Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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300 FXUS63 KDTX 080645 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 245 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. && .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. && .PREV DISCUSSION... Issued at 1201 AM EDT Wed May 8 2024 AVIATION... Bulk of convection has cleared out of Southeast Michigan late this evening while a wave of subsidence leads to aggressive dissipation of clouds. Wind speeds trend lower for several more hours offering potential for periods of MVFR fog. After evening rainfall moistened the near surface layer, air temperatures should largely cool-down and approach the dewpoint temperatures, thus the current TEMPO. Can`t completely rule out areas of IFR fog given the underachieving gradient wind (and nearby obs), but low confidence exists. Sunny and breezy conditions arrive Wednesday afternoon with gusts in excess of 25 knots. For DTW/D21 Convection... A line of storms crossing Lake Michigan will dissipate before reaching the immediate airspace between 06Z and 08Z. Showers, and perhaps a rumble of thunder, possible early Thursday morning with the next system. DTW THRESHOLD PROBABILITIES... * Low for ceiling at or below 5000 feet this morning. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...SF MARINE.......KDK AVIATION.....KGK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.