Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 251014

Area Forecast Discussion
National Weather Service Indianapolis IN
614 AM EDT Tue Jul 25 2017

The AVIATION Section has been updated below.


Issued at 153 AM EDT Tue Jul 25 2017

High pressure will dominate Indiana weather into Wednesday night as
its center travels from the Great Lakes to the eastern seaboard. A
cold front is forecast to cross our state Thursday and Thursday
night. Another high pressure system following the cold front should
remain over the central parts of the USA and Canada into the middle
of next week.


.NEAR TERM (Today)...

Issued at 153 AM EDT Tue Jul 25 2017

There are no true forecast problems. Model agreement is strong
high pressure will provide mostly clear skies. Guidance is also
close on temperatures, which should be a few degrees below
seasonal. Expect errors of 2 degrees or less.


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

Issued at 153 AM EDT Tue Jul 25 2017

With good model agreement about mostly clear skies through
Wednesday, the forecast problem is rain chances later in the period.

There is little doubt it will rain as a surface low crosses the
state. Timing is uncertain. Some models, such as the NAM, have
the event well underway by late Wednesday night. Other models,
like the GFS, delay the most significant weather until during the
day Thursday. For the present consensus POPs are the best way to
reduce uncertainty.

All the models have near record precipitable water at times. It`s
just a matter of exactly when. Heavy rain will be in the forecast
wherever POPs are 60 percent or higher.

Confidence in the temperature forecast is high into tomorrow night,
with potential errors 2 degrees or less. Confidence drops
considerably later since the precipitation forecast is uncertain.
Potential errors are 2-4 degrees.


.LONG TERM /Friday through Monday/...
Issued at 225 AM EDT Tue Jul 25 2017

The storm system and frontal boundary that will be responsible for
the heavy rain and storms late Wednesday night through Thursday
will be departing from the region by early Friday with a broad
area of high pressure expanding into the Ohio Valley and lower
Great Lakes in its wake. The result will be dry and seasonable
weather through much of the extended period. High confidence
exists for most of the forecast period.

The upper ridge which has been a persistent feature for much of
the month over the central U S will retrograde into the
Intermountain West through the weekend with a mean upper trough
over much of the country east of the Mississippi River. This will
leave the region within a dry northerly flow producing spectacular
yet slightly cooler than normal temperatures for late July. Expect
highs ranging from the upper 70s and lower 80s this weekend
gradually warming into the lower and middle 80s for early next
week. Lows in the 50s to low 60s will be common with low humidity
throughout much of the period.

ECMWF in particular hinting at a weakness developing within the
upper trough over the Tennessee and lower Ohio Valleys by Monday.
While confidence is low in this feature developing...could see
isolated convection generated by Monday and Tuesday as low level
moisture advects back into the forecast area and interacts with
the energy aloft.


.AVIATION /Discussion for 251200Z TAF Issuance/...
Issued at 614 AM EDT Tue Jul 25 2017

VFR conditions expected throughout the forecast period.

Picture perfect day for central Indiana with high pressure across
the region. Expect mainly clear skies through tonight with just a
few cirrus. Unreachable convective temperatures and plenty of dry
air and subsidence through the boundary layer should limit most if
not all diurnal cu. Wind direction will largely be easterly
through the period.





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