FXUS63 KIWX 112300
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
559 PM EST THU MAR 11 2010

.UPDATE/AVIATION...
LG SCALE DRY SLOT ADVTG OUT OF THE MID MS VALLEY PROMOTING BKN LINE
OF SHALLOW CONVN ALG THE IL/IN BORDER IN TANDEM W/LEADING EDGE OF
COLD POCKET ALOFT AND STG SFC MSTR CONVERGENCE COLLOCATED W/UPSTREAM
SFC INSTABILITY WEDGE THROUGH ERN IL. DEEP CLOSED MID LVL CIRC OVR
NW IA WILL HOOK BACK WWD INTO ERN NE OVERNIGHT AND IN ESSENCE KEEPS
ERN EDGE OF -20C H5 COLD POCKET CONFINED TO FAR WRN CWA. THUS PER
TRENDS THROUGH THIS AFTN...HAVE DROPPED THUNDER MENTION CNTRL/EAST
FOR THIS EVENING.

OTHERWISE SFC TROUGH AXIS WILL CONT NEWD THIS EVENING W/MORE
SUBSTANTIAL LL VEERING BEHIND MID LVL TROUGH AXIS AND W/INCOMING DRY
AIR ALOFT...LOOKS LIKE AN IDEAL SETUP FOR FOG AND POTENTIALLY
DRIZZLE PENDING DEPTH OF BNDRY LYR MSTR THAT GETS TRAPPED. 18Z/21Z
RUC LOOK A BIT TOO SHALLOW W/BNDRY LYR SATURATION LATE TONIGHT TO
WARRANT DZ MENTION YET BUT WILL REACCESS W/00Z RAOB ANALYSIS LTR
THIS EVENING FOR PSBL ADDNL ZONE AMENDMENT. REGARDLESS GIVEN
UPSTREAM CLRG AND WK CAA FOG LOOKS LIKELY LATE.

VFR CONDS EARLY THIS EVE XPC TO DETERIORATE THROUGH LT EVENING ESP
AS MID LVL DRY SLOT PUSHES THROUGH THE AREA BTWN 03-06Z. ONGOING -RA
SHLD SEED SIG FOG LATE INTO FRI AM ESP W/SECONDARY LL BACKING AHD OF
SECONDARY UPSTREAM SW AMPLIFYING ACRS SRN OK/N TX THIS EVENING. IN
ADDN...GUIDANCE IMPLIED WK ASCENT DVLPG TWD MORNING INADV OF
SECONDARY SW MAY PROVIDE ENOUGH IMPETUS FOR DZ TO DVLP WHICH FURTHER
WARRANTS A SIG FOG MENTION.

&&

.SHORT TERM...THIS AFTERNOON THROUGH FRIDAY NIGHT...

LARGE CLOSED UPR LOW WILL CONTINUE TO MEANDER EAST ACROSS THE
CENTRAL PART OF THE CONUS WHILE STG PACIFIC ENERGY PUSHES EAST
ACROSS TX/OLD MEXICO BORDER THIS AFTERNOON. AFTER PROMOTING
CYCLOGENESIS...A PORTION OF THIS ENERGY WILL BECOME ABSORBED INTO
UPR LOW AND SFC LOW WILL FOLLOW...ROTATING INTO INDIANA FRIDAY NIGHT.

THIS AFTERNOON AND TONIGHT...
AS EJECTING UPR WAVE MOVES UP THE OHIO VALLEY LATE THIS AFTERNOON
EXPECT REDVLPMNT OF SHOWERS/TSTORMS OVR ERN IL/WRN IN AS BNDRY
LAYER CONTINUES TO DESTABILIZE AS EVIDENCED BY CU STREETS.
SUBSIDENCE BEHIND FIRST WAVE MOVING OVERHEAD EARLY THIS AFTERNOON
MAY HAMPER SHRA/TSRA DEVELOPMENT INITIALLY. HOWEVER...NEXT VORT LOBE
SHOULD BECOME COLLOCATED WITH EWD MOVING SFC OCCLUDED FRONT LATER
THIS AFTERNOON OVER ERN IL/WRN IN WITH SCT SHRA/TSRA FIRING ALONG
AND EAST OF THIS BNDRY. THIS ACTIVITY SHOULD THEN SPREAD ENE INTO
THE CWA VERY LATE THIS AFTERNOON AND THIS EVENING AND HAVE UPPED
POPS TO CATEGORICAL IN SW CWA IN 00-06Z TIMEFRAME TO KEEP WITH
SLOWER TIMING OF SECONDARY H5 WAVE.

FRIDAY THROUGH FRIDAY NIGHT...
MODELS IN GOOD AGREEMENT WITH SFC LOW DVLPMNT OVR GULF COAST AS HIGH
PLAINS SHRTWV MOVES EAST THROUGH LOUISIANA TONIGHT. STRENGTHENING
SFC LOW WILL THEN TAKE A UNIQUE TRACK FROM MS TO KY TO WRN INDIANA
TO MO BEFORE STACKING UP AND FILLING BENEATH PERPETUAL UPR LOW IN
THE MO BOOTHEEL REGION ON SAT. WHAT THIS MEANS FOR US IS LIKELY A
DRY START TO THE DAY FRIDAY WITH AN INCREASED PROBABILITY FOR RAIN
SHOWERS AS THE DAY GOES ON. GRIDS WERE ADJUSTED TO LIKELY FRI NIGHT
TO ACCOUNT FOR INCREASING CHCS NE OF WWD MOVING SFC LOW.

TEMPSWISE...BUMPED UP LOWS TONIGHT IN THE EAST AS CLOUD COVER SHOULD
ALLOW LOWS TO STAY AOA GUIDANCE AS HAS BEEN THE CASE LATELY. THE
EXCEPTION TO THIS IS IN SWRN CWA WHERE SOME CLEARING BEHIND OCCLUDED
FRONT MAY RESULT IN TEMPS AOB GUIDANCE VALUES. INCREASED HIGHS SOME
TOMORROW AS TEMPS CONTINUE TO OUTPERFORM GUIDANCE TODAY EVEN IN
SPITE OF CLOUD COVER.

&&

.LONG TERM...

SATURDAY THROUGH THURSDAY

GENERALLY BLOCKED FLOW WILL DOMINATE THE CONUS AS A NEAR REX BLOCK
PATTERN CONTINUES THROUGH EARLY NEXT WEEK...GIVEN CUT OFF UPPER LOW
OVER THE EASTERN US UNDER A BUILDING UPPER RIDGE ACROSS SOUTHERN
CANADA. SPLIT UPPER FLOW WILL CONTINUE TO OFFER DRY CONDITIONS
BEYOND THE WEEKEND...WITH SFC RIDGING OFFERING RELATIVELY MILD
CONDITIONS BY MID NEXT WEEK. THERE IS SOME UNCERTAINTY PER THE
DETAILS OF AN EJECTING SW CONUS UPPER LOW EARLY NEXT WEEK...BUT
GIVEN THE LOCATION OF THE SUBTROPICAL JET...PATTERN RECOGNITION
WOULD FAVOR A SOUTH BIAS TO THIS SYSTEM. FORECAST MODELS AND MEAN
ENSEMBLES ARE IN GOOD AGREEMENT THROUGH THE PERIOD...WITH A BLEND OF
THE GFS AND ECMWF PREFERRED.

SAT-SUN...WANDERING UPPER LOW WITH ROTATING FUJIWARA TYPE
DISTURBANCES WILL SUPPORT PRECIP CHANCES AND CLOUDS INTO THE
REGION...WITH WEAK UPGLIDE CONTINUING THROUGH SAT MORNING. COOLER
AIR WILL WRAP INTO THE SYSTEM ON SAT AND SUPPORT COOLER THERMAL
FIELDS...WITH HIGHS IN THE 50S EXPECTED. DID RAISE TEMPS A DEGREE OR
TWO IN LINE WITH MIXING FIELDS AND ALSO IN SUPPORT OF GUIDANCE.
UPPER TROUGHING WILL BEGIN TO SHIFT EAST SUNDAY WITH DRY AIR
BEGINNING TO WORK INTO THE FA BY LATE SUNDAY. DID TRIM POP MENTION
SUNDAY EVENING...REFLECTING THE INTRODUCTION OF DRIER AIR INTO THE
REGION AND THE LOSS OF LARGE SCALE FORCING.

MON-THUR...WEAK SFC RIDGING CAN BE EXPECTED THROUGH THE PERIOD WITH
NW FLOW DOMINATING THE WEATHER...OFFERING PARTLY TO MOSTLY SUNNY
SKIES AND DRY CONDITIONS. MILD THERMAL FIELDS ARE EXPECTED PER
HIGHS...WITH VALUES AT OR ABOVE NORMAL. ALTHOUGH...LOWS WILL BE VERY
MUCH NEAR NORMAL GIVEN DRIER LL FIELDS. HAVE ADJUSTED GRIDS TO
REFLECT A SLOW WARMING TREND THROUGH THE PERIOD...KEEPING TEMPS
COOLER NEAR LK MI GIVEN EXPECTED LAKE BREEZE DIURNAL CIRCULATION.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

SHORT TERM...SIMPSON
LONG TERM...JC
UPDATE/AVIATION...T





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