326 FXUS63 KDTX 101942 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 342 PM EDT Wed Oct 10 2018 .DISCUSSION... A subtropical airmass continues to hold in place across Michigan as a surface low pressure system and a sharp, negatively-tilted upper- level shortwave pushes northeast across the Midwest. Copious amounts of moisture combined with the surface low and decent upper-level dynamics will be the main source of rainfall and thunderstorms this afternoon and evening. Near-record to record breaking moisture content for October (12Z DTX sounding at 1.33 in (record 1.36 in) and 00Z model guidance near 2.00 in suggests periods of heavy rainfall will be possible with the afternoon and early evening precipitation. In terms of location... Flint up to the Tri-Cities area will have the best chance to see the heavier rainfall and higher rainfall amounts as the axis of greatest moisture content sets up across Central Michigan. Rainfall amounts will widely vary between .10 - .5 inches across the CWA, with locally higher amounts expected over the the Flint to Tri-Cities area, tied to the moisture axis. Lack of diurnal heating due to expansive cloud cover will hold MLCAPEs between 100 - 200 J/kg through daylight hours as mid-level lapse rates remain sub par. Lack of instability will continue to limit severe weather threat despite bulk shear values ranging between 40 - 50 knots. Precipitation loading from towering thunderstorms may help bring down stronger winds aloft to the surface up to 40-50 mph, however, again with the modest lapse rates, saturated sounding profile and deep warm cloud layer, the wind threat will remain very low. Otherwise, westerly flow behind the low will drag a strong cold front across the state throughout the early morning hours Thursday, which will significantly diminish rain chances as very dry Canadian air aloft moves in across the state. CAA will increase boundary layer mixing overnight and for the bulk of Thursday and will bring gusts between 20 - 30 mph, isolated 35 mph. Did opt to carry on the chance for drizzle to light rain showers Thursday morning into early afternoon as as cool westerly flow will bring the chance for lake effect showers that could each east into the CWA. A thermal trough and higher pressure will set up across the region late Thursday and will cap temperatures into the 50s for a daytime high. The thermal trough will remain in place for the bulk of the extended period and will again cap temperatures in the upper-40s to lower 50s for a high on Friday. Slight chance to see rain late Friday into early Saturday, ahead of high pressure, as a PV anomaly couped with left exit dynamics from a jet streak centered across the Ohio Valley provides some upper-level forcing. High pressure will move across the Ohio Valley on Saturday, allowing plenty of cool Canadian air to settle over the region with dry conditions expected. 850mb temps in the negative single digits will translate to highs in the low 50s. Subtle upper ridging will remain in place through Sunday as the surface high moves to the Mid- Atlantic, which should help to keep SE Michigan dry for another day. Southerly return flow on the back side of the high will allow for some recovery in temperatures, with highs in the mid 50s for Sunday. Rain chances increase late Sunday into Monday as a shortwave pivots through the northern Great Lakes and pushes a cold front through. The work week will start chilly, with lows in the 30s and highs only in the mid to upper 40s. The coolest morning in the extended forecast looks to be Tuesday morning, with the potential for lows to dip below the freezing mark. A trough will dip through the Great Lakes during the midweek and bring another chance for precipitation. && .MARINE... Lengthy period of enhanced winds across the lakes as a low pressure system tracks through the northern Great Lakes pulling a cold front through this evening. Steady southerly winds around 10 to 20 knots will continue up until the frontal passage around midnight. At that point winds will veer to the southwest while increasing to near 30 knots. There remains a window of time along and behind the front where cold air advection will cause winds to strengthen to low end gales across central Lake Huron. The current gale watch will be upgraded to a warning for this portion of the lake, with small craft advisories for the remainder of the nearshore waters. As cold air advection continues on Thursday gusty conditions will remain across the lake with gusts topping out around 30 knots. A weakening of the gradient will then lead to decreasing winds and waves late Friday into Saturday. && .PREV DISCUSSION... Issued at 144 PM EDT Wed Oct 10 2018 AVIATION... A low pressure system will track through northern Michigan this evening will pull a cold front across the terminals this evening. Some scattered showers will begin this afternoon with increasing chances of precipitation just ahead of the front. This looks to be mainly a shower event but still cannot rule out some thunderstorms embedded in the line of showers along the front. CIGS will lower to Solid MVFR with some potential for brief IFR with this activity. Timing of the best chance for thunder remains in the 23-05Z window from west to east. Winds will become gusty from the west behind the front with gusts near or above 25 knots Thursdays. Stratus will look to hold through most of the day Thursday as low VFR or possibly MVFR. For DTW...The highest probabilities for thunderstorms to impact metro Detroit look to be late evening, sometime in the 01Z to 05Z time frame. The cold front will move across metro around 06Z tonight veering winds to the southwest while bringing a notable increase to speeds. DTW THRESHOLD PROBABILITIES... * Low in ceilings at or below 5000 ft this afternoon, increasing to high by evening. * Low in thunderstorms impacting the area this evening. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...Gale Warning from 2 AM to 4 PM EDT Thursday for LHZ363-421-422-441- 462. Small Craft Advisory from 2 AM Thursday to 4 AM EDT Friday for LHZ442-443. Lake St Clair...Small Craft Advisory from 11 AM Thursday to 4 AM EDT Friday for LCZ460. Michigan waters of Lake Erie...Small Craft Advisory from 11 AM Thursday to 4 AM EDT Friday for LEZ444. && $$ DISCUSSION...AM/TF MARINE.......DRK AVIATION.....DRK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.