Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 290934
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
534 AM EDT SAT AUG 29 2015

.SYNOPSIS...
ISSUED AT 330 AM EDT SAT AUG 29 2015

A WEAKENING TROUGH WILL DROP INTO THE LOWER GREAT LAKES TODAY INTO
SUNDAY CAUSING SCATTERED SHOWERS AND POSSIBLY A FEW THUNDERSTORMS.
HIGHS EACH DAY SHOULD REACH THE MID 70S TO LOW 80S. NEXT WEEK WILL
FEATURE WARMER AND MAINLY DRY CONDITIONS AS HIGH PRESSURE BUILDS
IN.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 330 AM EDT SAT AUG 29 2015

MAIN FOCUS TODAY INTO TONIGHT WILL BE ON SHOWER/ISO THUNDER CHANCES
AS A DISJOINTED MID-UPPER LEVEL TROUGH AXIS AND ASSOCIATED WEAK LOW
LEVEL TROUGH WEAKEN ESE INTO THE LOWER LAKES.

CORRIDOR OF DEEPER MOISTURE (PWATS EXCEEDING 1.50 INCHES) WITHIN LOW
LEVEL JET IMMEDIATELY DOWNSTREAM OF THIS FEATURE WILL SLOWLY EDGE
INTO NORTHWESTERN ZONES MID MORNING-EARLY AFTERNOON AND POINTS ESE
THEREAFTER. SUPPORT ALOFT INITIALLY WILL COME FROM WEAK UPPER JET
SUPPORT (RRQ OF A 80 KT NORTHERN LAKES 300-200 MB JET) AND MID
LEVEL UVM/MOISTURE ADVECTION SURGE TIED TO AN EMBEDDED VORT MAX
OUTRUNNING TROUGH AXIS THROUGH CENTRAL LOWER MI. THIS
FORCING/DEEPER MOISTURE WILL CLIP OUR FAR NORTHERN ZONES MID-
MORNING THROUGH AT LEAST EARLY AFTERNOON WHERE POPS WERE
RAISED...ALTHOUGH DID OPT TO DROP THE THUNDER MENTION GIVEN
LIMITED INSTABILITY/MID LEVEL LAPSE RATES. SHOWER COVERAGE WILL BE
MORE ISOLATED IN NATURE FARTHER SOUTHEAST THROUGH EARLY
AFTERNOON...WITH AREAS SOUTHEAST OF THE HWY 24 CORRIDOR LIKELY
REMAINING COMPLETELY DRY.

STEADY IMPROVEMENT IN MOISTURE QUALITY AND WEAK MID LEVEL
DCVA/DEFORMATION TIED TO SHEARED OUT UPPER PV FILAMENT SHOULD KEEP
SCATTERED SHOWERS AROUND INTO THE MID AFTERNOON/EVENING (BEST
CHANCES NW OF HWY 24). ANY THUNDERSTORM ACTIVITY WITH SFC
HEATING/MOISTENING SHOULD REMAIN ISOLATED AT BEST GIVEN THICKER
MID/HIGH CLOUD CANOPY AND WARM COLUMN...WITH CONVECTION HAPPY HI-
RES GUIDANCE LIKELY OVERLY AGGRESSIVE REGARDING SFC HEATING/DEWPOINTS.


&&

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 330 AM EDT SAT AUG 29 2015

ON SUNDAY...THE UPPER LEVEL PV ANOMALY TRACKING ACROSS THE REGION
WILL CONTINUE TO LOSE POTENCY AND BECOME HIGHLY ATTENUATED.
PERSISTENCE OF THIS WEAKENING FORCING COMBINED WITH DIURNAL HEATING
SHOULD YIELD ISOLATED TO SCATTERED AFTERNOON SHOWERS AND
THUNDERSTORMS HOWEVER. WHILE APPRECIABLE MOISTURE SHOULD BE IN PLACE
ON SUNDAY...UNCERTAINTY IN PRECISE MAGNITUDES OF LOW LEVEL MOISTURE
LEND SOME LOWER CONFIDENCE INTO EXTENT OF THUNDER POTENTIAL GIVEN
SENSITIVITY OF SBCAPES TO NEAR SFC MOISTURE WITH CONTINUED MARGINAL
MID LEVEL LAPSE RATES. WEAK FORCING WITH SHEARED VORTICITY MAX MAY
TEND TO MAXIMIZE ACROSS SOUTHEAST PORTIONS OF THE FORECAST
AREA...ALTHOUGH WEAK LAKE ENHANCED LOW LEVEL CONVERGENCE ZONE MAY
ALSO BE A SECONDARY FOCUSING AREA ACROSS NORTHWEST PORTIONS OF THE
CWA DOWNWIND OF LAKE MICHIGAN. WITH DECAYING NATURE OF UPPER PV
ANOMALY HAVE MAINTAINED LOW TO MID CHANCE POPS SUNDAY...PEAKING IN
THE AFTERNOON. SLIGHT CHANCE/LOW CHANCE POPS WERE ALSO MAINTAINED
INTO SUNDAY NIGHT FOLLOWING SOUTHEAST PROGRESSION OF WEAKENING
MID/UPPER LEVEL FORCING.

VORT FILAMENT ASSOCIATED WITH WEAKENING WAVE WILL LIKELY RESIDE
ACROSS THE REGION THROUGH TUESDAY AFTERNOON WITH THE POSSIBILITY OF
WEAK HIGHLY SHEARED WAVES LIFTING NORTHWARD OUT OF THE LOWER/MID MS
RIVER VALLEY TOWARD MID WEEK. THE DOMINANT FEATURE WILL BE
AMPLIFYING BACKGROUND UPPER RIDGING TO AFFECT MUCH OF CENTRAL CONUS
THROUGH THE REMAINDER OF THIS FORECAST PERIOD. MEDIUM RANGE MODELS
DO POINT TOWARD POSSIBILITY OF THE SOUTHERN EXTENT OF PACIFIC WAVE
PROGRESSING THROUGH MEAN RIDGING PROVIDING SOME WEAK FORCING IN THE
WED-THU TIMEFRAME...BUT CONFIDENCE WITH ANY OF THESE EMBEDDED WAVES
IS LOW. THE GENERAL IDEA OF PREVIOUS FORECAST WITH ISOLD DIURNAL
POPS FOR THE TUE-THU PERIOD WAS LEFT AS IS GIVEN THIS PATTERN.

BUILDING HEAT FOR NEXT WEEK COULD BE SOMEWHAT TEMPERED BY OCCASIONAL
WEAK BACKDOOR COOL FRONT TYPE FEATURES IMPACTING THE EASTERN GREAT
LAKES...WITH UPPER RIDGE AXIS LIKELY REMAINING JUST WEST OF THE
LOCAL AREA THROUGH MOST OF THE UPCOMING WEEK WHICH SHOULD CONFINE
HIGHS TO THE MID-UPPER 80S THROUGH MUCH OF THE TUE-FRI PERIOD. THIS
IDEA IS INLINE WITH PREVIOUS GRIDDED FORECAST AND NO SIGNIFICANT
CHANGES WERE MADE TO MAX/MINS AT THIS TIME FOR MUCH OF THE EXTENDED
PERIOD.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 534 AM EDT SAT AUG 29 2015

MAINLY VFR WITH LIGHT SSE WINDS CAN BE EXPECTED TODAY INTO
THIS EVENING. CHANCES FOR SHOWERS WILL INCREASE BY LATER THIS
MORNING/AFTERNOON AT KSBN AND LATE AFTERNOON/EVENING AT KFWA AS
A RIBBON OF DEEPER MOISTURE/WEAK ASCENT FOLDS IN ADVANCE OF AN
APPROACHING SHORTWAVE TROUGH. ALSO COULD SEE A RUMBLE OF
THUNDER BUT CHANCES REMAIN TOO LOW FOR A TSRA OR VCTS MENTION ATTM.
CONTINUED LOW LEVEL MOISTENING ALONG A DIFFUSE LOW LEVEL TROUGH
MAY SUPPORT VIS OR CEILING RESTRICTIONS TOWARD THE END OF THE TAF
CYCLE...BEST CHANCES AT KSBN.

&&

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

$$

SYNOPSIS...STEINWEDEL
SHORT TERM...STEINWEDEL
LONG TERM...MARSILI
AVIATION...STEINWEDEL


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