Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC
Issued by NWS Raleigh/Durham, NC
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
922 FXUS62 KRAH 270613 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 213 AM EDT Mon May 27 2024 .SYNOPSIS... A cold front will approach late today and move through the region Monday night. Dry high pressure will settle into the region toward the middle of next week. && .NEAR TERM /THROUGH TONIGHT/... As of 930 PM Sunday... The severe thunderstorm watch remains in effect until 11 PM for our northwestern counties. Satellite and radar imagery reveals a well- defined MCV northeast of Mount Airy over far south-central VA. As such, the strongest storms are currently along and east of this feature, stretching from the northeast/northwest Piedmont and southwest to just northwest of Charlotte. Based on latest trends, the main severe risk looks to be across the northern and northwest Piedmont. However, a strong line also exists just northwest of Stanly County and this is roughly moving ESE. Damaging straight line winds appear the main risk into late this evening. As the late evening wears on, it is difficult to say how the storms may hold together as they track into the Triangle, Sandhills, and Coastal Plain. Most CAMs have the storms either splitting to the north and south of the Triangle, though this will be something to watch for. Certainly convective inhibition will play a role as the night wears on, limiting overall storm coverage. We do think that the storms should start to dissipate after midnight as the MCV pushes to the east. However, upstream convection currently over MO/IL/KY is forecast to reach portions of the southern Appalachians by early Mon and could reach the Triad toward sunrise, though convective inhibition will keep most activity sub-severe until the better chance comes Mon aftn/eve. Lows should dip into the mid 60s to around 70, with some patchy fog possible. && .SHORT TERM /MONDAY AND MONDAY NIGHT/... As of 316 PM Sunday... There is decently high uncertainty wrt to thunderstorms on Monday. An upstream MCS is forecast to interact with the mountains early Monday morning. Most guidance suggests the mountains should eat this up before reaching our western areas. However, there is will still likely be some ongoing showers (and perhaps a little thunder) through about mid-morning across the western to central Piedmont associated with this decaying MCS. Lingering cloudiness may persist through late Monday morning, however clouds should clear enough in the afternoon to support the development of scattered thunderstorms. The spatial extent for afternoon showers/storms will largely depend on 1) where outflow boundaries set up from the upstream morning convection and 2) where mid-level vorticity/MCV features traverse. The recent RAP runs suggest mid-level features could maximize along and south of the NC/SC border Monday afternoon. It`s therefore not surprising that latest HRRR runs tends to focus late afternoon convection across our Sandhills/Southern Coastal Plains (and moreso active in central SC). Additional weaker perturbations are depicted further north into central VA maximizing over the Chesapeake Bay. As such, some high-res guidance (eg. NamNest, ARW) depict a bit more activity further north across our central to northern Piedmont/Coastal Plain Monday afternoon associated with these perturbations. Any storms that do develop Monday afternoon will have increasing effective shear to work with (up to 30 to 40 kts). As such, severe thunderstorms will be possible with any stronger storms that fire. In fact, guidance is pretty riled up about some stronger mid-level lapse rates (~7.5 to 8 C/km) developing across our far southern areas eastward towards the coast. Additionally, model-derived hodographs, HREF max/min helicity neighborhood probabilities, and model-derived STP values all support the potential for rotating storms (and possible tornadoes) from roughly US-1 east across the inner/outer banks Monday afternoon and evening. Given this potentially juicy parameter space, it`s no shock that the SPC has outlined our area in a 15% probability for severe hail and wind (supported by strong mid-level lapse rate potential), with a smaller area of up to 5 % probability for tornadoes across locations east of Raleigh. The overall mean-layer flow should be strong enough to preclude any widespread flooding concerns, however, can`t rule out isolated urban flash flooding with any heavier downpour. Rain chances should diminish late Monday night into the overnight hours. Persistent swly flow will promote highs in the mid to upper 80s/lower 90s. && .LONG TERM /TUESDAY THROUGH SUNDAY/... As of 155 PM Sunday... By Tuesday morning, a cold front should be along the coastline of the Carolinas or immediately offshore. This should keep a slight chance of thunderstorms in the forecast along the I-95 corridor, but by nighttime, a several day period of dry weather should begin. The front will slowly push east, and a surface high will establish itself over southwestern Ontario Wednesday morning. The high will expand to the southeast through the rest of the week, with the center reaching West Virginia by Saturday morning. An upper ridge along the East Coast will begin to break down on Saturday, and a shortwave could bring some isolated showers across western counties Saturday afternoon/evening, although this scenario is only shown in ensembles and not by deterministic models. A stronger shortwave appears likely to move across the Appalachian mountains Sunday and bring a chance of showers to all locations. Surprisingly, the GFS is showing a decent cap on Saturday and Sunday, so do not have lightning in the weekend forecast. Temperatures will trend downward through the beginning of the period, with highs ranging from the mid 70s to the low 80s on Friday. High temps will then rebound for the weekend, returning into the 80s. Thursday and Friday nights will be the coolest, with widespread lows in the 50s. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... As of 205 AM Monday... Scattered showers have begun to develop south and west of the Triad terminals (GSO/INT) towards CLT and are expected to lift northeast through 09z. Isolated instances of lightning will be possible, but mainly showers are expected at this time. A lull in precipitation is expected from 09-12z. A mature MCS is moving through the lower Ohio and Tennessee Valley and is forecast to track ESE and reach the Triad terminals around 13z. Model guidance suggest a weakening trend as it traverses the mountains and have opted to keep only showers mentioned, but thunder, heavy rain, and gusty winds could certainly be possible if it is able to maintain its strength into the NC Piedmont. Surface winds will become gusty out of the southwest late this morning through the afternoon hours with a redevelopment of showers/storms, some severe, during the late afternoon into the evening hours. Outlook: The first of several cold fronts will move through late Mon night into Tues morning with high pressure building in behind and VFR conditions expected through Fri. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Badgett NEAR TERM...Kren SHORT TERM...Luchetti LONG TERM...Green AVIATION...Swiggett