000
FXUS63 KIWX 301900
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
300 PM EDT FRI JUL 30 2010

.SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT

MAIN CONCERN IN THIS PERIOD WILL BE PRECIP CHCS AS SHORTWAVE ENERGY
OVER THE UPPER MIDWEST TRACKS SEWD INTO THE GREAT LAKES TONIGHT INTO
SATURDAY IN ACTIVE NW FLOW ALOFT. FA REMAINS ON THE STABLE SIDE OF A
LOW LVL BAROCLINIC ZONE AS OF THIS WRITING...WITH THE BOUNDARY
DRAPED FROM THE TN VALLEY NWWD INTO MO AND NE. WEAK ISENTROPIC LIFT
AND RIGHT ENTRANCE REGION UPR JET DYNAMICS FROM A 110 KT JET ACROSS
THE EASTERN LAKES HAS ALLOWED A BKN MID/UPR LVL CLOUD DECK TO LINGER
ACROSS MAINLY WESTERN/SOUTHERN PORTIONS OF THE FA TODAY. MAY SEE A
FEW SPRINKLES IN THE WEST LATE THIS AFTN AND EARLY THIS EVE GIVEN
THE ABOVE MENTIONED FORCING...ALTHOUGH CIGS ARE STILL 10-15 KFT.
WILL SEE INCREASING CHANCES FOR SHOWERS AND MAYBE A RUMBLE OF
THUNDER TONIGHT INTO SATURDAY MORNING...BEST CHANCES IN THE NORTH
AND WEST LATE TONIGHT AND SATURDAY MORNING...AS MODELS INDICATE
DECENT CROSS ISOBARIC FLOW COUPLED WITH WEAK LARGE SCALE ASCENT
AHEAD OF THE ADVANCING UPPER IMPULSE. BETTER FLOW AND LIFT PER MODEL
Q-VECTOR CONV/OMEGA PROGS WILL REMAIN NORTH OF THE FA BY LATE
TONIGHT/SATURDAY MORNING. WITH THIS...KEPT POPS IN THE CHC CATEGORY
AS TYPICAL SPLIT MAY PREVAIL WITH BETTER FORCING NORTH AND DEEPER
MOISTURE SOUTH. HOWEVER...DID INCREASE POPS A LITTLE OVERNIGHT INTO
SAT MORNING IN THE NORTH AS CURRENT OBS/MOSAIC RADAR SHOWS AN AREA
OF RAIN ACROSS PORTIONS OF SRN WI AND NRN IL ATTM.

ANY MORNING SHRAS AND EMBEDDED THUNDER SHOULD CLEAR EASTERN AREAS OF
THE FA BY LATE SATURDAY MORNING AS BETTER ISENTROPIC ASCENT AND
FORCING SLIDES NE. CONTINUED WITH CHC POPS SAT AFTN AS LOW LVL
FORCING ALONG THE ASSOCIATED SFC TROUGH MAY ALLOW FOR ISO/SCT
CONVECTION TO DEVELOP GIVEN THE 92-8H THETA-E SURGE AND INCREASING
INSTABILITY IF THERE IS ANY CLEARING. INCREASING MID LVL FLOW ON SRN
FRINGE OF THE SHORTWAVE WILL ALLOW FOR MODERATE SHEAR. THE QUESTION
IS HOW FAR NORTH THE ABOVE MENTIONED SFC BOUNDARY WILL GET. IF THERE
IS ENOUGH OF A LOW LVL RESPONSE TO GENERATE A DECENT SFC-85H
CIRCULATION IN SRN MI...WHICH HAS BEEN HINTED AT BY THE NAM...WE
COULD GET THAT BOUNDARY FARTHER NORTH AND END UP WITH A SVR WX
THREAT IN THE WESTERN FA SAT AFTN GIVEN THE PROGGED MODERATE SHEAR
AND POSSIBLE MLCAPE OF 1500-2500 J/KG ADVERTISED BY THE NAM. AT THIS
POINT FAVOR THE WEAKER/MORE STABLE SOLUTION WITH THE BETTER CHANCES
OF SVR CONVECTION AND ANY CONVECTION AT ALL BEING SOUTHWEST OF THE
FA. INHERITED 30 POPS COVER THIS WELL. OTHERWISE...EXPECT SEASONABLE
TEMPS AND PARTLY TO MOSTLY CLOUDY SKIES THROUGH THE PERIOD.


&&

.LONG TERM.../SUNDAY THROUGH THURSDAY/...

EXTENDED PERIOD STILL HIGHLIGHTED BY A SYSTEM EARLY NEXT WEEK MOVING
ATOP CONTINUED RIDGING ALONG THE SOUTHERN STATES FORCING STRONG
WESTERLIES TO REMAIN NORTH TO THE US-CAN BORDER.  AFTER A SLOW
WARMUP SUN-MON TAKES HIGHS INTO THE UPPER 80S SHRTWV MOVES INTO
THE REGION WITH FRONTAL BOUNDARY SAGGING SOUTH INTO THE AREA BY
TUESDAY NIGHT.  AS WITH LAST WEEK BEST MID/UPR LEVEL SUPPORT REMAINS
NORTH BUT ECMWF HAS UPPED THE ANTE WITH WARM MOIST RETURN AHEAD OF
THE FRONT..PERHAPS TOO MUCH SO..BUT IS MORE IN LINE WITH THE WARMER
MEX GUIDANCE THAT HAS BEEN ADVERTISED LATELY.  HENCE...A BUMP IN
TEMPS ON TUESDAY IS IN ORDER ALONG WITH CONTINUED CHANCES FOR
CONVECTION AS BNDRY SAGS INTO MOIST UNSTABLE AIRMASS.

FRONT MAKES VERY SLOW PROGRESS AND IF MODEL TIMING REMAINS
CONSISTENT POPS MAY BE NEEDED WEDNESDAY ESP ACROSS THE SOUTH.
GIVEN LEAD TIME WILL HOLD ONE MORE CYCLE TO BE SURE MORE PROGRESSIVE
SOLN DOES NOT UNVEIL ITSELF.  THEREAFTER DEGREE OF FLATTENING AND
REFOCUS OF RIDGING TO THE WEST PER 12Z GFS IS UNDETERMINED WITH WIDE
MODEL/ENSEMBLE SPREAD BUT A MILD CONSENSUS ON SOMEWHAT FLATTER/ZONAL
FLOW ACROSS THE NORTHERN HALF OF CONUS IMPLIES TEMPS JUST ABOVE
CLIMO BY END OF PD.

&&

.AVIATION...18Z TAFS
VFR CONDITIONS ARE EXPECTED THIS AFTN INTO MOST OF TONIGHT AS MID
LVL CLOUD DECK WILL GRADUALLY LOWER WITH TIME GIVEN INCREASING
ISENTROPIC ASCENT/MID LVL FORCING AHEAD OF AN APPROACHING MID LVL
IMPULSE OVER THE UPPER MIDWEST. MAY SEE A FEW LIGHT
SHOWERS/SPRINKLES WORK INTO SBN LATE THIS AFTN OR THIS EVENING PER
UPSTREAM OBS/RADAR AND INCREASING LIFT. CONTINUED WITH THE TEMPO
SHRA GROUP AROUND DAYBREAK SATURDAY AT FWA/SBN AS SFC TROUGH AND
THE ASSOCIATED 92-8H THETA-E SURGE ADVECTS IN. DID HOLD ONTO VFR
CIGS/VIS LATE TONIGHT INTO SATURDAY MORNING...BUT COULD SEE A
PERIOD OF MVFR CONDITIONS IF THE SHOWER ACTIVITY ENDS UP MORE
ORGANIZED.

&&

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

$$

SHORT TERM...STEINWEDEL
LONG TERM...LUD
AVIATION...STEINWEDEL

NWS IWX Office Area Forecast Discussion