Hammond, Indiana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

576
FXUS63 KLOT 150028
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
728 PM CDT Wed May 14 2025

.KEY MESSAGES...

- Summer-like warmth continues through Friday, with record
  breaking heat possible Thursday.

- Conditional threat of severe weather exists Thursday afternoon
  and evening (Threat level 2 to 3 out of 5), dependent on
  storms forming.

- Threat of rapid fire spread Thursday and especially Friday due
  to a combination of strong winds and dry conditions.

&&

.DISCUSSION...
Issued at 308 PM CDT Wed May 14 2025

Through Thursday:

Following the possibility for some isolated showers and
thunderstorms late this afternoon across interior sections of
northern IL into northwestern IN, we are looking at a fairly
quiet and mild evening (particularly for inland areas). However,
similar to yesterday, we will have to keep a close eye on the
dense marine fog, which remains in place across southern Lake
Michigan this afternoon. I suspect that the continued light
onshore easterly flow will again push some of this fog inland
across far northeastern IL after sunset this evening.
Accordingly, we will have to monitor the need for another dense
fog advisory for at least parts of Lake county IL and Cook this
evening and tonight. Any dense fog that moves inland will
quickly improve by mid morning on Thursday.

There also continues to be a low chance (~20%) for a few
showers and thunderstorms overnight. This as isentropic upglide
(warm air advection) kicks up along a modestly increasingly
southerly low-level jet late tonight. It still appears any
activity that develops into our area will remain low in areal
coverage, thus most will remain dry overnight.

Thursday is still shaping up to be an unseasonably hot day
(with near record high temperatures), with a conditional threat
of severe late afternoon and early evening storms. This as a
strong sub-985 mb surface low tracks northeastward while
occluding across eastern South Dakota and the Upper Midwest late
Thursday into Thursday night. Our area will become oriented
solidly within the warm sector of this cyclone following an
early morning warm frontal passage. Breezy south winds (gusting
up around 30 mph) in the wake of this warm front will drive a
thermal ridge northeastward into the Lower Great Lakes, with 925
mb temperatures progged to increase to around +25C. Locally
climatology suggests that this will support lower 90s high
temperatures for the area Thursday, which is right around the
record high`s for the 15th.

The warm sector airmass is expected to remain capped through
most of the day by an EML. Accordingly, the threat for storms
through at least 3 PM Thursday afternoon will remain very low.
However, the chances for at least isolated storm development
will begin to ramp up after 3 PM as a cold frontal/dry line
feature shifts eastward into northern IL. There continues to be
uncertainty with the overall storm coverage with southward
extent into northern IL later in the afternoon, owing to
lingering capping and rather weak large scale forcing. However,
there are signs in the guidance that the exit region of an
upper-level jet will try to nose into northeastern IL towards
the early evening period just as modest mid-level height
falls/cooling spread into the area. This is should thus foster a
gradual uptick in storm coverage along and ahead of the surface
boundary into Thursday evening as cap weakens.

What remains somewhat unclear at this time is how quickly this
uptick in storm development occurs along the frontal boundary
into early Thursday evening. If it takes a bit too long, the
higher storm coverage may end up occurring largely east-
northeast of our area as the front quickly shifts out over Lake
Michigan. Nevertheless, it appears that at least some isolated
to widely scattered storms may break out across parts of
northern IL late in the day. Assuming they do, the thermodynamic
and kinematic environment in which they develop will be very
supportive of organized severe storms, particularly supercells.
The presence of very steep mid-level lapse rates (700-500 mb 8C+
per km) suggests that instances of large to very large hail
(2"+ in diameter) will be possible with these storms, and may
end up be the primary severe threat in our area. However, some
instances of damaging winds and a possible tornado cannot be
ruled out. Expect the the threat of storms to quickly end from
west-to-east following the frontal passage into early Thursday
evening.

KJB


Friday through Wednesday:

In the wake of Thursday`s conditional severe weather risk, a
substantial mid-level dry layer atop a residual EML just above
the surface will advect across the area Thursday night into
Friday. Meanwhile, near-record low MSLP values for May of
potentially sub-980hPa over Minnesota on Friday will generate
anomalously strong synoptic winds over the forecast area. The
combination of RH values lowering to 25% or less and southwest
winds gusting to around 40 mph amid deep diurnal mixing into the
dry air mass will support the potential for critical fire
weather conditions Friday afternoon. Rapid spread of brush fires
is possible with any remaining dry/dead vegetation from prior
seasons. Additionally, fine fuels have started drying out given
the recent lack of rain and persistent days of lower RH values.
A Fire Weather Watch may be needed as early as the next forecast
cycle.

In addition to the windy and dry conditions Friday, have added
patchy blowing dust for much of interior northern Illinois away
from the Chicago/Rockford metros as soils in fields could result
in locally reduced visibility (particularly for NW to SE
oriented roads).

Even with the expected dry weather and brush fire concerns,
impressive lapse rates of 8-8.5C/km through much of the
troposphere will still promote high-based (10kft) cumulus during
the afternoon. A subtle mid-level impulse quickly tracking from
the western Rockies to the mid-Mississippi River Valley could
induce deeper growth of the high-based cumulus and ultimately
result in isolated thunderstorms late in the afternoon and early
evening. Associated DCAPE values approaching 1500 J/kg amid a
deep sub-cloud inverted-V profile would support locally damaging
wind gusts with any thunderstorms.

A strong Hudson Bay high will gradually replace the strong
surface low through the weekend, allowing for cooler conditions
to filter over the area. High temps in the 70s area-wide on
Saturday will settle into the 50s along the shore to 70s well
inland on Sunday as a backdoor cold front crosses the area from
the northeast Saturday night. Next week, overall guidance is
painting another period of active weather as deep troughing over
the western CONUS slows or potentially cuts off over the region
by midweek.

Kluber

&&

.AVIATION /00Z TAFS THROUGH 06Z FRIDAY/...
Issued at 716 PM CDT Wed May 14 2025

Key Messages:

- Potential for fog and IFR/LIFR ceilings at ORD, MDW, and GYY
  tonight.

- 30-40% chance for thunderstorms to affect the terminals late
  tomorrow afternoon. If storms develop, they will likely become
  strong to severe.

- Gusty southerly winds tomorrow afternoon, followed by a
  southwesterly wind shift behind a cold front during the late
  afternoon/early evening.


Similar to last night, a bank of marine fog/low stratus is
expected to ooze inland this evening and may affect ORD, MDW,
and GYY at some point tonight. Confidence is low in the extent
to which any of these sites will be affected and when, but most
of the latest forecast guidance favors this fog/stratus bank to
at least get very near ORD by late evening, with some guidance
still suggesting that it may also get close to or reach MDW as
well. Webcams and visible satellite imagery also shows that the
edge of this fog/stratus is very close to GYY, and with winds
still out of the northeast and inland boundary layer mixing
expected to subside as the Sun sets, some reduced visibilities
and lowered ceilings appear probable there until a southeasterly
wind shift later this evening pushes this low-level moisture
away from the GYY airfield. For now, opted to introduce some
targeted TEMPO groups for reduced visibilities and lower clouds
in the 00Z ORD and GYY TAFs. However, amendments will likely
need to be made based on observational trends as the
evening/night goes on.

While an isolated shower or storm can`t entirely be ruled out
tomorrow morning, the terminals will likely remain dry through
at least tomorrow afternoon. Late on in the afternoon, a cold
front will approach the area from the west, and as it gets close
to the terminals, explosive thunderstorm development is
possible. Confidence in whether a storm will develop over or
near a TAF site is still only low-medium (about a 30-40% chance
at any particular site), and thunderstorm coverage will likely
only be scattered at best. However, wherever storms do develop
will likely be subject to strong winds and/or large hail, in
addition to lightning and visibility reductions. The threat for
storms at the terminals should end by about 00Z or 01Z as the
cold front pushes through the area.

Lastly, south-southeasterly winds will become gusty during the
late morning, and pick up in intensity during the afternoon --
possibly gusting to around 30 kts at times. The prevailing wind
direction will likely turn due south or just west of south at
some point during the afternoon before turning southwesterly
after the passage of the cold front during the late
afternoon/early evening.

Ogorek

&&

.MARINE...
Issued at 716 PM CDT Wed May 14 2025

Dense fog continues to plague the southern half of Lake
Michigan in response to humid air pooling over the cool lake
waters. As winds adopt a southerly component overnight, fog may
begin to drift away from the Indiana shoreline. Fog may then
linger along the Illinois shoreline through at least tomorrow
morning but possibly into the afternoon. A Dense Fog Advisory
remains in effect for much of southern Lake Michigan through
tomorrow morning.

Tomorrow afternoon, thunderstorms appear poised to develop just
west of if not directly over Lake Michigan. Any storm may
produce gale to storm force winds and damaging hail. A brief
period of southwesterly gale force winds cannot be ruled out
behind the storms, as well.

Finally, a period of southwesterly gale force winds may materialize
Friday afternoon, particularly northwest of Gary, Indiana. A
Gale Watch may be needed soon.

Borchardt

&&

.CLIMATE...
Issued at 643 PM CDT Wed May 14 2025

Record high temperatures are possible on Thursday May 15.

Here are the current record highs for May 15:

Chicago: 91 in 1962

Rockford: 90 in 1944

Castro

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Dense Fog Advisory until noon CDT Thursday for Winthrop Harbor
     IL to Gary IN.

     Dense Fog Advisory until 10 PM CDT this evening for Gary to
     Burns Harbor IN-Burns Harbor to Michigan City IN.

&&

$$

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