Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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
39
40
41
42
43
44
45
46
47
48
49
50
728 FXUS64 KHUN 090922 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 422 AM CDT Sun Jun 9 2024 ...New NEAR TERM, SHORT TERM, LONG TERM... .NEAR TERM... (Today) Issued at 422 AM CDT Sun Jun 9 2024 A regime of light SSW flow in the low-levels continues across the TN Valley this morning, as the region is currently located to the north of a Bermuda high (extending southwestward into the eastern Gulf of Mexico) and to the south of a deepening area of low pressure tracking into the northern Mid-Atlantic states. Aloft, WNW winds in the 30-40 knot range will gradually increase to 40-50 knots by sunrise, as the height gradient contracts between a mid- level ridge centered over the northern Gulf and a 500-mb shortwave trough digging southeastward across the eastern Great Lakes. The remnants of thunderstorm activity (which developed yesterday evening in the vicinity of the surface lows trailing cold front across southern MO) continues to spread east- southeastward across Middle TN and will likely impact the northeastern portion of the CWFA in the 10-14Z timeframe. Although the convection has exhibited a weakening trend over the last couple of hours, brief wind gusts of 40-45 MPH, frequent lightning and heavy rain may accompany this activity. To the northwest of the local area, regional radar data indicates that additional thunderstorms have developed along an axis from southwestern MO into northeastern AR (in the vicinity of a trailing outflow boundary in the wake of the initial MCS). Although this activity will have a similar tendency to spread east-southeastward with time, guidance from the 0Z CAMs suggests that the majority of this convection will remain displaced to our north due to little southward movement of the outflow boundary. Thus, we will gradually decrease POPs through the late morning hours, as a broad coverage of mid/high-level debris clouds will likely have a substantial impact on diurnal destabilization. Later this afternoon, most high-resolution models indicate that scattered thunderstorms should redevelop to our southwest (in the vicinity of a differential heating zone across northern MS), with a more isolated coverage of storms occurring along a frontal wind shift axis dropping southward through western/Middle TN. For this reason, we have indicated a gradual increase in POPs between 21-0Z (and especially across the southwestern portion of the CWFA as storms developing across northern MS may tend to grow into another east-southeastward propagating cluster). Although uncertainty regarding storm coverage during this period remains rather high, mid-level WNW flow of 40-50 knots will support a risk of locally damaging winds and large hail if temps manage to rise into the m-u 80s, supporting CAPE in the 1500-2000 J/kg range. && .SHORT TERM... (Tonight through Tuesday night) Issued at 422 AM CDT Sun Jun 9 2024 We will carry a medium-high (50-70%) POP in the grids early this evening to reflect the potential for both convective regimes (discussed above) to continue for a few hours past sunset, and although POPs begin to decrease after Midnight, a narrow band of showers (and perhaps a few thunderstorms) will accompany the actual cold front as it shifts southward across the forecast area. Present indications are that the front will exit our southeastern zones between 12-15Z Monday, with any lingering shower activity expected to end with its passage. By Monday, afternoon, strengthening NNW winds will advect a cooler/drier Canadian airmass into the region, with dewpoints falling back into the mid 50s as temperatures struggle to reach the u70s-l80s. This will set the stage for a clear and cool night, featuring lows in the m-u 50s early Tuesday morning. Temperatures will exhibit little fluctuation on Tuesday and Tuesday night, with dry conditions continuing as a low-amplitude mid-level ridge translates eastward ahead of a weak southern stream trough tracking east-southeastward over OK/TX. && .LONG TERM... (Wednesday through Saturday) Issued at 422 AM CDT Sun Jun 9 2024 Although specific details remain unclear at this point, most of the global models now suggest that that southern stream trough (discussed above) will travel southeastward into the northern Gulf of Mexico during the first half of the extended period, before evolving into nearly stationary cutoff low on Friday/Friday night. Any northward movement of the low next weekend will likely be dictated by the strength and orientation of a blocking mid-level ridge to its north, which will in all likelihood lie across the TN Valley, providing an extended period of warm and dry conditions that could potentially extend into the first part of the following week. That said, we have included a very low (15-20%) POP across our southeastern counties on Friday and Saturday afternoons, due to a gradual increase in low-level moisture which will translate to a notable increase in CAPE given hot daytime temperatures. Highs will quickly warm into the lower 90s for most valley locations by Thursday/Friday/Saturday, with lows more gradually returning to the u60s-l70s by Saturday morning. && .AVIATION... (06Z TAFS) Issued at 1258 AM CDT Sun Jun 9 2024 Thick layers of mid/high-lvl convective debris clouds will continue to spread southeastward across northern AL early this morning, ahead of an MCS (currently across western TN). Current expectations are that the MCS will gradually weaken as it advances further southeastward into our region, but should largely survive, bringing impacts at the terminals btwn 10-14Z. We have included a TEMPO group during this timeframe to account for MVFR vsby reductions in locally heavy rain, and AWWs may also be warranted for lightning and brief wind gusts of 30-40 knots. Partial clearing is expected during the late morning/early aftn period (in the wake of the morning MCS), with redevelopment of additional but more scattered TSRA possible along a southward- moving cold front btwn 22-02Z. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...70/DD SHORT TERM...70/DD LONG TERM...70/DD AVIATION...70/DD