Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 250542
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
142 AM EDT MON AUG 25 2014

.SYNOPSIS...
ISSUED AT 339 PM EDT SUN AUG 24 2014

AN UPPER LEVEL RIDGE WILL PROVIDE DRY CONDITIONS TO THE REGION
TONIGHT. WARM AND HUMID AIR WILL BE DRAWN NORTHWARD ACROSS THE
REGION TONIGHT INTO MONDAY IN ADVANCE OF AN UPPER LEVEL
DISTURBANCE TRACKING OUT OF THE PLAINS. AN ISOLATED SHOWER OR
THUNDERSTORM IS POSSIBLE ON MONDAY...BUT A FRONTAL BOUNDARY
ASSOCIATED WITH THIS DISTURBANCE WILL INCREASE THE CHANCE OF
SHOWERS AND THUNDERSTORMS BY TUESDAY. LOW TEMPERATURES TONIGHT
WILL DROP INTO THE MID AND UPPER 60S. HIGH TEMPERATURES ON MONDAY
WILL RANGE FROM THE MID 80S IN CENTRAL LOWER MICHIGAN...TO THE
LOWER 90S ACROSS NORTHEAST ILLINOIS.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 339 PM EDT SUN AUG 24 2014

MID/UPPER LEVEL RIDGING TO PERSIST ACROSS THE REGION TONIGHT...WITH
PRIMARY SHORT WAVE TRACK FROM THE NORTHERN/CENTRAL PLAINS INTO
THE WESTERN/NORTHERN GREAT LAKES. AS HAS BEEN THE CASE OVER THE
PAST FEW DAYS...EASTERLY FLOW REGIME HAS BEEN CONDUCIVE FOR NARROW
ZONES OF WEAK CONVERGENCE...THE MOST DISTINCT THIS AFTERNOON
ROUGHLY FROM KEKM TO JUST NORTH OF KAOH. THE MOST UNSTABLE
CONDITIONS ARE ACROSS THE SOUTHWEST PORTIONS OF THE CWA. LITTLE IN
THE WAY OF ANY SYNOPTIC FORCING FOR VERTICAL MOTION NOTED THIS
AFTERNOON DUE TO PERSISTENCE OF UPPER RIDGING...ALTHOUGH AN
ISOLATED SHOWER OR STORM MAY TRY TO DEVELOP ALONG THE
AFOREMENTIONED CONVERGENCE ZONE WHERE SOME SLIGHTLY BETTER GROWTH
HAS BEEN NOTED IN AFTERNOON CU FIELD. CONFIDENCE IN OCCURRENCE AND
EXPECTED VERY LIMITED COVERAGE TO ANY CONVECTIVE DEVELOPMENT
PRECLUDES ANY ZFP MENTION. A SIMILAR SETUP IN STAGNANT PATTERN
TONIGHT SHOULD YIELD SOME PATCHY FOG AND STRATUS THROUGH EARLY
MONDAY MORNING.

UPPER LEVEL LOW CENTERED ACROSS THE NORTHERN HIGH PLAINS WILL LIFT
NORTHEAST INTO ONTARIO BY MONDAY EVENING. AN AXIS OF STRONGER
SOUTHWESTERLY LOW LEVEL FLOW WILL ALLOW FOR STRONG MOISTURE
TRANSPORT FROM THE MID MS VALLEY INTO THE NORTHERN GREAT LAKES
TONIGHT WHERE BEST CHANCES OF SHOWERS AND THUNDERSTORMS WILL RESIDE.
EVOLUTION OF THIS PATTERN WILL ALLOW FOR SLIGHT DEAMPLIFICATION OF
UPPER RIDGING ACROSS THE GREAT LAKES...AND NOT COMPLETELY OUT OF THE
QUESTION A REMNANT CONVECTIVE VORT COULD DROP SOUTHEAST INTO THE
SOUTHERN GREAT LAKES DURING THE DAY MONDAY. LOW LEVEL ANTICYCLONE
SHIFTING SOUTHEAST ACROSS THE MID ATLANTIC STATES SHOULD ALLOW FOR
SOME LOW LEVEL VEERING AND WARM/MOIST ADVECTION BACK INTO LOCAL
AREA...SETTING UP VERY UNSTABLE CONDITIONS FOR MONDAY. OUTSIDE OF
REMNANT FORCING FROM UPSTREAM CONVECTION TO THE NORTHWEST...NOT
MUCH TO KEY IN ON FOR FORCING MONDAY. HOWEVER...GIVEN SLIGHTLY
SUPPRESSED NATURE OF UPPER RIDGE...AND VERY UNSTABLE
CONDITIONS...DID INCLUDE SOME SLIGHT CHANCE TSRA POPS ACROSS
MAINLY NORTHERN HALF INTO EASTERN PORTIONS OF FORECAST AREA FOR
MONDAY.

WITH THE RETURN WARM/MOIST ADVECTION TONIGHT INTO EARLY
MONDAY...SFC DEW POINTS SHOULD CREEP BACK INTO THE LOWER TO MID 70S
WHICH WOULD YIELD PEAK AFTERNOON HEAT INDICES FROM THE MID TO
UPPER 90S WEST...TO THE LOWER 90S EAST ON MONDAY. AREAS ACROSS
THE FAR WEST/SOUTHWEST COULD CREEP CLOSE TO HEAT ADVISORY
CRITERIA...BUT GIVEN MARGINAL NATURE AND STILL SOME QUESTIONS
SURROUNDING LOW STRATUS/HIGH CLOUD EVOLUTION TONIGHT INTO EARLY
MONDAY...WILL HOLD OFF FOR NOW.

&&

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 339 PM EDT SUN AUG 24 2014

A RIDGE FLATTENING SHORTWAVE TROUGH PROPAGATING NORTHEAST INTO
ONTARIO/WESTERN QUEBEC TO START THE PERIOD WILL HELP FORCE A WEAK
FRONTAL BOUNDARY SOUTH INTO THE AREA BY LATER TUESDAY-WEDNESDAY.
MOIST/UNSTABLE ENVIRONMENT ALONG/SOUTH OF BOUNDARY SUPPORT GOING
CHANCE POPS FOR CONVECTION...ALTHOUGH FORCING MAY NOT BE STRONG
ENOUGH ON TUESDAY TO OVERCOME CAPPING INVERSION WITH THE LOCAL AREA
DISPLACED SOUTH OF STRONGER/MORE PERTURBED WESTERLY FLOW. IF/WHERE
CONVECTION FIRES HEAVY RAIN WILL LIKELY BECOME THE PRIMARY CONCERN
GIVEN WEAK FLOW AND ~2" PWAT POOLING INVOF BOUNDARY.

00/12Z MODEL ITERATIONS OVERALL TRENDED TOWARD A DRIER SOLUTION
LATER WEDNESDAY INTO THURSDAY...ESPECIALLY ALONG/NORTH OF HWY
30...WITH MORE PRONOUNCED NORTHEAST CONUS UPPER TROUGHING ALLOWING A
LOW LEVEL ANTICYCLONE TO BUILD INTO THE GREAT LAKES REGION. THIS
WOULD HELP STALL THE EASTWARD PROGRESSION OF A ROCKIES SHORTWAVE AND
PUSH THE ACTIVE INSTABILITY GRADIENT SOUTH OF THE IWX CWA. GIVEN
THESE TRENDS OPTED TO LOWER POPS...WITH A COUPLE DAYS OF COOLER/LESS
HUMID WEATHER POSSIBLE. LITTLE TO NO CHANGE FRIDAY AND BEYOND AS
GUIDANCE CONTINUE TO STRUGGLE WITH TIMING/SPEED OF A LONGER
WAVELENGTH TROUGH MODELED TO PROPAGATE EAST THROUGH THE
MIDWEST/GREAT LAKES.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 136 AM EDT MON AUG 25 2014

MOST IF NOT ALL THE TAF PERIOD WITH 2 AREAS OF CONCERN TO WATCH.
1ST WILL BE PRIOR TO 12Z WITH PATCHES OF STRATUS AND MVFR FOG
POSSIBLE AT BOTH SITES. JUST ENOUGH FLOW AND TEMPS A FEW DEGREES
WARMER THAN LAST NIGHT SHOULD KEEP THICKER CLOUDS AND FOG AT BAY.

VFR CONDITIONS SHOULD EXIST ACROSS THE AREA BETWEEN 12 AND 18Z
WITH CIRRUS MOVING IN FROM UPSTREAM CONVECTION. THE REMNANTS OF
THIS CONVECTION COULD CAUSE SOME FLIGHT ISSUES...MAINLY AT KSBN
AROUND OR AFTER 18Z. AT THIS POINT COVERAGE AND EXACT TIMING IS
UNCLEAR RESULTING IN LEAVING OUT OF TAFS AND HANDLING WITH THIS
MENTION FOR NOW.

&&

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

$$

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


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