Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, MI
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245 FXUS63 KMQT 191117 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 717 AM EDT Thu Sep 19 2024 .KEY MESSAGES... - Extended stretch of well above normal temperatures continues through at least Saturday with highs mainly in the upper 70s and 80s. - A cold front brings scattered showers and a few thunderstorms late today into Friday. Some stronger storms are possible in western Upper Michigan this evening. - Temperatures around normal are expected to return for next week. && .SHORT TERM /THROUGH THIS AFTERNOON/... Issued at 334 AM EDT Thu Sep 19 2024 Water vapor imagery and RAP analysis show troffing over the western U.S. with one well-defined mid-level low over se Saskatchewan and a second just off of the central CA coast. Some shra/tsra are occurring across MN ahead of the former mid-level low. Mid-level ridging is over the western Great Lakes. So, once again, it`s another early morning just like the last several. With stirring s winds closer to Lake Superior, it`s a 4th day in a row with early morning unseasonable warmth in the downslope areas near Lake Superior from western to n central Upper MI. As of 07z, temps are still in the upper 60s F in that area. For the 4th night in a row, Big Bay is the warm spot. Three nights ago, the temp at Big Bay was 76 at 07z, 2 nights ago it was 75, last night it was 73F and this morning its 70F. Just like previous nights, temps fall off significantly to the e and s. Across s central and eastern Upper MI, temps are as low as the mid 40s F at traditional interior cool spots as winds are decoupled, and a dry column has further enhanced the radiational cooling, but temps ranging thru the 50s F are generally the rule. With the cool conditions, fog has once again developed in that area. The areas of fog, locally dense, will burn off 1-2 hrs or so after sunrise. The Saskatchewan mid-level low and associated sfc low will drift into southern Manitoba today. Trailing occluded front moving e across MN will be the focus for late day convective development within a sharp 850mb theta-e ridge and MLCAPE building to 1500- 2500j/kg. This main area of developing convection will remain w of Upper MI thru about 00z. Earlier in the day, focus is on convection over MN in association with low-level jet/theta-e advection. Should see some additional development across MN over the next several hrs on eastern edge of low-level jet where theta-e advection is sharper. This convection should weaken/dissipate as it approaches Upper MI late morning/early aftn as low-level jet weakens. For now, have left pcpn mention out of fcst. Trends will be monitored as the morning progresses to assess whether pcpn needs to be introduced. Otherwise, expect one more day with temps exceeding 80F over much of the fcst area. Models indicate mid morning 850mb temps to be similar to 24hrs ago, so highs should be within a couple of degrees of yesterday`s highs at most locations. Ongoing, lengthening dry spell remains a concern for wildfire potential. Winds will be a little stronger today than yesterday with gusts getting into the 15-20mph range across the w and n. Dry air mix down potential today doesn`t appear to be quite as good as yesterday, so min RH should bottom out around 35pct today. Will certainly be something to monitor this aftn due to a little more wind today. && .LONG TERM /TONIGHT THROUGH WEDNESDAY/... Issued at 315 AM EDT Thu Sep 19 2024 Some active weather starts off the extended forecast tonight as a cool front pushes in from the west, bringing with it showers and thunderstorms over Upper Michigan. With MUCAPE between 1k to 2k J/kg and 0-6 km bulk shear being around 25 to 35 knots, we could see a few strong thunderstorms over the western U.P. this evening a couple of hours after the sunset, with namely strong winds and large hail being the main threats. However, as the front and precipitation travel eastward with time tonight, the convection looks to outrun the better CAPE and shearing, causing the strong storm threat to end around midnight over the central U.P.. While rainfall amounts from the front won`t be all that impressive (mainly between 0.10 and 0.30 inches), we could see a few isolated spots, mainly over the west and central, that could see some localized soaking rainfalls as the heaviest downpours move over them (PWATs will be around 1.50 inches). In addition to the rainfall, we could also see some record warm low temperatures tonight as the antecedent warm air along with the cloud cover will work to keep lows from reaching the 50s. The showers and storms continue over the east half Friday as convection redevelops behind the initial line. While not expected, there is a small, outside chance (2% or less) that we could see a strong storm or two over the central and east, even though the conditions are not as ideal as what they will be over the far west this evening. Expect slightly cooler temperatures too on Friday, with highs only being in the 70s. The rainfall associated with the front looks to get out of here by Saturday morning as weak ridging moves overhead. More dry weather and well above normal temperatures return Saturday as weak, localized ridging looks to keep precipitation and cloud cover away. Expect to see high temperatures return into the upper 70s to low 80s once again Saturday, meaning that some spots in the U.P. may flirt with tying or breaking their daily max temperature record. However, as a cold front from our north and west phases with a shortwave low lifting from the Plains through the U.P. Saturday night and Sunday, we could see showers return to the area. Currently, the expectation is that the rainfall from this will be fairly light. Temperatures will return to around normal next week behind this cold front, with highs generally being in the 60s and lows in the 50s to mid 40s later in the week. We may see additional rainfall over mainly the central and east around next Tuesday as a low lifts from the Southern Rockies into the Upper Midwest. However, model agreement is still shaky at this time, so confidence in this occurring is still pretty low (30-40% chance). Behind this low, expect surface ridging to return to the Great Lakes region by the latter half of next week. && .AVIATION /12Z TAFS THROUGH 12Z FRIDAY/... Issued at 717 AM EDT Thu Sep 19 2024 Fog that advected northward to SAW overnight will dissipate around 14z, resulting in LIFR improving to VFR. Otherwise, expect VFR to prevail thru the aftn at IWD/CMX/SAW. Southerly winds will prevail, gusting to around 20kt at IWD. Shra and some tsra will spread w to e across Upper MI tonight. Best chc of tsra will occur at IWD/CMX. While fcst maintains VFR at IWD/CMX, potential is there for MVFR during any periods of heavier rainfall. At SAW, upslope southerly winds and shra should result in MVFR developing overnight. && .MARINE... Issued at 315 AM EDT Thu Sep 19 2024 Light winds of 20 knots or less today give way to southeast to southerly winds of 20 to 25 knots over the central lake this evening as a cool front slowly trudges from west to east today through Friday. This front will bring some showers and storms across the lake, with some storms possibly being strong to severe over the west (the main threats being strong, erratic winds and large, damaging hail). As the front moves eastwards with time, expect the severe threat to diminish, particularly by around midnight tonight EDT. While winds generally decrease to 20 knots or less across Lake Superior by Friday morning, the showers and storms continue along the front through Friday night. Weak ridging over the area keeps winds light Saturday before a cold front passes through Saturday night and Sunday from the west. Currently, we could see northwesterly winds gust to 20 to 25 knots behind the cold front over the western half of the lake late Saturday night and Sunday. In addition, expect to see some showers and a few thunderstorms with the front`s passage Saturday night through Sunday, although the convection isn`t a guarantee as some models do keep the lake rain- free (50 to 60% chance of occurrence). Another low lifting from the Southern Rockies may lift into the Upper Great Lakes around the Tuesday time period too and bring stronger winds and thunderstorms back across the lake, but uncertainty on this occurring is higher (around 30 to 40% chance of occurrence). && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Rolfson LONG TERM...TAP AVIATION...Rolfson MARINE...TAP