Area Forecast Discussion
Issued by NWS Birmingham, AL
Issued by NWS Birmingham, AL
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723 FXUS64 KBMX 270225 AFDBMX Area Forecast Discussion National Weather Service Birmingham AL 925 PM CDT Sun May 26 2024 ...New SHORT TERM, AVIATION... .SHORT TERM... (Tonight through Tuesday) Issued at 838 PM CDT SUN MAY 26 2024 KEY MESSAGES... -Severe thunderstorms including tornadoes, damaging winds, and large hail are possible overnight. The best chance north of I-20 after 2 am. -Severe thunderstorms possible again on Memorial Day, mainly in the afternoon and evening. The main threats will be damaging winds and large hail. It appears the tornado threat lessens with time as the storms move from north to south. Monitoring the severe thunderstorms developing north across the Ohio Valley this evening. Some activity is just beginning in the Missouri Bootheel with hints of additional development in northern Arkansas. Hi Res CAMS are starting agree with the timing of after 2am for northwestern areas near Hamilton, with potential isolated development ahead of a more organized line. Bulk Shear values around 60kts will be more than enough for organized storms. 0-3km SRH values 200-300 in spots, SBCAPE 2000-3000 in spots while hodographs support tornadoes late tonight. Therefore, will hold the timing and threats as they are. Please have multiple ways to receive watches and warnings especially during the overnight hours. Some differences appear in the model output and ultimate evolution of the storms during the morning hours on Memorial Day. Some weakening is expected as the storms enter the I-20 corridor and then re-intensification with chances of severe after noon, though Bulk Shear decreases. The biggest questions at this time are the where storms start re-intensification or if they weaken at all and storms continue from overnight and exit quicker to the southeast. This will have an effect on how large an area has a severe risk. The only thing that does look fairly agreeable is that the winds veer with time and the tornado threat should decrease with time. At any rate, be aware of the possibility of severe thunderstorms especially with outdoor activities on Memorial Day. No significant changes to the ongoing forecast and overall message. 75 Previous short-term discussion: (This evening through Monday) Issued at 1228 PM CDT SUN MAY 26 2024 Tonight, the environment will become better prepped for storms ahead of a cold front expected to move through the area on Monday, with the main area of increasing instability, PW, and shear across the northwestern third of the state, closer to that front. A line of storms is expected to move east and southeast overnight into the early morning on Monday. While the storms move through northwestern Alabama, PW values will be around 2 inches, which is well above max for this time of year, with instabilities between 2500 and 3000 j/kg. 0-6 km shear will be very strong, values up to 80 kts showing on several models across the northern most counties, and 0-1 km shear around 30 kts. The storms along this line may stay strong to severe as they move into the northwestern counties of Central Alabama around 2 am Monday morning, and then as they move southeast. Damaging winds and large hail will be a threat, and with the amount of wind shear present, a tornado is possible. As the line moves to the east and south, instabilities should quickly decrease, and shear should weaken through the morning. While storms could remain strong, the severe threat will greatly diminish by the time the storms reach the I20 corridor. Areas south of I20 may see a strong storm if the line can move into the area faster Monday morning, otherwise, these areas will see scattered showers with a few isolated thunderstorms. This area of activity should be east of the area by around 8 am Monday morning with the rest of the morning and early afternoon remaining dry. The afternoon on Monday brings lower confidence. Almost all CAMs, (outlier is the HRRR) show a lack of convection developing through the afternoon. Wind shear decreases greatly, and PW values begin to decrease through the afternoon as the frontal boundary moves from northwest to southeast through the afternoon on Monday. Due to a combination of morning activity across the northern half of the state, as well as drier air moving quickly into these areas from the northwest, would expect decreasing chances for severe storms across the northwest through the afternoon. However, instabilities across the southeastern half of the state will be between 3500 and 4000 j/kg and LI values around -9. Wind profiles show very little strength or turning, though upper level dynamics show divergence aloft. Right now will advertise severe thunderstorms with damaging winds and large hail the main threat. If storms can develop and tap into the right combination of instability and forcing, severe thunderstorms seem to be a given. Though models are pessimistic as to much if any coverage across most of the area. In areas south of I85, there does appear to be decent consensus of a line of storms developing in the mid to late afternoon, lasting through the evening. With instabilities so high, will expect a greater chance for strong to severe thunderstorms in these areas. 24 && .LONG TERM... (Monday night through next Saturday) Issued at 402 PM CDT SUN MAY 26 2024 The main changes to the extended are that guidance is indicating a faster exit of the system out of C AL on Mon evening. So, although we are still thinking that there is a severe risk on Monday, storms will likely only still be around in the far SE counties to have risk by Mon evening in 0-3z timeframe. If faster trend continues, this timing may need further adjustments on the mid shift. Otherwise, added some minor isolated heat of the day pops for Wed/Thu in a few spots, but nothing big. More significant rain chances return by next weekend with the approach of an upper system into the SE US. 08 Previous long-term discussion: (Monday night through next Saturday) Issued at 340 AM CDT SUN MAY 26 2024 The frontal boundary should be moving through Central AL Monday evening/night, continuing to support strong to severe storms for a few hours Monday evening before exiting to our southeast before midnight. Drier weather expected Tuesday through the end of the week. Some guidance tries to hint at a few waves moving through the ridge to our west Wednesday into Thursday, but confidence isn`t there to included in the forecast at this time. Most indications are that the low level ridge that builds in across the deep south suppresses much of the thunderstorm activity under the northwesterly flow aloft. As we approach next weekend, the ridge slowly slides to our east, allowing a few shortwaves to slide through to our north, which will lead to increasing rain/storm chances Friday night through Saturday, but timing of these waves is highly uncertain and the forecast is likely to change in coming days. 25/Owen && .AVIATION... (00Z TAFS) Issued at 838 PM CDT SUN MAY 26 2024 VFR conditions will exist through 06-08z for most terminals. Then the conditions will begin changing. Lower ceilings/vis begin affecting the southern MGM/TOI after 06z while some lower ceilings and rain chances enter the picture north after 08z. Thereafter, showers and storms will traverse from north to south through the period. The specific evolution of the storms will need to be refined at a later time and added to the terminals. Right now, mentioning PROB30 thunder and MVFR/IFR ceilings. Winds will increase overnight and be south to southwest around 10kts. Some gusts are possible at times to around 20kts outside storms. 75 && .FIRE WEATHER... Scattered showers and thunderstorms are expected again late tonight into Monday. 20 foot winds will be from the south to southwest at 6 to 12 mph today. Min RH values will in the upper 40s or above 50 percent through Monday, with overnight recoveries near 100%. Drier air builds in Tuesday with only isolated convection possible for Tuesday and Wednesday with afternoon heating. && .PRELIMINARY POINT TEMPS/POPS... Gadsden 69 88 61 88 / 60 40 10 0 Anniston 71 88 63 87 / 40 40 10 0 Birmingham 72 90 65 88 / 50 30 10 0 Tuscaloosa 72 91 65 90 / 50 30 10 0 Calera 73 90 65 89 / 40 30 10 0 Auburn 72 86 67 87 / 0 50 20 0 Montgomery 74 90 67 90 / 10 50 20 0 Troy 72 89 68 90 / 0 50 30 0 && .BMX WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...75 LONG TERM....08 AVIATION...75