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000
FXUS63 KIWX 140008
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
808 PM EDT THU JUN 13 2013

.SYNOPSIS...
ISSUED AT 210 PM EDT THU JUN 13 2013

A RIDGE OF HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE REGION
INTO FRIDAY...ACCOMPANIED BY COOLER AND DRIER WEATHER. MORE
SHOWERS AND THUNDERSTORMS ARE POSSIBLE THIS WEEKEND AS AN UPPER
LEVEL TROF APPROACHES.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 350 PM EDT THU JUN 13 2013

COOLER AND DRIER AIR WILL SPREAD SOUTH OVER THE FORECAST AREA
TONIGHT. PARTLY TO MOSTLY CLOUDY SKIES SHOULD BECOME CLEAR TO MOSTLY
CLEAR TONIGHT AS SUBSIDENCE INCREASES OVER THE AREA. KEPT THE
FORECAST DRY EARLY TONIGHT. SCATTERED SHOWERS THAT WERE MOVING SOUTH
TOWARD SE LOWER MICHIGAN SHOULD DISSIPATE WITH THE LOSS OF DAYTIME
HEATING. OTHERWISE SOME CONCERN FOR SKIES TO BECOME MOSTLY CLOUDY
FRIDAY GIVEN MOISTURE TRAPPED UNDER A WEAK SUBSIDENCE INVERSION. FOR
NOW...WENT WITH THE MORE OPTIMISTIC GFS OVER THE NAM...KEEPING SKIES
PARTLY CLOUDY WITH HIGHS IN THE MID TO UPPER 70S. NAM/MET GFS/MAV
TEMPERATURE GUIDANCE APPEARS ON TRACK.

&&

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 350 PM EDT THU JUN 13 2013

MAIN FOCUS OF LONG TERM FORECAST IS AN UNSETTLED WEATHER PATTERN
FROM SATURDAY AFTERNOON THROUGH THE LATE MONDAY/EARLY TUESDAY
TIMEFRAME.

HIGH PRESSURE WILL CONTINUE TO SLIDE SOUTHEAST THROUGH THE AREA
FRIDAY EVENING INTO EARLY SATURDAY. AS SFC HIGH CENTER TRAVELS
ACROSS EASTERN AREAS THROUGH THE EARLY OVERNIGHT PERIOD...LOOKS LIKE
LOW LVL WAA WILL BEGIN AFTER THE 06Z TIMEFRAME...ESPECIALLY
SOUTHWEST AREAS. FEEL THAT THE WAA WILL SOMEWHAT OVERPOWER
RADIATIONAL COOLING EFFECTS ESPECIALLY SOUTHWEST...WHICH WILL RESULT
IN SUBSTANTIAL LOW TEMP GRADIENT FROM SW TO NE. AS A RESULT...RAISED
LOWS A DEGREE OR TWO ACROSS THE ENTIRE AREA...BUT STILL SLIGHTLY
COOLER THAN CLIMATOLOGICAL NORMS.

CENTRAL CONUS UPPER RIDGE AXIS WILL BEGIN TO PROPAGATE EASTWARD
TOWARD THE REGION. 925-850MB THETA E BOUNDARY WILL PUSH NORTHEAST
FROM THE MID MISSISSIPPI VALLEY INTO SW AREAS DURING THE DAY ON
SATURDAY. SERIES OF WEAK DISTURBANCES WILL PROPAGATE ALONG THE
MOISTURE GRADIENT...BRINGING CONVECTION CHANCES TO OUR AREA. TIMING
OF POPS IS VERY TRICKY GIVEN THE WEAKLY FORCED DISTURBANCES. MAIN
THINKING IS THAT A WEAKER DISTURBANCE WILL BRING LIMITED POPS TO
AREAS ACROSS THE WEST AND JUST SW OF THE AREA NEAR THE 12Z TIME
FRAME. DECIDED TO ADD CHANCE POPS TO FAR WEST AREAS BEFORE 18Z GIVEN
THIS UNCERTAINTY AND FOR COLLABORATIVE PURPOSES.

ANOTHER DISTURBANCE IS EXPECTED TO TRACK EAST ACROSS SOUTHERN/SW
AREAS TOWARD 18Z AND AFTER. BACKED OFF POPS ACROSS EASTERN/NE AREAS
WITH MAIN FORCING EXPECTED SOUTH. HIGHLY QUESTIONABLE IF FORCING
WILL BE ADEQUATE FOR CONVECTIVE DEVELOPMENT. HOWEVER GIVEN
SIGNALS...DECIDED TO GO WITH CHANCE POPS ACROSS SW/SOUTHERN AREAS
FROM 18Z TO 00Z.

MORE ROBUST SHORTWAVE EXPECTED ADVECT THROUGH THE REGION AFTER 00Z.
HAVE WENT WITH LIKELY ACROSS THE ENTIRE AREA FROM 00Z-12Z. AS WITH
PREVIOUS DISCUSSION...SOME QUESTIONS AS TO SEVERE POTENTIAL. MODEST
MID LEVEL LAPSE RATES AND INSTABILITY...UP TO 1000 J/KG
MUCAPE...WILL BE PRESENT ACROSS MAINLY WESTERN AREAS FROM 00Z AFTER.
30-40 KT 0-6 BULK SHEAR VALUES POSSIBLE AHEAD OF THE WAVE...HOWEVER
INSTABILITY REMAINS SHUNTED TO FAR WESTERN AREAS AND POINTS WEST.
DIURNAL TIMING STILL REMAINS A QUESTIONS AS WELL...THEREFORE ONLY A
MARGINAL RISK FOR HAIL/ISOLATED WINDS AT THIS POINT GIVEN THESE
UNCERTAINTIES...HOWEVER WILL CONTINUE TO MONITOR.

ZONAL FLOW PATTERN SETS UP BRIEFLY FOR SUNDAY/SUNDAY NIGHT. MODESTLY
UNSTABLE CONDITIONS...WEAK DISTURBANCES ALONG ZONAL MOISTURE/THERMAL
BOUNDARY WILL KEEP PRECIP CHANCES ACROSS THE AREA THROUGH THIS
PERIOD. CURRENTLY THINK BEST CHANCES WILL REMAIN ACROSS SOUTHERN
AREAS...AND HAVE REFLECTED THIS IN THE GRIDS.

NORTHERN STREAM SHORTWAVE WILL TRACK SOUTHEAST INTO GREAT LAKES
REGION DURING THE MONDAY TIMEFRAME. MODEL DIFFERENCES BRING LOW
CONFIDENCE FOR TIMING/EXTENT OF POPS FROM THIS PERIOD INTO TUESDAY.
HIGH PRESSURE AND DRIER NORTHWEST FLOW WILL SETTLE INTO THE REGION
FOR MIDWEEK AND EXPECTED TO PROVIDE SEASONABLE CONDITIONS AND DRY
WEATHER THROUGH THE END OF NEXT WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 808 PM EDT THU JUN 13 2013

VFR MET CONDS PERSISTING THROUGH THE FORECAST PERIOD. ONLY
EXCEPTION MAY BE SHALLOW GROUND FOG FORMATION ACROSS AIRFIELD
SHORTLY BEFORE/AT DAYBREAK. VERY MOIST GROUND PER LAST NIGHT
RAINFALL AND WARM TOP LAYER SOIL TEMPERATURES...MEASURED 2 INCH
SOIL TEMPERATURE THIS EVENING WAS 68F...CREATE CONDITIONS
FAVORABLE FOR SHALLOW GROUND FOG TO DEVELOP AS SURFACE RIDGELINE
WORKS EASTWARD INTO FAR WESTERN GREAT LAKES. AIR TEMPERATURES
FALLING TO 1-3 DEGREES BELOW WITH STRONG SURFACE BASED INVERSION
DEVELOPING ALL SUGGESTIVE OF FAIRLY WIDESPREAD THOUGH SHALLOW BR
FORMATION ACROSS MUCH OF NORTHERN INDIANA. HAVE CONFINED MVFR
VSBYS TO TEMPO 2 HOURS PENDING LATER REVIEW WITH 06 UTC
ITERATIONS.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...BEACH HAZARDS STATEMENT THROUGH FRIDAY MORNING FOR INZ003.

MI...BEACH HAZARDS STATEMENT THROUGH FRIDAY MORNING FOR MIZ077.

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

&&

$$

SYNOPSIS...OBERGFELL
SHORT TERM...SKIPPER
LONG TERM...NG
AVIATION...MURPHY


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