415 FXUS63 KDTX 091722 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 122 PM EDT Tue Oct 9 2018 .AVIATION... CU field popping up across the area as afternoon instability continues to rise. Hires models still indicate any shower or thunderstorm coverage to be fairly widespread thus will hold onto the vicinity mention this afternoon. Best chance of precipitation will be across MBS. VFR then through the overnight with only high clouds to speak of. CIGS will lower tomorrow as cloud field expands ahead of an approaching cold front. Winds will remain southerly through the taf period. For DTW...Hires models continue to suggest the best window of opportunity for convection to impact metro is between 20Z and 23Z, with the chances a little higher just to the north of metro (closer to PTK and points north). .DTW THRESHOLD PROBABILITIES... * Moderate in ceilings at or below 5000 ft late this afternoon and evening. * Moderate in thunderstorms within the Detroit area late this afternoon and early this evening. && .PREV DISCUSSION... Issued at 335 AM EDT Tue Oct 9 2018 DISCUSSION... NEAR TERM / TODAY THROUGH TONIGHT As of 335 AM EDT...Subtropical airmass now firmly entrenched across southeast Michigan, with anomalous moisture and temperatures in place on the western flank of strong upper-level ridging (596 dam 500 hPa heights) parked off the Mid-Atlantic coast. A muggy night continues, with temperatures currently around 70 across most areas and lows only expected to bottom out in the mid and upper 60s - near record high minimums for the date. Subsequent dewpoints are well into the 60s and will actually rise further closer to 70 this afternoon as low-level moisture is continuously pumped into the region under southwest flow. For the remainder of tonight, main weather concern will be the potential for patchy, locally dense fog development towards sunrise. Winds have largely stayed up most of the night, so full decoupling has yet to take effect, so more widespread dense fog concerns should generally be minimalized. Very warm and humid day today, the warmest in this current stretch. Despite increasing boundary layer cu with daytime heating, enough sunshine coupled with 850/925 hPa temps around 16 C/20+C respectively will yield high temperatures well into the low and mid 80s - near record highs. A limiting factor to even warmer temperatures will be the threat for isolated to widely scattered showers and thunderstorms this afternoon and evening, primarily focused along and northwest of the Irish Hills towards the Tri- Cities. Hi-res guidance has been increasingly bullish with coverage this afternoon, and with 1000-2000 J/kg of MLCAPE available aided by an embedded shortwave rotating through the southwesterly flow (currently near the Tennessee Valley), cannot argue this trend and have bumped up PoPs to high chance in the areas mentioned above. Still, not out of the question for some upper 80s readings closer to the Ohio border where the most sunshine is expected. Lingering convection shifts north into northern lower Michigan as the evening progresses with another very mild night in store. Low temperatures will flirt with record high minimums again only falling into the mid and upper 60s. For more on potential record temperatures, see the Climate section below. SHORT TERM / WEDNESDAY THROUGH THURSDAY NIGHT Active stretch of weather still expected late Wednesday into Wednesday night as a strong cold front sweeps across the region. This cold front will be in association with deepening low pressure ejecting out of the central Plains towards the northern Great Lakes. Model guidance still appears to be on a slightly slower solution, although is honing in on an 18z-06z timeframe for the best shot at numerous showers and thunderstorms accompanying the front. Modest instability will develop during the day Wednesday as the region remains in the subtropical airmass with temperatures warming to around 80. A tempering effect will be poor midlevel lapse rates, but strong dynamic forcing will likely aid in prefrontal trough development during the afternoon, with current indications that broken convection that fires up along this boundary will mainly be to the west in central lower Michigan. The Storm Prediction Center has now introduced a Marginal Risk for severe weather just west of the immediate region, as the wind field ramps up and 0-6 km bulk shear increases to 40-50 knots. Damaging wind gusts will be the primary threat as a possible squall line develops and moves east. The question will be whether the dynamic forcing will be strong enough to offset the lack of favorable instability as the line of convection moves east and likely impacts southeast Michigan during the evening and early overnight period. Will continue to monitor closely, but at the very least numerous showers and thunderstorms are expected late Wednesday into Wednesday night with the potential for gusty winds. The front will quickly exit east by 12z Thursday, with strong cold air advection in its wake as 850 hPa temps plummet to under 0 C by 06z Friday. Dewpoints will also crater significantly into the 30s by Thursday evening. The result will be a full force return to Fall with cool conditions as highs Thursday only reach the mid 50s to lower 60s. The strong cold air advection will also lead to gusty west/northwesterly winds of 25-30 mph. Increasingly dry air from building northern Plains high pressure will allow for clearing skies throughout the course of the day. Patchy frost will be possible Thursday night as low temperatures plummet into the upper 30s for most areas. LONG TERM / FRIDAY THROUGH MONDAY High pressure will remain in place over the region Friday and Saturday with dry weather expected, although there could be increased cloud cover with more of a moisture release off the lakes. High temperatures will only reach the 50s both days, with lows Friday night being the coldest of the Fall season so far, with mid 30s likely leading to areas of frost. Southern stream energy ejecting out of the Plains Sunday will attempt to develop weak low pressure that will track over the region bringing a period of prolonged light to moderate rain lingering into Monday. MARINE... South winds on the order of 10 to 15 knots will persist through the day. The exception will be across far northern Lake Huron, north of Presque Isle Light, where a front will settle south from eastern Upper Mi this afternoon, leading to a backing of the winds to the northeast. The southerly gradient will then increase tonight into Wednesday night ahead of an approaching cold front. Despite the stable over-lake profile, south wind gusts may approach 30 knots across the open waters of Lake Huron Wednesday evening. The cold front will advance across the region Wednesday night, leading to a veering of the winds to the west by Thursday morning. Post frontal cold air advection will support strengthening winds, likely leading to hazardous small craft conditions. There is a low probability that gusts across the open waters of Lake Huron will reach gale force on Thursday. HYDROLOGY... More widespread showers and thunderstorms are expected late Wednesday afternoon into Wednesday night ahead of a cold front. Total rainfall amounts between a quarter of an inch and an inch appear likely. Locally higher amounts are possible, conditional upon the extent of thunderstorm activity. The lack of more widespread rainfall for a couple days prior to this frontal passage will allow river levels to continue to drop. So forecast rain amounts with this next system to not suggest river flooding concerns. CLIMATE... Here are the record high temperatures for Tuesday October 9th: Tuesday, October 9th: High Temperature... Detroit 86 (set in 1949) Flint 85 (set in 1939) Saginaw/Tri-Cities 82 (set in 1949) Here are the record high minimum temperatures for Tuesday October 9th: Tuesday, October 9th: High Minimum Temperature... Detroit 66 (set in 1879) Flint 62 (set in 1949) Saginaw/Tri-Cities 62 (set in 1949) && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....DRK DISCUSSION...IRL MARINE.......SC HYDROLOGY....SC CLIMATE......IRL You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.