Area Forecast Discussion
Issued by NWS Indianapolis, IN

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS63 KIND 191749

Area Forecast Discussion
National Weather Service Indianapolis IN
149 PM EDT Mon Mar 19 2018

The AVIATION Section has been updated below.


Issued at 324 AM EDT Mon Mar 19 2018

A pair of low pressure systems will bring showers to all or parts of
central Indiana at times this afternoon through Wednesday. Then,
high pressure will bring dry weather to the area through Friday
morning. Finally, another system will bring more rain in for the

Temperatures today will be above normal. Otherwise, look for below
normal temperatures through the week and weekend.


.NEAR TERM /Today/...

Issued at 1026 AM EDT Mon Mar 19 2018

Not much change to going forecast as conditions seem to be
tracking well. Did increase cloud cover in the southwest and south
this afternoon to better match current trends to the southeast
and neighboring offices. The previous discussion follows...

Issued at 324 AM EDT Mon Mar 19 2018
Models in agreement that a low pressure system, currently over
the Oklahoma panhandle, will move into south central Illinois by
00z Tuesday. As it gets closer, moisture and lift will increase
and showers will spread northeast across parts of central Indiana.
The key is timing, thus the main focus today will be timing of
the rain. There should be a sharp cutoff on the northern edge of
the precipitation shield as dew points over our northern counties
will start off in the upper teens. High Resolution Rapid Refresh
reflectivity progs reflects this and has the rain shield not
moving into our southwestern counties until after 18z. This goes
along with the forecast trends and matches nicely with the blend.
Believe the northern edge of the shield will be near a Greensburg
to Franklin to Clinton line at 23z. Low confidence on the precise
location but moderate to high confidence on the trend.

Our extreme southwestern counties were included in the SPC Day1
general thunderstorm outlook. However, after looking at most
unstable instability progs and running Forecast Builder, will leave
mention out.

Surface pressure gradient will tighten as the system gets closer.
This will result in breezy conditions this afternoon with northeast
winds to near 15 knots and gusts to over 20 knots.

There should be enough early day sunshine to allow temperatures to
approach the slightly above normal blend temperatures in the 50s.


.SHORT TERM /Tonight through Wednesday night/...
Issued at 324 AM EDT Mon Mar 19 2018

Main focus will be on PoPs and potential for a light snow
accumulation over our eastern counties Tuesday night.

Non-NAM models in good agreement in the overall synoptic pattern
over the next couple of days. A low pressure system will move along
the Ohio Valley tonight and will be followed by a slow moving upper
trough. The combo will bring rain or snow showers to all or parts of
central through Wednesday morning. The only area that may stay dry
would be our far northwestern counties. The best chances for
precipitation will be over south central sections tonight associated
with the upper low and over southeastern sections Tuesday afternoon
and night associated with the latter feature.

As the upper low moves east of the area tonight, should see a wintry
mix or changeover to snow. However, not confident the mix or
changeover will reach our extreme southern tier until Tuesday
morning, if at all. Forecast Builder suggests more significant
wintry precipitation is possible over our eastern counties Tuesday
night with an inch or more of snow accumulation possible by daybreak
Wednesday. With lows in the upper 20s, this looks reasonable.
However, an upper ridge and surface high pressure will build in
Wednesday afternoon and night. This should allow for clearing and
dry weather Wednesday afternoon and night. With warm ground
temperatures, some sunshine and March increasing sun angle, any
accumulation should not stay on the ground long.

Tight surface low pressure gradient suggests breezy conditions will

High confidence in below normal temperature trends, if not precise
output of the blend.


.LONG TERM /Thursday through Sunday/...

Issued at 314 AM EDT Mon Mar 19 2018

A frontal system approaching from the southwest will bring chances
for precipitation back into the southern counties starting Thursday
night. Chances will increase in the southwestern counties during the
day Friday as a warm front moves nearer to that area. By Friday
night the front will move up into the area and bring much higher
probabilities for precip across the area. These will last into
Saturday night as the surface low moves across the area Saturday and
off to the east Saturday night. Models are indicating some elevated
instability will be available on Saturday, but this far out this
time of year will leave out mention for now and continue to monitor.
With the warm front in the area, could see a decent temperature
gradient across the area, so confidence in temperature forecast is
less than usual for the long term. This will also have a direct
effect on precipitation type, and thus this is lower than usual
confidence as well. Based on a model and guidance consensus, could
see mainly rain chances during the day, changing to a rain/snow mix
and possibly snow in the northern counties at night. Slushy
accumulation may be possible in the north Friday night but very low
confidence at this point.


.AVIATION /Discussion for 19/18Z TAF issuance/...

Issued at 126 PM EDT Mon Mar 19 2018

VFR conditions will start out the TAF period and then visibilities
are expected to reach MVFR conditions overnight for most sites as
rain/snow mix moves into the area. BMG could have visibilities
that reach IFR conditions overnight.

An upper level low pressure system will be moving over southern
Indiana Monday night. This system will bring with it snow, rain
and a rain/snow mix for our central and southern TAF sites
starting tonight and lasting through the TAF period. Models differ
on the northern extent of the precipitation coverage as the HRRR
has the precip setting up further south than other models. Thus
confidence is not high that IND and HUF will be impacted and left
VCSH at those sites.

Winds will start out easterly and transition to northeasterly and
northerly by the end of the TAF period. Winds could gust up to 20
to 25 kts at some sites.




AVIATION...KH/MRD is the U.S. government's official web portal to all federal, state and local government web resources and services.