Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
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
445 ACUS01 KWNS 160557 SWODY1 SPC AC 160556 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1256 AM CDT Mon Sep 16 2024 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN PLAINS... ...SUMMARY... Thunderstorms capable of severe gusts and large hail are expected today in parts of the northern Plains. An isolated tornado threat is expected in the Carolinas. Marginally severe wind and hail may occur in parts of the Four Corners and Intermountain West. ...Northern Plains... Southwest mid-level flow will be in place across the north-central U.S. today. A shortwave trough is forecast to move across North Dakota this afternoon. At the surface, a low will deepen across southeast Montana as a warm front moves northward across central and eastern North Dakota. Surface dewpoints near the front will be in the mid to upper 60s F and moderate instability is expected to develop by afternoon. The front will be a focus for convective initiation from late this morning into the afternoon. RAP forecast soundings near the front in east-central North Dakota have 0-6 km shear in the 30 to 35 knot range with some directional shear in the boundary layer. Mid-level lapse rates are forecast to be between 7.5 and 8 C/km. This environment should support supercells with severe gusts and large hail. The event will be driven by mesoscale processes, and the greatest severe threat coverage will likely be located in areas where the maxima in low-level convergence, instability and deep-layer shear become juxtaposed. The severe threat may ramp up during the early evening as a 40 to 50 knot low-level jet strengthens across the northern Plains. ...Eastern North Carolina/Far Eastern South Carolina... A low pressure area off the coast of the Carolinas is forecast to become a tropical storm by the National Hurricane Center and move northwestward into far eastern South Carolina this evening. RAP forecast soundings to the right of the expected landfall at Wilmington, North Carolina have 0-3 km storm-relative helicity increasing to around 150 m2/s2 by early evening with 0-1 km shear reaching the 20 to 25 knot range. This should support an isolated tornado threat as the tropical storm moves inland this evening. This threat may continue into the late evening and overnight along the coast of North Carolina, where moderate instability is forecast. ...Four Corners/Intermountain West... An mid-level low will move northeastward across the Intermountain West today. Ahead of the system, a band of strong large-scale ascent will aid thunderstorm development from the Four Corners region northwestward across parts of Utah. Scattered storms will likely develop and move northeastward across the region during the afternoon. Although instability will remain weak, very steep lapse rates and strong deep-layer shear may support an isolated severe threat. Marginally severe wind and hail will be possible with the stronger cells. ..Broyles/Weinman.. 09/16/2024 $$