FXUS63 KIND 251051
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
550 AM EST WED NOV 25 2009

.AVIATION...DISCUSSION FOR THE 25/12Z TAFS.
SURFACE LOW PRESSURE WAS LOCATED OVER LAKE MICHIGAN THIS MORNING... 
WITH AN UPPER LEVEL LOW OVER NORTHERN ILLINOIS. A LARGE AREA OF 
LIGHT RAIN HAD STEADILY INCREASED IN COVERAGE IN VICINITY OF THE 
UPPER LOW...AND WILL IMPACT KLAF AND POSSIBLY KHUF AND KIND THIS 
MORNING AS THIS FEATURE MOVES NORTHEAST. CEILINGS HAVE STAYED 
PRIMARILY AT MVFR LEVELS AT THE TERMINALS FOR THE LAST FEW HOURS... 
AND THIS WILL CONTINUE ALL MORNING AS LOW LEVELS REMAIN SATURATED. 
ANTICIPATE A PERIOD OF IFR CONDITIONS AT KLAF THROUGH 17Z AS AREA OF 
RAIN ASSOCIATED WITH THE UPPER LOW MOVES ACROSS NORTHERN INDIANA. 
PASSAGE OF A TROUGH AT THE SURFACE WILL ENHANCE SOUTHWEST WIND GUSTS 
TO AROUND 20KTS THIS MORNING AS WELL. WEAK RIDGING WILL BRING SOME 
DRIER AIR ALOFT ACROSS THE FORECAST AREA THIS AFTERNOON...BUT MODEL 
SOUNDINGS INDICATING THAT LOW LEVELS BELOW 5KFT REMAIN SATURATED.  
WHILE THE DRIER AIR SHOULD HELP CEILINGS TO RECOVER BACK INTO MVFR 
CATEGORY AT KLAF...EXPECT A PREDOMINANT 2K-2.5KFT STRATOCUMULUS DECK 
ALL AFTERNOON.

SECONDARY UPPER LOW WILL MOVE SOUTHEAST THIS EVENING AND BE LOCATED 
OVER CENTRAL INDIANA BY 12Z THURSDAY. MOISTURE WILL ONCE AGAIN 
INCREASE AHEAD OF THE UPPER LOW WITH LIGHT RAIN SHOWERS DEVELOPING 
OVER THE REGION THIS EVENING. HAVE INCLUDED A VCSH MENTION AT ALL 
TERMINALS FROM THIS POINT THROUGH THE REST OF THE FORECAST WITH 
IFR/LOW MVFR CEILINGS. AS DRIER AIR ALOFT SPREADS ACROSS FORECAST 
AREA OVERNIGHT...PRECIPITATION MAY END UP TAKING MORE OF THE FORM OF 
DRIZZLE WITH THE LOWEST 3-4KFT REMAINING SATURATED. THE BOUNDARY 
LAYER MAY BECOME SUFFICIENTLY COLD ENOUGH TOWARDS DAYBREAK THURSDAY 
FOR ANY LIGHT RAIN/DRIZZLE TO MIX WITH A FEW SNOWFLAKES. HAVE NOT 
INCLUDED THIS WITH THE 12Z FORECAST...BUT LATER SHIFTS TODAY WILL 
NEED TO ADDRESS PRECIPITATION TYPE AS THE COLDER AIRMASS BECOMES 
ESTABLISHED OVER THE REGION ON THURSDAY. SOUTHWEST WINDS WILL SLOWLY 
VEER TO WEST-SOUTHWEST OVERNIGHT AND HOLD AT 10-15KT.

&&

.DISCUSSION...COOLER AND UNSETTLED WEATHER EXPECTED ACROSS THE AREA 
IN THE SHORT TERM AS A COUPLE OF POTENT UPPER AIR DISTURBANCES MOVE 
THROUGH...EVENTUALLY CARVING OUT A LONG WAVE TROUGH OVER THE GREAT 
LAKES AND OHIO VALLEY BY THURSDAY. HOWEVER...PATTERN REMAINS 
PROGRESSIVE WITH THIS TROUGH MOVING TO THE EAST COAST BY FRIDAY. 
MODELS IN GOOD AGREEMENT WITH THE MAIN FEATURES. FORECAST FOCUS 
CENTERS ON POPS ASSOCIATED WITH THE DISTURBANCES AND PRECIPITATION 
TYPE TONIGHT AND THURSDAY.

FOR TODAY...FIRST SYSTEM CURRENTLY OVER NORTHERN ILLINOIS EXPECTED 
TO MOVE ACROSS THE NORTHERN SECTIONS OF THE STATE LATER THIS 
MORNING. REGIONAL RADARS SHOWING SOME LIGHT SHOWERS ASSOCIATED WITH 
THIS SYSTEM...WHICH LOOKS TO AFFECT MAINLY THE NORTHERN SECTIONS OF 
THE FORECAST AREA LATER THIS MORNING. PRECIPITATION THREAT WITH THIS 
SYSTEM SHOULD EXIT THE AREA BY THIS AFTERNOON...BUT LIFT FROM THE 
NEXT DISTURBANCE DROPPING SOUTHEAST THROUGH THE NORTHERN PLAINS 
SHOULD BE APPROACHING THE NORTHWEST COUNTIES TOWARDS SUNSET. ALL IN 
ALL...WL CONTINUE WITH CHANCE POPS TODAY...WITH THE HIGHEST POPS IN 
THE NORTHWEST.

IN THE LATER PERIODS...INITIAL BAND OF LIFT ASSOCIATED WITH SECOND 
SYSTEM EXPECTED TO MOVE ACROSS THE AREA DURING THE EVENING HOURS 
TONIGHT. SYSTEM LOOKS PRETTY DYNAMIC...SO WILL GO WITH LIKELY POPS 
IN THE NORTH CLOSEST TO THE BEST LIFT...AND CHANCE POPS FARTHER 
SOUTH. THICKNESSES SUGGEST AIR MASS MAY BECOME COLD ENOUGH TO 
SUPPORT SOME SNOW AFT ABOUT 260800Z...SO ANY LINGERING PRECIPITATION 
LATER IN THE NIGHT MAY HAVE SOME SNOW MIXED IN.

MAIN PART OF SECOND SYSTEM EXPECTED TO MOVE THROUGH ON THURSDAY. 
WILL GO WITH LIKELY POPS OVER ABOUT THE NORTHERN TWO THIRDS OF THE 
AREA...CLOSEST TO TRACK OF THE VORTICITY MAXIMUM...AND CHANCE POPS 
FARTHER SOUTH. THICKNESSES SUPPORT A RAIN/SNOW MIX. AT THIS 
POINT...DUE TO THE LIGHT AMOUNTS AND SURFACE TEMPERATURES ABOVE 
FREEZING...NOT EXPECTING ANY ACCUMULATIONS. WILL KEEP CHANCE POPS 
FOR RAIN OR SNOW DURING THURSDAY EVENING IN THE FAR EAST AND PERHAPS 
SOME FLURRIES ELSEWHERE...BUT IT APPEARS THREAT FOR MEASURABLE 
PRECIPITATION IS DIMINISHING BY THAT TIME.

LOW LEVEL THICKNESSES SUGGEST THE GFS MOS HIGHS FOR TODAY AND 
THURSDAY MAY BE A COUPLE OF DEGREES ON THE WARM SIDE...SO WILL NUDGE 
THEM DOWN A BIT IN THOSE PERIODS. REMAINDER OF GUIDANCE LOOKS OK.

&&

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

&&

$$

PUBLIC...JAS
AVIATION...RYAN