Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 261427
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1030 AM EDT TUE APR 26 2016

.UPDATE...
AVIATION SECTION HAS BEEN UPDATED BELOW.

&&

.SYNOPSIS...
ISSUED AT 339 AM EDT TUE APR 26 2016

AN UNSETTLED WEATHER PATTERN WITH THE POTENTIAL FOR SHOWERS AND
THUNDERSTORMS WILL CONTINUE THROUGH THURSDAY AS A FRONTAL BOUNDARY
OSCILLATES ACROSS THE OHIO VALLEY. AFTER A BRIEF PERIOD OF DRY
WEATHER TO END THE WEEK...WETTER CONDITIONS WILL RETURN FOR THE
WEEKEND AS LOW PRESSURE TRACKS THROUGH THE REGION. AN UPPER LOW WILL
MOVE INTO THE GREAT LAKES EARLY NEXT WEEK...BRINGING COOL WET
WEATHER TO CENTRAL INDIANA.

&&

.NEAR TERM /TODAY/...
ISSUED AT 339 AM EDT TUE APR 26 2016

PARTLY CLOUDY SKIES AND BREEZY CONDITIONS ONGOING EARLY THIS MORNING
WITH SOUTHWEST WINDS REMAINING AT A STEADY 10-20MPH AS LOW PRESSURE
TRACKS THROUGH THE LOWER GREAT LAKES. MOST OF THE CONVECTION IS IN
CLOSEST PROXIMITY TO THE LOW...EXTENDING ACROSS THE EASTERN GREAT
LAKES BACK INTO NORTHEAST INDIANA. WITH WELL MIXED AIR IN THE
BOUNDARY LAYER...TEMPS HAVE NOT MOVED MUCH SO FAR DURING THE
OVERNIGHT...WITH 07Z TEMPS GENERALLY IN THE MID AND UPPER 60S.

PRIMARY FOCUS FOR TODAY IS ON THE POTENTIAL FOR REDEVELOPING
CONVECTION WHILE SIFTING THROUGH THE MODEL SUITE WHICH CONTINUES TO
CARRY POOR RUN TO RUN CONTINUITY. HAVE LEANED MUCH CLOSER TO THE HI-
RES GUIDANCE /HRRR-WRF-4KM NAM/ FOR TIMING CONVECTIVE DEVELOPMENT
AND LOCATION OF GREATEST COVERAGE LATER TODAY.

COLD FRONT EXTENDS W/SW ACROSS NW INDIANA AND NORTH CENTRAL ILLINOIS
FROM THE SURFACE LOW CURRENTLY OVER SOUTHEAST MICHIGAN. MOST OF THE
FORCING ALOFT IS IN THE VICINITY OF THE SURFACE WAVE WITH THE LOW
LEVEL JET ALREADY DEPARTING INTO THE EASTERN GREAT LAKES. THIS HAS
RESULTED IN CONVECTION REMAINING ISOLATED AT BEST WITH LITTLE TO
FIRE OFF OF BACK TO THE NORTHWEST OF THE AREA SO FAR THIS MORNING.
FURTHERMORE...MODELS HAVE NOT HANDLED THE PRESENCE OF THE DRIER
AIRMASS OVER CENTRAL INDIANA WELL AT ALL...CONSISTENTLY TRYING TO
ADVECT LOW LEVEL MOISTURE INTO THE REGION FASTER THAN WHAT IS
ACTUALLY OCCURRING. MESOANALYSIS SHOWS THIS VERY CLEARLY WITH A
BORDERLINE HOSTILE ENVIRONMENT PRESENT OVER THE FORECAST AREA
HIGHLIGHTED BY DEWPOINTS PRIMARILY IN THE LOWER/MID 50S AND AN
ABUNDANCE OF CONVECTIVE INHIBITION. AS A RESULT...EVEN SHOWERS HAVE
HAD A DIFFICULT TIME MAKING IT INTO THE REGION SO FAR EARLY THIS
MORNING.

WHILE CONVECTIVE INHIBITION WILL SLOWLY DIMINISH THROUGH THE MORNING
AS MOISTURE SLOWLY INCREASES...HAVE A HARD TIME JUSTIFYING ANY
HIGHER THAN A 20 POP WITH RIDGING ALOFT DEVELOPING. THE PRESENCE OF
THE FRONTAL BOUNDARY SLIPPING SOUTH INTO THE NORTHERN HALF OF THE
FORECAST AREA BY LATE MORNING REALLY IS THE ONLY FEATURE LIKELY TO
PRODUCE ANYTHING OF SUBSTANCE THROUGH MIDDAY.

AS THE FRONT SHIFTS INTO THE SOUTHERN HALF OF THE FORECAST AREA THIS
AFTERNOON HOWEVER...THE SETUP WILL BECOME MUCH MORE CONDUCIVE FOR
THUNDERSTORMS AS MOISTURE POOLS ALONG THE BOUNDARY AND THE AIRMASS
BECOMES MODESTLY UNSTABLE WITH STEEPENING LAPSE RATES. A WAVE ALOFT
THAT IS CURRENTLY GENERATING INITIAL CONVECTIVE DEVELOPMENT IN THE
MISSOURI VALLEY EARLY THIS MORNING WILL ROUND THE UPPER RIDGE AND
SWING INTO THE REGION BY LATE AFTERNOON. THIS FEATURE WILL ADD SOME
FORCING FOR MORE ORGANIZED CONVECTIVE DEVELOPMENT WITH BULK OF THE
HI-RES GUIDANCE ALL CAPTURING AREAS OF THUNDERSTORMS DEVELOPING AND
BECOMING MOST NUMEROUS ALONG AND SOUTH OF I-70. WILL CONTINUE WITH
HIGHEST POPS IN THESE AREAS...TAPERING OFF QUICKLY OVER NORTHERN
COUNTIES AS DRIER AIR FILTERS IN NORTH OF THE FRONT. LACK OF MORE
APPRECIABLE BL SHEAR AND UNIMPRESSIVE BOUNDARY LAYER FLOW SUPPORT
MORE OF A MULTICELLULAR MODE TO STORMS WITH PULSING INTENSITY. COULD
SEE STRONGER STORMS PRODUCE HAIL AND BRIEF WIND GUSTS BUT OVERALL
EXPECT STORMS TO REMAIN SUBSEVERE INTO THE EVENING.

TEMPS...CONSIDERING THE WARMER START THIS MORNING WHICH MOST OF THE
MODELS HAVE MISSED...AND THE POTENTIAL FOR SUN AND QUICK HEATING
THROUGH THE FIRST HALF OF THE DAY...TRENDED HIGH TEMPS TOWARDS
HRRR/4KM NAM WHICH PLACE MOST AREAS AT OR A COUPLE DEGREES WARMER
THAN MOS. EXPECT MID 70S NORTH TO LOWER 80S SOUTH.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...
ISSUED AT 339 AM EDT TUE APR 26 2016

FORECAST CHALLENGES FOCUS ON PRECIP CHANCES THROUGH MUCH OF THE
PERIOD...AND POTENTIAL IMPACTS TO TEMPS AS LOCATION OF THE
OSCILLATING FRONTAL BOUNDARY WILL CREATE SHARP GRADIENTS FROM NORTH
TO SOUTH ACROSS THE FORECAST AREA AT TIMES.

CONVECTION LIKELY TO BE ONGOING AT 00Z THIS EVENING NEAR THE FRONTAL
BOUNDARY OVER THE SOUTHERN HALF OF THE FORECAST AREA. THE BOUNDARY
WILL CONTINUE TO PRESS INTO FAR SOUTHERN INDIANA LATE TONIGHT AIDED
BY BROAD HIGH PRESSURE OVER THE NORTHERN GREAT LAKES. ANY SCATTERED
CONVECTION WILL SHIFT TO THE LOWER WABASH VALLEY AND PERHAPS FAR
SOUTHERN ROW OF COUNTIES AFTER MIDNIGHT AS E/NE FLOW BRINGS DRIER
AIR BACK SOUTH INTO MUCH OF THE REGION. SHALLOW LAYER OF COOLER AIR
IN THE NEAR SURFACE LAYER WILL LEAD TO A SHARP INVERSION DEVELOPING
LATE TONIGHT AND CONTINUING INTO WEDNESDAY MORNING. THIS WILL LIKELY
MANIFEST AS A THICK LAYER OF STRATUS AND WILL CONTINUE WITH MOSTLY
CLOUDY SKIES ACROSS MUCH OF THE AREA.

FOCUS WILL SHIFT TO THE DEEP UPPER LOW AND ATTENDANT SURFACE WAVE
LIFTING NORTH THROUGH THE CENTRAL PLAINS WEDNESDAY MORNING. THIS
WILL PROMPT THE BOUNDARY TO LIFT BACK NORTH AS A WARM FRONT WHILE
THE LOW PRESSURE OCCLUDES OVER THE MISSOURI VALLEY. THESE FEATURES
WILL BE THE PRIMARY CATALYSTS IN THE POTENTIAL SIGNIFICANT SEVERE
WEATHER EXPECTED LATE TODAY AND TONIGHT OVER THE CENTRAL AND
SOUTHERN PLAINS. THAT ACTIVITY IS LIKELY TO COALESCE INTO A LINE OR
LINES OF WEAKER CONVECTION OVERNIGHT INTO WEDNESDAY MORNING AS IT
PRESSES EAST INTO THE MID MISSISSIPPI VALLEY AND LOWER OHIO VALLEY.

REMNANTS FROM THESE STORMS WILL GET DRAWN INTO THE REGION BY
WEDNESDAY AFTERNOON AS THE WARM FRONT LIFTS NORTH...AND MAY EVEN SEE
SOME RESTRENGTHENING OF STORMS LATE DAY IN THE LOWER WABASH VALLEY
WHERE ACTIVITY HAS BEST CHANCE TO BECOME SURFACE BASED IN THE WARM
SECTOR. NICE DIFFLUENCE ALOFT WILL HELP TO ENHANCE CONVECTIVE
COVERAGE WITH RAIN AND STORMS BECOMING WIDESPREAD FROM LATE
AFTERNOON INTO WEDNESDAY NIGHT. WILL CONTINUE WITH HIGH POPS ACROSS
THE FORECAST AREA AS A RESULT.

THE OCCLUDING SURFACE LOW WILL KICK OUT INTO THE REGION THURSDAY AS
THE UPPER LOW OPENS UP AND TRACKS INTO THE GREAT LAKES. DEEPER
MOISTURE AND BETTER FORCING SUPPORTS CARRYING BEST CHANCE POPS
ACROSS THE NORTHEAST HALF OF THE FORECAST AREA THURSDAY. SCATTERED
SHOWERS WILL GRADUALLY END THURSDAY EVENING AS THE LOW MOVES AWAY TO
THE EAST AND UPPER RIDGING QUICKLY EXPANDS INTO THE OHIO VALLEY.

TEMPS...WITH THE FRONT IN SOUTHERN COUNTIES WEDNESDAY...EXPECT A
FAIRLY SHARP TEMP GRADIENT FROM THE LOWER 60S IN THE NORTHEAST TO
THE MID 70S IN THE LOWER WABASH VALLEY. WARMER TEMPS EXPECTED
THURSDAY AND FAR SOUTHERN COUNTIES MAY MAKE A RUN AT 80 DEGREES WITH
MORE SUNSHINE AND ONLY WIDELY SCATTERED CONVECTION ANTICIPATED. AN
OVERALL MODEL BLEND CAPTURED THIS THINKING WELL. GENERALLY TRENDED
TOWARDS WARMER MAVMOS FOR LOWS THROUGH THE PERIOD.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
ISSUED AT 242 AM EDT TUE APR 26 2016

MODELS ARE CLOSE ENOUGH THAT THE SUPERBLEND INITIALIZATION WAS
ACCEPTED FOR MOST ITEMS.

AN UPPER LEVEL LOW INITIALLY OVER THE WESTERN HALF OF THE COUNTRY
WILL WORK SLOWLY EAST INTO THE REGION THROUGH THE LONG TERM. THIS
WILL ALSO BRING A SURFACE LOW PRESSURE SYSTEM WITH IT. THE RESULT OF
THIS SETUP WILL BE FREQUENT CHANCES FOR RAIN THROUGH THE LONG TERM.

GFS IS FASTER THAN ECMWF/CANADIAN IN BRINGING A RETURN OF RAIN
FRIDAY NIGHT. STUCK WITH THE CONSENSUS OF THE ECMWF/CANADIAN AND CUT
BACK SUPERBLEND/S POPS FRIDAY NIGHT. THIS IS CLOSE TO THE PREVIOUS
FORECAST AND THUS AVOIDS POTENTIAL FLIP-FLOPPING.

TEMPERATURES WILL START OUT NEAR AVERAGE...BUT WILL END UP COOLING
TO BELOW AVERAGE LATE IN THE PERIOD AS THE UPPER LOW MOVES IN.

&&


.AVIATION /DISCUSSION FOR THE 261500Z KIND TAF UPDATE/...
ISSUED AT 1030 AM EDT TUE APR 26 2016

MINOR TWEAKS MADE TO KIND TAF TO BETTER MATCH CURRENT CONDITIONS.
NO OTHER CHANGES ARE NEEDED AT THIS TIME.

PREVIOUS AVIATION DISCUSSION FOLLOWS...
VFR CONDITIONS EXPECTED OUTSIDE OF CONVECTION DURING THE DAY...THEN
MVFR DEVELOPING OVERNIGHT. MVFR OR WORSE IN CONVECTION...ESPECIALLY
LATE THIS AFTERNOON.

ISOLATED SHOWERS AND THUNDERSTORMS MAY BE AROUND THE AREA DURING THE
FIRST FEW HOURS OF THE TAF PERIOD...BUT COVERAGE NOT EXPECTED TO BE
ENOUGH TO MENTION IN TAFS. FOR ALL BUT KLAF...WENT VCSH AT 17Z TO
INDICATE INCREASING COVERAGE...THEN WENT TEMPO IN THE 20-24Z TIME
FRAME AS AN UPPER WAVE SHOULD GENERATE MORE WIDESPREAD CONVECTION.
COVERAGE OF CONVECTION NEAR KLAF SHOULD BE LOW ENOUGH NOT TO MENTION.

CONVECTION SHOULD DIMINISH THIS EVENING AS THE UPPER WAVE MOVES OFF.
MVFR CEILINGS THEN SHOULD DEVELOP OVERNIGHT. WINDS WILL BECOME
NORTHWEST DURING THE DAY THEN NORTHEAST OVERNIGHT.

&&

.IND WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SYNOPSIS...RYAN
NEAR TERM...RYAN
SHORT TERM...RYAN
LONG TERM....50
AVIATION...50/JH



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