Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 221044
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
644 AM EDT Tue Aug 22 2017

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

&&

.SYNOPSIS...
Issued at 210 AM EDT Tue Aug 22 2017

A cold front is forecast to cross Indiana today. By Wednesday high
pressure will extend across central parts of both the USA and Canada.
This high pressure system is expected to be very long lasting. It
should control Hoosier weather through Monday.

&&

.NEAR TERM (Today)...

Issued at 210 AM EDT Tue Aug 22 2017

Thunderstorms are likely. Otherwise this is a low confidence
forecast.

All models have thunderstorms occurring as a front passes today,
but they differ in the details. The HRRR in particular has several
waves of storms.

An all-day rain is unlikely. Whether it will be raining at any
given time is uncertain. Severe weather is not probable today, but it
is possible depending on when storms form and how well organized
they get. These issues should gradually be resolved as the HRRR
updates.

For temperatures, consensus should work as well as anything.
However errors could be as much as 5 degrees depending on exactly
when rain occurs.

&&

.SHORT TERM (Tonight through Thursday night)...

Issued at 210 AM EDT Tue Aug 22 2017

The models have come into good agreement. There is high confidence
precipitation should be shortly after 8 pm, with dry weather for the
rest of the period.

There is also agreement skies should be mostly clear, except for
partly cloudy conditions under a secondary system Thursday.

As with other parameters, guidance is close on temperatures.
Consensus should be accurate to within 2-3 degrees.

&&

.LONG TERM /Friday through Monday/...
Issued at 304 AM EDT Tue Aug 22 2017

Good confidence in dry weather with below normal temperatures this
weekend as models agree that surface high pressure and modest upper
ridge will result in tranquil conditions. Then, could see a few
showers or thunderstorms next Monday as models bring Harvey onshore
and hint at hit merging with an upper midwest trough. The blend
responded with small pops, influenced mostly by the further north
GFS which has Harvey over Arkansas by 00z Tuesday. The Canadian and
ECMWF are closer to southeastern Texas at that time with Harvey.
With model differences, do not see a strong reason to pull the small
pops Monday at this point.

Good confidence in blend trends regarding temperatures as high
pressure over the northeastern quadrant of the states along with
Quebec and Ontario support below normal temperatures. Highs will be
mostly in the 70s with some lower 80s possible south. Lows will be
mostly in the 50s.

&&

.AVIATION (Discussion for 221200Z TAFs)...

Issued at 645 AM EDT Tue Aug 22 2017

Showers and thunderstorms will move south across the area today.
They may produce brief IFR and gusty winds. Exact timing of
storms at any one site is very uncertain, but they should end
before 00Z.

Otherwise, expect VFR, with either no ceilings or ceilings of at
least 5 thousand feet.

Sustained winds 10 knots or less will veer from south to west
with a frontal passage in the afternoon. Gusts to 20 knots could
occur until evening.

Fog might develop late tonight in areas that get rain today. The
extent to which this will happen is still uncertain.

&&

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

$$

SYNOPSIS...JK
NEAR TERM...JK
SHORT TERM...JK
LONG TERM....MK
AVIATION...JK


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