219 FXUS64 KMOB 022058 AFDMOB Area Forecast Discussion National Weather Service Mobile AL 358 PM CDT Sun May 2 2021 .NEAR TERM UPDATE /Now Through Monday/...An upper trof with a slight negative tilt centered near the ArkLaTex gradually weakens while lifting off into the northeastern states through Monday. A vigorous series of shortwaves moving through the base of the upper trof will produce moderate to strong deep layer lift which moves across the forecast area mainly through the evening hours. Another upper trof meanwhile advances from the northwestern states and amplifies while beginning to move into the Plains. In response to this pattern, the surface features are somewhat complex and include a surface low currently located near the Oklahoma Panhandle with a frontal boundary/surface trof extending off to the northeast, and a subtle secondary surface low located over eastern Texas with a warm front extending eastward into the forecast area. The warm front lifts well north of the forecast area this evening as the secondary surface low dissipates. With the vigorous series of shortwaves/moderate to strong deep layer lift meanwhile shifting across the area, this will support likely to categorical pops this evening, after which chance to likely pops follow for the overnight hours. 0-6 km bulk shear values this evening will be around 45 knots with 0-1 km helicity values as high as 200 m2/s2, then shear values gradually diminish overnight. This environment will support the potential for severe storm development, and the Storm Prediction Center (SPC) has maintained a slight risk for the western half of the area with a marginal risk further to the east. The forecast area remains in the warm sector through Monday as the surface low near the Oklahoma Panhandle advances along the Red River valley and another surface low evolves further to the north and moves towards the Great Lakes. A series of generally modest shortwaves move across the area on Monday while MLCAPE values increase to 1500-2500 J/kg, potentially around 3000+ J/kg, with daytime heating. This environment combined with the series of shortwaves, and also some lingering subtle surface boundaries from past convection, will be sufficient to support likely pops across nearly the entire area. 0-6 km bulk shear on Monday will be only around 25 knots with generally low helicity values, so considering the instability values am expecting some strong pulse type storms due to precipitation loading, and cannot rule out isolated severe storm development. SPC has now included much of the area in a Marginal Risk on Monday. Rainfall totals through Monday have trended lower and now look to range from around 0.5 to 1.5 inches. Based on this, have opted to cancel the Flash Flood Watch earlier in effect through this evening for Washington and Mobile counties in Alabama, and Stone, George, Perry and Greene counties in southeast Mississippi. That said, storms will be slow-movers on Monday given the weak shear environment, and this could lead to some flooding concerns which will need to be monitored. Lows tonight range from the mid to upper 60s inland to around 70 at the coast. Highs on Monday range from the lower 80s near the coast to the mid to upper 80s further inland. A high risk of rip currents remains in effect through the period, and also into Thursday morning. /29 && .SHORT TERM /Monday night Through Wednesday night/...Aloft, a shortwave will be progressing over the Ohio Valley on towards the northeast. A deep, longwave trough will also progress into the Plains during this time. This feature will weaken, becoming more of a shortwave that will move across the southeastern CONUS late Tuesday afternoon into Wednesday morning. Generally zonal flow will then set up over the northern Gulf coast on Wednesday. At the surface, a low pressure system will move across Oklahoma and into southern Missouri by early Tuesday morning. A cold front associated with this will also begin traversing the ArkLaTex region by this time. This front will continue to progress southeastward moving off over the Gulf of Mexico sometime Wednesday night. Overall, the unsettled pattern will continue through the short term period. Model guidance indicates a line of showers with embedded thunderstorms moving over the Deep South from Tuesday afternoon through Wednesday as the cold front pushes southeast. Synoptic models show a 70-80 knot upper level jet progressing southeast over the Deep South as a result of the upper level shortwave. This looks to mainly impact our far northwest zones, especially into Wednesday evening. The synoptic models at this time do seem to slow the front down, with it not moving out of the local area until Thursday. This will be monitored. There will be ample instability during the day Tuesday, with 2000- 3000 J/kg SBCAPE and 1700-2100 J/kg MLCAPE. Although, this will decrease substantially into the evening with the loss of daytime heating. Most of the instability will then remain near the coast through the remainder of the short term period. Midlevel lapse rates are modest, ranging from 6-6.6 C/km, but the low level lapse rates range from 6.5 C/km to even 9.5 C/km in spots Tuesday. Though again, these values decrease by the evening. Shear will be meager on Tuesday, as values shown by models are only around 20-25 knots in the afternoon. Although, bulk shear does increase on Wednesday to be between 35-45 knots. In terms of moisture, model PWATs over the local area increase from 1.5-1.7 inches Monday evening to 1.6-2.0 inches by Tuesday afternoon. As the front moves over the area Wednesday evening/night, PWATs will begin to decrease to around 0.7 inches in the northwest to about 1.4 inches in the southeast portion of our area. Ultimately, some strong to severe storms are possible, mainly for the northwestern portion of the local area Tuesday afternoon through the evening. The Storm Prediction Center has outlooked areas generally along and northwest of I-65 in a Slight Risk of severe thunderstorms. In addition, The Weather Prediction Center has issued a Slight Risk of excessive rain for the same areas. Storm total rainfall at this time ranges from around 2 inches over southeast Mississippi and far southeast Alabama to about 1.25 inches over south-central Alabama and portions of the western Florida Panhandle. Locally higher amounts are possible. Chances for showers and storms will then persist into Wednesday, but taper off late Wednesday into early Thursday with FROPA. Highs Tuesday afternoon will be in the lower to mid 80s. Then, highs will be slightly cooler on Wednesday as temperatures are only expected to reach the upper 70s to lower 80s. Lows will be warm Tuesday night, in the lower 70s, due to elevated moisture. With FROPA and incoming drier air from the northwest, expecting cooler lows in the mid 50s to lower 60s Wednesday night. Lastly, a HIGH RISK of rip currents will continue through Wednesday night. /26 && .EXTENDED TERM /Thursday Through Sunday/...An upper level trough over the eastern Conus moves off Thursday into Thursday night, with zonal upper flow moving over the Southeast for the rest of the forecast. A cold front that has moved to the northern Gulf coast moves off to the south in response, along with any residual precipitation along and south of the coast. A drier and somewhat cooler air moves south across the Southeast, but after surface high pressure moves over and east of the Southeast, onshore flow returns to the forecast area Saturday. Temperatures will initially see a downward trend, with overnight low seeing the greatest downturn. Low temperatures in the 50s are expected Thursday and Friday nights. Temperatures then begin to nudge upward as moisture levels increase and the airmass moderates. 60s return by Sunday night. High temperatures in the upper 70s to low 80s are expected Thursday and Friday, increasing to low to mid 80s by Sunday. Upper level shortwave energy will pass just north of the area Sunday, bringing a small chance to the forecast area. /16 && .MARINE...Have continued with a Small Craft Advisory for the open Gulf waters until 18Z Monday with Small Craft Exercise Caution wording for much of the bay waters. A cold front approaching from the west will move through the marine area Wednesday afternoon into Wednesday evening with a light to moderate northwesterly flow in the wake of the front. /29 && .MOB WATCHES/WARNINGS/ADVISORIES... AL...High Rip Current Risk from 7 PM CDT this evening through Thursday morning for ALZ265-266. FL...High Rip Current Risk from 7 PM CDT this evening through Thursday morning for FLZ202-204-206. MS...None. GM...Small Craft Advisory until 1 PM CDT Monday for GMZ650-655-670- 675. && $$ This product is also available on the web at: http://weather.gov/mob