Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 030943
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
543 AM EDT THU SEP 3 2015

.SYNOPSIS...
ISSUED AT 155 AM EDT THU SEP 2 2015

A SERIES OF UPPER LEVEL DISTURBANCES WILL TRACK ACROSS THE GREAT
LAKES AND OHIO VALLEY REGIONS TODAY AND TONIGHT RESULTING IN
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS...ESPECIALLY THIS
AFTERNOON INTO THIS EVENING. OTHERWISE...VERY WARM AND HUMID
CONDITIONS WILL PERSIST THROUGH THE REST OF THE WEEK. HIGHS WILL
BE IN THE MID TO UPPER 80S. LOWS WILL BE IN THE MID TO UPPER 60S.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 347 AM EDT THU SEP 3 2015

THE SHORT TERM FORECAST CHALLENGES THIS CYCLE CONTINUE
TO CENTER ON CONVECTIVE CHANCES...AND IMPACTS OF CLOUD COVER ON
TEMPS TODAY.

AN UPPER LEVEL LEAD SHORT WAVE WORKING ACROSS NORTHWEST INDIANA DID
HAVE SOME ISOLATED SHOWERS ASSOCIATED WITH IT OVER THE PAST FEW
HOURS...ALTHOUGH RECENT TRENDS HAVE BEEN TOWARD DIMINISHMENT AS
CONVECTIVE INHIBITION HAS INCREASED DURING THE OVERNIGHT HOURS. NOT
COMPLETELY OUT OF THE QUESTION A FEW ISOLATED SHOWERS MAY ACCOMPANY
THIS FEATURE ACROSS NORTHWEST INDIANA/SOUTHWEST LOWER MICHIGAN
THROUGH DAYBREAK...BUT PRIMARY FEATURE OF INTEREST FOR LATER
TODAY WILL BE NEXT SLIGHTLY MORE PRONOUNCED UPSTREAM VORT MAX
ACROSS NORTHERN LAKE MICHIGAN/NORTHERN LOWER MICHIGAN. THIS
DISTURBANCE WILL DROP SOUTHEAST INTO NORTHEAST INDIANA/NORTHWEST
OHIO LATE THIS AFTERNOON. WESTERLY LOW LEVEL FLOW AHEAD OF THIS
FEATURE WILL BRING SOME INCREASING 925-850 HPA MOISTURE THIS
MORNING...WITH ISOLATED TO SCATTERED SHOWER/THUNDERSTORMS EXPECTED
TO DEVELOP ACROSS SOUTHERN LOWER MICHIGAN DURING THE MID TO LATE
MORNING HOURS IN ADVANCE OF THIS VORT MAX.

CONVECTIVE COVERAGE SHOULD INCREASE ESPECIALLY IN THE 18Z-00Z
TIMEFRAME...AND PRIMARILY ACROSS NORTHEAST HALF OF THE AREA WITH A
MORE PRONOUNCED WEAKNESS IN MID/UPPER LEVEL RIDGE AS THIS WAVE DROPS
INTO THE AREA. LOW LEVEL CONVERGENCE ACROSS THE SOUTHERN/EASTERN
GREAT LAKES ALSO SHOULD GET ENHANCED BY BACKDOOR COOL FRONT TYPE
FEATURE LATE AFTERNOON/EARLY EVENING. NAM MAY BE A BIT TOO BULLISH
WITH INSTABILITY...BUT GFS LIKELY UNDERDONE ONCE AGAIN. GENERALLY
EXPECTING BETWEEN 1000-2000 J/KG OF SURFACE BASED INSTABILITY THIS
AFTERNOON...WHICH WILL BE DETERMINED IN PART BY EXTENT OF MID LEVEL
WAA CLOUDINESS THAT FILLS IN ACROSS THE AREA THIS MORNING. SHEAR
PROFILES WILL REMAIN WEAK TODAY...ALTHOUGH A MODEST 25-30 KNOT
700-500 HPA SPEED MAX ROTATING THROUGH BASE OF THIS SHORT WAVE
SHOULD INCREASE DEEP LAYER SHEAR INTO THE 20-25 KNOT RANGE MID-
LATE AFTERNOON. MID LEVEL LAPSE RATES ARE ALSO EXPECTED TO REMAIN
ON THE LESS THAN IMPRESSIVE SIDE TODAY...BUT AS MENTIONED IN
SWODY1 AND AS WAS THE CASE YESTERDAY...LOCAL WATER-LOADING WITH
STRONGER CONVECTIVE CORES COULD RESULT IN ISOLATED
BRIEF...PRIMARILY SUB-SEVERE WIND GUSTS OF 40 TO 50 MPH ALONG
WITH ISOLATED HEAVY DOWNPOURS.

FOR TONIGHT...UPPER VORT MAX WILL BE SLOW TO TRACK THROUGH THE
REGION AND DID ADD SOME CHANCE POPS THROUGH THE EARLY PORTIONS OF
THE OVERNIGHT HOURS WITH SOME THREAT FOR ISOLATED HEAVIER DOWNPOURS
PERSISTING INTO THIS EVENING. WEAK LOW LEVEL TROUGH AXIS SHOULD SAG
INTO NORTHEAST HALF OF THE AREA LATE TONIGHT...AND COULD BE FOCUS
FOR SOME FOG FORMATION LATE TONIGHT INTO EARLY FRIDAY MORNING.

&&

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 347 AM EDT THU SEP 3 2015

AMPLIFIED MID-UPPER LEVEL RIDGE AXIS FROM THE SOUTHERN PLAINS
NORTHEAST INTO THE EASTERN US/SE CANADA WILL LEAD TO MORE
UNSEASONABLE WARMTH/HUMIDITY FRIDAY INTO THE HOLIDAY WEEKEND. NON-
ZERO CHANCES FOR ISO-SCT STORMS EXIST BOTH FRIDAY AND SATURDAY AS
BUILDING HEIGHTS INTO THE NORTHERN LAKES/SE CANADA BLOCK WEAKNESS IN
HEIGHT FIELD AND DIFFUSE SFC TROUGH OVER THE LOCAL AREA. ASSOCIATED
SUBTLE 700-500H COOL POOL OVER MOIST LOW LEVELS SHOULD PROMOTE A LOW
TO MODERATELY UNSTABLE (AND WEAKLY CAPPED) ENVIRONMENT BY EACH
AFTERNOON...ALTHOUGH EXPECT ANY MAINLY AFTERNOON/EARLY EVENING
CONVECTION TO BE HIT AND MISS (MORE MISS) GIVEN OVERALL WEAK
FORCING. OTHERWISE...RETAINED A DRY/HOT FCST INTO SUNDAY-SUNDAY
NIGHT AS FORECAST MODELS FINALLY SHIFT THIS FEATURE SSW OF THE
REGION.

THE EARLY TO MIDDLE PORTION OF THE NEXT WEEK WILL FEATURE A GRADUAL
BREAKDOWN OF RIDGE AXIS AND FRONTAL PASSAGE WITH 00Z GUIDANCE
OVERALL TRENDING SLOWER WITH COOLDOWN. LEAD/VIGOROUS SHORTWAVE
LIFTOUT INTO SOUTH-CENTRAL CANADA WILL ATTEMPT TO FORCE THIS
SLOWING/WEAKENING COLD FRONT (OR PRE-FRONTAL CONVECTIVE OUTFLOW)
INTO THE AREA BY LATER MONDAY/EARLY TUESDAY PER LAST SEVERAL MODEL
CYCLES. NOT ALL THAT EXCITED ABOUT CONVECTIVE CHANCES INITIALLY AS
ANY MID LEVEL SUPPORT BYPASSES WELL NW AND CAPPING INCREASES WITHIN
PRE-FRONTAL THERMAL WEDGE. HIGHER POPS AND EVENTUALLY SOME COOLER
WEATHER ARRIVES BY THE MIDDLE OF NEXT WEEK (MODELS ALL OVER THE
PLACE REGARDING TIMING AT THIS RANGE) AS HEIGHT FALLS AND A
SECONDARY SHORTWAVE EVENTUALLY OVERSPREAD NEARLY STALLED FRONTAL
BOUNDARY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 543 AM EDT THU SEP 3 2015

ISOLATED SHOWERS ASSOCIATED WITH LEAD SHORT WAVE TROUGH HAVE
DISSIPATED ACROSS NORTHEAST ILLINOIS. AS THIS FEATURE CONTINUES
ACROSS NORTHEAST INDIANA THROUGH 14Z...AN ISOLATED SHOWER IS
POSSIBLE BUT WILL CONTINUE WITH A DRY FORECAST AT BOTH KFWA AND
KSBN THIS MORNING WITH LIMITED INSTABILITY. A SECOND AND SLIGHTLY
MORE PRONOUNCED SHORT WAVE ACROSS EAST CENTRAL WISCONSIN/CENTRAL
LAKE MICHIGAN WILL DROP SOUTHEAST TODAY...AND WILL COMBINE WITH
DAYTIME INSTABILITY FOR ISOLATED-SCATTERED SHOWER THUNDERSTORM
DEVELOPMENT ACROSS NORTHERN INDIANA FROM MID-LATE AFTERNOON
INTO EARLY EVENING. SOME QUESTION REMAINS AS TO HOW FAR SOUTH
THIS WAVE WILL DIG...WITH GREATER PROBABILITIES OF STORMS POSSIBLY
REMAINING ACROSS EXTREME NORTHEAST INDIANA. GIVEN THIS SOMEWHAT
LOW CONFIDENCE...WILL CONFINE THUNDER MENTION TO VCTS DURING THE
MID AFTERNONOON-EARLY EVENING HOURS. WILL ALSO HAVE TO MONITOR AN
OUTFLOW BOUNDARY DROPPING SOUTHWARD ACROSS SOUTHEAST WISCONSIN
EARLY THIS MORNING AS A POSSIBLE FOCUS FOR LATE MORNING/EARLY
AFTERNOON ISOLATED SHOWER/STORM DEVELOPMENT. OTHERWISE SOUTHWEST
WINDS TODAY OF 5 TO 10 KNOTS TO BECOME LIGHT TONIGHT...WITH SOME
FOG POTENTIAL TOWARD THE END OF THE PERIOD AS WEAK LOW LEVEL
TROUGH AXIS SETTLES ACROSS NORTHERN INDIANA.

&&

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

$$

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


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