Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 120522
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
1222 AM EST Thu Jan 12 2017

.SYNOPSIS...
Issued at 1218 AM EST Thu Jan 12 2017

Occasional rain will continue this morning as a cold front moves
across the area. The rain could end as a brief period of freezing
rain across southwest Michigan and northwest Indiana. High
pressure will move into the Great Lakes tonight and Friday
resulting in dry conditions. Some freezing rain is possible, mainly
across southern portions of our area, over the weekend as low
pressure moves through the Ohio Valley.

&&

.SHORT TERM...(This Evening through Thursday)
Issued at 342 PM EST Wed Jan 11 2017

Primary forecast challenges for the short term will be rain/iso
thunder tonight, and fog.

Strong low level thetae advection to continue tonight with axis of
highly anomalous moisture working into the area. Low clouds and fog
have overspread approximately southwest half of the area late this
afternoon, with some concern of patchy dense fog over the next
several hours across far southwest/western portions of the area.
Will monitor trends over next few hours for the need for any
advisories.

In terms of precipitation, a couple of distinct waves to bring
enhanced chances of rain. One of these waves skirting across the
Ohio Valley through early evening will bring greater coverage of
rain across far southeast sections. Another short wave across
northwest Illinois will race across southern lower Michigan this
evening also bringing an increase in rain shower chances. By mid
to late evening a larger scale upstream trough should allow for
strengthening low level frontogenesis forcing in association with
strong baroclinic zone located just northwest of the area. This
should result in an increase in rain showers and a potential of
more impressive rainfall rates late evening into the overnight
hours. Air mass advecting into the area will be characterized by
PWATS in excess of an inch, and concern persists for total
rainfall amounts in excess of an inch and possibly approaching
localized two inch amounts where stronger frontogenesis forcing
materializes. Favored area for these potential heavier rainfall
amounts still appears to be across southeast portions of the area,
roughly along and southeast of the US Route 24 corridor. Some
localized minor flooding will be possible with the corridors of
heavier rainfall, along with continued rises on some area rivers.
Will continue to carry isolated thunder mention into Thursday
morning with weak elevated instability.

Non-diurnal temp trends for this evening with temperatures rising
into the 40s and 50s, and even a chance at extreme south/southeast
making a run at the 60 degree mark for a time. Temps will drop
sharply across the northwest half overnight as frontal boundary begins
to progress through the area.

Rain will continue Thursday morning, with greatest
coverage/intensity across southeast half. One thing that will need
to be watched is the potential of a brief period of light freezing
rain/freezing drizzle across northwest portions of the forecast
area. Low levels should dry out rapidly, but enough moisture beneath
the frontal inversion and shallow cold air could promote a period of
freezing drizzle before precip ends. Temps on Thursday will be
steady to slowly falling.

&&

.LONG TERM...(Thursday Night through Wednesday)
Issued at 342 PM EST Wed Jan 11 2017

Dry conditions will develop by Thursday evening as a very dry
low/mid level air mass advects across the southern Great Lakes
region. A strong low level baroclinic will stall out just south
of the local area as a strong 1045 mb high becomes established
across the Great Lakes.

A rather complicated upper level flow evolution will commence for
the weekend with cut-off upper PV anomaly setting up across
southwest CONUS and a series of smaller scales waves approaching
from the northern stream. Consensus of medium range model guidance
remains suppressed enough with the boundary that icing concerns with
initial warm advection ramp up may not be a big issue as far
north as local area for Friday night/Saturday, but will maintain
chance PoPs for freezing rain mainly across the south. A period of
perhaps greater concern that will need to be watched is for some
time in the Sunday/Sunday night period when a leading stronger
warm advection wing could spread across the area with a risk of
some ice accumulation. Have opted to keep just chance PoPs with
any freezing rain mention at this time given low confidence in
timing and placement of warm advection wing type forcing. Cut-off
PV anomaly to eventually lift across central CONUS early next week
with greater chances of precip for local area, but an eventual
preference to liquid precip type for Monday-Tuesday. Any heavier
rainfall during this period may cause some renewed/aggravated
hydro concerns. Milder temperatures will be in store for the early
portions of next week as this upper PV anomaly approaches.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday Night)
Issued at 1218 AM EST Thu Jan 12 2017

Band of shra has moved out ahead of cdfnt movg through
nw IN. Winds at FWA should diminish and veer wly after shra move
through but cdfnt movg slowly and not expected to reach FWA until
shortly after sunrise. Vort max lifting ne from KS expected to
cause more shra to move across nrn IN this morning keeping flight
conditions ifr. Some potential for zr at SBN but for now sided
with mos temp fcst just above freezing. High pressure building
into the upr midwest/upr grtlks tonight should result in
conditions improving to vfr.

&&

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

$$

SYNOPSIS...JT
SHORT TERM...Marsili
LONG TERM...Marsili
AVIATION...JT


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