Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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425 FXUS63 KDTX 221711 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 1211 PM EST Fri Nov 22 2024 .KEY MESSAGES... - Breezy today with peak gusts around 30mph. Scattered to numerous lake effect rain showers also likely today, mainly for areas east of US-23/I-75. - Dry weather returns for the weekend as weak high pressure builds in. Lingering cloud cover will be difficult to dislodge however. - Another low looking to develop over the region Monday bringing additional rain chances and brief shot at milder air. Below normal temperatures return by Tuesday and midweek. && .AVIATION... Broad low pressure centered near far NE PA maintains influence over the region with northerly flow across Lake Huron directing a plume of low-level moisture into SE MI. MVFR ceilings will continue to be the norm through the period with showers or drizzle mainly over the Thumb but also possible at times at the Metro Detroit sites. Gusty NW surface winds weaken slightly this evening but remain active into tonight and MVFR ceilings remain favored into Saturday morning. Wind direction then shifts more from the WNW by the afternoon with potential for ceilings to lift to VFR mainly after the current TAF period. DTW THRESHOLD PROBABILITIES... * High in ceilings at or below 5000 ft through tonight. * High for precip type being all rain today. && .PREV DISCUSSION... Issued at 327 AM EST Fri Nov 22 2024 DISCUSSION... Broad, closed low upper trough continues to dominate conditions across the Great Lakes/eastern CONUS today as its associated mature surface low retrogrades into central NY. Gradient re-tightens across the area this morning in response resulting in a deep column layer of winds >30kts which will support surface gusts near 30mph for much of the day. Northerly flow off Lake Huron aided by ribbons of vorticity rounding the mid-level circulation into southern MI should lead to a healthy lake effect response focused over the Thumb with spottier chances spilling south into Metro Detroit. Areas to the west of I-75/US-23 likely stay mostly if not entirely dry today given their detachment from lake moisture plumes under NNW wind. Warmer lake waters in the central/southern basin of Lake Huron (low to mid 50s F) modify the low level thermal profiles lifting freezing levels to between 900-850mb and keeping p-types as rain. With the core of thermal troughing now residing to our south and east, temperatures are able to moderate some as highs climb back to around average in the mid 40s. Troughing influence wanes Saturday as low amplitude ridging over the central CONUS attempts to nudge eastward into the central Great Lakes. Weak surface high pressure accompanies said ridge supporting drier conditions with seasonably average temps and lighter winds for the weekend. However as it typical this time of year, sun may still be hard to come by during this timeframe as forecast soundings struggle to scour out remnant low level moisture given weak subsidence and a lack of significant dry air advection (PW values only drop by ~0.2"). Active pattern redevelops to start the new work week as a mid-level shortwave breaks off from a larger Pacific NW trough and tracks into the central Plains Monday. This wave is progged to reach the Great Lakes late Monday into Tuesday as it undergoes amplification, potentially gaining a negative tilt in the more aggressive solutions, spurring surface cyclogensis over the region. How rapid this amplification and subsequent cyclogensis occurs is the main point of uncertainty with slower paces, such as what is in the Euro deterministic/ensemble, resulting in surface low developing on top of the area with the deepening and subsequent heavier precip occuring to our east. Conversely a faster amplification such as the GFS deterministic/ensemble leads to deepening occuring overhead resulting in greater QPF. Regardless of either outcome, the bulk of ensemble members in both families agree low development occurs roughly over central lower MI leading to warm advection into SE MI to keep the p-type as rain with much above average temperatures reaching into the 50s. Strong cold air advection on the backside of the low drops 850mb temps into the mid negative single digits (C) likely supporting some snow being able to mix in with any lingering trailing precip Tuesday. MARINE... The Great Lakes remain under influence of a slow-moving upper low, which will continue to generate scattered lake-enhanced showers through Saturday. The more notable part of this system is a second round of strong northerly wind gusts that will funnel down the major axis of Lake Huron today. A broad 925mb core of 35-40 knot winds develops overhead, which will encounter very efficient momentum transfer especially over southern Lake Huron where water temperatures are around 12 C. Considering time of year, unstable thermal profiles, and long fetch of unobstructed northerly flow, a Gale Warning has been issued for the southern half of Lake Huron and nearshore zones today. The most likely location for gale force gusts up to 35 knots will be along the tip of the Thumb (Caseville to Port Austin) and over southern Lake Huron around mid-day. Winds and waves will subside very gradually on Saturday with mid-level ridging attempting to build in briefly on Sunday. Another low pressure system will be quick to develop over the Plains however to continue the period of unsettled conditions into early next week. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...Small Craft Advisory until 10 PM EST this evening for LHZ422. Gale Warning until 7 PM EST this evening for LHZ421-441>443-462>464. Lake St Clair...Small Craft Advisory until 10 PM EST this evening for LCZ460. Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EST this evening for LEZ444. && $$ AVIATION.....TF DISCUSSION...KDK MARINE.......MV You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.