Special Weather Statement, NWS Indianapolis, IN

Area Forecast Discussion
National Weather Service Indianapolis IN
436 AM EDT FRI JUL 22 2016

.UPDATE...
The Aviation Section has been updated below.

&&

.SYNOPSIS...
Issued at 209 AM EDT Fri Jul 22 2016

Hot and Humid weather is expected to persist through the weekend
due to strong high pressure over the Central Plains and very humid
air over the Ohio Valley. The heat and humidity will lead to heat
index values between 105 and 110 on Friday and Saturday.

An upper level weather disturbance may arrive in the area on late
Friday or early Saturday...providing some relief in the way of
Thunderstorms. Relatively cooler weather is expected to arrive on
Monday along with more showers and storms as a cold front arrives
in the area.

Dry weather is expected after Monday as High pressure arrives in
the area along with typical Indiana summer time temperatures.

&&

.NEAR TERM /Today/...

Issued at 209 AM EDT Fri Jul 22 2016

Radar shows a dying thunderstorm complex over NW Indiana and NRN
Illinois..drifting southward. Surface analysis shows high pressure
in place across Missouri and Arkansas with a ridge axis extending
NE into the Ohio Valley. Terrible dew points in the middle and
upper 70s were in place across Central Indiana...amid weak
southerly Surface flow.

Nam fails to recognize ongoing convection to the northwest. That
is all I am gonna say about the NAM. Propagation thicknesses
suggest the convective cluster will continue to drift south and
should wane in intensity as is typical at this time of night.
Cloud tops appear to be warming already. This will set the stage
for a cloudy start across Central Indiana as this system
dissipated through the morning hours. The heat will then be on
this afternoon as full sun returns. Dew points in the upper 70s
are gonna make you sweat. Forecast soundings show plenty of CAPE
this afternoon with convective temperatures again near 90. Based
upon persistence...Highs near 90 should be easily reached. Thus
cannot rule out afternoons showers and storms...and Central
Indiana remains on the edge of the broad ring of fire as seen on
water vapor imagery. Thus will try and keep a dry period in
forecast during the late morning hours...followed by chances for
precip to return by late afternoon.

Heat advisory still looks reasonable given the very high and
downright oppressive dew points.

&&

.SHORT TERM /Tonight through Sunday Night/...

Issued at 209 AM EDT Fri Jul 22 2016

GFS keeps the moist anti-cyclonic flow across the Central Plains
and Indiana tonight...this time bringing upper
support...depicting a weak shirt wave passing within the flow.
Forecast soundings again hint toward saturation...and with the
very warm and very moist air mass in place...again thunderstorms
cannot be ruled out. CAPE tonight is well over 2000
j/kg...providing plenty of potential. Again with little chance in
the air mass...but potential for rain...will trend lows into the
lower 70s...due to expected rain cooled air.

More of the same looks in store for Saturday and Sunday. Forecast
soundings on each of those days show very high CAPE over 3000
j/kg along with attainable convective temperatures. Aloft the gFS
continues to suggest several short waves pushing across the upper
midwest and into Indiana. This should lead to ideal triggering
mechanisms for storms. Pwats remains very high as you would expect
with air mass...near or above 2 inches. Thus heavy rains will be
possible with any storms that do develop.

The best short wave of the bunch appears to pass on Sunday and
Sunday night along with a cold front that looks to push out of the
upper midwest into the Great Lakes and Indiana. Again...little
change in the air mass remains in place ahead of the front and
plenty of moisture...heat and instability should be in place. Thus
will again trend pops highs on Sunday and Sunday night as these
features pass.

As for temps through Sunday...will continue with a persistence
type forecast as there is not much change in the air mass. May
trend overnight lows slightly cooler due to possible overnight
rains and rain cooled air.

&&

.LONG TERM /Monday through Thursday/...

Issued at 237 AM EDT Fri Jul 22 2016

The long term forecast for central Indiana is characterized by a
retrograding upper ridge. This will allow for temperatures to cool
a bit from where they are now returning closer to normal for this
time of year. The aforementioned shift westward of the upper
ridge will also allow shortwaves to move through the upper
pattern and bring off and on thunderstorm chances to the area in
the northwest flow.

On Monday a cold front moving through the area will bring shower
and thunderstorm chances, and in its wake slightly cooler and
drier air will arrive. Tuesday into Wednesday should be dry, but
then thunderstorm chances ramp up as a frontal system approaches
for the latter half of the week.

&&

.AVIATION /Discussion for the 220900Z TAFS/...

Issued at 436 AM EDT Fri Jul 22 2016

Thunderstorm complex over eastern Illinois and western Indiana
continues to move SSE but has weakened some with time. Took thunder
mention out of KLAF, and left a VCTS at KIND but took out tempo TSRA
based on radar loop, with storms near KHUF maintaining themselves
but those nearer to KIND dissipating enough that only some showers
are left. At KBMG made no changes yet given the line has picked up a
little over the last hour and still uncertain how far east it will
develop. Brief MVFR to IFR visibility restrictions and gusty
shifting winds in and near heavier convective cells. CB bases 030-
040.

Outside of convective areas, threat for visibility restrictions in
fog is nonzero given the high dewpoints, but don't think much fog
will develop due to convection keeping the air mass mixed up.
Light surface winds overnight expected to become 220-250 degrees at
8-12 kts by early afternoon Friday.

&&

.IND Watches/Warnings/Advisories...
Heat Advisory from 10 AM this morning to 8 PM EDT Saturday for
INZ021-028>031-035>049-051>057-060>065-067>072.

&&

SYNOPSIS...PUMA
NEAR TERM...PUMA
SHORT TERM...PUMA
LONG TERM....CP
AVIATION...JAS/CP

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
318 AM EDT FRI JUL 22 2016

INZ021-028>031-035>049-051>057-060>065-067>072-230730-
CARROLL-WARREN-TIPPECANOE-CLINTON-HOWARD-FOUNTAIN-MONTGOMERY-BOONE-
TIPTON-HAMILTON-MADISON-DELAWARE-RANDOLPH-VERMILLION-PARKE-PUTNAM-
HENDRICKS-MARION-HANCOCK-HENRY-VIGO-CLAY-OWEN-MORGAN-JOHNSON-SHELBY-
RUSH-SULLIVAN-GREENE-MONROE-BROWN-BARTHOLOMEW-DECATUR-KNOX-DAVIESS-
MARTIN-LAWRENCE-JACKSON-JENNINGS-
INCLUDING THE CITIES OF...LAFAYETTE...FRANKFORT...KOKOMO...
CRAWFORDSVILLE...ANDERSON...MUNCIE...INDIANAPOLIS...TERRE HAUTE...
SHELBYVILLE...BLOOMINGTON...COLUMBUS...VINCENNES...BEDFORD...SEYMOUR
318 AM EDT FRI JUL 22 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL INDIANA.

.DAY ONE...TODAY AND TONIGHT.

OUTLOOK: ISOLATED SEVERE THUNDERSTORMS ARE POSSIBLE. HEAT
INDICES WILL REACH OVER 105 THIS AFTERNOON.

HAZARDS: HOT AND VERY HUMID CONDITIONS ARE EXPECTED TODAY.
BLINDING RAINS CAUSING LOCALIZED FLASH FLOODING... DAMAGING WINDS
AND PROLIFIC LIGHTNING.

TIMING: THUNDERSTORMS ARE POSSIBLE EARLY THIS MORNING AND AGAIN
THIS AFTERNOON AND TONIGHT. HEAT INDEX READING WILL REACH OVER 105
DURING THE AFTERNOON HOURS.

DISCUSSION: A VERY WARM AND HUMID AIR MASS WILL REMAIN OVER
CENTRAL INDIANA TODAY AND TONIGHT. A WEAK UPPER LEVEL WEATHER
DISTURBANCE IN COMBINATION WITH THE WARM AIR MASS MAY RESULT IN
THUNDERSTORMS THIS MORNING AND AGAIN LATE THIS AFTERNOON AND
TONIGHT.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

OUTLOOK: BOTH VERY HOT AND HUMID WEATHER WITH A CHANCE OF
THUNDERSTORMS IS EXPECTED THROUGH THE WEEKEND. MAX HEAT INDICES
FROM 100 TO 110 DEGREES ARE EXPECTED DURING PEAK HEATING SATURDAY
AND SUNDAY. MILDER TEMPERATURES WILL RETURN MONDAY WITH DRY
WEATHER STARTING MONDAY NIGHT.

DISCUSSION: EXTREMELY WARM AND HUMID AIR FROM THE GULF OF MEXICO
WILL STAY ACROSS INDIANA THROUGH THE WEEKEND. PERIODIC THREATS
FOR STORMS WILL CONTINUE UNTIL A FRONT PASSES MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND TONIGHT.

&&

MORE INFORMATION...ALONG WITH OTHER WEATHER...HYDROLOGICAL AND
CLIMATE INFORMATION CAN BE FOUND...AT HTTP://WEATHER.GOV/IND (ALL
LOWERCASE)

PUMA

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
502 AM EDT FRI JUL 22 2016

INZ052-053-061-220945-
OWEN IN-CLAY IN-GREENE IN-
502 AM EDT FRI JUL 22 2016

...SIGNIFICANT WEATHER ADVISORY FOR CLAY...NORTHEASTERN GREENE AND
OWEN COUNTIES UNTIL 545 AM EDT...

AT 501 AM EDT...DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM 15
MILES SOUTH OF BRAZIL...OR 18 MILES SOUTHEAST OF TERRE HAUTE...MOVING
SOUTHEAST AT 20 MPH.

DIME SIZE HAIL AND WIND GUSTS UP TO 50 MPH WILL BE POSSIBLE WITH THIS
STORM.

LOCATIONS IMPACTED INCLUDE...
BLOOMFIELD...SPENCER...JASONVILLE...WORTHINGTON...CLAY CITY...CENTER
POINT...COAL CITY...COALMONT...MCCORMICKS CREEK STATE PARK...
PATRICKSBURG...SALINE CITY...CORY...FREEDOM AND BOWLING GREEN.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TORRENTIAL RAINFALL IS ALSO OCCURRING WITH THIS STORM...AND MAY LEAD
TO LOCALIZED FLOODING. DO NOT DRIVE YOUR VEHICLE THROUGH FLOODED
ROADWAYS.

FREQUENT CLOUD TO GROUND LIGHTNING IS OCCURRING WITH THIS STORM.
LIGHTNING CAN STRIKE 10 MILES AWAY FROM A THUNDERSTORM. SEEK A SAFE
SHELTER INSIDE A BUILDING OR VEHICLE.

&&

LAT...LON 3935 8724 3950 8708 3929 8668 3926 8668
      3896 8694 3919 8724
TIME...MOT...LOC 0901Z 288DEG 16KT 3930 8711

CP