Merrillville, Indiana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

151
FXUS63 KLOT 310000
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
700 PM CDT Sun Mar 30 2025

.KEY MESSAGES...

- A period of below average temperatures is expected Monday and
  Tuesday before another storm system (with a threat for severe
  weather) arrives on Wednesday.

&&

.DISCUSSION...
Issued at 354 PM CDT Sun Mar 30 2025

Thunderstorms have cleared much of the CWA as of 4pm, with some
lingering lightning strikes possible in showers east of I-57
over the next couple hours as the cold front sweeps eastward.
Southwest winds will veer northwest while gusting to 30 mph
tonight as much colder air arrives.

As a deformation axis associated with the passing mid-level
wave brushes far northern Illinois tonight, light rain should
mix with and possibly change over to non-accumulating snow for a
few hours before ending by around sunrise Monday.

After a chilly start to the work week temperatures will
gradually moderate toward midweek when multiple rounds of
thunderstorms are possible late Tuesday night through
Wednesday, some of which could be severe.

Another low pressure system is forecast to lift across the
Upper Midwest toward midweek which will bring yet another period
of inclement weather to the local area. Guidance has trended
more consistently earlier with the onset of showers and
thunderstorms, with strong to possibly severe thunderstorms
moving into the area as early as the pre-dawn hours early
Wednesday morning (potentially in a weakening phase) near and
west of I-39. This coincides with where the Storm Prediction
Center introduced a Level 2 of 5 severe weather threat on Day 3.
Additional waves of showers and storms are possible through the
day on Wednesday. Depending on the timing of storms exiting in
the morning there is a window for another round of strong to
severe storms in the afternoon and early evening. Similar to
today`s (Sunday) setup, given the conditional nature of the
severe threat, expect updates over the coming days to the
forecast.

Uncertainty increases late week into the weekend when another
system is forecast to move across the broader region, though
differences in its placement remain. For now NBM rain chances
seem appropriate (highest south of I-80) with temperatures
generally in the 50s to lower 60s.

Petr/Kluber

&&

.AVIATION /00Z TAFS THROUGH 06Z TUESDAY/...
Issued at 700 PM CDT Sun Mar 30 2025

Forecast concerns for the terminals...

- Gusty west-northwest winds this evening gradually subsiding
  through Monday afternoon.

- Period of light rain tonight, possibly mixed with snow near
  RFD, along with MVFR to IFR ceilings.

- Lake breeze expected to move through the Chicago area
  terminals Monday afternoon/evening.

The dry slot of a stout spring storm system has moved into
northern IL and northwest IN which has allowed precipitation to
conclude for the time being. Winds on the other hand have
remained gusty with peak gusts in around 30 kts still being
observed. These gusts are expected to gradually taper this
evening as the surface low (currently over central Lake
Michigan) moves east, but gusts of 20-25 kts will prevail
through Monday afternoon.

While the terminals will enjoy a break in the weather this
evening, a shortwave disturbance is pivoting across central IA
and has resulted in a robust band of rain and snow showers. This
band of precipitation is expected to swing into northern IL
after 03z this evening and bring a period of showers to the
terminals through early Monday morning. Given that forecast
soundings show the majority of the moisture for the
precipitation tonight will be below the snow growth region, the
expectation is for rain to be the dominant precipitation type.
However, some snow may mix in at times especially near RFD where
temperatures are forecast to be coldest. Regardless, no snow
accumulation is expected.

Aside from the precipitation, ceilings will also be lowering
into the 1500-2000 ft (MVFR) range this evening and will remain
as such through Monday afternoon before clouds scatter out.
Though, there is a growing concern for a period of IFR ceilings
at the terminals with the aforementioned precipitation which has
been accounted for in TEMPO groups due to lower confidence. The
exception to this however is GYY which at this time looks to be
far enough south to avoid precipitation and IFR ceilings, but
we will monitor trends closely.

Finally, a lake breeze is expected to develop Monday afternoon
and move through the Chicago area terminals during the late
afternoon and early evening hours. Winds behind the lake breeze
will become easterly with speeds generally around 10-12 kts
where they will remain through much of Monday night. As per
typical with lake breezes, confidence in exact timing is
somewhat low so expect changes to occur as the forecast gets
refined.

Yack

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 4 AM CDT Tuesday for the IL and IN
     nearshore waters.

&&

$$

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