Special Weather Statement, NWS Indianapolis, IN

Area Forecast Discussion
National Weather Service Indianapolis IN
1026 AM EDT Fri May 19 2017

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

&&

.SYNOPSIS...
Issued at 319 AM EDT Fri May 19 2017

An active weather pattern will be in place over central Indiana for
the next seven days, with a stalled frontal system keeping chances
for showers and thunderstorms over the area through much of the
period.

&&

.NEAR TERM /Today/...
Issued at 924 AM EDT Fri May 19 2017

Raised pops to likely near and northwest of a Sullivan to
Indianapolis to Fishers line as east central Illinois broken line of
thunderstorms has held together and should continue to do so despite
what the High Resolution Rapid Refresh was showing.

Previous discussion follows...
Issued at 627 AM EDT Fri May 19 2017

Updated morning forecast to increase pops across northwest counties
and wherever hadn't already changed wording to coverage. Based on
short range consensus also increased pops across the area during the
entire morning, but still have a few hours of lower pops across the
southern and southeastern counties this morning. Previous discussion
follows...

Forecast focus is on timing of precipitation/thunder chances
across central Indiana. Unfortunately short term hi res guidance
shows decent differences in timing and placement of showers and
storms today and that makes for a lower than average confidence
forecast. However indications are that there will be a bit of a lull
during the early morning hours before convective activity picks back
up during the afternoon. There is a slight risk of severe storms
across the southwestern counties with marginal risk elsewhere.
Forecast models show good instability by the afternoon as better
upper forcing arrives but shear will be marginal, with the exception
of low level shear in the vicinity of the front. With the stalled
front projected to shift north again as a warm front, think warmer
overall temperatures are necessary, and a guidance consensus served
this purpose well.

&&

.SHORT TERM /Tonight through Sunday night/...
Issued at 319 AM EDT Fri May 19 2017

An upper low over the intermountain west will move northeast through
nebraska and into the Great Lakes region through the short term.
This will eject shortwaves through the main upper trough toward
central Indiana. These will interact with a stalled surface front
(trapped between the aforementioned upper low and a ridge of high
pressure over the eastern U.S.) to produce chances for showers and
thunderstorms throughout the short term. Timing of individual waves
is variable in the various forecast models making nailing down a
specific wet vs. dry time difficult. At this point the best forcing
appears to be associated with the cold frontal passage Saturday
night.

Models indicate good instability for Saturday/Saturday night. While
bulk shear isn't that impressive, there should be some low level
shear induced by the front. Just about the entire area is in a
slight risk for severe weather, and think the best timing for this
to occur would be late Saturday afternoon into Saturday night.

Temperatures will be highly dependent on whether or not any of these
days is a wash out. Given the model variability would rather choose
a middle of the road solution and this produces highs in the 70s to
lower 80s and lows in the upper 50s to 60s.

&&

.LONG TERM (Monday through Thursday)...
Issued at 330 AM EDT Fri May 19 2017

It will be cool and wet most of the long term period as a closed
upper low over the upper midwest Monday moves towards Indiana and
deepens.   The one exception will be Monday which will be mostly dry
as a weak ridge of high pressure moves east across the Ohio valley.
This will be followed by an area of low pressure and cold front
which will push across our region Tuesday.  Finally another ridge of
high pressure will build into the southern U.S. late day 7 and dry
and weather and slightly warmer temperatures will probably return
late next week after day 7.

Stayed close to model initialized temperatures and POPS most
periods.  Although I would not be surprised if some areas could end
up dry again by Thursday.

&&

.AVIATION (Discussion for 191500Z TAF update)...

Issued at 1027 AM EDT Fri May 19 2017

Scattered showers and thunderstorms will continue around a front
meandering around central Indiana. Some may produce brief LIFR in
heavy rain.

Timing is uncertain. For the most part the situation will be handled
with VCTS. Expect amendments to insert TEMPO groups when short term
precision is possible.

VFR should prevail between storms.

Winds of less than 10 knots will gradually veer from northeast to
southeast. Higher gusts are possible near storms.

&&

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

SYNOPSIS...CP
NEAR TERM...CP/MK
SHORT TERM...CP
LONG TERM....JH
AVIATION...CP/JK

Hazardous Weather Outlook
National Weather Service Indianapolis IN
434 AM EDT Fri May 19 2017

INZ021-028>031-035>049-051>057-060>065-067>072-201000-
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
434 AM EDT Fri May 19 2017

This hazardous weather outlook is for central Indiana.

.DAY ONE...Today and Tonight.

Outlook: Scattered thunderstorms will occur today and tonight. In
addition there is a slight risk of severe thunderstorms mainly this
afternoon...along and south of a Attica to Indianapolis Greensburg
line. Large hail and damaging winds will be the main threat. An
isolated tornado is also possible.

Hazards: Lightning...Damaging winds and large hail.

Timing: Most likely this afternoon.

Discussion: A cold front move to the southern parts of central
Indiana and become stationary this afternoon as low pressure moves
into the middle Mississippi valley. The air mass will become quite
unstable over all but far northern sections this afternoon.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

Outlook: Strong Thunderstorms are possible again Saturday along with
a slight risk of severe weather. Damaging winds...large hail and
heavy rainfall will be the main threat. In addition there is a slight
chance of thunderstorms over eastern sections Sunday and again some
areas Tuesday and Thursday. Except for Saturday...no other outbreaks
of severe weather are expected.

Discussion: Low pressure will move into the great lakes and a cold
front will move across Indiana Saturday night. A closed upper low
over the upper midwest Monday will move to Indiana by the middle of
next week bringing cooler than normal temperatures and unsettled
weather at times.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and again Saturday
afternoon and evening.

&&

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

Special Weather Statement
National Weather Service Indianapolis IN
1032 AM EDT FRI MAY 19 2017

INZ053-061-191515-
Owen IN-Greene IN-
1032 AM EDT FRI MAY 19 2017

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHERN OWEN AND NORTHERN GREENE
COUNTIES UNTIL 1115 AM EDT...

At 1031 AM EDT, Doppler radar was tracking a strong thunderstorm 9
miles northwest of Bloomfield, or 27 miles west of Bloomington,
moving northeast at 45 mph.

Dime size hail will be possible with this storm.

Locations impacted include...
Bloomfield, Spencer, Worthington, Switz City, Solsberry, McCormicks
Creek State Park and Freedom.

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 3917 8706 3921 8705 3931 8672 3897 8669
      3902 8705 3917 8717
TIME...MOT...LOC 1431Z 240DEG 49KT 3914 8702

JK