Area Forecast Discussion
Issued by NWS Northern Indiana

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377
FXUS63 KIWX 161011
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
611 AM EDT SAT MAY 16 2015

.SYNOPSIS...
ISSUED AT 136 AM EDT SAT MAY 16 2015

THE COMBINATION OF A STALLED FRONT ACROSS THE REGION AND A SERIES
OF UPPER LEVEL DISTURBANCES TRACKING ACROSS THE AREA WILL RESULT
IN A CONTINUED CHANCE OF SHOWERS AND THUNDERSTORMS TODAY AND
TONIGHT. SHOWERS AND THUNDERSTORMS WILL BECOME MORE LIKELY BY
SUNDAY NIGHT AS A STRONGER SYSTEM APPROACHES FROM THE WEST.
OTHERWISE...WARM CONDITIONS WILL CONTINUE THROUGH THE WEEKEND.
HIGH TEMPERATURES THIS AFTERNOON WILL REACH AROUND 80...WITH LOW
TEMPERATURES TONIGHT DROPPING INTO THE MIDDLE 60S.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 402 AM EDT SAT MAY 16 2015

NORTHWARD SHIFT TO LOW/MID LEVEL THETAE GRADIENT WILL CONTINUE THIS
MORNING AS A SERIES OF SMALL SCALE SHORT WAVES LIFT INTO NORTHEAST
INDIANA. THE MOST PRONOUNCED OF THESE SMALL SCALE VORTICES APPEARS
TO BE TRACKING ACROSS CENTRAL INDIANA AT THIS TIME. THROUGH THE
EARLY MORNING HOURS HAVE INDICATED A SOUTH TO NORTH INCREASE IN POPS
FOLLOWING PROGRESSION OF SHORT WAVE FORCING/MOISTURE
ADVECTION...AND AN ISOLD THUNDER MENTION WITH STILL SOME 250-500
K/G MUCAPES ANALYZED PER LATEST RUC ANALYSIS FOR SLIGHTLY ELEVATED
PARCELS. COVERAGE OF SHOWERS AND ISOLATED THUNDER SHOULD GRADUALLY
WIND DOWN IN THE 12-14Z TIMEFRAME.

LOOKING UPSTREAM...ADDITIONAL WEAK SHORT WAVES WILL TEND TO SHEAR
WITH NORTHWARD EXTENT AS THEY ENTER THE LOCAL AREA FROM THE
LOWER/MID MS VALLEY THIS AFTERNOON. QUITE CHALLENGING TO CLEARLY
PICK OUT THESE UPSTREAM WAVES THIS MORNING...ALTHOUGH BULK OF
GUIDANCE WOULD SUGGEST SOUTH/SOUTHEAST LOCATIONS WITH MORE
FAVORABLE SHORT WAVE TRACK THROUGH THIS AFTERNOON. A MODEST
MID/UPPER LEVEL SPEED MAX IS ALSO EXPECTED TO LIFT ACROSS EAST
CENTRAL INDIANA/WESTERN OHIO THIS AFTERNOON WHICH MAY ALSO TEND TO
FOCUS BETTER CONVECTIVE CHANCES. HAVE CONTINUED WITH MID TO HIGH
CHANCE POPS THROUGH THE DAY WITH HIGHEST POPS FOCUSED ACROSS
SOUTHEAST THIRD OF THE AREA. INSTABILITY MAGNITUDES SHOULD BE
SOMEWHAT LESS THAN YESTERDAY AS LOW LEVEL THERMAL RIDGE IS
WEAKER...AND GENERALLY EXPECTING SURFACED BASED CAPES ON THE ORDER
OF 750-1500 J/KG THIS AFTERNOON. SHEAR ALSO IS EXPECTED TO BE ON THE
MARGINAL SIDE WITH THE POSSIBLE EXCEPTION OF FAR SOUTHEAST AREAS
WHERE AFOREMENTIONED MID/UPPER JET STREAK MAY PROMOTE DEEP LAYER
SHEAR VALUES APPROACHING THE 25-30 KNOT RANGE. THIS MAY HELP TO
CONCENTRATE SCATTERED CONVECTION WITH THE APPROACH OF THE NEXT
SHORT WAVE ACROSS THE SOUTHEAST THIRD...BUT SEVERE WEATHER IS NOT
EXPECTED. NO CHANGE TO PREVIOUS FORECAST WITH HIGHS AROUND 80 FOR
TODAY...ALTHOUGH IF GREATER CONVECTIVE COVERAGE IS ABLE TO BECOME
ESTABLISHED ACROSS THE SOUTH/SOUTHEAST...HIGHS MAY BE A BIT TOO
WARM.

FORECAST CONFIDENCE FOR TONIGHT IS RELATIVELY LOW GIVEN THE LOW
PREDICTABILITY WITH SMALLER SCALE WAVES IN SOUTHWEST FLOW...BUT
CURRENT INDICATIONS SUGGEST THE DEPARTING SHORT WAVE ACROSS
SOUTHEAST HALF OF THE AREA MAY PROVIDE BEST EVENING CHANCES ACROSS
THESE LOCATIONS. OTHERWISE...FORCING LOOKS QUITE MEAGER FOR MOST OF
THE NIGHT. MOIST AIR MASS/CLOUD COVER SHOULD KEEP TEMPS IN THE MID
60S FOR LOWS MOST LOCATIONS. SOME PATCHY FOG IS
POSSIBLE...PARTICULARLY ACROSS THE FAR NORTH IN CLOSER PROXIMITY TO
STALLED LOW LEVEL FRONT BUT WILL OMIT FROM FORECAST AT THIS TIME.

&&

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 402 AM EDT SAT MAY 16 2015

PRECIP CHANCES STEADILY INCREASE INTO LATE SUNDAY AS LARGE CUTOFF
LOW FINALLY BEGINS TO MAKE SOME EASTWARD PROGRESS. STILL A FAIR
AMOUNT OF UNCERTAINTY REGARDING EXACT TIMING AND EVOLUTION OF
NORTHEAST EJECTION THOUGH. MAIN VORTICITY LOBE WILL PASS WELL TO OUR
NORTHWEST WITH JUST A FEW TRAILING EMBEDDED SHORTWAVES TO SPARK
CONVECTION IN OUR CWA. LEANED TOWARD THE LATEST GFS SOLUTION WHICH
HAS SUPPORT FROM THE ECMWF...SEVERAL OF THE NEWEST HI-RES RUNS...AND
IS IN LINE WITH PREVIOUS FORECAST. EXPECT BEST CHANCES FOR RAIN
DURING THE LATE AFTERNOON AND EVENING WITH LITTLE PRECIP BEFORE 18Z.
AFOREMENTIONED MODELS SHOW DECENT SHORTWAVE/PREFRONTAL SURFACE
TROUGH LIFTING INTO THE GREAT LAKES AT THIS TIME...COMMENSURATE WITH
A NOTED SURGE IN LOW LEVEL THETA-E ON THE NOSE OF A 30-35 KT 850MB
JET. SHOULD ALSO BE ABLE TO CAPITALIZE ON SOME MODERATE
INSTABILITY...THOUGH IT WILL STEADILY WANE AFTER SUNSET.
STILL...WOULD LIKE TO SEE BETTER DEFINED SYNOPTIC FORCING AND MODEL
AGREEMENT BEFORE BOOSTING POP FORECAST AND WILL HOLD WITH LOW END
LIKELY FOR NOW. MIDLEVEL LAPSE RATES ARE A LITTLE BETTER (6-6.5
C/KM) BUT MLCAPE VALUES STILL STRUGGLE TO GET MUCH ABOVE 1000
J/KG...ESPECIALLY BY 00Z WHEN THE BETTER 0-6KM SHEAR SPREADS INTO
THE AREA. SEVERE RISK IS THEREFORE LOW...CONFINED MAINLY TO OUR
WESTERN HALF DURING THE EARLY EVENING PERIOD. STRONG WIND GUSTS AND
SMALL HAIL WOULD BE THE PRIMARY THREATS IF SEVERE WEATHER DOES OCCUR.

ACTUAL COLD FRONT WILL NOT CROSS THE AREA UNTIL MONDAY NIGHT SO
COULD STILL BE SOME RESIDUAL CONVECTION...ESPECIALLY OVER OUR
EASTERN COUNTIES...ON MONDAY. COVERAGE/CHANCES WILL DEPEND ON HOW
SUNDAY NIGHT`S PRECIP EVOLVES WITH A POSSIBILITY OUR AREA WILL BE
TOO "WORKED OVER" FOR WIDESPREAD PRECIP. LLJ WEAKENS AND VEERS BY
MONDAY MORNING WITH BEST MOISTURE CONVERGENCE SHUNTED TO OUR EAST.
SIMILARLY...INSTABILITY REMAINS ON THE MARGINAL SIDE AND SEVERE RISK
IS LOW. INHERITED CHANCE POPS SEEM APPROPRIATE...THOUGH WILL BUMP
THEM UP A BIT IN OUR FAR EASTERN COUNTIES WHERE SLIGHTLY BETTER
MOISTURE/INSTABILITY RESIDE. REST OF THE WEEK STILL LOOKING COOL AND
DRY AS CANADIAN ANTICYCLONE REMAINS LOCKED OVER THE REGION.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 544 AM EDT SAT MAY 16 2015

THE COMBINATION OF LOW/MID LEVEL MOISTURE TRANSPORT AND SEVERAL
WEAK EMBEDDED WAVES IN SOUTHWEST FLOW HAS LED TO NARROW BAND OF
SHOWERS FROM KSBN TO NORTH OF KFWA EARLY THIS MORNING. THIS BAND
WILL LIFT NORTH OF KSBN BY 12Z. A LULL IS THEN EXPECTED IN TERMS
OF PRECIP COVERAGE FOR THE TERMINALS...ALTHOUGH ADDITIONAL
IMPULSES EJECTING OUT OF SOUTHERN MISSOURI/ARKANSAS WILL POSE A
THREAT FOR ADDITIONAL SCATTERED SHOWERS AND THUNDERSTORMS FROM
LATE MORNING INTO THIS AFTERNOON. CURRENT INDICATIONS WOULD
SUGGEST A MORE FAVORABLE SHORT WAVE TRACK FOR NORTHEAST
INDIANA. THUS...GREATER CONVECTIVE COVERAGE MAY AFFECT KFWA LATER
THIS MORNING INTO THIS AFTERNOON. HOWEVER WITH LOW CONFIDENCE IN
TIMING AND POINT PROBABILITIES...WILL LIMIT MENTION TO VCSH AT
KFWA AT THIS TIME. LIGHT SOUTH WINDS THIS MORNING WILL BECOME
SOUTHWEST 10 TO 15 KNOTS WITH DIURNAL MIXING THIS MORNING...AND
THEN LIGHT SOUTH AGAIN TONIGHT. DID ADD SOME MVFR VSBYS AT KSBN
LATER TONIGHT IN CLOSER PROXIMITY TO OLD LOW LEVEL BOUNDARY.

&&

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

$$

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


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