Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 261037
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
637 AM EDT Wed Jul 26 2017

.UPDATE...
The AVIATION 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 through Tuesday/...
Issued at 240 AM EDT Wed Jul 26 2017

Amplified flow aloft will persist through much of the
extended...with the center of the heat ridge retreating to the
southern Rockies and Intermountain West while much of the country
east of the Mississippi River will remain under the influence of a
broad upper level trough. The result will be dry weather and cooler
than normal temperatures for much of the long term. Confidence
remains high on the forecast through much of the extended.

The upper low that will dive through the Great Lakes on Friday and
into the Appalachians Saturday will remain in close enough
proximity to influence the weather over central Indiana for the
first part of the weekend. While the airmass will remain
dry...presence of an unusually strong upper low for this time of
year will support cooler temperatures...with growing support that
much of the forecast area will stay in the 70s during the day
Saturday.

This feature will shift off the mid Atlantic coast and weaken
rather quickly...but the region will remain under the influence of
an upper trough into early next week. With a dry northerly flow...
expect mainly clear skies through Monday with temperatures remaining
below normal but gradually warming as mid level heights slowly
modify. Highs will return to near normal levels next week in the
lower to mid 80s. Could see isolated showers and storms by Tuesday
as a weak wave aloft drifts into the area on the edge of the
expanding ridge but overall confidence in this occurring remains
low at this time.

&&

.AVIATION /Discussion for 261200Z TAF Issuance/...
Issued at 637 AM EDT Wed Jul 26 2017

VFR conditions through this evening...restrictions may develop
within convection predawn Thursday.

High pressure located over the northeast states will drift off the
East Coast today. The high will remain close enough to keep skies
mainly clear this morning with a subtle increase in high clouds
and perhaps a few cu this afternoon. Surface flow will veer around
to southerly later today as the high moves away...enabling a
gradual increase in low level moisture into the Ohio Valley.

Clouds will increase further this evening into the overnight as a
convective cluster is expected to develop over Iowa and track
southeast towards the forecast area late tonight. An increasing
low level jet organizing ahead of low pressure will enable
convection to migrate into the area after 07-08Z and continue
through Thursday morning. Will introduce VCTS at all terminals in
the predawn hours with the potential for restrictions to develop
within heavier storms.

&&

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

&&

$$

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



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