067 
FXUS63 KIND 052321
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
721 PM EDT Tue Oct 5 2021

...Updated Aviation Discussion...

.Short Term...(This Evening through Wednesday Night)
Issued at 235 PM EDT Tue Oct 5 2021

Low stratus continues to lift and mix out into a cu field this 
afternoon as the shallow inversion that aided in the fog and low 
clouds this morning has dissipated. few light showers and sprinkles 
are drifting west across the northern Wabash Valley...otherwise it 
was dry across central Indiana. 1830Z temperatures were in the 70s.

The brief break from the unsettled wet weather will continue into 
this evening before shifting back to increasing chances for rain 
late tonight through much of the rest of the work week. Axis of 
drier air has spread across the region this afternoon between the 
leftover moisture just to the northwest of the region and the 
expanding area of deeper Gulf moisture lifting north into the 
Tennessee Valley on the east side of the upper low over the lower 
Mississippi Valley. That moisture will continue to move N/NW into 
the Ohio Valley tonight in tandem with an inverted surface trough 
that will lift north across the area Wednesday as weak surface waves 
drift north through the Ozarks. The upper low will begin to lift 
northward as well...eventually reaching central Missouri by Thursday 
morning. 

The combination of the surface boundary moving into the region and 
the upper low lifting north as well will be a resumption of the 
wetter and more unsettled weather experienced Saturday through 
Monday across central Indiana. The initial surge of lift and deeper 
moisture will track into southern Indiana tonight and bring an 
increasing threat for scattered showers to the southwest half of the 
forecast area. Greatest rainfall coverage though is likely to focus 
just to the southwest of the forecast area late tonight in the 
vicinity of a low level jet that sets up from middle Tennessee 
northwest into southern Illinois. A low level convergence axis will 
lift north in tandem with the jet and will enable numerous showers 
and a few storms to expand into the southern counties towards 
daybreak Wednesday.

Scattered showers will continue to expand across the entire forecast 
area on Wednesday as the surface boundary lifts through the 
region...but the absence of more substantial low level lift suggests 
precip coverage will most likely remain scattered at best throughout 
the day. Weak elevated instability should be enough to generate a 
few lightning strikes...especially Wednesday afternoon and evening. 
An increase in forcing aloft along with hints of a reestablishing 
low level jet nosing into the region should bring more widespread 
showers and perhaps a continued threat for an isolated 
thunderstorm Wednesday night. 

Temps...low level thermals support undercutting guidance by a few 
degrees Wednesday...especially with clouds and scattered convection 
present. Expect generally mid 70s for highs. Lows tonight and 
Wednesday night will drop into the lower and mid 60s.

&&

.Long Term...(Thursday through Tuesday)
Issued at 235 PM EDT Tue Oct 5 2021

Active but wet pattern ahead.

Thursday through Friday Night...

ECMWF shows a negatively tilted upper low pushing from MO to the 
Great Lakes on Thursday through Saturday morning...with an 
associated upper trough axis pushing across Indiana. A warm front is 
depicted to push across Indiana during this time also. Forecast 
soundings show a deeply saturated column on Thursday Morning...and 
again on Thursday Night as forcing features are expected to pass 
aloft. Pwats are suggested to be near 1.55in and 1.39in at those 
times respectively. Forecast soundings only begin to show subsidence 
arriving by Friday afternoon as the column begins to dry out. It is 
at this time on Friday when the upper trough begins to exit to the 
north...allowing ridging over the plains states to build toward 
Indiana. Thus will keep rather high pops on Thursday through Friday 
morning...trending lower by Friday afternoon.

Saturday and Sunday...

Models suggest weak ridging in place aloft during this time as the 
next short wave begins to push into the northern plains. SW flow 
looks to remain in place aloft ahead of this trough...but best 
forcing should remain west of Indiana until Sunday night. Forecast 
soundings show a dry column for Saturday and Sunday. Warm SW flow 
will be in place within the lower levels with a thermal ridge in 
place across MO to Central IL and western Indiana on Sunday, with 
850mb temps soaring near 18C. Thus will expect dry...warm and breezy 
weather this weekend. Temps should be well above normal.

Monday and Tuesday...

Models show a strong short wave stretching from the western Great 
Lakes to Central MO...poised to push across Central Indiana on 
Monday. Strong dynamics will be in place as the trough axis pushes 
across Indiana on Monday. Meanwhile within the lower levels a strong 
cold front is expected to pass on Monday afternoon. Forecast 
soundings show good moisture present at that time within the warm 
sector ahead of the front and pwats are suggested to be near 1.53in. 
The column is expected to begin to dry out on Monday night in the 
wake of the front. By Tuesday afternoon...the forecast soundings are 
dry with westerly surface flow in place. Surface high pressure south 
of Indiana should be in place at that time. Thus will keep chances 
for rain on Monday...but will trend toward a dry forecast by Tuesday 
with cooler temperatures.

&&

.Aviation...(00Z TAF Issuance)
Issued at 720 PM EDT Tue Oct 5 2021

IMPACTS:
- VFR conditions expected through the overnight, with scattered 
showers arriving from the south sometime after 6z. 
- MVFR ceilings return at KLAF after 8z and other sites after a few 
more hours.
  
DISCUSSION: An upper low meandering around south of here will bring 
some showers and potential for a few rumbles of thunder late during 
the overnight hours. Ceilings will drop to MVFR as low level 
moisture and forcing increase during the early morning hours. 
Scattered showers should continue through much of Wednesday, and 
ceilings could stay restricted until late afternoon. Winds will be 
northeasterly around 5 to 8 kts overnight, and become southeasterly 
around 6 to 10 kts Wednesday.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

Short Term...Ryan
Long Term...Puma
Aviation...CP