Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 281805
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
205 PM EDT SAT MAY 28 2016

.UPDATE...
The LONG TERM Section has been updated below.

&&

.SYNOPSIS...
Issued at 330 AM EDT Sat May 28 2016

A warm and humid air mass will persist across the region through the
weekend with chances for showers and thunderstorms as a series of
upper waves pass through the Ohio Valley. Rain chances will end once
a weakening cold front passes through on Sunday...with less humid
weather for Monday and Tuesday. Scattered thunderstorms will return
to central Indiana by mid week as a storm system tracks through the
region. Cooler and drier conditions are expected by next weekend.

&&

.NEAR TERM /rest of Today/...
Issued at 940 AM EDT Sat May 28 2016

.UPDATE...Only minor tweaks made to grids mainly to raise POPS to 50
percent across the eastern half of our region where the deepest
moisture will be. High res model shows an increase in showers and
storms this afternoon as it moves north northeast across our region.
Otherwise...the remainder of the near term is on track.

Portion of previous near term discussion follows...
The Ohio Valley will remain entrenched within a moist southwest flow
aloft as a stubborn upper low over the central plains this morning
lifts northeast through the course of the day. Weak and poorly
defined perturbations aloft continue to eject out from the upper low
and lift into the area and will once again serve to offer forcing
for convective development today...especially this afternoon during
peak heating.

Deeper moisture advecting into the region courtesy of stronger low
level flow helping to generate the isolated activity early this
morning. A few lightning strikes cannot be ruled out with
mesoanalysis indicating subtle instability present...but overall
primarily anticipating showers through mid morning. Slightly
stronger wave aloft poised to lift into the Ohio Valley this
afternoon and with the airmass becoming more unstable with
heating...expect more of a convective component over the forecast
area with scattered thunderstorms developing. Primary focus for
greatest convective coverage likely to align over the eastern half
of the forecast area where axis of deeper moisture will reside...but
chance pops are warranted over all of central Indiana this
afternoon. With boundary layer shear lacking...expect convection to
remain largely disorganized later today with brief heavy downpours
as the main impact.

Temps...Expect less sunshine than Friday for most as model soundings
and RH progs showing a lot of potential for clouds through the
course of the day.  This will serve to keep max temps cooler than
Friday...with low level thermals supporting highs generally in the
lower 80s.

&&

.SHORT TERM /Tonight through Monday Night/...
Issued at 330 AM EDT Sat May 28 2016

Forecast challenges focus on convective chances through Sunday
followed by drier weather for Memorial Day as weak high pressure
arrives.

The aforementioned upper low will become slowly absorbed into the
mean flow aloft on Sunday as it tracks east across the Great Lakes.
The remnant wave aloft will enhance lift across the region and
combine with a weakening cold front to provide another round for
scattered convection during the afternoon and evening Sunday. Strong
surface heating will produce a modestly unstable airmass with
steepening lapse rates as cooler and drier air in the mid levels
arrives Despite weak low level flow and boundary layer shear...the
frontal boundary and wave aloft should support potential for more
organized and stronger convection in a multicellular mode.
Thermodynamic profiles suggestive of gusty wind and hail potential
with stronger cells. Timing differences still exist between various
models...but chance pops remain warranted and focused during the
second half of the afternoon into the evening as the front tracks
across the area.

Drier air will overspread the region Sunday night as weak surface
ridging reestablishes and the weakening wave aloft departs off to
the east. A dry and slightly less humid airmass will settle into the
Ohio Valley for Memorial Day and Monday night with the surface ridge
in control over the area and slowly rising heights aloft.

Temps...Warm weather will continue across the region through the
short term. Low level thermals remain supportive of highs rising
into the mid 80s both Sunday and Monday for most areas.

&&

.LONG TERM /Tuesday Night through Saturday/...

Issued at 159 PM EDT Sat May 28 2016

ECMWF continue to keeps the warm and humid air mass in place
across central Indiana through Thursday. Thus as superblend
suggests...kept low chance pops in place during that time to
account for diurnal showers and storms.

Best chances for rain look to be on Thursday afternoon and evening
as the ECMWF shows a cold front crossing Indiana from the
northwest. With ample moisture in place ahead of the
front...precipitation seems like a good bet here.

Superblend continued to keep low chance pops in the forecast on
Friday and Saturday. The ECMWF shows the cold front southeast of
Indiana at that time...along with subsidence in place along with a
cooler and dryer air mass in place amid NW flow. Therefore we
twiddled the pop grids down 5-10% to achieve a dry forecast then.

&&

.AVIATION /discussion for the 281800z tafs/...

Issued at 105 PM EDT Sat May 28 2016

VFR conditions expected much of this taf period. Brief MVFR
conditions will be possible late this afternoon and early evening
within any TSRA that may strike a TAF site.

Rapid Refresh continues to suggest convective development...mainly
during the peak heating hours of 20Z-01z. Thus have used VCTS for
now along with a TEMPO group for thunder during this most
favorable period.

Any spots that get rain...particularly the more rural taf sites
will be favorable for MVFR diurnal fog in the morning given the
expected lingering lower level moisture and small dew point
depressions.

CU rule is negative on sunday morning and low level moisture
lingers. Used VFR CIGS to cover this situation.


&&

.IND Watches/Warnings/Advisories...
NONE.
&&

$$

SYNOPSIS...RYAN
NEAR TERM...RYAN/JH
SHORT TERM...RYAN
LONG TERM....PUMA
AVIATION...JP



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