Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 220646
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
246 AM EDT FRI JUL 22 2016

.UPDATE...
The LONG TERM Section has been updated below.

&&

.SYNOPSIS...
Issued at 209 AM EDT Fri Jul 22 2016

Hot and Humid weather is expected to persist through the weekend
due to strong high pressure over the Central Plains and very humid
air over the Ohio Valley. The heat and humidity will lead to heat
index values between 105 and 110 on Friday and Saturday.

An upper level weather disturbance may arrive in the area on late
Friday or early Saturday...providing some relief in the way of
Thunderstorms. Relatively cooler weather is expected to arrive on
Monday along with more showers and storms as a cold front arrives
in the area.

Dry weather is expected after Monday as High pressure arrives in
the area along with typical Indiana summer time temperatures.

&&

.NEAR TERM /Today/...

Issued at 209 AM EDT Fri Jul 22 2016

Radar shows a dying thunderstorm complex over NW Indiana and NRN
Illinois..drifting southward. Surface analysis shows high pressure
in place across Missouri and Arkansas with a ridge axis extending
NE into the Ohio Valley. Terrible dew points in the middle and
upper 70s were in place across Central Indiana...amid weak
southerly Surface flow.

Nam fails to recognize ongoing convection to the northwest. That
is all I am gonna say about the NAM. Propagation thicknesses
suggest the convective cluster will continue to drift south and
should wane in intensity as is typical at this time of night.
Cloud tops appear to be warming already. This will set the stage
for a cloudy start across Central Indiana as this system
dissipated through the morning hours. The heat will then be on
this afternoon as full sun returns. Dew points in the upper 70s
are gonna make you sweat. Forecast soundings show plenty of CAPE
this afternoon with convective temperatures again near 90. Based
upon persistence...Highs near 90 should be easily reached. Thus
cannot rule out afternoons showers and storms...and Central
Indiana remains on the edge of the broad ring of fire as seen on
water vapor imagery. Thus will try and keep a dry period in
forecast during the late morning hours...followed by chances for
precip to return by late afternoon.

Heat advisory still looks reasonable given the very high and
downright oppressive dew points.

&&

.SHORT TERM /Tonight through Sunday Night/...

Issued at 209 AM EDT Fri Jul 22 2016

GFS keeps the moist anti-cyclonic flow across the Central Plains
and Indiana tonight...this time bringing upper
support...depicting a weak shirt wave passing within the flow.
Forecast soundings again hint toward saturation...and with the
very warm and very moist air mass in place...again thunderstorms
cannot be ruled out. CAPE tonight is well over 2000
j/kg...providing plenty of potential. Again with little chance in
the air mass...but potential for rain...will trend lows into the
lower 70s...due to expected rain cooled air.

More of the same looks in store for Saturday and Sunday. Forecast
soundings on each of those days show very high CAPE over 3000
j/kg along with attainable convective temperatures. Aloft the gFS
continues to suggest several short waves pushing across the upper
midwest and into Indiana. This should lead to ideal triggering
mechanisms for storms. Pwats remains very high as you would expect
with air mass...near or above 2 inches. Thus heavy rains will be
possible with any storms that do develop.

The best short wave of the bunch appears to pass on Sunday and
Sunday night along with a cold front that looks to push out of the
upper midwest into the Great Lakes and Indiana. Again...little
change in the air mass remains in place ahead of the front and
plenty of moisture...heat and instability should be in place. Thus
will again trend pops highs on Sunday and Sunday night as these
features pass.

As for temps through Sunday...will continue with a persistence
type forecast as there is not much change in the air mass. May
trend overnight lows slightly cooler due to possible overnight
rains and rain cooled air.

&&

.LONG TERM /Monday through Thursday/...

Issued at 237 AM EDT Fri Jul 22 2016

The long term forecast for central Indiana is characterized by a
retrograding upper ridge. This will allow for temperatures to cool
a bit from where they are now returning closer to normal for this
time of year. The aforementioned shift westward of the upper
ridge will also allow shortwaves to move through the upper
pattern and bring off and on thunderstorm chances to the area in
the northwest flow.

On Monday a cold front moving through the area will bring shower
and thunderstorm chances, and in its wake slightly cooler and
drier air will arrive. Tuesday into Wednesday should be dry, but
then thunderstorm chances ramp up as a frontal system approaches
for the latter half of the week.

&&

.AVIATION /Discussion for the 220600Z TAFS/...

Issued at 1230 AM EDT Fri Jul 22 2016

Large convective complex with a well established cool pool, currently
dropping south southeast through northern Illinois and northwest Indiana.
The presence of the cool pool and 25 kts of flow in the 925-850mb layer
suggests convective threat will be rather high at the terminals later
tonight. This threat will probably linger well past sunrise Friday with
potential elevated development over the cool pool. Brief IFR visibility
restrictions and gusty shifting winds in and near heavier convective
cells. CB bases 030-040.

Outside of convective areas, threat for visibility restrictions in fog
overnight exists given the high dewpoints, but don`t think fog will become
too thick or widespread due to convection keeping the air mass mixed up.
Light surface winds overnight expected to become 220-250 degrees at 8-12 kts
by early afternoon Friday.


&&

.IND Watches/Warnings/Advisories...
Heat Advisory from 10 AM this morning to 8 PM EDT Saturday for
INZ021-028>031-035>049-051>057-060>065-067>072.

&&

$$

SYNOPSIS...PUMA
NEAR TERM...PUMA
SHORT TERM...PUMA
LONG TERM....CP
AVIATION...JAS/CP


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