FXUS63 KIWX 252111
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
411 PM EST WED NOV 25 2009

.SHORT TERM...

TONIGHT THROUGH THU

SECONDARY UPPER LEVEL IMPULSE CONTINUES TO PUSH INTO THE GREAT LAKES 
REGION...SUPPORTING LARGE SCALE ASCENT INTO WI/IL. THIS FEATURE IS 
NEARLY COINCIDENT WITH THE FIRST OF TWO SFC TROUGHS WHICH ARE 
EXPECTED TO ADVECT INTO THE FA DURING THE PERIOD AND SUPPORT RAIN 
CHANCES...WITH A POSSIBLE SNOW MIX THUR. OCCLUDE SFC CYCLONE OVER 
THE NORTHERN GREAT LAKES IS EXPECTED TO GENERALLY PARK OVER NORTHERN 
MI FOR MUCH OF THE PERIOD AS THE SECONDARY IMPULSE DIGS PER AN 
ADVANCING UPPER JETLET AND SUPPORT LL PRESSURE FALLS ACROSS MUCH OF 
THE REGION. STAUNCH 110 KNOT UPPER LEVEL JET WILL SUPPORT A SLOWER 
EJECTION OF THE ENTIRE VORTEX AS HEIGHT FALLS WILL CONTINUE TO BE 
INDUCED ON THE SW EDGE OF THE UPPER WAVE. HENCE...HAVE FOLLOWED 
CLOSER TO THE NAM12 PROGS...WHICH SUPPORTS THE SLOWEST SYSTEM 
EVOLUTION AMONG DETERMINISTIC GUIDANCE.

TONIGHT...RAIN SHIELD ASSOCIATED WITH ASCENT AHEAD OF THE LL 
PRESSURE TROUGH IS EXPECTED TO PUSH INTO THE AREA. HAVE INCREASED 
POPS...OPTING FOR HIGHEST NUMBERS IN THE NW ZONES WHERE UVM AND LL 
CONVERGENCE WILL BE MAXIMIZED. DRY SLOT FEATURE ASSOCIATED WITH THE 
ADVANCING UPPER IMPULSE IS EXPECTED TO ADVECT OVER THE REGION LATE 
TONIGHT...STRIPPING AWAY DEEPER MID LEVEL MOISTURE. HAVE OPTED FOR A 
LOW POP MENTION AFTER MIDNIGHT FOR THIS WITH A DRIZZLE MENTION GIVEN 
LINGERING BL MOISTURE IN A REGIME FAVORING LL ASCENT. 

THUR...COLD CORE UPPER VORTEX WILL PUSH ACROSS THE FA THROUGH THE 
DAY AND OFFER SHOWER CHANCES PER INCREASED LL INSTABILITY IN 
CYCLONIC FLOW. HAVE RAISED POPS GIVEN UPSTREAM CONDITIONS AND 
EXPECTED SLIGHT DEEPENING OF THE UPPER LOW. PROFILES LOOK MARGINAL 
FOR SNOW GIVEN WARM BL AND LACK OF DEEP MOISTURE. HENCE HAVE ONLY 
OPTED FOR CH SNSH MENTION. OTHERWISE...LOOK FOR HIGHS IN THE UPPER 
30S TO AROUND 40. GIVEN THE INITIAL FLOW SPLIT...THE BULK OF CAA IS 
NOT EXPECTED TO PUSH INTO THE REGION UNTIL LATE THUR NIGHT AFTER 
MOST OF THE LL MOISTURE WILL BE SCOURED. HENCE...EXPECTING SNOW 
SHOWER CHANCES TO REMAIN VERY LOW. HOWEVER...A LAKE RESPONSE IS 
EXPECTED GIVEN DELTA T/S APPROACHING 16-18C. THIS SHOULD SUPPORT A 
PERIOD OF LAKE EFFECT SHOWERS...WITH A RAIN-SNOW MIX POSSIBLE...BUT 
VERY LOW UPSTREAM RH AND FLOW ORIENTATION LOOKS TO PRECLUDE 
FAVORABLE ORGANIZATION AT THIS TIME...WITH WAA AND HEIGHT RISES 
QUICKLY ESTABLISHING BY FRI AM. HAVE LEFT POPS LOW AT THIS POINT IN 
THE NW PER LAKE PROCESSES. CLOUD COVER IS ALSO EXPECTED TO BEGIN O 
SCT IN THE SW...WITH LAKE CLOUDS BEING ESTABLISHED OVER THE NE 2/3 
OF THE FA.

&&

.LONG TERM...
IMPRESSIVE SECONDARY SW DIGGING SEWD OUT OF MN THIS AFTN WILL LEAD 
TO A DREARY SHRT TERM HWVR BEGINNING OF THIS PD MARKED BY EXODUS OF 
THIS SYS AHD OF DEEP GULF OF AK SW DIGGING SWD INTO NRN MEXICO BY LT 
WEEKEND WHILE DOWNSTREAM RIDGING DVLPS W/MODERATING TEMPS THIS 
WEEKEND.

GREATEST DIFFICULTIES THIS PD LIE W/HANDLING OF COMPLEX SW ENERGY 
OVR THE ERN PACIFIC AS IT COMES INLAND THIS WEEKEND. 12Z MED RANGE 
SPREAD CONTS QUITE LARGE AND TIED TO AMT OF STREAM SEPARATION IN THE 
FLW EARLY NXT WEEK. 12Z OP GFS NOT THAT MUCH DIFFERENT COMPARED TO 
00Z EC/GEM SOLUTION MID NXT WEEK W/EJECTING DEEP SRN STREAM SW UP 
THROUGH THE OH VALLEY YET PREFERENCE LIES W/MORE WWD TRACK PLACEMENT 
GIVEN AN XPCD DEEPER THEN IMPLIED MEAN SOLUTION. THIS WEIGHTS 
HEAVILY W/PREFERRED CONTINUITY W/EXISTING SUN NIGHT/MON PD AND 
CONCURRENT POPS AND WILL HOLD CLOSE W/PRIOR FCST.

OTHERWISE BRIEF MODERATION IN TEMPS THIS WEEKEND WILL GIVE WAY TO 
PROGRESSIVELY COLDER READINGS NXT WEEK AS MODIFIED ARCTIC AIR SPILLS 
INTO THE PLAINS AND WORKS EWD.

&&

.AVIATION.../18Z TAFS/
UPPER LEVEL TROUGH AND ASSOCIATED SFC CYCLONE CONTINUES TO
SUPPORT MVFR CIGS WITH POCKETS OF HIGH END IFR VIS IN DZ THIS
AFTERNOON. SECONDARY UPPER LEVEL TROUGH WILL PUSH THROUGH THE
REGION TONIGHT WITH ANOTHER ROUND OF LIGHT RAIN EXPECTED AT THE
TERMINALS...POSSIBLY RESTRICTING VIS TO LOW END MFR. CIGS ARE
EXPECTED TO HANG ON TO LOW END MVFR THROUGH MUCH OF THE PERIOD.
HOWEVER...A SLIGHT IMPROVEMENT IN CONDITIONS IS ANTICIPATED THUR
AS CIGS MAY ELEVATE TO AROUND 2-3 KFT AS DRIER AIR ADVECTS INTO
THE AREA BEHIND ANOTHER COLD FRONT. SHOWERS WILL BECOME LIKELY
THUR AS THE UPPER VORTEX PASSES OVER THE FA...WITH A RAIN SNOW
MIX POSSIBLE. IF SNOW DOES MATERIALIZE VIS RESTRICTIONS WOULD BE
LIKELY WITH ANY SHOWER ACTIVITY.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY FROM 7 AM THURSDAY TO 4 PM EST FRIDAY FOR 
     LMZ043-046.

&&

$$

SHORT TERM...JC
LONG TERM...HOLSTEN
AVIATION...JC