FXUS63 KIWX 112037
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
337 PM EST FRI DEC 11 2009

.SHORT TERM...
TONIGHT THROUGH SATURDAY NIGHT...
HIGH PRESSURE CENTERED OVER THE TENNESSEE VALLEY WILL GIVE A QUIET 
START AND WARMING TREND IN THE SHORT TERM. SFC RIDGE TO SLIDE TOWARD 
THE EAST COAST ON SATURDAY PLACING THE REGION IN GOOD WAA PATTERN. 
EXPECT GOOD NIGHT FOR RADIATIONAL COOLING WHICH SHOULD SEE TEMPS 
DROP A GOOD 5-10F BELOW NORMAL ACROSS THE AREA. GOOD RECOVERY IN 
DAYTIME TEMPS ALREADY BEING OBSERVED THIS AFTERNOON AND EXPECT A 
CONTINUATION TOMORROW DESPITE INCREASING CLOUDS IN THE 
AFTERNOON...SHOULD SEE TEMPS AOA NORMAL AT MOST LOCATIONS. FOCUS 
THEN SHIFTS TO WEAK DISTURBANCE APPROACHING THE AREA SATURDAY NIGHT 
WITH PRECIP TYPE AS MAIN CHALLENGE. DECENT ISENTROPIC UPGLIDE 
INDICATED ON 295K SFC WITH COND PRES DEFICITS DROPPING BELOW 10MB BY 
06Z OVER THE CWA...BUT WITH NOT OVERWHELMING MOISTURE OR FORCING 
WILL OPT TO BUMP POPS JUST TO HIGH CHANCE ATTM. WITH WAA WELL 
UNDERWAY NOT ANTICIPATING MUCH OF A DIURNAL DROP OFF SAT EVENING 
BEFORE TEMPS BECOME STEADY AND SLOWLY RISE TOWARD MORNING. FCST 
SOUNDINGS SHOWING GOOD WARM LAYER PUNCHING THROUGH MUCH OF THE AREA 
AFTER 06Z. LACK OF FORCING WOULD SUGGEST NOT MUCH IN THE WAY OF 
DYNAMIC COOLING WITH ONSET OF PRECIP SO EXPECT SFC TEMPS TO BE ABOVE 
FREEZING IN EXTREME SOUTHERN CWA AND WILL KEEP PRECIP ALL RAIN HERE. 
ELSEWHERE WILL KEEP A MIX IN WEATHER GRIDS WITH R/FZRA IN CENTRAL 
AND R/IP/FZRA COMBO IN THE NORTH.&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...

MAIN EFFECTS OF THE SAT NGT SHORT WAVE WILL BE EXITING DURING THE 
DAY SUNDAY. HAVE ALSO REMOVED ANY MENTION OF SNOW AND WENT WITH WARM 
AIR ADVANCING NORTH IN THE AM TO CHANGE THINGS OVER TO ALL 
RAIN...WHAT LITTLE WILL BE LEFT...SOUTH OF US 30. BY AFTERNOON MOST 
OF THE FORCING WILL BE GONE BUT HAVE KEPT LINGERING RAIN/FZRA 
MENTION FOR NOW. MODELS VARY SOMEWHAT ON EXACT AMOUNT OF WARMING AT 
THE SFC BUT WITH HIGHS LIKELY TO BE IN THE MID 30S TO NEAR 40...MAY 
BE ABLE TO REMOVE ANY FZRA MENTION IN NEXT PACKAGE.

FOCUS THEN TURNS TOWARDS THE NEXT SYSTEM SET TO MOVE IN BY MONDAY. 
MODELS CONTINUE TO POINT TOWARDS A NICE SHOT OF WARM AIR WITH THIS 
AS WELL WITH HIGHS POTENTIALLY IN THE 40S IN MANY SPOTS ON MONDAY. 
ISSUES REMAIN WITH THE EXACT TIMING OF THE FRONT AND THE AMOUNT OF 
COLD AIR WITH IT. WHILE THE PRECIP MAY BE ENTIRELY RAIN...HAVE OPTED 
TO KEEP THE MIX AS ECMWF STILL HOLDS ONTO COLDER AIR BEGINNING TO 
ARRIVE BY AFTERNOON. THE GFS...WHICH HAS BEEN FAIRLY PERSISTENT ON 
THE ARRIVAL OF ANOTHER ARCTIC BLAST HAS BEGAN TO WAVER SOMEWHAT. MEX 
GUIDANCE FROM 12Z HAS INCREASED BY 5 TO 10 DEGREES IN MANY AREAS FOR 
TUESDAY WITH HIGHS GENERALLY IN THE 20S. WHILE THIS WOULD SEEM TO BE 
A RATHER DRAMATIC CHANGE...DPROG/DT FOR 850 MB TEMPS AT 00Z WED SHOW 
A SLOW BUT PERSISTENT TREND IS PUSHING THE COLDEST AIR TO THE NE OF 
THE FORECAST AREA. THIS SCENARIO CAN'T BE RULED OUT BUT STILL HAVING 
A HARD TIME BELIEVING THAT THE COLD AIR WON'T SETTLE IN MUCH LIKE WE 
ARE LEAVE NOW. HAVE LEFT HIGHS ALONE FOR TUES AND WEDS...WITH HIGHS 
ALREADY BELOW GUIDANCE...A GOOD COMPROMISE AT THIS TIME. HAVE ALSO 
LEFT ANYTHING WITH LAKE EFFECT ALONE. EVEN IF SETUP DOES 
MATERIALIZE...WITH FAVORABLE DELTA T'S...INVERSION HGTS WILL BE 
LOWER THAN PAST EVENT AS WILL MSTR SO POTENTIAL MAY BE REDUCED 
SOMEWHAT. 

&&

.AVIATION...
18Z TAFS...VFR CONDITIONS TO PREVAIL AT BOTH TAF SITES THIS PERIOD. 
W/SW WINDS 10-15KTS WILL BACK TO MORE SOUTHERLY FLOW AND DIMINISH TO 
LT 10KTS THIS EVENING. 

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR LMZ043-046.

&&

$$

SHORT TERM...LOGSDON
LONG TERM...FISHER
AVIATION...LOGSDON