Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 231859

Area Forecast Discussion
National Weather Service Indianapolis IN
259 PM EDT Sat Sep 23 2023

.Short Term...(This evening through Sunday)
Issued at 258 PM EDT Sat Sep 23 2023

- Mostly clear and pleasant overnight
- Mostly sunny and warm on Sunday

Surface analysis early this afternoon continued to show a ridge of
high pressure across Indiana, stretching south across Indiana. This
high pressure system was centered over Quebec and Ontario. Aloft a
ridge axis is shown to stretch from the southern plains across the
mid-Mississippi Valley, across Indiana to the Great Lakes. This was
resulting in subsidence across the area. Windward side flow on this
ridge was pushing clouds and precip associated with low pressure
over the plains states north and staying west of Indiana. Strong
surface low pressure was found over NC/VA.  GOES16 shows clear skies
across Indiana as subsidence was in place under the ridge aloft. Dew
points were quite dry in the 40s.


Little change is expected in the overall pattern. Models continue to
show subsidence and a dry column in place overnight as Indiana will
remain under the influence of the surface high pressure system and
the ridging aloft. Forecast soundings remain dry. Some weak cold air
advection today will allow for slightly cooler low temperatures
tonight. Thus expect clear and pleasant conditions with lows in the
lower 50s.


Slight changes begin to take shape in our weather pattern on Sunday,
but overall, this will have little overall impact on the sensible
weather. The upper ridge is depicted to drift east  of Indiana along
with the inverted surface ridge of high pressure.This will allow the
upper low over the western plains to drift to the upper midwest
along with its associated surface low.  All of this will result in a
more southerly component to surface winds on Sunday, allowing for
slightly warmer high temperatures in the lower and middle 80s.
Again, forecast soundings and time heights show a dry column with
unreachable high temperatures. Thus, mostly sunny and warm.


.Long Term...(Sunday night through Saturday)
Issued at 258 PM EDT Sat Sep 23 2023

Building surface high pressure across eastern Canada will promote
generally easterly flow for the first half of the coming week.
Currently, flow is out of the northeast and is quite dry with dew
points in the mid 40s. Low-level moisture may increase somewhat in
the days ahead as moisture from Tropical Storm Ophelia is sent
westward. The increased moisture should allow fire weather
conditions to improve somewhat.

Meanwhile, to our west, a closed low over the northern Plains should
weaken through tomorrow. Guidance largely depicts this feature
remaining cut off from the mid-latitude westerlies and drifting
southeastward. That should bring the system over Indiana by late
Tuesday, albeit with further weakening. Some showers may arrive well-
ahead of the core of the closed low late Sunday night or early
Monday...but these should be few and far between and mainly near the
Illinois border.

There remains some discrepancies within guidance regarding the
strength of the closed low. Additionally, low-level forcing appears
weak with only modest upper-level support. Nevertheless, enough
instability and forcing should be present for scattered showers and
thunderstorms. Will plan on capping PoPs at chance for now given the
above. Shear appears weak as well, so any storms that develop should
be pulse or loosely organized clusters with low severe potential.

With the closed low overhead or nearby, along with prolonged cloud
cover...moderated temperature are expected this week. The diurnal
curve will be flattened somewhat with highs in the mid 70s and lows
near 60. These values are still within the seasonable range for this
time of year.

By late in the week/next weekend our closed low should be out of the
area, with renewed ridging over the Plains. Some hints in guidance
of residual troughing to our east prompting a return to easterly low-
level flow. Ensemble guidance diverges quite a bit, however, so
forecast confidence decreases. Nevertheless, improving weather
currently appears to be the most likely scenario given the exit of
the mid-week closed low.


.Aviation...(12Z TAF Issuance)
Issued at 1130 AM EDT Sat Sep 23 2023


* VFR Conditions are expected


VFR conditions are expected to persist as high pressure and ridging
aloft are expected to remain across the TAF sites through the
period. This will continue to result in light east to southeast
winds and mostly clear skies. Forecast soundings and time heights
continue to show a dry column through the period.

Dew point depressions tonight are expected to fall to 3-7F. This may
result in a few areas of patchy shallow fog, but confidence for a
mention at this point is too low.





Short Term...Puma
Long Term...Eckhoff
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