Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 010453
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1253 AM EDT SUN MAY 1 2016

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

&&

.SYNOPSIS...
ISSUED AT 233 PM EDT SAT APR 30 2016

AN UPPER LOW OVER NORTHWESTERN KANSAS AND SOUTHWESTERN NEBRASKA WILL
WEAKEN AND MOVE ACROSS THE GREAT LAKES SUNDAY NIGHT. MEANWHILE...A
WARM FRONT WILL LIFT NORTHEAST TO CENTRAL INDIANA BEFORE STALLING
AND THEN MOVING SOUTHEAST OF THE AREA SUNDAY NIGHT. THESE TWO
FEATURES WILL KEEP SHOWERS AND THUNDERSTORMS AROUND THROUGH SUNDAY
EVENING.

AN UPPER SYSTEM WILL BRING SMALL SHOWER CHANCES BACK TO THE AREA
MONDAY. THEN...SURFACE HIGH PRESSURE WILL BUILD IN AND ALLOW FOR DRY
WEATHER THROUGH TUESDAY NIGHT. MEANWHILE...A COLD FRONT WILL DROP
SOUTHEAST OVER THE AREA ON WEDNESDAY AND BRING SHOWER CHANCES BACK
WEDNESDAY THROUGH THURSDAY. NEXT WEEKEND LOOKS TO BE MOSTLY DRY
UNDER THE INFLUENCE OF HIGH PRESSURE.

TEMPERATURES THROUGH THE NEXT SEVEN DAYS WILL BE NORMAL TO BELOW
NORMAL WITH HIGHS MOSTLY IN THE 60S.

&&

.NEAR TERM /REST OF THIS AFTERNOON AND TONIGHT/...
ISSUED AT 1000 PM EDT SAT APR 30 2016

ADDITIONAL TWEAKS MADE TO POP GRIDS. WATCHING THUNDERSTORM LINE
SEGMENTS TO OUR WEST...APPEARS LIKELY THEY WILL AT LEAST CLIP
SOUTHWESTERN FORECAST AREA LATER TONIGHT. PREVIOUS DISCUSSION
FOLLOWS.

ISSUED AT 233 PM EDT SAT APR 30 2016

POPS AND SEVERE POTENTIAL WILL BE THE MAIN CONCERNS FOR THE NEAR
TERM.

SWATHS OF MODERATE INTENSITY SHOWERS HAVE SPREAD NORTHEAST ACROSS
CENTRAL INDIANA THIS MORNING AND EARLY AFTERNOON AS A WARM FRONT
LIFTED NORTHEAST INTO WESTERN PARTS OF ILLINOIS AND KENTUCKY AND
EASTERN PARTS OF TENNESSEE. ALSO...AN UPPER LOW WAS NEAR THE
NEBRASKA...IOWA AND MISSOURI BORDERS...AND A WAVE...EJECTED
NORTHEAST BY THIS LOW...WAS OVER WEST CENTRAL INDIANA HELPING THINGS
ALONG.

MODELS ARE IN GOOD AGREEMENT THAT DRIER MID LEVEL AIR WILL BE
SPREADING EASTWARD ACROSS CENTRAL INDIANA LATE TODAY AND TONIGHT AS
THE WARM FRONT MOVES INTO SOUTH CENTRAL INDIANA. LATEST NATIONAL
RADAR LOOP WOULD SUPPORT THAT. IN ADDITION...30-40 KNOT LOW LEVEL
JET WILL MOVE IN AND 100 KNOT UPPER LEVEL JET STREAK WILL SPREAD
NORTHEAST ACROSS CENTRAL INDIANA. FINALLY...MID LAPSE RATES TO
STEEPEN TO AROUND 8 DEGREES C/KM. THE LINGERING LOW LEVEL
MOISTURE...STEEP LAPSE RATES AND DRYING ALOFT WILL ALLOW THE
ATMOSPHERE TO BECOME PROGRESSIVELY MORE UNSTABLE THROUGH THE
NIGHT...ESPECIALLY ACROSS THE MARGINAL RISK AREA. HOWEVER...THE
QUESTION IS...WILL THE INSTABILITY WILL BE SUFFICIENT? MOST MODELS
HAVE AT LEAST 300 J/KG OVER OUR SOUTHERN HALF TONIGHT. STILL THINK
THERE IS A NON-ZERO POTENTIAL FOR A FEW LATE DAY AND NIGHTTIME
SEVERE STORMS WITH GIVEN THE SHEAR PROFILE. WILL GO WITH HIGHEST
POPS NORTHEAST WHERE THE MORE SOLID SHOWERS WILL BE EXITING THIS
EVENING. OVERNIGHT...POPS IN THE CHANCE CATEGORY LOOK GOOD ALL
COUNTIES AS THE LOW LEVEL JET SHIFTS EAST INTO OHIO.

LOOKS LIKE MOST AREAS WILL SEE UP TO ABOUT THREE QUARTERS OF AN INCH
OF RAIN THROUGH TONIGHT WITH THE POTENTIAL OF THOSE LOCALES THAT SEE
HEAVIER STORMS THIS EVENING.

WILL GO NEAR 12Z BLEND FOR OVERNIGHT LOWS. LOWS WILL BE HIGHLY
DEPENDENT ON WHERE THE FRONT ENDS UP...SO NOT AS CONFIDENT REGARDING
LOWS OVER THE SOUTH CENTRAL COUNTIES.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
ISSUED AT 233 PM EDT SAT APR 30 2016

MAIN FOCUS FOR THE SHORT TERM WILL BE SEVERE POTENTIAL AND POPS
SUNDAY AND SUNDAY NIGHT.

MODELS AGREE THAT WAVY FRONT WILL MOVE SOUTHEAST OF THE AREA SUNDAY
NIGHT. HOWEVER...BEFORE THAT...MODELS HAVE MIXED LAYER CAPES TO 1000
J/KG OR MORE BY 18Z...MAINLY OVER OUR SOUTHEASTERN COUNTIES. IN
ADDITION...70 MID LEVEL JET WILL BE MOVING INTO WEST CENTRAL INDIANA
DURING THE AFTERNOON AND EVENING COINCIDENT WITH A 250 MILLIBAR 100
KNOT JET STREAK. AS A RESULT...THE STORM PREDICTION CENTER HAS
ISSUED A MARGINAL RISK FOR AREAS NEAR AND EAST OF A KOKOMO TO
GREENCASTLE TO WASHINGTON LINE. UNIDIRECTIONAL FLOW WITH GOOD SPEED
SHEAR SUGGESTS THE POTENTIAL FOR SPLITTING CELLS AND LARGE HAIL AS
THE MAIN THREAT. THE RISK MAY NEED TO BE UPGRADED AT SOME POINT PER
SPC.

AS THE FRONT SETTLES FURTHER SOUTHEAST AND HIGH PRESSURE BUILDS
IN...SHOULD SEE THE RAIN BRIEFLY END OVERNIGHT SUNDAY NIGHT. BEST
CHANCE OF THUNDERSTORMS SHOULD BE SUNDAY AFTERNOON WITH SCATTERED TO
WIDESPREAD COVERAGE.

MODELS ARE NOW MORE PESSIMISTIC REGARDING THE POTENTIAL FOR MORE
SHOWERS EARLY NEXT WEEK ASSOCIATED WITH A SLOW MOVING GREAT LAKES
UPPER TROUGH. IN FACT...12Z MOS 12 HOUR POPS FOR SOME OF OUR LOCALES
ARE 50 PERCENT OR HIGHER FOR MONDAY AND OR MONDAY NIGHT. WITH MOS
POPS THIS HIGH...IT IS HARD TO IGNORE. SO...AFTER COORDINATING WITH
LOCAL OFFICES...WILL INTRODUCE SMALL POPS MONDAY AND MONDAY NIGHT.
SHOULD SEE SOME SUNSHINE ON TUESDAY IN THE WAKE OF THE TROUGH.

12Z MOS BLEND LOOKS GOOD ON TEMPERATURES CONSIDERING EXPECTED CLOUD
COVER AND LOW LEVEL THERMAL PROGS.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
ISSUED AT 245 PM EDT SAT APR 30 2016

A LARGE UPPER TROUGH WILL DIG OVER THE EASTERN U.S. KEEPING
TEMPERATURES NEAR TO SLIGHTLY BELOW NORMAL THROUGH THE LONG TERM.
WEDNESDAY WILL SEE THE BEST CHANCES FOR RAIN THROUGH THE
PERIOD...OTHERWISE MOSTLY JUST SLIGHT CHANCES OF LIGHT SHOWERS. NO
INSTABILITY TO SPEAK OF SO AT THIS TIME NO THUNDER INCLUDED.
GENERALLY ACCEPTED SUPERBLEND INITIALIZATION.

&&

.AVIATION /DISCUSSION FOR THE 01/0600Z TAFS/...

ISSUED AT 1247 AM EDT SUN MAY 1 2016

SCATTERED CONVECTION EXPECTED OVERNIGHT AS A VORTICITY LOBE
CURRENTLY OVER ILLINOIS MOVES THROUGH THE AREA. LIFTING DOESN/T
APPEAR PARTICULARLY STRONG TONIGHT GIVEN ONLY 15-20 KTS OF FLOW AT
850MB. QUESTIONABLE WHETHER CONVECTION WILL BECOME WIDESPREAD
ENOUGH TO RESULT IN DIRECT IMPACTS. WILL MAKE A LAST MINUTE DECISION ON
THAT AT ISSUANCE TIME. CONVECTION THREAT SHOULD DIMINISH AROUND DAYBREAK
AS THE VORTICITY LOBE PASSES OFF TO THE EAST.

OTHERWISE...MOST OF THE IFR CEILINGS HAVE BEEN DISSIPATING AS LIFT
HELPS TO MIX UP THE AIR MASS...BUT SHOULD SEE CEILINGS 004-007 AGL DEVELOP
AGAIN TOWARDS DAYBREAK AS LIFT DIMINISHES. MODEL DATA INDICATE RATHER DRY AIR
ALOFT WILL MOVE INTO THE AREA LATER SUNDAY MORNING...WHICH SHOULD HELP TO
DISSIPATE THE IFR CEILINGS TOWARDS LATE MORNING OR MIDDAY.

SURFACE WINDS GENERALLY LESS THAN 7 KTS OVERNIGHT AND INTO THE MORNING HOURS
SUNDAY...EXCEPT NEAR ANY CONVECTION. WINDS SHOULD BECOME 260-290 AT 7-10 KTS
BY MIDDAY SUNDAY.

&&

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

&&

$$

SYNOPSIS...MK
NEAR TERM...MK/NIELD
SHORT TERM...MK
LONG TERM...CP
AVIATION...JAS


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