Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Indianapolis in
1023 am EDT Sat Aug 30 2014
the near term section has been updated below.
issued at 308 am EDT Sat Aug 30 2014
Upper disturbances will keep chances for rain in the forecast for
the Holiday weekend...and a frontal system will bring additional
chances for rain for much of next week. Temperatures will remain
near to above average for most of the next week.
Near term /rest of today/...
issued at 1023 am EDT Sat Aug 30 2014
Wet morning in progress over much of the southern half of the
forecast area with more isolated activity further north. Temperatures
were being held in the lower and middle 70s as of 14z with the rain
and clouds across the region.
Overall forecast in very good shape with a few adjustments needed
based on current analysis and short range model guidance. Plume
of deep tropical moisture coming out of the Gulf north through the
Mississippi River valley and into the region helping to generate
more widespread precipitation in southern counties this morning.
Mesoanalysis indicating precipitation water values at 2 inches or
greater within this plume...and this should continue to overspread
southern Indiana into the afternoon hours. In addition...expect
coverage to increase across western counties this afternoon as low
pressure and an upper wave over Wisconsin move east into the
central Great Lakes by this evening. Forcing aloft will increase
across the region as a result...with an upper level jetlet moving
into the lower Great Lakes by late afternoon.
As mentioned...main area for showers and embedded thunder to focus
into the early afternoon should remain in vicinity of the
highest precipitation water values over southern counties. After that as
convective temperatures are reached and forcing aloft increases...
anticipate an uptick in storms elsewhere into the evening hours.
Torrential rainfall...lightning and gusty winds with storms will
impact outdoor activities through the rest of the day. Will
continue with likely probability of precipitation over western half of the forecast are
and high chances further east. Even with the convective coverage
increasing...not anticipating a washout as there will be periods
with dry weather throughout the afternoon and evening.
Lowered high temperatures for the afternoon with abundant cloud cover
across central Indiana. Will be pockets of filtered sunshine here
and there which should still enable maximum temperatures into the 80-84 range
by late day. Zone and grid updates out.
Short term.../tonight through Monday night/
issued at 308 am EDT Sat Aug 30 2014
Focus remains on chances of rain through the period. Models are
similar with the big picture but differ in the details. See no clear
favorite in the details so stuck with a blend.
The forecast area will be in the right rear quadrant of an upper jet
tonight. With decent forcing and moisture will go likely probability of precipitation.
Lowered probability of precipitation most locations overnight as forcing lessens some. Could
be some locally heavy rain with high precipitable water
Forcing will continue to diminish during the day on Sunday as upper
system moves east. Went likely probability of precipitation in the morning southeast and
chance probability of precipitation in the afternoon. Elsewhere went chance category or
Little forcing will be around the area Sunday night. However since
slight chance probability of precipitation were already in the forecast...left them alone to
avoid flip-flopping as isolated convection cannot be completely
Chances for rain will increase once again Monday into Monday night
as another upper system moves into the area. Moisture will continue
to be plentiful. 30-40kt winds at 850mb and an upper jet will aid in
forcing. Thus went likely probability of precipitation across the northern half of the area
by Monday night with high chance category probability of precipitation south.
For temperatures...mav looks too warm on Sunday with lingering
clouds and rain...but met looks too cool. Went in between. On Monday
mav still looks a bit warm most areas but may not be too far off the
mark if rain arrives later in the day. Cut mav as needed. For low
temperatures through the period stuck with a blend.
Long term /Tuesday through Friday/...
issued at 248 am EDT Sat Aug 30 2014
Thunderstorm chances along with temperatures will be focus for the
long term. Ensemble blend continues to look better than the
deterministic models which are tending to change a bit run to run
regarding the specifics of the upcoming synoptic pattern. Trends
continue that an upper trough will move across the lower Great Lakes
on Tuesday in the fast flow aloft as a cold front drops southeast
across central Indiana. This should be enough to produce scattered
to widespread thunderstorms on Tuesday and lingering into Tuesday
night. After that...upper ridge will build across the area from the
south. As a result regional blend suggests only small probability of precipitation through
Thursday night. Meanwhile...after a brief break in temperatures in
the wake of the cold front on Wednesday...late week temperatures
will be above normal with afternoon highs in the lower 90s possible
across south central Indiana on Friday per the regional blend.
Finally...another front will be in the area next weekend which
should bring better chances of thunderstorms in once again.
Aviation /discussion for the 30/1500z taf issuance/...
issued at 1010 am EDT Sat Aug 30 2014
extended tempo time frame for showers at kind through Sat 17z.
VFR and tempo MVFR conditions in showers are expected the first
few hours of the forecast with thunderstorms increasing in
coverage during the afternoon. Will go with thunderstorms in the vicinity and tempo showers
through 15z and then thunderstorms in the vicinity during the afternoon and finally MVFR
thunderstorms in the prevailing group as it gets closer to 00z.
The activity should more scattered overnight...so will go with
thunderstorms in the vicinity and MVFR conditions after 05z.
Winds will be south and southwest and increase to 10 knots or so
with gusts to 20 knots this afternoon. Winds will die down after 00z
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