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FXUS64 KHUN 030752 AFDHUN

Area Forecast Discussion National Weather Service Huntsville AL 252 AM CDT Wed Jul 3 2024

New NEAR TERM, SHORT TERM, LONG TERM

NEAR TERM
(Today)
Issued at 251 AM CDT Wed Jul 3 2024

Tranquil weather across the Tennessee Valley early this morning with only a few clouds present across the area. High pressure centered over the Southern Appalachians will remain the dominant weather feature across the region again today. Strong subsidence from the ridge will suppress any potential for afternoon convection (save for a rogue storm or two), with NBM dropping PoPs below 15% areawide this afternoon. The main story will be the dangerous heat and humidity later today. Ample sunshine will once again warm temperatures into the mid to upper 90s, but dewpoints climbing into the mid to prehaps upper 70s will help to create heat index values in the 105-109 range across much of the region later today. Subsequently, a Heat Advisory will be in effect starting at 18z across the entire region.

SHORT TERM
(Tonight through Friday Night)
Issued at 251 AM CDT Wed Jul 3 2024

We'll get almost no relief from the heat overnight, with temperatures only dropping into the 75-80 degree range. The ridge begins to flatten, but remain centered across the Deep South on Thursday (4th of July). This weakeness in the ridge and the deep Gulf moisture in place will allow for a better potential for afternoon showers/storms (30-50%). Most locations will remain dry, however, even with these pulse storms briefly developing during the afternoon/early evening window. The main story for the 4th of July will be the heat, with mid/upper 90s highs and mid/upper 70s dewpoints creating heat index values between 105-110 degrees over much of the area. Heat index values over 110 are possible across portions of northern Alabama, especially the HSV/DCU/MSL metros. It's possible an Excessive Heat Warning may be needed on Thursday if these higher heat indicies are realized. The Heat Advisory continues tonight and will last through Thursday/Thursday night and the day on Friday.

The center of the high pressure ridge that will bring us the dangerous heat over the next 2-3 days will become squeezed to the SE of the area over the GA/SC/NC coast. Meanwhile, a fairly robust mid/upper trough will swing from the northern Plains into the Great Lakes, with its associated cold front pushing from the mid- Mississippi and lower Ohio Valleys into the Tennessee Valley and Deep South region on Friday. Ahead of the front, appreciable destablization of the boundary layer will take place as temperatures again warm into the mid 90s (with heat index values between 105-109 again). This instability combined with the forcing from the cold front will create an environment favorable for showers and thunderstorms (70-90%), including a few strong storms.
Gusty winds and heavy downpours will be the main threats with the strongest activity.

LONG TERM
(Saturday through Tuesday)
Issued at 251 AM CDT Wed Jul 3 2024

Upper level high pressure will persist over the northern Gulf coast through much of the long term period. Meanwhile, an upper trough over the central CONUS will very slowly begin to shift to the east and northeast over the Midwest, Ohio Valley, and Great Lakes regions early next week. This pattern leaves the Tennessee Valley in a sort of weakness into early next week, with southwesterly flow aloft. At the surface, a cold front looks to enter the Tennessee Valley Saturday morning and meander over the region through early next week.
High pressure looks to build in to the north, with high pressure over the northeastern Gulf of Mexico. With these upper level and surface patterns, expect daily chances of showers/storms from Saturday through Tuesday, especially during the peak heating hours of the afternoon. Generally, chances are low to medium (20-50%) each day with the exception of Sunday where chances are low (15-30%).

We'll be keeping an eye on trends for Monday and Tuesday because model guidance suggests that shear will increase to between 20-30 knots. While model instability values are under 1000 J/kg at this point, it's sufficient for the development of thunderstorms. Overall, what this means is that there is potential for a few stronger storms Monday and Tuesday. Confidence in anything severe is low, but heavy downpours, lightning, and gusty winds are all possible.

As for temperatures, the daily chances of showers and storms may quell the heat a bit this weekend through early next week. Highs on Saturday are forecast to only reach the upper 80s to around 90 degrees, whereas Sunday and Monday it'll be a bit warmer (low 90s).
Then, on Tuesday, highs looks to be similar to Saturday. This will result in heat indices generally in the 90s this coming weekend, then mid 90s to around 101-102 degrees in spots Monday and Tuesday. While these values as a whole are a fair bit below Heat Advisory criteria (105-109 degree heat indices), please remember heat safety if you have outdoor plans. Take breaks in the shade and drink plenty of water!

AVIATION
(06Z TAFS)
Issued at 1240 AM CDT Wed Jul 3 2024

VFR conditions will prevail at each terminal through the period with southerly winds and FEW/SCT decks of Cu developing later in the day.

HUN WATCHES/WARNINGS/ADVISORIES
AL...Heat Advisory from 1 PM this afternoon to 7 PM CDT Friday for ALZ001>010-016.

TN...Heat Advisory from 1 PM this afternoon to 7 PM CDT Friday for TNZ076-096-097.

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