838
FXUS63 KDTX 272250
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
650 PM EDT Thu Mar 27 2025

.KEY MESSAGES...

* A warm front lifts into Lower Michigan on Friday, generating
  showers and a few elevated thunderstorms; severe weather is not
  anticipated but heavy downpours will be possible in any
  thunderstorms.

* A sharp gradient in temperatures is expected on Saturday with
  showers along and north of the front during the day.

* Rainfall chances increase over Metro Detroit again Saturday
  evening into Sunday as additional low pressure systems impact the
  area until early next week.

&&

.AVIATION...

A warm front will lift northward into Se Mi on Friday. The elevated
portions of this front will drive an influx of moisture with
increasing chances for light showers during the overnight. Model
soundings and probabilistic guidance support lowering ceilings from
VFR to MVFR in the 06Z to 12Z time frame. The surface front will
inch northward across the terminals Friday afternoon. Low level
moisture convergence in advance of this front will drive ceilings
toward low end MVFR and IFR range late Fri morning into the
afternoon. A little better surge of low level ascent will result in a
band of higher intensity showers lifting from SW to NE across the
area late Fri morning/early Fri afternoon. Weak elevated instability
will offer a low chance of thunderstorms along the sfc warm front
during the afternoon. Given the expected east-northeast flow off
Saginaw Bay, the front is likely to hold south of MBS through Fri
afternoon.

For DTW...Generally only light rain showers are expected overnight.
The higher intensity rain showers are forecast during the 14Z to 20Z
time frame. There is a slight chance (<25%) for an embedded
thunderstorm within these higher intensity showers.

.DTW THRESHOLD PROBABILITIES...

* High in ceilings aob 5000 feet Friday. Low Friday evening.

* Low for an isolated thunderstorm Friday.

&&

.PREV DISCUSSION...
Issued at 337 PM EDT Thu Mar 27 2025

DISCUSSION...

Inflection point of the amplified longwave pattern has migrated
across Lower Michigan today, providing rather benign conditions. The
synoptic ridge encompassing central CONUS has begun to flatten in
response concentrated PV filaments working through the energetic
125+ knot upper-level jet structure which presents well in GOES
water vapor imagery. Expect thickening cloud cover this evening and
overnight as a plume of moisture spills into the Great Lakes from
the eastern Plains. GOES visible shows resultant cloud already
working well into Southwest Lower this afternoon with ASOS/AWOS
ceilometer measuring 6 kft to 8 kft AGL cloud bases. Greater
coverage of clouds spreads across Southeast Michigan with time
tonight, helping to prop up overnight lows above the freezing mark
for most. Afternoon gustiness of 25 mph to 30 mph also drops off
nocturnally as a near-surface inversion arises.

Latest CAMs have trended slightly earlier with shower potential late
tonight as the elevated portion of an approaching warm front lifts
into southern Lower into Friday morning. This affords rising
specific humidities as return flow from Southeast CONUS high
pressure directs a plume of Gulf moisture into the Midwest.
Perturbed embedded mid-level flow leads to more favorable tendency
for ascent. Did introduce Slight Chance (15-24 percent) PoPs for the
06Z to 09Z time-frame, early Friday morning, for Lenawee and Monroe
Counties.

Main FGEN arc activates a more robust precipitation response after
12Z Friday as the warm nose pushes in, backing low-level winds from
westerly to southwesterly. Models depict a notable 850-700 mb ThetaE
surge amidst an increasingly confluent low-level jet. Forecast
soundings depict unimpressive vertical RH profiles, particularly
through the mid-levels, but given the magnitude of ThetaE
convergence in the lower column, should still see some shallow
showers lift northeastward. A secondary period of rain showers (and
perhaps some embedded thunder) will brush the southwest portion of
the County Warning Area Friday afternoon as the surface warm front
straddles an inverted trough axis amidst elevated instability. Given
the drier air aloft and preservation of the 800 mb (6 kft AGL)
capping inversion, not expecting as much afternoon convection, at
least not as widespread. More aggressive/rapid drying arrives Friday
evening and early Friday night. Adjustments made to PoPs with
notable reductions south of I-69. Thermal gradient will from
southwest to northeast will result in cooler readings for The Thumb
where a backdoor cold front clashes with the warm frontal passage.

Much warmer air entrenched across the region Saturday with highs
well above normal (60s for most) as 850 mb temperatures start out in
the upper single digits (positive Celsius). Stalled/washed out warm
front through mid-Michigan gets dislodged by an approaching
trough/low that leads to renewed shower activity north of M-46.
Eventually, the front drops through flipping winds northerly behind
the boundary and in the wake of the low. Unsettled conditions
persist through the weekend and into early next week as a series of
shortwaves transit the Great Lakes, tied to a combination of
northern and southern stream waves. A sharp divide in temperatures
sets up through Sunday as the warmest air (mid-upper 60s) reside
south of M-59. Primary airmass change arrives behind the cold front
associated with a 997 mb surface low. Readings drop back into the
40s with drier conditions favored for the first half of next week.

MARINE...

A cold front continues to drop through the central Great Lakes this
evening setting up colder northwest flow in its wake. Magnitude of
the frontal wind spike decreases the further south the front gets,
due to its detachment from the parent low over northern Ontario,
ranging from 15-25kts over the central/southern Lake Huron to a
negligible increase over the southern lakes. Brief period of high
pressure follows for tonight before a warm front lifts the region
daytime Friday. Front generates scattered showers and isolated
thunderstorms with rain-snow showers over far northern Lake Huron.
Easterly winds increase in advance of said front with strongest
winds over far northern Lake Huron late Friday where favorable fetch
allows for 25-30kt gusts. Frontal boundary stalls near the Straits
before sagging back south daytime Saturday as a surface low tracks
directly over Lake Huron. Another surface low then tracks along this
lingering boundary through the central Great Lakes late Sunday-early
Monday. Result is long duration of unsettled weather through the
weekend including scattered thunderstorms, some of which may be
severe, over the southern Great Lakes Sunday evening. Winds
throughout the weekend expected to generally hold under 25kts
(variable direction given the lows passing overhead) before
increasing to 25-30kts Monday as northwesterly flow redevelops
following the departure of the last surface low.

HYDROLOGY...

A warm front lifts into the Great Lakes on Friday and stalls over
northern Lower Michigan. Moisture streams in from the Gulf elevating
precipitable water values to around 1.25 inches (near the 99th
percentile of sounding climatology). This supports an environment
conducive for several episodes of rainfall Friday through Monday.
Total rainfall amounts will be highly conditional on where heavier
convective downpours arise with any thunderstorm activity. This
affords lower than normal confidence in rainfall amounts and
resultant flooding potential. Should precipitation arrive in
episodic fashion, any flooding that could arise will likely be more
localized.

CLIMATE...

The record high minimum temperatures for Saturday, March 29th:

Detroit: 54 Degrees (Set in 1910)
Flint:   52 Degrees (Set in 1986)
Saginaw: 52 Degrees (Set in 1981)

&&

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

$$

AVIATION.....SC
DISCUSSION...KGK
MARINE.......KDK
HYDROLOGY....KGK/MV
CLIMATE......MV


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