Area Forecast Discussion
Issued by NWS Indianapolis, IN

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298
FXUS63 KIND 211355
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
955 AM EDT Wed Jun 21 2017

.UPDATE...
The Near Term and AVIATION Sections have been updated below.

&&

.SYNOPSIS...
Issued at 251 AM EDT Wed Jun 21 2017

High pressure from Indiana to the southeast coast is going to rule
Hoosier weather through Thursday night. Friday we`ll be passed by a
cold front. Friday night high pressure should arrive from the
northwest.  The high is likely to dominate our weather for several
days as its center shifts to the eastern seaboard.

&&

.NEAR TERM (Rest of Today)...

Issued at 1000 AM EDT Wed Jun 21 2017

For the morning update, added isolated showers in the
north/northeast counties based on radar returns and satellite data
through 15z. Made some cloud cover adjustments for this morning to
go with clear/mostly clear skies over much of the area through the
morning before more cloud cover from diurnal cu develops. Over the
northeast increased cloud cover through the next hour or two based
on satellite data. Increased temperatures by a couple degrees based
on comparison with current obs and those yesterday in comparison to
yesterday`s highs along with a look at the bias corrected consensus
data for today. Previous discussion follows...

The main issue is POPS.

The models tend to agree today will be dry. They also agree a weak
boundary and some moisture will remain over the area, on the day
with literally the highest sun angle of the year. We currently
have more rain than there `should` be.

There will need to be an early morning period with relatively high
POPs. For the actual today period, the comparatively moist MET,
which gives a chance or slight chance in the areas with the most
moisture, will be used.  Skies should be partly cloudy under diurnal
cumulus.

Given low confidence about POPs, there is limited confidence about
temperatures. Consensus should minimize errors. These may be 2-3
degrees based on the range between different forecast methods.

&&

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

Issued at 251 AM EDT Wed Jun 21 2017

POPs are the main forecast problem.

The models agree in many ways. However we are going to be affected
by a tropical system from the Gulf--very atypical so early in the
summer. Such systems are notoriously challenging for the models.

Currently there is no reason to deviate from the consensus POPs.
These have precipitation likely by Friday, with drier weather
afterward. However confidence is the forecast is low. POPs may
need to be adjusted by 20 percent from those issued today.

As with POPs, there is no reason to vary from consensus with
temperatures, and confidence in them is low. Potential errors are
2-4 degrees.

&&

.LONG TERM /Saturday through Tuesday Night/...

Issued at 311 AM EDT Wed Jun 21 2017

Latest models have backed down on precipitation chances for the
weekend with central Indiana actually dry on Saturday. Friday`s
cold front is progged to be far enough south by Saturday to result
in a dry forecast. Sunday, there have been some model
inconsistencies in regard to showers and thunderstorms with an
upper wave skimming the northern portions of the area. For now,
latest Superblend initialization is trending toward a dry
forecast, and there is not enough support to deviate from that at
this time. Further out, a strengthening ridge over the Rockies
will result in dry conditions through the end of the extended
period. The only caveat may be some isolated showers on Tuesday
afternoon in association with a weak upper wave. As far as
temperatures, expect below normal numbers with a transition back
to a warming trend at the very end of the period.

&&

.AVIATION (Discussion for 211500Z TAFs)...

Issued at 955 AM EDT Wed Jun 21 2017

Updating current conditions only. Previous discussion follows...

Surface high pressure should results in either no ceilings or
ceilings above 10 thousand feet. There may be scattered diurnal
cumulus around 4 thousand feet. Winds should be mainly southwest 5-
10 knots.

&&

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

$$

SYNOPSIS...JK
NEAR TERM...JK/CP
SHORT TERM...JK
LONG TERM....TDUD
AVIATION...JK/CP



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