IWX issues Area Forecast Discussion (AFD) at Jun 5, 6:46 AM EDT493
FXUS63 KIWX 051048 CCA
AFDIWX
Area Forecast Discussion...Correction
National Weather Service Northern Indiana
646 AM EDT Wed Jun 5 2024
.KEY MESSAGES...
- There is a marginal risk of severe thunderstorms from midday
through this evening.
-Damaging wind gusts, heavy rain, and hail are the primary
hazards.
- Warm and humid conditions today give way to cooler than-normal
temperatures for much of the next seven days.
&&
.UPDATE...
Issued at 623 AM EDT Wed Jun 5 2024
Thunderstorms over central and southwest Illinois will be the ones
to watch over the next several hours. These storms are forming ahead
of an approaching cold front. Early-morning activity locally has
diminished and moved northeast, thus leaving an unimpeded atmosphere
for the approaching storms. Surface observations are plenty soupy
this hour with temperatures near 70 and some dew points near 70 as
well. furthermore, plenty of breaks are noted on satellite as well.
Therefore, instability is plentiful this morning and that trend is
expected to continue.
High resolution guidance is picking up on these trends such that a
broken line of storms could get going as far west as the South Bend
area, and as early as about 15z (11am EDT). Forecast soundings in
this area advertise strong-low level lapse rates, confirming the
damaging wind gust threat, while shear continues to be marginal (but
acceptable) near 25 to 30 knots. Overall, the severe weather risk
remains marginal but the area of concern is shifting westward well
outside the I-69 corridor. I've passed along this assessment to the
SPC for consideration.
&&
.DISCUSSION...
Issued at 232 AM EDT Wed Jun 5 2024
A cold front approaching the Mississippi River this morning will
bring a marginal risk of severe thunderstorms in the afternoon and
evening along and east of I-69 (generally speaking). Damaging wind
gusts are the primary concern, followed by heavy rainfall and hail.
The timing of these storms remains about 2pm to 8pm EDT.
Showers and thunderstorms are ongoing over northwest Indiana early
this morning, associated with a MCV lifting in from Illinois, aided
further by a strengthening 850-mb jet. Heavy rainfall and perhaps
strong wind gusts near 40 mph are possible (as reported over
northeast IL). Elsewhere in the forecast area will be untouched by
the time the cold front arrives in the afternoon. Temperatures
rising in the 80s with dew points near 70 degrees will permit
impressive CAPE ahead of the cold front while shear and lapse rates
are lacking (25 knots 0-6km and 6C/KM mid-level, respectively).
Coverage of storms along the cold front varies among model guidance,
likely due to the marginal environment, but guidance favors discrete
cells in our area perhaps congealing into a line across central Ohio.
Drying out for a time early in the night behind the cold front but a
a few showers may arrive later on associated with a screaming, 85-
knot jet at 500mb. Moisture transport from the Pacific is somewhat
poor, navigating significantly poleward atop a towering ridge over
the Four Corners before spilling over the Great Lakes. However, RH
remains elevated in the column through Friday, warranting at least
slight chance POPs at times as various embedded vorticity maximums
rotated around the closed low aloft. Temperature-wise, Friday looks
to be the coolest of the next seven with highs right near 70
following two distinct waves of CAA.
This upper-level low lingers over the (eastern) Great Lakes into at
least the start of next week, if not longer. This complicates the
forecast as models do not handle cut-off lows very well. Overall,
showers at times are probable paired with cooler-than-normal
temperatures for June.
&&
.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 646 AM EDT Wed Jun 5 2024
A trailing pre-frontal outflow has settled into nw IN and central IL
behind a well defined MCV tracking into western MI. Ongoing moisture
advection, and the approach of another convectively aided wave over
western IL, should bring a round of showers/storms mid morning
through early afternoon at KSBN. Remnants of this activity and
growing diurnal instability should also allow for scattered
convection to eventually impact KFWA, best chances 18-21z. Flight
conditions should hover between MVFR and VFR for the bulk of the
morning and early afternoon before a cold front sweeps through late
in the day with quiet/cooler wx to follow into tonight.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
UPDATE...Brown
DISCUSSION...Brown
AVIATION...Steinwedel
Source:
IWX issues Area Forecast Discussion (AFD) at Jun 5, 6:46 AM EDT---------------
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