textproduct: Charleston

WHAT HAS CHANGED

Overall minimal changes, slightly higher chances of precipitation Monday than previously forecast.

KEY MESSAGES

1.) Elevated fire weather conditions are expected this afternoon across the lowlands as southwesterly wind gusts of 20 to 25 mph overlap with a mix of extremely dry dead vegetation and increasingly dry live fuels.

2.) Unseasonably hot and dry conditions will persist through the work week under an amplified upper level ridge. Temperatures will run 15 to 25 degrees F above normal, challenging daily records.

3.) Mild overnight temperatures are expected tonight and through the week. Persistent southwesterly flow will limit typical valley radiational cooling and fog development.

4.) Isolated to scattered afternoon showers and thunderstorms are possible each day, but widespread wetting rainfall is not expected. Drought conditions will likely worsen.

DISCUSSION

KEY MESSAGE 1...

A warm front has lifted north of the area this afternoon, placing the region squarely in the warm sector. Strong diurnal heating has allowed for deep boundary layer mixing. Regional soundings and objective analysis indicate a dry airmass in place, with surface dew points mixing out into the low 40s to mid 50s. Combined with temperatures soaring into the low to mid 80s F across the lowlands, minimum relative humidity values are dropping into the 20 to 30 percent range. Furthermore, this deep mixing is tapping into a modest low level jet, transporting momentum to the surface and resulting in southwesterly wind gusts of 15 to 25 mph. Relative humidity values will be higher tomorrow, especially across the northern half of the are where some very light rain is possible. Farther south, where little, if any rain is expected RHs should bottom out in the low 30s again with renewed gustiness Monday. While lowland forest floors are becoming increasingly sheltered, without precipitation or significant and persistent RH recoveries, fine dead fuels remain very receptive to fire. This is somewhat tempered by increasingly mixed live/dead fuels as the green up continues.

KEY MESSAGE 2...

An anomalously amplified and stagnant long wave pattern will dominate the eastern half of the country through the upcoming week. A strong H500 ridge axis remains anchored off the East Coast, maintaining persistent southwesterly flow across the Ohio Valley and Appalachia. This setup will yield a prolonged period of summer-like heat. High temperatures will consistently reach the mid to upper 80s across the lower elevations, which is 15 to 25 degrees above normal climatological values. Several daily high temperature records may be threatened over the next few days.

KEY MESSAGE 3...

Unlike typical quiescent weather patterns in the complex terrain of Appalachia, the persistent southwesterly boundary layer flow will preclude the development of sharp nocturnal valley inversions tonight and through much of the week. Without this decoupling and subsequent cold air drainage, overnight lows will remain quite mild, generally bottoming out in the upper 50s to low 60s. This persistent flow will also largely inhibit the formation of dense river valley fog that is otherwise common under strong high pressure.

KEY MESSAGE 4...

The region will remain in the open warm sector for the duration of the work week. A steady, albeit weak, moisture feed from the Gulf will gradually increase low level moisture over the next few days. With the H500 ridge centered to the east, the primary storm track will remain displaced to the northwest. However, weak shortwave energy embedded within the southwesterly flow aloft will periodically ripple across the area.

These subtle impulses, combined with daytime heating, will support daily chances for isolated to scattered showers and thunderstorms, primarily during the afternoon and evening hours. The thermodynamic environment will feature MLCAPE values gradually increasing to around 500 to 1000 J/kg by mid-week. However, deep layer shear remains notably weak, generally less than 20KTs, which will favor disorganized, pulse-type multicellular convection. The severe threat remains low.

Overall precipitation amounts through the week will be heavily dependent on where isolated convective cores track. Guidance interquartile ranges suggest basin-averaged totals will be rather meager, generally half an inch or less across the northwest counties and less than a quarter inch across the southeast. Given the highly localized nature of any heavy downpours and the exceptionally dry antecedent soil conditions, flash flooding is not anticipated. The lack of a widespread, organized wetting rain will offer little relief to the region, and fire weather concerns will need to be monitored daily as fine fuels continue to dry.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

VFR conditions will largely prevail through the 18Z TAF period. A warm front has lifted north of the terminals, establishing a warm and dry southwesterly flow. Scattered high based cumulus with cloud bases around 5000 to 7000 ft AGL will continue this afternoon before dissipating with the loss of daytime heating. Southwesterly surface winds of 10 to 15KTs with gusts of 20 to 25KTs are expected through 23Z.

Tonight, surface winds will diminish to 5 to 10 KTs as the boundary layer partially decouples. However, a 30 to 40KT southwesterly low level jet will remain positioned just off the surface. This will result in a period of low level wind shear at most terminals overnight, generally between 05Z and 13Z Monday.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z MONDAY... FORECAST CONFIDENCE: High. ALTERNATE SCENARIOS: None. EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.

UTC 1HRLY 17 18 19 20 21 22 23 00 01 02 03 04 EDT 1HRLY 13 14 15 16 17 18 19 20 21 22 23 00 CRW CONSISTENCY H H H H H H H H H H H H HTS CONSISTENCY H H H H H H H H H H H H BKW CONSISTENCY H H H H H H H H H H H H EKN CONSISTENCY H H H H H H H H H H H H PKB CONSISTENCY H H H H H H H H H H H H CKB CONSISTENCY H H H H H H H H H H H H

AFTER 18Z MONDAY... VFR conditions will generally prevail through the work week. However, brief periods of MVFR to IFR restrictions are possible within scattered showers and thunderstorms.

CLIMATE

Persistent, anomously warm conditions are forecast through much of the week with several days of near or record highs.

Forecast / Record High Temperatures ------------------------------------------------------------------------ Sun, 4/12 | Tue, 4/14 | Wed, 4/15 | Thu, 4/16 | ------------------------------------------------------------------------ CRW | 86 / 92 (1930) | 85 / 88 (2018) | 88 / 89 (1994) | 86 / 89 (2002) | HTS | 87 / 92 (1930) | 86 / 87 (1941) | 89 / 87 (2024) | 85 / 89 (2024) | CKB | 81 / 88 (1930) | 81 / 87 (2018) | 85 / 83 (1974) | 84 / 86 (2002) | PKB | 83 / 88 (1930) | 85 / 85 (1941) | 87 / 84 (2024) | 85 / 88 (2002) | BKW | 78 / 80 (1916) | 80 / 83 (2018) | 83 / 82 (2012) | 81 / 84 (2002) | EKN | 79 / 82 (1930) | 80 / 85 (2018) | 85 / 81 (2012) | 82 / 85 (2012) | ------------------------------------------------------------------------ -------------------------------------- Fri, 4/17 | Sat, 4/18 | -------------------------------------- CRW | 87 / 89 (1976) | 89 / 90 (2019) | HTS | 88 / 87 (1976) | 89 / 89 (1955) | CKB | 83 / 88 (1969) | 86 / 88 (1976) | PKB | 86 / 89 (1976) | 87 / 91 (1976) | BKW | 80 / 84 (1976) | 84 / 86 (1976) | EKN | 81 / 87 (1976) | 85 / 88 (1976) | --------------------------------------

RLX WATCHES/WARNINGS/ADVISORIES

WV...None. OH...None. KY...None. VA...None.