Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 212318 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 718 PM EDT Fri Jul 21 2017 .SYNOPSIS... Strong to severe thunderstorms possible this weekend. Frontal system passes early next week. Cooler high pressure crosses midweek. && .NEAR TERM /THROUGH SATURDAY/... As of 730 PM Friday... Previous forecast remains on track. No changes necessary. As of 2 PM Friday... Bulk of convection across far eastern zones and starting to exit east. Behind line of convection, area of stratiform rain and lower clouds. Associated cloud cover is trying to thin a bit on satellite to our east, and it`s possible an additional shower or storm could refire, but initial thought is atmosphere is probably fairly worked over, but left a slight chance to chance in for the remainder of the evening. Otherwise, another warm and humid night on tap. Thinking if there are many breaks in the clouds overnight we could see widespread fog development. As has been the case, models are struggling to depict the overall pattern, and this is the case for tomorrow. General consensus is for frontal boundary to lift back north on Saturday, with continued warm and humid conditions. Wave of low pressure moving east along the boundary, combined with general warm and unstable conditions, will lead to additional rounds of showers and thunderstorms, particularly across the north, where strong to severe thunderstorms will be possible, as 0-6km shear increases to 35-40 kts. SPC has northern zones in a slight risk for Saturday, with much of the southern zones in a marginal. In addition, heavy downpours are expected, with the possibility of localized flooding issues again, as pw values rise to 1.7 to 2+ inches. As far as a heat advisory on Saturday, am getting heat advisory conditions across parts of the lowlands on Saturday, however, still uncertain as to where/coverage of greatest precipitation will be. Have elected to have the midnight shift reevaluate the forecast and determine if one is necessary. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... As of 330 PM Friday... Models differ on timing of a low pressure system moving through the Great Lakes Saturday night through Sunday night. Leaned toward the NAM solution for this period as it seems to have a handle on current features. Upper level system tracks to our north Saturday night into Sunday. As it passes, trailing cold front will push southward across the CWA. With soupy airmass in place, Any showers or Thunderstorms with the front could produce heavy downpours with PWs near 2 inches over much of the area. Low pressure over the plains will finally lift and cross the Great lakes Sunday night Through Monday night. Left over frontal boundary over the region will lift north as a warm front and trailing cold front will push approach the area Sunday Night and exit Monday evening. SPC has us in a slight risk for severe wx Sunday with afternoon heating and lifting frontal boundary along with increasing instability throughout the day. Airmass stays rather soupy and water concerns are defiantly possibility Saturday night through Monday night. WPC has a slight risk of excessive rain for Saturday night and Marginal risk through Monday. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 330 PM Friday... Cooler and drier air associated with high pressure that builds across the region on Tuesday and lasts through Thursday. This will bring a welcome relief from the heat and humidity. Another system or complex may approaches from west Thursday night into Friday. This will bring showers and thunderstorms back into the forecast. && .AVIATION /23Z FRIDAY THROUGH WEDNESDAY/... As of 730 PM Friday... The atmosphere remains unstable tonight into Saturday. Isolated light showers or small thunderstorms could move across the area overnight. Abundant low level moisture and possible clear skies could result in dense river valley fog. Coded IFR/LIFR conditions with different starting times at most sites. For Saturday, more unstable conditions compared with this afternoon are expected with the stationary frontal boundary to our north. Therefore, expect scattered to numerous showers and thunderstorms to produce brief periods of IFR/LIFR due to heavy rain along their patch particularly after 16Z. Strong gusty winds, along with small hail will be possible with any storms. More storms on Sunday. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z SUNDAY... FORECAST CONFIDENCE: Medium. ALTERNATE SCENARIOS: Additional convection could develop this evening. Widespread fog may not form 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. UTC 1HRLY 22 23 00 01 02 03 04 05 06 07 08 09 EDT 1HRLY 18 19 20 21 22 23 00 01 02 03 04 05 CRW CONSISTENCY H H H H H H M M L L L L HTS CONSISTENCY H H H H H H H M L L L L BKW CONSISTENCY H H H H H H M M L L L L EKN CONSISTENCY M L L L H H M M M L M M PKB CONSISTENCY M M L L M M M M L L L L CKB CONSISTENCY H H L L L H M L L L L M AFTER 00Z SUNDAY... IFR possible Saturday night and Sunday in heavy showers and thunderstorms. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...JS/SL NEAR TERM...SL SHORT TERM...JS LONG TERM...JS AVIATION...ARJ is the U.S. government's official web portal to all federal, state and local government web resources and services.