Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 221026

Area Forecast Discussion
National Weather Service Indianapolis IN
626 AM EDT Sun Apr 22 2018

The AVIATION section has been updated below.


Issued at 342 AM EDT Sun Apr 22 2018

More clouds are in store for central Indiana for the next few days
along with increasing chances for showers as low pressure moves from
the plains through the Tennessee and Ohio valleys. A couple of upper
waves and associated frontal systems will move through the area late
in the week to bring more chances for rain to the area.


.NEAR TERM /Today/...

Issued at 342 AM EDT Sun Apr 22 2018

Low pressure will approach from the southwest and keep mostly
cloudy to cloudy skies over central Indiana today. Even with this,
with warm 850 temperatures expect to see highs similar to/a bit
warmer than yesterday. Dry easterly component flow will continue to
inhibit the northward progression of any measurable precipitation
through the day today, and only bring in a slight chance for showers
in the far southwestern counties in the late afternoon. Can`t rule
out some sprinkles before then, but even these should be few and far
between given the dry surface air.


.SHORT TERM /Tonight through Tuesday night/...

Issued at 342 AM EDT Sun Apr 22 2018

An upper low and surface low are progged to stack over western
Tennessee tonight and then slowly make their way northeastward
through Kentucky and off to West Virginia during the short term.
This will bring increasing chances for rain showers, with the
highest chances on Monday in the area of best forcing northeast of
the low. Probabilities will remain high in the eastern counties into
Tuesday as the low gets east of the area. With the upper low to the
south and cloudy skies high temperatures will be a bit depressed on
Monday and Tuesday, hanging around in the upper 50s to lower 60s.
Highest rainfall amounts should be in the southern/southeastern
counties during the short term, but even those should only be around
half an inch. Continuing to keep thunder out of the forecast during
this period due to lack of instability and paltry lapse rates.


.LONG TERM /Wednesday through Saturday/...
Issued at 315 AM EDT Sun Apr 22 2018

The main focus for the long term will be on timing of showers over
the area as a pair of waves move through the area in a mean eastern
trough regime.

Issues with model timing of various upper waves or lows over the
Great Lakes and Ohio in mean eastern trough lend low confidence in
model QPF timing and consequently in timing and coverage of PoPs
throughout the long term.

Models were showing a Great Lakes trough dropping southeast over the
area Wednesday. The 12z ECMWF and 00z CMC were faster than the 00z
GFS with this feature and would support low or no PoPs. The 00z GFS
would support higher PoPs. The new  ECMWF just came in closer to the
GFS, but still faster. With confidence low in a winner, low blend
PoPs will be accepted.

Then, a surface and upper ridge should allow for dry weather
Wednesday night and at least Thursday morning. After that, the 00z
GFS was much faster and further north with an upper system compared
to the slower 12z ECMWF and the slower and much further southern 00z
CMC. The 00z GFS brings QPF back across northwestern parts of the
forecast area Thursday afternoon, while the other models do not
bring any in until Thursday night /CMC/ or Friday /ECMWF/. The Blend
was closer to the GFS, with low PoPs northwest Thursday afternoon
and chance PoPs all areas by Thursday night. With it being the long
term and confidence not high in any one model, will accept the
Blend. Kept chance PoPs in through Friday night per the Blend. Then,
dry weather is expected the remainder of next weekend as an upper
ridge approaches.

With mean upper troughing, high confidence in below to slightly
below normal temperatures per the Blend.


.AVIATION /Discussion for the 221200Z TAF Issuance/...
Issued at 626 AM EDT Sun Apr 22 2018

High confidence that conditions will remain VFR through the period
at LAF and through 09z or so at the other sites. Then, the SREF
suggests ceilings will deteriorate to MVFR or possibly worse in

Winds will be 050-080 degrees at 5 to 10 knots.




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