Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 201045

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

The AVIATION section has been updated below.


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 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


.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 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

Temperatures will remain above normal through the period.


.AVIATION (Discussion for the 201200Z TAF Issuance)...
Issued at 645 AM EDT Sun May 20 2018

MVFR conditions expected very early in the period due to patchy fog.
Otherwise, outside of convection, VFR conditions are expected.

Fog will burn off early in the period. Focus then is on what will
happen with thunderstorms currently near St Louis. These storms will
be moving away from instability, so will only include a VCSH mention
at KHUF by 15Z to account for remnants.

Otherwise expect scattered convection to develop this afternoon and
continue into the evening, with perhaps some nocturnal thunderstorm
activity moving in overnight tonight. Will handle with vicinity and
PROB30 mentions for now. Confidence remains low in timing and
coverage of convection.




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