Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 251055
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
655 AM EDT SAT JUL 25 2015

.SYNOPSIS...
ISSUED AT 352 AM EDT SAT JUL 25 2015

WARM AND HUMID CONDITIONS CAN BE EXPECTED TODAY IN ADVANCE OF AN
APPROACHING FRONTAL BOUNDARY. THIS FRONTAL BOUNDARY WILL PRODUCE A
CHANCE OF SHOWERS AND THUNDERSTORMS TODAY INTO THIS EVENING. A
CHANCE OF THUNDERSTORMS WILL CONTINUE FOR SUNDAY AND MONDAY
ESPECIALLY ALONG AND SOUTH OF US ROUTE 30. HIGH TEMPERATURES THIS
AFTERNOON WILL REACH INTO THE MID 80S. LOW TEMPERATURES TONIGHT
WILL DROP BACK INTO THE MID TO UPPER 60S.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 352 AM EDT SAT JUL 25 2015

OVERALL SCENARIO REMAINS UNCHANGED FOR TODAY/TONIGHT
WITH APPROACHING FRONTAL BOUNDARY TO BE THE PRIMARY FEATURE OF
INTEREST.  SATELLITE IMAGERY EARLY THIS MORNING DEPICTING 5-6K FT
CLOUD DECK WORKING ACROSS NORTHERN ILLINOIS LIKELY MARKING THE
LEADING EDGE OF MORE SIGNIFICANT LOW LEVEL MOISTURE TRANSPORT. THIS
STRONG LOW LEVEL MOISTURE ADVECTION WILL WORK FROM WEST TO EAST
ACROSS THE AREA THIS MORNING. MORE ROBUST CONVECTION TO THIS POINT
HAS BEEN IN CLOSER PROXIMITY TO STRONGER FORCING WITH AN UPPER LEVEL
SHORT WAVE WORKING ACROSS THE UPPER MIDWEST/WESTERN GREAT LAKES
REGION. THIS TROUGH WILL QUICKLY SWEEP ACROSS THE SOUTHERN GREAT
LAKES REGION THROUGH EARLY AFTERNOON. DESPITE LOW LEVEL MOISTURE
ADVECTION...AT LEAST SOME WEAK SURFACE BASED CIN SHOULD PERSIST INTO
EARLY AFTERNOON AND WILL KEEP MAINLY SLIGHT CHANCE POPS THIS MORNING
TO ACCOUNT FOR SOUTHERN PERIPHERY OF FORCING WITH GREAT LAKES SHORT
WAVE AND SOME INCREASE IN ELEVATED INSTABILITY.

CONFIDENCE IN CONVECTIVE POTENTIAL REMAINS RELATIVELY LOW THIS
AFTERNOON. GREAT LAKES SHORT WAVE SHOULD BE DEPARTING TO THE EAST
WHILE PREFRONTAL-TROUGH TYPE AXIS MAY GIVE RISE TO SOME ISOLD-SCT
SHOWERS/THUNDERSTORMS. RATHER WARMISH 800-600 HPA PROFILES MAY EVEN
ARGUE FOR SOME SURFACE BASED CIN LINGERING INTO THIS AFTERNOON. IN
TERMS OF INSTABILITY PROFILES...NAM MAY BE EXHIBITING A TYPICAL
MOIST BIAS AND A BIT OVERDONE WITH INSTABILITY MAGNITUDE.
NONETHELESS WOULD EXPECT MUCAPES ON THE ORDER OF 1500-3000 J/KG
LATER THIS AFTERNOON WITH GREATEST MAGNITUDES ACROSS THE SOUTHWEST.
DEBRIS CLOUDINESS FROM CORNBELT CONVECTION AND THE POSSIBILITY OF
BROKEN STRATOCU FIELD FORMING MAY TEMPER THIS INSTABILITY A BIT
HOWEVER. WITH SOME QUESTIONS AS TO HOW INSTABILITY WILL EVOLVE AND
WEAK FORCING THIS AFTERNOON...WILL ONLY MAINTAIN SLIGHT CHANCE TO
LOW CHANCE POPS AHEAD OF THE COLD FRONT THIS AFTERNOON. MARGINAL
SHEAR PROFILES MAY SUPPORT SOME MULTICELL ORGANIZATION IF STORMS ARE
ABLE TO DEVELOP WITH AN ISOLATED STRONG TO SEVERE STORM NOT
COMPLETELY OUT OF THE QUESTION. ISOLATED DAMAGING WIND GUSTS APPEAR
TO BE THE PRIMARY THREAT THIS AFTERNOON/EARLY EVENING.

MAINTAINED LOW CHANCE POPS MAINLY SOUTHERN TWO THIRDS THIS EVENING
WITH SOME INDICATIONS OF SLIGHTLY BETTER MID LEVEL LAPSE
RATES/INSTABILITY EARLY THIS EVENING ACROSS THE WEST. SOME RESIDUAL
CONVECTIVELY ENHANCED VORT MAX FROM CENTRAL PLAINS MORNING
CONVECTION MAY ALSO BE PROGRESSING THROUGH THE FLOW THIS
EVENING...ALTHOUGH STEERING FLOW WOULD SUGGEST BETTER CHANCE JUST
SOUTHWEST OF THE AREA. PRECIP CHANCES TO GRADUALLY DIMINISH FROM
NORTH TO SOUTH THIS EVENING AS THE FRONT SETTLES SOUTHWARD.


&&

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 352 AM EDT SAT JUL 25 2015

MEDIUM RANGE MODELS IN DECENT AGREEMENT ON CLOSED LOW DIGGING INTO
THE PAC NW SUNDAY... THEN LIFTING NE TO WRN ONTARIO WED AND TO NRN
QUEBEC FRIDAY. EXPECT AMPLIFICATION OF PLAINS RIDGE IN ADVANCE OF
THIS SYSTEM SUNDAY WITH SUBSEQUENT EASTWARD MOVEMENT OF THE RIDGE
ACROSS THE WRN GRTLKS MON-TUE. CDFNT ASSOCIATED WITH THE
MIGRATORY CLOSED LOW MOVG ACROSS ERN CANADA SHOULD MOVE THROUGH OUR
AREA WED BRINGING A GOOD CHC OF TSTMS. POST-FRONTAL COOLER/DRIER
CONDITIONS EXPECTED LATE WEEK WITH NW FLOW ALOFT AND SFC HIGH
BUILDING INTO THE AREA.

MAIN DISAGREEMENT IN MODELS THIS FCST PERIOD COMES EARLY ON WITH
ECMWF INDICATING WEAKER SFC HIGH OVER THE GRTLKS SUNDAY-MONDAY
ALLOWING WK SHRTWV`S MOVG OVER TOP OF PLAINS RIDGE TO IMPACT OUR CWA
WITH POST-FRONTAL CONVECTION. IN DEFERENCE TO THIS SOLUTION AND PREV
FCST LEFT LOW CHC POPS IN SW PORTION OF CWA THROUGH THIS TIMEFRAME.
TEMPS SHOULD BE ABOVE NORMAL SUNDAY-WEDNESDAY AS UPR RIDGE MOVES
THROUGH... HWVR WITH SOME POTENTIAL FOR CONVECTION IN THE AREA
STAYED CLOSE TO COOLER MODEL CONSENSUS IN THIS TIMEFRAME. TEMPS
SHOULD DROP BACK TO A BIT BLO NORMAL LATE WEEK FOLLOWING FROPA
WEDNESDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 633 AM EDT SAT JUL 25 2015

AN UPPER LEVEL SHORT WAVE TRACKING ACROSS THE GREAT LAKES WILL
ALLOW A COLD FRONT TO DROP INTO THE SOUTHERN GREAT LAKES THIS
AFTERNOON. AXIS OF INCREASED LOW LEVEL MOISTURE WILL OVERSPREAD
NORTHERN INDIANA THIS MORNING AHEAD OF THE FRONT...WHICH ALSO WILL
BRING SOME VFR SCT-BKN LOW CLOUDS. CONFIDENCE IN THUNDERSTORM
DEVELOPMENT IS RELATIVELY LOW FOR THIS AFTERNOON AS OVERALL
MID/UPPER LEVEL FORCING WILL BE WEAK. SHORT TERM FORECAST
SOUNDINGS ALSO SUGGEST POSSIBILITY OF SOME WEAK CAPPING PERSISTING
INTO THE AFTERNOON. WILL CONTINUE WITH VCSH MENTION THIS
AFTERNOON/EARLY EVENING DUE TO LOW CONFIDENCE IN POINT OCCURRENCE
AT ANY POINT TERMINAL. SOUTHWEST WINDS AROUND 10 KNOTS AHEAD OF
THE FRONT WILL BECOME LIGHT NORTHWEST THIS EVENING.

&&

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

$$

SYNOPSIS...MARSILI
SHORT TERM...MARSILI
LONG TERM...JT
AVIATION...MARSILI


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