Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/19/24


Area Forecast Discussion
National Weather Service Bismarck ND
951 PM CDT Sat May 18 2024 .KEY MESSAGES... - Low to medium rain shower chances (20 to 40 percent) return late tonight into early Sunday morning. - There is a Marginal Risk of severe weather (level 1 out of 5) late Sunday afternoon into the evening hours. - High temperatures remain cool through the next work week, mainly in the 60s. Expect daily low to medium (20 to 40 percent) chances for showers and thunderstorms through the week. && .UPDATE... Issued at 949 PM CDT Sat May 18 2024 Clear skies and calm winds as the daytime heating driven clouds have died. It will be a calm night before clouds and some light showers move in early morning. UPDATE Issued at 643 PM CDT Sat May 18 2024 The diurnal cumulus continue to slowly die across most of the area and will be clear skies be sunset. Winds are also relaxing and will go calm after sunset as well. The Wind Advisory will be allowed to expire as winds are calming now. && .DISCUSSION... Issued at 231 PM CDT Sat May 18 2024 An upper low continues to spin off to the east just north of the Canadian border over eastern Manitoba. Associated light rain showers continue over Bottineau and Rolette counties, but should move out in the next hour or two. Western and central North Dakota generally sits under the influence of near zonal flow aloft but we will see some subtle ridging move across the state through the rest of the day. While visible satellite imagery shows a decent amount of fair weather cumulus, this progressive ridging should lead to some subsidence across the west, leading to some clearing. The strongest cold air advection and pressure rises have mainly moved off to the east, so while it will remain windy though the rest of the afternoon (winds out of the west northwest), it should very gradually diminish as we move towards sunset. Given the tight pressure gradient, we are still expecting sustained winds up to 30 mph and gusts to 45 mph for a few more hours. Thus, the Wind Advisory still looks to be in good shape. Late tonight and into Sunday morning, we will gradually transition to southwest flow aloft as a Pacific Northwest trough starts to approach. Warm air advection may lead to some low to medium (20 to 40 percent) chances for hit and miss showers late tonight into Sunday morning, mainly across the south central and James River Valley. This activity should move north through the morning and into the early afternoon but uncertainty remains about how long it will be able to sustain itself. A better chance for showers and thunderstorms (40 to 70 percent) should start to develop over the south central and James River Valley by late Sunday afternoon and into the evening hours. A surface low will start to deepen over South Dakota with an inverted surface trough extending to it`s north northeast. This boundary should be the focus for thunderstorm development by the late afternoon hours. Across the far south, RAP soundings suggest the potential for up to 2000 J/kg of MUCAPE. However, looking at MLCAPE, we generally max out in the 500 to 1000 J/kg range. Still, with forecast deep layer shear will range from 45 to 55 knots over the same area. On paper, these parameters should be more than enough for a strong to severe storm or two. However, there are concerns with moisture quality and depth. It is also worth noting that the RAP is a bit more bullish on higher instability than most of the other short term models (but the RAP still shows fairly "skinny" CAPE which may mean relatively narrow updrafts). That being said, deep layer shear vectors will mainly be orthogonal to the surface trough so storms that do form could be discrete or semi- discrete. The Storm Prediction Center has placed Emmons, Logan, McIntosh, LaMoure, and Dickey counties in a Marginal Risk (level 1 of 5) for severe weather. After analyzing soundings and the latest CAMS, we have decided to message the marginal severe weather potential up to Kidder, Stutsman, and Foster counties as well. For now, we will message wind gusts up to 60 mph and hail to the size of quarters. The one caveat is that if the RAP were to verify, these thresholds would possibly be too low. However, the RAP appears to be an outlier right now, maybe not mixing out dewpoints enough. Regarding temperatures, Sunday will be the warmest day of the week with highs ranging from the lower 60s to the lower 70s. By Monday we will only see lower 70s in our far southeast with highs in the 60s elsewhere. Highs will mainly be in the 60s through midweek. The coolest days will then be possible towards the end of week (Thursday and Friday) when we could see some highs in the upper 50s to lower 60s. The active progressive flow will also continue through the week, leading to daily low to medium (20 to 40 percent) chances of precipitation at various locations across western and central North Dakota. Thunderstorm potential will be limited given the cooler temperatures but a slight chance seems warranted towards the end of the week across the south as most models have a potent trough moving into the region (Thursday-Friday). The eventual track of this trough and associated upper low is still a bit up in the air. Most models/ensemble members have this feature but substantial uncertainty remains regarding the track and strength. It may be worth nothing that CIPs extended analogs suggest some severe potential across our south by the end of the week, but CSU Machine Learning guidance is not showing the potential at this point. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 950 PM CDT Sat May 18 2024 Calm winds and clear skies overnight before VFR clouds move in early morning. Showers are possible at every terminal at some point in the late afternoon so included VCSH. Winds will increase to around 20kts Sunday from the southeast. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Smith DISCUSSION...ZH AVIATION...Smith
Area Forecast Discussion
National Weather Service Cleveland OH
1016 PM EDT Sat May 18 2024 .SYNOPSIS... High pressure slides across the region tonight and Sunday. A weak cold front approaches from the northwest Sunday night before lifting well to our north as a warm front on Monday. A cold front is expected to push through on Wednesday. && .NEAR TERM /THROUGH SUNDAY NIGHT/... 9:30 PM Update... Convection has completely dissipated, and that will allow for a dry night as high pressure builds overhead. We just await the development of radiation fog. Temp/dew point spreads are larger than last night, and we mixed well this afternoon, so that will make the fog less dense and less widespread than last night. However, the latest RAP forecast soundings still show a low- level inversion late tonight, especially in NE Ohio and NW PA, and enough low-level moisture lingers to cause at least mist with pocket of dense fog in the sheltered valleys. For these reasons, kept patchy fog in most of the area overnight, with areas of fog in NE Ohio and NW PA, but not enough confidence on coverage and duration for any special weather statements at this point. Lakeshore areas near the Islands have the best potential for locally dense fog outside of NE Ohio and NW PA where light NE flow will advect some lake moisture below the inversion, so a fog bank could redevelop on the lake and affect communities near the western and central basins. Many HREF members show high probabilities of this, but confidence is still somewhat low due to the overall environment being a little drier than 24 hours ago. 6:30 PM Update... Increased PoPs over an axis from Morrow and Knox Counties through southern Richland, Ashland, Wayne, and Stark Counties over the next 1-2 hours. A weak boundary associated with a lingering mid-level vort max over eastern Ohio is generating persistent convection along its low-level convergence where MLCAPE of 500-1000 J/Kg is present. PWATs are only around 1 inch in that area, but these cells have produced efficient rainfall rates of 2 inches in 30 to 45 minutes! This is due to training and very slow movement of around 5 kts or so. Expect this pulse convection to finally wane after 23Z as the sun angle decreases. The rest of the forecast remains on track. Original Discussion... Relatively benign weather is expected for the remainder of the weekend. The combination of heating of a somewhat moist low- level airmass, a subtle vort max overhead, and some low-level convergence over the Mid Ohio region has allowed isolated showers and thunder to develop. Expect this activity to dissipate by around sunset. Weak high pressure then slides through tonight and Sunday leading to partly to mostly clear skies and dry conditions for most of the forecast area through the rest of the near term. A weak cold front will try to approach Northwest Ohio late Sunday afternoon / evening before lifting north to start the week. Strong upper ridging will be in place, though forecast soundings depict modest to moderate and uncapped instability near Toledo late Sunday afternoon / evening. Enough hi-res models have isolated to scattered convection nearing Northwest Ohio late Sunday to maintain some 20-30% POPs to cover the potential. Weak shear and forcing suggest any storms will be of the single cell or "pulse" variety. Thermodynamics may be sufficient for a couple of cells to produce locally gusty winds or small hail in Northwest Ohio late Sunday, though overall am not too concerned about any kind of organized strong to severe storm threat. Any storms that make it into Northwest Ohio should rain themselves out by late Sunday evening with dry weather for the rest of Sunday night. Lows tonight will generally settle into the 50s. It will be quite warm on Sunday, with highs in the low to mid 80s with the exception of the eastern lakeshore where onshore flow will keep conditions cooler. Lows Sunday night will be quite mild, ranging from the mid to upper 50s from far eastern OH into PA to the mid 60s along and west of I-71. Some radiation fog is likely again late tonight and very early Sunday though coverage should not be as widespread as Friday night into early this morning. The most widespread fog with pockets of dense fog will be from interior eastern OH into western PA, with fog more patchy and generally not quite as dense farther west. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... Mid to upper level ridging will gradually build east during the day Monday before an upper trough and embedded shortwave clips Northwest Ohio on Tuesday. For now, have low end PoPs confined to Northwest Ohio for Monday afternoon and along and west of I-71 Tuesday afternoon. The upper trough becomes more pronounced Tuesday night as the surface low moves northeastward while deepening. This low will swing a cold front toward the Ohio Valley region to end the short term and begin the long term period. Temperatures will rise nearly 10-15 degrees above normal Monday and Tuesday with highs in the mid to upper 80s. Warm overnight lows Monday and Tuesday night in the mid to upper 60s. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... The aforementioned deepening low pressure will drag a cold front east across the local area on Wednesday and bring increased shower and thunderstorm chances to the region. The environment continues to look favorable for strong to severe storms develop as we`ll remain in the warm sector with dew points in the low 60s with current guidance suggesting roughly 1000-1500+ J/kg of MLCAPE to work with. We will continue to monitor the severe weather potential for Wednesday as we get more model guidance. Trended drier toward the end of the week behind the cold front as a brief ridge of high pressure builds northward for Friday. Highs top out in the lower 80s ahead of the cold front on Wednesday before returning to near normal values in the mid 70s Thursday through Saturday. Overnight lows through the long term settle in the mid 50s each night. && .AVIATION /00Z Sunday THROUGH Thursday/... Convection near KMFD is dissipating and should be gone by 00Z. This will leave VFR at all sites through the evening. The main question mark for tonight continues to be how much fog will develop? Most areas mixed well today, so it should be less widespread than last night. However, another inversion will develop tonight, so think most areas should go down at least below 5 miles, with pockets of 1/2 to 1 mile visibility in fog as temp/dew point depressions remain small. The duration of the most dense fog should be shorter, but KERI could still have dense fog much of the night due to added low-level moisture advection off of Lake Erie. Any fog/mist will gradually dissipate by mid to late Sunday morning, but it could once again hang on at KERI into the early afternoon. Light N to NE winds this evening will turn light and variable tonight before becoming N at 5-10 knots Sunday. Outlook...Low risk for isolated thunderstorms in Northwest OH Monday night. Somewhat greater potential for isolated to scattered thunderstorms Tuesday afternoon and evening. Scattered to widespread thunderstorms are likely Wednesday afternoon. Mainly VFR is expected outside of thunderstorms. && .MARINE... Satellite imagery and local area webcams of Lake Erie indicate vast improvement of visibilities and thus the Dense Fog Advisory was cancelled. Moist low levels under a steep inversion overnight tonight will likely prompt the issuance of another fog headline over the lake. Low confidence in exact timing and placement of overnight fog so opted to hold off on issuing a new Dense Fog Advisory for overnight tonight with this forecast update. High pressure persists through the weekend keeping winds light and variable on the lake through Monday afternoon. Flow turns southerly over Lake Erie by Monday night generally remaining between 5 and 10 knots. Deepening low pressure centered over the Great Plains will enter the Great Lakes region by mid week and will allow for southerly flow to increase to 15-20 knots during the day Wednesday before a cold front crosses eastward on Wednesday evening. Southwest flow of 10-15 knots behind the cold front continues into the end of the week. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. NY...None. MARINE...None. && $$ SYNOPSIS...Sullivan NEAR TERM...Garuckas/Sullivan SHORT TERM...Iverson LONG TERM...Iverson AVIATION...Garuckas MARINE...Iverson
Area Forecast Discussion
National Weather Service State College PA
1124 PM EDT Sat May 18 2024 .SYNOPSIS... An upper trough overhead will slide east through the late evening with showers decreasing by late tonight. High pressure will start to build into the region on Sunday accompanied by generally rain-free conditions that are expected to hold through the middle of next week. A storm system should arrive late Wednesday into Thursday bringing the next chance of showers and thunderstorms to the area. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Isolated open cellular showers continue to roam areas from the N Central Mountains to the WC Mountains late this evening as upper low upper low tracks off the coast and drier air works southward behind the upper trough axis. Showers will taper by late tonight with clearing skies and light winds allowing areas of fog to form overnight. Some fog could become locally dense in the predawn hours. Lows will range from the mid 50s to around 60. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY NIGHT/... High pressure rolls in for Sunday. Clouds/fog in the AM clear out nicely. However, just enough instability develops and enough moisture lingers to pop a couple of SHRA. Literally just a few with the highest probability (30pct) over the SErn hill tops. Maxes in the 70s will be pretty normal. We are likely to see some areas of fog again Sunday night with the sky clearing out better, but dewpoints not dipping out of the m50s. A decent and mostly rain-free stretch of weather is expected Monday through Wednesday morning, with high pressure dominating the sensible weather conditions and bringing the driest weather we`ve seen in a few weeks. We are timing the next weather system into central PA by Wednesday afternoon. Scattered showers and thunderstorms may approach western areas by late Wednesday afternoon, but it looks like most areas stay dry until after 00z Thurs. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... Late evening update holds minor changes to the long-term forecast, most notably have capped PoPs at Chc Wednesday evening into Thursday as both GFS/ECMWF models have showers/thunderstorms along the cold front breaking up as they enter central PA. Ensemble plumes still outline higher chances of PoPs in this timeframe so have decided to just cap instead of trim PoPs at this time. Prev... By the middle of next week, upper troughing will move across Pennsylvania and support a better chance for showers and thunderstorms. At the surface, there remains plenty of model uncertainty about the timing of a cold front. The mean timing is Wednesday afternoon, but individual models bring rain as late as Thursday morning. If the front moves through Wednesday afternoon or evening, it could produce the first threat for severe weather in some time given the aforementioned WAA bringing greater instability. After the front moves through, considerable uncertainty exists in terms of how much and how frequent rain will be. A chance of showers remains in place through the end of the week despite zonal flow aloft providing little in the way of synoptic forcing. The next chance for a widespread soaking rain will come during the weekend with a center of low pressure developing across the Ohio Valley by Friday afternoon. && .AVIATION /03Z SUNDAY THROUGH THURSDAY/... 03Z Update: Minimal changes outside of slightly later (1-2hr) later on fog development overnight with generally the same time for mixing out. A period of MVFR cigs possible tomorrow compared to earlier guidance but VFR expected by the afternoon hours. Prev... The main concern overnight will be fog formation at all airfields across central PA. The bulk of recent guidance outlines IFR conds in the 04-07Z timeframe, with most likely timing between 05-06Z where the potential for calm/light winds becomes slightly higher. This is echoed in recent RAP model soundings, thus have these restrictions in with moderate (50-60%) confidence. There is some uncertainty in regards to which airfields go down to 1/4SM vsbys and VV cigs after during the early morning hours Sunday morning. Highest confidence (40-50%) remains at AOO/UNV/IPT, with some potential for these conds at JST/BFD. Further to the SE, cannot rule out some lower- level clouds (below 300ft AGL) to bring LIFR conds to LNS with moderate (40-50%) confidence while retaining IFR conds at MDT based on a combination of RAP/GLAMP guidance. After sunrise, some lingering low cigs/vsbys remain possible through 14Z Sunday before rapid improvement (in a 1-2 hour period) towards VFR is expected by the late morning. Once conds prevail to VFR, expect these conditions to continue through 00Z Monday. Outlook... Mon...Patchy AM fog possible. Otherwise, becoming VFR. Tue...Predominantly VFR, w/ no sig wx expected. Wed...Sct to widespread SHRA/TSRA return. Thu...Chc of TSRA. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert/DeVoir NEAR TERM...DeVoir/Dangelo SHORT TERM...DeVoir/Dangelo LONG TERM...NPB/Bowen AVIATION...NPB
Area Forecast Discussion
National Weather Service Dodge City KS
1034 PM CDT Sat May 18 2024 ...Updated Aviation/Key Messages... .KEY MESSAGES... - Hot temperatures in the 90s and strong south winds are expected Sunday afternoon. - Scattered thunderstorms are expected Sunday afternoon and evening. Some storms are expected to be severe with large hail and damaging winds. - The highest risk of straight line wind damage will be east of Dodge City Sunday evening, where gusts of 60-80 mph are probable. && .SHORT TERM /THROUGH SUNDAY NIGHT/... Issued at 200 PM CDT Sat May 18 2024 18Z observations and upper air analysis shows a cold front located from central Kansas to around Liberal which is slowly progressing to the south and east. Winds behind the front have increased to 20-30 mph. A 1006 mb surface low is located in the Texas panhandle in association with an upper level shortwave while mid level winds are generally zonal. Tonight the main feature of interest is a forecast MCS to develop in northeast Colorado around sunset. Ahead of the storm complex a 700 mb shortwave and surface low will develop and the present cold front will lift back to the north as a warm front which should allow the return of more robust moisture as the winds switch back to the southeast. Through the evening and overnight hours BUFKIT soundings in northwest and northcentral Kansas show the storm will be quite elevated and the main threat would be downburst winds up to 60 mph and as a result there is a marginal risk of severe weather. These storms will likely affect areas along an north of a Syracuse to Hays line through sunrise Sunday morning. Sunday there should be a brief outflow boundary from the overnight convection which will stabilize the atmosphere through mid morning. Afterwards as the winds turn back to the southeast we will have growing moisture and instability ahead of a developing dryline along the Kansas-Colorado border. Mid level temperatures will be quite warm at 10-11(C) however with forecast highs reaching to the mid 90s around the dryline this should be warm enough to erode any cap we have. A 700 mb shortwave should move into the vicinity of the dryline around 20-21Z and thunderstorm initiation should quickly result around the Kansas/Colorado border. If we do have any supercells they will quickly evolve into a linear squall line within a couple hours. With short term models forecasting 3,000 J/kg or more CAPE these storms will have plenty of energy to work with as the progress eastward. Main threat for severe weather on Sunday will be straight line winds as the 12Z HRRR has hints of wind gusts approaching 75-80 kts once the line gets into the most robust moisture along and east of highway 183. Secondary threat with any squall line could be some brief QLCS spin up tornadoes embedded in the line. Hail threat will be the most with initial storm development and then lessen as the storms become more linear. The bulk of the line should be through by Sunday evening. Sunday evening as the main line of storms moves into central Kansas HRRR models hint at a secondary line of storms developing on an outflow/frontal boundary along K-96. If there is any instability left after the initial line this could certainly be a possibility. Storms look to fester between K-96 and I-70 through close to sunrise on Monday. && .LONG TERM /MONDAY THROUGH SATURDAY/... Issued at 205 PM CDT Sat May 18 2024 Monday medium range ensembles have a large longwave trough in the western CONUS and southwest winds at 700 mb will push a shortwave into western Kansas by 00Z. With how the track of the surface to 850 mb the majority of the rain and storms will be concentrated in northwest and north central Kansas into Nebraska. Tuesday into Wednesday the longwave trough will be concentrated in the northern plains with a strong cold front moving into Kansas Tuesday. High temperatures on Wednesday will be in the 70s. A warming trend will return towards the end of the week as highs get into the middle 80s. The more active part of the jet stream looks to be in the northern plains. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1034 PM CDT Sat May 18 2024 Outside of the influences of any convection, VFR is expected to continue through this TAF period. KDDC radar at 0330z showed strong thunderstorms near the CO/KS line well west of GCK. These storms are expected to track primarily north of GCK/HYS through 12z Sun, so kept any mention out of this set of TAFs. Light east winds will prevail overnight. After 15z Sun, south winds will increase quickly at all airports, gusting 30-35 kts. Scattered thunderstorms are expected to initiate on a dryline near US 83 (GCK-LBL) around 21z Sun, then rapidly spread eastward to impact DDC/HYS through 00z Mon. Using 00z ARW as a guide, only mentioned VCTS/CB for now, with the expectation that TEMPO groups will eventually be required, once the expected squall line is trackable on radar. Some thunderstorms Sunday are expected to be severe, with the primary risk to aviation being outflow wind gusts in excess of 50 kts. && .DDC WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Tatro LONG TERM...Tatro AVIATION...Turner
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1154 PM EDT Sat May 18 2024 .KEY MESSAGES... - Patchy fog, locally dense at times, will be possible tonight. - Warm and muggy conditions continue through early next week with daytime highs in the 80s. - Chance for showers and thunderstorms tomorrow afternoon and evening favored toward the lakeshores. Locally heavy rainfall and strong thunderstorm winds will be possible. && .AVIATION... Will maintain a mention of fog KYIP/KDTW/KDET within light southeast flow from Lake Erie, but will temper the degree of lower stratus as late evening satellite trends do not support much stratus at this point. Winds veer to the southwest and then west as a weak frontal boundary settles into the area. This front, combined with a number of lake breeze boundary, will be the focus for widely scattered to scattered showers/thunderstorms late in the day, mainly KPTK south. Wind will shift to northeast tomorrow night behind the front and then basically become light/variable. For DTW/D21 Convection...There will be a chance for scattered thunderstorms Sunday afternoon as a weak frontal boundary interacts with lake breeze(s) serving as the focus. Isolated heavy downpours may bring visibility restrictions. DTW THRESHOLD PROBABILITIES... * Low for ceilings aob 5kft late tonight. * Low for thunderstorms Sunday afternoon. && .PREV DISCUSSION... Issued at 423 PM EDT Sat May 18 2024 DISCUSSION... Lower clouds supported by lake moisture under the strong inversion this morning has mixed out this afternoon bringing mostly clear skies. Warm and muggy airmass in place today. The 12Z DTX RAOB came in with 925mb temperatures in the mid teens (C). This is supporting the temperatures into the 80s this afternoon. Daytime heating and low level moisture has brought a scattered field cumulus, but high pressure and ridging should largely limit any shower activity with instability lacking and very weak forcing. Higher dewpoints, southeast flow off Lake Erie, and mostly clear skies will bring potential for patchy fog development again tonight. An unstable airmass residing across Michigan tomorrow will set the stage for scattered shower and thunderstorm potential. The RAP offers 1000-1500 J/kg of MLCAPE developing by 18Z tomorrow across much of southeast Michigan with increased mid level lapse rates of 6.5-7.0 C/km and low level lapse rates to around 9 C/km. A northern stream shortwave will drive a weakening cold front into southeast Michigan tomorrow. Shear over much of the area will be weak though with best flow off to the north. Bulk shear from 0-6 km is mostly below 20 knots with the exception across portions of the Tri-Cities and Thumb. The northern stream shortwave will push a weakening cold front into southeast Michigan during the late morning/early afternoon while stronger surface heating will likely lead to the development of multiple lake breezes during the afternoon. This brings several opportunities for surface convergence to force convection initiation, especially if the front tracks further into southeast Michigan and meets up with any lake breeze. The weaker flow leads to mainly a pulse type thunderstorm mode that form initially on either of the aforementioned boundaries with thunderstorm outflow also driving additional updrafts. Current Hi- res model suite wants to place greater probability for initiation across Port Huron to the Detroit Metro area and down to Monroe County along the lake breezes. Though, some capping in the forecast soundings could also put a damper on some thunderstorm development. Will maintain the chance PoPs in the forecast here. Main threats with activity will be strong downburst winds, hail, and brief heavy rainfall with the PWATs of 1.25" to 1.35". Heavy rainfall and slow storm motions bring some potential for localized flooding of prone spots, especially in the urban footprint in and around Detroit for any areas that experience a longer duration of thunderstorm activity. Shower and thunderstorm activity will weaken and eventually come to an end in the evening with the loss of instability. The next shortwave lifts out of the central plains and through the southwest flow between the Canadian troughing and the ridging through the Appalachian Mountains. A weak surface reflection is forecast to travel across WI and northern Lake Michigan. A plume of theta-e will support scattered showers and thunderstorms with a boost in larger scale ascent from the shortwave. Greater forcing and placement of the higher moisture axis puts higher PoPs towards the Tri-Cities. Active stretch of weather remains as the above normal temperatures and moist airmass remain over Michigan into the middle of the week helping field additional showers and thunderstorms. Long range models are mostly in agreement with a Tuesday night into Wednesday system as shortwave energy originating off the Baja Coast shoots northeast within the flow of the southern and northern stream jets. Frontal timing will ultimately decide severe weather potential mid-week. The well above normal temperatures with daytime highs in the 80s will carry continue Sunday through Tuesday with overnight lows in the upper 50s to mid 60s. Cooler temperatures will arrive behind frontal system mid-week bringing highs back down into the 70 degree range for the late week period. MARINE... High pressure dominates local conditions this weekend with light southeasterly winds generally 10 knots or below through the rest of today, veering south tonight. Very warm and humid air in place keeps areas of fog across marine areas, with potential for dense fog to redevelop tonight. Will continue to monitor observations and reissue a marine Dense Fog Advisory if/where conditions warrant. Models do show a slightly stronger gradient picking up overnight which may disperse any more dense fog before sunrise Sunday. A weak cold front moves into the region on Sunday with a few showers and storms possible, mainly in the nearshore waters. An area of low pressure then tracks in from the Midwest late Monday into Tuesday, bringing the next likelihood for showers and storms. Winds and waves are expected to remain below Small Craft Advisory criteria outside of any localized higher winds within any thunderstorms. HYDROLOGY... Scattered to numerous showers and thunderstorms are possible, mainly tomorrow afternoon and evening with favored areas along the lake breezes across Port Huron through Metro Detroit to Monroe County. Locally intense rainfall rates are possible with any thunderstorms that can develop with the high moisture environment. Forecast average rainfall amounts are a quarter to half inch with locally higher amounts of 1 inch or more possible. Several areas may remain dry, but the slow moving nature of the scattered thunderstorms will bring potential for these localized higher rainfall totals. Main concern would be for localized flooding of prone urban areas across the Detroit Metro if any of these thunderstorms develop and linger over parts of the metro region. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....DG DISCUSSION...AA MARINE.......TF HYDROLOGY....AA You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Quad Cities IA IL
707 PM CDT Sat May 18 2024 .KEY MESSAGES... - Scattered showers and storms will wane after sunset tonight. There is a Marginal risk (level 1 of 5) of severe weather today west of the Mississippi River. - Boundary stalls south of the area as temperatures again reach well into the 80s as chances for thunderstorms return late. - Active pattern through the long term with chances of strong to severe storms through Tuesday. Tuesday is the best day for severe weather in the next 5 days. && .UPDATE... Issued at 705 PM CDT Sat May 18 2024 Cold front approaching the nw part of the forecast area had briefly flared up a few thunderstorms along the front, but since then they have weakened rapidly. The bulk of the thunderstorms, some severe, have been across Wisconsin and western Upper MI where the stronger shear/forcing exists. In our forecast area, the SPC mesoanalysis showed weak shear (<20 kt) along with weak forcing, while the SBCAPE was about 1500 J/kg. In addition, the 00z/19 DVN sounding showed a decent capping inversion above 800 mb. Being that we are past peak heating it appears that the threat for any severe storms has diminished. However, still can`t rule out an isolated storm or two this evening until the front moves through. && .SHORT TERM /THROUGH TONIGHT/... Issued at 109 PM CDT Sat May 18 2024 Temperatures well into the 80s today were found area-wide. Dewpoints in the upper 50s to low 60s made it feel somewhat nicer than the middle of July. To the west of the area, a cold front was located across the center of Iowa. A shortwave passing north of the area today will drag this front through the area this afternoon and into the evening. The boundary will then stall out across southern portions of the area. This boundary on Sunday will separate the higher moisture air from the drier air. Nonetheless, we will see highs again in the 80s, but with drier air than today. With that boundary in place across the south, we could see some thunderstorms redevelop along the front later in the day and move east towards us late. Most of the impactful weather will likely be ongoing at 00z tonight as the cold front moves through the area. Guidance has CAPE building ahead of the front to around 2000 J/kg this afternoon. Shear looks very weak, so updraft organization is not expected. Pulse like storms are expected if they develop. The main question today is forcing. The main upper level forcing is way north, so the front and daytime heating will be the main drivers for thunderstorm development. CAMs have either a broken line of storms or not much with the exception of the highway 20 corridor. Dprog/Dt of the HRRR shows run to run variability with some having convection down to highway 30 the rest further north. The NAMnest has convection all the way through the CWA. Think the best chance for storms is highway 20 north. In a nod to the NAMnest, did keep schc south through I80. Am not too big on severe today. Could see near severe wind gusts and hail, especially due to the steeper lapse rates, but don`t expect cells to have much longevity to really get going. && .LONG TERM /SUNDAY THROUGH SATURDAY/... Issued at 251 PM CDT Sat May 18 2024 Extremely active pattern with a mid-summer like pattern is expected to last through most of the period as a stalled out boundary resides just south of the CWA. This boundary will separate the area between Tds in the 50s, to the more robust deep moist Tds in the 60s and 70s to the south. A series of weak waves and possibly MCVs/convective induced waves/ move over the boundary later Sunday into Monday evening. A strong wave, with better shear is expected to approach the area into Tuesday. A deepening surface low with this wave will help to bring this boundary north as a warm front Tuesday. This will bring higher Tds into the area ahead of the wave and increased shear. Then the boundary is sent south again as a cold front later Tuesday. After this point, there are questions about where the boundary will be and additional chances for thunderstorms. Closer look at the guidance for Sunday evening suggests a MCV rolling into the area after 00z. The 12Z HRRR has convection firing with this wave like feature across the area. In fact, the HRRR suggests some of these storms could be supercellular in nature. As mentioned before, shear looks to be weak, however, if this truly is a MCV, then the shear may actually be stronger than forecast. With Tds lower tomorrow, think that these supercells would be hailers and possibly HP in nature and a wind threat. That said, other guidance keeps us clear. We will need to keep an eye on convection upstream to see if this forms. So there is a conditional risk for severe weather tomorrow afternoon and evening. Monday, another possible day with severe weather as the wave induces height falls and the sfc boundary moving north again. The NAMnest depicts yet another MCV moving through our area Monday with redevelopment of showers and storms in the afternoon. This is yet another potential case where we could see higher shear than forecast. With clouds possibly keeping Ts lower, our T/Td spread may be lower as well. Llvl winds looked back so if we develop afternoon showers and storms monday they could be severe as well. We currently have a mrgl for this day as well, but could see this day updated to a slight if the MCV comes true. So after the next two days with conditional severe weather outlooks we get to Tuesday when a better wave makes its way into the area. This one will bring better shear into the area Tuesday. Storm Mode: 0-6km shear vectors are perpendicular to the forcing and around 40kts. This would suggest supercells and they will likely form first west of the CWA. However, upper level flow is weak so expect convection to quickly become cold pool dominated. Expect a mature/ing bow to enter the area in late afternoon. Severe Hazards: 0-3km shear vectors of 40kts will help the production of mesovorts with localized higher wind gusts and possible tornadoes. The LLJ is impressive for the afternoon, and even more so after sunset, so this thing could really ramp up later in the evening. With weak upper-level flow, the overall system should not be moving all that fast. Some hail is possible early on, but think this is rain/strong wind/tornado event. Heavy Rain: In addition, some heavy rainfall will be possible with this event, with PWs around 1.5 to 1.7 inches, which would be above the 90th percentile for this time of year. Wednesday On...additional showers and storms will be possible late week. However, model timing differences in shortwaves moving through the flow precludes changing the PoPs, which are in the 15 to 30 percent range for each 6 hr period through Friday. There will be some dry hours, but when this will occur is still in question. Temperatures will return to more seasonable values by late week, with highs in the 70s and lows in the 40s. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 705 PM CDT Sat May 18 2024 VFR conds through this taf cycle. An isolated shower or storm is still possible along a cold front, but coverage too low to mention in the TAFs. Winds will turn northwest overnight then become northeast to east on Sunday. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...None. IL...None. MO...None. && $$ UPDATE...Haase SHORT TERM...Gibbs LONG TERM...Gibbs AVIATION...Haase
Area Forecast Discussion
National Weather Service Kansas City/Pleasant Hill MO
631 PM CDT Sat May 18 2024 .KEY MESSAGES... - A few brief, isolated storms remain possible this evening. - Active Pattern Sunday Night through Tuesday Night. Severe thunderstorms possible each day. - High temperatures well into the 80s, around 10 degrees above normal, through Tuesday. && .DISCUSSION... Issued at 254 PM CDT Sat May 18 2024 19Z surface analysis reveals a modest surface trough stretched from northern Iowa southwest through northwest Missouri into Kansas. Behind the surface boundary, winds are gusting around 20 to 25 mph. Visible satellite reveals some minor cu development in southwest Iowa toward S. Joe and into northeast Kansas. The latest runs of the HRRR have been less bullish with convective development along this boundary as it advances toward the KC Metro and lower Missouri Valley through the late afternoon and early evening. Forecast soundings suggest a rather deep, 5 to 6kft, mixing layer and rather weak wind profiles. Elevated instability will be sufficient, but given the lack of supportive shear, organized updrafts are looking difficult to come by. Regardless, will keep a low PoP mention going through the evening, with the best window between 5 and 8 PM CDT. If any one updraft can tap into the 1000 to 1500 J/Kg MLCAPE, an isolated bout of severe hail or wind cannot be ruled out. Positively tilted mid-level ridging will continue to strengthen aloft across the region through Sunday morning. Overnight tonight, a complex of thunderstorms is expected to develop with support from a weak, open, H500 short wave trough traversing the larger flow pattern along the northern Kansas and southern Nebraska. Through sunrise, whatever remains of this activity will slide begin to slide across northwestern Missouri and continue east through the day along the MO/IA border. Most precipitation chances will exist along and north of the US-36 corridor during the day. South of this activity, modest return flow will persist ahead of a developing surface trough over the western High Plains. Low to mid 60s surface dew points will develop through the late afternoon. Convection is forecast to fire in central Kansas by mid-afternoon near the triple point, with convection growing upscale into a line or broken line of storms as it moves into far eastern Kansas and western Missouri by late in the evening. Some of this line may be strong to severe as it arrives with damaging winds and hail and flash flooding the primary concerns. Storms are expected to lower in intensity as they move east through early Monday morning, with localized flooding a lingering concern. Monday, lingering showers and thunder may be ongoing across portions of the area, likely ending through midday. At the same time, a long wave trough will strengthen across the western CONUS, with another surface trough developing over the western High Plains of CO/KS. With better access to return flow and a more robust synoptic pattern setting up to the west, recovery is expected in the wake of any lingering precipitation in the morning. The good news for now is that the better focus forcing looks to be in western Nebraska to central Kansas, nearer the low center and focused along the warm front, which the latest mid-range guidance has a bit farther north. However, as the low level jet increases through the evening and the region well within the warm sector, some organized convection is expected and could result in some strong to severe updrafts. Tuesday could be the more significant day for severe convection across the region. It goes without saying, but any morning precipitation would influence recovery, but with a more negative tilt to the H500 shortwave trough ejecting across Nebraska in the morning, strong WAA will persist, with ample recovery more than likely ahead of the surface trough as it pushes east into the afternoon. With steep mid-level lapse rates and surface dew points nearing 70 F, MLCAPE between 1500 and 2500 is possible. However, forecast soundings through the afternoon from the NAM suggest a sizable capping inversion and given 700mb southwest flow, it`s likely the inversion will hold off initiation until the arrival of the surface front. Latest guidance has the line lighting up around 00Z from northwest Missouri southward toward the KC Metro. Timing of the boundaries arrival will be key and a primary forecast focus as step through the next two days. 0-6km shear orientation suggests initial convection would be isolated, supercellular in nature, but quickly developing into a line as the surface front surges south- southeast through the evening. Damaging winds and hail and a tornado or two cannot be ruled out with storms Tuesday evening/night. Precipitation will clear out through Wednesday with surface ridging briefly holding on before another trough arrives into Friday from the west. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 623 PM CDT Sat May 18 2024 A cold front is currently draped across NW Missouri and into NE Kansas, but so far only a few small and brief showers have formed along the front. The terminals will likely remain clear of any showers or storms, but if anything does get going in the area it would be between now and around 2z. Winds will turn northwesterly and then northerly behind the front tonight, with winds turning southerly by tomorrow morning as the boundary lifts back to the north. VFR conditions are expected through the period. && .EAX WATCHES/WARNINGS/ADVISORIES... MO...None. KS...None. && $$ DISCUSSION...Kurtz AVIATION...BMW
Area Forecast Discussion
National Weather Service Hastings NE
635 PM CDT Sat May 18 2024 .KEY MESSAGES... - Scattered showers and thunderstorms move in late tonight and continue into Sun AM. Most likely non-severe, but small hail and gusty winds will be possible in strongest cores. - Off and on thunderstorms are expected Sun PM through Tue, some of which could be strong to severe and pose risks for all severe hazards. However, confidence on details is only low to medium as each round will have significant impact on subsequent rounds` severity, timing, and placement. - Cold front sweeps through the area and brings somewhat cooler and less active weather for Tue night into Thu. - Temperatures most days will peak in the 70s-80s, though mainly mid 60s-70s are expected Tue-Wed. Lows will be mainly 50s- 60s, except for cooler 40s Tue/Wed nights. && .DISCUSSION... Issued at 208 PM CDT Sat May 18 2024 Expect increasingly pleasant conditions late this aftn and into the evening as wind speeds gradually decr and temps remain mild. Short term CAMs are in pretty good agreement that elevated convection will develop over the central High Plains 03-06Z as 45kt LLJ noses into the region, then shift E/NE into our area 06-09Z. Peak MUCAPE will increase to around 1500-2000 J/kg for parcels lifted from H7-H8 amidst steep mid level lapse rates. However, the bulk of the veering in the wind profile is below the MUCAPE layer, so effective shear is rather marginal at mainly 25-30kt. This could yield some "pulsey" elevated hailers, generally of the low-end variety (penny to half dollar size), and perhaps some gusty winds around 40-50 MPH. Recent HRRR runs and HREF seem to focus the majority of the activity along and S of the Platte River, which is a bit of southward shift from where previous forecast placed the highest PoPs. Seems probable (60- 70%) that at least scattered activity will persist into the mid to late AM hrs Sunday as the LLJ slowly veers and weakens, though the lingering activity will probably have a lesser hail risk. Pattern recognition and general model guidance would suggest a dry period, or at least a lull in coverage/intensity, from around midday Sunday through AT LEAST mid aftn. Thereafter, details for additional convection become quite a bit more murky owing to uncertainties left by the earlier round, such as location of outflow boundaries, cloud cover that will affect ability to destabilize, and quality/depth of BL moisture. The overall upper pattern will feature only modest height falls, but most guidance has several weak disturbances in moderately fast SWrly mid-upper flow, and the AM round may actually help to suppress the strongest mid level capping to our S. As it stands now, there appears to be two scenarios of convective potential: 1) Seems plausible that enough recovery will occur to allow for a narrow window of sfc based development along lingering outflow boundary that will probably be located somewhere between the NE/KS border and I-70 corridor around 22Z-02Z. After that, cooling BL will probably become capped along this boundary in the absence of stronger forcing. It is a highly conditional, and probably isolated, threat...but if something does pop up, it will likely be supercellular with all modes of severe possible - including tornadoes - given tendency for backed low level flow and perhaps some pooling moisture. Worth noting, however, that forecast soundings suggest moisture quality/depth will not be great during the late aftn/early eve period and subject to mixing out - so would really need some pooling and backed flow to get low enough LCLs for tors. Greatest risk would likely be large to very large hail given very steep mid level lapse rates and bulk shear values of 40-50kt in the presence of clockwise curved hodographs, along with damaging wind gusts. 2) The other scenario - which is more probable and likely more impactful because of coverage - will be for tstms to develop along a N-S corridor along the High Plains from the NE Panhandle southward to TX/OK Panhandles within warm/hot, deeply mixed environment with little to no capping and beneath slightly stronger height falls. This activity would have a tendency to become outflow dominate given inverted-V thermodynamic profiles and more forward propagating due straighter hodographs. Since it`s developing further W, this threat would likely be a bit later, generally after 00Z, but severe will still be a risk as this activity will actually be moving into pool of greater instability, and LLJ again increases to 40-50+kt. Would tend to favor W/S zones the most, but if a mature MCV develops then local dynamical forcing could overcome incr capping after 03Z to persist the severe threat longer and further E. Heavy rain is not a concern attm given isolated/conditional nature of scenario 1, and likely progressive nature of scenario 2. Thunderstorms remain possible into Monday, and the entire area is outlooked in either a Marginal or Slight Risk of severe weather (levels 1 and 2 on a scale of 5) on SPC Day 3 outlook. As there are uncertainties on Sun due to earlier convection, the uncertainties are even higher on Monday. In general, upper troughing still resides to the W and we`ll remain in diffluent (but kinda weak) SWrly upper flow. At least one or two upper waves will likely be ejecting NE out of the broader trough, which could enhance the upper flow late in the day and moreso into Mon night. Sfc mass fields suggest a triple point over central KS, with previous outflow boundaries possibly augmenting and/or narrowing the primary instability axis to the E of this triple point and southward trailing dry line. I have a tendency to doubt we`ll have much sfc-based activity in our CWA prior to sunset as mid level temps appear to be 1-2 deg warmer, though mesoscale details will be important. Would think the later arrival of upper support would favor activity moving off the High Plains after sunset and/or new development ahead of possible northward moving warm front in response to incr LLJ. This would provide more of a wind/hail threat and lesser of a tornado threat, but again, plenty of details to work out. Trough moves through on Tuesday, and timing will be key for severe weather chances in our area. At this time, appears it will be just fast enough to keep primary risk to our E/SE, but any slowing trend and our chcs will incr. Continued cloud cover and shwr chcs behind departing system amidst NWrly low level flow will likely keep temps considerably colder in the 60s, esp N/W of the Tri-Cities. Flow turns more zonal late in the week and into the start of the holiday weekend, which should support seasonable temperatures and off and on pcpn chances. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 625 PM CDT Sat May 18 2024 A cluster of showers and thunderstorms is expected to move through central Nebraska early Sunday morning, with near-term models showing additional scattered showers and storms redevelop later Sunday morning. In addition to the thunderstorms, ceilings could dip to MVFR Sunday morning. The probability for this occurring is a bit higher at EAR compared to GRI. Another round of stronger thunderstorms is possible Sunday evening, just beyond this TAF period. && .GID WATCHES/WARNINGS/ADVISORIES... NE...None. KS...None. && $$ DISCUSSION...Thies AVIATION...Mangels
Area Forecast Discussion
National Weather Service Goodland KS
516 PM MDT Sat May 18 2024 .KEY MESSAGES... - Thunderstorms will progress eastward from CO into western KS late this evening and overnight. A few severe storms are possible, mainly between ~7 PM and ~3 AM MDT. - Severe storms capable of producing very large hail and damaging winds are possible in northwest KS and southwest NE Sunday afternoon, mainly between 3-9 pm MDT / 4-10 pm CDT. Latest guidance suggests that the severe weather threat in the Goodland CWA will be isolated in nature (i.e. not widespread). Thunderstorm coverage and severe weather potential increases with eastern extent into central KS. In other words, locations along/east of Highway 283 appear to be most at-risk. - Cooler with frost concerns mid week. - Active weather may return next weekend (Memorial Day Weekend) && .SHORT TERM /THROUGH SUNDAY NIGHT/... Issued at 245 PM MDT Sat May 18 2024 Through Noon on Sunday: Southern stream shortwave energy presently located invof the southern CA/AZ border will track ENE across the 4-Corners and central Rockies (tonight) and adjacent portions of the High Plains (Sunday morning). Current and recent runs of the HRRR and NAM NEST suggest that scattered diurnal convection developing along the Palmer Divide this afternoon will progress eastward to the CO/KS border this evening.. continuing eastward across northwest KS overnight. Guidance suggests that convection will increase in both coverage and intensity this evening and overnight.. aided and assisted (presumably) by DPVA attendant the aforementioned shortwave energy (approaching from the SW-WSW) and strengthening low-level (SFC-H85) warm advection over western KS.. when modest (albeit increasing) airmass destabilization and strengthening deep layer shear appear supportive of severe weather.. especially if forcing is favorably/further augmented by convection itself (e.g. an MCV).. mainly in the 03-09 UTC time frame. Wind gusts up to 65 mph, quarter size hail and torrential rainfall appear to be the primary hazards. Sun PM-Sun night: Challenging forecast. Early morning convection may significantly alter environmental conditions over the Tri-State area during the day on Sunday, esp. in a pattern characterized by a rather weak/broad/ill-consolidated lee cyclone in southeast CO. Latest available guidance indicates a scenario characterized by little/low convective coverage over northwest KS and southwest NE Sunday afternoon, suggesting that severe weather in the Goodland CWA may be isolated in nature (i.e. not widespread).. and largely confined to the 21-03 UTC time frame. Very large hail and damaging winds appear to be the primary hazard(s). Broadly speaking, guidance continues to indicate that convective coverage and severe weather potential increases with eastern extent into central KS. In other words, locations along/east of Highway 283 appear to be most at-risk. && .LONG TERM /MONDAY THROUGH SATURDAY/... Issued at 140 PM MDT Sat May 18 2024 The latest from the GFS/ECMWF continues to show potential for rainfall/storms to impact mainly the northern portion of the CWA from late Monday on into the end of next week. With a blocking upper ridge over the eastern portion of the country through the midweek timeframe, a strong trough will swing east out of the north central Rockies late Monday, making a slow trek eastward due to the blocking effects of the eastern ridge. This system will eventually lift northeast along the western periphery of the block. This will be followed by a second shortwave taking a similar track although a bit more easterly as guidance breaks down the ridge for the latter portion of the week. Another amplified ridge build into the Plains region for Thursday, shifting east to end the week. This will be ahead of an elongated trough stretching through the northern/central Rockies. At the surface, low pressure sets up across southern Kansas late Monday into Tuesday, lifting northeast with an associated front. The position/track of this low will allow for a moist, easterly upslope flow from the surface to 850mb and eventually going northerly by Tuesday as the low lifts east. A similar setup will occur late Tuesday into Wednesday for the second system, although a bit further south based on both the GFS/ECMWF. High pressure traverses the CWA Thursday/Thursday night, with southerly flow setting up increased warmth/moisture ahead of the end-of-week upper system. A surface low does work off the Front Range in tandem with the upper system. As a result, the main wx concerns are going to focus on the potential for showers and storms. QPF/track through midweek puts the best chances for rain north of the Interstate, especially along/north of Highway 36. For Fri/Sat, the coverage is ahead of the low/front that moves off the Front Range, but for areas closest to the surface low. The chances for storms will be focus mainly for the Mon-Tue timeframe with the passage of the aforementioned shortwaves. The end of week system does differ with timing/placement of storms/QPF, but these could be problematic. Decent instability along with increasing PW values from west to east on Mon-Tue, will afford the potential for strong to severe storms, especially Monday. SPC currently has a Marginal risk for most locales east of the Colorado border. The surface low passages to the south will bring in PW values of an inch plus, especially east of Highway 83 which is closest to the surface trough/front that extends into central Kansas. So, besides a hail/wind threat, heavy rainfall/flooding potential will also be high. Monday looks to be the main focus, with WPC having a Marginal risk area out for locales north of highway 36 Mon night-Tue. Please refer to the Hydro section below for more details. The passage of the second system Tuesday night into Wednesday will bring about some cooler/colder air into western locales. Areas in Colorado could see some frost potential, but will be highly dependent on the extent of clearing from the exiting system. Right now, western portions of Kit Carson/Cheyenne counties are most prone. For temps, with a cold front settling through the region during the first portion of next week, looking for a downtrend in daytime highs before rebounding for the latter portion of the week. On Monday, mid 70s north through the mid 80s south are expected. A wide range for Tuesday with mainly 60s north of the Interstate and 70s south will give way to lower and mid 70s area-wide for Wednesday. 80s Thursday drops to the mid 70s through the lower 80s to end off the week. Lows during this time will mainly range from the mid 40s west through the lower and mid 50s east. Tuesday night will be the coldest, with lower to mid 40s east of the Colorado border, with upper 30s to around 40F for northeast Colorado. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 500 PM MDT Sat May 18 2024 For KGLD... A mix of VFR and IFR conditions are forecast along with chances for thunderstorms through the period. A line of storms was entering western Kit Carson county as of 23Z. Currently expecting these storms to progress and move through the terminal around 0130Z. They currently are moving slowly and if they don`t speed up as forecast, then it would move in around 4Z. When the line passes, VFR conditions are forecast for a few hours until moisture advection and cooling temperatures saturated the lowest 1000ft around 09Z. Unless additional storms form, the lower ceilings should break a few hours after sunrise and allow for VFR conditions. Storms are then possible again around the last 3 hours of the period. Currently, the storms are forecast to form near, but not over the terminal tomorrow afternoon, look for updates. For KMCK... VFR to MVFR ceilings are forecast at times through the period, but the main concern will be storms and rain. Currently expecting a line of storms around the Western Yuma county line (as of 23Z) to move east through the evening. Based on current forecast and timing, the storms and rain should move over the terminal around 04Z. The main uncertainty is whether storms will redevelop near the terminal through the night due to an MCV/low, or if the storms will progress and leave the terminal. Once the storms end, stratus clouds are forecast to develop around 1000-1500ft. There is a 20% chance that the cloud layer could be below 1000ft. By around noon, ceilings should lift and VFR conditions are expected for the afternoon. && .HYDROLOGY... Issued at 226 AM MDT Sat May 18 2024 Some potential does exist for torrential rainfall and isolated flash flooding starting Saturday night/Sunday morning into early portions of the new work week. The majority of the area, especially western and southern portions have seen a lack of rainfall in recent weeks and worsening drought conditions. Overall main concern for any hydro issues lies to the east of Highway 83 in Kansas where portions of Gove county for example received 1-3 inches of rainfall earlier in the week. PWATS will rapidly increase tonight around 1.25 inches and remain above 1 inch for the duration of the weekend. Overall widespread flooding potential is relatively low as overall systems should be fairly quick moving with fast Corfidi Vectors. The overall main concern for any hydro related issues lies in multiple rounds of heavy rainfall and any potential training locales. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...None. CO...None. NE...None. && $$ SHORT TERM...BV LONG TERM...JN AVIATION...KAK HYDROLOGY...Trigg
Area Forecast Discussion
National Weather Service Grand Rapids MI
1039 PM EDT Sat May 18 2024 .KEY MESSAGES... - Warm Weekend Continues - Unsettled Weather at Times Monday through Wednesday - Drier and cooler Thursday and Friday && .UPDATE... Issued at 1038 PM EDT Sat May 18 2024 Cold front is moving east through Wisconsin at 1030pm and can clearly be seen in regional radar loops. Convection on the front has trended down (fading diurnally), but it has not come to an end. There is enough instability on the front that storms continue. MUCAPE values at present are on the order of 1000-2000 j/kg in Wisconsin. The front makes steady progress eastward tonight and moves through much of the forecast area between midnight and 800am. The 3km NAM shows MUCAPE values remaining around 1,000 j/kg through the night in Southwest Lower Michigan. Consensus of short term models suggest we need an isolated/scattered chance (20-30 pct) for showers and storms through the night. Most places will likely not see any precipitation but the front is strong enough and instability great enough to warrant the chance. The HREF that is now coming in suggests an uptick in showers and storms near and after 500am. It will be a warm night with lows in the lower 60s in many areas. The normal low at GRR tonight is 50. && .DISCUSSION... Issued at 258 PM EDT Sat May 18 2024 - Warm Weekend Continues "Cold" front over Wisconsin slips our way tonight but it is really nothing more than a wind shift line. High temps will actually be similar or even a few degrees warmer on Sunday despite its passage. A band of showers and thunderstorms along the front in WI weakens considerably as it drifts southeast and arrives in our area later tonight, and may even dissipate completely before getting here. Will maintain 20-30 pops toward/after midnight for areas north/west of GRR but latest CAMs look to be decreasing the threat of convection since the shortwave stays well northwest of us over the Lk Superior region and instability wanes quickly. A few showers and storms may redevelop by Noon Sunday south and east of GRR where the frontal boundary stalls out and sfc instability rebuilds. RAP has SBCapes rising to near 2000 J/KG where sfc dew pts near 60 will be present along with some weak sfc convergence. Pops only 20-40 pct again (highest near JXN), and any storms will be the pop-up/pulse-variety in weakly sheared environment. Any diurnal showers/storms will dissipate with sunset although returning warm front late Sunday night could touch off a few storms again by daybreak Monday. - Unsettled Weather at Times Monday through Wednesday The ridge that will be over the area on Sunday will slip east of the area by Monday. This occurs as a long wave trough will dig and amplify across the western half of the country. Our area will end up under deep flow from the SSW which usually results in a warm and humid/wet period. This period looks about as expected with periods of showers/storms, although it will not be raining all of the time by any means. The first chance of rain will come as early as Monday as the leading short wave ejecting from the long wave trough skirts by to our NW. Ahead of this wave, we will see a surge of warm and moist air ahead of it with a low level jet. Showers and storms look like a decent bet into Monday night before that wave moves away from the area. We are expecting another more significant wave to lift NE around the long wave trough in the Tue/Wed time frame. A front will remain over the southern half of the area behind the Mon system, and will then move back north as a warm front on Tue ahead of the stronger wave. This will bring additional chances of showers/storms. This system is the center of the SPC DY4 outlook that clips the area. It appears that the main threat may stay SW of the area with the entire system wrapping up a bit to the west. We will remain out ahead of the cold front on Wednesday, leaving the area in the warm sector for at least a part of the day. Getting out that far, details are a bit gray. Timing of features with this system with respect to peak heating as late as Wed may ultimately determine the severe weather threat. The potential does exist with some strong wind fields aloft and plenty of warm and humid conditions present. - Drier and cooler Thursday and Friday It does look like the front should sweep out the heat and humidity by late Wednesday, leaving a mild and drier air mass in it`s wake. The instability and showery weather with the cold pool aloft should stay north, while the front moves SE of the area. This leaves some ridging in place, and it looks likely to stay dry through at least Friday. There remains some small chances of rain in the NBM, but we are thinking it is more likely to stay dry. Rain chances will increase some by Saturday, but nothing significant is on the horizon yet for the beginning of the upcoming holiday weekend. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 747 PM EDT Sat May 18 2024 VFR prevails across the area with clear skies. Expect continued VFR through the forecast period with no major forecast concerns to note. Wind will be primarily southerly through much of this evening and early overnight, then a dry front will pass through resulting in a wind shift to the northwest between 06 and 12z Sunday. A line of 5 to 7k ft clouds will accompany the front then clouds will scatter out after sunrise. Diurnal cumulus is expected to develop tomorrow afternoon. && .MARINE... Issued at 258 PM EDT Sat May 18 2024 Winds and waves remaining below advisory levels through the remainder of the weekend, although a frontal boundary slipping through tonight will shift the winds from southerly this afternoon and tonight to northwesterly on Sunday. There may be a period Sunday afternoon where the NNW winds increase to near 15 kts or so for a time. The fog threat appears to have ended over the lake. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Air Quality Alert until midnight EDT tonight for MIZ050-056-057- 064-071. MARINE...None. && $$ UPDATE...Duke DISCUSSION...Meade/NJJ AVIATION...Thielke MARINE...Meade
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
952 PM CDT Sat May 18 2024 ...New MESOSCALE UPDATE... .MESOSCALE UPDATE... Issued at 943 PM CDT Sat May 18 2024 The potential for any severe storms in our CWA has ended and the probability of any measurable rain was coming to an end as well. Local radars had a few very light showers over eastern Clarke county and back to the west across southern Scott county. These light showers were along a nearly diffuse cold front that will continue to sag south of Interstate 20 and near Highway 84 the remainder of tonight. Some patchy fog may develop across our southeast as a result. /22/ && .DISCUSSION... Issued at 242 PM CDT Sat May 18 2024 The rest of today through tomorrow: Radar imagery shows mostly showers and some storms developing in the Golden Triangle Region this afternoon. A boundary associated with a low pressure moving eastwards across the MS/AL line is enabling storm development and will continue through the late afternoon. RAP mesoanalysis shows an estimated 2000 - 3000 J/kg of SBCAPE and low level lapse rates between 6.5 -7 C/km, which has allowed for some strong shallow updrafts to develop so far this afternoon. Mid-level lapse rates continue to be lackluster, which will make it difficult for any deep cores to develop through the remainder of the evening. Despite this, a Marginal Risk (1/5) will continue through the late evening with the main risks being isolated severe storms with hail up to quarter size and damaging wind gusts up to 60 mph. By tonight, rain chances are expected to diminish and maintain a dry overnight period. in the southeast, lingering moisture is expected to generate some patchy fog across the Pine Belt, but diminish by daybreak. On Sunday, drier conditions look to prevail as an upper trough ejects out of the Southeast region onto the eastern coast. Deep ridging will begin to build into the Lower Mississippi Valley, allowing for temperatures to increase and cloud cover to dissipate. Sunday highs look to be in the upper 80s to near 90, with mostly sunny skies across the region. /AJ/ Next week... Early-midweek (Monday-Wednesday): As the mid-level ridge amplifies over the Bay of Campeche & Mexico, the low-level ridge axis is progged to build across the area through mid-week. Sfc high pressure is progged to build across the region, with an active upper level jet ejecting across the Central Plains. This will drive a strong low pressure system out of the Plains into the Mid West to Great Lakes. A dry pattern is progged to persist through early week, with increased warm advection/low-level temps into the upper teens to low 20s degree C at 850-925mb layers. Expect highs to moderate to seasonably warm into the low 90s & lows in the upper 60s southeast of the Natchez Trace to low 70s to the northwest. Heat & humidity will be on the rise around midweek with heat indices climbing into mid-upper 90s, but heat stress shouldn`t be much of an issue. Low- level return flow won`t pick back up until by midday Tuesday through midweek, with rain & storm chances picking back up around late Wednesday aftn to evening, mainly northwest of the Natchez Trace. Late week (Thursday-Friday): As the trough swings into the Great Lakes to Hudson Bay, expect the ridge axis to relax & gradual height falls to occur across the Gulf Coast region. This keep continued heat & humidity but increased scattered rain & storm chances to build into the region from the north. During this time, there could be enough westerly zonal flow for some organized convective & strong- severe potential into late week. There are some indications in long term convective outlooks & CSU machine learning probs for some isolated strong-severe potential, but this remains too far in the extended timeframe to introduce in HWO graphics for now. Seasonably warm conditions in low 90s on Wednesday will tamper down into the upper 80s to near 90 degrees south of I-20 by late week. Heat & humidity will be slightly less oppressive but still heat indices in the low-mid 90s, with less potential for heat stress. /DC/ && .AVIATION... (00Z TAFS) Issued at 643 PM CDT Sat May 18 2024 Isold SHRA may come in vcty of MEI by 02Z and reduce flying conditions. Elsewhere VFR conditions wl prevail until 10Z. After 10Z a brief period of MVFR/IFR vsby wl be psbl at MEI-PIB-HBG until 13Z. After 13Z VFR conditions wl prevail areawide through the end of the TAF period. /22/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 65 87 66 89 / 10 0 0 0 Meridian 64 88 64 90 / 30 10 0 0 Vicksburg 67 89 68 91 / 0 0 0 0 Hattiesburg 67 89 66 91 / 10 0 0 0 Natchez 66 89 68 90 / 0 0 0 0 Greenville 67 89 70 91 / 0 0 0 0 Greenwood 65 89 68 91 / 10 0 0 0 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$ AJ/DC/22
Area Forecast Discussion
National Weather Service North Platte NE
632 PM CDT Sat May 18 2024 .KEY MESSAGES... - An active weather pattern brings a variety of impacts, including severe weather and heavy rainfall Sunday through Tuesday. - A limited threat for late season frost, but cannot rule out a localized threat following a cool down mid week. - The pattern remains active through the week, brining the potential for precipitation nearly every day. Confidence on daily precipitation chances remains relatively low, due to uncertainty in exactly how the upper level pattern evolves. && .SYNOPSIS... Issued at 235 PM CDT Sat May 18 2024 Upper air analysis and satellite imagery this morning reveal an upper level low over north central North Dakota, and a developing shortwave over western Washington. At the surface, a low pressure system is located over Winnipeg, Manitoba this morning, with a cold front extending south through north central Kansas. High pressure is observed over the Nebraska Panhandle. && .SHORT TERM /THROUGH SUNDAY NIGHT/... Issued at 235 PM CDT Sat May 18 2024 Tonight, the stage becomes set for several days of active weather. As surface high pressure ejects to the east, a weak surface boundary may be the focus for some showers and thunderstorms this evening through Sunday morning, particularly across southwest Nebraska. As the nocturnal low level jet settles in, a plume of warm, moist air advects into the region. While this is happening, a low pressure system over Wyoming is expected to form and mature, developing a warm front and cold front before it heads east. The main forecast challenge in the short term will be how long these showers and thunderstorms linger, which sets up two main scenarios for Sunday evening. If the storms exit the region more quickly, as seen in HRRR guidance, there is a greater period of daytime heating, and as such a greater severe weather threat Sunday afternoon and evening. These solutions are presenting decent surface based CAPE and generally initiate storms along a line through most of the region. On the other hand, there is some slower guidance such as the NAM Nest, which holds the cloud cover from showers and storms a bit longer, limiting the daytime heating. These slower solutions limit the surface based CAPE, keeping storms more elevated in nature, and in some cases wipes the thunderstorm threat out by tomorrow evening. What does remain consistent is the plume of moisture ahead of the approaching system. Additionally, forecast soundings all tend to show a potential severe weather environment tomorrow evening, with ample CAPE and shear profiles. If the daytime heating can erode the capping layer, and storms can tap into the surface based layer, the environment seems primed to produce large hail and damaging winds. If the cap remains in place, then convection likely remains elevated, still with large hail potential, but may end up being hindered unless it can tap into the surface moisture. && .LONG TERM /MONDAY THROUGH SATURDAY/... Issued at 235 PM CDT Sat May 18 2024 Showers and thunderstorms Sunday night begin to taper off after midnight, giving a brief dry period on Monday morning. By the afternoon, another batch of showers and thunderstorms develops to the west and begins to track across the forecast area. Overnight Monday into Tuesday continues to be highlighted as the peak intensity of this precipitation event. Current guidance suggests that forecast precipitable water values will exceed the climatological 90th percentile. To further back this, ensemble guidance is now highlighting portions of north central Nebraska and the Sandhills with a 60 percent chance of exceeding 1 inch of rain in 24 hours. As for expected amounts, followed with the Weather Prediction Center guidance which calls for storm total rainfall around 1 to 3 inches across the region from tonight through early Wednesday morning. Currently, the highest amounts are expected across the Sandhills, but with the convective nature of the rain, locally higher amounts are possible. The next concern comes with a mid week cool off Wednesday morning. The latest forecast sees temperatures trending up slightly, however some of the lower end guidance brings mid to lower 30s across southern portions of the Panhandle. Will continue to keep an eye on temperature trends over the next several days, as temperatures in the mid to lower 30s could cause some late season frost concerns across the southern Panhandle. At this time, the chances seem somewhat limited, but again, will be worth keeping a close eye on. Mid week through the end of the week, the upper level pattern remains fairly active. A series of shortwave and upper level lows persist across the Northern Plains, with variations in the placement of surface systems and associated rainfall. Precipitation chances remain through the end of the week, however, it is a bit difficult to nail down a precise timing right now. Certainly, the synoptic forcing will be there, so it will also be worth keeping an eye on how the upper level pattern evolves over the next several days to more precisely time precipitation chances through the week. For now, will continue to stick with general chances of showers and thunderstorms through the week, however, follow on forecasts may be able to refine the timing as models resolve the pattern later this week. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 625 PM CDT Sat May 18 2024 VFR conditions will continue through the overnight period, though clouds will begin to fill in and lower as rain showers develop Sunday morning. MVFR to locally IFR ceilings are likely for southern terminals after sunset, impacting KLBF. Winds will strengthen out of the south with gusts exceeding 25 knots. Clouds will begin to scatter out towards the end of the valid period. Confidence on timing and specific impacts from the rain showers is rather low at this time, thus future amendments and inclusions will be possible. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Richie SHORT TERM...Richie LONG TERM...Richie AVIATION...Viken
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
907 PM CDT Sat May 18 2024 .KEY MESSAGES... - Small chance (~20%) for some isolated/widely scattered showers/storms later this evening as a weak cold front moves into the area. - A few additional isolated showers and storms possible Sunday afternoon and early evening, mainly south of the Illinois and Kankakee River Valleys. - Summer-like warmth expected through Tuesday night, interrupted only by lake cooling Sunday; then during any showers/storms Monday and Tuesday. - Scattered thunderstorms likely Monday afternoon and evening across portions of northern Illinois, a few of which could be strong, and capable of causing heavy downpours and ponding - Scattered (mainly non-severe) thunderstorms possible Tuesday morning and then after a break, widespread thunderstorms in the evening, including a severe threat for parts of the area && .UPDATE... Issued at 859 PM CDT Sat May 18 2024 This evening, we find a weak cold front draped across eastern IA and up through central WI propagating eastward toward northern IL. Clusters of strong thunderstorms can be found ahead of the front across central and northern WI where there is notably better forcing for ascent, both along the face of the front and from features aloft. What little activity we had brewing out to our west a bit earlier this evening has fizzled away meaning areas upstream are rain-free for the time being. While most high res guidance has dry conditions prevailing along the front, if not producing just a few sprinkles, the RAP and HRRR have consistently been resolving a little bit of shower/storm redevelopment along the line within the next few hours just prior to reaching the CWA. Some low level deformation appears to be the primary driver behind this redevelopment as it looks to stretch the low level vort lobe and provide us with a little uptick in pre-frontal forcing over the next few hours. With dry low level air in place, LFCs across northern IL are pushing 10,000+ ft AGL, which equates to around 700 mb, with more and more MUCIN building up as the evening progresses. And with such shallow moisture to work with beneath awfully dry mid level air, it`s going to be tough to overcome these dampers and produce any precip, even with the added forcing. If anything does manage to go up, chances are seemingly greatest across far north central IL late this evening with the environment becoming even less favorable to support precip as the front moves into the Chicago metro later tonight. The current forecast brings slight chances across our northern CWA with the front, and that seemed appropriate still. That being said, the short term forecast remains very much on track. Doom && .DISCUSSION... Issued at 315 PM CDT Sat May 18 2024 Through Sunday Night: Very warm and somewhat more humid weather has set up across the area this afternoon in advance of an approaching cold front across the Upper Midwest. While there have recently been a few attempts at thunderstorm development across northwestern IN where weaker capping exists, no more than some isolated sprinkles or light showers are expected east of I-57 this afternoon. Elsewhere, partly cloudy and warm conditions will persist the remainder of the afternoon as inland temperatures top out in the mid 80s. Slightly cooler conditions are expected near the IL Lake Michigan shores due to an onshore southeasterly wind component. Diurnal heating and destabilization in advance of the approaching cold front to our west-northwest is expected to foster scattered thunderstorm development across parts WI and northeastern IA later this afternoon. While this activity should persist into this evening as the cold front begins to approach northwestern IL, a gradual weakening trend is expected through the evening as the boundary layer stabilizes. Nevertheless, I opted to add some slight chance POPs (20%) along the front across northern IL later this evening. Areas in and around the Rockford area stand the best chance to have a few of these weakening showers and storms in the 10pm to midnight timeframe. The cold front is expected to stall out over my southern counties in central IL and IN on Sunday. North of the boundary, a drier airmass will filter into the area on east-northeasterly winds. Accordingly, a less humid day is expected for much of interior sections of northern IL (especially north of I-80). Temperatures will be the coolest near the lake, where readings will hold in the upper 60s to around 70. Farther inland, temperatures will top out in the low to mid 80s. Much of the area will be precipitation free on Sunday due to the drier easterly winds. However, a moist and unstable airmass will remain in place to the south near the stalled frontal boundary across central IL and IN. Therefore, as capping weakens in the afternoon, some isolated showers and thunderstorms cannot be ruled out, especially south of the Kankakee and Illinois River Valleys. While weak flow through the troposphere will curtail any threat for organized storms, any showers or storms that do manage to develop Sunday afternoon will be very slow moving at 10 mph or less. This could thus promote some very localized instances of heavy rainfall. These isolated storms should diurnally weaken after sunset Sunday evening, thus setting up a relatively quiet night for the area. We will have to keep an eye on convective trends to our west late Sunday night, however. Numerous thunderstorms are expected to develop and convectively enhance a mid-level disturbance across the Plains Sunday afternoon and evening. The decaying remnants of these thunderstorms are expected to shift east-northeastward across the Corn Belt Sunday night, and it is possible that some of them make it into northern IL into early Monday morning. We thus continue to carry some low end chances (~20%) west of I-39 late Sunday night to account for this possibility. KJB Monday through Saturday: On Monday, a lead short-wave and its associated surface low lifting into the upper MS Valley will drag a warm front north of the area. While the strongest forcing will pass north of our area, the southern flank of the short-wave will provide some weak height falls. With strong heating bringing temps up into the mid-upper 80s and dew points into the 60s amidst 6.5-7.0 C/km mid-level lapse rates, looking at up to 1500 J/kg of MLCAPE. Areas near/northwest of I-55 or I-57 should see enough erosion of CIN (capping) that combined with the modest large scale forcing, expecting scattered thunderstorms to develop toward mid day and especially in the afternoon over the western or northwestern half or third of the CWA and then track northeast. Marginal (less than 30 kt) of deep layer shear and the modest mid-level lapse rates appear to be limiting factors for a more appreciable severe threat, though fairly steep low level lapse rates and seasonably high PWATs may contribute to wet downbursts with 50 to perhaps 60 mph gusts across the northwest CWA, in line with the SPC day 3 level 1 (marginal) severe risk. Our official forecast holds onto likely PoPs north of I-80 in the evening and overnight, though with weak flow aloft, diurnal loss of destabilization, and minimal large scale forcing, the highest thunderstorm coverage may in reality be confined to only an hour or two after sunset. Looking into Tuesday, global guidance has been consistent in bringing a lead short-wave northeastward across the mid-MS Valley during the morning hours. There may be enough of a MUCAPE reservoir for scattered showers and thunderstorms during this time, focused near/northwest of I-55, where we have 30-50% PoPs in our forecast. Morning timing and marginal deep layer shear suggest primarily non-severe thunderstorms, with maybe a chance of an isolated marginally severe hail or wind producer. Similar to our previous discussion, Tuesday afternoon continues to look like a gap in the convection that should support temps at least in the mid to upper 80s, and possibly tagging 90F if clouds really scour out. Southerly winds will gust up to 30-35 mph. The powerhouse cyclone for late May that has exhibited an overall slowing trend vs. a few days ago will have the surface low northwest of Des Moines early Tuesday evening (around 00z). Initial supercells initiating west of the MS River may tend to congeal into a squall line or bowing segments into the evening, with a coherent but possibly weakening severe MCS tracking eastward across the area during the evening. Given the slightly later and less favorable timing, areas of the CWA within the 30% probs area in the SPC Day 4 outlook correspondingly appear to have the highest severe chance. With this said, strong dynamics and strengthening southerly low-level flow may offset diurnal stabilization enough to keep the severe (mainly wind) threat going farther east, overall fitting the 15% area on the outlook. Thunderstorm coverage should wind down overnight Tuesday night and then expecting the cold front to clear the area by Wednesday morning. Barring a slightly slower trend in the cold frontal passage, Wednesday will be a breezy, cooler (highs in low-mid 70s), and dry day for most of the area. In this scenario (slightly slower cold front), the best chance for any showers and a thunderstorm will be southeast of I-55, where chance PoPs were maintained. Dry and pleasant weather Thursday, with highs in the mid to upper 70s, may very well persist through the day on Friday, before shower and thunderstorm chances possibly return at the end of the period. An early glance at Memorial Day Weekend points toward seasonable temps and some potential for showers and thunderstorms at times, but that`s about all that can be said this far out. Castro && .AVIATION /00Z TAFS THROUGH 06Z SUNDAY/... Issued at 614 PM CDT Sat May 18 2024 Key Aviation Messages: - Slight (<20%) chance of a shower or thunderstorm late tonight with a cold front moving through the area. - South-southwest winds will shift north-northwest behind the front pre-dawn Sunday, then northeast around/after sunrise. Surface low pressure was over far western Ontario early this evening, with a cold front trailing through western WI into eastern IA. South-southwest winds (with a few 15-20 kt gusts prior to sunset) will prevail ahead of the cold front into the overnight hours, before shifting north-northwest behind the front which should move through KRFD 06-07Z and KORD/KMDW 09-10Z. Isolated to widely-scattered showers and thunderstorms were occurring ahead of the front currently, but are expected to diminish in coverage with the loss of diurnal heating after sunset. High-res CAM guidance suggests most of these would dissipate before reaching the Chicago terminals later tonight. KRFD has a little better chance, but probability is too low for TAF mention. Winds will shift northeasterly early Sunday morning, and will remain from that direction through the day, before trending more easterly Sunday evening. VFR conditions should prevail through the period. Ratzer && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...Air Quality Alert until midnight CDT tonight for INZ001-INZ002- INZ010-INZ011. LM...None. && $$ Visit us at weather.gov/chicago
Area Forecast Discussion
National Weather Service Marquette MI
657 PM EDT Sat May 18 2024 .KEY MESSAGES... - Increasing threat for severe thunderstorms capable of damaging winds and large hail across western Upper Michigan late this afternoon into the evening hours. - Borderline elevated fire weather conditions on Sunday with very dry conditions, but winds on the lighter side. - Frequent periods of showers Monday through late week, but mainly focused on Monday and also Tuesday afternoon and Tuesday night. - Above normal temperatures early in the week falling to below normal late week. && .SHORT TERM /THROUGH EARLY THIS EVENING/... Issued at 309 PM EDT Sat May 18 2024 Forecast is mostly on track early this afternoon except for a few pesky rain showers that continue to percolate across the Copper Country on the cool side of a ~40 kt low level jet. There was some thunder/lightning with this activity before it moved into our area, but has just been showers since then. Looking around local weather stations indicates morning rainfall has been difficult to measure, probably due to the deep inverted-v signature evaporating most of the droplets. Otherwise temperatures have warmed into the 70s and 80s in line with the morning forecast with the warmest spots being L`Anse, Harvey, and Covington that all observed 84F around 2PM. Relative humidity values decreased to 28% at Baraga Plains, Golden Lake, and Michigamme sites with everywhere else staying at or above 30% at this time. The eastern edge of lower RHs appears to be a subtle Lake MI lake breeze with a subtle wind shift from SSW to SSE and dew points a few degrees warmer. The main forecast challenge going through this evening continues to be thunderstorm chances as a cold front sweeps east across Upper Michigan. Many different observation platforms reveal a cold front extending south from the MN arrowhead toward La Crosse, WI. A lake breeze boundary over the Bayfield Peninsula is also apparent on DLH radar with SPC mesoanalysis of surface vorticity and divergence highlighting these features well. The latest 18z mesoanalysis also shows SBCAPE around 1500 J/kg along the MN/WI state line beneath 0-6 km bulk shear of 30-40 kts, which is conducive to marginally severe thunderstorms. Large hail and damaging winds are the most likely hazards and deep inverted-vs with DCAPE of similar magnitude as MUCAPE suggests damaging winds may be more prevalent. Several recent HRRR/NAM nest runs have shown gusts at or near severe thresholds with the most common location being near and northeast of the Porcupine Mountains. Satellite/radar imagery shows orphan anvils over northern WI indicating updrafts are trying to get going, but have so far failed to persistently break a mid level capping inversion. However, HREF guidance indicates rapid initiation over northern WI around 20Z/4PM eastern with coverage increasing as it moves into Gogebic County by 22Z/6 PM eastern then well into the western UP by 00z/8 PM eastern. Thunderstorm activity is expected to be weakening as it moves into the central UP due to the loss of surface heating. However, the threat doesn`t end until the cold front moves through and the frontal boundary apparent on DLHs area is about 5 hours away according to the time of arrival tool. This is a fair amount slower than CAMs implying storms may be outflow-dominant, surging ahead of the boundary. As far as rain totals ensemble guidance favors a quick 0.10-0.20in of rain for the most part, but there is a chance (30- 40%) for heavier amounts up to a half inch in any heavier downpours. Skies quickly clear from west to east behind the front while winds veering westerly before becoming light and variable under surface ridging. && .LONG TERM /TONIGHT THROUGH SATURDAY/... Issued at 551 PM EDT Sat May 18 2024 An active pattern will continue across the U.S. during this week. Troffing currently over western Canada into the northern U.S. Rockies will amplify over the next few days, leading to western Canada/western U.S. troffing this week. A series of shortwaves dropping into this trof from the N Pacific will then eject e and ne across the U.S., supporting the active pattern. For Upper MI, the result will be several opportunities of rainfall this week. The first is just beginning and continues into tonight. The second follows late Sun night thru Mon evening, the third Tue aftn thru Wed, possibly lingering into Thu, associated with the strongest low pres of the week, and finally the fourth at some point Fri thru the weekend. Models are in overall good agreement thru midweek. Timing of the last system is most uncertain, but that`s expected given the farther time range out in the model runs. So, expectation is for overall above normal pcpn across Upper MI over the next 7 days. This will work to ease still lingering drought over portions of western Upper MI where, per the 5/16 U.S. Drought Monitor, severe drought was still indicated, centered around the Porcupine Mtns, and also in eastern Upper MI where moderate drought was still indicated from eastern Delta to western Mackinac counties. As for temps, above normal readings will be the rule thru Mon, warmest on Sun. Temps will then trend downward to blo normal Thu/Fri, due to the flow around the deep low that passes across the area midweek. A return toward normal expected over the weekend. Beginning tonight, a mostly narrow band of convection associated with cold front still currently w of Upper MI will continue progressing eastward with a tendency to diminish with time once it reaches central Upper MI due to loss of daytime heating and resulting waning instability. Risk of damaging winds/large hail exists across roughly the w half of Upper MI owing to 500-1000j/kg of MLCAPE over the next few hrs and deep layer shear of 30-40kt. Last of the diminishing shra/tsra will exit the eastern fcst area 06- 09z. Skies will quickly clear from w to e after fropa. Expect lows generally in the upper 40s to lwr 50s F across the area. On Sun, sfc high pres ridging will move to the Upper Great Lakes along with and an associated very dry air mass. Full sun thru the morning will give way to some mid/high clouds arriving from the w in the aftn. Strong insolation will result in deep mixing into extremely dry mid-levels. NAM shows late morning dwpts at 800mb/~5kft AGL ranging from -20 to -40C, though this is the low end of the model guidance. Moisture aloft does increase during the aftn, but mixing potential still supports sfc dwpts falling thru the 30s F. Some locations will see upper 20s F. The low dwpt potential is evident thru local mixed dwpt tool and simply in raw model guidance, HRRR most dramatically (it often captures mix down drying quite well). With high temps in the mid/upper 70s F across the interior, the low dwpts will drive RH down to around 20pct across much of Upper MI Sun aftn. The good news is winds will be on the lighter side, though a little higher than previously expected. Sustained winds will be around 10 mph with gusts to around 15 mph. Winds will be strongest across the Keweenaw with gusts to around 25mph there. Will need to monitor for lightning strike started fires, especially if rainfall from storms is more limited tonight. Lake breeze development will limit fire wx concerns close to the Great Lakes shorelines due to cooling conditions (temps falling into the 60s F), and higher dwpts, resulting in higher RH. Out of the amplifying mid-level trof over the western CONUS, next shortwave will lift to the Upper Great Lakes on Mon, accompanied by a surge of precipitable water up to ~190pct of normal. This increase in moisture along with increasing isentropic ascent will lead to shra/isold tsra and a widespread wetting rain across much of the fcst area. EPS ensemble probabilities show much of the area, except the Keweenaw, with a 30-50% chance of seeing 0.5 inch of rain from this system. Shra will arrive late Sun night and end most areas Mon evening. After a period of drier weather late Mon night thru Tue morning, a notably stronger shortwave ejecting from the western trof will reach the Upper Mississippi Valley Tue night. With this wave potentially closing off a mid-level low, it may be slower to exit across Upper MI into Ontario Wed/Thu. The GFS has been and continues to be on the faster edge of the model solutions. This fcst leans toward the slower consensus. Associated deepening sfc to 985-990mb range will be in the vcnty of western Lake Superior Wed morning. While the low track passing to the w of Upper MI will support the widest coverage of heaviest rainfall to the w of Upper MI, mdt to locally hvy rainfall will still be possible across the fcst area during the period of strong isentropic ascent/strong 850mb theta-e advection to the e of the low Tue night. Precipitable water increases to ~200pct of normal as well. Expect widespread rainfall across the area. EPS probabilities show a 30-70% chance for at least a half inch of rainfall from this system with the highest probabilities se and w. Shra coverage will diminish significantly for Wed, some areas may slip in dry weather for much or all of the day, especially e half. As the low lifts across northern Ontario, isold/sct shra may linger under cyclonic flow on Thu. Timing shra potential Fri/Sat is uncertain. For now, of the 2 days, Fri has the better shot at being a dry day. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 657 PM EDT Sat May 18 2024 VFR conditions prevail thru this fcst period. A brief 2 hour window through 02z at SAW and CMX could see some thunderstorms when a cold front sweeps east across Upper Michigan. Cloud cover also rapidly diminishes behind the front with skies becoming clear by Sunday morning. && .MARINE... Issued at 325 AM EDT Sat May 18 2024 Stable conditions will lead to light winds of generally 20 knots or less prevailing over the lake into early next week, except for some 20-25 kt southeast gusts today over the east half ahead of an approaching cold front. Thunderstorms are possible today into tonight as the cold front marches across the lake. These storms may contain small hail, gusty and erratic winds, and frequent lightning. More thunder chances return late Sun night into Monday and then again late Tuesday into Tuesday night as a series of disturbances track northeast across the Upper Great Lakes region. Models and ensembles indicate winds will ramp up Tue night into Wed as a stronger low pressure center tracks across the western and northern portions of the lake. Ensemble probabilities show a 40-60 pct chance of gale force gusts to 35 knots late Tue night into Wed across western and northern sections of the lake. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...EK LONG TERM...Rolfson AVIATION...07 MARINE...Rolfson
Area Forecast Discussion
National Weather Service Omaha/Valley NE
621 PM CDT Sat May 18 2024 .KEY MESSAGES... - Several rounds of strong to severe thunderstorms will be possible across our region tomorrow through Tuesday afternoon. All modes of severe weather including flash flooding will be possible. - There will be another chance for thunderstorms Thursday night. Overall risk of severe weather appears low at this time. && .DISCUSSION... Issued at 159 PM CDT Sat May 18 2024 Today through Tomorrow Night... A warm and dry air mass will be in place this afternoon in association with a high pressure that has taken residence across our area. Clear skies and high temperatures in the upper 70s to mid 80s will be on tap for us before temperatures start cooling after sundown this evening. Tonight will begin a prolonged period of rain and thunderstorm chances, lasting through Tuesday afternoon. Aloft, models have consistently resolved a deepening longwave trough over the western CONUS. While this main upper-level disturbance is not expected to eject out into the Plains until later Monday night, a series of subtle shortwaves are anticipated to eject out into our area downstream of this feature in the days prior. The first in this series of disturbances is going to be a low-amplitude negatively tilted shortwave that should kick out into the central High Plains by 7 PM this evening. Scattered showers and thunderstorms should develop in response to the forcing associated with this disturbance, and generally grow upscale as the system propagates towards the northeast overnight tonight. With surface dew points in the 40s, this convection is expected to remain elevated. However, short term CAMs depict a cold pool maturing under this cluster of storms owing to evaporative cooling from the deep and dry low-levels. As such these storms will pose a low-end wind threat through the early morning hours tomorrow morning. Storms should moved into portions of east- central Nebraska by 3 AM in the morning, with the US-30 corridor an approximate center line for the region of highest rain and strong wind chances. Wind gusts of 45 to 55 mph are possible, with a severe wind gust up to 60 mph not out of the question. These storms should move into central Iowa by 9 AM tomorrow morning. Additional showers and thunderstorms are expected to trail this initial round of storms, bringing cloud cover and rain to much of eastern Nebraska and western Iowa through the morning hours tomorrow. This will act to delay recovery and destabilization of the atmosphere until the afternoon hours. By early afternoon tomorrow, winds are expected to become south/southeasterly as a warm front slowly advances north across the area. This will help advect gulf moisture back into our region from the south, with short term guidance bringing dew points in the low 60s up to the I-80 corridor by 7 PM tomorrow. This front will be the focus for a conditional threat for isolated severe thunderstorms tomorrow. All CAMs have trended towards eroding the capping inversion by 4 to 5 PM, with MLCAPE ranging from 1500 to 2250 J/kg. Aloft, a 500 mb jet is expected to be in place over our area, bringing 45 to 60 knots of bulk shear over portions of southeast Nebraska and southwest Iowa. 0-1 km shear will be on the weaker side with shear magnitudes under 20 knots and 0-1km SRH around or under 100 m2/s2. This will support a large hail and damaging wind threat with any storm that can develop. The tornado risk appears to be much lower with these storms, but non-zero. Further to our southwest, scattered thunderstorms are expected to develop along a dryline in western Kansas and Nebraska. These storms will quickly grow upscale into an MCS and track east across the central Plains. These storms are not expected to reach our area until after 7 PM tomorrow evening. The primary threat for these storms will be strong damaging winds. With lowering LCLs and a strengthening low-level jet tomorrow after sundown, a spin-up tornado or two cannot be ruled out. The highest risk for severe weather will be south of I-80 sometime between 9 PM and midnight. There will be a more conditional threat for strong winds with another potential cluster of storms that may track across northeast Nebraska tomorrow night. The pre-storm environment in this region will be less favorable as the warm front will struggle to get this far north in addition to the environment being more worked over by convection tonight into tomorrow morning. Nonetheless, a few CAM solutions depict a second cluster of storms that will weaken as they traverse east across northeast Nebraska. These will also pose a risk for strong winds tomorrow night, with the time frame of highest risk being between 10 pm and 1 am. The risk for severe hail and tornadoes with this particular cluster of storms appears low at this time. Monday through Tuesday Night... The aforementioned longwave trough out west will approach our area on Monday. Synoptic scale forcing for ascent and height falls will aid in surface cyclogenesis in the central Plains. The favored area for surface low development seems to be southwest Kansas at this point in time. Extending northeastward out of this developing low pressure, a warm front will arc across central and northeast Nebraska, with a moderately unstable airmass to the south and east of the boundary. Surface dew points by Monday evening will likely range from the mid 60s across east-central Nebraska and western Iowa, to around 70 degrees in southeast Nebraska. Model trends over the last day have been to weaken the capping inversion over our area Monday afternoon as well. As such, with periods of substantial forcing as low-amplitude shortwaves eject into the Plains downstream from the main disturbance, the potential for scattered strong to severe thunderstorms Monday evening is increasing (30 to 50 percent at this time). Uncertainty with regards to the magnitude of destabilization and exact strength of the capping inversion will remain until Monday becomes in range for short term CAMs. This will preclude any further discussion on coverage details. Nonetheless, GFS and EURO both show an airmass with 2000 to 2500 J/kg of surface based CAPE under 10 to 20 J/kg of CIN across much of eastern Nebraska and western Iowa. For what it`s worth, the 18Z run of the HRRR leaves southeast Nebraska uncapped by 1 PM on Monday. Furthermore, SREF probabilities for CAPE at or greater than 3000 J/kg range from 50 to 75 percent south of the I-80 corridor. The limiting factor to organized convection, at least early Monday afternoon will be weak shear over our area. Bulk shear values will remain under 30 knots until around mid- afternoon. As the evening progresses and flow aloft strengthens with the approach of the trough out west, the dynamic environment should improve to better support organized convection. All in all, this will all support an isolated threat for strong to severe thunderstorms, with large hail being the primary hazard Monday late afternoon and evening. By Monday night, the environment is expected to look very different than the one in place over our region Monday afternoon. Aloft, a speed max is expected to eject out into the Plains as the axis of the main trough moves to the east of the Rockies. With much stronger flow aloft, bulk shear across our region will range anywhere from 40 to 60 knots by midnight Monday night. At the surface, the aforementioned surface low will track north-northeast, likely in the vicinity of south- central Nebraska/north-central Kansas by Tuesday morning. With the development of a strong low-level jet (flow by 4 AM Monday at 850 mb may exceed 50 knots), all modes of severe weather will become increasingly likely for any convection that can persist into the overnight hours. The one complicating factor to this set up is there is still substantial uncertainty with how much the nocturnal boundary layer will cool across our region. Strong mixing from the low-level jet in conjunction with strong advection of warm air and moisture at the surface from the south will mitigate nocturnal cooling (and by correlation minimizing CIN that can develop ahead of any pre-existing storms). On the other hand, strong southwesterly flow in mid- levels may advect much warmer temperatures that may develop a capping inversion above the boundary layer, helping weaken storms into the early morning hours. Regardless, there may be sufficient forcing for ascent driven by the strong dynamics at play Monday night to overcome this. These uncertainties should be ironed out over the next few forecast issuances. Until then, will refrain from any further discussion on timing, coverage, and threat details. Tuesday morning. A surface low is expected to be somewhere in northeast Nebraska or southeast South Dakota. A cold front will extend to the south-southwest of this front through central Nebraska into central Kansas. The airmass ahead of this front will destabilize very quickly, with convection initiating on the front as early as the late morning hours. While there is still uncertainty with the exact placement and timing of the system at this point, odds are increasing for rapid development of thunderstorms along the cold front in eastern Nebraska by around noon, with strong to severe thunderstorms exiting our region by mid afternoon. Surface based CAPE may exceed 3000 J/kg by noon, particularly across southwest Iowa. Bulk shear will also be very strong, with magnitudes 50 to 65 knots possible. Hodographs Tuesday appear to be fairly straight line at this time which would limit the tornado risk, at least until these storms move east of our region. As such, large hail and damaging winds will be the primary risk, with a low but non-zero tornado risk slowly increasing as the afternoon progresses. The highest risk for severe weather at this time appears to be southwest Iowa in the early to mid afternoon hours. Lastly, due to multiple rounds of heavy rain traversing our region, there will be a threat for flooding across all of eastern Nebraska and western Iowa through Tuesday afternoon. This risk appears to be maximized across northeast Nebraska and west-central Iowa where storm total rainfall amounts will range from 1 to 2 inches, with local amounts of 3 to 4 inches possible. Wednesday through Friday... The pattern should quiet down after our main system moves east on Tuesday. Another round of thunderstorms appears possible Thursday night, however the potential for severe weather is low at this time. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 621 PM CDT Sat May 18 2024 VFR conditions will likely prevail through the forecast period with increasing shower and thunderstorm chances late tonight into Sunday morning. Measurable precipitation appears most probable at KOFK where prevailing -SHRA will be indicated Sunday morning. At KOMA and KLNK, TEMPO -TSRA groups will be included for a 2-3 hr period Sunday morning. Otherwise, southeast winds are expected to increase to 12+ kt by mid-morning at KOFK, and midday or early afternoon at KOMA and KLNK. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Darrah AVIATION...Mead