Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 260446
AFDIND

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1246 AM EDT SAT JUL 26 2014

.UPDATE...

THE AVIATION SECTION HAS BEEN UPDATED BELOW.

&&

.SYNOPSIS...
ISSUED AT 344 PM EDT FRI JUL 25 2014

SCATTERED THUNDERSTORMS ARE POSSIBLE TONIGHT AS A WARM FRONT LIFTS
THROUGH THE AREA. A WARMER AND MUCH HUMID AIR WILL BUILD INTO THE
OHIO VALLEY FOR SATURDAY. AS A COLD FRONT APPROACHES FROM THE NORTH
BY THE EVENING...WIDESPREAD THUNDERSTORMS WILL DEVELOP ACROSS
CENTRAL INDIANA AND HAVE THE POTENTIAL TO PRODUCE SEVERE WEATHER.
ADDITIONAL CHANCES FOR THUNDERSTORMS WILL COME SUNDAY AS A STRONG
UPPER WAVE TRACKS INTO THE GREAT LAKES. COOLER AIR WILL RETURN FOR
MUCH OF THE UPCOMING WEEK AS A DEEP UPPER TROUGH ONCE AGAIN DEVELOPS
OVER THE EASTERN HALF OF THE COUNTRY.

&&

.NEAR TERM /REST OF TONIGHT/...
ISSUED AT 1000 PM EDT FRI JUL 25 2014

.UPDATE...CONVECTION HAS JUST ABOUT DIED OUT ACROSS THE AREA THIS
EVENING. SHORT TERM MODELS INDICATE IT MAY INCREASE SOME LATER
TONIGHT AS MOISTURE INCREASES. BUT RAPID REFRESH ONLY INDICATING
WEAK SCATTERED AND WEAK ACTIVITY WILL TRIM POPS A LITTLE OVERNIGHT.
WILL ALSO DROP MENTION OF THUNDER FROM INDY AND EASTWARD AS AIRMASS
ONLY BECOME MARGINALLY UNSTABLE ACROSS OUR NORTHWEST LATE TONIGHT.

CURRENT TEMPERATURES ARE TRACK AND NO SIGNIFICANT CHANGES MADE.
PORTION OF PREVIOUS NEAR TERM DISCUSSION FOLLOWS...

FOCUS WILL BE ON PRECIP CHANCES FOR THE REGION TONIGHT AS A WARM
FRONT MOVES INTO THE AREA. DEWPOINTS REMAIN IN THE 50S THIS
AFTERNOON WITH DRIER BOUNDARY AIR SLOWLY BEING ERODED AWAY. DEEPER
MOISTURE BEGINNING TO ADVECT INTO THE FORECAST AREA...WITH
MESOANALYSIS INDICATING A STEADY RISE IN PWATS ABOVE 1 INCH ONGOING.
THIS TREND WILL CONTINUE OVERNIGHT AS THE WARM FRONT LIFTS THROUGH
THE REGION. SHORT RANGE MODEL GUIDANCE FOCUSING BETTER CONVECTIVE
CHANCES WILL EXIST OVER NORTHERN COUNTIES AS THE FRONT LIFTS TO THE
NORTHEAST...WITH INCREASING ELEVATED INSTABILITY THROUGH THE NIGHT.
WILL MAINTAIN HIGHEST CHANCE POPS NORTH OF I-70 WITH LOW POPS
FURTHER SOUTH.

TEMPS...WARMER OVERNIGHT WITH THE PASSAGE OF THE WARM FRONT. EXPECT
MOST AREAS TO BOTTOM OUT IN THE LOWER TO MIDDLE 60S BEFORE BEGINNING
TO RISE TOWARDS DAYBREAK. MODELS WERE CLOSE OVERALL AND TOOK A
GENERAL MOS BLEND.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
ISSUED AT 344 PM EDT FRI JUL 25 2014

FORECAST CHALLENGES FOCUS ON THREATS FOR THUNDERSTORMS AND SEVERE
WEATHER OVER THE WEEKEND...WITH A GROWING POTENTIAL TOWARDS A
SIGNIFICANT SEVERE WEATHER EPISODE FOCUSED ON SATURDAY EVENING INTO
THE OVERNIGHT.

THE PASSAGE OF THE WARM FRONT EARLY SATURDAY WILL USHER IN A WARMER
AND MUCH HUMID AIRMASS ACROSS THE OHIO VALLEY AS THE FLAT UPPER
RIDGE POKES INTO THE REGION FROM THE SOUTHWEST. ARRIVAL OF A STRONG
UPPER LEVEL WAVE FROM THE CANADIAN PRAIRIES SATURDAY MORNING INTO
THE GREAT LAKES ON SUNDAY WILL FORCE A RETROGRADE OF THE UPPER RIDGE
AND AN AMPLIFIED DOWNSTREAM TROUGH OVER THE EASTERN U S BY EARLY
NEXT WEEK. NORTHWEST FLOW ALOFT WILL ALIGN ACROSS THE MIDWEST AND
OHIO VALLEY AS THIS TRANSITION TAKES PLACE...WITH A SERIES OF WAVES
TRAVERSING A SLOWLY SAGGING COLD FRONT. THIS WILL RESULT IN MULTIPLE
OPPORTUNITIES FOR THUNDERSTORMS ALONG WITH A PERSISTENT SEVERE
WEATHER THREAT EXISTING LATE SATURDAY POSSIBLY INTO SUNDAY.

WHILE CLOUD DEBRIS FROM OVERNIGHT CONVECTION LIKELY TO STILL BE IN
THE REGION SATURDAY MORNING...EXPECT LITTLE TO NO PRECIP THROUGH
EARLY AFTERNOON WITH ENHANCED FORCING NEAR THE FRONT BACK TO THE
NORTHWEST OF THE FORECAST AREA AND CAPPING DEVELOPING WITH WARMER
AIR ALOFT. WHILE THE GENERAL THEME AS TO HOW THE CONVECTIVE SETUP
EVOLVES LATER SATURDAY HAS BROAD MODEL SUPPORT...NAM AND SREF BOTH
GENERATING MORE WIDESPREAD CONVECTION FASTER THAN OTHER MODELS WITH
GREATER STORM IMPACTS AS EARLY AS MID/LATE AFTERNOON. BELIEVE THIS
IS PREMATURE CONSIDERING THE PRESENCE OF THE CAP AND THAT 700MB
TEMPS SHOULD BE IN THE 12-13C RANGE THROUGH MUCH OF THE AFTERNOON.
WHILE SCATTERED CONVECTION IS POSSIBLE AS THE AFTERNOON PROGRESSES
DUE TO THE INCREASING AMOUNTS OF LOW LEVEL MOISTURE AND HIGH LEVELS
OF INSTABILITY...THE MORE WIDESPREAD STORMS ARE LIKELY TO HOLD OUT
UNTIL EVENING AT EARLIEST AS THE CAP WEAKENS AND LOW LEVEL JET...BL
SHEAR AND DEEPER FORCING INCREASES.

HIGHEST CONFIDENCE FOR SIGNIFICANT IMPACTS FROM CONVECTION AND
SEVERE WEATHER ARE BEGINNING SATURDAY EVENING INTO THE OVERNIGHT AS
THE COLD FRONT DROPS INTO THE REGION AND A SURFACE WAVE RIPPLES
ALONG IT. A LOT OF FAVORABLE FACTORS SUPPORT RAPID CONVECTIVE
EXPANSION DURING THE EVENING...WITH EXPLOSIVE UPSCALE DEVELOPMENT
INTO AN MCS. A DEVELOPING 35KT LOW LEVEL JET AND HIGH INSTABILITY
POSSIBLY IN EXCESS OF 3000J/KG WILL SERVE AS THE FUEL FOR THE
COMPLEX...PUMPING PROGRESSIVELY DEEPER MOISTURE INTO THE OHIO
VALLEY. PWATS ARE IMPRESSIVE AT NEAR 2.25 INCHES...ABOUT 2 STANDARD
DEVIATIONS ABOVE NORMAL. FORCING AND DIFFLUENCE ALOFT ALONG WITH THE
ARRIVAL OF BL SHEAR VALUES APPROACHING 40KTS WILL FURTHER ENHANCE
CONVECTIVE INTENSITY AND COVERAGE SATURDAY NIGHT. OF FURTHER
INTEREST FROM A CLIMATOLOGICAL STANDPOINT AND SERVING TO STRENGTHEN
CONFIDENCE IN SIGNIFICANT CONVECTION...MANY CIPS ANALOGS OFF BOTH
00Z AND 12Z DATA HIGHLIGHT PAST HIGH END MCS EVENTS PRODUCING A
POTPOURRI OF SEVERE WEATHER AND FLOODING IMPACTS FOR CENTRAL INDIANA
AND THE OHIO VALLEY.

THE PRESENCE OF SUCH HIGH PWATS AND SURFACE DEWPOINTS LIKELY INTO
THE LOW/MID 70S COMBINED WITH HIGH INSTABILITY SUPPORTS THE
POTENTIAL FOR WIDESPREAD DAMAGING WINDS AS THE PRIMARY IMPACT FROM
AN MCS SATURDAY EVENING/NIGHT. CONSIDERING AVAILABLE SHEAR/HELICITY
AND POTENTIAL INTERACTION OF MESOSCALE BOUNDARIES...ALL MODES OF
SEVERE WEATHER WOULD BE ON THE TABLE. IN ADDITION...REMAIN CONCERNED
ABOUT TORRENTIAL RAINFALL AND FLOODING CONSIDERING HOW HIGH PWATS
ARE AND THAT FREEZING LEVELS NEAR 15KFT WOULD SUPPORT WARM RAIN
PROCESSES WITHIN CONVECTION. BACKBUILDING CONVECTION IS ANOTHER
CONCERN DUE TO THE ORIENTATION OF THE LOW LEVEL JET FROM WEST TO
EAST. FINALLY...LIGHTNING WILL ALSO BE A FACTOR...ESSENTIALLY
NON-STOP AT TIMES WITHIN THE COMPLEX.

SUNDAY FORECAST REMAINS HIGHLY CONDITIONAL ON WHAT OCCURS SATURDAY
NIGHT. DEEPER MOISTURE IS FOCUSED TO OUR SOUTHEAST...BUT THE
APPROACH OF THE STRONGER UPPER LOW INTO THE GREAT LAKES SUNDAY
AFTERNOON PROVIDING ANOTHER BOOST IN BL SHEAR AND FORCING ALOFT.
STILL FEEL MCS SATURDAY NIGHT GRUNGES OUT THE AIRMASS IN ITS WAKE
FOR MUCH OF SUNDAY WITH LIMITED INSTABILITY. WITH THAT BEING
SAID...THE PRESENCE OF FORCING ALOFT WITH THE APPROACH OF THE
ANOMALOUSLY STRONG UPPER WAVE WARRANTS A CONTINUATION OF THE
POTENTIAL FOR THUNDERSTORMS AND POSSIBLY ANOTHER SHOT FOR SEVERE
WEATHER. SHOULD ANY SUNSHINE TAKE PLACE SUNDAY...FAVORABLE
THERMODYNAMIC PROFILES WITH STEEP LAPSE RATES WOULD INCREASE THE
SEVERE STORM RISK. FOR NOW...WILL CARRY HIGH CHANCE POPS.

THE UPPER WAVE WILL BECOME ABSORBED IN THE MEAN UPPER TROUGH...
AMPLIFYING IT ACROSS THE EASTERN PART OF THE COUNTRY BY MONDAY.
PASSAGE OF A SHORT WAVE TO OUR EAST SUNDAY NIGHT INTO MONDAY COULD
PRODUCE A FEW SHOWERS...ESPECIALLY OVER THE NORTHEAST HALF OF THE
FORECAST AREA.

TEMPS...TRENDED TOWARDS MAVMOS GUIDANCE FOR TEMPS THROUGHOUT THE
PERIOD. MAV GUIDANCE HAS A BETTER HANDLE ON SATURDAY TEMPS TODAY
WITH HIGHS LIKELY IN THE 85 TO 90 DEGREE RANGE. EXPECT ANY NEAR
90/LOW 90S TO BE CONFINED TO THE LOWER WABASH VALLEY...MEANING INDY
WILL REMAIN WITHOUT A 90 DEGREE HIGH IN 2014. HEAT INDICES COULD
RISE INTO THE MIDDLE AND UPPER 90S OVER SOUTHWEST COUNTIES SATURDAY
AFTERNOON. MUCH COOLER AIR BUILDS IN SUNDAY NIGHT AND MONDAY...
EXPECT HIGHS 10-15 DEGREES BELOW NORMAL MONDAY.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
ISSUED AT 216 PM EDT FRI JUL 25 2014

THE LONG TERM WILL START OUT DRY AND COOL WITH HIGH PRESSURE
BUILDING OVER THE AREA. WITH AN UPPER TROUGH OVER THE EASTERN U.S.
COOLER THAN NORMAL CONDITIONS WILL CONTINUE THROUGH THE LONG TERM
WITH TEMPERATURES SLOWLY WARMING BUT STILL NOT GETTING BACK UP TO
NORMAL. WEAK SHORTWAVES MOVING THROUGH THE MAIN NORTHWEST FLOW
PATTERN COULD BRING IN SMALL THUNDERSTORM CHANCES WEDNESDAY THROUGH
FRIDAY ESPECIALLY ACROSS THE NORTHERN COUNTIES. WITH A WIDE SPREAD
IN ENSEMBLE SOLUTIONS FOR THAT TIME WILL LEAVE THE ALLBLEND SLIGHT
TO LOW CHANCE POPS ALONE.

&&

.AVIATION /DISCUSSION FOR THE 26/06Z TAFS/...
ISSUED AT 1246 AM EDT SAT JUL 26 2014

VFR THROUGH THE PERIOD OUTSIDE OF THUNDERSTORMS POSSIBLE LATE IN THE
PERIOD.

HAVE REMOVED FOG MENTION OVERNIGHT AS CLOUDS ARE LOWERING AND
THICKENING IN ADVANCE OF APPROACHING SYSTEM.

THUNDERSTORMS WILL BECOME AN ISSUE LATE IN THE PERIOD...TOMORROW
EVENING AND ONWARD...BUT WITH A LACK OF CONFIDENCE IN SPECIFIC
TIMING AND IMPACTS WILL HAVE TO CARRY A VCTS MENTION. MODELS AND
ANALOGS INDICATE SEVERE THUNDERSTORMS MAY IMPACT ALL TERMINALS LATE
IN THE TAF PERIOD.

SYNOPTIC WINDS DURING THE PERIOD MAY REACH UP TO 14-15KT...GENERALLY
OUT OF THE SOUTH OR SOUTHWEST.

&&

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

&&

$$

SYNOPSIS...RYAN
NEAR TERM...RYAN/JH
SHORT TERM...RYAN
LONG TERM...CP
AVIATION...NIELD

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