Area Forecast Discussion
Issued by NWS Indianapolis, IN

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378
FXUS63 KIND 261838
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
238 PM EDT Wed Jul 26 2017

.UPDATE...
The LONG TERM Section has been updated below.

&&

.SYNOPSIS...
Issued at 155 AM EDT Wed Jul 26 2017

High pressure over the east coast will control Indiana weather into
tonight.  Thursday through Friday a slow moving cold front should
cross our state from the northwest. High pressure is forecast to be
the big weather maker Friday night through Monday as its center
moves from the upper Great Lakes to the central Appalachians.
Another cold front should reach Indiana Tuesday.

&&

.NEAR TERM (Today)...

Issued at 155 AM EDT Wed Jul 26 2017

The models continue to agree today will be dry thanks to high.
pressure. Based on the amount of cirrus upstream and increasing low
level moisture, mostly sunny, as opposed to sunny, is the best
forecast. Given model agreement, consensus temperatures should be
accurate to within 2 degrees.

&&

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

Issued at 155 AM EDT Wed Jul 26 2017

The main issues are timing and intensity of precipitation.

There is strong agreement Thursday is going to be wet. Whether rain
will start late tonight, and whether it will last into Thursday
night aren`t so clear. There is also disagreement about whether a
secondary system justifies low POPs on Friday.  Given the
uncertainties with convection, no one model may have all the
answers. Consensus POPs should be best.

Mostly clear weather is on tap Friday night.

Extremely heavy rain is possible.  Both the NAM and GFS are
forecasting near record precipitable water.  They are also both
forecasting high freezing levels and so-called skinny CAPE
consistent with the efficient warm rain process.

A flash flood watch may eventually be needed. When and where should
be clarified with the run of convection allowing models this
afternoon.

There is much uncertainty about temperatures since they will be very
sensitive to rain timing and intensity. Forecast uncertainty is
about 3 degrees tonight and 5 degrees later.

&&

.LONG TERM /Saturday night through Wednesday/...

Issued at 228 PM EDT Wed Jul 26 2017

A strong upper level low pressure system will exit the Midwest and
move into the Appalachians Saturday night leaving behind northerly
flow that will persist through much of the long term period.  At
the surface, north to northeasterly winds will keep temperatures in
the low to mid 80s and keep dewpoints in the low to mid 60s.

There is high confidence for dry weather through Tuesday. A weak
upper level disturbance will move across the Midwest on Monday and
Tuesday, but with very dry air aloft, chances for precipitation are
low. Better chances for rain for Wednesday with several models
showing an upper level shortwave strengthening over the High
Plains and moving east into the Midwest.


&&

.AVIATION /Discussion for 26/18Z TAF Issuance/...

Issued at 112 PM EDT Wed Jul 26 2017

VFR conditions are expected through 6Z tonight before scattered
showers and thunderstorms move into central Indiana and bring
possible MVFR ceilings and visibility.

High pressure will continue to weaken this afternoon as an upper
level disturbance approaches the state bringing good chances for
showers and thunderstorms tonight. Exact timing is still uncertain
at this time, but the best chances look to be between 6Z and 14Z
with a line of thunderstorms moving across the state and trailing
stratiform behind. Another round of showers and thunderstorms are
possible Thursday afternoon, but with low certainty it will be
left out at this time.

Winds will generally be light and variable through the period
except for instances of thunderstorms. Ceilings will fall into
MVFR conditions shortly after sunrise and will slowly rise
through the afternoon.


&&

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

$$

SYNOPSIS...JK
NEAR TERM...JK
SHORT TERM...JK
LONG TERM....White/Tucek
AVIATION...White/Koch



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