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000
FXUS63 KIWX 140743
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
343 AM EDT FRI JUN 14 2013

.SYNOPSIS...
ISSUED AT 341 AM EDT FRI JUN 14 2013

HIGH PRESSURE WILL MAINTAIN COOL AND DRY CONDITIONS OVER THE REGION
THROUGH TONIGHT. THE CHANCE OF SHOWERS AND THUNDERSTORMS WILL THEN
RETURN OVER THE WEEKEND AS ANOTHER UPPER LEVEL TROUGH PASSES OVER
THE REGION.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 341 AM EDT FRI JUN 14 2013

INCREDIBLY BENIGN WEATHER IN STORE FOR THE LOCAL FORECAST AREA
TODAY. STRONG AVA ASSOCIATED WITH THE GRADUAL APPROACH OF CENTRAL
CONUS LONGWAVE RIDGE WILL SUPPORT WIDESPREAD SUBSIDENCE AND A 1020MB
SURFACE HIGH OVER THE GREAT LAKES. MAIN QUESTION WILL BE CLOUD
TRENDS. NAM AND GFS FORECAST SOUNDINGS/RH FIELDS CONTINUE TO SHOW A
ROBUST AFTERNOON CU FIELD DEVELOPING TODAY THANKS TO RESIDUAL
BOUNDARY LAYER MOISTURE. SURFACE DEWPOINTS WILL CONTINUE TO HOVER IN
THE MID 50S AND STOUT SUBSIDENCE INVERSION SHOULD HELP TRAP THIS
MOISTURE AND MAINTAIN A DECENT DIURNAL CU FIELD. ADJUSTED SKY GRIDS
UPWARD A BIT FOR THE AFTERNOON BUT STAYED GENERALLY IN PARTLY CLOUDY
RANGE FOR NOW. THIS WILL ALSO HELP KEEP A LID ON AFTERNOON TEMPS.
850MB TEMPS WILL BE AROUND 11C ONCE AGAIN AND THIS SHOULD RESULT IN
HIGHS VERY SIMILAR TO YESTERDAY...IN THE MID TO UPPER 70S.

LOW LEVEL RIDGE AXIS WILL SHIFT OVERHEAD TONIGHT WITH SOME
INCREASING WAA ALOFT. NO PRECIP EXPECTED BUT THIS WILL BRING AN
INCREASE IN MID/UPPER LEVEL CLOUDS TOWARD DAYBREAK
SATURDAY...HELPING TO SUPPRESS LONGWAVE RADIATIVE LOSSES DESPITE
NEARLY CALM SURFACE WINDS. TIMING THESE CLOUDS WILL BE IMPORTANT TO
WATCH THOUGH AS LATE ARRIVAL COULD ALLOW TEMPS TO DROP MORE THAN
EXPECTED. FEW CHANGES MADE TO INHERITED FORECAST WITH SLIGHT NOD TO
COOLER GUIDANCE AND VALUES GENERALLY IN THE MID TO UPPER 50S.

&&

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 341 AM EDT FRI JUN 14 2013

AN ACTIVE PERIOD STILL APPEARS TO BE IN STORE FOR THE WEEKEND INTO
THE EARLY PORTIONS OF NEXT WEEK...BEFORE MAINLY DRY CONDITIONS
BECOME ESTABLISHED BY TUESDAY.

A LARGE SCALE UPPER TROUGH ACROSS THE PACIFIC NORTHWEST WILL
CONTINUE TO DEEPEN WITH ACTIVE POLAR/SUBTROPICAL JET PATTERN ACROSS
WESTERN CONUS. THIS WILL EVENTUALLY ALLOW A WEAK CUT OFF UPPER LOW
ACROSS TEXAS TO GET INGESTED INTO BELT OF STRONGER UPPER LEVEL
SOUTHWESTERLIES ON SATURDAY. MODEL DEPICTIONS OF THIS ARE VASTLY
DIFFERENT GIVEN CONVECTIVE CONTRIBUTION TO STRENGTH OF UPPER VORT
MAXES...BUT SOME INCREASE IN MID/UPPER LEVEL FORCING IS EXPECTED
WITH THIS PATTERN BY SATURDAY AFTERNOON/NIGHT. MOREOVER...DEPARTING
LOW LEVEL RIDGING WILL ALLOW A STRONGER LOW LEVEL WESTERLY FLOW TO
SETUP ACROSS THE SOUTHERN GREAT LAKES REGION DURING THIS PERIOD
RESULTING IN STRONG LOW LEVEL THETAE ADVECTION GIVEN PREEXISTING
STRONG WEST TO EAST MOISTURE GRADIENT IN PLACE. NO CHANGE MADE TO
PREVIOUS FORECAST IN CHANCE POPS MAINLY WESTERN CWA SATURDAY
AFTERNOON WITH LIKELYS ACROSS ENTIRE AREA SATURDAY NIGHT COINCIDENT
WITH STRONGEST LOW LEVEL MOISTURE CONVERGENCE ACCOMPANYING THETAE
ADV. LINGERING UNCERTAINTY IN REGARDS TO POPS IS WITH STRENGTH OF
MID/UPPER LEVEL SHORT WAVES WHICH IS DIFFICULT TO RESOLVE AT THIS
FORECAST DISTANCE. IN TERMS OF SEVERE POTENTIAL...GREATER DIURNAL
INSTABILITY SATURDAY AFTERNOON WILL REMAIN WEST OF THE AREA WITH
MAIN POCKET OF HIGHER MUCAPES SHIFTING INTO THE AREA AFTER DARK.
SHEAR PARAMETERS ALSO SOMEWHAT ON THE MARGINAL SIDE AND AT THIS TIME
ANY HAIL/WIND POTENTIAL APPEARS TO BE MARGINAL. MAY NEED TO WATCH
THIS PERIOD FOR HYDRO CONCERNS GIVEN STRONG LOW LEVEL MOISTURE
CONVERGENCE AND PWATS INCREASING UP OVER 1.6 INCHES ALONG WITH WET
ANTECEDENT CONDITIONS.

SUSPECT SOME NOCTURNAL SHOWER/THUNDERSTORM ACTIVITY MAY BE
ONGOING/DEPARTING EARLY SUNDAY MORNING POSING QUESTIONS AS TO EXTENT
OF AFTERNOON DESTABILIZATION. NOT MUCH AT THIS POINT TO LATCH ONTO
IN TERMS OF PRONOUNCED MID/UPPER FORCING SO HAD TO MAINTAIN
BROADBRUSH CHANCE TSRA POPS THROUGH SUNDAY NIGHT BUT AGAIN...SEVERE
POTENTIAL APPEARS TO BE LOW AT THIS TIME. MODELS BEGIN TO DIVERGE BY
MONDAY WITH EC/GEM CLUSTERED INTO A MORE PROGRESSIVE IDEA WITH THE
SOUTHERN CANADIAN UPPER TROUGH AS IT DROPS INTO THE WESTERN GREAT
LAKES. GFS RUN TO RUN CONSISTENCY HAS BEEN A BIT POOR FOR THIS
PERIOD AND UPON COLLABORATION WITH SURROUNDING OFFICES HAVE LEANED
MORE TOWARD PROGRESSIVE EC/GEM IDEA. MAIN IMPACT OF THIS PROGRESSIVE
PREFERENCE TO THE FORECAST WAS TO REDUCE POPS FOR MONDAY NIGHT. WITH
RELATIVELY COOLISH TEMPS ALOFT AND INDICATIONS OF A WEAKER LOW
AMPLITUDE WAVE APPROACHING IN NORTHWEST FLOW TUESDAY...DID MAINTAIN
ISOLD POPS INTO TUESDAY AFTERNOON ACROSS THE EAST. NO MAJOR CHANGES
TO TEMPS THROUGH THIS FORECAST PERIOD WITH TRANSITION TO A DRIER LOW
LEVEL AIR MASS TUESDAY-THURSDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT) ISSUED
AT 128 AM EDT FRI JUN 14 2013

LARGELY VFR CONDITIONS EXPECTED THIS TAF PERIOD AS STRONG CENTRAL
CONUS RIDGE FORCES HIGH PRESSURE AND SUBSIDENCE TO BUILD OVER THE
GREAT LAKES. RESIDUAL MOISTURE FROM RECENT RAINFALL MAY SUPPORT
SOME SHALLOW FOG LATER THIS MORNING BUT MARGINAL DEWPOINTS COUPLED
WITH STEADY...ALBEIT LIGHT...SURFACE WINDS SHOULD KEEP ANY FOG
PATCHY AND SHALLOW WITH LIMITED IMPACTS. THIS RESIDUAL MOISTURE
WILL ALSO SUPPORT A HEALTHY DIURNAL CU FIELD TODAY BUT GOOD MIXING
DEPTHS SHOULD KEEP CEILINGS IN VFR CATEGORY.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...BEACH HAZARDS STATEMENT UNTIL 10 AM CDT THIS MORNING FOR INZ003.

MI...BEACH HAZARDS STATEMENT UNTIL 11 AM EDT THIS MORNING FOR MIZ077.

OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 11 AM EDT THIS MORNING FOR LMZ043-046.

&&

$$

SYNOPSIS...AGD
SHORT TERM...AGD
LONG TERM...MARSILI
AVIATION...AGD


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