Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 210610
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
210 AM EDT THU AUG 21 2014

.SYNOPSIS...
ISSUED AT 152 AM EDT THU AUG 21 2014

PERIODIC SHOWERS AND THUNDERSTORMS ARE POSSIBLE LATE TONIGHT INTO
FRIDAY AS A WARM FRONT SLOWLY MOVES NORTH INTO THE AREA. HEAT AND
HUMIDITY WILL RETURN BY FRIDAY AS THIS FRONT MOVES NORTH. LOWS
TONIGHT WILL BE IN THE 60S WITH HIGHS ON THURSDAY 80 TO 85.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 251 PM EDT WED AUG 20 2014

TRANQUIL AFTN SO FAR IN SHALLOW POST FNTL AIRMASS. HWVR LL DRYING
HAS NOT BEEN AS EXTENSIVE AS INDICATED IN PRIOR MODEL SOLUTIONS AND
ISOLD SHRA NW SHLD UPTICK SOME THROUGH THIS AFTN GIVEN BAND OF
AGGRAVATED CU ACRS EXTENDING EWD INTO NW OH.

OTRWS PRIMARY DIFFICULTY IS W/NWD RTN OF SFC FNTL ZONE INADV OF NXT
SW DISTURBANCE ROLLING EWD THROUGH SWRN CANADA THIS AFTN. WHILE
MODEL GUIDANCE IS SIMILAR ALOFT...TIMING OF STG LL MSTR FLUX
DIFFERS AND GENERALLY SIDED W/SLWR SOLUTIONS IN LIGHT OF CURRENT
COMPLEX WORKING THROUGH SE IL/SW IN...THUS SLOWED ARRIVAL OF
LIKELY POPS SW HALF UNTIL 12Z. ACTIVE WMFNTL ZONE XPCD TO CONTINUE
ON THU ESP CNTRL/WEST UNDER THE ASSUMPTION THAT OUTFLW/WMFNT
COMPOSITE ANCHORS SFC FNTL ZONE THROUGH NRN IN IF NOT FURTHER
SOUTH. BUMPED SWRN HALF HIGHER YET CUT FAR NE LWR PER CONSENSUS OF
HIGHRES GUIDANCE. PRIOR TEMPS LIKELY TOO WARM AS NOTED IN UPSTREAM
TEMPS UNDER EXTENSIVE CLDS/PRECIP THIS AFTN AND HAVE CUT MAX TEMPS
SOME BUT LIKELY NOT ENOUGH SW. WILL LET NIGHT SHIFT TAKE ANOTHER
LOOK AT THAT.

&&

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 251 PM EDT WED AUG 20 2014

WARM FRONT WILL CONTINUE TO SLOWLY LIFT NORTHEAST THURSDAY NIGHT
INTO FRIDAY. SUSPECT AN MCS WILL DEVELOP SOMEWHERE OVER THE UPPER
MIDWEST THURSDAY NIGHT WITH LLJ STRENGTHENING TO AROUND 30-40 KTS
AND STRONG THETA-E ADVECTION. THIS MCS WILL EVENTUALLY DIVE
SOUTHEAST EARLY FRIDAY MORNING. LOW CONFIDENCE IN EXACT TRACK OF
NOCTURNAL CONVECTION BUT IT COULD IMPACT OUR CWA. THIS COMBINED WITH
POTENTIAL FOR LINGERING CONVECTION FROM THE AFTERNOON SUPPORTS AT
LEAST A HIGH CHANCE POP FOR THURSDAY NIGHT. THERE IS A LOW CHANCE OF
SEVERE WEATHER INTO THE OVERNIGHT PERIOD WITH FORECAST SOUNDINGS
INDICATING AROUND 1000 J/KG OF ELEVATED INSTABILITY. HEAVY RAIN MAY
BE THE BIGGER THREAT WITH PW VALUES AT OR ABOVE 2 INCHES AND
POTENTIAL FOR TRAINING STORMS.

UNCERTAINTY REMAINS UNUSUALLY HIGH FOR PRECIP CHANCES FRIDAY INTO
THE WEEKEND. WARM FRONT WILL LIKELY STALL SOMEWHERE OVER THE GREAT
LAKES AND WASH OUT A BIT. 12Z NWP SUITE CONTINUES TO SHOW WIDESPREAD
CONVECTIVE QPF BUT FORECAST SOUNDINGS ALSO SHOW A DECENT WARM NOSE
AROUND 850MB. COMBINED WITH A LACK OF FORCING MECHANISM AMID
BUILDING LONGWAVE RIDGE...SUSPECT MODEL QPF MAY BE OVERDONE.
MAINTAINED JUST A LOW CHANCE FRIDAY INTO SATURDAY. KEPT SUNDAY AND
MONDAY DRY THOUGH AN ISOLATED STORM CANT BE COMPLETELY RULED
OUT...ESPECIALLY IN OUR NORTHEAST COUNTIES WHERE THE CAP WILL BE
WEAKER. MIDLEVEL TROUGH AND SURFACE COLD FRONT WILL EVENTUALLY
ARRIVE WITH A BETTER CHANCE OF RAIN BUT LATEST MODELS NOW SUGGEST
THAT COULD BE AS LATE AS WEDNESDAY.

SOMEWHAT HIGHER CONFIDENCE ASPECT OF THE FORECAST WILL BE THE HEAT
AND HUMIDITY OVER THE WEEKEND. 850MB TEMPS STILL LOOK TO BE AROUND
20C AND MOST GUIDANCE AGREES ON HIGH TEMPS AROUND 90F. SURFACE
DEWPOINTS ALSO EXPECTED TO HOVER IN THE LOW TO MID 70S...SUPPORTING
HEAT INDEX VALUES NEAR 100F IN OUR SOUTHERN COUNTIES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 152 AM EDT THU AUG 21 2014

UPPER LEVEL JET DYNAMICS WERE HELPING TO TRIGGER ISOLATED STORMS
AND AN EXPANDING AREA OF SHOWERS WELL NORTH OF THE FRONT. STORMS
WERE HIGH BASED...WITH BASES NEAR 100K. HAVE KEPT THE BULK OF THE
TIMING OF THE STORMS IN THE ONGOING TAFS...BUT HAVE RAISED CIGS
EARLY IN THE PERIOD GIVEN THESE HIGH BASES. STORMS LATER TODAY
SHOULD BECOME MORE SURFACE BASED AS THE FRONT MOVES NORTH AND AS
THE ATMOSPHERE DESTABILIZES WITH DAYTIME HEATING. THETA E FLUX
INCREASES TONIGHT...WITH A BETTER CHANCE FOR SHOWERS AND STORMS.
FOR NOW...PLACED VCTS IN THE LAST 6 HOURS OF THE TAF. MAY HAVE TO
ADD A TEMPO GROUP AS MORE PRECISE TIMING BECOMES MORE EVIDENT.

&&

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

$$

SYNOPSIS...SKIPPER
SHORT TERM...T
LONG TERM...AGD
AVIATION...SKIPPER


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