


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
137 FXUS62 KRAH 080752 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 352 AM EDT Tue Jul 8 2025 .SYNOPSIS... A weak surface trough will linger over the Middle Atlantic and Carolinas through mid-week. && .NEAR TERM /TODAY AND TONIGHT/... As of 350 AM Tuesday... * A Heat Advisory is in place for the eastern Piedmont, Sandhills, and Coastal Plain for heat indices of 105 to 109. * Although most locations should remain dry today, scattered slow moving wet-downbursts may result in isolated strong to severe wind gusts as well as isolated flash flooding in urban and within the areas of heavily saturated soils from Chantal rainfall. A broad trough draped across the northern Plains through the Great Lakes into the Northeast will gradually sharpen through early Wed morning, but change very little over the Southeast. At the surface, Bermuda high pressure will extend westward into the Carolinas with the sharpening of the Piedmont trough through the afternoon hours. Diurnal heating of the humid airmass over the Mid-Atlantic through this afternoon will result in temperatures rising into the 90s by early afternoon and combine with surface dew points in the low/mid 70s to produce heat indices of 105 to 109 degrees. A Heat Advisory is in place to account for this risk for dangerous heat. Reminder that the heat index represents the feels-like temperature in the shade and doesn`t account for additional stress from direct sunlight when heat stress would develop more rapidly. Drink plenty of fluids and take breaks in the shade or air-conditioned areas if you must be outside during peak heating. The airmass should quickly become weakly capped as moderate to high surface based instability develops with low/mid 70s dewpoints and temps in the 90s. Weak to negligible synoptic forcing will have to rely surface forcing from seabreeze and the sharpening of the Piedmont trough, although convective temperatures may also be breached as well. Isolated deeper convection may still develop in the vicinity of the surface forcing and be capable of primarily strong to severe wet-downburst. Anomalous deep-layer moisture, a deep warm cloud layer of >12k ft, and slow steering winds will also add the risk for torrential rainfall to produce isolated instances of flash flooding. Urban areas and poor drainage locations will be at greatest risk, but also within the footprint of rainfall from Chantal where flash-flood guidance is significantly lower and MRMS Flash Crest-Soil Moisture is still very saturated showing 40 to 80% (only taking 2.5" in 6 hrs to fill basins in the eastern Piedmont). The biggest question mark will be magnitude of background synoptic descent associated the Bermuda ridge in the western Atlantic. This may prevent much more than scattered convection and isolated deep convection due to poor mid-lapse rates and warm temperatures at 850mb. && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... As of 350 AM Tuesday... * Increasing concerns for scattered flash flooding for the NC Piedmont Wednesday afternoon/evening. Convectively amplified shortwaves are expected to ripple through the base of the broad mid/upper level trough Wed and result in weak but gradual H5 heights falls to leak into the Mid-Atlantic Wed afternoon through the overnight period. Anomalous deep layer moisture will gradually increase to around 2" areawide (exceeding the 90th percentile areawide and prime the area for efficient heavy rainfall showers/storms during the afternoon. Although an isolated strong to severe wet-downburst is possible, the greater concerns may be the threat for scattered instances of flash-flooding. HREF guidance suggest weak H5 height falls will trigger numerous to widespread showers and storms with a moderate to strongly unstable airmass, especially over the Piedmont between 18z Wed and 00z Thurs. As mentioned in the near term section, a large portion of the eastern Piedmont remains especially sensitive to flash flooding due to high soil moisture resulting in significantly lower flash-flood guidance where Chantal brought 3-8 inches to locally as much as 11 inches. Latest guidance suggest it would only take 2.5 inches in 6 hours to fill local basins in these areas and the 00z HREF is beginning to highlight 30-50% probabilities of >3" in just 3 hrs from these storms. Additionally, 00z HREF LPMM is highlighting concentrated areas of 2 to 5 inches possible in 6 hours. Now it is important to note that this setup is very different from a tropical system moving through the region. Primarily convective events are difficult to predict where these consecrated areas of higher rainfall will occur and may fall outside of the more sensitive areas altogether. Additionally, these setups more likely result in localized areas of enhanced rainfall rather than large swaths of flash flooding from tropical events. There are still a lot of details to be worked out, but the pattern is there for at least increased awareness heading into mid-week. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 340 AM Tuesday... A mid/upper trough will push east from SE Ontario into southern Quebec on Thursday and Friday, as a pair of shortwaves moves across the Northern and Central Plains. Meanwhile the broad longwave trough will extend south into the TN Valley. Southwesterly flow aloft will prevail over central NC between this feature and a subtropical high centered near Bermuda. This will bring in plenty of moisture with PW values near or exceeding 2 inches. A series of upper impulses and a Piedmont surface trough will combine with the ample moisture and moderate destabilization south of a quasi-stationary front over the OH Valley and northern Mid-Atlantic to result in widespread shower and storm development on Thursday and Friday, maximized in the afternoon and evening. The greatest coverage looks to be on Thursday when POPs are categorical everywhere. Similar to previous days, despite weak shear, there still could be a threat for isolated damaging winds from wet downbursts, and SPC introduced a marginal (level 1 of 5) risk for severe storms on Thursday. The more concerning threat, however, looks to be heavy rain and flooding. The storms should be fairly slow moving with the weak mean flow, and grounds will be saturated due to recent heavy rainfall from Tropical Depression Chantal along with additional expected showers and storms today and tomorrow. Thus the WPC has a marginal (level 1 of 4) risk for excessive rainfall on both Thursday and Friday, with even a slight (level 2 of 4) area over the NC Piedmont where locally very heavy rain just fell from Chantal. Flood Watches may be needed, and additional river flooding will be possible as some points along the Haw, Little, and Cape Fear Rivers are already above or near flood stage. High temperatures on Thursday and Friday will be back down to near normal (mid-80s to 90) with the widespread clouds and precipitation chances, but it will still be uncomfortably humid with widespread dew points in the 70s. The cloud cover will also keep lows on the mild side, in the upper-60s to mid-70s. The longwave trough will push to our east this weekend, turning the mid-level flow more W/NW and bringing in some drier air. The shortwaves over the North-Central US will lift into Canada, and ridging will begin building into the Southeast US especially by Monday. Thus convective coverage should decrease somewhat, but with moderate destabilization and the boundary remaining to our north, along with a continued Piedmont surface trough, scattered showers and storms will still be possible each day. This pattern will result in a slight increase in temperatures but still within a few degrees of normal, with highs in the upper-80s to lower-90s. Lows will be in the lower-to-mid-70s. Heat indices in the low-100s will be possible in the south and east by Sunday and Monday. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... As of 125 AM Tuesday... No major changes with the 06z TAF package as prevailing VFR is expected at all TAF sites with PROB30s for late afternoon storms and associated restrictions. We are watching an area of IFR/MVFR cigs pinned along the NC coast as some guidance suggest a period of SCT to perhaps BKN cigs may lift northward and affect FAY and RWI in the 10-14z window. Mixing after sunrise may additionally result in a short window of MVFR cigs at FAY before scattering/lifting to VFR by mid-morning. Outlook: Scattered storms are expected each afternoon and evening through Fri, as a weak upper trough slowly approaches from the west; greatest coverage through the outlook period may be Wed and Thurs. Early morning fog and/or stratus will also be possible. Storm coverage decreasing a bit this weekend as westerly flow aloft takes hold. && .HYDROLOGY... As of 350 AM Tuesday... River Flood Warnings remain in effect for a few locations across central NC. As of this morning, this includes the following: Haw River at Bynum (although is falling quickly) Little River at Manchester Cape Fear at Fayetteville After coordination with local emergency management, the flood warning was allowed to expire late last night due to slowly improving conditions and receding waters. There still remain a significant amount of road closures as well as several roadways that have been completely washed away. Continue to heed road closures and find alternate routes. Rivers and streams still remain relatively elevated, fast moving, and dangerous for the next couple days. && .RAH WATCHES/WARNINGS/ADVISORIES... Heat Advisory from 10 AM this morning to 8 PM EDT this evening for NCZ007>011-023>028-040>043-075>078-084>086-088-089. && $$ SYNOPSIS...Leins NEAR TERM...Swiggett SHORT TERM...Swiggett LONG TERM...Danco AVIATION...Swiggett/MWS HYDROLOGY...Swiggett