158 FXUS63 KDTX 132311 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 711 PM EDT Mon Apr 13 2020 .AVIATION... An ongoing push of colder air this evening should sustain enough of a mixed layer to support a continuation of gusty winds, with speeds and gusts perhaps dropping off a touch with the easing of daytime heating. The diurnal cu field overhead has a large diurnal component. So there is the expectation that the onset of nocturnal cooling this evening will support a clearing trend. This will eventually offer enough cooling to allow some boundary layer decoupling. This in turn will support a more pronounced drop in sfc wind speeds/gusts, likely late in the evening or early overnight. For DTW...The sustained mixing this evening will maintain a nearly due west wind direction. The drop in wind speeds is expected in the 03Z to 04Z time frame. A backing of the winds toward the southwest is then expected overnight. DTW THRESHOLD PROBABILITIES... * High for cigs aob 5kft this afternoon, low this evening, Medium tomorrow. * High for exceeding westerly crosswind thresholds into early evening. && .PREV DISCUSSION... Issued at 333 PM EDT Mon Apr 13 2020 DISCUSSION... Southeast Michigan now firmly within the grip of strong low level cold air advection, the process manifesting along the lead edge of larger scale height falls underway across the northern plains. The strong kinematic response derived within this height fall gradient and the attendant deepening surface low now ejecting toward western Quebec maintaining a solid 20-25kt westerly gradient locally. The ongoing advective process combined with modest diurnal mixing into this elevated wind field contributing to gusty conditions - reaching in excess of 45 mph at times. This profile will receive a boost this evening, as mixing depth briefly climbs in response to a secondary period of 850-700 mb cold air advection. Given the existing wind field residing in this layer, there remains a high likelihood for gusts of 35 to 45 mph to continue well into the evening. Recent model evidence suggests this gust magnitude may linger just beyond the initial advisory expiration window of 00z, so will nudge the end time back to 11 pm. A brief increase in moisture depth with an accompanying steepening of lapse rates could offer a passing light snow shower or flurry across the Saginaw valley and northern thumb overnight, any activity lacking in intensity or duration. Lows tonight dipping just below freezing. Sprawling lower height anomaly will gradually descend across the great lakes through the mid week period. This pattern will solidify a stretch of well below normal temperatures, as 850 mb readings reside just shy of record levels for mid April. Highs arriving in the low to mid 40s most locations - or a solid 10 to 15 degrees below average. A standard increase in diurnal stratocumulus likely each day within the background of mid level cyclonic flow and steepening lapse rates. The increase in boundary layer depth will also offer a period of late day gusty conditions - particularly Tuesday - peak gusts capped near 30 mph given projected wind magnitude and mixing depth. Precipitation potential through the Thursday period remains nebulous, defined by a clear lack of meaningful forcing or moisture quality. Any opportunity therefore quite limited, perhaps focused on the passage of a weak trough timed coincident with a greater lapse rate environment provided during peak heating. Defined precipitation chances during this time remain appropriately muted. Southeast Michigan will likely reside on the northern periphery of a west to east expanding axis of mid level warm air advection late Thursday night into Friday. Governing dynamics still a good 36-48 hours away from appropriate sampling, meaning plenty of room for additional latitudinal movement in the resulting swath of snow. MARINE... Strengthening low pressure system, now centered over the Ontario/Quebec border, will continue to support a strong pressure gradient across the Great Lakes. This will allow Gales (and low-end Storm force gusts across northern Lake Huron) to continue through the late afternoon and evening hours. The low pressure will quickly travel northeast well into Quebec tonight which will weaken the pressure gradient and allow gusts to diminish to sub-gales throughout Tuesday morning. A ridge of high pressure will fill in across the Ohio Valley on Tuesday which will maintain a modest pressure gradient across the state, allowing gusts around 25 knots to hold on throughout Tuesday afternoon. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...Wind Advisory until 11 PM EDT this evening for MIZ047>049-053>055- 060>063-068>070-075-076-082-083. Lakeshore Flood Warning until 4 AM EDT Tuesday for MIZ049-054-063. Lake Huron...Gale Warning until 4 AM EDT Tuesday for LHZ363-421-422-441>443- 462>464. Storm Warning until midnight EDT tonight for LHZ361-362. Lake St Clair...Gale Warning until 10 PM EDT this evening for LCZ460. Michigan waters of Lake Erie...Low Water Advisory until 4 AM EDT Tuesday for LEZ444. Gale Warning until 10 PM EDT this evening for LEZ444. && $$ AVIATION.....SC DISCUSSION...MR MARINE.......AM You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.