Area forecast discussion 
National Weather Service Indianapolis in 
722 PM EDT sun Jul 24 2016 


Update... 
the aviation section has been updated below. 


&& 


Synopsis... 
issued at 300 PM EDT sun Jul 24 2016 


One more relatively warm and humid day is expected 
Monday before slightly cooler and less humid air filters 
into our area Tuesday and Wednesday. The change in air mass will 
be accompanied by scattered thunderstorms though not all 
locations will receive this rain. The next weather system and 
return of slightly warmer and humid air will bring a better 
rain/storm coverage for the latter half of the week. 


Temperatures for this period will start above normal then dip to 
seasonal values for the balance of the week. 


&& 


Near term /tonight/... 


Issued at 300 PM EDT sun Jul 24 2016 


Synoptic models have been fairly consistent with the 
approaching frontal system and associated timing and coverage 
with precipitation. The rapid refresh has been a bit aggressive 
with precipitation development for this afternoon relative to 
observations perhaps the result of the extreme cape values being 
observed. Cap appears to be well in place still so will lean 
towards slower storm development of synoptic models. Lafayette to 
Kokomo area looks to have best shot at getting rain being closest 
to approaching front and instability still being relatively high. 
Remaining areas rain chances are not as great as stabilizing 
cooling occurs and frontal boundary and its lift only slow to 
approach northern counties before daybreak. 


Guidance minimum temperatures a tad on the warm side the last 
few days and will go just below those...but with winds to remain 
up a little...minimums should be several degree warmer than this 
morning. 


&& 


Short term /Monday through Wednesday/... 


Issued at 300 PM EDT sun Jul 24 2016 


Models are in fairly good agreement on movement and position 
of front over the next several days as high pressure takes over. 
The front will move from just north of our area at daybreak 
Monday to our southern counties by Sundown. With the strongest 
wind fields and best upper support well to the north and northeast 
convection should be relatively scattered. Where storms do 
develop expect heavy rainfall given our fairly high precipitable 
water values. 


Do not plan to add heat advisory for Monday with heat indices 
at highest just over 100 in our southern counties. Monday will 
still feel relatively warm and humid though. Will keep Max temps 
near guidance and previous forecast. Rain chances will likely 
follow diurnal trend with better chances at peak heating and 
along and ahead of southeast advancing cold front. Again given 
best dynamics being well northeast would expect no more than 
scattered convection and pops still in the chance category. 


For Tuesday and Wednesday the frontal boundary will slip south 
of the Ohio River. Current forecast of rain chances in 
southern counties may be a bit pessimistic as high pressure may 
more likely drive rain chances south of the Ohio River. Will keep 
low chances for now but another model run may suggest their 
removal. 


Temperatures Tuesday and Wednesday still look fairly good with 
mid and upper 80s appearing reasonable. Might be a tad high on 
holding southern County dewpoints in the lower 70s. High pressure 
scouring out the tropical air may reach south of our area by 
Wednesday and may need future adjusting. 


&& 


Long term /Wednesday night through Sunday/... 


Issued at 218 PM EDT sun Jul 24 2016 


Main challenge for the long term will be timing various upper waves 
moving through and ahead of a mean Mississippi Valley trough. 
Judging by the differences in the operational GFS and European model (ecmwf) and 
individual ensemble spaghetti plot members, the confidence in 
strength and timing of these waves is not good. For instance, the 
00z and 12z GFS runs have a strong wave moving through Thursday 
night, while the 00z European model (ecmwf) version is much weaker. Thus, will 
accept regional blend, which has chance pops Wednesday night through 
Sunday. 


Low level thermal progs support normal to slightly below normal 
blend highs in the lower to mid 80s. Meanwhile, look for overnight 
lows mostly be in the mid to upper 60s. 


&& 


Aviation /discussion for 250000z taf issuance/... 
issued at 722 PM EDT sun Jul 24 2016 


Restrictions possible within convection overnight and Monday 
otherwise predominantly VFR conditions expected. 


Convection has been slow to develop but has finally started to 
become better organized over northern Illinois since 22z. 
Convection developing in the vicinity of a prefrontal trough 
and aligned with an axis of strong instability with MLCAPES in 
excess of 5000 j/kg. Central Indiana remains under the influence 
of the ridge aloft and effectively capped with 700mb temps around 
12c. 


That presents the question of how far south the northern Illinois 
convection comes over the next 6-8 hours as storms move against 
the ridge flank. It has been another difficult day for model 
guidance...most of which has been grossly overdoing the convective 
development to the northwest. The parallel hrrr has the most 
reasonable solution at this point and loosely utilized it for 
timing and southward extent to convection into the overnight. The 
only terminal with medium to high confidence in convective impacts 
at this point is klaf with the potential that khuf and kind are 
also impacted after midnight. Introduce thunderstorms in the vicinity at klaf at 02z with 
more specific impacts in the 05-10z period. Will maintain a thunderstorms in the vicinity 
mention only at both khuf and kind until a better determination 
can be made regarding whether storms will directly impact either 
site late tonight as airmass quickly becomes less favorable for 
convection to persist further south. 


Storms are likely to diminish in coverage and intensity overnight 
as instability is lost...then refire by Monday afternoon south of 
I-70 along and ahead of the cold front in the moist unstable 
airmass. Will focus thunderstorms in the vicinity after 17-18z at kbmg and khuf and may 
eventually need to include kind as well. Drier air will advect in 
from the north by Monday evening. 


&& 


Ind watches/warnings/advisories... 
heat advisory until 8 PM EDT this evening for inz021-028>031- 
035>049-051>057-060>065-067>072. 


&& 


$$ 


Synopsis...tucek 
near term...tucek 
short term...puma 
long term....mk 
aviation...Ryan 






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