Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 302329
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
729 PM EDT SAT AUG 30 2014

.SYNOPSIS...
ISSUED AT 729 PM EDT SAT AUG 30 2014

SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE TO MOVE ACROSS
NORTHWEST PARTS OF THE AREA THIS EVENING AS LOW PRESSURE TRACKS
INTO THE NORTHERN GREAT LAKES. DRIER AIR WILL BRIEFLY WORK INTO
THE AREA ON SUNDAY BEFORE A COLD FRONT BRINGS RENEWED CHANCES FOR
SHOWERS AND THUNDERSTORMS ON MONDAY. LOWS WILL BE NEAR 70 WITH
HIGHS ON SUNDAY AND MONDAY IN THE LOW TO MID 80S.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 335 PM EDT SAT AUG 30 2014

CONVECTIVE DEVELOPMENT HAS TRIGGERED WHERE THE CLOUDS CLEARED
EARLIER TODAY...MAINLY OVER CENTRAL ILLINOIS TO LOWER LAKE
MICHIGAN AND INTO NORTHERN MICHIGAN. BEST SYNOPTIC SCALE FORCING
ASSOCIATED WITH THE LOW/TROF IN WISCONSIN. FLOW REGIME IS SUCH
THAT THE CONVECTION HAS DEVELOPED IN A STRETCHING DEFORMATION
AXIS. HRRR AND LOCAL WRF SHOW THE SFC BASED FRONTOGENESIS IN THIS
AXIS...

LAPSE RATES AND WIND PROFILES SUPPORT THE POTENTIAL FOR CONVECTIVE
LINES AND INDIVIDUAL LINE SEGMENTS. ISOLATED THREAT FOR SEVERE WIND
GUSTS. DO NOT EXPECT TO SEE SUSTAINED CONVECTIVE DEVELOPMENT AS THE
BOUNDARY LAYER FORCING DOES NOT PERSIST MUCH PAST 04Z.

LOW LEVEL JET KICKS IN OVERNIGHT AND THIS SHOULD BE ENOUGH TO
SUSTAIN MORE ORGANIZED SHRA/TSRA ACROSS THE SOUTHEASTERN HALF OF THE
FORECAST AREA. WHILE THERE IS DISCREPANCY IN TIMING AND INTENSITY
BETWEEN THE MODELS...THE BOUNDARY LAYER CAPE AND WIND PROFILES ARE
VERY SIMILAR AND DO SUPPORT PERSISTENT/LINGERING SHOWERS THROUGH
SUNDAY MORNING. WITH ABUNDANT MOISTURE TAP AND A LONG FETCH OF
ISENTROPIC ASSENT...SOME OF THE SHOWERS COULD PRODUCE MODERATE TO
LOCALLY HEAVY RAINFALL.

AS THE LOW LEVEL JET DECREASES AND THE TROF/DEFORMATION AXIS SHIFTS
EASTWARD...EXPECT IMPROVING CONDITIONS DURING THE DAY SUNDAY AHEAD
OF ANOTHER MORE ROBUST SYNOPTIC SYSTEM APPROACHING THE AREA FOR
MONDAY.

&&

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 335 PM EDT SAT AUG 30 2014

MAIN FOCUS OF LONG TERM IS ON PRECIP/SEVERE WEATHER CHANCES MONDAY
INTO MONDAY NIGHT. WELL DEFINED MID/UPPER LEVEL TROUGH CURRENTLY
DIGGING INTO THE PACIFIC NORTHWEST WILL SWING THROUGH THE GREAT
LAKES LATE MONDAY. TROUGH WILL BE LIFTING AS IT MOVES THROUGH THE
REGION BUT STRONG PUSH OF HEIGHT FALLS AND CVA WILL SUPPORT A DECENT
SURFACE CYCLONE AND ATTENDANT COLD FRONT. PRECIP CHANCES WILL BE
FURTHER AIDED BY GOOD RIGHT ENTRANCE JET DYNAMICS OVER THE SOUTHERN
GREAT LAKES. DEEP AND STRONG SOUTHWEST FLOW AHEAD OF THE TROUGH WILL
EASILY ADVECT HIGH THETA-E AIRMASS BACK INTO OUR AREA ON MONDAY.
AFTERNOON SBCAPE VALUES EXPECTED TO REACH THE 2-3 KJ/KG RANGE AS
HIGH TEMPS CLIMB INTO THE MID...OR PERHAPS UPPER...80S WITH SURFACE
DEWPOINTS IN THE LOW 70S. VERY DYNAMIC WAVE WILL LIKELY SUPPORT
NUMEROUS SHOWERS AND THUNDERSTORMS BUT TIMING WILL BE CRITICAL TO
SEVERE WEATHER CHANCES. LATEST 12Z NWP SUITE KEEPS SURFACE BOUNDARY
WEST OF OUR CWA UNTIL TUESDAY MORNING. ISO/SCT CONVECTION MAY
DEVELOP IN THE WARM SECTOR MONDAY AFTERNOON ALONG WEAK PREFRONTAL
TROUGH AS SUGGESTED BY THE LATEST NAM12 BUT EXPECT BULK OF THE
ACTIVITY WILL BE TIED TO THE ACTUAL COLD FRONT LATE MONDAY NIGHT.
BETTER WIND PROFILES...WITH 0-6KM SHEAR OF 30+ KNOTS...WILL ALSO BE
TIED CLOSER TO THE FRONT. DESPITE MORE THAN ADEQUATE
SHEAR...MIDLEVEL LAPSE RATES OF 6-7 C/KM ARE ONLY WEAKLY SUPPORTIVE
OF A NOCTURNAL SEVERE WEATHER THREAT. FORECAST SOUNDINGS INDICATE
ONLY AROUND 1000 J/KG OF ELEVATED INSTABILITY MONDAY NIGHT....PLENTY
FOR WIDESPREAD THUNDERSTORMS BUT SEVERE POTENTIAL IS LESS CLEAR.
THERE WILL BE A THREAT FOR SEVERE WINDS...AND POTENTIAL
ROTATION...WITH ANY SUBSTANTIVE UPDRAFTS THAT MANAGE TO DEVELOP BUT
LATE ARRIVAL OF FRONT MAY LIMIT CHANCES FOR A WIDESPREAD SEVERE
WEATHER EVENT. PUSHED BACK TIMING OF POPS BUT ALSO INCREASED THEM A
BIT BASED ON LATEST MODEL SOLUTIONS. COULD ALSO BE A THREAT FOR
STRONGER STORMS IN OUR FAR SOUTHEAST COUNTIES LATE TUESDAY MORNING
IF SURFACE BOUNDARY IS SLOW ENOUGH TO EXIT THE CWA.

QUIET WEATHER EXPECTED MIDWEEK BEFORE ANOTHER TROUGH APPROACHES NEXT
WEEKEND. SCT CONVECTION MAY BE POSSIBLE THURSDAY INTO FRIDAY AS WARM
FRONT LIFTS NORTH ONCE AGAIN BUT BEST CHANCES LOOK TO HOLD OFF UNTIL
THE WEEKEND. AFTER A BRIEF BREAK TUES AND WED...HEAT AND HUMIDITY
WILL RETURN FOR THE END OF THE WEEK AS ACTIVE WEATHER PATTERN
CONTINUES.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 729 PM EDT SAT AUG 30 2014

VFR CONDS THIS EVENING WILL GIVE WAY TO A PD OF MVFR/IFR CONDS LT
TONIGHT AS WK SFC TROUGH STALL ACRS THE AREA. FORCING ALG TRAILING
BNDRY ASSOCD/W PARENT SW SHIFTING EWD THROUGH NRN WI HAS SO FAR BEEN
GENERALLY POOR W/FRACTURED...POORLY DVLPD CONVECTIVE LINE EXTENDING
FM ERN IL NEWD THROUGH NW IN/SRN MI. DOUBT THIS WILL IMPROVE
OVERNIGHT AS NR TERM HIGHRES GUIDANCE WEAKENS VEERED LLJ AFT
MIDNIGHT AND W/NO REAL PUSH TO SFC BNDRY DOUBT CONVN MAKES IT OUT OF
NWRN ZONES. THUS WILL KEEP W/PRIOR TEMPO TSRA MENTION AT KSBN WHICH
MAY NEED TO BE EXTENDED A BIT FURTHER. HWVR CONVN XPCD TO REMAIN NW
OF KFWA AND DROPPED PREV VCTS MENTION THERE. HIGH BNDRY LYR MSTR
REMAINS IN PLACE AND W/DECAYING SFC GRADIENT AND SOME CLRG OVERNIGHT
XPC SOME FOG TO DVLP.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR LMZ043-046.

&&

$$

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


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