS OF THE SOUTHERN TIER (MAINLY CATTARAUGUS AND 
ALLEGANY COUNTIES). THIS IS THE AREA WHERE THE THREAT FOR FREEZING 
RAIN APPEARS TO BE GREATEST FOR CHRISTMAS DAY. TEMPERATURES ACROSS 
MOST OF THE REST OF THE CWA ARE EXPECTED TO BE ABOVE FREEZING WHEN 
THE RAIN BEGINS. 

STEADY RAIN WILL CONTINUE TO SPREAD ACROSS THE AREA CHRISTMAS NIGHT 
AS A 50 TO 60 KNOT LOW LEVEL JET TRACKS EAST ACROSS THE AREA. THE 
MAIN FOCUS FOR FREEZING RAIN WILL SHIFT TO THE HIGHER ELEVATIONS 
EAST OF LAKE ONTARIO WHERE SURFACE TEMPERATURES MAY STAY BELOW 
FREEZING MOST OF THE NIGHT.  

ON SATURDAY...AN OCCLUDED FRONT THAT EXTENDS WELL EAST OF THE PARENT 
LOW IS FORECAST TO PUSH EAST ACROSS WESTERN AND CENTRAL NEW YORK. 
EXPECT THE STEADIEST RAIN TO TAPER OFF FROM WEST TO EAST DURING THE 
AFTERNOON AS A DRY SLOT WORKS IN BEHIND THE FRONT. STILL LOOKS LIKE 
RAIN WILL BE THE DOMINANT PCPN TYPE...BUT A FEW POCKETS OF FREEZING 
RAIN MAY LINGER EAST OF LAKE ONTARIO WHERE TEMPERATURES MAY HOVER 
AROUND 32. 

AS COLDER AIR WORKS IN FROM THE WEST SATURDAY NIGHT...LINGERING RAIN 
SHOWERS WILL GRADUALLY CHANGE TO SNOW. THE GFS BRINGS THE COLDER AIR 
IN FASTER THAN THE NAM AND ECMWF. FOLLOWING THE TREND OF THESE TWO 
MODELS...WILL DELAY THE CHANGEOVER TO SNOW UNTIL A LITTLE AFTER 
MIDNIGHT.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
THE UPPER LOW PASSES NEAR THE REGION SUNDAY...BRINGING A CHANCE OF 
SNOW SHOWERS. DEPENDING ON THE TRACK OF THE UPPER LOW...MAY ALSO SEE 
LAKE EFFECT KICK IN ON A SOUTHWEST FLOW AS 850 MB TEMPS DROP TO 
ABOUT -11C RESULTING IN MARGINAL LAKE INDUCED CAPES. THE UPPER LOW 
MOVES EAST ON MONDAY...AND INTO THE MARITIMES TUESDAY...BRINGING 
PROGRESSIVELY COLDER AIR INTO THE REGION. ON TUESDAY...850 MB 
TEMPERATURES MAY DIP TO INTO THE MINUS LOWER 20S BEHIND A PASSING 
COLD FRONT. CORRESPONDING SURFACE TEMPERATURES MAY STRUGGLE TO GET 
ABOVE 20. 

IN TERMS OF THE POTENTIAL FOR LAKE EFFECT SNOW...EXACT WIND 
DIRECTIONS ARE HARD TO PIN DOWN. GENERALLY EXPECT SW WINDS TO SHIFT 
MORE NW WITH TIME. 

HIGH PRESSURE BUILDS IN ON WEDNESDAY...WITH A CONTINUATION OF COLD 
TEMPERATURES...BUT DIMINISHING CHANCES FOR PRECIPITATION.

&&

.AVIATION /09Z THURSDAY THROUGH MONDAY/...
INCREASING SUBSIDENCE ASSOCIATED WITH A RIDGE BUILDING EASTWARD
FROM THE CENTRAL GREAT LAKES REGION WILL CONTINUE TO TRAP LOW
LEVEL MOISTURE LINGERING ACROSS THE REGION. THIS WILL KEEP MVFR
CIGS ACROSS THE ENTIRE AREA...POSSIBLY LOWERING IF IFR OVER KJHW
OVERNIGHT. SOME CLEARING MAY BEGIN TO WORK INTO FAR SOUTHWESTERN
NY STATE IN CONJUNCTION WITH THE ARRIVAL OF THE SURFACE RIDGE
AXIS AFTER DAYBREAK...THOUGH THE PROGRESSION OF ANY SUCH CLEARING ACROSS
THE REST OF THE AREA ON THURSDAY IS LIKELY TO BE ON THE SLOW SIDE.
AS SUCH...HAVE KEPT THINGS ON THE PESSIMISTIC SIDE WITH MVFR CIGS
ACROSS THE REMAINING TAF SITES THROUGH MOST OF THURSDAY. CLEARING
AND VFR CONDITIONS ARE MUCH MORE LIKELY IN THE LAST 6 HOURS OF
THIS 06Z-06Z TAF CYCLE.

OUTLOOK... 
FRIDAY...VFR/MVFR CONDITIONS EARLY DETERIORATE TO
IFR/MVFR IN RAIN AND PATCHY FREEZING RAIN. 
SATURDAY...IFR/MVFR WITH RAIN CHANGING TO SNOW FROM WEST TO EAST.
SUNDAY AND MONDAY...MVFR/VFR WITH A CHANCE OF SNOW SHOWERS.

&&

.MARINE...
SMALL CRAFT ADVISORIES HAVE BEEN DISCONTINUED. WINDS WILL CONTINUE 
TO DIMINISH THROUGH TONIGHT AS HIGH PRESSURE RIDGES IN. SMALL CRAFT 
ADVISORY CONDITIONS ARE LIKELY TO DEVELOP FRIDAY AND SATURDAY AS LOW 
PRESSURE APPROACHES FROM THE MIDWEST.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...NONE.
MARINE...NONE.

&&

$$

SYNOPSIS...TJP
NEAR TERM...TMA
SHORT TERM...TJP
LONG TERM...APFFEL/TJP
AVIATION...JJR/SAGE
MARINE...TJP