Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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764 FXUS63 KDTX 081028 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 628 AM EDT Wed May 8 2024 .KEY MESSAGES... - Warm and breezy today. - Much cooler on Thursday with rain expected south of M-59 and a chance north. && .AVIATION... West-southwest low level winds have ushered in drier air in the boundary layer early this morning, which should inhibit pre dawn fog development. Southeast Michigan will lie between a departing low pressure system over the northern Great Lakes a frontal boundary over the Ohio Valley. A region of dry air between these two systems will limit the extent of cloud cover across most of the area today outside of MBS. Westerly gradient flow with a solid region of 20 to 30 knots in a deep daytime mixed layer will result in gusty west winds this afternoon. A cold front will advance inland from Lake Huron late this afternoon and evening. There is general model agreement that the low level moisture will erode with the southward advancement of this late day front. So the main impact with this front will be a wind shift to the NNE. For DTW/D21 Convection...Instability has completely exited the airspace. No thunderstorms are expected today and tonight. DTW THRESHOLD PROBABILITIES... * Low in crosswind thresholds being exceeded this afternoon. && .PREV DISCUSSION... Issued at 245 AM EDT Wed May 8 2024 DISCUSSION... Massive/West-East elongated upper level low/trough centered over the Dakotas early this morning. In fact, 00z Bismark raob indicated a 500 MB height of 537 DAM, which looks like it set the daily min record. As this upper level low weakens today, a big pattern shift will occur for us, as the warm and deep southwest-west flow in place transitions to predominately northwest flow to end the work week into the weekend. Weak surface wind fields early this morning, coupled with last evening`s rainfall, and dew pts in the 50s has lead to a little light fog in spots. Still looks very shallow and should not have a much of impact on max temperatures. Increasing westerly flow today with a north-south gradient in place, as 850 MB temps this afternoon look to be in the mid/upper single number north of I-69, with lower teens toward the southern Michigan border. The I-94 corridor will likely mix to 725 MB, where 2-3 C is forecasted, supportive of highs around 80 degrees/lower 80s, otherwise 70s should work for much of the rest of the CWA. Huron county looks to have more clouds, cooler influence from Saginaw Bay and perhaps a stray shower to keep temps down in the upper 60s/near 70. With the deeper boundary layer mixing expected, inherited wind gusts of 25-30 knots also appears fine. Much cooler air for the entire CWA arrives on Thursday as positive tilted trough axis drops south from Eastern Canada, and low level winds out of the northeast increase off Lake Huron. Highs predominately in the 55-60 degree range expected. It does appear the upper level wave coming out of the Midwest will subsequently be deflected farther south, through the Ohio Valley. 850-700 MB Theta-E ridge axis looks to be straddled along or just south of the southern Michigan border, with moisture quickly diminishing as one heads north, calling into question the rain showers developing for northern areas of the CWA (see 00z regional GEM, NAM, ICON, and UKMET especially). Planning on sharping up the south-north pop gradient significantly. Dry Friday as shortwave ridging builds over the Central Great Lakes, but nthe ext upper level wave/trough embedded within the northwest flow arrives by Saturday morning, supportive of a chance of showers despite limited moisture available, and perhaps an isolated thunderstorm as the showalter index lowers toward zero and several hundreds of MUcape indicated. MARINE... Low pressure tracks near the Straits this morning setting up modest (~15-20kt) westerly flow across the region in its wake. A secondary low develops over the Ohio Valley tonight resulting in local winds shifting to out of the northeast. With a marginally cooler airmass drawn south, peak wind gusts Thursday over the central portion of Lake Huron reach 20-25kts with near 30kts possible over the Saginaw Bay due to funneling down the bay. Small craft advisories may be needed around the Thumb nearshore waters daytime Thursday as waves increase given the wind direction. System vacates by Thursday night bringing lighter winds and ending further shower chances. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....SC DISCUSSION...SF MARINE.......KDK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.