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Area forecast discussion 
National Weather Service northern Indiana
327 am EDT Sat Sep 5 2015

issued at 318 am EDT Sat Sep 5 2015

The Labor Day weekend will be hot and humid...with afternoon heat
indices reaching the middle and upper 90s. There is a chance for
thunderstorms this afternoon and again on Labor Day. Highs will
be in the upper 80s and lower 90s...with overnight lows in the
upper 60s and lower 70s.


Short term...(today and tonight)
issued at 318 am EDT Sat Sep 5 2015

Persistent upper level circulation center is now located over
Southern Lake Michigan and does not appear to be making any big move
for the next 12 to 18 hours. This vortex has been the focus for
ongoin convection over the south-central portion of the County Warning Area and will
be the focus for later convective development today. While there are
difference between the models...all have narrow and focused areas of
cape for this afternoon...primarily centered near the center of the
middle level vortex. Expect to see afternoon convection with slow
moving storms and the greatest threat being localy heavy rainfall.

Models have been advertising for this shortwave/vortex to shift east
and exit the region for the past several runs and it does appear
that the latest runs are handling the flow pattern better. Water
vapor imagery does support the ridging over the plains shifting
eastward and aligns well with the current high resolution it appears that the vortex will linger for the day
before being sheared apart overnight tonight as the ridge flattens
slightly and shifts eastward.


Long term...(sunday through friday)
issued at 318 am EDT Sat Sep 5 2015

Hot and dry conditions still expected for Sunday as upper ridge
remains firmly established across the eastern Continental U.S. And pesky cutoff
low finally dissipates. Forecast soundings tell the story with very
warm (and relatively dry) profiles featuring a deep/well mixed
boundary layer. Mostly sunny skies should yield highs around 90f.
Surface dewpoints will be in the upper 60s to around 70f. This is
enough to generate heat indices in the middle 90s but instability is
still limited by poor midlevel lapse rates and hints of a capping
inversion. GFS soundings actually show very little surface-based
instability and are preferred over typically overzealous NAM
profiles. Regardless...lack of any synoptic forcing will make precipitation
difficult and silent 10 pop still preferred.

Frontal boundary extending from Canadian prairies height anomaly
begins to approach the area on Monday but remain highly skeptical of
how much progress it will make given lack of any substantive height
falls locally. Maintained low chance pop in our far northwest but
suspect most locations will remain dry through the day. This also
allows for at least one more day of temperatures near 90f (away from the
lake). Clouds will be on the increase but enhanced southwest flow
will also push thermal profiles a touch higher. Better chances for
rain as we head into Tuesday and especially Tuesday night as front
is pushed closer to our area. Still a very high degree of
uncertainty as to evolution of this boundary though and will have to
maintain broadbrush chance probability of precipitation for much of the upcoming week until
details become more clear. Some relief from the heat during the
midweek period but more substantial cool down does not arrive until
next weekend.


Aviation...(for the 06z tafs through 06z Saturday night)
issued at 156 am EDT Sat Sep 5 2015

Convection continues to form in a line from kbeh-kmie with ts
along the southern half of the forecast area. Showers moving off
Lake Michigan are not in favorable location to maintain any
vertical growth and expect these to slowly drift south and east
through 12z. Model soundings suggest that the boundary layer
should continue to decouple and with light winds and rainfall
expect to see patchy fog form before dawn. Fog will dissipate
rather quickly. Timing of afternoon showers / ts is still
difficult. Should see an increase in coverage late afternoon...
however for now have left out convection. Will re-evaluate for 12z


Iwx watches/warnings/advisories...


short term...Lewis
long term...agd

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