Expert Forecast Opinion

353
FXUS63 KDTX 231635
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1235 PM EDT Wed Apr 23 2025

.KEY MESSAGES...

- Much warmer over most of the area today through Friday.

- Low chances for widely scattered showers and thunderstorms this
afternoon into the first half of the night.

- Wider spread showers with embedded thunderstorms likely Friday
afternoon through Friday night as low pressure lifts through the
Great Lakes.

- Dry and seasonable this weekend as high pressure drifts over.

&&

.AVIATION...

A pair of mid level short waves upstream will track across Se Mi
this afternoon. Despite limited moisture, steep mid level lapse
rates will support a chance of showers with these features. The
better chances at the terminals will be focused between 20Z and
23Z. Subtle moisture return into Se Mi will result in weak surface
based instability this afternoon. Of note is the steep mid level
lapse rates which sustain weak to possibly moderate instability
aloft. For this reason, a prob30 group will be maintained in all the
TAFs for a chance of thunderstorms late this afternoon. Ceilings
within any evolving convection is expected to be VFR given the low
level dry air.

For DTW...There is generally a 20 to 30% chance of convective
development across the airspace between 20Z and 00Z. The large
scale forcing and available instability does not support a
widespread area of thunderstorms, rather scattered to isolated but
possibly embedded within a cluster of showers.

.DTW THRESHOLD PROBABILITIES...

* Low for ceiling at or below 5000 feet today.

* Low for thunderstorms late this afternoon and evening.

&&

.PREV DISCUSSION...
Issued at 335 AM EDT Wed Apr 23 2025

DISCUSSION...

Near zonal upper pattern continues for the midweek period allowing a
series of diffuse, dumpy shortwaves to slide over the Great
Lakes/lower MI. These disturbances aid in both lifting a weak warm
frontal boundary north towards central lower MI today as well as
advecting periodic waves of mid-level moisture into the state
supporting widely scattered showers and storms (as seen early this
morning). Overall PoPs remain fairly broad-brushed at 20-30% in
running forecast as weaker forcing combined with sensitivity to
frontal positioning and uncertainty to what degree remnant pieces of
upstream convection survive the local drier low level airmass all
lend to a low predictability, nebulous rain coverage. A break in
rain chances is likely by mid morning through early afternoon as the
first wave kicks east of the region. These chances then return late
afternoon-evening as a second wave (currently generating convection
over Iowa) reaches the western Great Lakes. Said convective remnants
reach SE MI between ~18-22Z however the resident low level dry
airmass works to weaken activity likely only resulting in spotty
showers/storms. Additional scattered convection tied to a surge in
theta-e advection then pushes in from the western Great Lakes
between ~00-06Z with best coverage north of M-59- owing to closer
proximity to the PV anomaly tracking over central lower MI. In both
windows, lapse rates hover around 6.5-7 C/km with MLCAPE`s sitting
at several hundred J/kg supporting the chances for some embedded
elevated thunderstorms within wider showers. 0-6km shear around
35kts will offer a low, but non-zero, shot for an isolated organized
storm which would be capable of generating hail.

Weak mid-level height rises attempt to build over southern lower MI
Thursday suppressing/greatly limiting any precip from shortwaves
still traversing over northern lower MI. The majority of the area is
expected to stay dry as a result, though there is a potential
exception. There is signal among some high-res (and coarser models
like the 00Z RGEM) for a backdoor cold front-lake breeze hybrid,
driven by weak surface high pressure over northern Lake Huron, to
drop across the northern half of the CWA, down to roughly the I-69
corridor. Solutions are divided on the strength of this low level
forcing to generate pop-up (thunder)showers so for now have only
inserted a base slight chance (15%) PoP to highlight. Deeper layer
south to southwest flow below 500mb maintains warm advection into
the area increasing 850mb temps to 10-11C and supporting highs
around 80 Thursday for areas south of I-69. For areas north, it
depends highly on the aforementioned backdoor cold front which would
create a decent north-south temperature gradient with highs in the
mid to upper 70s near I-69 and only 60s in the Thumb.

Large shortwave ejects out of the southern Plains late Thursday and
lifts northeast over the Great Lakes for Friday. Rain looks to
arrive by late morning-early afternoon as widespread showers work
across the area through Friday night. Scattered embedded
thunderstorms also likely, mainly in the afternoon-evening
timeframe, as a few hundred J/kg of MLCAPE develop with peak diurnal
heating. Flatter mid-upper wave decreases the degree to which Gulf
moisture is able to get advected this far north with the core
holding to our south over the Ohio Valley. That said PW values still
increase over 1", well within the 90th percentile for the daily
climo, supporting for heavier downpours and a soaking rain with QPF
looking to fall generally between 0.3-0.6" (some locally higher
amounts possible given t-storm chances). Broad northern Plains high
pressure builds in by early Saturday morning ending further rain
chances with dry conditions holding through the weekend as it drifts
overhead.

MARINE...

Light winds continue through the midweek period under the guise of
higher pressure and a weaker pressure gradient. Any localized higher
wind speeds will be found across northern Lake Huron with the
southeast flow, where gusts around 20 knots will be possible this
afternoon and evening. Otherwise, there will be the chance for
showers or an isolated thunderstorm centered over Lake Erie into
Lake St. Clair today, with additional low end chances extending into
Lake Huron late tonight into tomorrow morning. The better chances
for more widespread active weather and elevated winds enter Friday
as the next low pressure system arrives over the state.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

AVIATION.....SC
DISCUSSION...KDK
MARINE.......AM


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