Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Indianapolis in
704 PM EDT Thursday Sep 3 2015
the aviation section has been updated below.
issued at 141 PM EDT Thursday Sep 3 2015
A strong ridge of high pressure is expected to remain across
central Indiana over the next several days. This will result in
little change in the weather. Widely scattered afternoon and
evening showers and thunderstorms will remain possible each day
through the weekend as a very warm and humid air mass is in
Look for temperatures to remain above seasonal normals through
the weekend and into early next week.
Near term /tonight/...
Issued at 141 PM EDT Thursday Sep 3 2015
Surface analysis early this afternoon shows high pressure in place
over Kentucky and the Tennessee River valley. Warm and humid SW
flow was in place across central Indiana as dew point temperatures
remained in the upper 60s to lower 70s. Aloft...a strong ridge
was in place over the Central Plains. A weak short wave was found
on the Lee side of the ridge over lower Michigan.
GFS and NAM continue to keep the strong ridge in place
tonight...however the weak short wave appears to propagate to the
southeast...mainly across Ohio. During this progression...some
energy from this system appears to be sheared into eastern
Indiana. Time height sections through tonight just show lower
level moisture with no forcing available. Meanwhile forecast
soundings show good cape....in excess of 2000 j/kg available late
this afternoon and evening. Thus given the persistence of daily
storms along with daytime heating and even some energy from the
approaching short wave arriving in the northeast parts of the
forecast area...will carries probability of precipitation again this afternoon and evening
for scattered tsra/shra.
As for temperatures...with little change in the overall pattern...will
trend toward persistence for overnight lows...which may also
result in some patchy fog.
Short term /Friday through Sunday/...
Issued at 141 PM EDT Thursday Sep 3 2015
GFS and NAM continue to suggest little change in the overall
weather pattern through Sunday. Strong high pressure looks to
remain in place across the Ohio Valley and much of the eastern
United States. Meanwhile aloft a strong ridge appears to remain in
place across the eastern United States...steering any short waves
well north of Indiana into the northern greater lakes and
Ontario. Time height sections look unchanged through the
period...with plenty of lower level moisture indicative of the
high dew points...and little to no lift. Forecast soundings each
day also show attainable convective temperatures each day with decent
cape in excess of 1500 j/kg also. Thus diurnal thunderstorms and rain cannot be
ruled out each afternoon. Will continue with at least a low pop
each afternoon and evening. Furthermore the light winds and high
dew points each night will lead to favorable conditions for fog
formation. Will include patch fog each night.
As for temperatures...with little overall change in the air mass...will
trend toward expected persistence for highs and lows.
Long term /Sunday night through Thursday/...
issued at 208 PM EDT Thursday Sep 3 2015
Models are close enough that the superblend initialization was
accepted for most items.
Upper ridging will break down some and allow upper flow to become
west or northwest by the end of the long term period. This will mean
an end to the hot temperatures across the area.
As the upper ridge diminishes...a cold front will be able to slowly
move through the area. Will keep superblend probability of precipitation pretty much
intact...which means chances for rain in some part of the forecast
area Monday into Thursday.
The start of the long term will see hot temperatures...but highs by
Thursday will be in the 70s.
Aviation /discussion for the 040000z taf issuance/...
issued at 704 PM EDT Thursday Sep 3 2015
The last remaining diurnal cumulus will continue to burn off this
evening...leaving only high clouds overnight. Visibilities will
become restricted at the outlying sites by 05z...dropping to periods
of LIFR at khuf and kbmg during times of the densest fog. MVFR is
expected at kind and klaf. VFR cloud decks and visibilities will
return to all sites by 13z and persist through the end of period in
an unchanging air mass.
While dry weather is expected...there is a slight chance for
vicinity showers and thunderstorms at klaf and kind towards the end
of the period from a storm system over Michigan that may expand
southward Friday afternoon. Winds will be light out of the