Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 210223
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1023 PM EDT Sat Jul 20 2019

.UPDATE...
The AVIATION section has been updated below.

&&

.SYNOPSIS...
Issued at 443 PM EDT Sat Jul 20 2019

The high heat and humidity continues for one more day before a
cold front pushes through the forecast area Sunday and Sunday
night. This front interacting with the high heat and humidity with
produce some showers and thunderstorms along and ahead of the
front. Much cooler conditions and lower humidity will push into
the area behind the front...allowing for temperatures some 5 to 10
degrees below normal Monday and Tuesday.

&&

.NEAR TERM /Rest of Tonight/...
Issued at 937 PM EDT Sat Jul 20 2019

Forecast is in good shape. Thunderstorms across northern Indiana
are dying. The outflow boundary from them continues to sink toward
the northern forecast area. It may enter that area, but with a cap
overhead and decreasing instability, do not think any convection
will form.

Tweaked hourly parameters, but no significant changes were made to
the forecast.

Previous discussion follows...

Confidence not high in seeing much in the way of precipitation
tonight. Diurnal CU is currently struggling to break through a cap
in the 700-850mb layer. The best chance looks to be across the
northwest during the early morning hours. However, the one caveat
to this will be any potential outflow boundary pushing south into
central Indiana from a couple complexes of storms currently
pushing east from Wisconsin into lower Michigan. Confidence not
high enough in this possibility to include POPs. Removed the
slight chance POP over the northern tier of counties for this
evening and returned the slight chances across the far northwest
counties around 11Z with the approach of a cold front and upper
disturbance from the northwest.

&&

.SHORT TERM /Sunday through Tuesday/...
Issued at 443 PM EDT Sat Jul 20 2019

Low to mid 90 degree heat with heat indices from 100 to 105
continues to be expected for Sunday. An unsettled beginning
portion of the short term forecast is expected as a cold front and
upper trough pushes toward central Indiana from the northwest.
GFS and ECMWF are in good agreement with respect to the passage of
this cold front. Shower and thunderstorm chances will increase
starting in the northwest first Sunday morning and then spread
south and east through Sunday night.

With the cold front moving through the hot and humid airmass we
have currently over the area...widespread thunderstorms are
expected Sunday and Sunday night. With instability progged to max
at 2000 to 2500 J/kg tomorrow afternoon...a few storms could be
strong to severe. The limiting factor to more widespread severe
looks to be the marginal shear across the forecast area. Thus, SPC
has the forecast area within the Day 2 Marginal Risk for the
severe weather.

Behind the front, high pressure moves our way from
Canada...bringing much cooler temperatures with lower humidities
to start the work week. Temps some 5 to 10 degrees below normal
are expected to end the short term period.

&&

.LONG TERM /Tuesday Night through Saturday/...
Issued at 310 PM EDT Sat Jul 20 2019

Fantastic weather is expected throughout the extended period next
week. Broad high pressure at the surface will expand into the
area for much of next week with upper level heights cooling as the
strong ridge aloft shifts west into the Rockies and Intermountain
West. This will result in several days with dry and seasonable
weather...highlighted by mainly sunny pleasant days and clear
comfortable nights. Dewpoints will nosedive into the 50s by
Tuesday evening and Wednesday before slowly climbing back into
the lower 60s by next weekend. Highs will slip back to the low 80s
before gradually warming into the mid 80s by Friday and Saturday.

Extended models hinting of a cold front impacting the region at
some point next weekend which will once again bring in a cooler
airmass for the beginning of the last week of July. Storm impacts
with this front likely to be just outside the 7 day forecast.

&&

.AVIATION (Discussion for the 210300Z TAF Update)...
Issued at 1023 PM EDT Sat Jul 20 2019

Minor tweaks made to reflect current obs.

Previous discussion follows...

VFR conditions expected most of the period, with some convection
possible by Sunday afternoon.

Cumulus clouds will dissipate this evening. Will have to watch an
outflow boundary across northern Indiana to see how far south it
gets. If it makes it into central Indiana there may be a wind shift
this evening at KLAF. However, odds are against it generating
convection with a cap in place over the TAF sites.

Expect an increase in mid and high clouds overnight into Sunday as
dying convection approaches the area. There may be a few leftover
showers in the morning from this. Better chances for convection will
arrive in Sunday afternoon as a front moves into the area.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 8 PM EDT Sunday for INZ021-028>031-
035>049-051>057-060>065-067>072.

&&

$$

SYNOPSIS...MRD
NEAR TERM...MRD/50
SHORT TERM...MRD
LONG TERM....Ryan
AVIATION...50


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