Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 210050 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 850 PM EDT Thu Jul 20 2017 .SYNOPSIS... Convective activity on the increase into the weekend strong diurnal heat under northwest flow Friday. Frontal system passes early next week. && .NEAR TERM /THROUGH FRIDAY/...
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As of 800 PM Thursday... Sent an update to cut PoPs across the southern two thirds of the area. Radar images show weakening convection just north of the area as we loose sun heat. Guidance suggests that a cold front will stall just north of the area tonight. This could keep the northern sections under a threat of a shower or two or perhaps a storm overnight. As of 230 PM Thursday... Quite a few changes to the near term forecast. First and foremost is an MCS that formed last night, which continues to thrive/move east towards the CWA where daytime heating/unstable conditions have persisted, despite debris clouds across the area from earlier. Went ahead and based on timing of day and continued cooling of cloud tops evident on satellite, and added in a chance of pops across southeast Ohio and northeast KY zones. In addition, there have been small pop up showers this morning/early afternoon across the CWA, and think with the moist unstable conditions, that isold convection cannot be completely ruled out this afternoon, so went ahead and added at least a slight chance everywhere this afternoon. Focus then shifts to later this evening and tonight as a shortwave moves east across the Great Lakes region, driving a frontal boundary south into/towards Ohio zones, and possibly sinking southeastward overnight across the remainder of the CWA, as the flow aloft becomes more northwesterly. Models are all over the place with this, and there is a lot of uncertainty in this, particularly considering the time of day. Went ahead and decided to hang onto a slight chance to chance pops in the overnight hours. There is also a slight possibility that some storms in southeast Ohio could be on the strong side, with 25-40 kts 0-6km bulk shear across the area. SPC has included a slight or marginal risk across most southeast Ohio and adjacent WV zones. On Friday, convection will be on the increase area wide, particularly if there are any leftover outflow boundaries from previous night convection. Moisture will also be on the increase across the area, with dew points climbing a few degrees on Friday. This will push heat indices into the lower 100s across parts of the lowlands, and create the need for a heat advisory. The one concern is whether or not convection and cloud cover will dampen temperatures a bit. But feel public safety is more of a concern at this point, and even if the numbers are not quite advisory criteria, it will still be dangerously hot. In addition, heavy downpours, and strong gusty winds will be possible with any convection on Friday.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... As of 305 AM Thursday... Frontal boundary sags and stalls over northern portion of the area Friday night along with plenty of moisture in place. Showers and thunderstorms a good bet with boundary draped across the north especially on Saturday with daytime heating. Went likely pops along front chance pops elsewhere. Warm and muggy through Saturday night. && .LONG TERM /SUNDAY THROUGH THURSDAY/... As of 305 AM Thursday... Low pressure from the plains will finally move eastward across the great lakes Sunday and Monday. Expect trailing cold front to pass through the region Monday night, Tuesday time frame. This will keep the threat of showers and thunderstorms in the forecast. Cooler and drier high pressure builds in behind the front Tuesday night into Wednesday. This will bring some relief in the high temperatures and humidity as temperatures should average about 10 degrees cooler through Thursday. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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As of 730 PM Thursday... Diurnal heating and an frontal boundary north of the area are producing scattered showers and isolated thunderstorms across extreme northern WV and southern PA this afternoon. Some of this convection is developing further south affecting PKB and CKB with short periods of MVFR/IFR. Otherwise, VFR conditions expected through the period. Models suggest some cloud cover overnight. This clouds could prevent fog formation even along the river valleys. Patchy river valley fog is expected but not widespread to affect the terminals for an extended period of time. On Friday, unstable conditions expected with portions of the area under a marginal risk for severe weather. Brief periods of IFR/LIFR possible along heavier showers or storms. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z SATURDAY... FORECAST CONFIDENCE: High. ALTERNATE SCENARIOS: Fog development tonight in question, and will depend largely on amount of cloud cover overnight. 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. DATE FRI 07/21/17 UTC 1HRLY 00 01 02 03 04 05 06 07 08 09 10 11 EDT 1HRLY 20 21 22 23 00 01 02 03 04 05 06 07 CRW CONSISTENCY H H H H H H H H M M M L HTS CONSISTENCY H H H H H H H H M M M L BKW CONSISTENCY H H H H H H H H H H H L EKN CONSISTENCY H H H H L L L M M M M L PKB CONSISTENCY H H H H H H L L M M M L CKB CONSISTENCY H H H H H H L L L H H M AFTER 00Z SATURDAY... IFR possible Friday and Saturday in showers and thunderstorms.
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&& .RLX WATCHES/WARNINGS/ADVISORIES... WV...Heat Advisory from noon to 7 PM EDT Friday for WVZ005>008- 013>015-024>026. OH...Heat Advisory from noon to 7 PM EDT Friday for OHZ083-086-087. KY...Heat Advisory from noon to 7 PM EDT Friday for KYZ101>103-105. VA...None. && $$ SYNOPSIS...JS/SL NEAR TERM...ARJ/SL SHORT TERM...JS LONG TERM...JS AVIATION...ARJ

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