298
FXUS63 KDTX 220833
AFDDTX
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
333 AM EST Wed Jan 22 2025
.KEY MESSAGES...
- A Cold Weather Advisory remains in effect until Noon.
- Hazardous wind chill values between -25F to -20F through 9 AM EST.
- Widespread light snow expands over SE MI late tonight through
tomorrow morning. A half-inch, up to two inches of accumulation
expected. Higher totals expected within the Thumb.
- A warming trend, albeit still below normal, begins tomorrow and
continues into early next week.
&&
.DISCUSSION...
The coldest air of the ongoing arctic outbreak now resides across SE
MI, enhanced by efficient radiational cooling under clear skies
coupled with peak nocturnal cooling. All stations across SE MI are
reporting temperatures in the negative single digits. Subtle mixing
in the lowest 1km have sustained lighter winds peaking up to 10-15
mph which have dropped wind chill values to around -20F. With still
a several hours until sunrise, temperatures will be capable of
dropping several more degrees, lowering wind chills to near -25F in
spots. A cold weather advisory remains in effect until 12PM EST
today.
The combination of high pressure expanding into the Appalachia
coupled with an approaching clipper system targeting the upper Great
Lakes will allow a moderate pressure gradient to form over SE MI
under persistent southwest flow which will allow for the more
modified continental US air to start to filter into the region. This
will mark the start for "warmer" temperatures to settle in over the
state, with daytime highs in the teens today increasing into the mid
20s by tomorrow afternoon -- still below normal for this time of
year. Subsidence in the wake of a passing shortwave brings a dry
start through the morning while south-southwest flow holds lake
effect snow showers west and north of the cwa.
A very subtle uptick in moisture will accompany the increasing
temperature trends while low to mid level system relative isentropic
ascent becomes more favorable late tonight into tomorrow morning
once the aforementioned clipper system and attendant shortwave move
across the Great Lakes. The result will be widespread, light snow
that fills in, initially through the Tri-Cities and Thumb. A half-
inch to an inch of accumulation will be likely across the greater
portion of SE MI by the late morning, up to a localized two inches,
most favorable across the Thumb given an earlier start time, longer
resident time, and closer proximity to shortwave. The I-94 corridor
south will be removed from the better forcing, bringing higher
chances to see snow totals closer to a half-inch or less.
Passage of the clipper will drag a cold front across SE MI through
the morning which will steepen lapse rates as a secondary shortwave
passes overhead. Backed flow the northwest under caa coupled with
the above will bring a window for lake effect snow showers in the
afternoon and evening, which has the potential to grind out an
additional dusting of snow accumulation before converting over to
flurries or stopping altogether leading into Friday morning once
lapse rate strength wanes.
Temperatures do get colder in the wake of this cold front with lows
dropping into the single digits Friday morning, wind chills near
zero. Temperatures rise to the 20s under shortwave ridging while
near surface flow backs southwest. This will bring about dry weather
and will lead to a cold start to the weekend with lows again in the
single digits. Zonal mid-level flow through the weekend breaks down
slightly into next week with flow veering to the northwest through
the middle of next week. This will pull in some modified warmer air
derived from the western Provinces, and will likely bring subtle
increases to temperature trends through the early week period, eyeing
temperatures to or above the freezing mark Tues-Weds.
&&
.MARINE...
Surface high pressure building northward out of the Ohio Valley
while an upper level ridge slides over the first half of the day
will lead to quiet weather in terms of snow today. Winds will
continue to be elevated but out of the southwest today so lake
effect will be directed off to the northeast. Winds gusting up to 25
to 30 knots will keep waves active thus will keep freezing spray
possible across Lake Huron. Current freezing spray headlines will
continue through this evening. The next low pressure system tracks
through the northern Great Lakes tonight, pulling a cold front
through on Thursday which will bring chances of more widespread snow
to the area in addition to any lake effect bands still active. With
the coldest of the arctic air off to the east, we`ll remain slightly
below normal with highs in the mid-upper 20s through the weekend.
&&
.PREV DISCUSSION...
Issued at 1043 PM EST Tue Jan 21 2025
AVIATION...
Ongoing backing of the low level winds to the south-southwest has
driven the lake moisture plume out of Se Mi, leaving clear skies
across Se Mi. An approaching upper short wave will result in an
increase in mid and high level clouds toward daybreak. There will be
some degree of lowering cloud bases Wednesday afternoon as the
shortwave advances. Limited upstream low level moisture will keep
cloud bases relatively high (mainly VFR) until some Lake Michigan
moisture comes into play later Wednesday night.
DTW THRESHOLD PROBABILITIES...
* Low in ceilings aob 5000 feet Wednesday. Moderate Wednesday night.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Cold Weather Advisory until noon EST today for MIZ047>049-053>055-
060>063-068>070-075-076-082-083.
Lake Huron...Heavy Freezing Spray Warning until 10 PM EST this evening for
LHZ362-363-462>464.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&
$$
DISCUSSION...AM
MARINE.......DK
AVIATION.....SC
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at www.weather.gov/detroit.
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