Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 211736

Area Forecast Discussion
National Weather Service Indianapolis IN
136 PM EDT Fri Apr 21 2017

The SYNOPSIS Section has been updated below.


Issued at 130 PM EDT Fri Apr 21 2017

High pressure over the Dakotas will give way to a developing storm
system over the southern High Plains in the next 12-24 hours.
mid/upper level jet steam is extending south/southeast over the
Rockies and will extend eastward across the southern Plains/lower
MS Valley tonight. That will develop a positively tilted trough
over the lower MS Valley and associated surface low along the
quasistationary front that extends east/northeast across southern
and east central KY. Low pressure will move along this frontal
boundary over the next 24-36 hours and spread rain/rainshowers
across mainly the southern half of IN as early as tonight and
likely Saturday.


.NEAR TERM /Rest of Today/...

Issued at 928 AM EDT Fri Apr 21 2017

Morning surface analysis shows frontal boundary that moved
through central IN last evening is now extending from southwest PA
southwest through southwest AR. Still have plenty of cloud cover
spreading northeast from a thunderstom complex over northern
AR/southern MO. May still be able to see some breaks in this cloud
cover into early this afternoon due to surface high pressure over
the Dakotas that extends into the area. Cloud cover/cooler air
mass over the area should keep temperatures in the upper 50`s/low
60s today. Thermal gradient at 850 mb extends across central IN
will play role in tracking activity over AR/MO northeast possibly
spreading some rain over southern IN this afternoon slowly
northward into parts of central IN by this evening.


.SHORT TERM (Saturday through Sunday night)...

Issued at 257 AM EDT Fri Apr 21 2017

The main issue is when rain will end.

The latest background models are close. They take the low pressure
that will bring rain chances farther south than previously. Given
they agree, the trend is probably good. The earlier forecasts used
in the Superblend consensus are likely an undesirable influence.
Lowering consensus POPs should improve them. The forecast will have
no POPs above the likely category, and rain over by 18Z Sunday.

With a strong moisture gradient over the CWA skies ought to be
mostly clear north and mostly cloudy south through Sunday, then
clear everywhere.

There is a little uncertainty about temperatures, which will be
sensitive to how much sky cover there is and just where rain falls.
However, considering good model agreement about the underlying
thermal fields, the consensus forecast should be accurate to within
a few degrees.


.LONG TERM /Monday through Thursday/...

Issued at 237 AM EDT Fri Apr 21 2017

The long term will start out dry with upper ridging sliding across
the area. Temperatures will warm to above normal Monday with highs
in the upper 60s to lower 70s with sunshine. Temperatures will get
even warmer after that as southwesterly surface flow develops. By
Tuesday night chances for rain will move into the area as a
frontal system approaches and moves through the area. Models are
in agreement that this front will stall somewhere in the Ohio
Valley vicinity, but not great agreement on where which is to be
expected this far out. Thus should see off and on chances for rain
and some thunderstorms from Tuesday night through Thursday. At
this point with the variability in frontal position and resultant
differences in moisture don`t see a need to adjust from
initialization pops running as high as mid range chances with some
potential for mainly isolated thunderstorms Tuesday night through
Wednesday night. Highs from Tuesday through Thursday should be in
the mid 70s to lower 80s with low sin the 50s and low 60s.


.AVIATION /Discussion for 21/18Z TAF Issuance/...

Issued at 1244 PM EDT Fri Apr 21 2017

High pressure over the Dakotas extends southeast into IN for this
afternoon. Clouds are spreading east/northeast embedded in the
mid/upper level flow from OK into the region. A mid/upper level
trough over W TX will move east/northeast over the next 24 hours
and is expected to spread light rain over at least the southern
third of IN, including KBMG, KHUF, and possibly KIND during the
morning hours Saturday. Thus, expect mostly VFR through this
afternoon with an ocasional MVFR south, becoming MVFR with
occasional IFR Saturday morning across the southern half of IN.




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