FXUS63 KIND 220448
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1145 PM EST MON DEC 21 2009

.AVIATION...DISCUSSION FOR 22/06Z TAFS.
AREA OF SNOW SHOWERS ACROSS NORTHERN ILLINOIS WILL SPREAD ACROSS THE 
NORTHERN TWO THIRDS OF CENTRAL INDIANA AFTER 09Z AND CONTINUE TO 
ABOUT 15Z.  NAM MODEL INDICATE AN INCH OF SNOW MAY FALL AT KLAF WITH 
LESSER AMOUNTS FARTHER SOUTH.  WILL MENTION PREVAILING VISIBILITY OF 
2 MILES AT KLAF...BUT IT COULD DROP TO A MILE AT TIMES.

AFTER SNOW MOVES BY...MVFR CIGS WILL BE THE RULE AS SOME TRAPPING OF 
LOW LEVEL MOISTURE OCCURS. MODEL SOUNDINGS INDICATE LOW CLOUDS MAY 
BREAK UP SOME ACROSS SOUTHERN INDIANA AND WILL MENTION A PERIOD OF 
VFR CONDITIONS AT KBMG. OTHER TAFS MOST LIKELY WILL REMAIN 
MVFR...BUT THERE MAY BE SOME IMPROVEMENT TUESDAY AFTERNOON.

FINALLY NAM BRINGS RAIN INTO KHUF BY END OF THE TAF PERIOD AND 
FREEZING RAIN AT KIND AND KLAF AFTER 06Z WEDNESDAY. THIS MAY BE A 
LITTLE FAST SO WILL NOT MENTION IN THIS SET OF TAFS.

&&

.UPDATE...

SATELLITE SHOWING A RELATIVELY IMPRESSIVE UPPER WAVE MOVING THROUGH 
IOWA AT THE MOMENT. NEAR THE WAVE SNOW WAS SPREADING ACROSS IOWA. 
LOCAL RADARS SHOWING INCREASING VIRGA ACROSS ILLINOIS AHEAD OF THE 
SYSTEM...AND INCREASING RETURNS ACROSS NORTHERN MISSOURI AS WELL.

LATEST NAM/RUC MODELS SHOWING THAT AREA OF BEST FORCING WILL BE 
FARTHER SOUTH THAN PREVIOUSLY THOUGHT. THE MODELS THUS BRING IN MORE 
SNOW TO THE AREA...ESPECIALLY ACROSS NORTHWESTERN SECTIONS. THEY 
ALSO BRING IN SOME FRONTOGENETICAL FORCING WITH THE WAVE. GIVEN THE 
OBSERVED STRENGTH OF THE WAVE AND SOME SNOW ALREADY BREAKING OUT 
ACROSS MISSOURI...FEEL THAT HIGHER POPS ARE WARRANTED ACROSS PARTS 
OF THE FORECAST AREA. WENT LIKELY POPS IN THE LAFAYETTE AND KOKOMO 
AREAS WITH CHANCE POPS DOWN TO NEAR THE BLOOMINGTON AND COLUMBUS 
AREAS. 

HIGHEST ACCUMULATIONS WILL MOST LIKELY BE NORTH OF THE FORECAST 
AREA...BUT DID GO UP TO AN INCH ACROSS THE NORTHWEST FORECAST AREA. 

LITTLE CHANGE TO REMAINDER OF FORECAST AS IT WAS ON TRACK. 

THANKS TO NEARBY OFFICES FOR THE COLLABORATION THIS EVENING.

&&

.SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT...
LONG WAVE PATTERN EXPECTED TO REMAIN PROGRESSIVE OVER THE NEXT FEW 
DAYS. RIDGING CURRENTLY OVER THE ROCKIES EXPECTED TO PUSH EASTWARD 
INTO THE APPALACHIAN MOUNTAIN REGION BY THURSDAY...WITH THE NEXT 
STORM SYSTEM EXPECTED TO BE LOCATED IN THE SOUTHERN PLAINS BY THAT 
TIME. MODELS IN FAIRLY GOOD AGREEMENT ON THE MAIN FEATURES. FORECAST 
FOCUS CENTERS ON POPS AND PRECIPITATION TYPE OVER THE NEXT COUPLE OF 
DAYS.

MODEL DATA CONTINUE TO INDICATE AN AREA OF MID LEVEL FORCING ALONG 
WITH NEAR SATURATION IN THE PRECIPITATION BEARING LAYERS OVER THE 
NORTHERN SECTIONS OF THE FORECAST AREA DEVELOPING LATER TONIGHT AND 
INTO TUESDAY. SNOW CURRENTLY BREAKING OUT ACROSS SOUTH DAKOTA AND 
IOWA PROBABLY RELATED TO THIS. WILL KEEP CHANCE POPS GOING FOR LIGHT 
SNOW OVER ABOUT THE NORTHEAST TWO THIRDS OF THE AREA FOR LATE 
TONIGHT INTO TUESDAY AFTERNOON. POTENTIAL MAXIMUM SNOWFALL AMOUNTS 
WITH THIS SYSTEM LOOK TO BE QUITE LIGHT...AROUND 1/2 INCH OR SO.

ATTENTION THEN TURNS TO THE SYSTEM THAT WILL BE AFFECTING THE LOCAL 
AREA OVER THE SECOND HALF OF THE WEEK. OPERATIONAL MODELS ALONG WITH 
THE ENSEMBLES CONVERGING ON PLACEMENT OF SURFACE LOW...IN THE 
VICINITY OF SOUTHWEST MISSOURI AND SOUTHEAST KANSAS BY THURSDAY 
MORNING. THE PRESENCE OF THE UPPER RIDGE AND A LARGE SURFACE HIGH 
EXPECTED TO BE OVER THE NORTHERN GREAT LAKES FUNNELING DRY AIR INTO 
THE SYSTEM SUGGESTS PRECIPITATION MAY HAVE A HARD TIME GETTING INTO 
THE LOCAL AREA THROUGH WEDNESDAY NIGHT...BUT ALSO SUGGESTS 
EVAPORATIVE COOLING PROCESSES MAY COME INTO PLAY REGARDING EVENTUAL 
PRECIPITATION TYPE. AS A RESULT...PLANNING ON CHANCE POPS IN THE 
SOUTHWEST FOR LATE TUESDAY NIGHT...AND CHANCE POPS ALL ARES 
WEDNESDAY AND WEDNESDAY NIGHT. CRITICAL THICKNESSES SUGGEST MAINLY A 
LIQUID OR FREEZING EVENT WITH LITTLE CHANCES OF SIGNIFICANT 
SNOWFALL. AT THIS TIME...BEST CHANCES FOR FREEZING RAIN APPEAR TO BE 
ALONG AND NORTHEAST OF INTERSTATE 74. BASED ON THE ABOVE 
REASONING...EXPECTING ANY PRECIPITATION THAT OCCURS WILL BE RATHER 
LIGHT. NO HEADLINES PLANNED AT THIS TIME.

DON/T HAVE A MAJOR PROBLEM WITH THE GFS MOS TEMPS BASED ON LOW LEVEL 
THICKNESSES...ALTHOUGH BY WEDNESDAY THE GUIDANCE MAY BE SEVERAL 
DEGREES TOO WARM. WILL NUDGE DOWN THE NUMBERS IN THAT 
PERIOD.

&&

.LONG TERM...THURSDAY THROUGH MONDAY...
MODEL CONSENSUS IS COMING INTO LINE ON THE LOW PRESSURE OCCLUDING 
SOMEWHERE OVER NORTHERN MISSOURI OR SOUTHERN IOWA BY THURSDAY 
NIGHT...WITH A SLOW NORTHEASTWARD PROGRESSION TO THE LOW THEREAFTER 
AS STRONG HIGH PRESSURE REMAINS IN THE WAY NORTH OF THE GREAT LAKES. 
TRACK DIFFERENCES HAVE BECOME RELATIVELY MINOR AT THIS POINT...AT 
LEAST WITH RESPECT TO PRECIPITATION TYPE OVER CENTRAL INDIANA. HAVE 
TAKEN A BLEND OF THE 12Z ECMWF AND GFS ENSEMBLE MEAN FOR THE TIME 
PERIOD. 

AM STILL A BIT CONCERNED THAT SURFACE TEMPERATURES MAY BE AT OR JUST 
BELOW 32F AT DAYBREAK THURSDAY...ESPECIALLY NORTHEAST OF INTERSTATE 
74. WILL THEREFORE ALLOW FOR A CONTINUATION FOR A CHANCE OF FREEZING 
RAIN TO START...GRADUALLY SHIFTING NORTH DURING THE MORNING. 
EVALUATION OF LOW LEVEL THICKNESSES AND SURFACE TEMPERATURES 
SUGGESTING PRECIPITATION SHOULD BE FALLING AS RAIN ACROSS THE ENTIRE 
FORECAST AREA BY MIDDAY THURSDAY OR SHORTLY THEREAFTER. HAVE SLOWED 
DOWN LIKELY POPS TO THURSDAY AFTERNOON AND NIGHT AS DEEPER FORCING 
ARRIVES AHEAD OF THE FRONTAL BOUNDARY. 50-60KT 850 LOW LEVEL JET 
SHOULD SERVE TO ENHANCE RAINFALL CONVERGE AND INTENSITY...WITH 
POTENTIAL FOR A SOLID 1 TO 1.50 INCHES ACROSS THE REGION. THIS COULD 
LEAD TO SOME LOCALIZED FLOODING ISSUES...ESPECIALLY ALONG THE 
STREAMS IN THE SOUTHERN FORECAST AREA WHICH HAVE BEEN RUNNING HIGHER 
DUE TO RAIN LAST WEEK. WILL CONTINUE TO MONITOR THIS POTENTIAL OVER 
THE NEXT FEW DAYS.

IN WAKE OF THE FRONTAL BOUNDARY FRIDAY MORNING...TEMPERATURES MAY 
SLOWLY FALL THROUGH THE DAY AS COLDER AIR SPREADS BACK INTO CENTRAL 
INDIANA. DRY SLOT ON BACK SIDE OF THE BOUNDARY MAY ACTUALLY ALLOW 
FOR A PERIOD WITH NO PRECIPITATION DURING THE DAY FRIDAY.  
PRECIPITATION WILL RETURN AS COLD POOL OVERSPREADS THE AREA DURING 
THE AFTERNOON...EITHER AS SNOW SHOWERS OR AS A SNOW/RAIN MIX BEFORE 
CHANGING TO SNOW. THEN AS THE LOW DRIFTS NORTHEAST ACROSS THE GREAT 
LAKES THROUGH THE WEEKEND...ANTICIPATE SCATTERED SNOW SHOWERS ACROSS 
CENTRAL INDIANA THROUGH SUNDAY. MODEL SOUNDINGS SHOWING PLENTY OF 
LOW LEVEL MOISTURE AND INCREASING COLD ADVECTION SATURDAY AND 
SUNDAY...ALONG WITH SHALLOW LOW LEVEL INSTABILITY. COULD SEE MINOR 
ACCUMULATIONS OVER THE WEEKEND...AND WILL ADDRESS IN GREATER DETAIL 
AS WE GET CLOSER. TEMPERATURES WARMING INTO THE 40S...POSSIBLY EVEN 
LOWER 50S ON THURSDAY IN THE WARM SECTOR WILL BEGIN SLIDING BACK ON 
FRIDAY...EVENTUALLY SETTLING IN THE MID AND UPPER 20S OVER THE 
WEEKEND. LOWS WILL FALL BACK INTO THE TEENS FOR SATURDAY/SUNDAY/ 
MONDAY MORNINGS. 

&&

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

&&

$$

UPDATE...CS
SHORT TERM...JAS
LONG TERM...RYAN
AVIATION...JH