303 
FXUS63 KIWX 191036
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
636 AM EDT Tue Oct 19 2021

.SYNOPSIS...
Issued at 635 AM EDT Tue Oct 19 2021

Sunny to partly cloudy skies and southwest winds will allow for 
another mild day with afternoon high temperatures into the lower 
70s. A system across the Central Plains today will shift eastward 
for Wednesday and will drag a cold front into the region Wednesday
night. Scattered showers and a few thunderstorms are expected 
Wednesday night. A trend back to cooler conditions can be expected
for the end of the work week.

&&

.SHORT TERM...(Today and Tonight)
Issued at 325 AM EDT Tue Oct 19 2021

Mild conditions are expected today with a continuation of sunny to 
partly cloudy skies.

Upper level ridge axis will be shifting across the Great Lakes and 
Ohio Valley today with continued weak low level warm advection. Some 
high level clouds are possible this afternoon, but overall expecting 
high temperatures similar to that of yesterday, and perhaps a few 
degrees warmer in most spots. The combination of surface low 
pressure development in lee of Rockies associated with Wednesday 
night system and expansive southeast CONUS low level anticyclone 
will provide southwest winds to the area today, with the strongest 
gradient expected across northwest locations. Some gusts into the 15 
to 20 mph range are possible this afternoon as a result.

Continued low level warm advection and maintenance of weak gradient 
overnight tonight should continue the trend of slightly milder 
overnight lows tonight, generally in the upper 40s to around 50 
(although favored cool spots may dip into the mid 40s).

&&

.LONG TERM...(Wednesday through Monday)
Issued at 325 AM EDT Tue Oct 19 2021

Not a great deal has changed with the forecast in terms of 
Wednesday's precipitation potential. Closed upper level system 
across the Rockies today will shift into the Corn Belt on Wednesday. 
Northeast progression of this upper low will be limited by blocking 
broader negative upper height anomaly sinking south across northern 
Ontario. Cooling upper level temperatures with approach of this 
upper low will allow for steepening mid level lapse rates as we head 
into Wednesday afternoon and evening. Low level moisture transport 
does become more favorable locally, albeit for a short time, 
Wednesday afternoon/evening before low level flow becomes more 
veered later Wednesday night. The combination of approaching upper 
trough, narrow 1+ inch PWAT axis, and steepening mid level lapse 
will support increasing shower chances later Wednesday 
afternoon/Wednesday evening. Some increasing signs that this event 
may be a little more convectively driven with elevated moisture 
return potentially briefly interacting with steeper mid level lapse 
rates. With this mind, will continue to temper PoPs a bit from model 
guidance consensus and maintain high chance/likely PoPs.

Mid level dry slot builds in late Wednesday night/Thursday morning, 
but will maintain some low chance shower PoPs into Thursday as dry 
slot gets suppressed by aforementioned blocking Ontario upper 
trough, and some mid level moisture sinks back south across southern 
Great Lakes. Secondary sfc trough passage still looks on track for 
Thursday to bring reinforcing low level cold advection into Friday.

The weekend still appears to be setting up as one with below normal 
temperatures, with mainly dry conditions at least through the first 
half of the weekend. One eastern Pacific wave should tend to get 
sheared as it works down the upstream upper ridge axis into the 
Ohio Valley later Friday night. Some weak fgen signal is possible 
with this wave that could bring low coverage shower potential for 
a time Friday night, but confidence is quite low. Overall 
predictablilty with additional more amplified eastern Pacific 
waves still remains low for 2nd half of weekend into early next 
week, although large scale pattern may trend to favor periodic 
chances of showers toward end of this period as advective forcing 
may increase downstream of any deepening eastern Pacific wave 
across central CONUS.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday Morning)
Issued at 635 AM EDT Tue Oct 19 2021

VFR conditions expected through the TAF period with mostly clear
skies and light southwesterly winds. 

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

SYNOPSIS...Marsili
SHORT TERM...Marsili
LONG TERM...Marsili
AVIATION...MCD


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