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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Monday
• 
• High: 73 °
• Low: 55 °
• Chance of T-Storms

• Tuesday
• 
• High: 77 °
• Low: 48 °
• Clear

• Wednesday
• 
• High: 86 °
• Low: 61 °
• Clear

• Thursday
• 
• High: 90 °
• Low: 72 °
• Partly Cloudy

• Friday
• 
• High: 93 °
• Low: 64 °
• Partly Cloudy

Area forecast discussion 
National Weather Service Indianapolis in 
1259 PM EDT Monday may 21 2012 


Update... 
aviation section has been updated below. 


&& 


Synopsis... 


Issued at 338 am EDT Monday may 21 2012 


Scattered showers and thunderstorms will gradually shift east today 
with a weak cold front...with dry weather returning tonight as high 
pressure reestablishes over the region. After a brief cooldown for 
today and Tuesday...arrival of ridging aloft and southerly flow will 
bring a warming trend beginning on Wednesday. The upper ridge will 
become the dominant weather feature for the Ohio Valley for late 
week and the upcoming Holiday weekend...with dry weather and the 
hottest temperatures of the year so far. 


&& 


Near term /rest of today/... 


Issued at 922 am EDT Monday may 21 2012 


Analysis as of 915am this morning depicts a surface cold front 
moving across the western counties of the County Warning Area early this morning... 


The passage of the front will usher in much drier air and a shift 
to northwest winds as it progresses east through the forecast area 
during the course of the day. Convective coverage continues to 
diminish early this morning as instability wanes and forcing aloft 
is limited. Current rap indicating that convective coverage will 
decrease over the next few hours...with renewed development mainly 
along and ahead of the instability gradient and frontal boundary 
by middle/late morning over the eastern half of the forecast area. 
Have focused highest probability of precipitation south and east of the indy metropolitan where 
combination of the instability and deepest moisture axis should 
promote largely disorganized and scattered convection into the 
afternoon. 


Will maintain low chance probability of precipitation over western counties this morning to 
account for any isolated development along the front as it moves 
into the area. However...expect an overall drying trend for the 
afternoon as model guidance in agreement on much drier air advecting 
into the region from the west with a capping inversion becoming well 
established by late day. Axis of deeper moisture will shift east 
into Ohio by early evening with any lingering precipitation departing the 
forecast area. 


Temperatures...cooler day setting up as cold advection commences with the 
frontal passage. Consall and mavmos guidance matched up well with 
low level thermals with most locations remaining in the 70s this 
afternoon. 


&& 


Short term /tonight through Wednesday night/... 


Issued at 338 am EDT Monday may 21 2012 


Forecast challenges focus on temperatures through the period as a warming 
trend commences by Wednesday with the return of ridging aloft. 


Upper trough will sharpen as it passes the forecast area tonight... 
eventually developing an upper low that will dive into the southeast 
states by Tuesday night. This will cause deeper moisture to hold 
over the eastern Ohio Valley and the southern Appalachians into 
Wednesday as the upper low slowly pinwheels east into the Carolinas. 
The only impacts to central Indiana will be to accentuate cloud 
cover into Tuesday over eastern counties where presence of a low 
level thermal trough likely to enable a healthy cumulus field on the back 
side of the moisture plume. Further west across the forecast area... 
increasingly deeper subsidence will funnel into the region with 
mostly sunny skies expected. 


Ridging aloft will steadily expand into the region Tuesday night and 
Wednesday as the upper low moves east across the southern 
Appalachians. Progressively deeper subsidence will expand across the 
Ohio Valley on Wednesday as return southerly flow signals the 
arrival of warm advection. Result will be mainly clear skies 
Wednesday and Wednesday night and the beginning of a warmup that 
will continue through the rest of the week. 


Temperatures...MOS guidance and consall matched up well on Tuesday with 
temperatures mainly in the middle 70s. Leaned closer to warmer mavmos 
Wednesday as highs return to the 80s. Potential for temperatures to slip 
into the upper 40s both tonight and Tuesday night in rural locales 
with 50s elsewhere. 


&& 


Long term /Thursday through Sunday/... 


Issued at 338 am EDT Monday may 21 2012 


Models still differ in the extended on how far south a cold front 
gets into the area Friday and Saturday. GFS is the outlier again in 
bringing in the cold front farther south. Even GFS ensemble mean 
keeps front to the north...and experimental GFS ensemble confidence 
plots Show Low to very low confidence in GFS temperatures by next 
weekend. Thus will throw out GFS and go closer to European model (ecmwf) again with 
this package. 


The above means raising allblend temperatures next weekend and 
removing any chances for rain that it gives. Also adjusted allblend 
dewpoints and sky cover as necessary. 


Upper high will move into the area late in the week and persist into 
the weekend. This will result in hot conditions for the Holiday 
weekend with no rain expected. Dewpoints and thus resultant heat 
index values are more uncertain due to lack of widespread 
significant rainfall recently. Conditions will still be very warm 
regardless so will continue to mention heat in severe weather potential statement. 


&& 


Aviation /discussion for the 211800z tafs issuance/... 


Issued at 1259 PM EDT Monday may 21 2012 


Cold front currently over eastern central and southern Indiana will 
will continue moving east. Areas of MVFR ceilings have developed 
behind cold front and was currently limiting ceilings all except 
kind. 


With some daytime heating...expect ceilings to rise to VFR category 
in a few hours. But ceilings may remain barely above 3 thousand feet 
as there is an extensive area of cumulus upstream across eastern 
Illinois. 


Drier air will spread into western sections by evening and over most 
of the remaining area later tonight. Expect clouds to scatter out 
most areas by evening and even become clear at khuf and klaf by 
midnight. Models keep some low level moisture across the southeast 
half of Indiana Indiana into Tuesday...so any clearing at kind and 
kbmg may not occur until near or after the end of the forecast 
period. 


North to northwest winds will increase to 10 to 15 knots this 
afternoon and drop to 8 knots or less tonight. 


&& 


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


$$ 


Synopsis...Ryan 
near term...Ryan/smf 
short term...Ryan 
long term....50 
aviation...jh