####018004831#### FXUS64 KMRX 041845 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 245 PM EDT Sat May 4 2024 ...New SHORT TERM, LONG TERM... .SHORT TERM... (This evening through Sunday) Issued at 241 PM EDT Sat May 4 2024 Key Messages: Drying trend tonight, then less coverage of showers and storms on Sunday than is occurring today. Discussion: The short wave trough that is over the region will exit tonight, followed by rising heights/short wave ridging on Sunday. Scattered to numerous showers and thunderstorms this afternoon will gradually diminish overnight, but some at least isolated weaker convection will be possible through much of the night. On Sunday the overall environment will consist of minimal shear and modest instability, with MLCAPEs likely to top out between 500 and 1000 J/kg most locations. Given the weak subsidence over our area as the short wave ridging builds in, expect less convective coverage with mostly isolated to scattered showers and storms especially in the afternoon. && .LONG TERM... (Sunday night through next Saturday) Issued at 241 PM EDT Sat May 4 2024 Key Messages: Shower and thunderstorm chances are possible almost every day for the next week. With the strongest and most organized storms likely to occur Wednesday/Thursday. Discussion: By Sunday night yet another shortwave will be moving into the southern Appalachian region, but will lose some of it's power as it flattens out and runs into the more stable atmosphere. This will however be enough to spark off even more showers and thunderstorms, with the greatest coverage and intensity of storms expected during the daytime on Monday as the vortmax moves right over head. Luckily with the almost continuous cloudy conditions we should struggle to destabilize on Monday which will hopefully lead to weaker thunderstorms. However if some sun is able to make it through to the surface we could see pockets of stronger storms. On Tuesday the shortwave should be out of our area, but the rain chances don't completely go away as LLJ begins to increase in strength and move eastward through the Tennessee/Ohio Valleys. Storms that are able to form on Tuesday will have an atmosphere more conducive to organized convection, but again the CAPE looks to remain limited with cloudy conditions. Wednesday and Thursday look to have an interesting set up as the LLJ continues to strengthen and a low moves through the Great Lakes region bringing with it a frontal boundary to the southeast, which will aid in synoptic level forcing across the southern Appalachian region. Wednesday into Thursday still looks to be the day with the best chances to see strong to severe convection with this synoptic set up, and we cannot rule out an MCS moving through somewhere in our area. With that being said we are still 4-5 days out from this event with LOTS of convection and turnover in the atmosphere between now and late next week, so still expect models to change the location and timing of the front/low/jet into next week. Also of note will be the increasing chances to see flooding with all this shower and thunderstorm activity. There will likely be large differences in rainfall totals from county to county by this time next week due to the convective nature of the storms, but we could see several counties get widespread 2-3 inches of rain before Friday. Cannot pinpoint exactly where the heaviest rain will be over the next week, but expect we could see several flood advisories or warnings issued before next weekend. && .AVIATION... (18Z TAFS) Issued at 115 PM EDT Sat May 4 2024 There will be showers and a few thunderstorms around mainly this afternoon/early evening, but timing/location uncertainties abound so for now will carry vicinity and tempo groups to try to capture highest probability times for convection. Will likely see MVFR or lower conditions with any thunderstorms or heavier showers this afternoon, then more widespread MVFR or lower conditions look likely later tonight as lower cigs and fog develop. Should see improving conditions late in the period. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 64 85 66 82 / 30 20 40 80 Knoxville McGhee Tyson Airport, TN 61 82 63 79 / 30 20 30 90 Oak Ridge, TN 61 83 63 79 / 30 30 30 90 Tri Cities Airport, TN 59 79 60 77 / 60 50 20 90 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM... LONG TERM.... AVIATION..... ####018005708#### FXUS63 KILX 041847 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 147 PM CDT Sat May 4 2024 .KEY MESSAGES... - Scattered thunderstorms will develop this afternoon west of Interstate 57, mainly between 3pm and 9pm. The potential severe weather hazards include hail to the size of ping pong balls and damaging wind gusts up to 60 mph. - Confidence is medium that hazardous weather will occur both Tuesday and Wednesday as a pair of disturbances track across the region, bringing periods of thunderstorms. && .DISCUSSION...(emphasis on severe potential through Wednesday) Issued at 141 PM CDT Sat May 4 2024 ********************************************************************* Today's Severe Weather Potential: ********************************************************************* Up until this point, two limiting factors for afternoon convective coverage has been the idea that deep-layer shear is somewhat underwhelming (30 kts or less), and that synoptic forcing atop the cold front is somewhat nebulous. If true, then updrafts may struggle to get organized or struggle to stay organized -- thus limiting the severe risk. However, we have recalibrate our expectations due to a decaying MCV currently lifting across northeast Missouri. MCVs notoriously augment forcing and vertical wind profiles, and it bears watching over the next couple hours. If this feature can hold together as it crosses the mid-Mississippi Valley, then convective coverage should become greater than previously anticipated. A quick glance at the RAP-derived parameter space suggests the mesoscale environment this afternoon will be sufficiently unstable as steepening 0-3 km lapse rates and good solar insolation work to erode convection inhibition. SBCAPE values are now progged to be 2000-2500 J/kg ahead of the cold front; which is a notable increase from yesterday's modeled instability. This all adds up to increased confidence in severe weather coverage this afternoon and early evening in areas west of I-55. The primary severe weather hazards are still hail and wind, and recent HRRR guidance suggests that the latter could be the more formidable feature as cold pools strengthen ahead of the front. Any attendant flash flood risk with storm activity looks low. The 3- hr flash flood guidance in areas west of I-55 is currently between 1.5" - 2.0". When overlaying the HREF 3-hr PMM QPF, this same area only achieves 0.5" - 1.0". It's at least worth noting that recent runs of the HRRR offer a couple localized QPF pockets of 1.75", but any flash flooding that occurs would be the exception and not the rule. Our expectation is still for severe convection to fade after sunset, as the lack of an appreciable LLJ will make it difficult for storms to maintain their punch. ********************************************************************* Tuesday-Wednesday Severe Weather Potential: ********************************************************************* A seasonable and otherwise low-drama forecast has been drawn up for Sunday and Monday, but concern quickly focuses on the convective potential unfolding during the Tuesday-Wednesday timeframe. Global deterministic guidance continues to resolve a synoptic pattern favorable for a multi-day severe weather outbreak, and this signal is reflected in other analogs (CIPS) and machine learning tools (CSU MLP Severe). In a sentence or two, we're monitoring the evolution of what looks to be a deepening upper-level low positioned over the Northern Plains by Monday night, with a strong jetcore nosing into the Mid- Mississippi Valley above multiple shortwaves traversing meridional flow. This combination of strong forcing, strong kinematics, and favorable thermodynamics evolving in deep southwest flow could lead to widespread severe weather within a broadening warm sector. Our confidence at this time is only medium, as we cannot possibly imagine how certain mesoscale processes (convective feedback, debris, outflow boundaries, etc) evolve in time and space. But, the synoptic setup currently being modeled for Tuesday-Wednesday is concerning. When leveraging our 100-member ensemble comprised of the GEFS, EPS, and CMCE to assess a favorable parameter space for supercell development (SBCAPE > 1000 J/kg, SBCINH > -75 J/kg, and bulk shear > 40 kts), we see a 50-70% chance of achieving these conditions on Tuesday in areas along and south of I-72. When looking toward Wednesday, we see probabilities of 50-60% in areas south of I-72. And so while the emphasis appears to currently favor the southern half of our CWA on both days, our confidence is only medium. The severe weather outlook will undoubtedly change in coming days, so do check back. MJA && .AVIATION... (For the 18z TAFs through 18z Sunday Afternoon) Issued at 1241 PM CDT Sat May 4 2024 There is a high chance (>80%) a line of storms will work across the area later this afternoon, impacting TAF sites from west to east for a few hours through early evening. South-southwest winds will swing around to the northwest behind the storms as a cold front sweeps through. Winds could be gusty with storms, but otherwise should range from 10-15 kts through tonight. MVFR ceilings become common late tonight and stick around at most airfields through at least late Sunday morning. NMA && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$ ####018009689#### FXUS61 KAKQ 041848 AFDAKQ AREA FORECAST DISCUSSION National Weather Service Wakefield VA 248 PM EDT Sat May 4 2024 .SYNOPSIS... On and off shower chances are expected this afternoon into Sunday night. Summerlike conditions return to the area for next week with daily chances of showers and storms. && .NEAR TERM /THROUGH TONIGHT/... As of 1015 AM EDT Saturday... Key Messages: -Dreary conditions across the entire forecast area this afternoon with extensive low-level cloud cover and scattered showers. Early this morning, a backdoor front was located south and west of the CWA. While, high pressure over New England was wedging cool, moist air into the Mid Atlc. With the front projected to stay south and west of the area this aftn, expect cloudy and dreary conditions across the area. Latest radar showed sctd showers over wrn and NE portions of the region. Chances for showers will continue through this aftn. But, with the best forcing/lift and moisture remaining to the W, the highest coverage will continue to be over the piedmont. Minimal thunder is expected this aftn, but could have a few rumbles in SW counties this evening. Easterly winds will become breezy E of I-95, esply near the coast, with gusts of 15-25mph. Highs will be cool across far northern portions of the FA. Highs will struggle to even reach 60F. Far southern portions will likely see a few breaks in the clouds and winds will have a slight SE component, allowing for warmer temps in the lower to mid 70s. The gradient between these warmer temps and the rest of the FA will likely be sharp. So, expect most will see cooler highs in the 60s. Showers in the far western counties increase in coverage overnight with lower end chances extending E to the coast. The front will start to move back N overnight, leading to stable if not slightly increasing temps late tonight/early Sun. Lows will be in the lower to mid 50s across the N, and in the lower to mid 60s in the S. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 330 AM EDT Saturday... Key Messages: - Continued unsettled, but warmer, Sunday. - More humid on Monday with showers and storms areawide. The front is expected to lift back N Sunday into Monday, shifting the low-level flow to the S. These factors should act to scour out the dreary conditions seen on Saturday. However, still expecting shower redevelopment in the aftn hours as temps warm into the 70s (and maybe as high as 80) and the residual front and a weak disturbance aloft remains near the area. An early look at some CAMs show that they are not particularly enthusiastic at widespread rainfall coverage, which makes sense given a lack of any focused areas of lift. Lows Sun night in the 60s. Upper heights begin building back N for Monday with high temps warming into the low 80s areawide. Despite the warmer temps, a lee trough is expected to develop in the aftn and evening hours. Combined w/ an approaching shortwave from the OH River Valley, showers and storms are expected to develop over the higher terrain in the afternoon and slide eastward into the evening. Mean LREF CAPE shows ~750 J/KG, but shear looks to be rather weak. Therefore, the severe threat looks relatively low, but cannot rule out a stronger storm or two. Soundings do show a rather saturated atmospheric column (PWATS potentially reach or exceed 1.5"), which could lead to some heavier downpours. Dew points also increase into the mid-upper 60s so the humidity will make it feel more like early summer. Shower/storm activity diminishes inland after midnight, but may linger closer to the coast overnight. Lows remain mild in the mid 60s. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 330 PM EDT Saturday... Key messages: -A summer-like pattern will bring unsettled conditions and above- normal temps. -There is the potential for severe weather mid to late week. An unsettled, summertime pattern takes over through the end of the week. A ridge aloft builds in Tuesday, then weakens slightly starting Wednesday. The GFS and ECMWF both suggest stronger 500mb flow of up to 50 kt by Wed afternoon. Additionally, several waves of weak shortwave energy will pass over the area. As of latest guidance, the strongest of these looks to pass on Thursday ahead of an UL trough dropping into the Great Lakes. A stronger system (i.e. cold front) will then cross the area late in the week. These features along with plentiful daytime heating/instability will allow for daily rounds of showers/thunderstorms. Will be monitoring this time period for severe weather given the support aloft and steep mid- level lapse rates. The CSU Machine Learning Probabilities have picked up on the aforementioned parameter space and suggest at least a slight risk for severe weather on Wednesday and Thursday for the entire area and Friday for southern/southeast areas. Highs on Tues will be in the upper 70s on the Eastern Shore and low 80s W of the bay. Well-above normal temps on Wed/Thurs with the potential for widespread 90 degree highs. Fri looks a bit cooler, but still in the 80s for most. Lows generally in the mid-60s. && .AVIATION /19Z SATURDAY THROUGH THURSDAY/... As of 230 PM EDT Saturday... Degraded flight conditions are expected to continue at the TAF sites from this aftn into Sun aftn, as LIFR/IFR/MVFR CIGs will prevail, along with occasional showers (isolated thunder). There may be MVFR or VFR CIGs at ECG through the period, but the other TAF sites will mainly have IFR or MVFR CIGs. NE or E winds 6-12 kt this aftn, will become SE or S tonight into Sun aftn. Outlook...Sub-VFR conditions expected at times into Mon, due to an unsettled weather pattern. Sctd showers and tstms are expected at all TAF sites Sun aftn through Mon. A warmer, more summerlike pattern returns Tue through Thu, with chances for storms each aftn/evening. && .MARINE... As of 430 AM EDT Saturday... Key Messages: - Small Craft Advisories remain in effect for the Chesapeake Bay and lower James River through late tonight/early Sunday morning. - Small Craft Advisories remain in effect from Parramore Island S to the VA/NC for lingering seas to 5 ft. With yesterday's backdoor cold front now well S of the local area, winds have generally dropped off to 10-15 kt with gusts to 15-20 kt early this morning. However, winds are expected to increase a bit later today through tonight as low pressure lifts NE into the Great Lakes with the sfc high sliding off the coast of northern New England into Atlantic Canada. Will keep the SCAs going for the Bay/lower James for E winds increasing to 15-20 kt with gusts to 25 kt. On the ocean, have extended SCAs through 10 am for now for the zones between Parramore Island and the VA- NC border. This is where seas are still ~5ft, with 3-4 ft seas elsewhere. Depending on the increase in winds later today, these headlines may need an extension. The front lifts back N on Sunday, shifting winds to the SE/SSE. SSW winds return for Monday through the middle of next week (but likely remain sub-SCA). Southerly flow looks as though it will persist through most of next week with the next backdoor cold front possible some time Friday. && .TIDES/COASTAL FLOODING... As of 440 AM EDT Saturday... Key Messages: - Upgraded the northern Neck to a Coastal Flood Advisory through Sunday for widespread minor flooding. - Coastal Flood Statements remain in effect for the bayside of the Maryland eastern shore, with an upgrade to a Coastal Flood Advisory likely for additional rises late Sunday into Monday morning. Tidal departures early this morning average around +1.5 ft across the Bay and tidal rivers. A strong flood tidal current Fri aftn/evening has led to increasing departures into the mid/upper Bay. The pattern of elevated E winds shifting to the ESE to SE by tonight favors going above ETSS guidance across the northern Neck. As such, a Coastal Flood Advisory is in effect in this area for the next 3 high tides through Sunday aftn (an extension through Monday morning will likely be needed). Have maintained a Coastal Flood Statement for the bayside of the MD eastern shore to cover nuisance flooding for the next 2 high tide cycles. Water levels further increase here later Sunday into early Monday with an upgrade to a Coastal Flood Advisory likely as SSE winds will tend to focus the highest departures here by that time. A Coastal Flood Statement is in effect for locations on the west shore of the middle Bay to cover nuisance flooding for the next 2 high tide cycles (this may need to be extended as well). It still appears that other than locally moderate flooding at Bishops Head, this event will peak in minor flood category with the high tide cycle Sunday aftn into early Monday. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...Coastal Flood Advisory until 4 PM EDT Sunday for VAZ075>078. MARINE...Small Craft Advisory until 7 AM EDT Sunday for ANZ630>632-634. Small Craft Advisory until 4 AM EDT Sunday for ANZ638. && $$ SYNOPSIS...TMG NEAR TERM...AM/TMG SHORT TERM...AM/SW LONG TERM...AM AVIATION...TMG MARINE...LKB/JAO TIDES/COASTAL FLOODING...AKQ