Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 231029

Area Forecast Discussion
National Weather Service Northern Indiana
629 AM EDT Sun Oct 23 2016

Issued at 343 AM EDT Sun Oct 23 2016

Mostly sunny skies can be expected today although clouds
will increase later this afternoon across far northern Indiana
and southern lower Michigan as a fast moving disturbance
approaches from the northwest. Gusty southwest winds ahead of
this disturbance will allow for mild conditions this afternoon,
cooling back to more seasonable levels tonight and Monday as a
cold front moves across the area. Dry conditions are expected to
persist across the region from today through Tuesday. Rain
chances will then increase Tuesday night through the middle of
the week. High temperatures today will range from the upper 60s
to lower 70s across northwest and north central Indiana to the
mid 60s across south central lower Michigan. Lows tonight will
drop into the lower to mid 40s.


.SHORT TERM...(Today and Tonight)
Issued at 343 AM EDT Sun Oct 23 2016

Main story for the short term period will be mild conditions
today followed by next frontal passage tonight.

A progressive but fairly compact and well-defined upper level short
wave skirting across the North Dakota/southern Manitoba border will
be the primary feature of interest for the short term. This short
wave is expected to race eastward this morning eventually reaching
the western Great lakes by mid afternoon and to southern Lake Huron
by early evening. Low level flow/warm advection will ramp up this
morning in advance of this feature setting the stage for milder
conditions. Strong warm advection in the 850-700 hPa layer will
limit mixing heights but magnitude of air mass and mixing up to 900
hPa would still support high temps from the lower 70s southwest to
mid 60s far northeast. Southwest winds will become gusty into the 20-
30 mph range this afternoon particularly southern two thirds of the
forecast area based on sfc reflection track and better enhancement
to winds from sfc pressure falls tracking across the southern Great

It still appears as though best channeled DPVA with this feature
will remain just north/northeast of the area across south
central/southeast lower Michigan this afternoon, although
combination of WAA and tightening low/mid level fgen fields across
the Great Lakes region should promote a period of fairly strong
upward vertical motion in the 900-750 hPa layer this afternoon
across especially northeast third of the area. With better dynamics
remaining to the north...warming mid level profiles...and lack of
appreciable deep moisture will continue with a dry forecast across
the northeast this afternoon. There could be a relatively brief...low
chance of rain showers across the north/northeast early this
evening immediately behind the front but given low confidence and
any potential precip amounts likely totaling a trace to a few
hundredths have opted to keep PoPs below mentionable levels at
this time. Otherwise, dry conditions for remainder of the forecast
area this afternoon and tonight with significant mid level drying
later this afternoon/evening. Northerly flow and some increase in
lake-induced instability developing post-frontal tonight should
keep some stratocu around downwind of Lake Michigan, but
relatively shallow nature to cold air advection should limit any
lake-induced convective depths and will maintain dry forecast.


.LONG TERM...(Monday through Saturday)
Issued at 343 AM EDT Sun Oct 23 2016

Temperatures closer to seasonable levels will arrive for the
Monday-Tuesday period with western periphery of post-frontal low
level thermal troughing still anchored back across the western
Great Lakes. Lake effect clouds should persist through Monday, but
otherwise mainly clear/partly cloudy skies anticipated. Thermal
advections to remain weak through Tuesday, although increasing mid
level cloudiness may take a few degrees off highs on Tuesday,
likely limited to lower 50s far northeast, to upper 50s southwest.
Coldest night of the forecast should be Monday night with lows
into the mid/upper 30s likely. However, with end of climatological
growing season, no additional frost headlines will be issued.
Onset of stronger low/mid level warm advection by Tuesday night
will likely be associated with some warm advection-wing type rain
and have maintained chance PoPs for Tuesday night northern two-
thirds of the area.

Primary feature of interest for remainder of long term period
will be PV anomaly from the eastern Pacific which
emerges/amplifies in lee of Rockies Tuesday night and becomes more
influential for local area by Wednesday. Some northward trend
noted past few days in deterministic guidance consensus, which
agrees fairly well with general GEFS idea. Given this northward
trend did add iso thunder mention for the late Wed afternoon/night
period primarily across southern half of the area. With strong
advective fields and respectable dynamics with this system have
maintained ramping up of PoPs from west to east Wednesday, and
likely PoPs most areas for Wednesday night. Scattered showers may
persist into Thursday morning as upper trough axis moves through,
but should trend to drier conditions in the afternoon.

Forecast confidence in terms of additional precip chances dwindles
for the Thursday night-Saturday period with broad low level
baroclinic zone likely positioned in the region with a potential
of additional waves progressing through upstream ridge. Hard to
discount at least some lower end precip chances in this pattern,
with current indications suggesting temps near seasonable levels.


.AVIATION...(For the 12Z TAFS through 12Z Monday Morning)
Issued at 629 AM EDT Sun Oct 23 2016

VFR/dry conditions will persist through the period as hybrid
clipper tracks southeast through Michigan later today. Diurnal
mixing and shot of warm advection within ramped low level
southwest flow should yield a somewhat breezy afternoon before
trailing cold front drops south through KSBN early evening and
KFWA late evening. Post-frontal saturation/cooling and weak
theta-e flux off Lake MI may allow a low VFR stratocu deck to
settle into KSBN later tonight. Mainly clear skies expected


LM...Small Craft Advisory from 4 PM this afternoon to 4 PM EDT Monday
     for LMZ043-046.



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

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