Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 081725
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
125 PM EDT TUE JUL 8 2014

.SYNOPSIS...
ISSUED AT 1053 AM EDT TUE JUL 8 2014

AN UPPER LEVEL DISTURBANCE WILL TRACK NORTHEAST OUT OF THE REGION
THIS EVENING. THIS WILL ALLOW RAIN AND EMBEDDED THUNDERSTORMS TO
END BY EARLY TONIGHT. A HIGH PRESSURE AREA WILL BUILD INTO THE
REGION THURSDAY. HIGHS THROUGH FRIDAY WILL BE IN THE 70S TO AROUND
80. LOWS WILL BE IN THE MID 50S TO LOWER 60S.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 410 AM EDT TUE JUL 8 2014

EVOLUTION OF ONGOING MCS ACROSS CENTRAL ILLINOIS AND CONVECTIVE
TRENDS THIS AFTERNOON WILL CONTINUE TO BE THE PRIMARY SHORT TERM
FORECAST CONCERNS.

IR SATELLITE HAS INDICATED A SHARP WARMING OF CLOUD TOPS WITH MCS
CURRENTLY WORKING ACROSS CENTRAL ILLINOIS. ORIENTATION OF 1000 J/KG
MUCAPE AXIS FROM CENTRAL ILLINOIS INTO NORTHWEST INDIANA...ALONG
WITH 0-6 KM EFFECTIVE SHEAR MAGNITUDES OF 35-40 KNOTS SHOULD TEND TO
FAVOR EASTWARD PROPAGATION TO REMNANT MCS...WORKING INTO WESTERN
PORTIONS OF THE AREA IN THE 10Z-12Z TIMEFRAME. FAIRLY STRONG LOW
LEVEL MOISTURE TRANSPORT IS PRECEDING THIS MCS...SO WOULD EXPECT
MAINTENANCE OF SHOWERS AND THUNDERSTORMS INTO SOUTHWEST PORTIONS OF
THE AREA THIS MORNING...OR A MORE LOCALIZED BRIEF RE-
INTENSIFICATION OF CONVECTION. THE COMBINATION OF LOW LEVEL THETAE
ADVECTION...LOW LEVEL MOISTURE TRANSPORT...AND INCREASING SYNOPTIC
SUPPORT FROM UPPER LEVEL SHORT WAVE TROUGH APPROACHING MID MS
RIVER VALLEY SHOULD ALSO SUPPORT NORTHWARD EXPANSION OF RAIN
SHOWERS/EMBEDDED THUNDER ACROSS THE NORTHWEST OVER NEXT SEVERAL
HOURS. SMALLER SCALE CONVECTIVELY ENHANCED VORT WITH ANOTHER
DECAYING MCS ACROSS SOUTHEAST WISCONSIN SHOULD BE ANOTHER FACTOR
IN SUPPORTING EXPANDING PRECIP COVERAGE ACROSS NORTHWEST SECTIONS.
PREVIOUS FORECAST GRIDS STILL APPEAR TO CAPTURE CURRENT TRENDS
WELL...WITH BULK OF PRECIPITATION ACROSS THE AREA FALLING IN THE
12Z-18Z TIMEFRAME. CURRENT THINKING IS THAT SOME GUSTY WINDS INTO
THE 30 MPH RANGE ARE POSSIBLE ALONG LEADING EDGE OF MCS ACROSS THE
WEST/SOUTHWEST EARLY THIS MORNING GIVEN MORE FAVORABLE INSTABILITY
PERSISTING ACROSS THESE LOCATIONS. MODELS REMAIN PERSISTENT IN
ENHANCING COVERAGE OF RAIN/EMBEDDED THUNDER TOWARD 15Z ACROSS
REMAINDER OF THE AREA...AS LARGE SCALE SYNOPTIC SUPPORT INCREASES
IN ASSOCIATION WITH MID MS VALLEY UPPER TROUGH.

CONVECTIVE TRENDS OF SOMEWHAT LOWER CONFIDENCE THIS AFTERNOON IN
WAKE OF MORNING PRECIPITATION. NAM REMAINS A BIT SLOWER IN CLEARING
SFC TROUGH/COOL FRONT ACROSS THE AREA WITH SOME INDICATIONS OF
RESPECTABLE LOW LEVEL THETAE RIDGE/MODERATE INSTABILITY AXIS NOSING
INTO SOUTHEAST SECTIONS OF THE AREA...HOWEVER NAM LIKELY OVERDONE
IN THIS REGARD WITH PRONOUNCED LOW LEVEL MOIST BIAS. MODEL
CONSENSUS UPPER LEVEL Q-VEC CONVERGENCE FIELDS ALSO SUPPORT
STRONGEST UPPER FORCING TRANSLATING EAST AND SOUTH OF LOCAL AREA
CLOSE TO THE 21Z TIMEFRAME. A SMALL WINDOW MAY EXIST FOR ISOLD/SCT
SHRA/TSRA RE- DEVELOPMENT DURING THE MID TO LATE AFTERNOON
HOURS...PARTICULARLY ACROSS THE EXTREME SOUTHEAST. GIVEN
BACKGROUND SHEAR...SOME CONCERN MAY EXIST FOR ISOLD SVR THREAT
DEPENDING ON AVAILABLE INSTABILITY...BUT GREATER THREAT DOES APPEAR
TO BE SOUTHEAST OF LOCAL AREA.

UPPER LEVEL TROUGH OVERHEAD FOR THE EARLY EVENING HOURS SHOULD
PROVIDE STEEP LOW/MID LEVEL LAPSE RATES...WITH ISOLATED SHRA/TSRA
STILL A POSSIBILITY. GIVEN SLOW EASTWARD EJECTION OF UPPER TROUGH
AND WEAK LOW LEVEL CAA WITH BROAD WEAK THERMAL TROUGHING...DID
SLIGHTLY NUDGE UP SKY COVER FOR TONIGHT WITH A POSSIBILITY OF SOME
LINGERING STRATOCU...AND PERHAPS SOME PATCHY FOG.

&&

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 410 AM EDT TUE JUL 8 2014

COOL/DRY TO START THE PERIOD WITH SHOWER/STORM CHANCES AND NEAR
NORMAL TEMPS RETURNING THIS WEEKEND...

SHORTWAVE ENERGY WITHIN BROAD MID LEVEL TROUGH AXIS WILL PIVOT
THROUGH THE GREAT LAKES REGION ON WEDNESDAY. WEAK HEIGHT FALLS/CVA
AND IMPRESSIVE -20C 500MB COLD POCKET WITH THIS VORT MAX WILL MAINLY
PASS NORTHEAST OF THE FORECAST AREA. THIS AND CONTINUED LOW LEVEL
DRYING/STABLE LAKE SHADOW PRECLUDES A POP MENTION WITH HIGHS ONLY IN
THE MID-UPPER 70S. RELAXATION OF EASTERN CONUS TROUGH WILL ALLOW SFC
HIGH PRESSURE TO BUILD IN WEDNESDAY NIGHT INTO THURSDAY RESULTING IN
MORE QUIET/PLEASANT WX.

THETA-E ADVECTION/SHORTWAVE DRIVEN CONVECTION IN FLATTENED MID LEVEL
FLOW AND RETURN SOUTHWESTERLY LOW LEVEL FLOW WILL BRING CHANCES FOR
SHOWERS/THUNDER BACK INTO THE FORECAST BY FRIDAY NIGHT-SATURDAY.
COULD SEE CONVECTION ALSO CLIP THE AREA AROUND SUNDAY AS INSTABILITY
GRADIENT/COMPOSITE OUTFLOW LAYS OUT IN THE VICINITY (WEST TO EAST)
UNDER A STRENGTHENING UPPER MIDWEST/NORTHERN LAKES UPPER JET.
ANOTHER SURGE OF COOLER/DRIER AIR IS EXPECTED EARLY NEXT WEEK AS AN
UPPER TROUGH AMPLIFIES INTO THE GREAT LAKES/ONTARIO (EXCELLENT MODEL
AGREEMENT)...LIKELY SENDING ANOTHER COLD FRONT THROUGH AROUND SUNDAY
NIGHT OR MONDAY...WITH COOLER/LESS HUMID WX ANTICIPATED IN ITS
WAKE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 119 PM EDT TUE JUL 8 2014

VFR CONDITIONS ANTICIPATED THROUGH THE TAF PD. SFC TROF AXIS
SWINGING EAST THRU NORTHEAST IN THIS AFTN AS UPPER DISTURBANCE
NOTED ON W/V IMAGERY ACROSS LK MI PUSHES EAST THROUGH SOUTHERN
MICHIGAN. ISOLATED TSRA POSSIBLE ACROSS THE REGION THIS
AFTERNOON...BUT LOW CONFIDENCE/COVERAGE PRECLUDES TAF MENTION.
SUBSIDENCE ON THE BACKSIDE OF GREAT LAKES UPPER TROF W/ RESIDUAL
LOW LVL MOISTURE COULD BRING AN MVFR CIG/VISBY TO TERMINALS AFTER
10Z...BUT KEPT FORECAST VFR FOR NOW.

&&

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

$$

SYNOPSIS...SKIPPER
SHORT TERM...MARSILI
LONG TERM...STEINWEDEL
AVIATION...NG


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