Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
Issued by NWS New Orleans/Baton Rouge, LA
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
509 FXUS64 KLIX 131758 AFDLIX Area Forecast Discussion National Weather Service New Orleans LA 1258 PM CDT Mon May 13 2024 ...New AVIATION... .UPDATE... Issued at 607 AM CDT Mon May 13 2024 All interests over SELA should be alert to future updates and warnings issued today; this includes marine, flight terminals, and inland interests. There has been a concerning trend in model runs mainly from the GFS over the last several days that show a very fast moving MCS type feature(most likely a squall line/wake low) moving either along the coast or just inland entering our area from the west around 6pm today. The GFS was the first to show this but since then, the NAM, Euro and now the HRRR is starting to show this very same scenario. If this is going to actually occur, this feature should begin to develop over south central TX around or just after noon today. One can easily see that development of this system over south central TX around noon then only 6 hours later entering our area(~400 miles) would show this is a very fast moving feature which puts it moving east at around 70mph. The wind speeds associated with this should be 50-60kt but much higher gusts could be entirely possible. The majority of the weather associated with this feature may stay over marine areas. The problem with setting any long fused warnings out at the moment is very dependant on exactly where this forms and how fast it actually moves. Since we don`t know these specifics until after it forms, the timing and placement could be off quite a bit. && .SHORT TERM... (Today through Tuesday) Issued at 324 AM CDT Mon May 13 2024 The upper flow is now supportive and subsequent lower level flows are also lining up to support the training of heavy rainfall. Models did show a very weak system moving through late this morning but this mornings system is a bit earlier than what previous model runs were showing but the main thing is, the system is much stronger than what any model was showing. The second system coming in late today is still expected but we will contend with the first one then start on the next. To show just how large the errors are in the 00z model runs, the HREF has >5% of its members showing >5" rain between 1am and 7am today in an area from Gonzalez to Mandeville. This will not be occurring in that time frame but could later. The area to the north, where the heavy rainfall is actually occurring, this same model has no members showing a chance of getting >5" of rainfall. This is what we expected with all of these models trying to handle mesoscale solutions. They will simply be all over the place. We will choose the models that are closest to where the activity has developed this morning(best initialization). One of these is the NAM Nest. This model develops this area into a line to the NW of the area this morning and swings it into the area well before daylight and slowly sinks it southward. This looks to be the most logical conclusion at the moment, so we will move more along these lines. This model, and the others still bring another system through the area this evening into the overnight hours. This first system could cause some flooding and severe weather issues, but if it does not cause any issues, it will at the very least prime the area ahead of the next. Both of these systems will be capable of flooding rainfall and severe storms. The Flood Watch will remain as this should verify for several locations. Rainfall amounts are still coming in from 3 to 6 inches with the highest of these numbers over coastal Mississippi through 7am Tuesday. Once the second system moves to the east, it will clean the area(clearing skies and stable conditions). This should occur by Tue afternoon. && .LONG TERM... (Tuesday night through Sunday) Issued at 324 AM CDT Mon May 13 2024 The frontal boundary that is helping to cause all of this will have sunk back into the gulf by late Tue. The next upper troughing will then move out into the plains by mid week with sfc return flow forcing this boundary back to the north moving back over the area possibly as early as Thu and this whole thing looks to play out again similar to this event. The first disturbance moves through mid day Thu and may hug the coast. This should be associated with the warm front. The next main system will move along the cold frontal interface as it stalls across the area with an abundance of deep moisture Fri. This is at least one solution, but as one can clearly see with the current system, this will almost surely change several times before we get there. The general synoptic structure looks valid, but we will definitely need to get closer to even think of resolving the smaller scale features. && .AVIATION... (18Z TAFS) Issued at 1252 PM CDT Mon May 13 2024 MVFR to IFR CIGs will prevail through the remainder of the daylight hours. Some breaks to scattered coverage can be expected with the wake of the morning showers and storms, but expect redevelopment of VCTS through the afternoon primarily along and north of I-10/12 corridor. Another complex of strong to severe thunderstorms are expected to move in from the west after 00 UTC tonight with TEMPOs noted for windows of highest confidence of TSRA impacts. However, timing is still somewhat uncertain with exact evolution of these storms. After this line of storms clears the area through 06-09 UTC timeframe, expect SHRA to persist into sunrise in the morning with gradual improvement of CIGS/VIS as the day progresses on Tuesday. && .MARINE... Issued at 324 AM CDT Mon May 13 2024 The first of two systems will move through the area this morning. Some of these storms will impact some of the coastal waters mainly the nearshore waters. A second system will move thorugh this evening to impact a greater portion of the gulf waters. Both of these systems could have strong to severe storms associated with them. Gradient flow winds will be southerly while convective winds will be from the direction of the nearest storm. Basically, wind direction will be all over the compass at times and could be quite strong. Tuesday looks to see these conditions ease but storms could be an issue once again toward the end of the week. && .PRELIMINARY POINT TEMPS/POPS... MCB 65 84 62 85 / 80 30 0 0 BTR 69 89 66 90 / 70 20 0 0 ASD 69 89 66 90 / 80 50 0 0 MSY 72 89 71 89 / 90 50 0 10 GPT 69 87 68 89 / 90 60 10 0 PQL 69 88 66 90 / 90 70 10 0 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...Flood Watch through Tuesday morning for LAZ034>037-039-046>048- 056>060-064>071-076>090. GM...None. MS...Flood Watch through Tuesday morning for MSZ068>071-077-083>088. GM...None. && $$ SHORT TERM...TE LONG TERM....TE AVIATION...TJS MARINE...TE