Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 172100

Area Forecast Discussion
National Weather Service Northern Indiana
400 PM EST Fri Feb 17 2017

Issued at 350 PM EST Fri Feb 17 2017

A warm front lifting across the Great Lakes region has allowed an
unseasonably warm air mass to overspread the area. The much above
normal temperatures will continue this weekend and through much of
next week. A weak cold front will drop south across the southern
Great Lakes on Saturday, but will provide only some minor cooling
closer to Lake Michigan. Dry conditions will persist through
Monday night, with the next chance of rain for Tuesday. Low
temperatures tonight will drop into the lower 40s. Record or near
record warmth is in store once again Saturday with high
temperatures in the lower to mid 60s. Slightly cooler conditions
can be expected closer to Lake Michigan across southwest lower
Michigan Saturday afternoon.


.SHORT TERM...(This Evening through Saturday)
Issued at 350 PM EST Fri Feb 17 2017

The beginnings of a prolonged period of unseasonably mild
conditions will continue to be the primary short term focus.

Surface warm front has cleared most of the forecast area, with
far northeast portions just now getting into the interface of this
warm front. Temperatures south of this warm front rapidly shot
into the upper 50s and lower 60s this afternoon with record highs
broken at both Fort Wayne and South Bend. Additional details
regarding record high max temps and record high min temps over the
next several days can be found in the climate section below.
Quiet conditions in store for tonight as mid level height rises
continue to push across western Great Lakes region. Upper flow
pattern remains somewhat disjointed upstream with cut-off PV
anomaly slowly meandering across the Southern Plains, and an open
northern stream wave working across the northern tier of CONUS.
Progression of this northern stream wave will allow weak sfc
trough/cool front to sag across southern lower Michigan/far
northern Indiana on Saturday before losing integrity. While most
of the area may be prone to just slightly cooler low level air on
Saturday, subtle increases in mixing heights should offset this
influence for most locations providing highs similar to that of
today. The possible exception would be across the far northwest
where more of a westerly low level flow trajectory off Lake
Michigan will provide some cooling to near the lakeshore. High
clouds will increase some across especially southern half of the
area Saturday as southern cut-off PV anomaly drifts across lower
MS Valley.


.LONG TERM...(Saturday Night through Friday)
Issued at 350 PM EST Fri Feb 17 2017

Unseasonably mild conditions will continue through much of this
forecast period. A couple of chances of rain for the long term,
the first Tuesday, and then again toward end of the period as
medium range models continue to depict more substantial storm
taking shape across central CONUS.

Mid/upper level height rises to commence again Saturday night in
advance of the next upper level trough reaching western CONUS.
Low level anticyclone tracking across the area on Sunday should
provide a weak enough gradient for a lake breeze to develop with a
better chance of more substantial lakeshore cooling by Sunday
afternoon. Guidance has wavered back and forth in some of the
details regarding how to handle this next trough in terms of
budgeting of the northern/southern stream. Latest GFS has come in
a bit more phased and slightly stronger with the northern stream
wave which would result in a better chance of rain by Tuesday as
this idea would allow for a more substantial narrow moisture axis
to advect into the area. ECMWF/GEM remain a bit slower and weaker
and given this spread have slightly lowered blended PoPs which
gives high chance/low likely PoPs for Tuesday. Associated frontal
boundary will stall across the area for midweek behind this system
with no intrusions of significantly cooler air.

Medium range models have been somewhat consistent in a better
phased, more significant upper trough affecting the area toward
the end of the forecast period. Some expected timing differences
persist, but the overall general idea is similar with a resurgence
of low level theta-e advection late Thursday/early Friday.
Maintained categorical PoPs for the end of the period, and
depending on track may need to add some thunder mention toward end
of the period eventually.


Issued at 350 PM EST Fri Feb 17 2017

A prolonged period of unseasonably mild conditions is in store
through the middle of next week. Below are record daily high
maximum temperatures and record daily high minimum temperatures
for the next several days for Fort Wayne and South Bend:

Fort Wayne

Date        Record High Max Temp        Record High Min Temp

2/18          61(1994 and 1961)                42(1981)
2/19             67(1930)                  43(1981 and 1913)
2/20             67(1930)                      47(1930)

South Bend

Date        Record High Max Temp        Record High Min Temp

2/18             63(1961)                      46(1981)
2/19             65(1930)                      48(1994)
2/20          65(1983 and 1930)                46(1930)


.AVIATION...(For the 18Z TAFS through 18Z Saturday Afternoon)
Issued at 1226 PM EST Fri Feb 17 2017

Quiet aviation weather conditions for this forecast period. Warm
front has cleared terminals with south-southwest winds of 10 to 15
knots expected to prevail through this period. Some increase in
high clouds is expected by Saturday morning in response to slow
eastward progression of cut-off PV anomaly across the Southern
Plains, but VFR conditions should prevail. Sfc trough tracking
across the Great Lakes tonight should be accompanied by downstream
modest low level jet across northern Indiana, and have maintained
LLWS mention tonight from previous forecast.




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

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