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Area forecast discussion 
National Weather Service Indianapolis in
433 PM EDT Tuesday Sep 2 2014

the aviation section has been updated below.


issued at 332 PM EDT Tuesday Sep 2 2014

Calm weather will prevail through tomorrow as high pressure
strengthens at the surface. However...there will be some chances
for showers and thunderstorms throughout the forecast period as a
warm front moves through central Indiana at the end of the week...
quickly followed by a cold front on Friday night and Saturday.


Near term /tonight/...

Issued at 332 PM EDT Tuesday Sep 2 2014

Remnant showers and thunderstorms are currently lingering over
the far southeast counties closest to frontal boundary that
recently moved through central Indiana. Elsewhere...the remainder
of central Indiana is currently dry with just some isolated
development to the northwest of Lafayette. Still expect clearing
tonight though as drier air filters into the forecast area. This
combined with lingering low level moisture and light winds will
create the possibility for patchy fog development.

Temperatures tonight will drop into the low to middle 60s with the clearing
skies. This was captured best by the cooler GFS. Some of the
northern counties may even dip into the upper 50s...this will have
to be monitored through the course of the evening.


Short term /tomorrow through Friday/...

Issued at 332 PM EDT Tuesday Sep 2 2014

The main focus of the short term period is shower/thunderstorm
chances on Thursday and Friday.

Zonal flow aloft and high pressure at the surface will result in
dry conditions tomorrow and tomorrow night. Focus then turns to
Thursday when significant warm air advection with southwesterly
flow will provide an unstable environment for diurnal thunderstorm
activity. At this time...the models are struggling a bit in regard
to Thursday/S forecast. The GFS seems to be overdoing convective
chances for Thursday...but the NAM and Euro are trending toward a
dry forecast. For now...will cover this discrepancy with slight
chance probability of precipitation to account for any pop-up diurnally driven activity on
Thursday afternoon.

Friday...high confidence forecast in regard to probability of precipitation as a cold
front moves through the area...will cover with chance probability of precipitation for
now...but these will most likely be increased to likely in future
forecast issuances.

Temperatures...models have a good handle on the weak warming went
with allblend for the entire period.


Long term /Friday night through Tuesday/...

Issued at 332 PM EDT Tuesday Sep 2 2014

Broad ridge aloft will buckle at the end of the week in response to
an upper trough amplifying across the northern plains. This will
enable a cold front to drop south across the Ohio Valley Friday
night and Saturday with rain and thunderstorms impacting the
forecast area. Will continue with high chance probability of precipitation through Saturday.

The front will shift south of the Ohio River Saturday night with
strong high pressure building across the region for much of the
remainder of the extended period as it drifts slowly east into New
England. High temperatures will fall back into the 70s Sunday and Monday
with overnight lows the coolest seen in the region since the middle
of August...ranging from the upper 40s to middle 50s. Return flow on
the back side of the high will bring scattered convection back north
into the Ohio Valley by midweek along with a warming trend.


Aviation /discussion for 022100z taf issuance/...
issued at 433 PM EDT Tuesday Sep 2 2014

Added a brief tempo group for MVFR conditions with shower just
upstream of klaf. Otherwise updated current conditions as ceilings
have lifted to VFR at the sites.

Fog producing sub IFR conditions possible late tonight/early

Skies will become mostly clear later evening with high pressure
building across the Ohio Valley. West/northwest winds up to 10kts are expected
through 00z.

The main issue for the rest of the forecast period is expectation
for fog development after 06z with clear skies...light winds and
shallow moisture still present near the ground. Potential for
visibilities to 1sm or less at outlying terminals...with thickest
fog at kbmg where the most rain has fallen since last night. Even
kind should see at least a period with MVFR visibilities and
possibly lower. Fog will burn off by middle morning Wednesday with
light southerly winds and a few cumulus developing midday.


Ind watches/warnings/advisories...none.



near term...tdud
short term...tdud
long term....Ryan

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