Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 011807
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
207 PM EDT SAT AUG 1 2015

.SYNOPSIS...
ISSUED AT 320 AM EDT SAT AUG 1 2015

EXPECT MOSTLY SUNNY SKIES THROUGH EARLY AFTERNOON...THEN
INCREASING CLOUDS AND A CHANCE OF SHOWERS AND THUNDERSTORMS THIS
EVENING. HIGHS WILL RANGE FROM THE UPPER 70S NEAR LAKE MICHIGAN TO
THE MID 80S INLAND.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 320 AM EDT SAT AUG 1 2015

ANOTHER DIFFICULT SHRT TERM PD ON TAP. ANOTHER IN A
SERIES OF UPR DISTURBANCES OVR SWRN ONTARIO WAS NOTED THIS MORNING
ROTATING E/SEWD THROUGH BASED OF UPR LOW CNTRD OVR JAMES BAY W/SOME
DECAYING CONVN ALG THE N SHORE OF LK SUP. HWVR UNLIKE YDA SIG
SCOURING OF LL THETA-E RIDGING HAD OCCURRED WHICH BY ALL SHRT TERM
GUIDANCE ACCOUNTS WILL TAKE SOME TIME TO RECOVER. THAT SAID MEAN
TROUGHING ASSOCD/W JAMES BAY UPR LOW XPCD TO FLATTEN THIS PD AS SWRN
ONTARIO DISTURBANCE WRAPS EWD. SFC TROUGH IN ASSOCN/W THIS FTR XPCD
TO PASS THROUGH THE SRN/WRN LAKES THIS EVENING W/ROBUST RENEWED LL
THETA-E PLUME FOLDING EWD INTO THE WRN CWA TWD 00Z AND PROGRESSING
INTO OH BY LT EVENING. BEST OVERLAP OF MSTR/FORCING AND FNTL TIMING
WARRANTS AN APPRECIABLE BUMP TO POPS THIS EVENING WRN HALF FOLLOWED
BY A TAIL OFF W/E/SE EXTENT BY LT EVENING. OTRWS SEASONABLE TEMPS
XPCD AGAIN THROUGH THE PD W/ENLARGED DIURNAL SPREADS FVRD AGAIN.

&&

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 320 AM EDT SAT AUG 1 2015

NORTHWEST FLOW REGIME ALOFT WILL PERSIST UNDER A HUDSON BAY NEGATIVE
HEIGHT ANOMALY THAT WILL DRIFT ESE INTO SOUTHEAST CANADA. THE RESULT
WILL BE TEMPS TRENDING COOLER THAN NORMAL AND SEVERAL OPPORTUNITIES
FOR RAIN/STORMS AS A SERIES OF MID LEVEL IMPULSES PROPAGATE THROUGH.

THE MAIN FOCUS SUNDAY INTO EARLY MONDAY WILL BE CONVECTIVE
TRENDS/CHANCES IN ADVANCE OF A COLD FRONT MODELED TO TRANSLATE
THROUGH SUNDAY NIGHT/EARLY MONDAY. THE ASSOCIATED SHARP MID LEVEL
SHORTWAVE/HEIGHT FALLS INTO THE GREAT LAKES WILL AID IN RAMPING OF
PRE-FRONTAL LOW LEVEL JET INTO THE LOWER LAKES. THE RESULTING
INCREASE IN MOISTURE/INSTABILITY WILL PRIME THE LOCAL AREA FOR
CONVECTION. HOWEVER...CHANCES DURING THE DAY SUNDAY APPEAR
LOW...WITH MORNING/EARLY AFTERNOON ACTIVITY INTO NORTHWEST ZONES
DEPENDENT ON TIMING OF A WEAK LEAD SHORTWAVE AND SURVIVAL OF
SATURDAY NIGHT`S UPSTREAM CONVECTION INTO THE LOWER LAKES. BETTER
CHANCES APPEAR TO BE NORTHWEST IN AN AREA OF MORE FOCUSED MOISTURE
CONVERGENCE/ISENTROPIC ASCENT.

GROWING SFC BASED INSTABILITY WITHIN WARM SECTOR EXPECTED BY SUNDAY
AFTERNOON/EARLY EVENING. HOWEVER...HELD WITH LOW POPS GIVEN
INCREASED CAPPING/EML OVERSPREAD WITH REGION CAUGHT IN BETWEEN UPPER
WAVES. COLD FRONTAL PASSAGE LOOKS GOOD FOR A ROUND OF RAIN/STORMS
SUNDAY NIGHT...BUT HELD OFF ON INCREASING INTO THE LIKELY CATEGORY
GIVEN LINGERING MODEL TIMING/STRENGTH DIFFERENCES. WILL NEED TO
MONITOR THE POTENTIAL FOR ORGANIZATION INTO A MCS (WIND THREAT)
GIVEN STRONG 0-3 KM FLOW/SHEAR AND LINGERING MODERATE INSTABILITY
(THANKS TO STEEPENING MID LEVEL LAPSE RATES AND MID/UPPER 60S SFC
DEWPOINTS).

THE AFOREMENTIONED FRONT WILL FOCUS/SUPPRESS SOUTH IN THE VICINITY
OF THE OHIO/MID MS VALLEYS FOR MUCH OF NEXT WEEK IN RESPONSE TO
SOUTHERN DRIFT OF HUDSON BAY LOW. NORTHERLY TO EASTERLY FLOW AT THE
SFC WILL SUPPORT BELOW NORMAL TEMPS AND MAINLY DRY CONDITIONS ACROSS
AT LEAST THE NORTHERN HALF OF THE FORECAST AREA. LOWER CONFIDENCE
FOR AREAS ALONG/SOUTH OF THE HWY 30 CORRIDOR REGARDING RAIN/EMBEDDED
THUNDER CHANCES TUESDAY THRU WEDNESDAY NIGHT GIVEN CLOSE PROXIMITY
TO ACTIVE FRONTAL SLOPE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 203 PM EDT SAT AUG 1 2015

VFR CONDITIONS EXPECTED THIS PERIOD. VERY SUBTLE MOISTURE
ADVECTION AND WEAK SHORT WAVE LATE THIS AFTERNOON AND EARLY
EVENING TO PASS THROUGH TAF SITES. NOT OVERLY IMPRESSIVE BUT A FEW
HIRES MODELS STILL SHOW POSSIBILITY OF SOME ISOLATED SHRA
DEVELOPING. OPTED TO REPLACE VCTS WITH VCSH GIVEN VERY LOW CHANCE
OF OCCURRENCE AND LACK OF GOOD FORCING AND MOISTURE. OTHERWISE
EXPECT DRY CONDITIONS OVERNIGHT WITH LIGHT AND VARIABLE WINDS.
SFC WINDS WILL INCREASE TO BETWEEN 10 AND 20 KNOTS SUNDAY MORNING
WELL AHEAD OF A STRONG COLD FRONT. SLIGHT CHANCE FOR TSRA BEFORE
18Z BUT NOT ENOUGH CHANCE FOR INCLUSION AT TERMINALS AT THIS TIME.

&&

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

$$

SYNOPSIS...T
SHORT TERM...T
LONG TERM...STEINWEDEL
AVIATION...LASHLEY


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