Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 010557
AFDIWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
157 AM EDT SUN MAY 1 2016

.SYNOPSIS...
ISSUED AT 720 PM EDT SAT APR 30 2016

OCCASIONAL RAIN IS EXPECTED ACROSS THE AREA TONIGHT. LOWS WILL
RANGE FROM THE MID 40S IN SOUTH CENTRAL MICHIGAN TO THE MID 50S IN
CENTRAL INDIANA. THERE IS A CHANCE OF SHOWERS AND THUNDERSTORMS
SUNDAY... MAINLY IN THE AFTERNOON. HIGHS WILL BE IN THE UPPER 50S
TO UPPER 60S.

&&

.UPDATE...
ISSUED AT 1137 PM EDT SAT APR 30 2016

FORECAST UPDATED TO CLEAR OUT THE MAIN AREA OF RAIN A TOUCH
FASTER. STEADIER RAIN HAS SHIFTED AWAY WITH MORE OF A CONVECTIVE
NATURE TO RECENT RETURNS (EVEN 1 LIGHTNING STRIKE NE OF DECATUR IN
ABOUT 5 MINUTES AGO). ADDITIONAL SHOWERS/ISOL STORMS WERE WORKING
NORTH OF I-70 ALONG A SLOWLY ADVANCING WARM FRONT. WILL KEEP CHC
POPS GOING THROUGH 6Z TO HANDLE ANY POP UP SHOWERS THAT MAY OCCUR.
AFTER 6Z...FOG/DRIZZLE TO COME INTO PLAY WITH FRONT TO THE SOUTH
AND OVERRUNNING SETUP PLUS WEAK LIFT IN LOWER LEVELS. A FEW OF THE
HI RES MODELS SHOW SHOWER ACTIVITY MAY PERSIST AND EVEN INCREASE
SOMEWHAT BUT FOR NOW WILL MONITOR TRENDS.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 428 PM EDT SAT APR 30 2016

DEEP MOISTURE FIELD ALONG WITH COGENT I300K ISENTROPIC LIFT
LENDING WIDESPREAD RAINFALL COVERAGE THIS EVENING THROUGHOUT CWA.
BACK EDGE OF PRECIP SHIELD OR AT LEAST TRANSITION TO LIGHTER/MORE
SPOTTY RAINFALL TO THEN ENTER SWRN CWA THIS EVE/LIFTING NEWD AS
DRY SLOT PUNCHES INTO SWRN UPR GREAT LAKES AND ISENT UVM
DIMINISHES CONSIDERABLY WITH BEST AXIS LIFTING NWD THROUGH MI.
WHILE CWA REMAINS LARGELY ON COLD SIDE OF FRONTAL OCCLUSION AS YET
ANOTHER SLOWLY FILLING MID LEVEL SYSTEM SLOWLY LIFTS/FILLS FROM
CNTL PLAINS INTO THE SWRN UPR GRTLKS...DID RAISE TEMPS SLIGHTLY
OVERNIGHT WITH THICK IFR STRATUS DECK TO CAP RADIATIVE EFFECTS AND
AT MINIMUM COLD LAYER BECOMES MORE SHALLOW/ESPCLY ACRS SRN CWA.
THIS AREA WILL BODE BEST POTENTIAL FOR MIDDAY/AFTERNOON CONVECTION
ON SUNDAY. STILL SUSPECT DESTABILIZATION QUITE CONDITIONAL AND
CERTAINTY FOR TSRA NOT ESPECIALLY HIGH. AFFORDED SOME
TEMPORAL/SPATIAL DELINEATION WRT TSRA CHANCES...WITH HIEST CHANCES
21-24 UTC SUN OVER SERN QUARTER CWA.

&&

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 428 PM EDT SAT APR 30 2016

MAIN UPPER LOW ACROSS THE CENTRAL PLAINS THIS AFTERNOON WILL
FINALLY OPEN/SHEAR EAST THROUGH THE AREA SUNDAY EVENING. LAST
SEVERAL MODEL ITERATIONS HAVE TRENDED LESS SHEARED WITH MORE
FOCUSED ASCENT DURING THIS TIME. AS A RESULT BUMPED POPS UP SUNDAY
EVENING WITH SCT-NUM SHOWERS ANTICIPATED ALONG SE SINKING LOW
LEVEL BAROCLINIC ZONE/DEFORMATION AXIS. ENOUGH DRY AIR SHOULD
SNEAK IN BEHIND THIS SYSTEM TO FOCUS THE NEXT ROUND OF PCPN SOUTH
AS NEXT SHORTWAVE NOW OVER ARIZONA SHEARS QUICKLY ENE THROUGH THE
OH/TN VALLEYS. WITH THAT SAID THERE COULD BE JUST ENOUGH OF A MID
LVL FGEN/PVA RESPONSE TO GENERATE A FEW LIGHT
SHOWERS/SPRINKLES...BUT OPTED TO RETAIN OPTIMISTIC (MAINLY
DRY...10-20 POPS) FOR NOW. OTHERWISE...MAINLY CLOUDY/COOL
CONDITIONS PERSIST INTO MONDAY.

BLOCKY PATTERN WILL LIKELY PERSIST MID-LATE WEEK AS CUT-OFF UPPER
LOWS EVENTUALLY EMERGES OVER THE EASTERN US AND SOUTHWEST US...WITH
AMPLIFIED UPPER RIDGING IN BETWEEN ACROSS HIGH PLAINS/CANADIAN
PRAIRIES. SHOWER CHANCES WILL ACCOMPANY A COLD FRONTAL PASSAGE ON
WEDNESDAY IN THIS TRANSITION AS NEGATIVE HEIGHT ANOMALY DROPS SOUTH
FROM THE ARCTIC CIRCLE. COULD EVEN SEE ADDITIONAL SHOWER DEVELOPMENT
INTO THURSDAY/FRIDAY ON WESTERN FRINGE OF CIRCULATION. AS FOR
TEMPS...TUESDAY LOOKING LIKE THE WARMEST DAY AS LOW LEVEL THERMAL
RIDGING SLIDES IN PRE-FRONTAL...WITH BELOW NORMAL TEMPS RETURNING
THEREAFTER.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 136 AM EDT SUN MAY 1 2016

LEAD SHORT WAVE AND STRONGER ISENTROPIC ADVECTION SURGE ARE
DEPARTING NORTHERN INDIANA EARLY THIS MORNING. WEAK WARM ADVECTION
WILL CONTINUE OVERNIGHT IN ADVANCE OF NEXT UPPER LEVEL LOW
APPROACHING FROM THE WEST FOR LATER THIS AFTERNOON WHICH SHOULD
RESULT IN CONTINUED DRIZZLE/PATCHY LIGHT RAIN THROUGH THE
REMAINDER OF THE EARLY MORNING. EASTERLY FLOW NORTH OF SFC FRONT
AND A STRONG LOW LEVEL INVERSION WILL SUPPORT CONTINUED IFR/LIFR
CONDITIONS THROUGH MID MORNING...AND POSSIBLY AS LATE AS THE
16-17Z TIMEFRAME AT KSBN. SOME IMPROVEMENTS TO MVFR EXPECTED LATE
MORNING/EARLY AFTERNOON WITH SOME DIURNAL MIXING AS SFC BOUNDARY
TO THE SOUTH MAY TRY TO MIX SLIGHTLY TO THE NORTH. SCATTERED-
NUMEROUS SHOWERS AND PERHAPS A FEW THUNDERSTORMS ARE EXPECTED TO
REDEVELOP LATE AFTERNOON INTO EARLY EVENING AS UPPER TROUGH
APPROACHES. INSTABILITY WILL BE SOMEWHAT LIMITED...AND AT THIS
FORECAST DISTANCE HAVE HELD OFF ON THUNDER INCLUSION...BUT BEST
CHANCE OF THUNDER LATE AFTERNOON/EARLY EVENING WOULD BE AT KFWA IN
CLOSER PROXIMITY TO PRIMARY WEAK INSTABILITY AXIS.

&&

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

$$

UPDATE...FISHER
SYNOPSIS...JT
SHORT TERM...MURPHY
LONG TERM...STEINWEDEL
AVIATION...MARSILI


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