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Area forecast discussion 
National Weather Service Indianapolis in
638 PM EDT Tuesday Aug 4 2015


The aviation section has been updated below.


issued at 310 PM EDT Tuesday Aug 4 2015

High pressure will provide dry conditions to much of central Indiana
into Wednesday morning...then an area of low pressure will bring
chances for rain later Wednesday through Thursday. A couple of
fronts will bring more chances for rain to parts of the area by the
second half of the weekend. Temperatures will generally be near to
below average.


Near term /tonight/...
issued at 310 PM EDT Tuesday Aug 4 2015

Generally more of the same in the forecast for tonight as a
nearly stationary front remains across southwest Kentucky.
Meanwhile central Indiana will remain in northwest flow aloft.

Models continue to indicate very weak chances for showers and
isolated thunderstorms to develop across the far
southwest/southern tier of counties through this evening. Even
though high pressure will continue to build over the region across
North Central Indiana...a few weak disturbances will move
southeast and may interact at times with the stalled boundary.
Left in 20-30 percent chances across the far south for the rest of
this afternoon through overnight.

A MOS blend for temperatures generally looks representative of
the expected conditions for lows in the low to middle 60s.


Short term /Wednesday through Friday/...
issued at 310 PM EDT Tuesday Aug 4 2015

Agree with previous forecast that Wednesday is still looking dry
for most of the central Indiana...which has been the trend for the
last few models runs. Kept low chance probability of precipitation across the southwest
corner of area...and not until the afternoon.

Models are not in as good agreement as they were 24 hours ago with
the upper trough and associated surface low projected to move
through the area Wednesday night through Thursday.

The GFS is definitely the outlier of the all the
takes this system well south of the area and keeps central Indiana
almost entirely dry during this period. The rest of the guidance
is hinting at a more southward trend...and thus higher quantitative precipitation forecast amounts
centered over portions of southern Indiana and Kentucky. Up to an
inch of rainfall is still possible in central Indiana...especially
for counties south of the I 70 corridor where the best moisture
and lift is expected to be. And even though convective development
is not expected to be as widespread...actually trended back
mention of thunderstorms to chance and slight chance (very little
to no instability over the area by early thursday)
important to remember any one thunderstorm can produce several
inches of rainfall over a given area when the precipitable waters
are still running very high at over 2 inches.

Left in likely to categorical probability of precipitation for all areas except for the
far northern few rows of counties based on this new southward
trend of the system. A Flash Flood Watch may need to be considered
for subsequent forecast issuances/updates for at least the counties
across the south...depending on how the models trend.

The system should be moving out of the area by Thursday night.
Tapered probability of precipitation from low chance to slight chance across the south
Thursday night...and then dry for Friday.

As for temperatures...went a little cooler than MOS for highs
and a little warmer than lows based on cloud cover and expected
precipitation chances for most days this period except for Friday. For
Friday a blend of MOS seems reasonable. Temperatures will
generally run a few degrees below normal through the entire


Long term /Friday night through Tuesday/...
issued at 157 PM EDT Tuesday Aug 4 2015

GFS and European model (ecmwf) continue to suggest strong ridging across the
Western Plains states and Rocky Mountains during this
period...resulting in a quick northwest flow aloft from Canada into the
Ohio Valley though this period. GFS brings several short waves
across central Indiana during this period...while the European model (ecmwf)
appears to be less robust. Thus confidence is low. One thing
remains more that Gulf moisture remains effectively
cut off. This should result in any rain events leaning toward the
lighter side of things. Given the northwest flow...have trended toward
cooler temperatures through the period. chances for precipitation appear to be on Monday as European model (ecmwf)
and GFS agree a surface cold front will push across the
state...providing good lower level convergence.


Aviation /discussion for the 05/00z tafs/...
issued at 638 PM EDT Tuesday Aug 4 2015

VFR throughout the period at ind...and the majority of the period at
the outlying sites. Some MVFR fog appears possible late tonight
through tomorrow morning.

Some middle and high cloud will generally be the only sky cover across
the area tonight into tomorrow. Winds appear likely to go light to
calm at the outlying sites. This should set the stage for MVFR fog
development. Ind will likely remain VFR or only see very patchy fog.

Winds will be less than 10kt throughout the period.


Ind watches/warnings/advisories...none.



near term...smf
short term...smf
long term...puma

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