Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 200824
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
424 AM EDT Sun May 20 2018

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

&&

.SYNOPSIS...
Issued at 156 AM EDT Sun May 20 2018

Unsettled weather is expected to continue across Central Indiana
the next few days. A warm and humid air mass is expected to remain
in place across the Ohio Valley as a series of upper level weather
disturbances pass across the state. This will result in daily
showers and thunderstorms across Central Indiana...with best
chances during the afternoon and evening hours.

High pressure is expected to settle across the region for the
middle of the week...leading to some dry and warm weather. More
shower and storm chances will return next weekend.

&&

.NEAR TERM /Today/...

Issued at 156 AM EDT Sun May 20 2018

A poorly organized surface front was found across Central Indiana
early this morning. Water vapor shows mainly a SW flow in place
aloft with several upper disturbances within the flow. Radar
Mosaics show diminishing returns over Missouri and southern
Illinois. Dew points across Central Indiana remain quite
moist...in the middle 60s.

Main forecast challenge today will be pops. GFS and NAM continue
to suggest a short wave approaching this afternoon amid a poorly
organized flow aloft. Models have not been handling the set up
rather well. However Forecast soundings again show steep lapse
rates this afternoon with favorable CAPE and attainable convective
temperatures. Thus with a bit of upper support along with
instability...afternoon and evening shower chances appear very
reasonable. Confidence is low for specific timing or location on
any storms that should develop. Overall will trend toward a 50 pop
for most locations. Will also stick close to the blend for highs
today.

&&

.SHORT TERM /Tonight through Tuesday Night/...

Issued at 156 AM EDT Sun May 20 2018

Confidence for precip timing and locations remains rather low
during this period. The GFS and NAM continue to suggest poorly
defined SW flow in place aloft with several embedded short wave
with in the flow poised to push through the Ohio Valley tonight
through Monday Night. Confidence in these wave is low as the model
tend to not handle them well. Forecast soundings however once
again show the warm...humid and unstable airmass in place through
Monday Night. Thus...with best forcing aided by diurnal
heating...best chances for precip will be during the afternoon and
evening hours. That being said will trend highest pops at those
times...and given the possible hit and miss nature of these
showers and storms will trend the pops a little lower than the
forecast builder Guidance. As for temps through Monday night Night
will trend lows warmer than the blend and stick closet to the
blends on Highs.

By Tuesday and Tuesday Night...the GFS and NAM suggest some weak
ridging aloft and the SW moist flow aloft to be diverted somewhat
to the southeast. Broad lower level high pressure also appears to
be in place for Tuesday and Tuesday Night. Forecast soundings
also trend to introduce some drier air within the column. Thus
will try to aim for a dry forecast at that time....sticking close
to the blend on temperatures.

&&


.LONG TERM /Wednesday Through Saturday/...
Issued at 227 AM EDT Sun May 20 2018

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

Upper ridging and surface high pressure will work to keep the area
dry Wednesday and Thursday. However, there remains some uncertainty
if all areas will remain dry Wednesday with a surface front just to
the south.

A frontal system will bring rain chances Friday afternoon and again
Saturday.

Temperatures will remain above normal through the period.

&&

.AVIATION /Discussion for 200900Z TAF Update/...
Issued at 424 AM EDT Sun May 20 2018

Added 6SM BR to the KIND TAF. It appears that the heat island is
keeping the visibility up there, but wouldn`t be surprised if it did
dip into MVFR for a bit closer to sunrise. Will continue to monitor.
Already updated other sites to MVFR fog.

Previous discussion follows...

VFR conditions expected throughout much of the forecast period.
Low confidence in convective impacts and timing.

Predominantly dry weather is expected through Sunday morning as the
region resides under weak ridging aloft. Most of the hi-res guidance
has backed off on convection moving into the region for the rest of
the night with storms over eastern Missouri moving southeast towards
the lower Ohio Valley. Cannot rule out isolated convection through
the morning with the frontal boundary lingering over the
region...but this is not enough for inclusion into the forecasts at
this point.

High uncertainty exists on how and if a convective complex will
develop over the region Sunday afternoon and evening. Depending on
how much cloud debris lingers over central Indiana in the morning
will ultimately determine how much heating and instability develops
later in the day. The arrival of an upper level wave late afternoon
into the evening may serve as a spark to greater convective coverage
and considering the presence of an unstable airmass and the remnant
frontal boundary...will maintain a VCTS mention at all terminals
from mid afternoon into the evening.

Wind direction is likely to be variable throughout the forecast
period at less than 10kts.


&&

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

$$

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



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