Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 151056

Area Forecast Discussion
National Weather Service Northern Indiana
556 AM EST Sun Jan 15 2017

Issued at 414 AM EST Sun Jan 15 2017

Other than some patchy fog this morning, expect dry conditions
with highs in the 30`s today. There are chances for freezing rain
tonight into late Monday morning. Minor ice accumulations are
possible. Any freezing rain tonight into Monday morning will
transition to rain throughout the day Monday. Rain will continue
into Wednesday morning. We may even hear some thunder Monday night
into Tuesday morning. Rainfall is expected to cause rises on area
rivers, with the potential for minor flooding. Otherwise, expect
dry conditions Wednesday afternoon into the start of the weekend
with above normal temperatures.


.SHORT TERM...(Today and Tonight)
Issued at 414 AM EST Sun Jan 15 2017

Other than some patchy fog this morning, we`ll see a quiet start
to the short term, with surface high pressure infiltrating the
region. Clouds will be on the increase from SW to NE throughout
the day as the next system approaches the area.

00Z guidance is in disagreement about the chances for precipitation
tonight. The only agreement thus far is that precipitation will
arrive after 06Z. Beyond that, the 00Z NAM remains dry through the
overnight and early Mon morning hours. The 00Z GFS/ECMWF/GEM still
attempt to bring in some light precipitation after 06Z. The primary
difference appears to lie in how quickly the surface high pressure
drifts eastward, with the NAM the last to move it out of our CWA.
The GFS/ECMWF/GEM also have a bifurcation in the isentropic ascent
along the 290K sfc that funnels the moisture northeastward into our
area, whereas the NAM is slower to do this.

Slowed the timing and lowered the pops just a hair overnight, with
the best chances developing from SW to NE after 9Z. As far as
precipitation type, surface temps will be below freezing and the
warmer air aloft arrives fairly quickly-so I have freezing rain. Ice
accumulation (0.04" or less) before 12Z will be primarily west of US
31 and along/south of US 30. An advisory may be needed, but given
lower confidence and per collaboration with the neighbors, decided
to hold off for now.


.LONG TERM...(Monday through Saturday)
Issued at 414 AM EST Sun Jan 15 2017

The NAM is still the outlier from 12-21Z Monday, being the only
one not to bring in precipitation due to a lingering surface high
pressure. The GEM/GFS/ECMWF move a band of precipitation
associated with weak isentropic ascent from south to north through
the day, with the best chances west of US 31 through 15Z, and west
of I 69 through the 21Z time frame. Precipitation type looks to be
freezing rain through about 15Z for most areas, and transitions to
rain from south to north shortly thereafter. Additional ice
accumulations of around 0.03" or less are possible across most
areas, with the highest amounts most likely west of I 69. It is
possible early Monday evening that we see a brief transition back
to freezing rain in our far NE, mainly in Hillsdale County
Michigan, which could lead to minor ice accumulations-but after
06Z expect p-type to be all rain.

Otherwise, as we inch towards late Monday afternoon into Tuesday,
the stronger upper level forcing and support arrives to kick things
up a notch. Luckily, with warmer air advecting into the region
precipitation type through this period will be all rain. Model
agreement during this time is also a bit better as far as the larger
scale pattern goes, at least through Tuesday afternoon. At 300mb we
see a broad area of strong divergence entering into IL and western
IN around 00z associated with coupled northern/southern stream jets.
This stronger upper level support drifts slowly eastward through 12Z
Tuesday. At the same time, the 500mb trough approaches from the
west, with stronger 850-500mb Qvector convergence seen CWA wide. The
associated surface low pressure system lifts northeast from MO/IL/IA
into Michigan, with a swath of PWATs around 1" pumping in from the
gulf ahead of the surface cold front. Long story short, confidence
is higher for a decent period of rain Monday evening into Tuesday
night. Steeper mid level lapse rates and a weak area of MUCAPE
arrive during the 00-12Z Tuesday time frame, and as mentioned in
previous discussions-would not be surprised to hear a rumble of
thunder. I added a slight chance of thunder in for now.

Model disagreement becomes more apparent...yet better than it was in
previous runs...after the first shortwave swings through and the
cold front dives east of our area late Tuesday afternoon.
Discrepancies are mainly in the handling of the first upper level
wave as it is absorbed into the broader-scale trough, and the
subsequent deepening of that second trough and how fast it moves
through Wednesday. Kept the consensus slight chance/chance pops in
for now Tuesday night into Wednesday afternoon, with a chance for a
rain/snow mix through Wed AM as the temps fall.

Of course with expected rainfall, we will see rises on area rivers,
which will likely lead to some minor flooding. See our AHPS page for
detailed river forecasts across the area.

Wednesday afternoon into Friday should be dry, and will feature
climbing temperatures that rise well above normal. Highs Wednesday
will be in the upper 30`s and 40`s, and then by Friday we will see
highs in the upper 40`s and 50`s. Saturday-Sunday we will be in the
50`s, with some areas across our far south reaching near 60. Records
are in the 60`s for both Fort Wayne, IN and South Bend, IN for this
time period-so it looks like we`ll be just shy of those. Saturday we
have a chance for rain as the next low pressure system moves through
the area, but I kept lower chance consensus for now given larger
scale disagreement in the models.


.AVIATION...(For the 12Z TAFS through 12Z Monday Morning)
Issued at 554 AM EST Sun Jan 15 2017

Br fairly widespread across the area this morning and will be
slow to mix out with considerable high clouds and light winds.
Expect vsbys will improve to vfr by aftn. Flight conditions should
deteriorate again tonight as a low pressure system and associated
warm front approaches. There is a low chc of freezing rain late in
the period but held off mentioning in tafs attm.





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