Kokomo, Indiana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

343
FXUS63 KLOT 131718
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1218 PM CDT Thu Mar 13 2025

.KEY MESSAGES...

- Powerful spring cyclone will impact the area Friday afternoon
  into Saturday and bring with it:
 - Very windy and unseasonably warm Friday afternoon and Friday
       night, wind gusts to around 45 mph expected.
     - Increased threat of grass/brush fire spread Friday afternoon.
 - Fast moving line of showers and thunderstorms Friday night,
       with threat for severe thunderstorms
     - Very strong, possibly damaging winds, Saturday morning/early
       afternoon with some gusts over 50 mph likely

- Above normal temperatures again Monday/Tuesday

- Precip chances return middle of next week

&&

.DISCUSSION...
Issued at 335 AM CDT Thu Mar 13 2025

Through Saturday:

Synoptic overview:

Quasistationary front that`s been stalled out well south of the
area will begin lifting northward tonight in response to
pressure falls ahead of the developing lee cyclone. Intense/rapid
lee cyclogenesis will take over the central Plains tonight into
Friday morning, fostered by an incredibly intense upper-level
jet streak (120+ kts progged at 500 mb) and corresponding left
exit region fanning out across the central Great Plains. Surface
pressure falls on the order of 10 mb/6 hours will support the
quick development of a mid 970s mb low by midday over western
Kansas. This powerful low and associated negatively tilted,
sharp upper trough with an attendant closed mid-upper level low
will eject northeastward toward the upper Mississippi Valley
Friday afternoon into Friday night.

Through tonight:

Today will be a near carbon copy of Wednesday, only with
temperatures around 5F warmer. The exception will be near and
immediately downwind of the still very chilly Lake Michigan.
By late tonight a 35kt 850mb low level jet will near the axis of the
Mississippi River and result in strengthening warm air advection.
Have maintained a slight chance of showers overnight in the Rockford
vicinity, but elsewhere it should be dry.

Friday temps:

Warm front should clear all but the Illinois north shore by
mid-late morning Friday. Buckling mid-upper level ridge over the
region should send core of the upper level jet and associated
cirrus north of the area by late morning with skies becoming
mostly sunny. ECMWF and GFS both have 925mb temps warming to
near 20C by late afternoon, which given the mostly sunny skies
should allow temps to get at least into the upper 70s, with it
looking increasingly likely that some locations will tag 80 degrees
Friday afternoon. Thanks to the backed south-southeasterly synoptic
flow, it will take much of the afternoon and possibly the early
evening before the warm front can finally reach the Lake County IL
shore. As the higher dewpoints meet the lake chilled air, some dense
marine fog is certainly possible along on the cool side of the front
along the IL north shore.

Friday afternoon/evening winds:

Quickly tightening pressure gradient amidst a deeply mixed boundary
layer should set the stage for very strong southerly winds Friday
afternoon. By early/mid afternoon, bufkit soundings over western CWA
show boundary layer mixing up to 40kt winds, which given the
sunshine should be able to mix to the surface in gusts, particularly
by late afternoon. The very strong winds will likely continue into
the evening hours with strong pressure falls and turbulent mixing
likely keeping very strong gusts going. If gusts ease a bit at
sunset, they should ramp back up during the early evening as 50-60kt
low level jet around 1500ft AGL overspreads the area. This very
strong low level jet and very little diurnal cooling/decoupling
should result in frequent gusts of 40-50 mph Friday evening with a
few gusts over 50 mph not out of the questions. In collaboration
with DVN/ILX, have hoisted a wind advisory for Friday afternoon and
evening, starting it at noon western CWA and 3 pm eastern CWA. These
start times may be a little early, but it shouldn`t be too long
after those start times that we start to see advisory level gusts.
The advisory level gusts should abate in the wake of the fast moving
convective line moving across the CWA, which looks to exit out
eastern CWA not too long after 06z.

Friday night storms:

Forecast reasoning hasn`t changed much at all over the past
couple of days.

Vigorous thunderstorm development is expected Friday afternoon
across southwest Iowa arcing southeast and south across Missouri
as the main upper jet streak spreads across a sharpening
dryline. While a significant cross-boundary component to deep
layer shear vectors is forecast, which would normally tend to
promote discrete or semi-discrete storm modes, the significant
nature of synoptic scale forcing with this system looks to
encourage a rapid development towards a line of strongly-forced
convection. This activity will quickly become severe across
central and eastern Missouri and into Iowa.

The magnitude/expansiveness of the severe threat into our forecast
area remains uncertain. It still appears like that low level
moisture will mix out to some degree Friday afternoon across much of
the warm sector of the cyclone, including a good chunk of Illinois.
Assuming this occurs, it should keep instability confined to a
fairly narrow ribbon pooled moisture immediately ahead of the
surging dryline. It appears likely that this QLCS will outrun that
narrow ribbon of pooled moisture and instability as it matures and
accelerates eastward. During the evening as this QLCS moves east of
the Mississippi River it should be venturing into an increasingly
marginal/more hostile environment with respect to boundary layer
based instability. This should result in weakening trend in the
storms as they approach and/or move across our CWA mid-late evening
Friday.

How quickly that weakening trend occurs will be a critical in
determining both the magnitude and eastward extent of the severe
weather threat. If greater than expected boundary layer
instability persists well into the evening and/or synoptic
forcing help maintain the QLCS longer, then the threat for
significant winds gusts (65kt+) and QLCS type tornados will
increase in our area. In line with the latest SWODY2, it
appears the highest severe probabilities in our area will be
across western and southwestern CWA with threat decreasing with
eastward extent. It is worth noting, that given the extreme low
level wind fields, even innocuous looking showers could mix severe
criteria wind gusts to the surface, so the wind threat with the QLCS
could persist longer then the lightning and heavy rain threat!

Synoptic high winds early Saturday:

Potential for a period damaging winds across portions of the
area is increasing. As the dry slot of this 970s mb cyclone
punches into the area, deepen mixing into very strong wind
field should promote increasingly strong and potentially
damaging wind gusts Saturday morning into the early afternoon.
Bufkit soundings from both the NAM and GFS show peak boundary
layer winds of 50-60kt and mean BL winds of 40-45kt. Given the
propensity for very effective downward momentum transfer within
the dry slots of intense mid-latitude cyclone, it seems likely
that there will be a couple/few hours with some 50kt+ gusts.
Strongest wind fields within this dry slot begin move east of
our CWA between 18-20z, so our likely window of strongest winds
appears to be 15-19z. Given the growing confidence in the
potential for occasional damaging wind gusts, will be issuing a
high wind watch for about the northern 2/3rd of the CWA.

- Izzi

Saturday Night through Wednesday:

The surface low should be somewhere over Lake Superior Saturday
night and lifting into Ontario into Sunday morning. With the amount
dry air moving in, PoPs were kept in the slight chance/chance range
through Sunday afternoon for the potential of some wrap around
precipitation. Lastly, with the amount of cold air advection moving
in behind the low, there is the potential for some snow to mix in
with the rain Saturday night into Sunday morning. Maybe there is a
light dusting for areas west of the Rockford Metro, but otherwise no
accumulations are expected.

An upper level ridge access will slowly slide eastward early next
week. As winds swing back to the south, warm air advection will help
drive temperatures back into unseasonable territory with low 60s
possible on Monday and potentially 70s (mainly south and west of the
I-80 corridor) on Tuesday. AS the warm air advection increases early
next week, another low level jet will develop and create breezier
winds, especially in the afternoons.

For Tuesday night and beyond, models have been consistently showing
the next upper level wave coming out of the Rockies triggering the
next surface low to move east toward northern Illinois. Firstly, the
signal for this surface low is nowhere near as strong as the low
impacting the area this weekend. Secondly, ensembles are still
struggling with the location and strength of this system. It could
arrive as early as Tuesday night and not exit until Thursday
morning. At this distance there is still a lot of refinement needed
to timing and impacts; however, it is likely that rain will return
to the area during the middle of next week so it was decided to
leave the PoPs that the National Blend provided. This low should
also have some decent cold air advection behind it when it exits
which could allow for a little light snow to mix in at the end. But
as mentioned, there is still a lot of time and model runs to iron
out the details.

DK

&&

.AVIATION /18Z TAFS THROUGH 00Z SATURDAY/...
Issued at 1218 PM CDT Thu Mar 13 2025

The main aviation weather concerns are:

- Period of LLWS tonight into Friday morning, mainly INVOF RFD

- Quickly increasing SSE winds Friday morning and afternoon.
  Gusts over 35 knots probable during the afternoon with a cross
  wind threat on E-W runways.

- Small potential for a little mist/br overnight.

E winds will prevail today around 10 knots. Winds will turn more
southeasterly this evening and overnight. A LLJ will intensify
tonight, particularly over RFD which will lead to a period of
LLWS as winds increase to near 40 knots at 1 kft agl. Have left
this mention out of the Chicago-area terminals where the LLJ
will be a bit weaker.

Winds will then quickly increase through Friday morning and
especially during the afternoon. Gusts above 20 knots will
likely begin towards 14-15z and increase from there. Occasional
gusts towards 40 knots appear possible after about 20z, and
particularly after 21-22z.

A line or several clusters of thunderstorms will impact the TAF
sites Friday night. The most likely timeframe will be in the
02-06z period at RFD, and 03-07z at the Chicago-area sites. Some
storms may be severe with a threat for wind gusts over 50 knots
(severe threat will not encompass the entire time window
mentioned above).

Carlaw

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Wind Advisory from noon Friday to 1 AM CDT Saturday for ILZ003-
     ILZ004-ILZ005-ILZ008-ILZ010-ILZ011-ILZ012-ILZ019-ILZ020-
     ILZ021-ILZ032.

     Fire Weather Watch from Friday afternoon through Friday
     evening for ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
     ILZ023-ILZ032-ILZ033-ILZ039.

     High Wind Watch from Saturday morning through Saturday
     afternoon for ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-
     ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.

     Wind Advisory from 4 PM Friday to 1 AM CDT Saturday for ILZ006-
     ILZ013-ILZ023-ILZ033-ILZ039-ILZ103-ILZ104-ILZ105-ILZ106-
     ILZ107-ILZ108.

IN...Fire Weather Watch from Friday afternoon through Friday
     evening for INZ001-INZ002-INZ010-INZ011-INZ019.

     High Wind Watch from Saturday morning through Saturday
     afternoon for INZ001-INZ002.

     Wind Advisory from 4 PM CDT /5 PM EDT/ Friday to 1 AM CDT /2
     AM EDT/ Saturday for INZ001-INZ002-INZ010-INZ011-INZ019.

LM...Small Craft Advisory from 10 AM to 5 PM CDT Friday for the IL
     and IN nearshore waters.

     Gale Watch from Friday afternoon through Saturday morning for
     the IL and IN nearshore waters.

&&

$$

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