Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 221432

Area Forecast Discussion
National Weather Service Northern Indiana
1032 AM EDT FRI JUL 22 2016

Issued at 354 AM EDT Fri Jul 22 2016

A strong high pressure system centered off the mid Atlantic coast
will continue to cause a southerly flow of hot and humid
air across our area today. A weak cold front will move south
across lower Michigan today and into northern portions of Indiana
and Ohio tonight, possibly causing scattered thunderstorms in our
area. Highs today will be in the lower 90s, which combined with
the high humidity, will result in heat index readings over 100
across much of the area. Lows tonight are expected to be in the
upper 60s and lower 70s.


Issued at 1018 AM EDT Fri Jul 22 2016

Old remnant convective vort associated with thunderstorms last
night will continue to slowly sag southeast out of the forecast
area through midday. A few showers may persist across southern NW
Ohio counties over the next hour or two before this vort departs.
Otherwise, relative stable bubble induced from yesterday`s storms
should cap additional development through at least the early to
mid afternoon hours. Debris high clouds should continue to thin
across the area allowing for good surface warming into the lower
90s. Sfc dew points remain an item of slightly lower confidence
however. Aforementioned stable bubble has allowed for dew points
to drop into the upper 60s to around 70 across much of the
forecast area this morning, except for the far southeast which
remains on the more unstable side of the residual outflow
boundary. This could yield some slightly lower heat indices than
currently forecasted, but likely well into the advisory range
nonetheless. Expecting some upward creep of dew points today and
will not make major modifications to going forecast of 100 to 105
heat indices.

Did slightly lower PoPs this afternoon due to the potential of a
weak cap persisting. Triggering mechanism will also be somewhat
nebulous with difficulty in picking up any significant upstream
waves, and a relatively weak nature of a frontal boundary dropping
across the southern Great Lakes. Will maintain 20 PoPs for the
afternoon hours, with continued low end concern for an isolated
strong storm if convective inhibition issues can be overcome this
afternoon. SPC has removed much of the area from Day 1 Marginal
Risk based on above trends, except for the far southeast which
appears to be not as influenced by the early morning outflow.


.SHORT TERM...(Today and Tonight)
Issued at 354 AM EDT Fri Jul 22 2016

Outflow boundary emanating from mcs dropping into central il/in this
morning was movg se across our cwa with so far no convective
response, as airmass apparently still stabilized from aftn/eve
convection. Convective debris cirrostratus canopy should gradually
diminish this morning allowing airmass to become very unstable,
although weakly capped, this aftn. Wk sfc boundary associated with
shrtwv movg ese across srn ontario/swrn quebec will drop south into
this unstable airmass this aftn, psbly triggering sct tstms and with
wk synoptic flow/very unstable airmass in place, suspect this
activity if it does occur will linger into tonight along frontal
convergence zone and other outflow boundaries. Given the very
unstable airmass with wk deep layer shear in place, an isolated
severe storm is psbl. Temps should be a few degrees warmer than yday
with more aftn sunshine. This combined with a little higher dwpts
should result in heat index readings above our advisory criteria
(around 100). No sgfnt relief from heat tonight as abundant low
level moisture holds temps in the 70s.


.LONG TERM...(Saturday through Thursday)
Issued at 354 AM EDT Fri Jul 22 2016

The weak frontal boundary is expected to stall out over our cwa
Saturday and then lift n-ne Sat ngt as a seasonably strong shrtwv
and associated sfc low/cdfnt move east across srn sask/manitoba and
the daks. Airmass will remain very moist/unstable but bufr soundings
suggest a little stronger capping around 5kft so kept pops low. A
little drier air north of the stalled frontal boundary should allow
for heat index readings to be blo advisory criteria across nrn
portion of the cwa with heat index around 100 contg to the south.

Tstms chances increase a bit Sunday/Sunday night as plains
shrtwv/cdfnt moves into the upr grtlks. Cdfnt should still be movg
across the sern portion of the cwa Monday continuing the threat of
tstms in that area. By Tuesday, post-frontal high pressure
expected to build in providing a couple of days with lower
humidity and slightly cooler temps.


.AVIATION...(For the 12Z TAFS through 12Z Saturday Morning)
Issued at 653 AM EDT Fri Jul 22 2016

Stable airmass in place in wake of late evening convection should
keep any storms at bay until at least afternoon. Extensive cirrus
shield and some patchy lower clouds should erode through the day.
Variable wind direction at KFWA will steady out back to more SW
over the next hour or 2 as meso low pushes away.

Chances for storms exists after 18z as unstable atmosphere and
approach of frontal boundary may trigger a few storms. Have left
VCTS in the forecast through 00Z before conditions stabilize.


.IWX Watches/Warnings/Advisories...
IN...Heat Advisory until 8 PM EDT /7 PM CDT/ Saturday for INZ003>009-

MI...Heat Advisory until 8 PM EDT this evening for MIZ077>081.

OH...Heat Advisory until 8 PM EDT Saturday for OHZ001-002-004-005-015-




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