FXUS63 KIND 262033
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
335 PM EST SAT DEC 26 2009

.DISCUSSION...DEEP UPPER LOW CENTERED OVER WISCONSIN WILL DOMINATE 
OUR WEATHER BEFORE IT MOVES EASTWARD BEGINNING LATE SUNDAY.  MODELS 
HAVE BEEN CONSISTENT PAST FEW RUNS IN GIVING UP SOME MEASURABLE SNOW 
AS THIS SYSTEM STARTS TO MOVE BY ON SUNDAY.  THUS THE MAIN FORECAST 
CONCERNS ARE SNOW CHANCES SUNDAY AND HOW MUCH SNOW WILL FALL.  ALSO 
TEMPERATURES NEXT SEVERAL DAYS AND HOW LONG TO KEEP ANY RESIDUAL 
LAKE EFFECT SNOW IN OUR NORTH AFTER THIS SYSTEM MOVES BY.

IN THE SHORT TERM NAM...GFS AND GEM MODELS ARE IN GENERAL AGREEMENT 
AND WILL USE BLEND.  THERE IS PRESENTLY AN AREA OF SNOW OVER CENTRAL 
ILLINOIS AND THIS MAY ROTATE ACROSS OUR NORTHWEST ZONES THIS EVENING 
PRODUCING LIGHT SNOW AMOUNTS THERE.  AS THE MAIN SHORT WAVE LOBE 
ROTATES ACROSS OUR REGION MODELS GIVE .1 TO .2 INCHES OF 
PRECIPITATION WHICH WOULD TRANSLATE TO 1 TO 2 INCHES OF SNOW. SNOW 
WILL END OVER ALL SECTIONS SUNDAY NIGHT AS THIS SYSTEM MOVES 
EASTWARD...BUT LAKE EFFECT FLURRIES MAY LINGER ON INTO OUR NORTH ON 
MONDAY.

CONCERNING TEMPERATURES WENT CLOSER TO A BLEND OF NAM SURFACE 
TEMPERATURES AND MET TEMPERATURES.  ASSUMING THERE MAY BE A LITTLE 
SNOW COVER ACROSS OUR NORTH AND CENTRAL WENT ON THE LOW SIDE OF 
GUIDANCE NUMBERS SUNDAY NIGHT THROUGH TUESDAY.

MODELS MOVE A WEAK UPPER RIDGE ACROSS OUR REGION AROUND TUESDAY. BY 
WEDNESDAY THERE IS A SPLIT FLOW OVER THE WESTERN U.S.  THERE IS ONE 
UPPER DISTURBANCE IN THE SOUTHERN STREAM OVER THE SOUTHWEST U.S. 
WHILE ANOTHER UPPER SYSTEM IN THE NORTHERN STREAM STARTS TO DIG 
ACROSS SOUTHWEST TEXAS.  THE GFS KEEPS THESE SYSTEMS SEPARATE UNTIL 
THE SOUTHERN SYSTEM PASSES BY...WHILE THE EUROPEAN SHOWS MUCH MORE 
PHASING BETWEEN THE NORTHERN AND SOUTHERN SYSTEMS.  MODELS HAVE 
TRENDED A TAD SLOWER SO WILL DROP PRECIPITATION CHANCES MOST AREAS 
FOR WEDNESDAY MORNING. I HAVE DECIDED TO NOT MAKE ANY SIGNIFICANT 
CHANGES IN THE LATER PERIODS FROM HPC NUMBERS BECAUSE OF UNCERTAINTY 
BETWEEN DIFFERENT MODELS IN THE EXTENDED PERIOD REGARDING SNOW 
CHANCES.  EITHER CASE TEMPERATURES WILL BECOME QUITE COLD NEAR END 
THE END OF THE 7 DAY PERIOD.

&&

.AVIATION...DISCUSSION FOR 26/18Z TAFS

AREA OF LIFT ACROSS ILLINOIS WILL DRIFT EAST TOWARD THE TAF SITES 
THIS AFTERNOON. BEST FORCING LOOKS TO BE NORTH OF THE AREA...SO KLAF 
HAS THE BEST CHANCE TO SEE SNOW. WILL CONTINUE TO GO MVFR CEILINGS 
AND VISIBILITIES IN LIGHT SNOW FOR SEVERAL HOURS LATE THIS AFTERNOON 
INTO THIS EVENING THERE. CHANCES DIMINISH TO THE SOUTH...BUT LOOKING 
UPSTREAM THERE ARE STILL SOME SITES WITH MVFR CONDITIONS IN LIGHT 
SNOW...SO WILL ALSO KEEP THESE CONDITIONS IN THE FORECAST AT HUF/IND 
FOR A FEW HOURS IN A SIMILAR TIME PERIOD. WILL KEEP VISIBILITIES A 
LITTLE HIGHER AT THOSE SITES THOUGH. BMG LOOKS TO BE FAR ENOUGH 
SOUTH FOR NOTHING OTHER THAN A CONTINUED VCSH MENTION.  OUTSIDE THE 
SNOW SHOWERS EXPECT LOW VFR CEILINGS. WINDS WILL CONTINUE TO GUST 
OVER 20KT INTO THE EVENING HOURS AT ALL SITES.

AFTER FIRST WAVE MOVES PAST...THE OVERNIGHT SHOULD BE DRY FOR THE 
MOST PART. MORE WIDESPREAD SNOW LOOKS TO IMPACT THE TAF SITES AFTER 
12Z SUNDAY WITH LOW MVFR CONDITIONS FORECAST AT THE MOMENT. COULD BE 
IFR CONDITIONS IN HEAVIER SNOW SHOWERS...BUT THAT IS TOO FAR OUT TO 
PUT IN THE TAFS AT THE MOMENT.

&&

.IND WATCHES/WARNINGS/ADVISORIES...NONE. 

&&

$$

PUBLIC...JH
AVIATION...CS