Area Forecast Discussion
Issued by NWS Gaylord, MI
Issued by NWS Gaylord, MI
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630 FXUS63 KAPX 211743 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 143 PM EDT Sat Sep 21 2024 .KEY MESSAGES... - Rain/storms return very late tonight into Sunday night && .UPDATE... Issued at 1144 AM EDT Sat Sep 21 2024 Synopsis: 13z surface/composite analysis shows a strung out 1011mb low over Lake Huron/eastern Upper Michigan along a cold front that extends south into Ohio. A second cold front lies across western Minnesota/eastern Nebraska. Weak short wave trough moving into Lake Huron this morning with a stronger disturbance over Manitoba and the northern High Plains. Bit of a low level thermal trough across the lower Great Lakes with a thermal ridge/low level warm advection spreading into the Midwest. In between the two cold fronts is an area of convection over eastern Minnesota/far northwest Wisconsin. Over northern Michigan at late morning...stratus deck north of M-72 into eastern Upper...with skies mostly sunny south of M-72. 12z APX/GRB raobs showed just a shallow moist layer above the surface and dries out quickly above. But juxtaposition of cold dynamic tropopause temperatures and higher low level theta-e is resulting in some elevated instability across northern Michigan (12z APX MUCAPE around 800J/kg with minimal CINH). Forecast Update: Stratus will continue to mix into an Sc deck this morning over the land areas...may eventually mix out completely later this afternoon. Lake breezes should abound this afternoon... will watch a little more closely along the Lake Huron counties where there is some lingering instability as mentioned above. Another afternoon of temperatures well above normal...with normal highs now ranging from 66 to 70 degrees afternoon highs expected to range from the upper 70s to mid 80s. Don`t think any record highs will go down at this point even with most records in the mid to upper 80s now but it could be close in spots. && .SHORT TERM /THROUGH TONIGHT/... Issued at 341 AM EDT Sat Sep 21 2024 Pattern/synopsis: A slow-moving cold front bisects northern MI from nw to se. Precip has m moved off to the east, associated with a mid-level trof and better moisture/instability. Drier mid-level air has ended precip, but contributed to fog. The front progresses eastward out of the area this morning, and high pressure will poke northward into lower MI by midday. Forecast: Fog is the most immediate concern. Fog has been dense in spots. Satellite imagery suggests the most substantial fog in in the tip of the mitt counties, and in the far se. Was thinking a couple hours that a fog advisory was likely...but for now, the number of surface ob sites indicating dense fog is limited. (At this moment: PLN/MGN/MBL/Y31). That`s fewer than two hours ago (for example, CAD-HTL have improved). Would think things would still tend to worsen thru sunrise (though the pressure gradient is a touch tighter in nw lower MI vs southern lower). For now, just have an SPS out mentioning fog. Will continue to monitor satellite and surface ob trends. Satellite does hint at much of our fog/stratus being on the shallow side. The exception is in parts of eastern upper MI (including just w of our area at ISQ-ERY). Expect fog/low clouds to mix out somewhat faster in the south than in the north. Places south of M-32 should be comfortably mostly sunny by midday, but it may take thru early or even mid afternoon to the north. Building 500mb shortwave ridging will sharply limit Cape, and diurnal convection is not expected here. Max temps mid 70s north to mid 80s far se. Tonight, the upper ridge gets shunted east across Lk Huron, with weak energy lifting ene-ward into the central lakes. A quick shot of return flow gets going tonight, in advance of another cold front approaching western sections by Sunday morning. Warm/moist advection in low levels, and some troffing aloft, will contribute to marginal destabilization. This instability will be very marginal here (MuCape values struggling to reach triple digits), but more substantial just w of Lake MI (where MuCape values reach high triple-digits. Deep convection should initiate later today in the far upper MS Valley. Stronger/more organized convection should tend to turn se-ward with time tonight, as storms search for better instability/inflow. But some pre-frontal convection will fight its way into the region tonight, eventually overcoming the drier air initially in place. There could be a stray shower in the far west by midnight, but better pops arrive later. By late overnight, chancy pops are found nw of a line from CAD to Onaway, including the eastern UP. The highest pops will be in western Chip/Mack Cos. A rumble of thunder is possible, but severe wx is not expected, given the lack of significant instability. Min temps mid 50s to near 60f. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Issued at 341 AM EDT Sat Sep 21 2024 Pattern Synopsis and Forecast: Midlevel split flow over the CONUS will continue chances of active weather to the Great Lakes region for the first part of the long term. Current above average temperatures influenced by southern branch flow will eventually advect southward. A more active northern branch will allow for cooling temperatures next week. The first shortwave trough currently over the Canadian/Montana boarder will make its way to the Great Lakes region at the start of the Long Term. No impactful weather is expected at this time, but showers and storms could persist across the CWA (at times) through the first half of the forecast period. Upstream ridging eventually returns surface high pressure and sunny skies during the second half of next week around the Wednesday timeframe, but northern branch flow will keep Fall-like temperatures for the entire week. Primary Forecast Concerns/Key Messages: Cooler temperatures move into the Great Lakes region next week: No high impactful weather to discuss during the long term. Biggest story will be the end of warmer than average temperatures as northern branch flow advects southward this Monday. Current daytime highs in the 80s will lower into the upper 60s to low 70s for most areas next week, finally returning temperatures somewhat closer to normal. Showers and storms return this Sunday: Aformentioned troughing will move in this Sunday while developing a weak surface cold front at the same time. While most areas can expect minor QPF amounts (roughly a half inch or so) localized areas that undergo more efficient convection could see locally higher amounts as PWATs climb to well above normal and a warm, deep cloud layer could result in locally higher totals. Additional small showers could continue into Tuesday as strong flow aloft moves through the Ohio Valley, but substantial QPF is not expected at this time. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 143 PM EDT Sat Sep 21 2024 Initial problem for tonight will be redevelopment of LIFR conditions at KCIU/KAPN...fairly confident that KAPN will fog in this evening...KCIU a little more uncertain with visibility but think that lingering St over northern Lake Huron will expand back to the west tonight. More western terminals (KPLN/ KTVC/KMBL) are more likely to avoid this with increasing mid/high clouds tonight (and perhaps a little better breeze)...with shower chances increasing probably after 09z or so with a better thunderstorm threat at KTVC/KMBL closer to the heart of the low level theta-e ridge that pushes into Lower Michigan Sunday morning. && .APX WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ UPDATE...JPB SHORT TERM...JZ LONG TERM...SJC AVIATION...JPB