Area forecast discussion 
National Weather Service Indianapolis in 
142 PM EDT Friday may 6 2016 


Update... 
the synopsis...near term and short term sections have been updated below. 


&& 


Synopsis... 
issued at 142 PM EDT Friday may 6 2016 


Tonight the quick reprieve from the recent wet weather will 
linger. However...showers and thunderstorms are expected to return 
to the forecast on Saturday afternoon through much of next week. 


High pressure south of Indiana will exit to the southeast on 
Saturday as a cold front approaches from the upper Midwest. 
Showers and storms are expected to develop along and ahead of the 
front on Saturday afternoon and evening as it pushes through the 
state. 


The front is expected to stall near the Ohio River on 
Sunday...lingering there until Monday when it returns to central 
Indiana as a warm front. This will result in more chances for rain 
showers as the weekend ends and the new work week begins. 


The warm front should stay with Indiana into Wednesday...then be 
replaced by a cold front. Another high pressure system will arrive 
Thursday. 




&& 


Near term /tonight/... 


Issued at 142 PM EDT Friday may 6 2016 


Surface analysis early this afternoon shows high pressure centered 
over Arkansas...extending a ridge of high pressure northeast into 
Indiana. Light northwest flow was in place across Indiana with 
comfortable dew points in the middle 40s. Low pressure was found 
across western Ontario...with a cold front sagging southwest 
across Minnesota and into the Dakotas. Aloft the water vapor 
imagery showed ridging in place over the Great Lakes which is part 
of a larger Omega block across the entire United States. 


Main forecast challenge tonight will be temperatures. 


Forecast soundings and time heights maintain a dry column tonight 
as the surface high pressure system settles across the deep south. 
With good subsidence will continue to trend toward a mostly clear 
sky. As for temperatures...strong warm air advection is expected 
overnight as the GFS and NAM suggest a 850mb thermal ridge in 
approaching ahead of the cold front. In fact...NAM suggests 850mb 
temperatures reaching 14-15c by 12z Saturday. Thus will not expect large 
temperature falls overnight...and will trend lows at or above 
mavmos. 


&& 


Short term /Saturday through Monday/... 


Issued at 142 PM EDT Friday may 6 2016 


Active weather is expected to return to central Indiana on 
Saturday. Models continue to suggest the cold front will push 
south across central Indiana during the afternoon. Favorable lower 
level convergence along with daytime heating looks to provide 
favorable conditions for shower and storm development. Forecast 
soundings on Saturday afternoon suggest MUCAPES in excess of 2000 
j/kg...along with steep...favorable lapse rates for convection. 
Convective temperatures near 80 appear very reachable. Thus will trend 
probability of precipitation at or above mavmos...mainly during the afternoon hours as 
convective temperatures are reached. Given the warm air advection and 
decent day of heating ahead of the front...will trend highs right 
near convective temperatures. 


Saturday night and Sunday the cold front looks to stall across southwest 
Indiana. The upper flow then also begins to break down...allowing 
northwest flow to occur over the front. Minimal support is seen at this 
time...however lower level convergence remains favorable across 
the southwest...along with favorable convective temperatures again on the 
warm side of the front. Meanwhile...by Sunday...weak high pressure 
should keep much of the north and east parts of central Indiana 
dry and cooler. Thus will focus probability of precipitation on Saturday night mainly 
across the south parts of the forecast area...and across the 
southwest on Sunday. Will stick close to guidance temperatures on lows 
and highs...expect near the front where we will trend lows warmer 
and highs cooler given the expected clouds and possible precipitation. 


Sunday night and Monday the flow aloft becomes more southwest and 
the GFS and NAM both severe several short waves pushing toward 
Indiana from the southwest. The lingering frontal boundary will 
act as a focus for developing precipitation. Forecast soundings on 
Sunday night show deep saturation amid an overrunning type 
pattern. 305k GFS isentropic surface suggesting excellent upglide 
across Indiana with a surge of specific humidities in excess of 5 
g/kg. Thus will once again trend probability of precipitation higher than guidance on 
Sunday night as this warm front with dynamics lifts north across 
central Indiana. Given the expected clouds...rain and warmer air 
moving in...will trend lows warmer than mavmos. 


Models then suggest the warm front lingering across the northern 
parts of central Indiana on Monday as yet another shortwave amid 
the southwest flow aloft pushes through central Indiana. 
Furthermore...forecast soundings on Monday suggest steep lapse 
rates again...with ample cape...no cap and easily attained 
convective temperatures. Thus will again need to include 
probability of precipitation...probably at or above mexmos. 


&& 


Long term /Monday through Thursday/... 
issued at 228 am EDT Friday may 6 2016 


Main focus for the long term will be on potential for unsettled 
weather through next work week. 


Models in good agreement that strong upper ridge will begin to break 
down late this weekend as an upper low moves into the Missouri 
Valley on Monday. Southwest flow around this low will allow a warm 
front to lift northeast across central Indiana. Then...as the upper 
low opens up over the Great Lakes...a cold front will sweep 
southeast across central Indiana Wednesday night. The combination of 
synoptic forcing...deep moisture and instability warrants 
thunderstorm chances throughout the long term and especially Monday 
night through Tuesday night...when likely probability of precipitation from the regional 
blend look good. 


Seasonable to slight above blend temperatures with afternoon highs 
in the 70s look good. 


&& 


Aviation /discussion for the 05/18z tafs/... 
issued at 100 PM EDT Friday may 6 2016 


VFR through the period. 


High pressure is in place across the region providing clear skies 
and winds less than 10kt. 


Quiet conditions will continue through tonight. Cannot entirely rule 
out brief MVFR fog near daybreak at some sites but this is far too 
uncertain for inclusion and would be of minimal impact. 


Winds late in the period may become gusty at all sites...into the 
low to middle 20kt range. 


In the 30 hour period at ind...will include a thunderstorms in the vicinity mention after 20z 
Saturday. This remains outside the current taf period at the 
outlying sites. 


&& 


Ind watches/warnings/advisories... 
none. 
&& 


$$ 


Synopsis...puma 
near term...puma 
short term...puma 
long term...mk 
aviation...nield 



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