Area Forecast Discussion
Issued by NWS Gaylord, MI
Issued by NWS Gaylord, MI
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015 FXUS63 KAPX 190345 AFDAPX Area Forecast Discussion National Weather Service Gaylord MI 1145 PM EDT Tue Jun 18 2024 .KEY MESSAGES... - Chances of showers and storms tonight and Wednesday. - Heat continues...periods of relief at times... && .UPDATE... Issued at 1019 PM EDT Tue Jun 18 2024 Upstream cold front remains well upstream of our CWA late this evening...extending from the Arrowhead of Minnesota into NW Iowa and the Central Plains. Several large areas of convection continue to fire along and ahead of this front....but leading edge of this convection is also still well upstream of our CWA. Latest near term models still insist that this convection is going to diminish overnight in both areal coverage and intensity as it tries to make eastward progress into the significantly more stable airmass overhead. Will keep small chances of showers/storms in our far western CWA very late tonight...but expect the vast majority of our CWA will stay dry...warm and humid overnight in ongoing WAA pattern in advance of this upstream cold front. Low temps will only cool into the mid to upper 60s across Eastern Upper Michigan and into the low to mid 70s across Northern Lower Michigan. && .SHORT TERM /THROUGH WEDNESDAY/... Issued at 359 PM EDT Tue Jun 18 2024 Pattern Synopsis/Forecast: 18z surface analysis shows a pair of surface lows west/northwest of the Great Lakes...999mb low over northwest Ontario...trailing cold front to the southwest to a 997mb low along the South Dakota/Minnesota border. A more consolidated warm front extends east of the Ontario low into northern Quebec. The dreaded apocalyptic "heat dome" is centered over the mid Atlantic with deep southwest flow around its west side bringing warmth and moisture into the Great Lakes. Water vapor imagery shows a compact vorticity center lifting northeast across western Lower Michigan... spreading a mostly mid/high cloud deck and some high based radar returns across northern Lower Michigan. But it has also helped sprout a thunderstorm adjacent to Saginaw Bay. Temperatures have mostly leveled off across northern Lower with arrival of cloud cover...areas that have remained in the sun longest from the tip of the mitt around the northeast Lower shoreline have warmed into the 90-95 degree range...93 at PLN ties the record high for today. While the upper anticyclone to the east holds firm and pushes the 594DM height contour into southeast Lower Wednesday...upstream cold front eventually nudges into northern Michigan Wednesday afternoon. Primary Forecast Concerns: Rain chances tonight and Wednesday: Initial rain chances this evening mostly tied to the diurnal heating/instability cycle and aforementioned passing short wave trough that should be crossing Lake Huron by early/mid evening. Once we get this initial activity out of the way should see a lull in the precipitation chances (and clouds for that matter) heading into the early morning hours. But there also appears to be some gravity waves crossing Wisconsin in visible imagery...moving into an uncapped 2000J/kg MLCAPE air mass. So will need to monitor and make sure this feature doesn`t cause any mischief into the evening hours. Ahead of the approaching cold front should be quite a bit of convective activity expected to develop across the Midwest during the late afternoon/evening hours. Leading edge of what remains of this convection may reach eastern Upper/far northwest Lower toward daybreak Wednesday. Cold front expected to push into eastern Upper later Wednesday morning and into northern Lower during the afternoon...with an axis of 1.75-2.00 inch precipitable water along it. Should be a corridor of heating ahead of the cold front which is expected to gin up 1000-1500J/kg MLCAPE across northern Lower... so precipitation chances should increase during the afternoon. Like today deep layer shear is forecast to be relatively minimal (generally under 20kts 0-6km)...so organized severe potential is low outside of some pulse-y severe storms that may gust out. Continued hot and humid Wednesday: Looks like a warm night ahead give humid air mass and southerly breeze which should persist. Temperatures Wednesday will be dependent on cloud cover but will have a head start with expected overnight lows mainly in the 70s. Looks like there should be a corridor of good heating ahead of the front across northern Lower...aided by southwest downsloping into northeast Lower. Expecting areas along/east of the I-75 corridor across northeast Lower should warm into the 90-95 degree range...heat indices in the mid 90s could push the need for a Heat Advisory over northeast Lower but that is call better made by the overnight shift. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... Issued at 359 PM EDT Tue Jun 18 2024 PATTERN SYNOPSIS/FORECAST: Anomalous longwave pattern across North America today...with troughing over the western US into north central Canada...and strong ridging building over the eastern US. Strong southwesterly flow through the column...with upper jet over Canada around 140+kts, and LLJ into the Upper Midwest running around 40-50kts, even after nocturnal influences have diminished. Southwesterly warm advection also aiding in plume of EMLs stretching from the southern Plains well into MN (700mb temps in the low teens). Decaying activity north of this continues to trek through Canada. Subtropical high over the Carolinas resulting in excellent return flow up the MS Valley, with pwats exceeding 1.5-2in. through that region. Pwats even bumping up to 1.46in here in northern MI with our 12z sounding. PV max trekking NNEward into SW MI early this afternoon with attendant shower activity. Looking ahead...expecting aforementioned PV niblet to zip through today into tonight. Upstream PV (southern lobe of broader troughing) over MT to jam its way up into MN going into Wednesday night and Thursday as surface high pressure tries to settle in. However, additional energy diving into the back of this helps shunt it out of the region a bit quicker for the weekend...though there is still some potential it could be a little more active. Aforementioned surface high retrogrades into TN going into the end of the week, with generally pleasant (albeit hot) conditions expected. A clipper- type system approaches the area Saturday, though strength of this feature is still somewhat nebulous, as there`s uncertainty in how deep this feature will develop as it crosses the N. Plains. While both ideas suggest it may not be entirely quiet this weekend (naturally), there is some potential for a more tightly wound system to cross into the area, which could be a little more active and a little breezier. Otherwise...generally zonal flow in the presence of the active storm track suggests we could have some potential for multiple rounds of storms/rain tracking over similar broad areas later in the week/weekend as well, which will be worth keeping an eye on going forward. Perhaps some signals of relief finally arrive on the horizon going into the start of next week, with troughiness trying to return to the Great Lakes again. Primary Forecast Concerns: Heat continues...periods of relief at times... Anomalous subtropical ridge continues to hang on to our south, and as we`re on the periphery of it with the BCZ so close...will expect things will waver back and forth across the area through the period. Cold front wavering south across the region on the southern flank of a stronger push of energy will drag the boundary south into central Michigan Wednesday night into Thursday and stall it out. Expect cooler and somewhat drier air to filter in from the north in its wake, with perhaps even a period of more seasonable weather over the northern half of the CWA. Looks like the boundary pivots back north again on return flow Thursday night into Friday, which should bring heat/humidity back into the picture for the end of the week for us, with highs again into the upper 80s and low 90s (barring any convective debris that could keep things cooler)...with dewpoints up into the 60s again. Generally stalled boundary looks to slowly slide out going into Sunday, with a brief reprieve to more seasonable temps in the 70s/low 80s with lower humidity...though an uptick is possible early next week as another wave of energy approaches and shunts the ridge axis overhead again. Some signals attm for a more definitive cooldown for the end of the period, though not sure how long it will last, given the pattern attm may be rather zonal overall. Storm chances continue...especially this weekend... Current air mass in the presence of an approaching boundary for Wednesday night should help trigger some convection, and potentially through the remainder of the period as it stagnates and meanders back and forth over the area. Generally stagnant flow suggests little shear to support organized storms, though stagnant flow could certainly support the idea of at least slow-moving convection...which, in this anomalously moist air mass, could be problematic from a heavy rain standpoint...as it wouldn`t be impossible for a couple inches or more of rain to fall over a single area...though confidence in this exact area is low, given the nature of convection and the potential mesoscale boundaries that could also enhance this threat. Additionally, as another plume of anomalous moisture floods northward into the region on warm advection Saturday...will certainly have to keep an eye out as training convection is not entirely out of the question...though even so, wherever the air mass is able to get wrung out, it could certainly produce a lot of rain. Especially if this boundary ends up being a bit slower to move through the region. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 1145 PM EDT Tue Jun 18 2024 Upstream cold front currently stretching thru the length of Minnesota into the Central Plains will march eastward into the Western Great Lakes region overnight into Wednesday. Chances of showers and storms will gradually increase on Wednesday along and ahead of this front. Prevailing conditions will remain VFR...but will temporarily drop to MVFR/IFR within any heavier showers and storms that develop. LLWS will develop overnight into Wednesday morning as winds just off the deck strengthen ahead of the approaching cold front. Southerly surface winds at around 10 kts overnight will shift to the west at 10 to 20 kts...and eventually shift to the NW Wednesday afternoon/evening as this cold front sweeps thru our area. && .APX WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...Small Craft Advisory until 5 PM EDT Wednesday for LMZ323-341- 342-344>346. && $$ UPDATE...MLR SHORT TERM...JPB LONG TERM...FEF AVIATION...MLR