####018006784#### FXUS63 KBIS 071451 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 951 AM CDT Tue May 7 2024 .KEY MESSAGES... - Widespread showers are expected across western and northern North Dakota today, with isolated to scattered showers south central into the James River Valley. - A northward moving west to east orientated line of thunderstorms may develop this afternoon north of I94. Severe weather is not expected at this time. - Strong westerly winds are expected along and south of Highway 12 in far southwest North Dakota from mid morning to early evening today. - A transition to warmer and drier weather is expected for the end of the work week and into the weekend. && .UPDATE... Issued at 951 AM CDT Tue May 7 2024 Rain continues over much of the northern half of the state, with rain showers in the southwest. By this afternoon, guidance suggests that a west to east orientated line of thunderstorms may develop. These would most likely develop north of I94 and lift to the north through the afternoon hours. Severe weather is not anticipated at this time, although a strong storm or two is not out of the question. UPDATE Issued at 707 AM CDT Tue May 7 2024 At 700 AM CDT, the center of the surface was located over western parts of the Standing Rock Reservation. Patchy fog has developed to the north and west of the low in southwest North Dakota where an inverted trough is maintaining lighter winds. The fog should lift by mid morning as low clouds fill back in and winds increase. Otherwise, the forecast for today remains on track. && .DISCUSSION... Issued at 430 AM CDT Tue May 7 2024 A stacked low pressure system with MSLP down to 983 mb is spinning over northwest South Dakota early this morning. The mid/upper trough that the low resides in exhibits negative tilt, placing the warm/ moist conveyer belt with a continuous .stream of cyclonic vorticity advection from southern Minnesota curling toward southeast Saskatchewan, the deformation zone with strong upper level divergence over eastern Montana, and a dry slot from southeast and central South Dakota into south central and southwest North Dakota. The low is forecast to slowly drift northeastward into south central North Dakota throughout the day while becoming elongated in a west to east fashion. High- resolution and global ensembles are well- aligned with high chances for rain across northern and western North Dakota this morning and afternoon, with more isolated to scattered shower activity expected south central to southeast. A strong band of low level westerly winds wrapping around the low will clip the far southwest corner of the state today, which is expected to bring advisory criteria winds and gusts to areas along and south of Highway 12. A Wind Advisory has been issued for Bowman and Adams Counties from mid morning to early evening. High temperatures today are mostly expected to be in the 50s, but will likely be limited to the mid to upper 40s in the southwest. The stacked low is forecast to gradually weaken and drift southward later tonight through Wednesday. High chances for lighter rain remain in the forecast for southwest North Dakota through Wednesday afternoon, where some guidance maintains a pocket of enhanced Q- vector convergence. The rest of the state will still see low to medium chances for rain through Wednesday with the continued presence of mid level cyclonic vorticity. There could be some peeks of sun on Wednesday, but it will likely be another mostly cloudy day with slightly warmer high temperatures in the mid 50s to mid 60s. The NBM shows low chances for rain departing all but southwest North Dakota by Thursday morning as a northeast-pointing upper ridge brings anticyclonic flow over the region. This should result in greater sunshine and temperatures finally warming into the mid and upper 60s. A clipper-like system is then forecast to dig into the Upper Mississippi River Valley and western Great Lakes region on Friday. Most of the forcing will lie east of our forecast area, but central North Dakota could see isolated to scattered afternoon showers under the cyclonic northwest flow. Despite the passage of the cold front attendant to the clipper, highs are still expected to reach the mid to upper 60s again on Friday. But as is the case with clippers, a breezy, if not windy day can be expected. Mean ensemble height fields suggest a northwest flow pattern over the Northern Plains this weekend into early next week, with a potential for one or two shortwave passages. Despite this, there is medium to high confidence in temperatures rising above normal for most areas over this time period, with upper 60s to mid 70s for highs and 40s for lows. The NBM maintains a dry forecast for the weekend, with only low chances for showers and thunderstorms returning on Monday. && .AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/... Issued at 707 AM CDT Tue May 7 2024 A low pressure center will continue to spin over western and central North Dakota through the forecast period. Precipitation: Widespread showers are expected to develop across western and northern North Dakota this morning and afternoon, with more isolated to scattered shower activity across south central and southeast North Dakota in the afternoon. A few isolated thunderstorms could also develop across portions of central North Dakota this afternoon. Visibility: Patchy dense fog is possible at KDIK this morning. MVFR to IFR reductions are possible in heavier showers. Ceilings: Parts of south central North Dakota will see VFR conditions early this morning. Otherwise, the overall expectation is for MVFR/IFR ceilings to prevail through the afternoon. Areas from KJMS to KBIS could see an improvement to VFR ceilings this evening, with lower ceilings continuing elsewhere. Wind: Northern and eastern North Dakota will see easterly to southeasterly winds around 15 kts today. South central and far southwest North Dakota should experience lighter and variable winds today due to the proximity of the center of the low. The far southwest corner of the state, primarily Bowman County to KHEI, will see much stronger westerly winds today, with sustained speeds up to 30 kts and gusts to 45 kts. && .BIS WATCHES/WARNINGS/ADVISORIES... Wind Advisory until 8 PM MDT this evening for NDZ043-044. && $$ UPDATE...Telken DISCUSSION...Hollan AVIATION...Hollan ####018011850#### FXUS63 KJKL 071452 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 1052 AM EDT Tue May 7 2024 .KEY MESSAGES... - Our main shower and thunderstorm potential lasts into early Thursday, with a smaller possibility at times through the weekend. - Severe thunderstorms are possible today through Wednesday night or Thursday morning. Large hail and damaging winds are the primary threats, but there is also a risk of tornadoes. Locally heavy rainfall could also lead to isolated flooding. - Above normal temperatures are forecast through Thursday. A cold front should pass late in the week and turn temperatures below normal through the weekend. && .UPDATE... Issued at 1052 AM EDT TUE MAY 7 2024 This morning monitoring upstream radars and a line of convection continues to track eastward across western Kentucky and moving into part of central Kentucky. So far, this activity has been sub-severe and will set the stage for how activity develops this afternoon and evening. Biggest change this update was to increase PoPs with decent agreement on this line of convection pushing across much of the area this afternoon. This warrants at least 60-80 PoPs through the afternoon. Outside of this, we are continuing to monitor the potential for severe weather this afternoon. The better parameter space is more northwest of the area today, but a few strong to severe storms can't be ruled out. However, we will need to see how much recovery we see after this morning convection moves through. This as strong shear moves in, with effective shear this afternoon around 40-50 knots and potential for MUCAPE values increasing into the 2000-3000 J/kg range. This would be enough to organize a few storms if the instability can increase this afternoon. UPDATE Issued at 655 AM EDT TUE MAY 7 2024 Minor adjustments were made based on recent observations and satellite trends. This generally led to lower visibilities and greater coverage of fog initially in the southwest and less coverage/lighter fog in the east under more cloud cover. && .SHORT TERM...(Today through Wednesday) Issued at 450 AM EDT TUE MAY 7 2024 Early this morning, an upper level low was centered over the Dakotas with a broad trough across portions of the western and into the Plains. A shortwave trough moving around the upper low was nearing the mid MS Valley region with a couple of additional weaker shortwaves also rotating around the upper low. At the surface, occluded low pressure was centered over the Dakotas with a triple point working across IA. A frontal zone extended east to north of the OH River to the mid Atlantic coast with the trailing cold front south and southwest to the Southern Plains. Today, the shortwave trough nearing the mid MS Valley should continue east an northeast across the Lower OH Valley region and work into the Southern Great Lakes while the upper low meanders over the Dakotas. The parent surface low should move little over the Dakotas today with a triple point low developing over the Great Lakes by this evening which should reach southern Ontario by late tonight. The trailing cold front should approach the OH Valley tonight. However, surface low pressure should begin to evolve over the Plains on the southwestern extent of this boundary as a more potent shortwave trough rotating around the upper level move across the Four Corners region and into the Plains and Central Conus on Wednesday. The frontal zone in the OH Valley region should lift stall near the OH River while an outflow boundary may linger near the KY and TN and KY and VA border regions. This surface low should reach the mid MS Valley by Wednesday evening. Periods of convection are expected during the period with a warm and rather moist airmass in place. PW should be in the 1 to 1.4 inch range today and much of tonight, though PW should drop to 1 inch or less in the northern two thirds of the area Wednesday morning to early Wednesday afternoon before climbing back to 1 to 1.4 inch range to end the period. Recent convective allowing models are generally consistent with 2- 5km updraft helicity probabilities from the 0Z HREF for where the potential for severe weather later tonight and tonight is greatest. These are greatest north of the Mtn Parkway and along the WV border with the highest probabilities near and north of Interstate 64. 0Z HREF 24 hour probabilities for today and tonight for wind are generally greatest north of the Mountain Parkway and near the WV border. Tornado and hail potential is greatest north and northwest of the region where the strongest winds from a LLJ should be present this afternoon and evening. SPC has the entire region in a Slight Risk with the exception of portions of the far northwest three counties which are in an Enhanced Risk for Day 1. At this time it appears that there are two timeframe where severe storms are most likely, the afternoon to early evening and again overnight tonight. MUCAPE per the 0Z HREF mean should reach generally the 1500 to 2500 J/kg range with bulk shear of 25 to 45KT though these values may climb toward 25 to 50KT by early evening per forecast soundings in the north with effective shear near 50KT. MLCAPE per the RAP should reach the 1500 to 2500 J/kg range with pre convective low level lapse rates of 7 to 8 C/km with mid level lapse rates more meager. Fixed layer STP may reach 1 to 2 if not a bit higher in the more northern and eastern locations with 0-1 SRH of at least 100 to 150 m2/s2 per the 0Z HREF with 0-3 SRH of at least 200 to 250 m2/s2. All indications and CAM signals point toward the potential for a couple of discrete cells with rotating updrafts and all three severe hazards would likely coincide with peak heating, though wind and hail would be possible overnight. Anywhere thunderstorms are repetitious, heavy rain and isolated flash flooding would also be a concern. On Wednesday, a lull in shower and thunderstorm activity is generally expected from the morning to midday behind an outflow boundary that should reach near the VA and TN borders. However, some recovery and instability should develop by the afternoon to early evening, especially in the southwest, where MUCAPE should climb toward 2000 J/kg per the 0Z HREF with 40 to 50KT of bulk shear with effective shear values similar per the RAP. Late Wednesday afternoon to early Wednesday evening mid level lapse rates are likely to be at least marginally favorable for large hail at 6.5 to 7C/km with low level lapse rates of at least 7C/km. 2-5km updraft helicity probabilities from the 0Z HREF are greatest in the southwest portions of the CWA, generally after 19Z or 3 PM EDT. Hodographs have some low level curvature and some length in the southwest as well late in the afternoon and early in the evening. 0-1 SRH Fixed layer STP values there are forecast in the 1 to 2 range per the RAP late in the short term period. 0-1 SRH from the 0Z HREF mean climbs to 100 to 200 m2/s2 in the southwest late in the period with 0-3 SRH climbing to at least 200 to 250 m2/s2. Supercells will again be possible, with perhaps a tendency of more elevated storms further north from the TN and VA borders and a better chance for surface based storms further south. Either way, all hazards appear possible by late Wednesday afternoon or early evening with the severe threat likely increasings the long term period commences. Temperatures will be mild with rather humid conditions in the short term period with highs generally in the low to mid 80s both days with mid 80s expected to more common on Wednesday. Lows tonight should average in the mid to upper 60s. .LONG TERM...(Wednesday night through Monday) Issued at 441 AM EDT TUE MAY 7 2024 The most significant weather of the period is certainly front- loaded, with a Day 2 enhanced svr tstm risk covering almost the entire area which carries into Wednesday night. Mesoscale details will be important for exactly how things pan out, and uncertainty still exists in this regard. However, the larger picture does look ominous. Surface low pressure tracking eastward across the Midwest on Wednesday night will continue to pull warm and moist low level air north northeast into the Ohio Valley. Combined with diurnal heating, CAPE of 1500-3000 J/kg is expected to carry over into the evening (where convection has not occurred and where it is able to advect back into the area). Meanwhile, a positively tilted mid/upper level trough will evolve over the Great Lakes and upper Midwest and provide a veered, brisk west southwest flow of 50+ kts. With ample shear and instability, severe wx should result. As mentioned, the uncertainties involve where/when it occurs and evolves. All severe hazards are on the table, including tornadoes, especially if locally backed low level flow can occur due to mesoscale features. The main severe threat in the long term period is Wednesday night, but thunderstorms could carry over into Thursday, especially early in the day in southeast KY. Forecast soundings, particularly in the NAM, also show a potential for redevelopment in the afternoon. However, instability and forcing will be weaker, with very dry mid-upper levels, which should keep activity more benign and sparse. It will wane on Thursday night with loss of heating and the arrival of significantly cooler and drier air. The aforementioned mid/upper level trough will slowly shift eastward with time. However, impulses rotating around the trough will periodically enhance our shower potential through the weekend. Forecast soundings suggest the thunder potential will be fairly limited, with the best chance on Sunday afternoon, and a slight chance of thunder has been included in our northeastern counties then. By Monday, the trough is lifting out to the northeast and our geopotential heights are rising. With this we should have warming temperatures and dry weather. && .AVIATION...(For the 12Z TAFS through 12Z Wednesday morning) ISSUED AT 710 AM EDT TUE MAY 7 2024 Initial low stratus and fog was affecting several locations and likely was most prevalent in the valleys in the southwest portion of the area where more clearing had occurred. Some initial IFR to below airport min vis and or ceilings are anticipated for some areas, with VFR in a few spots as well. General improvements recovering to MVFR and VFR by 15Z and VFR outside of showers and storms thereafter. Convective activity should ramp back up by around or after 16Z as remnants of convection approaches from the west associated with an upper level disturbance. Another at least brief lull may occurring during the evening, with chances possibility diminishing from southwest to northeast toward 0Z. Additional development over or upstream of the area is possible between 0Z and 06Z. The first round could bring strong to potentially severe storms to portions of eastern Kentucky between 17Z and 00Z, especially north of the Mtn Pkwy and nearer to the WV border. Winds will generally be out of the south to southwest throughout the period generally at around 10KT or less. However, any showers or storms could lead to some higher gusts as they move through. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...DJ SHORT TERM...JP LONG TERM...HAL AVIATION...JP