River Flood Warning 108, NWS Indianapolis, IN

Area Forecast Discussion
National Weather Service Indianapolis IN
107 PM EDT Wed Mar 18 2020

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

&&

.SYNOPSIS...
Issued at 335 AM EDT Wed Mar 18 2020

Rainy conditions will return for the next few days due to
multiple disturbances passing through the Great Lakes region. Some
showers on Thursday could produce thunderstorms with the
possibility of reaching severe criteria. Severe weather is
expected to be isolated at this point. A strong cold front will
pass through Friday dropping temperatures into the low 40s this
weekend, although sunny skies will return. Next chance for rain
will be next Monday night into Tuesday.

&&

.NEAR TERM /Rest of Today and Tonight/...

Issued at 1044 AM EDT Wed Mar 18 2020

Scattered showers continue across parts of central Indiana at 1030
am, moving northeast around 45 mph. Still expect widespread rain
across the area during the afternoon as better forcing arrives.
Looking at elevated instability in high res models and the lightning
currently to the southwest of the forecast area, added a slight
chance for thunderstorms for the afternoon and evening over much of
the area, starting in the southwest and overspreading from there.
Kept it mainly along and south of I-70. Going high temperatures look
reasonable and no changes made there.

Relevant parts of previous discussion follow...

The majority of the forcing this evening and tonight will the
moderate vorticity advection and a subtle jet streak aloft. Some
warm air advection near 850mb aid in the production of rain, but
will actually inhibit convective development with this system by
stabilizing the low levels. Some embedded thunder is possible within
pockets of heavy rainfall, but with the lack of extent and
confidence, thunderstorms have been left out of the forecast for
today and tonight. Some dry air intrusion within isentropic descent
behind the shortwave will limit rain chances after midnight,
although an semblance of cloud cover should remain.

Prolonged cloud cover and rainfall during peak diurnal warming will
damper high temperatures for Wednesday, but expect a steady increase
in temperatures as warm, moist air is advected in the low-levels
over central Indiana. With this in mind, highs will be in the low
50s this afternoon, with minimal cooling overnight. Winds will
shift to primarily SE at around 10 knots this afternoon.

&&

.SHORT TERM /Thursday through Friday Night/...

Issued at 335 AM EDT Wed Mar 18 2020

A more pronounced and organized low pressure system will approach
Indiana Thursday. An initial round of rain along a defined warm
front will progress over central Indiana in the late morning
hours. After which, showers will be likely throughout the
afternoon, evening and overnight hours, some of which will be
convective in nature. Discrepancies between models exist in the
extent of showers Thursday afternoon, with some maintaining dry
periods. Given dew points in the low 60s and sufficient lift,
expectations are showers will be fairly widespread. Decreased
precipitation in the afternoon would allow for some
destabilization and increased convective activity in the
evening/overnight. Temperatures will increase throughout the day
on Thursday with highs nearing 70 towards the south. Extend of the
afternoon showers will have an impact on afternoon highs.

Severe thunderstorms will be a possibility Thursday evening and
night. Convective allowing models have trended towards an increase
in surface cyclogenesis of the aforementioned low pressure
system, inducing a southerly shift of the low-level winds. This
has increased directional wind shear, producing 0-3km helicity
values greater than 350 m^2/s^2. As of right now, the main
limiting factor will be the lack of sufficient steep lapse rates
between 900mb and 600mb, restricting updraft strength. Models with
reduced extent in afternoon showers have produced adequate CAPE
values near 1000 J/kg Thursday evening, but confidence in this
outcome is low. Will continue to monitor severe potential, but for
now, thoughts are severe thunderstorms would be isolated with a
small chance for tornadoes.

Friday morning, a cold front will progress through the region
providing a stark drop in temperatures. Morning highs will be in the
upper 50s, with temps in the low 40s by the afternoon. High
pressure aloft will clear out skies by friday evening.

&&

.LONG TERM /Saturday Through Tuesday Night/...

Issued at 243 AM EDT Wed Mar 18 2020

Dry but cool weather is expected to start off this period with
rain chances returning for the next work week.

ECMWF shows strong and large high pressure over the upper midwest
on Saturday...poised to push through the Great lakes to Quebec and
the St. Lawrence valley by Sunday night. The broad high will
maintain its influence across Indiana and the Ohio valley through
the weekend...providing mainly a cool and dry easterly flow. Thus
have trended toward a dry forecast at that time.

Return flow looks to begin on Monday as low pressure deepens over
the southern plains and a warm front is suggested to take shape
over the Tennessee and Ohio Valleys. The front appears well
defined by the ECMWF with good lower level convergence as it
pushes north toward Central Indiana on Monday and continues to
linger across the area through midweek. Thus will include daily
chances for precip on Monday through Tuesday night. Looking
ahead...Wednesday looks wet too.

&&

.AVIATION /Discussion for 181800z TAF issuance/...

Issued at 1251 PM EDT Wed Mar 18 2020

IFR or lower expected for the sites for the rest of the TAF
period with low ceilings and off and on rain. Ceilings should be
the more limiting factor. Could see a few isolated embedded
thunderstorms (more likely at KBMG) this afternoon/evening but low
enough probability at any location to leave out. Could see more
chances for thunderstorms Thursday morning, but these are too far
out in time to include. Will see winds from around 080 to 140 at
about 10 kts for the rest of the day.

&&

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

SYNOPSIS...Updike
NEAR TERM...Updike/CP
SHORT TERM...Updike
LONG TERM....Puma
AVIATION...CP

Hazardous Weather Outlook...UPDATED
National Weather Service Indianapolis IN
1010 AM EDT Wed Mar 18 2020

INZ021-028>031-035>049-051>057-060>065-067>072-191415-
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 Delphi, Flora, Williamsport, West Lebanon,
Lafayette, West Lafayette, Frankfort, Kokomo, Attica, Covington,
Veedersburg, Crawfordsville, Lebanon, Zionsville, Tipton, Fishers,
Carmel, Noblesville, Anderson, Muncie, Winchester, Clinton, Newport,
Rockville, Greencastle, Plainfield, Brownsburg, Danville,
Indianapolis, Greenfield, Cumberland, New Castle, Terre Haute,
Brazil, Clay City, Spencer, Martinsville, Mooresville, Greenwood,
Franklin, Shelbyville, Rushville, Sullivan, Linton, Bloomfield,
Bloomington, Nashville, Columbus, Greensburg, Vincennes, Washington,
Loogootee, Shoals, Bedford, Mitchell, Seymour, Brownstown,
and North Vernon
1010 AM EDT Wed Mar 18 2020

This hazardous weather outlook is for central Indiana.

.DAY ONE...Today and Tonight.

Outlook: There is a slight chance for thunderstorms this afternoon
and evening. Severe storms are not expected.

Hazards: Lightning, heavy rain.

Timing: This afternoon and evening.

Discussion: Scattered rain showers will become more widespread this
afternoon. A few embedded thunderstorms will be possible, with the
main threats being lightning and locally heavy rain.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Outlook: Rain showers are expected Thursday through Friday morning
with scattered thunderstorms. Locally heavy rainfall and flooding
will be the greatest concerns. 2 to 3 inches of rain are possible
from Wednesday through Friday with locally higher amounts. The greatest
threat for thunderstorms will be Thursday evening through the
overnight hours with a few severe storms possible.

Discussion: A warm front will move into the region on Thursday and
bring multiple chances for rain and eventually scattered
thunderstorms Thursday through Friday morning before a cold front
sweeps across the area. Dry and cooler weather is expected this
weekend.

.SPOTTER INFORMATION STATEMENT...

Spotter activation cannot be ruled out Thursday evening.

.STORM MOTION STATEMENT...

The expected storm motion today is from the southwest at 45 MPH.

&&

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