Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
882 FXUS63 KDTX 140757 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 357 AM EDT Tue May 14 2024 .KEY MESSAGES... - There is a chance of showers across all of southeast Michigan this morning shifting toward the Ohio border this afternoon and tonight. An isolated weak thunderstorm is possible. - Notably cooler temperatures settle into the area today with highs in the upper 50s to lower 60s after highs yesterday in the lower 80s. - High pressure brings dry weather and a gradual temperature rebound Wednesday and Thursday. - The next low pressure system arrives with a chance of showers Thursday night and Friday && .DISCUSSION... Early morning observational trends and model analysis fields indicate the cold front overhead and settling very slowly toward the Ohio border leading up to sunrise. Slightly stronger high pressure reaching down from northern Ontario combined with a slower/farther south pace of mid MS valley low pressure is keeping the front slowly on the move rather than completely stalled across southern Lower Mi. Clusters of showers in progress are embedded in the west to east mid level moisture axis extending north of the surface front up through the Tri Cities and Thumb, and this is expected to continue during the morning. The temperature contrast will become the notable aspect of conditions this afternoon as readings stall in the upper 50s to lower 60s compared to highs in the lower 80s across all of SE Mi yesterday. A shift toward surface based convective potential is confined to along and near the cold front that will be very near the Ohio border by mid afternoon, if not to the south when factoring in the influence of Lake Erie. This will limit the chance of surface based convection to Lenawee and Monroe counties during feeble peak instability from mid afternoon to mid evening. HREF mean surface based CAPE is only a few hundred J/kg after 18Z and almost non- existent by 00Z this evening to go along with an impressively weak wind profile featuring about 10 knots of flow at 500 mb. Scattered afternoon and evening showers is the best way to describe the result, with a rumble of thunder possible. A stray shower then remains possible after midnight off the northern fringe of the low pressure system as it moves slowly along the Ohio valley. Clouds decrease north to south across Lower Mi during Wednesday as surface high pressure builds down farther from northern Ontario. Lingering NE boundary layer cold advection is balanced by breaks of afternoon sunshine across interior locations making guidance highs around 70 within reach. Given the NE wind, locations closer to the shorelines will have much more of a temperature struggle where readings end up stuck in the 50s near Lake Huron. Temperatures then take a step upward Thursday as high pressure retreats into Quebec. The Lake Huron shoreline remains the exception as easterly/onshore wind continues, although on a weaker gradient compared to Wednesday. For the late week and next weekend, extended/global model solutions depict a less amplified long wave upper air pattern compared to recent days/weeks. The relatively zonal flow carries the next short wave system into central Canada during mid week with improved agreement among solutions on Thursday night/Friday arrival timing in the Great Lakes. The quick moving system brings our next chance of showers and thunderstorms until exiting eastward Friday night. Model consensus for the weekend maintains a progressive/zonal configuration favoring mostly dry and mild weather this weekend. && .MARINE... The chance for showers will continue along a stationary front which is currently positioned west-southwest to east-northeast, extending from the basin of southern Lake Michigan into southern Lake Huron. Some rumbles of thunder cannot be ruled out, but with limited instability, mainly rain showers are expected. Shower chances remain possible leading into the early afternoon, but will decrease as high pressure builds into the northern Great Lakes, pushing the frontal boundary south of the state line. Some renewed rain and some thunder chances will build back in mainly across Lake Erie late tonight into Wednesday as a low pressure fills in across the Ohio Valley. This low pressure system will reinforce northeast flow across all of the Great Lakes, building wave heights into Saginaw Bay and across the Lake Huron shoreline. Small Craft Advisories will likely be needed across the Bay and portions of the shorelines given wave heights building to or slightly above the four feet. High pressure will continue to settle in over the Great Lakes on Thursday, relaxing wind speeds and subsequently wave heights. && .PREV DISCUSSION... Issued at 1047 PM EDT Mon May 13 2024 AVIATION... Frontal boundary is now just north of FNT with a narrow corridor of showers in its wake. Overall ceilings hold well above 5.0 kft agl at discussion issuance, but as the front gradually sinks south, increased convergence and moisture pooling work to lower ceilings toward MVFR (potentially lower at FNT and PTK which are nearest to the boundary). Frontal position is well marked by a shift to northeast winds that will hold through the TAF period. The DTW corridor may hold on to VFR ceilings or scattered coverage Tuesday owing to drier low levels and further distance from the front, but confidence is low at the moment given large variations in guidance. Elevated portions of the frontal slope remain active with showers through Tuesday morning mainly along/north of PTK, while a disturbance lifts into the Ohio Valley which will support scattered showers around DTW as well. Improvements to ceilings and a decrease in shower coverage is anticipated Tuesday afternoon-evening. For DTW/D21 Convection...thunderstorm activity has waned with loss of diurnal instability, thus no thunderstorms are expected at the terminal. DTW THRESHOLD PROBABILITIES... * Medium confidence in cigs aob 5000 feet late tonight through Tuesday evening. * Very low confidence in cigs/vsby aob 200 ft and/or 1/2sm 08z-14z Tuesday. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ DISCUSSION...BT MARINE.......AM AVIATION.....MV You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.