Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 211449

Area Forecast Discussion
National Weather Service Northern Indiana
1049 AM EDT Sun Apr 21 2019

Issued at 1048 AM EDT Sun Apr 21 2019

Partly to mostly sunny skies are expected today allowing high
temperatures to reach the low 70s across far northwest Indiana to
the low to mid 60s across northwest Ohio. Clouds will be on the
increase again for Monday and Monday night with just a low chance
of showers again Monday night and Tuesday as the next frontal
boundary approaches. Mild conditions can be expected in advance of
this front, with highs in the 70s on Monday.


Issued at 1048 AM EDT Sun Apr 21 2019

Cleaned up grids some to bring on higher cloud coverage to handle
fast moving area of mid clouds dropping south. Deck is slowly
thinning/mixing out so should only impacts warming temps briefly.
Other change was to lower dewpoints in the west where values in
the 20s were noted (hi res models not capturing) yielding RH
values in the mid 20% range. Will need to watch trends into this
afternoon once clouds leave with large dewpoint depressions noted
on 12Z DTX/APX soundings around 850 mb. Luckily the wet weather
and winds under 10 mph will limit any fire weather concerns.


.SHORT TERM...(Today and Tonight)
Issued at 350 AM EDT Sun Apr 21 2019

Clearing skies, calm winds, and lingering trapped low level
moisture have allowed for areas of fog formation overnight. Fog
was quite shallow initially, but deepening nocturnal inversion and
west to east clearing trend for locations with better near sfc
trapped moisture may allow for at least a short-lived period of
dense fog potential roughly in the vicinity of the I-69 corridor
and locations just to the west of I-69 through 12Z or 13Z.
Observations have been depicting varying visibilities likely
indicative of shallow nature of fog, but still may need to
monitor potential for narrow swath of advisory conditions this
morning. Areas west of US Route 31 likely not to see expansive fog
as dew points and hydrolapse profiles are not nearly as

Otherwise for today, mostly sunny skies expected although patchy
mid level cloud deck may bring a period of partly-mostly cloudy
conditions across far northwest-north for a time this morning as
mid level ridge/weak mid level warm advection build in behind the
departing upper level low. Low level ridge axis sagging to the
southeast this morning will allow for weak return westerly
flow/low level warm advection today. Have not made much change to
previous forecast with highs from low-mid 70s extreme west to the
low-mid 60s east.

Weak lee cyclogenesis across the Rockies today combined with
eastward departure of low level anticyclone will cause modest
increase in low level flow tonight, and continued low level warm
advection will keep low temps on the more mild side tonight in
the 45 to 50 degree range.


.LONG TERM...(Monday through Saturday)
Issued at 350 AM EDT Sun Apr 21 2019

Longwave pattern will be somewhat slow to evolve for early
portions of the week as upper level ridge axis reaches the
western Great Lakes by Monday afternoon. This will allow a
lead vort max emanating from broader southwest CONUS negative
height anomaly to work across Mid MS Valley Monday afternoon,
and across the western Great Lakes Monday night. Confidence
in extent of rain showers with this feature Monday night into
Tuesday is beginning to diminish somewhat due to strongest
forcing likely just to graze northern portions of the forecast area
and due to an elevated mixed layer advecting into the region
possibly limiting elevated instability. Best chance of showers
still appears to be Monday night with initial theta-e advective
push, and then again Tuesday afternoon across the east/southeast
as associated cool frontal boundary passes through during more
diurnally favored time of day to realize weak instability. Above
normal temperatures still on track for Monday and Tuesday ahead of
this feature, with highs well into the 70s Monday. Warmest temps
will be confined to southeast locations on Tuesday due to frontal

Forecast confidence diminishes for mid-late week as local area
becomes positioned between more progressive northern stream short
wave track, and cut off PV anomaly across the southern Plains.
Medium range models are still providing some indication of fast
moving northern stream north wave working across Great Lakes
region for Thursday with a low chance of showers, but it still
appears as though better moisture will remain limited to well
south of the area due to earlier week frontal passage and little
opportunity for good moisture return. Weak thermal troughing
behind this feature should keep highs in the 60s for Wed-Fri, with
better chance at moderation again toward the end of the period as
zonal flow pattern becomes established.


.AVIATION...(For the 12Z TAFS through 12Z Monday Morning)
Issued at 654 AM EDT Sun Apr 21 2019

Ground fog had developed over much of northern Indiana with the
fog very close to the FWA terminal. Have allowed the 1/2SM FG in
the TAF for now given the potential for a very rapid drop in the
visibility before 1230Z. At SBN, the boundary went back across the
terminal with the dew point rising 11F in one hour. Some potential
for light/MVFR fog there, but the shallow radiation inversion will
mix out rapidly with VFR conditions the rest of the period.




SHORT TERM...Marsili
LONG TERM...Marsili

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