Area Forecast Discussion
Issued by NWS Mobile, AL
Issued by NWS Mobile, AL
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481 FXUS64 KMOB 131018 AFDMOB Area Forecast Discussion National Weather Service Mobile AL 518 AM CDT Mon May 13 2024 ...New NEAR TERM, SHORT TERM, LONG TERM, MARINE... .NEAR TERM... (Now through Tuesday) Issued at 518 AM CDT Mon May 13 2024 Talk about a frustrating forecast as a rather low confidence, potentially high ceiling, also low floor event is begging to shape up across the area. Severe storms capable of all hazards and heavy rainfall are all on the table this morning through the day today. A lot of moving parts so bare with us here. Synopsis...Broad southwesterly flow will develop over the area as a rather deep upper level low ejects out of the Desert Southwest into the central Great Plains. Ridging is in place across the southern Gulf. At the surface, a warm front is slowly attempting to lift northward and recent surface obs have noted that the boundary is somewhere across coastal southeastern Mississippi into southern Mobile county extending eastward across the barrier islands of the Florida Panhandle. Along this boundary, PWATS will climb to around 1.8 to 2.0 with PWATS south of the warm front approaching 2.25 inches. The lead shortwave is currently pushing its way into the mid south this morning and will quickly lift out of the area by midday. The main trough axis and eventual cold front is expected to move in late this evening and into the overnight hours before clearing the area by Tuesday morning. Honestly the only thing we are truly confident on is that it will rain and there will likely be multiple rounds of rain. After that the rest is just a mess with each part highly dependent on one another. Rain clears out on Tuesday as the upper trough lifts northeast into the Ohio Valley. Multiple hazards could be possible today into tonight. Heavy Rainfall...Heavy rainfall continues to be a hazard of concern, especially across the immediate coastline. The issue is the heavy rainfall threat could be highly conditional on how this morning`s storms evolve and placement of the front. This is leading to a rather low confidence forecast with the potential to be highly impactful. It could also be a nothing burger and it won`t flood at all with both solutions on the table. The overall setup supports somewhere getting whacked with some heavy rainfall, especially along the I-10 corridor where heavy population enters are located. You have the classic setup with high PWATS, warm tropical rain processes, instability, a low level jet perpendicular to the initiating boundary advecting moisture towards the boundary with strong convergence and deep layer flow/shear parallel to the boundary to support training. The main question at play is where the heck this boundary will setup and there continues to be two main scenarios possible. One scenario would be best case scenario with low impacts and a good soaking rain. The second scenario is a little more aggressive with likely significant flooding in some of our more populated areas near the coast. Scenario 1. In the best case scenario for flooding, the warm front in question ends up surging well offshore in the wake of the morning MCS that is expected to bring strong to severe storms. In this scenario the storms help re-enforce the cooler side of the boundary and push the boundary well offshore. While the storms themselves could bring a couple of quick inches of rain to the area, long duration training that would support the higher end heavy rainfall threat looks to move offshore and well we don`t think the Gulf of Mexico cares if it adds a few more inches of rain. A brief respite in between waves likely occurs allowing the first round`s rain to attempt to runoff before the second batch of heavier rainfall moves in overnight. While most of the area would likely see 3 to 6 inches in this scenario with locally higher, it would be spread out over almost 24 hours leading to likely more isolated flooding if any. The good news is that recent trends in guidance have actually trended towards this solution and confidence that maybe we sneak by this event with more of a beneficial rain vs flooding is growing. Scenario 2. The more concerning scenario is if the boundary does not push offshore or stays relatively close to the coast. With low level flow leading to convergence along this slow moving boundary and deep layer flow supportive of training convection, backbuilding storms in the wake of the morning MCS would just continue to push over the same areas for several hours. In this result those 3 to 6 inch totals would quickly expand to 6 to 8 inches possibly higher. We would get no break from the heavier rain inbetween rounds and this could lead to some rather significant flooding. The best chance for this rain would be along the immediate coastline up to about the I- 10 corridor. The one saving grace is we have not seen a ton of rain recently and soil moisture is fairly dry. This will allow our sandy soils to attempt to keep up with heavier rainfall. This may limit the overall impact; however, we all know Gulf Coast rain rates can dump and can quickly overpower the grounds ability to absorb waters. At the end of the day the difference between something much more significant vs. a soggy afternoon will likely come down to a few miles. Despite recent trends, the potential for a higher ceiling has lead us to at least err on the side of caution with the higher totals despite the less impactful scenario looking a little more likely than 24 hours ago. Severe... The severe threat is currently knocking on our door step as a line of storms back by Jackson Mississippi quickly marches eastward this morning. The question with the severe storms is the level of instability that will be available. With the current placement of the warm front still confined near the coastal areas this will likely limit the better severe risk towards the coast as this line of storms approach. However north of the warm front, elevated instability could lead to some larger hail. Observations upstream have also shown wind gusts approaching 45 knots so damaging wind gusts could be possible even north of the boundary. Now things have been moving a little quicker this morning which has helped limit the northward extent of the warm front. Now as this line approaches the boundary near the I-10 corridor this morning this will be an area of concern for a potential tornado or two given better instability and rather impressive shear values. The question is do storms actually make it down to the instability this afternoon. Lastly, gusty winds could be possible well behind the line as a wake low appears to be developing behind the line of storms. This appears to move north of our area this morning, however, northern areas along and north of highway 84 could see some strong winds well behind the cluster of storms and this may need to be monitored throughout the period. BB/03 && .SHORT TERM... (Tuesday night through Wednesday night) Issued at 518 AM CDT Mon May 13 2024 Axis of upper level storm system/trough axis is progged to be aligned from the Mid MS River Valley southward to the central Gulf Coast Tuesday night. There appears to be just enough, albeit weak lift lingering Tuesday night to support only a slight chance of showers/storms over the eastern zones from Greenville AL southward to east of Navarre FL. After midnight, as drier air begins to filter in from west to east and expand, rain chances end over the land zones. The upper trof pivots eastward Wednesday and with the surface front well east and south of the local area along with drier deep layer air in place, rain-free weather is on tap Wednesday/Wednesday night. Low temperatures in the lower/mid 60s interior and lower/mid 70s coast Tuesday night are well above normal. Wednesday night lows, see a lowering trend to a range of 58 to 63 interior to upper half of the 60s coast. Highs Wednesday range mostly 84 to 88. /10 Along the beaches, the rip current risk remains High through mid week. /10 && .LONG TERM... (Thursday through Sunday) Issued at 518 AM CDT Mon May 13 2024 The southern stream remains active going into the medium range. An evolving upper level storm system over TX sends rounds of shortwave energy eastward through a nearly zonal upper flow pattern over the deep south Thursday and Friday. Increased ascent will operate on a signal of deep Gulf moisture return resulting in an increase in showers/storms. There are some indications of yet another heavy rain event possibly setting up to close out the week. As far as strong to potentially severe storms, guidance points to Friday. All depends on position of the warm-front late in the week. Model solutions differ on the evolution of the boundary/warm sector and degree of moisture, lift, instability, and shear. Stalled front may linger near-by into the weekend to keep a mention of a small PoP going. Daytime highs through the period mostly well into the 80s. Exception being Friday where overcast conditions and higher coverage of showers/storms keep highs tapered back, 78 to 83. Lows moderate to well into the 60s interior to lower 70s coast. /10 && .MARINE... Issued at 518 AM CDT Mon May 13 2024 A light to moderate southeasterly flow tonight will persist into the early part of the week as a system approaches the marine area from the west. Increasing onshore flow and building seas are expected during the mid to late part of the week. Scattered to numerous showers and thunderstorms likely early in the week and again late in the week, with locally higher winds and seas near the storms. BB/03 && .PRELIMINARY POINT TEMPS/POPS... Mobile 80 68 86 65 88 64 86 69 / 90 90 60 10 10 0 20 40 Pensacola 79 71 84 71 86 67 85 73 / 80 90 80 10 10 0 20 40 Destin 80 72 82 73 85 69 84 74 / 90 80 90 20 10 0 20 30 Evergreen 75 66 85 64 86 60 88 66 / 90 80 70 10 0 0 10 50 Waynesboro 77 65 86 61 86 60 86 64 / 90 70 50 10 0 0 20 60 Camden 74 65 84 63 84 59 85 64 / 90 70 50 10 0 0 10 50 Crestview 79 66 84 66 88 60 89 66 / 80 90 80 20 10 0 10 30 && .MOB WATCHES/WARNINGS/ADVISORIES... AL...Flood Watch from 7 AM CDT this morning through Tuesday afternoon for ALZ051>060-261>266. High Rip Current Risk from 7 AM CDT this morning through Thursday morning for ALZ265-266. FL...Flood Watch from 7 AM CDT this morning through Tuesday afternoon for FLZ201>206. High Rip Current Risk from 7 AM CDT this morning through Thursday morning for FLZ202-204-206. MS...Flood Watch from 7 AM CDT this morning through Tuesday afternoon for MSZ067-075-076-078-079. GM...Small Craft Advisory from 1 AM to 7 PM CDT Tuesday for GMZ630>632-634-650-655-670-675. && $$ This product is also available on the web at: www.weather.gov/mob