774 FXUS64 KBMX 060915 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 415 AM CDT Sat Apr 6 2019 .SHORT TERM... Today and Tonight. The stalled frontal boundary that was near the coast has begun to lift northward as a warm front early this morning as low-level southerly flow develops ahead of troughing over the Plains. The front is currently located along the I-85 corridor. A few scattered showers are ongoing south of the warm front. Areas of fog are noted south of the forecast area with more patchy development across Central Alabama where low stratus has not yet developed. The most widespread fog will probably remain south of the area but will continue to monitor. At upper levels, split flow remains in place over the CONUS. A southern stream trough is centered near the Four Corners region with ridging over the Southeast. A shortwave will eject out of this trough and lift northward towards Kansas City by this evening. Closer to home, a moist air mass will advect into the area along and south of the warm front. Warm air advection/isentropic lift and daytime heating will result in showers developing along and south of the front this morning, with thunderstorms expected by afternoon in an axis of 1.5" PWATs. This should overcome the broadly anticyclonic mid-level flow/weak height rises, aided by some weak waves in the southwest flow aloft that locally flatten the ridge. Temperatures warming into the upper 70s to near 80 and mid to upper 60s dew points will result in SBCAPE values of 1500-3000 J/kg and MLCAPE of 1000-2000 J/kg, supportive of strong updrafts. Steep mid-level lapse rates in excess of 7 C/km associated with an EML will advect into the region, with forecast soundings indicating fat CAPE profiles and WBZ heights around 10k ft which will support hail production. Some dry air aloft and DCAPE will also be present resulting in potential for gusty to locally damaging winds. 0-6 km bulk shear values are only around 20-25 kts this afternoon which will result in storms being of the pulse/multicell variety. While this limits the potential for organized severe storms this afternoon, some isolated severe storms capable of producing large hail/damaging winds will be possible, and have added an areawide marginal risk to the HWO. Also, with many outdoor activities going on today, be mindful of the potential for frequent lightning with these storms. Additionally, the current clusters of storms in West Texas will continue to move east-northeastward through the day, aided by the shortwave trough. While the strongest MCS activity still looks remain northwest of the area, CAMs/HREF members suggest that some more organized clusters could reach the northern counties this evening, with a main threat of damaging winds. There's still some spread regarding the exact track of these clusters, but if confidence increases later today, it's possible that some of our northwest counties could be upgraded to a slight risk depending on whether upstream/mesoscale trends support a more organized threat. Overall timing of the event will favor the southern half of the area during the afternoon and the northern half of the area during the evening. Activity should decrease in coverage after midnight as drier air moves in aloft. 32/Davis .LONG TERM... Sunday April 7 through Sunday April 14. The southern stream trough will only slowly move eastward across Texas on Sunday, as it will be cut off from the stronger westerlies of the northern stream. Dry air will be present at mid-levels, with 850-700mb mean RH values falling below 50%. This combined with the influence of ridging over Florida suggests that diurnal convection will be largely suppressed during the day on Sunday, so PoPs have been lowered. But will need to monitor for any outflow boundaries from a potential convective complex developing near the Delta region of Mississippi. Highs will be in the low to perhaps middle 80s. Rain chances will begin to return Sunday night as height falls develop ahead of the trough and a surface low begins to develop over the ArkLaTex. An MCS is likely to form over Louisiana. Models seem to be trending towards this MCS being more north-south oriented rather than oriented along the coast. It appears that this MCS will move into our western counties after midnight Sunday night, and more likely after 3 AM. Severe potential with this MCS is unclear, but appears to be very limited with weaker instability during that time of the day, and it will be displaced eastward of the better forcing. Therefore, confidence is too low to mention any severe storms for late Sunday night at this time. This potential MCS will likely play a large role in determining any severe weather potential for Monday. The most likely scenario appears to be that it would move through during the morning hours, possibly posing a marginal threat of severe weather, and contaminate the warm sector and decrease the mid-level lapse rates, limiting the potential for air mass recovery and preventing more than a marginal risk of severe weather with new storms developing along the cold front further west within a mid-level dry slot. However if it weakens or dissipates, or if enough daytime heating occurs behind it then a greater risk for severe storms could materialize. For now, the best course of action appears to be to add an areawide marginal risk of damaging winds to the HWO for Monday with a broad time window, and monitor for any potential upgrades. The tornado potential for Monday is unclear as models have varied from run to run and between each other regarding the magnitude of both deep layer and low-level shear. For example, yesterday's runs of the ECMWF had a stronger surface low while tonight's run trended weaker. The low also appears to be vertically stacked. So, will hold off on mentioning a tornado threat in the HWO at this time. Ultimately there will be several rounds of convection across the southern CONUS between now and then which will determine what kind of environment is present by then. Rain chances will linger into Tuesday as the vertically stacked low swirls overhead. A rumble or two of thunder will remain possible given cool air aloft. The system finally moves eastward with dry conditions expected for Tuesday night and Wednesday. A potent shortwave trough will reach the central CONUS by Thursday. A powerful 985mb surface low will bring the potential for a significant late season winter storm for the Upper Midwest. Closer to home, moisture return will be limited with dew points barely reaching 60F. Warm air aloft will also result in some capping. The strong wind fields will probably result in a strongly forced squall line developing from the Great Lakes southward Thursday night. This could result in a damaging wind threat across our northern counties depending on the southern extent of the squall line, but it remains unclear whether or not it will reach this far south. The GFS is more aggressive than the ECMWF with a frontal passage into the Gulf behind this system. This will likely play a role in moisture quality for a potential threat for severe storms with another system next weekend as the pattern remains active, but confidence in any details remains low at this time. 32/Davis && .AVIATION... 06Z TAF Discussion. MVFR/IFR conditions in the south along and south of the warm front. Will see that front work slowly north and will result in scattered showers and storms this afternoon and evening. Added in prob30 for the best time frame at each site and will likely need to add into the time frame with the next set at 12Z 16 && .FIRE WEATHER... Low clouds will be in place this morning, as a warm front slowly lifts northward through the area. North of the front, patchy fog is possible through the morning. Scattered showers and an isolated thunderstorm is possible south of the front. The front will stall across the area and be the focus for shower and storm development tonight and through the weekend. Moisture and rain chances remain elevated through Monday. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 79 60 82 62 74 / 40 30 30 60 80 Anniston 78 61 82 62 75 / 40 40 30 60 80 Birmingham 80 64 83 64 76 / 40 40 30 60 80 Tuscaloosa 80 64 82 65 77 / 50 50 40 70 80 Calera 78 62 81 64 74 / 50 50 30 60 80 Auburn 76 62 80 63 74 / 60 50 30 50 80 Montgomery 80 63 84 64 77 / 60 30 20 50 80 Troy 79 62 83 64 77 / 60 20 20 40 80 && .BMX WATCHES/WARNINGS/ADVISORIES/... None. && $$