Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Indianapolis in
1017 PM EDT Friday Aug 22 2014
the near term section has been updated below.
issued at 326 PM EDT Friday Aug 22 2014
Scattered thunderstorms will remain possible into Sunday as a
frontal boundary remains across the Ohio Valley. An upper level
ridge will expand into the region for late weekend and early next
week...bringing a period of very warm and dry weather. Thunderstorm
chances return for midweek with the arrival of a cold front...with
cooler weather to follow.
Near term /rest of tonight/...
Issued at 1005 PM EDT Friday Aug 22 2014
trended probability of precipitation downward for the rest of tonight...but latest
forecasted probability of precipitation may even still be too high. Confidence was not
high enough to go slight chance or lower though despite little
development according to rapid refresh. Current temperatures across the
area are generally in the middle to upper 70s. Forecasted lows of
upper 60s/low 70s still look reasonable...so no changes to those.
Updated grids have been sent.
beyond the early evening hours...potential does exist for another
period of convective expansion later tonight as a few pieces of
energy aloft ripple over the top of the ridge and into central
Indiana and add their weight to the moist unstable airmass over the
region. One possible mitigating issue is the lack of a more
pronounced nocturnal low level jet overnight which may serve to keep
storms more scattered through the night.
Temperatures...another steamy night with lows remaining in the lower and
middle 70s. A consmos blend looked reasonable and was utilized.
Short term /Saturday through Monday/...
issued at 326 PM EDT Friday Aug 22 2014
Forecast challenges focus on precipitation chances Saturday into Sunday and
potential heat as the ridge builds early next week. Uncertainty in
the pop forecast remains high for Saturday/Saturday night and is
somewhat dependent on what takes place late tonight/early Saturday.
Depending on precipitation coverage late tonight...very possible that
storms are ongoing at 12z Saturday with at the very least remnant
cloud debris over the forecast area. Middle level heights attempt to
rise with the ridge expanding during the day but in general...model
consensus keeps central Indiana on the eastern periphery of the
ridge axis. With the boundary lingering across the region and the
airmass prognosticated to become moderately unstable by afternoon...
scattered probability of precipitation are warranted for much of the forecast area into the
evening. Heavy rainfall and locally gusty winds will certainly be
possible with convection Saturday afternoon and evening.
Convective potential much more conditional on Sunday as the ridge
axis expands east into the Ohio Valley with subtle capping
developing as 700mb temperatures warm to 10-11c. Leftover boundary remains
across the forecast area however and warrants low chance probability of precipitation as
isolated convection cannot be entirely ruled out. The ridge
strengthens its hold on the area for Monday as core of the warmest
air aloft aligns just southwest of the forecast area. In the
absence of any appreciable forcing aloft expect dry conditions.
Temperatures...mavmos guidance much more believable for weekend highs.
Considering the potential for clouds and convection Saturday and
possibly even Sunday...still expect most locations remain below 90
degrees with the only exception over the lower Wabash valley and far
southern forecast area where lower 90s are expected. Best chance for
kind to make a run at their first 90 of the year comes Monday with
the core of the ridge centered over the region. Considering the
moist low levels however...would really like to see temperatures a touch
warmer in the boundary layer to support 90+. Have chosen to keep
them just shy of 90 for the Monday high. We shall see.
Will continue to highlight heat indices in the upper 90s and lower
100s through Monday...with biggest impacts in the lower Wabash
Long term /Monday night through Friday/...
issued at 220 PM EDT Friday Aug 22 2014
Models are close enough that the allblend initialization was
accepted for most items.
An upper trough will move into the area during the long
term...bringing a return of cooler air and frequent chances for
Tuesday and Wednesday still look to be warm and humid with above
normal temperatures...but a cold front will move in and bring near
to below average temperatures for the end of the week.
Chances for rain will return Tuesday and continue through Thursday
with the cold front in the area. For now kept Friday dry as front
may be far enough south to keep the rain away.
Aviation /discussion for the 230000z taf issuance/...
issued at 624 PM EDT Friday Aug 22 2014
A few storms have popped up along an outflow boundary that lined up
southeast to northwest near bmg and huf. Upper wave appeared to be
helping things along. So...will make a last minute decision at huf
and bmg whether to include thunderstorms in the vicinity or a tempo thunderstorm group. The
19z rapid refresh has activity in this area much of the evening.
More storms could move in from northwest to southeast overnight
ahead of an Iowa wave...however confidence is not high enough to
include. Finally...went with heating of the day storms and prob30
tomorrow late afternoon as yet another wave drops down overtop the
Mississippi Valley ridge.
With dew points as high as they are could see some MVFR or worse fog
overnight if convective debris does not interfere. Winds will be
very light or calm tonight and light tomorrow.
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