Area Forecast Discussion
Issued by NWS Nashville, TN
Issued by NWS Nashville, TN
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
446 FXUS64 KOHX 270218 AFDOHX Area Forecast Discussion National Weather Service Nashville TN 918 PM CDT Thu Sep 26 2024 ...New UPDATE... .UPDATE... Issued at 845 PM CDT Thu Sep 26 2024 Hurricane Helene will make landfall shortly SSE of Tallahassee with the latest NHC advisory indicating 130 mph maximum sustained winds. Locally, we are seeing the tropical moisture overspreading the area as it wraps around the upper low centered along the Mississippi River at the TN/AR border. The rain will increase in intensity and coverage overnight with the heaviest swath of rain expected during the morning hours. The 00z CAMS are coming in as I type, but the early indications is that the heavy amounts may setup along the I-24 cooridor. One other area the CAMS are pinging on is the pivot point of the moisture around the upper low. This will be west of I-65 but east of the Tennessee River. As far as rainfall amounts through tomorrow evening, the area will likely see widespread reports of 2-4" with localized amounts of 6". The Flood Watch is in effect until 12z Saturday. As far as the winds, gusts will increase along the Plateau near dawn close to Wind Advisory criteria (40 mph+). Those advisory level winds will spread westward with the focus on locations along and north of I-40. The strong gusts may temporarily slack late in the morning but will increase again in the afternoon as the winds swing back around to the south. The strongest winds during the afternoon will likely be over the eastern third of the area where gusts of 40-45 mph look reasonable. We are still not expecting severe weather with all of this activity tomorrow. In fact, lightning in general will be very sparse. && .SHORT TERM... (Rest of today through Sunday) Issued at 1200 PM CDT Thu Sep 26 2024 Hurricane Helene is the big weather story and will be the main impact on our local wx over the next couple of days. The mid morning update had the center of Helene located 255 miles southwest of Tampa with max sustained winds of 105 mph. Helene is expected to make landfall in the Florida Big Bend region this evening as a large, major Hurricane. The storm will move north then northwest, weakening to a tropical depression as it moves over Middle Tennessee and hangs around late Friday through Saturday. The main impacts for Middle Tennessee will be heavy rainfall possibly causing localized flooding and gusty winds with potential for a few downed trees and scattered power outages. We have our entire coverage area under a Flood Watch and Wind Advisory, both from 7 PM this evening until 7 AM Saturday. Models have remained in pretty good agreement with the general scenario, moving Helene toward Middle Tennessee, interacting with a big cutoff low just to our west. Then the low pressure systems will spin around and merge. A surge of tropical moisture will precede the main center of Helene causing rain to spread quickly across the area later today through tonight. Rain will become heavy at times. As the center of Helene moves closer, winds will increase with frequent gusts of 20 to 30 mph. For rainfall, the heaviest and most widespread rain will occur tonight through midday Friday. During this time, most areas are expected to have 2 to 3 inches of rain with locally higher totals. Additional on and off rain is then expected Friday night through the weekend. Event totals will be mostly in the 2 to 4 inch range with some areas up to 5 or 6 inches. By Sunday, there will be a notable decease in coverage of showers as the low weakens and starts to move out the area. Flooding is expected to be generally localized, impacting roads and low lying areas. Small streams will rise, some possibly reaching bankfull. Main rivers are expected to handle the rainfall without reaching flood stage. For winds, the strongest winds will occur in the early morning hours Friday with another peak late Friday as low center repositions and shifts wind directions from mainly north to mainly south. Generally, the strongest gusts are expected across our northeast half (generally along and northeast of I-24) with some episodes of 40 to 45 mph gusts. Our southwest counties may not reach advisory level, but given uncertainties about the wobbling track, we decided to include all areas in the advisory. Thankfully, parameters for severe storms and tornadoes are looking low thanks to extensive coverage of showers and clouds. Still, the setup is a little unusual and we may have a few pockets of storms this weekend in areas of partial clearing or within heavier rainfall bands. Very low risk, but something to keep in mind. && .LONG TERM... (Monday through next Thursday) Issued at 1200 PM CDT Thu Sep 26 2024 Some straggling showers may occur Monday, then we may have a few showers with a cold front Tuesday. Otherwise the trend for next week is for dry wx with seasonable temperatures. && .AVIATION... (00Z TAFS) Issued at 617 PM CDT Thu Sep 26 2024 Rain from Helene will continue spread across airports tonight with VFR conditions becoming MVFR then IFR/LIFR. Rain and IFR will then continue through the TAF period at airports as Helene rotates around the area. Northeast winds will slowly increase overnight with gusts to 20 knots, then increase further with gusts to 30 knots on Friday while switching around to the southwest. && .PRELIMINARY POINT TEMPS/POPS... Nashville 66 73 63 71 / 100 100 90 90 Clarksville 66 72 62 70 / 100 100 90 100 Crossville 61 69 57 67 / 100 100 60 90 Columbia 63 70 61 69 / 90 90 90 90 Cookeville 63 69 61 67 / 100 100 70 90 Jamestown 63 70 59 68 / 100 100 60 90 Lawrenceburg 63 69 60 68 / 90 90 80 80 Murfreesboro 64 71 62 70 / 100 100 80 90 Waverly 63 71 59 68 / 100 100 90 90 && .OHX WATCHES/WARNINGS/ADVISORIES... Flood Watch through Saturday morning for Bedford-Cannon-Cheatham- Clay-Coffee-Cumberland-Davidson-De Kalb-Dickson-Fentress-Giles- Grundy-Hickman-Houston-Humphreys-Jackson-Lawrence-Lewis-Macon- Marshall-Maury-Montgomery-Overton-Perry-Pickett-Putnam-Robertson- Rutherford-Smith-Stewart-Sumner-Trousdale-Van Buren-Warren-Wayne- White-Williamson-Wilson. Wind Advisory until 7 AM CDT Saturday for Bedford-Cannon- Cheatham-Clay-Coffee-Cumberland-Davidson-De Kalb-Dickson- Fentress-Giles-Grundy-Hickman-Houston-Humphreys-Jackson-Lawrence- Lewis-Macon-Marshall-Maury-Montgomery-Overton-Perry-Pickett- Putnam-Robertson-Rutherford-Smith-Stewart-Sumner-Trousdale-Van Buren-Warren-Wayne-White-Williamson-Wilson. && $$ UPDATE.......Reagan SHORT TERM...13 LONG TERM....13 AVIATION.....Shamburger