131 FXUS63 KDLH 111456 AAA AFDDLH Area Forecast Discussion...UPDATED National Weather Service Duluth MN 956 AM CDT Wed Sep 11 2019 .UPDATE... Issued at 956 AM CDT Wed Sep 11 2019 Please see the updated Marine Discussion below. && .SHORT TERM...(Today through Thursday night) Issued at 353 AM CDT Wed Sep 11 2019 A quick round of rain showers will graze portions of the southern forecast area today, followed by more widespread and persistent showers, with some embedded thunderstorms Thursday and Thursday night. Moderate to heavy rainfall is very likely across the entire Northland, with the heaviest rain expected along the North Shore on Thursday and Thursday evening. The synoptic pattern doesn't change much through tonight as a longwave mid-level trough will slowly translate eastward over the Intermountain West states. A mid-level impulse has ejected from this parent trough, and has brought some light rain showers over our southwestern counties as of 08z/3 AM this morning. Instability for thunderstorms looks to stay just to our south, especially along a warm frontal zone, which is currently draped across southern Minnesota. A line of strong thunderstorms has developed, with a parallel stratiform rain region over our area. The shortwave aloft will gradually make its way eastward, which will bring some heavier rainfall over our southern counties later this morning. Winds will be from the northeast today and Thursday as high pressure across northern Ontario and surface low pressure associated with the longwave trough ascends northeastward towards the Northland. Winds will be fairly breezy today, strongest right along Lake Superior, with gusts between 15 to 25 mph. Total rainfall amounts over northwest Wisconsin through midnight tonight will range between one-tenth of an inch up to one inch over southern Price county. The surface low and the parent longwave trough will arrive late in the day Thursday, with the surface low expected to be over the MN/ND border by 00z Friday/7 PM Thursday. The low will help lift the surface warm front into the region, helping to enhance theta-e advection and increase instability. Southerly flow ahead of the surface low will help advect copious amounts of moisture, characterized by PWAT values in the ballpark of 1.5 to 1.9 inches. These values are above 98% of climatology, per the NAEFS precipitable water climatological anomalies, so plenty of moisture to generate moderate to heavy rainfall. QPF has been a challenge as the consensus blends have been a bit too high the last few days. Instead, we leaned more heavily on the WPC QPF, which seems to be closer to the 50th percentile for QPF. Using this, QPF amounts for Thursday through Friday generally range from around 1.4" over north-central Minnesota to around 2.5 inches along the North Shore. Instability appears to remain fairly modest, despite the increasing theta-e values, with most-unstable CAPE in the 500 to 1000 J/kg range. Deep layer bulk shear will be more favorable for thunderstorms, thanks to a 35 to 45 knot low-level jet ahead of the surface low. The Storm Prediction Center has a Marginal risk for our southern tier of counties, from Pine to Price. The most likely time for thunderstorm activity will be Thursday afternoon and evening when the more favorable instability increases and the better large-scale forcing moves through. Gusty northeast winds will continue on Thursday, and even strengthen further, with gusts from the Twin Ports north to the Minnesota Arrowhead will reach up to nearly 30 knots. The surface low will linger over the region into Friday morning, which will keep chances of showers, and maybe a thunderstorm or two, over the region. Chances of rain showers continue through the day Friday. .LONG TERM...(Friday through Tuesday) Issued at 309 AM CDT Wed Sep 11 2019 After cool and rainy weather mid to late week, a pattern change leads to a period of summer-like weather early next week with highs approaching the low 80s Monday and Tuesday. Rain comes to an end Friday in the wrap-around flow of the low pressure that will bring the mid/late week rain, then a chance for some showers on Saturday night. Dry Sunday and Monday, and very low chance for showers Tuesday, then a better chance for precipitation Tuesday night into Wednesday. On the synoptic scale, the work week ends with a mature low of the northern MN/Ontario border lifting northeast, causing cooler wrap-around flow to advect into the Northland as the low exits to the north. Light rain showers are expected Friday, but less than a tenth of an inch of rain is expected, with decreasing clouds from south to north Friday night. While there is a possibility for cool temps, at this point the timing of the exiting low across most guidance would lead to too much cloud cover for temperatures to really drop below the upper 30s, but this could change. Highs in the On Saturday a sunny start, but a quick-moving mid-level shortwave trough moving east across the North Dakota/Canada border on Saturday will approach the Northland late Saturday into Saturday night. Southwest flow at low levels ahead of the wave will begin advecting in increasing warm air and some richer low level moisture, and while dew points values will not be very impressive - in the mid 50s by late Saturday afternoon - there will be at least modest instability values around 500 to 1000 j/kg MUCAPE in the afternoon hours as well as deep layer shear values around 40-50 knots. While conditions are not great for surface-based convection, if any storms can develop in this environment ahead of the mid-level wave, they could be strong supporting the possibility for hail and strong winds going into Saturday night. Coverage would likely be limited, but still a few strong storms could be possible. Highs in the 60s to near 70 on Saturday. Warmer late-weekend into next week with a very strong mid/upper level ridge building over the Great Lakes region. At low levels, southwesterly flow will advect in 850mb temps approaching +25C - values that would be considered over the 90th percentile even in the middle of the summer, and for mid-September in near the 99th percentile compared to climatology for the Upper Midwest. Highs will generally be in the 70s Sunday through Wednesday, with some spots south of Highway 2 approaching 80 degrees on Monday and Tuesday, which is about 15 to 20 degrees above normal for mid September. Dew points will rise into the mid 60s, making it feel fairly humid as well. An increasing chance for precipitation towards mid-week as a deep longwave trough across the west coast ejects into the Great Plains. && .AVIATION...(For the 12Z TAFS through 12Z Thursday morning) Issued at 956 AM CDT Wed Sep 11 2019 No major changes in the latest update. Did bump up winds a few knots based on the latest observations. Utilized the latest DLHWRF model to do this. Previous discussion A deepening area of low pressure across the Upper Midwest will lead to increasing northeast winds today, remaining strong tonight into Thursday before becoming more easterly and the finally weakening Thursday night. Winds will be steady 15 to 25 knots much of the time across western Lake Superior with gales to near 35 knots possible Thursday afternoon, especially along the north shore. At this point confidence is not high enough for a Gale Watch, but one may be needed on future shifts. Wind will also lead to building waves, with wave heights as high as 6 to 10 feet along the north shore Thursday afternoon into Thursday evening. A round of showers possible today, then heavy rain with occasional thunderstorms Thursday into Thursday night. Heavy rain may obscure visibility to a mile or less at times. Conditions improve Friday as the low pressure system exits to the north, with winds shifting to become southwesterly 10 to 20 knots Friday into Friday night, westerly 5 to 15 knots on Saturday. && .MARINE... Issued at 309 AM CDT Wed Sep 11 2019 A deepening area of low pressure across the Upper Midwest will lead to increasing northeast winds today, remaining strong tonight into Thursday before becoming more easterly and the finally weakening Thursday night. Winds will be steady 15 to 25 knots much of the time across western Lake Superior with gales to near 35 knots possible Thursday afternoon, especially along the north shore. At this point confidence is not high enough for a Gale Watch, but one may be needed on future shifts. Wind will also lead to building waves, with wave heights as high as 6 to 10 feet along the north shore Thursday afternoon into Thursday evening. A round of showers possible today, then heavy rain with occasional thunderstorms Thursday into Thursday night. Heavy rain may obscure visibility to a mile or less at times. Conditions improve Friday as the low pressure system exits to the north, with winds shifting to become southwesterly 10 to 20 knots Friday into Friday night, westerly 5 to 15 knots on Saturday. && .PRELIMINARY POINT TEMPS/POPS... DLH 52 48 55 50 / 50 80 100 90 INL 55 47 56 50 / 10 50 90 100 BRD 59 52 61 51 / 40 90 100 40 HYR 59 51 62 52 / 90 80 100 90 ASX 56 50 58 52 / 70 70 100 100 && .DLH WATCHES/WARNINGS/ADVISORIES... WI...Beach Hazards Statement until 9 PM CDT this evening for WIZ001. MN...Beach Hazards Statement until 9 PM CDT this evening for MNZ037. LS...Small Craft Advisory until 10 PM CDT Thursday for LSZ121-142>148. Small Craft Advisory from 4 AM to 10 PM CDT Thursday for LSZ140- 141. && $$ UPDATE...WL SHORT TERM...JTS LONG TERM...JJM AVIATION...WL MARINE...JJM