Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 280724
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
324 AM EDT THU APR 28 2016

.UPDATE...
THE SYNOPSIS...NEAR TERM AND SHORT TERM SECTIONS HAVE BEEN UPDATED
BELOW.

&&

.SYNOPSIS...
ISSUED AT 323 AM EDT THU APR 28 2016

SCATTERED SHOWERS AND THUNDERSTORMS WILL REMAIN POSSIBLE TODAY AS A
FRONTAL BOUNDARY AND LOW PRESSURE MOVE THROUGH THE REGION. WEAK HIGH
PRESSURE WILL BRING A BRIEF RESPITE FROM THE UNSETTLED WEATHER FOR
FRIDAY...BUT WET CONDITIONS RETURN FOR MUCH OF THE WEEKEND AS LOW
PRESSURE TRACKS THROUGH THE OHIO VALLEY. DRY WEATHER WITH COOLER
THAN NORMAL TEMPERATURES ARE EXPECTED THROUGH MOST OF THE FIRST HALF
OF NEXT WEEK. A COLD FRONT WILL PROVIDE THE NEXT CHANCE FOR RAIN AND
STORMS NEXT WEDNESDAY.

&&

.NEAR TERM /TODAY/...
ISSUED AT 323 AM EDT THU APR 28 2016

SCATTERED CONVECTION CONTINUES TO TRACK ACROSS CENTRAL INDIANA EARLY
THIS MORNING WITH A MOIST AND MARGINALLY UNSTABLE ENVIRONMENT
PRESENT. A STRONGER CONVECTIVE LINE PRESENT ACROSS EASTERN ILLINOIS
IN CLOSER PROXIMITY TO THE OCCLUDED FRONTAL BOUNDARY. STILL QUITE
THE TEMP GRADIENT PRESENT FROM NORTH TO SOUTH...WITH 07Z TEMPS
RUNNING FROM THE MID 40S IN THE NORTH TO THE LOWER 60S OVER THE
LOWER WABASH VALLEY.

INITIAL ISSUE FOCUSES ON THE CONVECTIVE THREAT OVER THE NEXT 6 HOURS
OR SO AS THE OCCLUDED BOUNDARY PRESSES EAST INTO THE REGION BY
DAYBREAK. HI-RES GUIDANCE CAPTURING THE CONVECTION TO OUR WEST OVER
ILLINOIS THIS MORNING...BUT HRRR/WRF/4KM NAM ALL WEAKEN AND
VIRTUALLY DIMINISH THE STORMS AS THEY MOVE INTO THE FORECAST AREA
OVER THE NEXT 2-3 HOURS. CONVECTION BEING AIDED BY A THIN MLCAPE
AXIS WITH 500-1000 J/KG...AND ALL SIGNS ARE THAT SOME OF THE
INSTABILITY WILL TRANSITION INTO CENTRAL INDIANA THROUGH 10-11Z.
WHILE THE AIRMASS WILL BE LESS FAVORABLE FOR MORE INTENSE CONVECTION
ACROSS THE FORECAST AREA...HAVE A HARD TIME SEEING THE ACTIVITY
COMPLETELY DIMINISH. WILL MAINTAIN HIGHER POPS OVER THE NEXT FEW
HOURS...RAPIDLY DROPPING OFF TO LOW CHANCE BY 12Z AS BETTER FORCING
AND MOISTURE SHIFT NORTHEAST. MAIN IMPACTS FROM STORMS THROUGH THE
PREDAWN HOURS WILL BE LOCALLY HEAVY RAINFALL AND PERHAPS SMALL HAIL
FROM SOME OF THE STRONGER CELLS.

REMAINDER OF THE DAY PRESENTS SOME CHALLENGES AS THE REMNANT
OCCLUDED BOUNDARY EVENTUALLY ALIGNS WEST-EAST ACROSS THE NORTHERN
HALF OF THE FORECAST AREA WITH THE LEFTOVER AND MUCH WEAKER SURFACE
WAVE KICKING OUT INTO THE REGION. THE BOUNDARY AND SURFACE WAVE WILL
SERVE AS A SOURCE OF LIFT FOR ANY CONVECTION THAT CAN GET GOING
COURTESY OF DIURNAL HEATING...WITH DIFFLUENCE AND WEAK FORCING ALOFT
CONTRIBUTING AS WELL. MUCH OF CENTRAL INDIANA WILL SEE SUNSHINE AS
THE MORNING PROGRESSES...ESPECIALLY OVER SOUTHERN COUNTIES...AND
EXPECT AIRMASS TO BECOME MODESTLY UNSTABLE BY AFTERNOON. ALL OF
THESE FEATURES SUPPORT RENEWED CONVECTIVE DEVELOPMENT IN VICINITY OF
THE BOUNDARY THIS AFTERNOON.

HOWEVER...THE LACK OF MORE APPRECIABLE MOISTURE...LOW LEVEL FORCING
AND BL SHEAR WILL LIKELY KEEP CONVECTIVE COVERAGE TO SCATTERED AT
BEST. LACK OF SHEAR WILL ALSO LIMIT STORM INTENSITY WITH STRONGER
CELLS BRIEFLY PULSING UP WITHIN THE UNSTABLE AIRMASS. CANNOT RULE
OUT GUSTY WINDS WITHIN COLLAPSING STORM CORES OR HAIL AS WET BULB
ZERO LEVELS DROP TO NEAR 7KFT THIS AFTERNOON...BUT OVERALL EXPECT
STORMS TO REMAIN UNDER SEVERE LEVELS. WILL CARRY SCATTERED POPS THIS
AFTERNOON OVER THE NORTHERN 2/3 OF THE FORECAST AREA WITH LOWEST
POPS IN THE SOUTHWEST FURTHEST AWAY FROM THE BOUNDARY AND WITHIN A
PROGRESSIVELY DRIER AIRMASS.

TEMPS...AFTER A COOL WEDNESDAY...SUNSHINE AND SOUTHERLY FLOW FOR
MUCH OF THE AREA WILL ENABLE A NICE RECOVERY TODAY. NORTHERN
COUNTIES LIKELY REMAIN IN THE 60S NEAR/NORTH OF THE BOUNDARY...WITH
70S ELSEWHERE. TRENDED TOWARDS WARM END OF GUIDANCE FOR MOST...WHICH
ENDED UP CLOSE TO WRF/4KM NAM MODEL TEMPS.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...
ISSUED AT 323 AM EDT THU APR 28 2016

FORECAST CHALLENGES FOCUS ON PRECIP CHANCES RETURNING LATE FRIDAY
NIGHT INTO SATURDAY AS A NEW STORM SYSTEM IMPACTS THE OHIO VALLEY.

ISOLATED SHOWERS AND STORMS WILL LINGER OVER NORTHERN COUNTIES
THROUGH THE EVENING AS THE REMNANT SURFACE WAVE DEPARTS OFF TO THE
EAST. TAIL END OF THE BOUNDARY WILL HANG BACK AS WELL INTO THE
OVERNIGHT AND WITH WEAK FORCING ALOFT PERSISTING AS AN UPPER WAVE
TRACKS ACROSS THE GREAT LAKES...MAY SEE A FEW LIGHT SHOWERS IN THE
NORTH OVERNIGHT BEFORE ENDING.

WEAK SURFACE HIGH PRESSURE AND RIDGING ALOFT WILL BUILD IN EARLY
FRIDAY WITH A BRIEF PERIOD OF DRY WEATHER FOR THE OHIO VALLEY. MODEL
SOUNDINGS CONTINUE TO ADVERTISE A SHALLOW INVERSION DEVELOPING
DURING THE PREDAWN HOURS FRIDAY OVER THE NORTHERN HALF OF THE
FORECAST AREA LINGERING THROUGH THE MORNING. THIS WILL LIKELY
MANIFEST AS A LOW STRATUS DECK THAT WILL NOT MIX OUT UNTIL CLOSER TO
MIDDAY AS THE INVERSION WEAKENS. WILL START OUT THESE AREAS MOSTLY
CLOUDY...BUT EXPECT INCREASING SUNSHINE INTO THE AFTERNOON HOURS.

MID AND HIGH LEVEL CLOUDS WILL BE ON THE INCREASE BY LATE DAY IN
ADVANCE OF AN AREA OF LOW PRESSURE DEVELOPING OVER THE SOUTHERN
PLAINS. MODEL CONSENSUS HAS TRANSITIONED BACK TO A FASTER ARRIVAL OF
DEEPER MOISTURE INTO THE REGION AHEAD OF A FRONTAL BOUNDARY THAT
WILL ALIGN NEAR THE OHIO RIVER BY SATURDAY MORNING. AFTER A DRY
EVENING FRIDAY...ISENTROPIC LIFT WILL INCREASE QUICKLY AFTER 06Z
SATURDAY AS A 45KT 850MB LOW LEVEL JET NOSES INTO THE LOWER OHIO
VALLEY. SHOULD SEE SHOWERS EXPAND IN COVERAGE FROM THE SOUTHWEST IN
THE PREDAWN HOURS...ENCOMPASSING THE ENTIRE FORECAST AREA BY MID
MORNING AND MAKING FOR A VERY WET AND COOL SATURDAY. WILL INCREASE
POPS TO CATEGORICAL FOR SATURDAY AS THE WARM FRONT LIFTS NORTH INTO
THE REGION. EXPECT EMBEDDED THUNDER AS WELL WITH PLENTY OF ELEVATED
INSTABILITY. RAIN AND THUNDERSTORMS WILL CONTINUE SATURDAY NIGHT
WITH THE FRONT ACROSS CENTRAL INDIANA AND A SURFACE WAVE TRACKING
INTO THE REGION FROM THE WEST.

TEMPS...TRENDED TOWARDS THE WARMER MET GUIDANCE FOR HIGHS FRIDAY AS
TEMPS LIKELY TO RISE INTO THE MID AND UPPER 60S OVER MUCH OF THE
FORECAST AREA. WIDESPREAD RAIN AND A RAW EASTERLY FLOW NORTH OF THE
WARM FRONT SUPPORTS GOING COOLER FOR SATURDAY...AND HAVE DROPPED
HIGHS BACK INTO THE LOWER AND MID 60S. CERTAINLY PLAUSIBLE THAT MAY
NEED TO DROP TEMPS EVEN FURTHER AS THE SIGNS ARE THERE FOR TEMPS TO
REMAIN IN THE 50S...ESPECIALLY NORTH OF I-70. UTILIZED A MODEL
BLEND FOR LOWS THROUGH THE PERIOD.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
ISSUED AT 241 AM EDT THU APR 28 2016

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

ONE UPPER LOW WILL MOVE THROUGH THE AREA EARLY IN THE PERIOD KEEPING
THE CHANCES FOR RAIN IN THE FORECAST. AFTER A BRIEF BREAK
TUESDAY...AN UPPER TROUGH WILL DEEPEN ACROSS THE AREA AND ANOTHER
COLD FRONT WILL MOVE THROUGH MID-WEEK. THIS WILL BRING AN ADDITIONAL
CHANCE FOR RAIN.

TEMPERATURES WILL REMAIN NEAR TO BELOW AVERAGE THROUGH THE PERIOD.

THE MODELS HAVE BEEN STRUGGLING WITH THE DETAILS OF THIS SETUP WITH
EACH RUN...SO CONFIDENCE IS LOWER THAN AVERAGE...ESPECIALLY IN LATER
PERIODS.

&&

.AVIATION /DISCUSSION FOR THE 280600Z TAFS/...
ISSUED AT 1234 AM EDT THU APR 28 2016

SCATTERED SHOWERS/ISOLATED THUNDERSTORMS CONTINUE TO LINGER AHEAD OF A
VORTICITY LOBE MOVING THROUGH WESTERN ILLINOIS. APPEARS THERE WILL BE
SHOWER ACTIVITY IN THE VICINITY OF THE TERMINALS THROUGH ABOUT
280900Z AS THIS VORTICITY LOBE MOVES THROUGH. THERE ARE SOME
SCATTERED STORMS CURRENTLY MOVING TOWARD SOME SITES...BUT BY VALID
TIME PERHAPS ONLY KIND WILL SEE THUNDER. WILL WAIT UNTIL ISSUANCE
TIME FOR ANY BRIEF INCLUSION OF THUNDER.

OTHERWISE...CONTINUED WARM/MOIST ADVECTION OVER A FRONTAL ZONE TO
THE SOUTH SHOULD ALLOW FOR A GRADUAL INCREASE OF IFR CEILINGS DURING
THE COURSE OF THE NIGHT. SHOWER ACTIVITY MAY TEND TO KEEP WIDESPREAD
IFR CEILING FROM DEVELOPING UNTIL AFTER 280900Z. EXPECTING IFR
CEILINGS TO LINGER INTO THE MIDDAY HOURS OF THURSDAY...WITH CEILING
LIFTING ABOVE IFR BY THEN AS A COLD FRONT MOVES THROUGH.

SURFACE WINDS 090-120 DEGREES AT 7-10 KTS OVERNIGHT EXPECTED TO
DIMINISH WITH TIME AS THE FRONTAL ZONE APPROACHES. WINDS SHOULD
BECOME 240-270 DEGREES AT 8-11 KTS BY LATE MORNING THURSDAY WITH THE
PASSAGE OF A COLD FRONT.

&&

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

&&

$$

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


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