Area Forecast Discussion
Issued by NWS Marquette, MI
Issued by NWS Marquette, 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
44
45
46
47
48
49
50
128 FXUS63 KMQT 011124 AFDMQT Area Forecast Discussion National Weather Service Marquette MI 724 AM EDT Wed May 1 2024 .KEY MESSAGES... - Breezy west winds gusting up to 40 mph, mainly this afternoon. - Active pattern continues through next week as a series of low pressure systems track across the U.S. and affect Upper MI. Above normal precipitation expected, including chance of thunderstorms at times. - Temperatures won`t stray too far from normal most days, but they will be above normal more often than below normal. && .SHORT TERM /THROUGH THIS AFTERNOON/... Issued at 347 AM EDT Wed May 1 2024 The well-advertised band of rain showers is lifting northeast across the UP along a warm front extending east from a 1002 mb surface low west of Duluth. Lightning is mostly absent from ongoing activity, but there is a cluster of lightning/thunderstorms near Green Bay, WI where SPC Mesoanalysis analyzed around 250 J/kg MUCAPE. Surface observations across the UP show temperatures mainly around 40F though there are mid-40s near the WI state line. Light east- southeast winds advected moisture off Lake MI allowing low stratus and fog to develop across east-central portions of the area where clear skies occurred last evening. Increasing upper level clouds make it difficult to see fog/stratus on RGB satellite imagery, but several eastern UP surface observations indicate vsby at or below 1 mile. Looking ahead through today, any lingering fog should diminish as rain moves through this morning. Rain ends early this morning across most of the west-central UP, but the Keweenaw and eastern UP will be slower to dry out. The track of the low pressure remains low confidence and has important implications for today`s wind forecast. The most likely scenario is a surface low over eastern Lake Superior by early afternoon with the associated cold front passage already across most of the area. Despite very dry mid-levels, model soundings indicate sufficient boundary layer moisture for nearly continuous stratus or broken cumulus that limits surface heating and mixing depth. This lowers confidence in afternoon wind forecast, but EFI values of 0.7-0.9 and SoT >0 indicates unseasonably strong winds. EPS output and sounding analysis suggests potential for westerly gusts to around 40 mph especially across the south-central UP where mid- level winds are stronger and downsloping west winds allow for deeper mixing. Downsloping also boosts high temps into the low 60s across the south-central with 50s elsewhere except for 40s on the Keweenaw. Across the eastern UP, west winds back Nwerly this afternoon as the low pressure tracks over Ontario resulting in a pseudo lake breeze/cool front that may force a shower or two across the far east. && .LONG TERM /TONIGHT THROUGH TUESDAY/... Issued at 505 AM EDT Wed May 1 2024 Last 24hrs of medium range model guidance has maintained continuity in showing that the recent active pattern across the Lwr 48 will continue thru next week as a series of vigorous waves track off of the N Pacific and then across the U.S. This pattern will be beneficial in easing ongoing drought over western and eastern Upper MI as frequent rainfall events are expected, some potentially mdt to hvy. The latest drought monitor from 4/25 indicated drought conditions in western Upper MI were into the severe category in portions of Gogebic/Ontonagon counties. To the e, moderate drought was indicated from eastern Delta to western Mackinac counties. The frequent pcpn events will also ease spring fire weather concerns. So, expectation is for overall above normal pcpn thru next week. As for temps, with the progressive nature of the flow and frequent shortwave passages, expect temps fluctuating around normal, likely not straying too far from normal on most days, rather than any prolonged periods of well above or well blo normal temps. Daily temps will end up on the warm side of normal more often than the cool side. Farther down the road, there are indications for a cooler period mid month per recent EPS runs which show troffing/weak negative height anomalies setting up over the Great Lakes region and ne U.S. CFSv2 ensemble mean also supports a cooler period mid month. Beginning tonight, sfc high pressure ridge builds over the area in the wake of the passing shortwave today. Result will be a dry, quiet night, but lower level moisture/clouds from today will likely linger tonight for many areas. Expect min temps ranging through the 30s F. W half has best chc of seeing a decrease in cloud cover, so lowest readings are expected in the traditional interior cold spots of the w. Also, if it does clear out over the w, some radiation fog could develop. Attention then shifts to the next shortwave swinging across the Rockies tonight and out over the Northern Plains on Thu. In response, strong waa/isentropic ascent will advance across the Upper Mississippi Valley to Upper MI Thu aftn/night. Strong 850-700mb moisture transport is also noted with precipitable water increasing to 200-250pct of normal. As a result, expect shra to spread ne into Upper MI during Thu aftn, especially across the w half. Shra will then continue across the area Thu night. Rainfall amounts should be on the order of 0.25-0.50 inches. Ensemble probability guidance indicates a 30-60pct chc of exceeding 0.50 inches, and only a 10- 20pct chc of exceeding 1 inch. Overall model trend has been to lower cape avbl for parcels lifted from top of sfc based inversion. So, potential of thunder has diminished. On Fri, low pres will lift across western Lake Superior or ne MN early in the day and then into northern Ontario. Shra will end from w to e as associated cold or occluded front crosses the fcst area late Thu night thru early Fri aftn. With sharp drying occurring in the wake of the front, skies will trend mostly sunny early Fri over the w and later aftn across the e. High temps will range thru the 60s to lwr 70s F. Will be cooler near Lake Superior where westerly winds are an onshore wind and also near Lake MI as a southerly wind component will linger. Deepening mixed layer under increasing insolation will lead to a breezy day w, especially Keweenaw where gusts to around 30mph should occur. Dry weather will continue Fri night. Then, next shortwave will already be approaching by Sat aftn, resulting in a chc of shra spreading w to e Sat aftn/night. Model trends are toward a drier scenario, and ensemble guidance only indicates a 20-30pct chance of rainfall exceeding a tenth of an inch. Fcst will only reflect 30- 40pct chc of shra Sat aftn/night. In the wake of the shortwave, dry weather returns for Sun with sfc high pres ridge arriving. Model agreement has notably improved for dry weather to continue on Mon as a more amplified mid-level ridge shifts over the area. While there is more uncertainty in timing shortwaves beyond Mon as is typical at this time range, models have trended toward better agreement. Next wave is likely to arrive Tue, bringing the next round of shra in the ongoing active pattern. Shra chc will continue on Wed as a potential mid-level low approaches from the w. && .AVIATION /12Z TAFS THROUGH 12Z THURSDAY/... Issued at 723 AM EDT Wed May 1 2024 Band of showers has lifted quickly northward across the U.P. this morning with the back edge already clearing KSAW and KIWD. Expect another hour or two of rain at KCMX before ending. IFR Cigs exist at all 3 TAF sites and they should persist through at least midday before improvement to MVFR at KIWD and KSAW this afternoon. Cigs won`t lift above IFR at CMX until later this evening. Winds will be gusty from the west at all sites...especially this afternoon. && .MARINE... Issued at 505 AM EDT Wed May 1 2024 Low pres will track e across Lake Superior today from near Duluth to near Michipicoten Island. E to NE winds gusting up to 25-30kt are expected in advance of the low. Attention then turns to eastern Lake Superior to the e of the Keweenaw this aftn. As the low tracks to near Michipicoten Island, westerly winds will increase to its s in a corridor from the lee of the Keweenaw toward Whitefish Pt. Guidance has trended weaker with the low pres, and thus the probability of low end gale gusts is only 20-40pct, mainly running from near the Huron Island to Grand Marais for about a 3-5hr period mid aftn to early evening. High pres ridge arrives tonight, resulting in a quick drop of winds to under 20kt across the lake. Lighter winds under 15kt will linger across eastern Lake Superior on Thu. Over western Lake Superior, ne winds will be on the increase again on Thu as the next low pres moves out over the central Plains. Expect NE winds up to 30kt by late Thu aftn over far western Lake Superior. E to SE winds will increase up to 30kt over eastern Lake Superior Thu night. Probability guidance indicates a 10-30pct chc of low end gale gusts. As low pres lifts into northern Ontario on Fri, winds will shift s to sw. While gusts up to 30kt will continue over western Lake Superior, winds will fall off to under 20kt over the eastern lake. Over the weekend, expect winds mostly under 20kt across Lake Superior. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Small Craft Advisory until 3 PM EDT /2 PM CDT/ this afternoon for LSZ240. Small Craft Advisory until 8 PM EDT /7 PM CDT/ this evening for LSZ241-242-245-246. Small Craft Advisory until 11 PM EDT this evening for LSZ243- 244. Small Craft Advisory from noon today to 10 PM EDT this evening for LSZ247-248. Small Craft Advisory from 3 PM this afternoon to 2 AM EDT Thursday for LSZ249. Small Craft Advisory from 2 PM this afternoon to 8 AM EDT Thursday for LSZ250-251. Lake Michigan... Small Craft Advisory until 8 PM EDT this evening for LMZ250. && $$ SHORT TERM...EK LONG TERM...Rolfson AVIATION...MZ MARINE...Rolfson