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LCZ460 Lake St Clair- 950 Pm Est Wed Nov 29 2023
Rest of tonight..Southwest winds 15 to 20 knots diminishing to 10 to 15 knots after midnight. Mostly clear. Waves 1 to 3 feet.
Thursday..Southwest winds 15 to 20 knots. Mostly Sunny. Waves 1 to 3 feet.
Thursday night..Southwest winds 15 to 20 knots becoming west 10 to 15 knots in the late evening and early morning...then becoming northwest 5 to 10 knots after midnight. Partly cloudy in the evening...then cloudy with a chance of light rain after midnight. Waves 2 feet or less.
Friday..Northeast winds 5 to 10 knots becoming southeast 10 to 15 knots in the late morning and early afternoon...then becoming east 5 to 10 knots early in the afternoon. Rain. Waves 2 feet or less.
Friday night..Northeast winds 10 to 15 knots diminishing to 5 to 10 knots in the late evening and early morning...then increasing to 10 to 15 knots after midnight. Cloudy. Light rain in the evening...then light rain likely after midnight. Waves 2 feet or less.
Saturday..Northeast winds 10 to 15 knots diminishing to 5 to 10 knots in the afternoon and evening. Mostly cloudy. Waves 2 feet or less.
Sunday..Southwest winds 5 to 10 knots. Mostly cloudy with a chance of light showers. Waves 2 feet or less.
Monday..Northwest winds 5 to 10 knots. Mostly cloudy with a chance of light showers. Waves 2 feet or less.

LCZ400
No data

FXUS63 KDTX 301138 AFDDTX

Area Forecast Discussion National Weather Service Detroit/Pontiac MI 638 AM EST Thu Nov 30 2023


AVIATION

A warmer and drier low level environment will exist throughout southeast Michigan today as winds increase from the southwest. This ensures clear skies aside from some thicker cirrus at times. Modest early day winds under greater stability will turn gusty this afternoon as daytime mixing strengthens. This will support frequent gusts over 20 knots through the early evening period. Low level moisture will increase tonight as a frontal boundary eases into the region. This will bring low end VFR to MVFR ceilings with a chance of light rain development during the overnight period. Winds becoming northeasterly in the wake of the front. A more significant surge of moisture then arrives Friday morning associated with an approaching low pressure system. This will bring widespread precipitation Friday in form of mainly rain across Detroit, with a rain/snow mix to snow at PTK and all snow at FNT/MBS on Friday.

For DTW...Lower cloud will increase in coverage tonight and persist into Friday as widespread precipitation arrives. At this time, conditions appear warm enough to support mostly rain, with simply a very low chance for snow mix in Friday morning.

DTW THRESHOLD PROBABILITIES

* High in ceilings aob 5000 feet Thursday night and Friday morning.

* High in ptype as all rain Thursday night; Medium for just rain Friday.

PREV DISCUSSION
Issued at 417 AM EST Thu Nov 30 2023

DISCUSSION...

Low-level warm air advection will persist through the day under generally zonal flow in the mid-levels. Clear skies this morning (outside of the northern Tri-Cities where low-level stratus has developed) will be overtaken by an expansive mid-level cloud deck later today, but temperature highs will peak into the mid to upper 40s, pushing to 50 near the MI/OH border. Shallow mixing depths to 2kft will pull down some stronger winds aloft, resulting in breezy southwest flow with gusts ranging between 25 to 30 mph during daylight hours.

Attention will then turn to the shortwave that is now located just south of the Four Corners area, which will path just northwest of Ark-La-Tex today where it will then redirect towards the Ohio Valley River through tomorrow morning. A surface low pressure system will develop in response to the wave over Texas and will trail the wave into the Ohio Valley. Deep layer system relative isentropic ascent will commence in anticipation of the arrival of the shortwave which will bring widespread precipitation to most of not all of SE MI starting early tomorrow morning. pva will increase leading into the afternoon under the flank of a 130 knot jet streak which will place SE MI under the favorable cyclonically sheared portion of the jet.
The precipitation shield will expand across all of SE MI leading into the early afternoon hours as a result.

P-type continues to be the major challenge with this forecast package, particularly just north of where a cold front stalls. A shallow cold front that is expected to stall out somewhere around Port Huron southwest into Ann Arbor once southwest flow kicks in from the arriving wave, offsetting the advancement. Temperatures quickly cool near or to the freezing level behind this front, prior to the arrival of precipitation. So at this time there is pretty decent convergence that south of front will support an all rain solution through the event. A rain/snow mix to all snow is then increasingly likely north through roughly the I-69 or just north of the corridor. A very brief period of sleet may be possible in this region as the shallow cold front undercuts very subtle warm air just above the 0C isotherm, but the onset of precipitation is expected to cool the elevated layer of warmer air to below freezing. There is no major indication of a strong push of warm air filling in aloft above this shallow layer of cold air, thus the threat for freezing rain as the initial p-type is extremely low. All snow is likely north of the I-69 corridor.

Surface temperatures are expected to be at or will rise above freezing and ground temperatures from today's milder highs will be an inhibiting favor for accumulation totals where snow is observed.
The caveat to watch will be for any banding potential that can dynamically cool the column and offset surface warming which can result in accumulation on both grassy surfaces and untreated roadways. The outgoing forecast will advertise snowfall totals ranging between 1-3 inches generally between M59 up into the Tri- Cities and Thumb by tomorrow night, acknowledging the potential for a period of moderate snowfall rates. Highly localized totals up to 4 inches are possible if this narrow corridor of banding sets up. As of now this would be most favored north of I-69 where the thermal profile is more favorable, but is certainly a low-end possibility down into the M59 corridor. Snow ratios are expected to be wet to normal between 8:1 to 10:1 snow to liquid ratio. Expect additional tweaks to p-type and snowfall potential leading up to this event given the likely narrow delineation between the rain/snow line. At this time, wanted to put more emphasis on the potential for accumulating snow.

Warm air will draw north late tomorrow night once this initial wave exits. A secondary wave and aforementioned trailing low pressure system will then bring another round of precipitation through Saturday morning. With the warmer air in place, snow chances will likely stay confined to more the Tri-Cities to northern Thumb area.
Some additional snow accumulation will be possible with this wave but again will be contingent on where exactly the rain/snow line sets up. Additional chances for precipitation moves in Sunday as shortwaves start to eject into the Midwest within a longwave trough.

MARINE...

Southwest winds have decreased slightly earlier this morning as a more mild airmass moves in. These winds remain elevated enough across southern Lake Huron to maintain Small Craft Advisory conditions across Saginaw bay to Harbor Beach this morning. Winds hold generally less than 25 knots through most of this morning before another quick passing low pressure system moving across Ontario into Quebec sends a cold front through the central Great Lakes. Wind gusts increase to around 30 knots with this front across central and southern Lake Huron with Small Craft Advisory conditions developing for the remaining Thumb nearshore zones by early this afternoon. Winds will begin to shift from the southwest Thursday afternoon to east-northeast by Friday morning as a low pressure system moves into the Ohio River Valley Friday and then into the southern Great Lakes by Saturday morning bringing rain and snow showers Friday and Friday night. Winds will again bring building waves to the nearshore zones of the Thumb for Friday night into Saturday morning. The active weather pattern will continue into the weekend and a trough moves across the Midwest and Great Lakes region.

HYDROLOGY...

Widespread precipitation is expected to encompass all of SE MI early tomorrow morning into tomorrow night. There will be a rain/snow line that sets up roughly around Port Huron to Adrian, but some minor adjustments to where this line sets up will be possible leading into this event. For locations that receive all rain, accumulation totals between a half-inch to three-quarters of an inch are likely through Friday night. An additional low pressure system then enters early Saturday morning, which will be capable of producing an additional one to two-tenths of liquid accumulation. No flooding concerns are expected at this time.

DTX WATCHES/WARNINGS/ADVISORIES
MI...None.
Lake Huron...Small Craft Advisory until 9 PM EST this evening for LHZ421-422-441.

Small Craft Advisory from noon today to 7 PM EST this evening for LHZ442-443.

Lake St Clair...None.
Michigan waters of Lake Erie...None.

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