366 
FXUS63 KIWX 042314
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
714 PM EDT Sun Apr 4 2021

.SYNOPSIS...
Issued at 351 PM EDT Sun Apr 4 2021

Clouds will increase later tonight in advance of a weak system that 
will track across the Great Lakes on Monday. There is a chance of 
showers and thunderstorms late tonight into Monday mainly north of 
US Route 6. The warm weather will continue into midweek. Widespread 
rainfall is expected late Wednesday night into Thursday as a 
stronger system moves into the region. 

&&

.SHORT TERM...(This Evening through Monday)
Issued at 351 PM EDT Sun Apr 4 2021

Weak upper level short wave is bringing just some passing mid and 
high clouds to the Great Lakes region this afternoon. A slightly 
stronger embedded short wave from the Dakotas will top the ridge 
tonight. A modest low level theta-e push is expected tonight into 
the southern Great Lakes ahead of this feature. Veering of low 
level flow downstream of this feature across the Mid/Upper MS 
Valley will advect some steeper mid level lapse rates eastward 
overnight. Higher res near term guidance does indicate some 
convective response after 09Z across the southern Great Lakes due 
to the above factors. Currently expecting best chances to remain 
just north of local area, but cannot discount at least isolated 
elevated convection affecting far north/northwest portions of the 
area after 09Z at the leading edge of these steeper mid level
lapse rates. Southeast progression of the weak embedded short 
wave should allow weak sfc boundary to sag southward across the 
southern Great Lakes on Monday, with an eastward expansion of 
chance shower/storm PoPs into northeast Indiana, south central 
Michigan, and northwest Ohio Monday morning. Orientation of 
upstream ridge axis and expected placement of weak low level 
boundary would keep chances north of US Route 30 with best chances
north of US Route 6. Even warmer low level air advects into the 
area for Monday which supports highs in the 70 to 75 degree range
(possibly higher across the southwest). The only caveat would be 
if some outflow reinforces the weak sfc trough for some 
potentially slightly cooler conditions across far northeast 
Indiana/south central Lower Michigan/far northwest Ohio. Expecting
these shower chances to have largely diminished by Monday evening
as some capping becomes more likely.

&&

.LONG TERM...(Monday Night through Sunday)
Issued at 351 PM EDT Sun Apr 4 2021

Another weak ridge-topping upper level short wave is expected to 
progress across the Great Lakes on Tuesday. This will occur in 
background larger scale pattern of amplifying mid level ridging 
across the region. This lends to low confidence in any mentionable 
precip chances for Tuesday, and if any low end shower chances to 
evolve, would likely be confined to very far northern portions of 
the area in closer proximity to northward retreating low level 
boundary. With consistent model trend past few cycles for 
strengthening mid level ridging and consensus PoPs following suit 
in lower PoPs, will keep Tuesday PoPs below mentionable criteria.

Overall picture for the Wed-Thu remains unchanged today as potent 
upper low shifts across Rockies early Wednesday. Dprog/Dt trends in 
most of medium range guidance has indicated a preference to a more 
slowly evolving, stable wave pattern with even some slight 
retrogression in negative upper height anomaly across the western 
Atlantic early week. This continues to produce more confidence to 
slower evolution with the Rockies upper trough midweek. Only tweak 
of significant for this forecast was to continue to lower PoPs 
during the day Wednesday and focus on the late Wednesday night and 
especially into Thursday period for highest likely rain shower 
PoPs/isolated thunder.

Predictability in large scale pattern appears to decline post-
Thursday with continuation of active eastern Pacific pattern and 
high uncertainty regarding downstream phasing with potential 
lingering central CONUS upper low. Have deferred to consensus 
PoPs for Days 6/7 with another chance shower mention next weekend.
Temps to remain above normal through the period, with lower 
confidence in temps toward Day 7-8 due to uncertainty in these 
phasing issues.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday Evening)
Issued at 709 PM EDT Sun Apr 4 2021

A frontal boundary currently extends across southern Michigan. A
shortwave will develop along this front tonight and an area of 
showers and thunderstorms will form and move along the boundary, 
possible bringing some light rain as far south as northern 
Indiana. Have therefore included VCSH at SBN for Monday morning, 
but any thunderstorms that develop should stay north of the 
terminal. Winds will remain se to variable into tonight then turn 
sswly late tonight into Monday morning. VFR conditions are 
expected through the forecast period, although mid and high clouds
will increase.

&&

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

$$

SYNOPSIS...Marsili
SHORT TERM...Marsili
LONG TERM...Marsili
AVIATION...Cobb


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