Area Forecast Discussion
Issued by NWS Gaylord, MI
Issued by NWS Gaylord, MI
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911 FXUS63 KAPX 041715 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 115 PM EDT Thu Jul 4 2024 .KEY MESSAGES... - Shower/t-storm chances increase late tonight into Friday. Locally heavy rainfall Friday. - Active weather at times next week. && .UPDATE... Issued at 1105 AM EDT Thu Jul 4 2024 Synopsis: Large scale pattern features broad ridging from the southeastern U.S./southern Plains westward into California...west- southwest mid level flow across the Great Lakes north of this ridge and ahead of a short wave trough moving through the Dakotas/ Nebraska. Water vapor imagery also shows a lead short wave trough from southeast Minnesota/eastern Iowa/Missouri. 1011mb surface low over far western Minnesota with some semblance of a warm front extending east into Wisconsin. Another front stretched from the lower Lakes into northern Ohio/Indiana/southern Illinois...south of which dew points were in the 70s. Good bit of sun to start the holiday across northern Michigan with temperatures already in the 70s and dew points in the 60s. More widespread mid/high cloud cover across Wisconsin was spreading northeast...but closest precipitation is west of the Mississippi and south of Lake Michigan with a "bubble" of drier air (in a relative sense) over Michigan/northeast Wisconsin eastward into the lower Lakes. 12z APX sounding reflects this with >15C dew point depressions above 800mb. Boundary layer mixing ratio also drops quickly off the deck (near 11g/kg at the surface to around 8g/kg in residual layer evident from 900-800mb). Forecast Update: Only concern for the afternoon will be lake breeze development and whether any convection will pop along these boundaries over eastern Upper and on the Lake Huron breeze south of Thunder Bay. Dew points are expected to mix down into the 50s for the most part away from the lakes...so only moisture convergence/ onshore flow along these boundaries will keep dew points high enough to squeeze out a modicum of MLCAPE (100-200J/kg). Added lift from short wave trough coming out of the upper/mid Mississippi Valley won`t hurt the cause either especially across Upper Michigan. Background northerly flow will push Lake Superior breeze farther inland so best chance for any development north of the Bridge would be across Mackinac county. A low (but non-zero) probability event for sure. Already setting up to be a warm afternoon with 70s across eastern Upper and 80s across northern Lower away from the lakes. && .SHORT TERM /THROUGH TONIGHT/... Issued at 343 AM EDT Thu Jul 4 2024 Happy 4th of July. Pattern/synopsis: Low pressure over Hudson Bay will move ne- ward. There are multiple surface trofs moving thru the northern lakes, but the departing low will leave behind w-e oriented troffing over the central lakes. Part of this can already be analyzed as a warm/stationary front from eastern SD to central WI. Aloft, a digging shortwave is likely to close off as it transits southern MN tonight. Forecast: Isolated showers are being maintained along a surface trof that extends from south of LDM to north of APN. These will persist for a few more hours, as they move eastward. Otherwise, there are patchy mid clouds over eastern upper and ne lower MI. Early on, surface heating will be relatively uninterrupted, and temps will climb quickly this morning. We remain muggy (surface dew points 60-65f), and that heating will eventually result in a cu field. A partly cloudy afternoon is expected. Temps are warm enough aloft to keep most of northern MI with minimal Cape. But, where lake breezes move inland, and where moisture pooling occurs along them, we may realize up to 300j/kg of MlCape. The areas of interest are the interior of eastern upper MI, and ne lower MI from Rogers to Standish. Isolated showers here are maybe possible, late this afternoon into this evening. The grids will have POPs around 10 percent, but this is not enough to include a mention of a shower. Tonight: as the upper low crosses southern MN, a weak surface wave should take shape just ahead of it. A warm front sharpens to the east of this (especially aloft), over southern WI. The low level jet in the area is weakish, but a very rich airmass is in the warm sector. Beginning late today, deep convection should continue to generated in parts of MN/IA, and eventually WI. Moisture/forcing/instability are all better west of Lake MI than east, and CAMs are disagreeing considerably as to how far east precip will get. Have kept the evening dry, before shower/ t-storm chances increase overnight. Highest pops are after 4-5am, west of I-75 in both peninsulas. Respectable precip rates are possible...but are much more likely to be realized on Friday and beyond. Max temps mid/upper 70s north, to upper 80s far se. Lows mid 50s to mid 60s. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Issued at 343 AM EDT Thu Jul 4 2024 Primary Forecast Concerns/Key Messages: Midlevel split flow pattern for the first half of the long term followed by broader troughing next week will continue chances of showers and storms at times throughout the entirety of the forecast period. Embedded shortwaves will produce the best chance of widespread rainfall across the CWA this weekend and early next week. The first trough with relatively weak surface low pressure currently over the northern planes will progress to the Upper Midwest by late Thursday night. The second main round of showers will not arrive until Tuesday as an additional trough moves across the upper Great Lakes region. Primary Forecast Concerns: Showers and storms return this Friday. Locally heavy rainfall remains possible: Latest ensembles show weaker forcing compared to past model runs along with lower H8 winds. With more potential atmospheric stability and less southerly moisture feeding into the CWA, lower QPF can be expected. The disheveled core of low pressure is expected to track across central Michigan, delivering a general half inch or so of QPF, but locally higher amounts can be expected as PWATs remain quite juicy (well over an inch). Longwave troughing will keep chances of active weather at times next week: Aformentioned split flow followed by longwave troughing across the northern half of north America will keep active weather at times for the remainder of the forecast period. Best chance of widespread rainfall is on Tuesday as another shortwave drops from northern Hudson Bay to the Upper Great Lakes. Longwave troughing after Tuesday will keep chances of diurnal pop-up thunderstorms like a typical northern Michigan summer. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 111 PM EDT Thu Jul 4 2024 VFR conditions expected through tonight with plenty of mid/high cloud expected but low levels are dry. Better precipitation chances at the terminals not expected until late tonight into Sunday morning...and along with it some MVFR conditions expected mostly due to visibility restrictions as cloud heights will continue to come down. && .APX WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ UPDATE...JPB SHORT TERM...JZ LONG TERM...SJC AVIATION...JPB