Special Weather Statement, NWS Indianapolis, IN

Area Forecast Discussion
National Weather Service Indianapolis IN
1256 PM EDT Thu Mar 30 2017

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

&&

.SYNOPSIS...
Issued at 232 AM EDT Thu Mar 30 2017

A powerful low pressure system over the Central Plains states will
push a warm front toward Indiana today...pushing showers across
Indiana today. Another round of Thunderstorms will be possible
late this afternoon and evening as the Low pressure system pushes
even closer to Indiana.

A rainy and cooler day is in store on Friday as the low pushes
across Indiana. Dry weather will return on Friday Night and into
the weekend as high pressure builds across Indiana for the
weekend.

More active and wet weather is expected next work week as more low
pressure systems are expected to push through the region.

&&

.NEAR TERM /Rest of Today/...
Issued at 1009 AM EDT Thu Mar 30 2017

Strengthening low pressure centered over eastern Kansas this
morning with a warm front extending from the low E/SE into the
Ohio Valley. Areas of convection continue to drift N/NE across
portions of central Indiana. 14Z temperatures ranged from the mid
40s north to lower 60s in the lower Wabash Valley.

Focus for the rest of the day remains on the convective threat and
particularly concerns for severe weather to impact the forecast
area later this afternoon and into the evening.

The low pressure will track northeast slowly through the course of
the day...prompting the warm front currently draped near the Ohio
River to be pulled north through the area as well by late day.
Scattered convection will continue to impact the forecast area
through the day with a specific focus to more widespread precip
along and north of the warm front as it lifts through the area.
Will maintain highest pops over the northwest half of the forecast
area through mid afternoon...then gradually expand higher pops
over the rest of the area.

Still some questions as to how the convective scenario sets up for
later this afternoon and evening and how great the risk for severe
weather is over central Indiana. Nice upper dynamics over the
region later today highlighted by excellent diffluence in the mid
and upper levels ahead of the upper low. Splitting upper jet
structure ahead of the storm system with the northern jetlet being
drawn north across the region through early evening. Further
down...a low level jet is present this morning over the lower Ohio
Valley further south along the Mississippi River...but recent
model trends are losing the jet before refocusing to our east this
evening.

At the surface...am concerned that bulk of the model guidance
overdoing the expansion of 60 degree+ dewpoints into the area this
afternoon. While potential certainly there to see dewpoints near
or just above 60 in some locations...think most of the area does
not get much warmer than upper 50s dewpoints. Ultimately...this
will have an impact on available instability for storms later
today. The NAM depiction for example of potential for 2000 J/KG
and above CAPE values looks far too bloated considering the
inconsistencies with the low level jet and the likelihood based
on current satellite trends of little if any clearing.

In a nutshell...while the dynamics certainly argue for the severe
weather threat later today...the potential caveats mentioned
above suggest this could set up to be a messy convective scenario
later today with the severe threat being more isolated. Recent hi-
res guidance seems to be picking up on this thinking as well...
bringing multiple areas/lines of convection through the forecast
area this afternoon and evening in an otherwise sloppy fashion.
Low level shear will be initially maximized as the warm front
lifts north this afternoon but should drop back some ahead of the
cold front this evening. While the presence of the directional
shear and storm relative helicity support at least a mention of
tornadoes...certainly does not appear this will be the primary
threat. If storms can reach severe levels...the potential for
large hail and locally damaging winds appear to be greater risks
at this point. Stay tuned into the afternoon as storms evolve.

Zone and grid updates out.

&&

.SHORT TERM /Tonight through Saturday Night/...

Issued at 232 AM EDT Thu Mar 30 2017

GFS and NAM suggest strong forcing arriving this afternoon and
continuing in to the evening hours. Forecast soundings again
suggest a couple periods of showers/storms in the period...showing
deep saturation. Convection from the afternoon will likely bleed
into the evening hours and will need to carry high pops again.
Again, excellent shear in place along with possible instability
suggest severe weather is possible. After the severe threat
ends...forecast soundings again show good lower and middle level
saturation...as the large and broad low pressure system arrives in
the area. Thus again. HIgh pops tonight and will trend lows above
mavmos.

Surface low arrives for Friday. At that point the severe threat
will be lost as instability is gone...but clouds and lower level
moisture will remain in the area as forecast soundings and time
heights show lower level saturation. Will trend pops higher on
Friday than mavmos given light precip that will be expected as the
upper low passes. Will also trend high at or below a forecast
builder blend given the expected clouds and light precip.

Dry weather expected to return for Friday through Saturday night.
Models suggest the low will depart to the east allowing another
Cool canadian high pressure system to build across the region from
the NW. Forecast soundings show mainly a dry column associated
with subsidence...but some lingering lower level moisture. Thus
partly cloudy will work here. Will stick close to the forecast
builder blend here on temps.

&&

.LONG TERM /Sunday Through Wednesday/...
Issued at 249 AM EDT Thu Mar 30 2017

Models are close enough that the model blend initialization
was accepted for most items.

Like a stuck record, a series of low pressure systems will continue
to bring rain chances to much of the Long Term. Of course models
still have a good amount of variability between them, so confidence
remains low in timing of highest PoPs through the period. Thus
decided to just stick with the blend.

Temperatures look to remain above average through the period.

&&

.AVIATION /Discussion for 301800Z TAF Issuance/...
Issued at 1256 PM EDT Thu Mar 30 2017

Restrictions possible in showers and thunderstorms through this
evening...then IFR ceilings developing Friday morning.

Dual low pressure structure over the mid Mississippi and Missouri
Valleys early this afternoon with a warm front extending E/SE
across the forecast area. North of the front...winds remained
easterly while southerly flow had commenced south of the boundary.
The front will continue to lift north through the afternoon as the
dual lows lift northeast. Expect southerly winds to develop at
both KHUF and KIND by 19Z and even pushing through KLAF by later
this afternoon. Expect gusts to peak near 25kts once the warm front
passes.

Convective evolution still remains in question but current
thinking is scattered storms will impact all terminals this
afternoon then become more widespread from 21Z through about 02Z
as the cold front moves through the area. Potential for severe
convection with damaging wind gusts during this time period but
enough uncertainty with respect to timing and intensity to leave
out of the primary tempo group at this time.

Skies may briefly clear late tonight behind the front before lower
clouds associated with the upper low overspread the forecast area
near daybreak Friday. Stratus could be as low as IFR and the
possibility exists at least for a few light showers or drizzle.
Winds will gradually veer to westerly by Friday afternoon.

&&

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

&&

SYNOPSIS...Puma
NEAR TERM...Ryan
SHORT TERM...Puma
LONG TERM...50
AVIATION...Ryan

Hazardous Weather Outlook...UPDATED
National Weather Service Indianapolis IN
1227 PM EDT Thu Mar 30 2017

INZ021-028>031-035>049-051>057-060>065-067>072-311630-
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, and Seymour
1227 PM EDT Thu Mar 30 2017

This hazardous weather outlook is for central Indiana.

.DAY ONE...This Afternoon and Tonight.

Outlook: There is a Enhanced risk for severe Thunderstorms today and
tonight.

Hazards: Damaging winds...large hail...isolated tornados...flash
flooding from torrential rain. Lightning.

Timing: Highest severe chances 3 pm to 10 pm. Thunderstorms possible
for parts of the area until 5 am.

Discussion: Thunderstorms are expected to develop this afternoon and
evening across Central Indiana ahead of a powerful low pressure
system to the west. Some of the storms could become
severe...producing damaging winds...large hail and even an isolated
tornado. Multiple rounds of showers and storms could lead to flash
flooding. Lightning is a threat with any thunderstorm.

The severe threat will diminish after midnight.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Outlook: Storm systems may effect central Indiana on Sunday and again
on Wednesday. It is too soon to determine if these storms will be
severe. Lightning is a threat with any thunderstorm.

Discussion: Low pressure systems will sweep into Central Indiana on
Sunday and again on Wednesday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is possible this afternoon and tonight.

&&

More information, along with other weather, hydrological and climate
information can be found at http://weather.gov/ind

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
134 PM EDT THU MAR 30 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0115 PM     HAIL             NEW CASTLE              39.92N 85.36W
03/30/2017  M0.25 INCH       HENRY              IN   PUBLIC

            .

&&

NWS INDIANAPOLIS IN
IRIS SYSTEM

Special Weather Statement
National Weather Service Indianapolis IN
217 PM EDT THU MAR 30 2017

INZ043-044-051-301845-
Parke IN-Vermillion IN-Vigo IN-
217 PM EDT THU MAR 30 2017

...SIGNIFICANT WEATHER ADVISORY FOR NORTHERN VIGO...PARKE AND
SOUTHEASTERN VERMILLION COUNTIES UNTIL 245 PM EDT...

At 216 PM EDT, Doppler radar was tracking a strong thunderstorm near
Terre Haute, moving northeast at 45 mph.

Half inch hail and wind gusts up to 50 mph will be possible with this
storm.

Locations impacted include...
Terre Haute, Clinton, Rockville, West Terre Haute, Fairview Park,
Seelyville, Montezuma, Rosedale, Universal, Mecca, Bloomingdale,
Marshall, Fontanet, Shepardsville, Cecil Harden Lake, Bridgeton,
North Terre Haute, Judson, Indiana State University and Sandford.

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.

&&

LAT...LON 3958 8753 3990 8728 3975 8701 3972 8701
      3961 8715 3961 8720 3956 8720 3938 8741
      3945 8753
TIME...MOT...LOC 1816Z 216DEG 37KT 3951 8744

CP