Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/29/24


Area Forecast Discussion
National Weather Service Binghamton NY
810 PM EDT Sun Apr 28 2024 .SYNOPSIS... A frontal wave will bring showers and isolated thunderstorms to the area this evening. Lingering clouds and areas of fog are expected overnight into early Monday morning. A warm front will bisect the area on Monday, with partly sunny and very warm conditions from the Twin Tiers south across NE PA. The next front arrives Tuesday with a better chance for more widespread showers and scattered thunderstorms. Remaining very warm, with well above average temperatures through the end of the work week. && .NEAR TERM /THROUGH MONDAY NIGHT/... 625 PM Update... No major changes to the near-term forecast. The only change was expanding the areas of fog development overnight through the majority of Central NY and NE PA. We are currently monitoring for any thunderstorm development in NE PA now through the next few hours; these storms are not expected to become severe. Otherwise, forecast remains on track. 340 PM Update Main concern in the near term are the potential for scattered thunderstorms this evening across the Southern Tier and NE PA. MLCAPE values are being held in check by mostly cloudy skies and limited daytime heating from the northern tier of PA northward across all of CNY at this time. Current analysis shows only up to 250 J/kg, with sfc based LIs of 0 to -2 over the southern half of the forecast area. Bulk effective layer shear is between 25-35 kts out there this afternoon. With more clearing and temperatures in the upper 70s to lower 80s now from Towanda south to Avoca and Hazleton...this will be the most likely area to watch for scattered thunderstorm development over the next several hours. Latest CAMs such as the 18z HRRR show t`storm development by 4-5 PM over the NY Southern Tier , with a line of storms then dropping south toward the Wyoming Valley & Poconos between 5 to 9 PM this evening. There remains an outside chance for a stray stronger storm to develop, with a possible isolated instance of small hail or gusty winds. Guidance continues to show MLCAPE reaching 300-500 J/kg over this region before the storms move in. Further north the rest of the evening will be dominated by clouds and occasional rain showers, with thunderstorms being unlikely due to limited/ non-existent instability. The main concern up this way across Central NY will be the front sagging south overnight, bringing a relatively cooler air mass, which combined with light winds to produce areas of fog. Overnight lows dip into the 50s. On Monday, the latest guidance has finally come into better agreement on where the quasi-stationary warm front will set up. Based on some of the hi-res guidance the front looks to be located right along the US-20 corridor for much of the day. Along and north of this front low clouds and stratus linger most of the day and temperatures only reach the 60s to low 70s. South of the front, the clouds scatter out by late morning, with partly sunny and very warm conditions expected. With the upper level heights building overhead any shower or t`storm development will be isolated. There will be plenty of instability (1000 J/kg SBCAPE) but no lifting mechanism to get the storms initiated. Highs range from the upper 70s to mid-80s south of the front across the Twin Tiers and all of NE PA. Generally quiet and warm weather Monday night, with perhaps just a few showers riding across the top of the ridge. Muggy for late April with lows in the mid-50s to lower 60s expected. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... 300 PM Update... Tuesday remains a tricky forecast at this time. The ridge sitting overhead should break down Monday night, allowing a trough to move into the region from the west and bring SW flow across the area. Warm and moist air should move into the region, with morning temperatures rising into the 60s to low 70s with dewpoints in the low 60s. The big question here is will sky cover be too thick to allow sufficient surface heating to break a modeled cap between 700-600mb. Showers are expected to ride the western edge of the ridge, west of our region Monday night into Tuesday morning, which should pump clouds into the area. Guidance is still unsure on how the event evolves, with some incorporating more clouds and less instability, while others are showing less clouds and more instability. Temperatures are currently forecast to reach the mid to upper 70s, but a few degrees difference either higher or lower makes a large impact on the severe weather chances. Sifting through it all, leaning on the lower values of 500-1000j/kg of CAPE and 0-6km bulk shear between 25-35kts seems reasonable at this time, stretching from NEPA into Delaware/Otsego counties. This should be sufficient to generate scattered severe thunderstorms ahead of the approaching front, but timing of the trough and front arrival is still uncertain, with the longer range CAMs showing a quicker, late morning arrival vs. global models which show a slower, wetter solution. Hydrologically, PWATs of 1-1.30in(2-3 standard deviations higher than normal) imply enough moisture for heavy downpours and corfidi vectors show training potential in the afternoon. Warm cloud depths of 7-8k ft are not optimal for heavy rain production, but tall enough that heavy downpours are possible. All of these point to a chance for localized flooding under heavy rain. Adding confidence to this is WPC has put us in a marginal outlook for excessive rainfall. Rain chances linger, especially east of I-81 Tuesday night into Wednesday as the upper level trough slowly moves eastward. Temperatures Tuesday night will be in the mid to upper 50s. A ridge will quickly follow the departing front/trough on Wednesday, building in from the SW and keeping warm air in the region. Skies will clear from SW to NE, allowing highs to climb into the upper 60s to mid 70s. High pressure remains in control Wednesday night, keeping lows in the upper 40s to low 50s. && .LONG TERM /THURSDAY THROUGH SUNDAY/... 330 PM Update... Thursday and most of Friday should be quiet and warm, with temps climbing into the 70s. The next system will arrive during the weekend as a low pressure center over the north central US climbs north into Canada and pushes a frontal boundary through the region, bringing another round of rain showers and isolated thunderstorms Sat and Sun. Guidance remains unsure on the timing and strength of this feature so the NBM solution was relied upon. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... A few lingering showers may affect RME and ELM/AVP over the next couple of hours, but the general trend will be for diminishing rain chances through the night. A frontal boundary will sag southward towards the NY/PA border overnight, with widespread fog and stratus expected to develop across the region, especially along and north of the front, with IFR conditions at most CNY terminals. AVP still looks to stay south of the front and the lower ceilings, though some light fog or mist is possible there before sunrise. Conditions will improve slowly through the morning, with restrictions (MVFR or fuel-alt) lingering into the afternoon north of the Twin Tiers. Outlook... Monday Night...Lingering MVFR SYR and RME. VFR expected for the rest of our taf sites. Tuesday...Restrictions likely in rain showers and thunderstorms, especially in the afternoon and evening. Wednesday...Lingering morning clouds and restrictions possible, becoming VFR in the afternoon. Thursday...VFR Likely. Friday..Mainly VFR, but late day showers/t`storms possible. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...None. && $$ SYNOPSIS...MJM NEAR TERM...KL/MJM SHORT TERM...JTC LONG TERM...JTC AVIATION...MJM/MPH
Area Forecast Discussion
National Weather Service Des Moines IA
638 PM CDT Sun Apr 28 2024 ...Updated for the 00z Aviation Discussion... .KEY MESSAGES... * Another opportunity for a few strong storms today, mainly W/SW, but threat scaled back overall * Briefly quiet Monday, then additional threats for some strong to severe storms return to the area Tuesday and possibly again Wednesday. && .DISCUSSION... Issued at 308 PM CDT Sun Apr 28 2024 Largely been a cloudy and more dreary day across the area thus far with mostly cloudy skies and periodic showers streaming across the area. While the overall severe threat remains on the lower end of the spectrum, there are a couple of items of note that may yet yield a stronger storm or two and/or a weak tornado or two. RAP/HRRR and CAMs in general, have struggled to pin down existing shower/storm activity back west as well as the stratus deck evolution across the state today, with all holding onto stratus into mid to late afternoon before more rapid erosion. By about 18z, about the southern two-thirds of Iowa had already seen a good amount of erosion of the stratus deck, resulting in some filtered sun through a relatively thin mid-level cloud deck. This may help develop more favorable conditions for a stronger storm or two, including potential for marginally supportive to supportive low level CAPE for a landspout or weak tornado or two as the upper/surface lows move through. However, existing shower activity ahead of the more vigorous convection near surface front muddy the waters once again. While HRRR has struggled some, it has had a consistent trend in upping SBCAPE values along/ahead of the surface front with recent runs suggesting potential for around/above 1500 J/kg versus <1000 J/kg in morning runs. Similar trends have been seen in the SPC RAP mesoscale analysis in 0-3km CAPE and associated NST parameter space. Deeper layer shear largely remains messy, marginal, and predominantly unidirectional, limiting organization, large hail, and damaging wind threats. At this point, the suggested main threat may be a few weak tornadoes/landspouts associated with any more vigorous convection along the surface front and nearer the core of the low this afternoon and evening before the lowest levels stabilize. This would point to west-central into northwest Iowa this afternoon into the evening. Monday will be on the quieter and side as the upper and surface lows pull off to the northeast and westerly winds prevail. A few low level instability driven showers may be seen north. Temperatures quickly rebound Tuesday with southerly flow increasing ahead of a shortwave trough and developing surface low. Expect highs to soar back towards the upper 70s and lower 80s. Moisture does not quite rebound in a similar fashion, but consistent signal for SB/MUCAPE values to approach 2000 J/kg in a corridor over eastern Nebraska into western Iowa by the afternoon and evening. Wind profiles will be supportive for some organized convection with fair curvature and effective shear values in excess of 40kts within various guidance. Hail and damaging winds appear to be the primary threats at this time, though a tornado would remain possible with storms near/along the surface cold front. Into Wednesday, additional chances for showers and storms present themselves as a warm front quickly lifts back northward ahead of upper level shortwave and developing surface low across the Front Range. Guidance this afternoon has trended northward with the warm frontal placement by the evening/overnight, so details remain in flux for both strong/severe potential and any heavy rain threat. Activity looks to be most robust with increasing LLJ activity Wednesday night. Temperatures ease through the remainder of the week too with highs back into the lower 60s return by Friday. Also rounding out the week, discrepancy remains among flagship deterministic models and ensemble suites with Euro solutions still favoring a much more rapid upper trough passage while GFS/GEFS remain slower and would prolong shower/storm opportunities to end the week. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 634 PM CDT Sun Apr 28 2024 Area of showers and isolated thunderstorms will move across the area, mainly early this evening. A period of VFR conditions is possible behind the precipitation before stratus fills in from the northwest. IFR to MVFR cigs will arrive overnight then cigs will gradually improve during the day Monday. The wind will become southerly this evening then westerly overnight into Monday. The wind may have gusts near 25 kts Monday afternoon. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Curtis AVIATION...Donavon
Area Forecast Discussion
National Weather Service Sioux Falls SD
1039 PM CDT Sun Apr 28 2024 .KEY MESSAGES... - Intermittent periods of light to moderate showers will continue to spread north through late tonight. Additional accumulations between 0.25" to 0.75" of an inch are expected through Monday morning. - There are still some low probabilities of an isolated severe weather risk across northwestern IA this evening with large hail up to half dollar size being the main threat. - Severe weather threat increases Tuesday afternoon through early evening with a Level 2 of 5 risk. Large hail is the main threat, but damaging wind gusts, a tornado, and/or ponding of water from heavy downpours are secondary threats. - Cooler than or near normal temperatures are favored for Wednesday and beyond. A few periods of low temperatures in the 30s and lower 40s suggest frost/freeze concerns will linger into early May. && .DISCUSSION... Issued at 237 PM CDT Sun Apr 28 2024 REST OF THE AFTERNOON/TONIGHT: A wet and dreary day continues! Taking a look across the area, light to moderate showers along with a few thunderstorms continue to push northward ahead of the surface low which is currently positioned somewhere over northeastern Nebraska based on the wind field. With cold front sitting just west of the NE/IA border and the warm front lifting across northwestern IA; we`re starting to see more convective showers develop with some embedded thunderstorm as lift and instability (300-500 J/kg) increases along the cold front. As this system continues its slow walk towards the northeast, expect most of our current activity to either rotate to the north or northeast into the evening hours. Shifting gears to our severe weather chances; low confidence continues with a highly conditional environment this evening. Between the mostly stable environment brought from this morning`s rain and the lingering stratus deck across our area of interest this afternoon, i`m still not particular convinced that things can get going this evening. With that being said, there is still a conditional chance for a few stronger storms between the Hwy- 20 corridor and areas east of Hwy-59. Further analysis of RAP soundings at Spencer (SPW) and Sioux City (SUX) shows long skinny CAPE profiles (700-1000 J/kg) along with 30-40 kts of bulk shear. This combined with lapse rates varying between 6-7 degree C/km could lead to a few storms with some large hail up to half dollar size this evening with the best window being between 23z to 04z. However, these chances will be conditionally dependent on if the showery activity can clear out across northwestern IA in time for the atmosphere to destabilize. If not, a few moderate to heavy downpours will be possible with any developing activity at best. Lastly, as cooler air begins to pool into the area behind the surface low, temperatures will drop into the upper 30s to low 40s for the night. MONDAY: Looking into Monday, most of the lingering shower activity will continue to lift northeastwards during the morning hours as the surface low slowly rotates into central MN. Northwesterly surface winds will increase throughout the day as the SPG tightens as an upper-level ridge approaches. Wind gusts between 15-25 mph are expected across the area. Otherwise, mostly quiet conditions should return by Monday afternoon as increasing warm air advection (WAA) underneath the ridge brings our 850mb temperatures back towards the mid to upper teens by the afternoon. This along with decreasing cloud cover during the day should allow our temperatures to recover slightly with highs expected to vary between the low 50s to low 60s across the area with the warmest conditions expected along the Missouri River Valley. Unfortunately, the quieter condition won`t last for long as our attention pivots to the Rockies as a negatively tilted trough ejects into the northern plains during the day on Tuesday. TUESDAY: Warm air advection and southerly return flow bring a much warmer day Tuesday than the previous few days. Expect temperatures returning to near to above normal values with highs in the mid 60s to mid 70s. Breezy south gradient winds start the day, shifting southwest and west behind a passing cold front. Gusts will peak in the upper 20s and 30s. Main focus on Tuesday will be the threat for scattered strong to severe thunderstorms in the afternoon and evening. Despite initial zonal flow aloft, a jet streak digs the upper trough over the Northern Rockies and bringing broad upper level support for ascent between the upper jet and approaching negatively tilted upper trough. Despite scattered showers and storms in the morning in central SD, capping should greatly limit severe weather concerns until after noon. Moderate to high confidence in rain occurring with GEPS/GEFS and CIPS analogs favoring at least isolated strong to severe storms Tuesday afternoon and early evening due to narrow axis of 1-2 kJ/kg MUCAPE and 50+ kts of 0-6 km shear. 28.12z model soundings suggest skinny CAPE profiles and 7-8 C/km mid level lapse rates, and a not-so-favorable weak cold frontal passage suggests elevated storms near and west of I-29 with a linear mode. Though there is favorable low level curvature in hodographs, stronger mid level winds hold off until late in the day as do dew points exceeding 60F. Can`t rule out a tornado in northwest Iowa if the right conditions develop Tuesday evening, but the tornado threat is certainly greater further southeast in central Iowa. Additionally precipitable water values exceeding 1" (90th percentile of NAEFS/EFS) favor heavy downpours with some locations receiving over 1 inch of rain. Expect the main threats with the strongest storms to be large hail and to a lesser extent, damaging wind gusts. WEDNESDAY AND THURSDAY: Drier air aloft settles in with sfc high pressure overnight. With the upper low well to our north and the cold front sagging south to between the I-80 and I-70 corridors, ensemble clusters aside from 40% of GEFS members suggest Wednesday should be dry for many sites. Increased cloudiness with peeks of sunshine Wednesday should make for a fairly nice day with highs in the 60s to mid 70s. Another round of convection should fire in the Central Plains Wednesday afternoon and/or night, forced by an ejecting CO Low and associated low level jet. While chances for showers and storms increase Wednesday night and Thursday both from another mid level disturbance sliding in from the west and convective remnants in northwest Iowa, at this stage it seems unlikely that we will destabilize enough (MUCAPE < 500 J/kg) to see another round of severe weather threat. FRIDAY AND NEXT WEEKEND: Low confidence in the forecast for Thursday night and beyond as models struggle to handle the interaction between an upper low stalled over the Canadian Prairie and an upper trough approaching from the West. Near to below normal temperatures are favored for the end of the week and weekend. With lows dipping into the 30s and 40s, frost or a freeze still remains possible into early May. CPC highlights a slight (20%) chance of heavy rainfall over much of the Central U.S. for next Saturday and Sunday, so will want to monitor that period if you have outdoor activities planned. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 1035 PM CDT Sun Apr 28 2024 Showers and isolated thunderstorms begin to diminish from south to north later tonight into Monday morning. Ceilings will generally be in the IFR range, though may occasionally jump into the MVFR range. By Monday afternoon, ceilings will lift, then scatter out by late afternoon. Clouds decrease on Monday evening. Winds will be west/northwesterly tonight into Monday, gusting around 20 kts at times into mid evening on Monday. Winds then drop off by late Monday evening. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ DISCUSSION...Gumbs/BP AVIATION...JM
Area Forecast Discussion
National Weather Service Grand Rapids MI
1012 PM EDT Sun Apr 28 2024 .KEY MESSAGES... - Cold Front brings rain/thunder on Monday - Multiple Chances for Showers and Storms This Week - Warm Temperatures Through The Saturday && .UPDATE... Issued at 1007 PM EDT Sun Apr 28 2024 Minimal instability remains south of the warm front tonight. Mainly showers are expected overnight but some thunder can`t be ruled out. A steadier batch of showers is indicated by the 00z HRRR to arrive in the 06z-12z time frame. This activity is currently located across eastern Missouri but will head our way overnight. Looks like a wet morning commute especially along and west of a Big Rapids to Battle Creek line. && .DISCUSSION... Issued at 352 PM EDT Sun Apr 28 2024 - Cold Front brings rain/thunder on Monday Extensive cloudiness into this afternoon has so far muted any strong updrafts, although a few showers and towering cu have managed to form in the past couple hours across the southern half of the forecast area. Cannot rule out a few strong storms into early evening with deep layer shear values of 25 to 30 knots. Breaks in the clouds and surface heating could overcome the stabilizing influence of the extensive rain showers from last night into this morning. For tonight, we will watch whatever showers/storms are able to develop but they should diminish after sunset as sfc based instability diminishes, then look for showers and storms pushing in ahead of the advancing cold front overnight into Monday morning. Expect the bulk of those showers to come through between roughly 8 AM and noon on Monday with the potential for some stronger storms across the eastern forecast area as the airmass destabilizes. Scattered showers persist along and behind the cold front into Monday evening before drying works in from the west. - Multiple Chances for Showers and Storms This Week Tuesday will be the best chance for dry weather in the long term portion of the forecast thanks to a surface ridge and upper-level ridging forecast to move overhead. Ensemble probabilities have trended downward with precipitation chances for the Tuesday night into Wednesday timeframe due to questions on low-level moisture even with a vorticity maximum swinging through. An isolated shower can`t be ruled out north of M20 but given low confidence will leave the dry NBM PoPs as is. Showers and Thunderstorms more likely Wednesday into Thursday as a surface low to our west lifts a warm frontal boundary across Lower Michigan. Thursday could be the most active day of the long term period as MUCAPE values increase near to above 1000 J/kg Thursday afternoon in both ECMWF and GFS guidance with a 30-40 knot low-level jet. A shortwave then swings through the area Thursday night into Friday driving a front through keeping rain chances going. Predictability in the longwave pattern decreases notably into next weekend. While there are signals in cluster analysis and model guidance for a trough to setup over the central United States by next weekend, there is considerable variation in both the positioning and amplitude of this feature. - Warm Temperatures Through The Saturday Highs in the 60s are expected for Tuesday as a weak thermal trough quickly passes through the region. Temperatures warm for the mid to late work week into the 70s, with the 80s not out of the question, as southwest flow brings plenty of warm air into the Central Great Lakes. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 743 PM EDT Sun Apr 28 2024 The first item of interest for aviation operations is a front that is dropping down from the NE through the KLAN and KGRR areas. This front has really nothing with it, but there is a distinct wind shift from the South, to the NE. This should be in place for a couple of hours, and will likely not reach the other airports. The next item is rain chances. There are some rain showers developing north of all of the SW Lower terminals. There may be a few spotty showers this evening into the overnight hours at the I-96 terminals, but nothing too widespread. Thunder can not be ruled out, but the chance seems low enough during the night to keep it out for now. The terminals are likely to stay VFR for most of the night. Some stratus to the NE of KLAN and KGRR should be held back. There does look to be a more widespread area of showers that moves in from W to E starting around 10-12z. These showers are likely to bring conditions down to IFR at the I-96 sites closer to the wave. The I-94 terminals are likely to drop down into the MVFR category. These showers will move out then from 16-18z, and conditions will improve a category or two at each site. A few showers, and maybe a storm will remain possible then from 18-00z. Coverage looks quite limited and uncertain, so for now will go with VCSH. As we near this time frame and certainty increases, fine tuning of this period will occur. && .MARINE... Issued at 352 PM EDT Sun Apr 28 2024 Webcams and satellite do not show any extensive areas of dense fog over Lake Michigan this afternoon as winds have apparently been able to prevent its formation. We will keep mention of patchy fog in the marine zones for this evening. Winds and waves increase Monday afternoon and a Small Craft Advisory may be needed although conditions looks marginal. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ UPDATE...Hoving DISCUSSION...Ostuno/Thomas AVIATION...NJJ/Thomas MARINE...Ostuno
Area Forecast Discussion
National Weather Service Jackson MS
1056 PM CDT Sun Apr 28 2024 ...New MESOSCALE UPDATE... .MESOSCALE UPDATE... Issued at 1056 PM CDT Sun Apr 28 2024 Rest of tonight... Ongoing MCS is somewhat waning as it moves into the area, with the forward propagation component of this MCS more focused towards central-eastern AR. A tornado watch was issued for southeast AR, northeast LA & extreme northwest MS & continues through 2AM. GOES-East infrared imagery & regional radar mosaic indicate somewhat warming cloud tops aloft & convection somewhat waning in radar presentation on the leading edge of this MCS. More vigorous deep convection/intense cloud tops over southern portions of the ArkLaTex. Evening synoptic analysis remains across the Carolinas to Appalachians while subtropical sfc high remains right off the Atlantic seaboard. 1005mb sfc low is moving into the Mid West. As the trough swings east-northeast, strong southern stream shortwave, indicated by stout drying over the southern Plains, will continue to eject to the east overnight through the morning hours. This will provide the impetus for more convective development, especially in the areas along the ArkLaTex & expected to slide to the east-southeast a MCS. For areas south of the ongoing complex & cold pool moving into northeast LA & southeast AR, low-level jet around 30-40kts, low-level instability & somewhat favorably aligned low-level flow for organized MCS to remain likely into the overnight hours. SPC earlier added an "Enhanced" for areas west of the MS River & kept it confined to this zone, with the most likely area of seeing the higher wind probs of up to 70mph along & south of the I-20 corridor from Rustin, LA to Natchez, MS area through the overnight hours. Main hazards remain damaging winds 60-70mph, with best chances west of MS River, spinup tornadoes & large hail in any deeper core that could develop. Timing has been tricky, as guidance earlier indicated some of this convection could precede a later MCS, but have now congealed into one definitive MCS propagating southeast, with the southern half along & south of I-20 corridor becoming the most concerning. Main updates were to add the "Enhanced" to the HWO graphics for west of the MS River, tweak an earlier start timing for the western timing slot & speed up timing slightly along & east of the I-55 corridor. Heavy rain looks to be confined for the southwestern half of the area, with most confident area along & southwest of a line from Bolivar to Lincoln county in MS. No other major changes were needed. Updates are out. /DC/ && .DISCUSSION... Issued at 253 PM CDT Sun Apr 28 2024 As anticipated, weaker inhibition today is allowing for warm advection showers to develop and spread north across the forecast area today. Isolated thunderstorms are embedded with this activity as well, but deep layer shear is not favorable for organized updrafts. Expect quick moving, and short-lived storms where they do develop. Regional radar mosaic showed the remnants of last night`s convective line were all but washed out across North Texas into Arkansas, but an organized cluster of storms has re-fired east of Waco and Killeen in Texas this afternoon. High res guidance has struggled with how to transition from last night to today`s activity, but but they all generally get to the point of one or more MCS segments drifting east through Louisiana and Arkansas toward Mississippi late tonight. 06Z and 12Z HRRR were previous fast outliers, but 18Z run has come into a little closer agreement with consensus of HREF members regarding timing. Southerly low-level jet winds and greatest instability located to the south of any MCS activity will favor southward propagating MCS activity by morning (or at least most intense MCS activity farther south along any broken line). Forecast MLCAPE values over 1000 J/kg seem to favor MCS trajectory to be along or southwest of a diagonal line roughly from Ruston, LA down Natchez, MS or so. Depending on timing and placement of overnight storms, the potential for severe storms could extend farther east to around the Interstate 55 corridor. Bowing segments along any line could lead to increased potential for damaging wind gusts and possible spinup tornadoes. The Slight Risk for severe storms was expanded to account for this wind and isolated tornado potential - including southeast Arkansas, northeast and central Louisiana, and far southwestern Mississippi. The Marginal Risk area extends south through Mississippi generally along Interstate 55. In addition to any severe threat, heavy rainfall could cause localized flash flooding concerns. End timing is a little uncertain, but an organized line will probably clear out earlier in the day than anything disorganized. /NF/ Monday Night through Sunday: A fairly progressive split flow regime sets up over the CONUS through the rest of next week, driving a few potential periods of showers and thunderstorms as shortwave troughs moving east and interact with spring-like humid and unstable air masses across the South. Nothing at this point looks to fully scour out the decent moisture in the region, and PWAT values over 1.3 inches should support air mass thunderstorms on any given day. When not raining, afternoon high temperatures should push the upper 80s/lower 90s range. Glimpses of summertime are coming into view. /NF/ && .AVIATION... (00Z TAFS) Issued at 826 PM CDT Sun Apr 28 2024 Southeasterly sfc winds will continue through early evening. MVFR stratus should develop at all TAF sites, with onset between 29/04-7Z & earlier onset at southern-central TAF sites. TSRA ongoing across northern LA into southwestern AR will propagate northeastward, with more SHRA & TSRA expected overnight. Some gusts in these storms could bring 40-50kts at times & variable ceilings/vsby. Expect a gradual decrease in coverage from west-east overnight & some improvement to VFR flight categories in spots. SHRA & TSRA will decrease from west-east into the morning hours, mainly after 29/15-20Z. /DC/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 69 78 63 83 / 10 80 60 20 Meridian 64 81 63 84 / 0 70 80 30 Vicksburg 67 77 63 84 / 40 90 40 20 Hattiesburg 67 81 64 84 / 10 70 70 40 Natchez 67 76 63 85 / 40 90 40 30 Greenville 69 75 63 82 / 60 90 40 10 Greenwood 68 76 63 83 / 20 90 60 10 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$ DC/NF/DC
Area Forecast Discussion
National Weather Service North Platte NE
613 PM CDT Sun Apr 28 2024 .KEY MESSAGES... - Showers should linger across north central Nebraska this evening. - Seasonal to near seasonal temperatures are expected this week. - Rain chances return on Tuesday and will persist into next weekend. The best chances for rain will be Wednesday night into Thursday. && .SYNOPSIS... Issued at 309 PM CDT Sun Apr 28 2024 H5 analysis from this morning had a closed low just off to the west of North Platte Nebraska. A trough extended south of this feature into far western Texas. Immediately east of the trough axis, strong shortwaves extended from central Texas into the Ozarks. Further downstream, a ridge extended from the Carolinas, north to Lake Ontario. West of the trough and low, a secondary shortwave trough was located over southern Alberta with a closed low noted off the coast of central British Columbia. At the surface, low pressure was located over southeastern Nebraska. A warm front extended to the east into central Iowa. A cold front extended south of the low into central Kansas and western Oklahoma. Skies were cloudy this afternoon and very light rain showers were occurring over the central Sandhills into portions of central Nebraska. Temperatures as of 3 PM CT, ranged from 43 at Gordon and Thedford, to 51 degrees at Imperial. && .SHORT TERM /THROUGH MONDAY NIGHT/... Issued at 309 PM CDT Sun Apr 28 2024 Upper level low pressure will migrate northeast from northern Nebraska into southwestern Minnesota overnight. Weak lift will persist across far northern and northeastern portions of the forecast area this evening, and will lead to a continued threat for light rain through midnight. Thereafter, skies will continue to clear into the overnight with cool temperatures developing across the forecast area. For lows tonight, generally followed the inherited forecast with a couple of modifications. The first was to adjust lows up slightly in the northeast where cloud cover, in association with the exiting low, could hold on until daybreak Monday. Second, lowered lows slightly in the northwest to bring them more in line with the latest guidance. This led to lows ranging from around 30 in the northwest, to the middle 30s in central and northeastern portions of the CWA. This will facilitate frost across most of the forecast area. Will still forgo any frost/freeze headlines tonight as we are about a week away climatologically from our median date for issuing these products. Finally, after looking at the latest NAM12, HRRR and CONSHORT there is a fog signal in the west tonight. This is co- located with some lighter winds toward daybreak Monday. With this in mind, will insert a mention of fog for the western Sandhills tonight. Monday will be mainly clear with highs generally in the upper 60s to lower 70s. On Monday night, a northern stream disturbance will lift across northern Wyoming, forcing a cool front into the northwestern CWA at 12z Tuesday. The latest NBM probabilistic forecast has a 20 to 40 percent chance of >0.01" of precipitation late Monday night. With this in mind, went ahead and inserted some 20 pops in the far NW after 06z Tuesday. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Issued at 309 PM CDT Sun Apr 28 2024 The cool front will transition across the forecast area Tuesday. Impacts to high temperatures will be greatest across the northern forecast area as the front is not expected to pass through southern and eastern areas until early afternoon. Along the front, precipitation chances will increase with better chances over northern Nebraska where mid level forcing is more favorable. Probabilistic forecasts for measurable (>0.01") precipitation are not great Tuesday and pops were limited to around 30 percent. A second, stronger upper level trough will lift across the northern Rockies Wednesday night into Thursday, leading to the development of surface low pressure over eastern Colorado. A warm front will extend to the northeast of this feature into southeastern Nebraska. ATTM, with this setup, the bulk of severe storms should remain east of the area Tuesday night through Thursday. With the forecast area being north of the warm front and in good easterly upslope was concerned initially about heavy rain potential Wednesday night. The latest WPC outlook has a marginal risk for excessive rainfall generally east of a line from Hayes Center, to Hershey, to Lynch. Current probabilistic forecasts from the NBM only have a 20 to 30% chance of better than a half an inch of rainfall in the marginal risk attm and this lends some doubt as to heavy rain potential Wednesday night/Thursday. Beyond Thursday night, the forecast becomes problematic. The pattern appears to become more zonal into the weekend. This will lead to temps in the 60s/lower 70s. Precipitation chances will be less certain toward the weekend given the zonal mid level flow and no pronounced mid level forcing. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 612 PM CDT Sun Apr 28 2024 The area of MVFR/IFR ceilings and -SHRA/-DZ across the Sandhills and ncntl Nebraska will lift north and east very slowly tonight and Monday morning. Widespread VFR expected across ncntl Nebraska by 18z Monday. Along and south of Interstate 80, VFR should be widespread overnight and Monday except for one potential flight concern. Dry air moving in aloft tonight and light sfc winds may produce patchy valley fog, 3-5 mile vsby, 09z-14z Monday morning. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Buttler SHORT TERM...Buttler LONG TERM...Buttler AVIATION...CDC
Area Forecast Discussion
National Weather Service Marquette MI
643 PM EDT Sun Apr 28 2024 .KEY MESSAGES... - Much cooler today with showers lifting from south to north during the afternoon. - Active pattern continues as three low pressure systems track across the region over the next week. Above normal temps/precip are expected including thunderstorm chances. - Elevated fire weather conditions are possible over the west half of Upper Michigan on Wednesday, but will depend on the preceding precipitation. && .SHORT TERM /THROUGH MONDAY NIGHT/... Issued at 346 PM EDT Sun Apr 28 2024 Upslope/onshore ne winds have lead to chilly temps today (mid to upper 30s) into west and north central portions with even some patchy dz at times into north central portions. Downsloping into the eastern portion of the cwa has allowed temps there to reach into the lower 50s under abundant cloud cover. Water vapor imagery and RAP analysis show a shortwave over the eastern NE and eastern KS that models project will be lifting ne toward the Upper Great Lakes later tonight and Monday. As the associated sfc low pres centered over eastern NE and southern IA lifts nne into southern MN and southern/central WI late tonight, strengthening WAA/isentropic ascent ahead of the system`s advancing sfc-850 mb warm front and increasing transport of Gulf moisture and PWAT values around an inch or more will result in steady showers (now over into the south central UP) to lift north across most of the cwa later this afternoon and evening. In turn, will have categorical PoPs lifting north for widespread showers across the cwa. Models mid-level RH plots hint at dry-slotting reaching into the western UP later this evening and overnight which could result in a break from the steadier showers so have lowered PoPs back to chance over these zones. Overall, from this afternoon through tonight have QPF totals ranging from around a .25 inch over the Keweenaw to more than an inch over se portions of the cwa where best isentropic lift will be focused the longest across the sharp 850 mb thermal gradient along the warm front. Elevated CAPE values of a couple hundred j/kg could lead to isolated t-storms late tonight into se portions, also boosting QPF totals. Expect lows tonight mostly in the mid to upper 30s, except for some lower 40s readings south central and east. Despite a very shallow mixed layer of 1-2 kft off the sfc as depicted on soundings, the arrival of a 45-50 kt LLJ could result in easterly wind gusts approaching near advisory criteria later tonight across the Keweenaw Peninsula, particularly on the downslope westerly side of the Keweenaw. Not enough confidence to issue a wind advisory at this point for the Keweenaw as it looks the higher gusts may be just localized on the western side of the Keweenaw but this will be something to monitor on the evening and mid shifts. The rest of the cwa will see easterly gusts more in the 20-30 mph range. && .LONG TERM /MONDAY THROUGH SUNDAY/... Issued at 445 PM EDT Sun Apr 28 2024 With three different low pressure systems in the extended forecast, there is fairly good agreement in the medium range model guidance for plenty of precip chances. Uncertainty builds in the latter part of the week as guidance begins to diverge ahead of the third low pressure system. The first low pressure system will be ongoing at the beginning of the extended forecast. Starting on Monday, a negatively tilted mid level trough will be situated over the Dakotas/MN state line, extending south into IA with weak ridging over the east U.S. coast and a trough over the Pacific Northwest. The midwest trough pivots over the UP on Monday and the sfc low slowly follows northward behind it. Better q-vector convergence will be located over Lake Superior already Monday morning with a dry slot highlighted in PWATs dropping ~0.2" behind the warm front. This leads to diminishing showers over the west in the morning hours. With increasing PVA in the afternoon, showers are reinvigorated mainly over the west half of the UP. This may be enough forcing to provide some thunder and lightning, however severe weather is not expected. Lingering showers and cloud cover will limit instability with model guidance hinting at ~200-300 j/kg of MUCAPE and mid level lapse rates mainly below 6 C/km. Also, by the time the low level inversion is eroded, the very limited instability will have nearly diminished. The 4/28 0z ECMWF EFI still highlights this period under anomalous QPF with SoT>0 and shaded values to 0.7 to 0.9. Morning showers look to add 0.01" to 0.15" in the west with 0.15" to 0.5" in the Keweenaw and eastern UP. Showers in the afternoon could result in an additional 0.25" in heavier downpours. That said, hydro hazards are not expected. Showers lift north out of the UP Monday night as the trough and sfc low lift over Lake Superior, temporarily bringing dry weather back to the UP for Tuesday. WAA during the day accompanied by clearing skies will bring above normal highs in the 50s near Lake Superior and in the east with 60s in the interior west and south central. Meanwhile, a shortwave will quickly ride east off the Northern Rockies toward the Upper Great Lakes during the day as it takes on a negative tilt and replacing the dry weather Tuesday night into Wednesday as it swings northeast over the UP. While there is some spread yet in the associated sfc low pressure, the general consensus is to take it northeast from MN into northern Ontario, but both GEFS and ECMWF ensembles have members that take the low further to the east over Lake Superior. The ECMWF also is a bit slower with the timing, which would drag precip longer into Wednesday. This means that timing and track still have some uncertainty yet, but a brief round of showers Tuesday night into Wednesday is expected, with better odds over the northwestern UP. Instability again is fairly low (MUCAPE below 100 j/kg), but the support of the cold front moving east across the UP may support a few rumbles of thunder near the WI/MI state line. Dry weather then returns on Wednesday, likely continuing through Wednesday night. Pressure rises behind the cold front and clearing skies will result deep mixing. This will yield warmer than normal temps in the 60s to low 70s and some breezy west winds during the day. Sounding analysis shows the interior west mixing up to around 800-850mb with up to 900mb in the east and the Keweenaw. The last two runs of ECMWF ensemble probabilities of wind gusts exceeding 34 kts were around 20-40% in the west with the 4/28 13Z NBM probabilities around a similar magnitude, except higher to 60% in the Keweenaw. This would also result in lower dew point temps in the west and thus RHs dropping near 25%. The combination of gusts and low RHs would increase fire weather concerns. The limiting factor here is the timing of the previous low pressure system. If the ECMWF solution is favored, precip will linger further into Wednesday resulting in delayed mixing, lower wind speeds, and higher RHs. Uncertainty continues to grow in the forecast Wednesday night onward, but chances for precip increase Thursday with 20-50% PoPs continuing into the weekend as we track out the third low pressure system. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 642 PM EDT Sun Apr 28 2024 An advancing warm front and increasing moisture ahead of low pressure lifting ne through the Upper Mississippi Valley will result in MVFR cigs at IWD and CMX lowering to IFR and as low as LIFR/VLIFR late tonight after widespread rain into the region later this evening and overnight. Lingering LIFR conditions at SAW will continue under steady rain. ENE winds this afternoon will be gusty to around 20kt. At CMX, easterly winds tonight will become sustained at 20-25kt with gusts to 35-40kt possible. LLWS will set in at SAW this evening into the early overnight. && .MARINE... Issued at 445 PM EDT Sun Apr 28 2024 Northeast gales to 35 kt are expected across the western third of the lake this afternoon increasing to easterly gales to 40 kts across most of the lake tonight, continuing into Monday morning. While a few gusts may exceed 40 kts late tonight into Monday, probabilities remain on the low end (25-50%). The strongest winds are expected in the far west as well as the north central portion of the lake between the Keweenaw and Isle Royale where there could be some channeling. The far eastern zone may see a few gale force gusts to 35 kts Monday morning, but confidence was not high enough to issue a Gale Warning for that zone. Gales quickly diminish Monday afternoon as the low pressure moves over western Lake Superior. Significant wave heights up to 14 ft are possible Monday morning between Duluth Harbor to the Bayfield Peninsula and near Isle Royale. Waves fall below 8 ft Monday evening. Winds fall below 20 kts in the west half of the lake Monday evening and after midnight in the east. Winds are then expected to remain mainly below 20 kts through Tuesday. East to south east winds increase to 20-30 kts Tuesday night, becoming west behind a cold front on Wednesday. With stronger pressure rises behind the cold front, west gales to 35 kts are possible on Wednesday over the west half of the lake. Highest probabilities of winds exceeding 33 kts are around 50-75% between the Keweenaw and Isle Royale. Winds quickly return below 20 kts Wednesday night. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Gale Warning until 5 PM EDT /4 PM CDT/ Monday for LSZ162. Small Craft Advisory until 11 PM EDT /10 PM CDT/ Monday for LSZ240-241-247-248. Small Craft Advisory until 11 PM EDT this evening for LSZ242>246. Gale Warning from 11 PM this evening to 5 PM EDT Monday for LSZ242>246-263>266. Small Craft Advisory until 5 PM EDT Monday for LSZ249>251. Lake Michigan... Small Craft Advisory until 11 AM EDT Monday for LMZ221. Small Craft Advisory until 4 PM EDT Monday for LMZ248-250. && $$ SHORT TERM...Voss LONG TERM...Jablonski AVIATION...07 MARINE...Jablonski
Area Forecast Discussion...UPDATED
National Weather Service Topeka KS
615 PM CDT Sun Apr 28 2024 .KEY MESSAGES... - Storms exit to the east this afternoon. - Could be some patchy ground fog Monday morning. - Active pattern with some potential for severe thunderstorms persists for Tuesday through Thursday. && .DISCUSSION... Issued at 218 PM CDT Sun Apr 28 2024 19Z water vapor imagery showed a closed upper low over western NEB. The associated surface low was noted in the obs over east central NEB with a stretching south through northeast and south central KS. Showers and storms along the boundary have been sub- severe thanks to cloud cover preventing much in the way of destabilization ahead of the front. This activity along with the surface front is forecast to be east of the forecast area by 00Z. Clearing skies and diminishing surface winds may allow from some ground fog to develop Monday morning. Forecast soundings from the RAP and NAM have not been that bullish on fog in part to some wind at the top of the boundary layer and drier dewpoints moving in from the northwest. But given recent rains and not much mixing of the boundary layer this afternoon, think the models may be under doing the fog potential. Have only added some patchy fog in the favorable low lying areas for now, but later shifts may need to reevaluate the potential for fog. Monday brings a break from the thunderstorm activity with subsidence behind the exiting wave providing mostly sunny skies. With good insolation have bumped up highs a few degrees with middle 70s expected for most locations. There are signs from the operational models for some weak warm air advection developing Monday evening. Moisture return looks muted so don`t think it will amount to much, but it is something to keep an eye on nonetheless. Better moisture return develops Tuesday and through mid-week. Models are in good agreement with a shortwave passing mainly north of the forecast area into Tuesday evening. While the better dynamics look to stay north of the area, the wave is progged to push a frontal boundary into the area with a narrow axis of CAPE between 2000 and 3000 J/kg developing ahead of the front. Bulk shear of 40KT to 50KT maybe enough for some organized updrafts. So will need to keep an eye on convection late in the afternoon Tuesday and Tuesday night. A moist and unstable boundary layer is progged to remain in place for Wednesday, but forcing for vertical motion is not obvious. Shower and thunderstorm activity could be higher Wednesday night as the low level jet increases and provides some lift for convection to form on. Another frontal system is forecast to move through the central plains Thursday as a more amplified shortwave trough propagates east. There is good agreement in the models with the timing of the front so the NBM has some high POPs with this feature. GFS forecast of 0-6km bulk shear is less than stellar for severe weather, probably due to a relatively weak wind field forecast. But given the time of year we`ll need to monitor this for the severe potential in the coming days. Operational solutions show the deeper moisture getting displaces to the east and south for Friday through Sunday. But the model blend holds onto some small POPs through the weekend indicative of greater spread from the ensembles. Looking at the 500MB cluster analysis from the 00Z runs shows that negative height anomalies could end up anywhere from northern MN to CO. Given the uncertainty, have stuck with the model blend in what is a low confidence POP forecast. This increase forecast spread also tends to smooth out temperature anomalies. But even the operational runs don`t show persistent warm air advection. So temps generally remain mild with readings near or a little above normal. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 613 PM CDT Sun Apr 28 2024 VFR cumulus will continue to scatter out as sunset approaches this evening, while westerly winds become near calm. Given all the recent rain, this may allow for some shallow fog to briefly develop towards sunrise. Confidence in this occurring is still not very high, but is more likely in the typical river valley locations like KMHK and KTOP. && .TOP WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Wolters AVIATION...Reese