Area Forecast Discussion
Issued by NWS Charleston, WV

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774 FXUS61 KRLX 280009 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 809 PM EDT FRI MAY 27 2016 .SYNOPSIS... Slow moving convection with heavy downpours again on Saturday. Moist southeast flow will raise shower chance Sunday in the mountains. Upper level ridge rebuilds next week. && .NEAR TERM /THROUGH SATURDAY/... Increased pops per thunderstorm development as needed otherwise previous discussion follows. significant changes were necessary to the previous forecast. Upper ridge along the east coast will build westward today...with increasing heat and humidity. Isold showers and thunderstorms...already starting to develop across the mountains in the afternoon heat...will for the most part dissipate after sunset...although a few may continue to linger through the evening across the east as an upper disturbance rounds the edge of the ridge. With a very light steering flow...generally less than 5kts...thunderstorms will be slow moving...and capable of producing heavy downpours...with the moisture laden atmosphere in place. Otherwise...another warm muggy night on tap...with patchy fog developing. Saturday looks to be a carbon copy of today...perhaps a degree or two warmer with ridge continuing to build westward. Afternoon convection will fire again off the mountains...and possibly drift westward in the southeasterly flow. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... Area sits in deep layer south to southeast flow Saturday night and Sunday, between an upper level ridge along the eastern seaboard, and an upper level shortwave trough lifting through the midwest. A broad shortwave trough over the southeastern states serves almost as an extension to the midwest one, but surface low pressure associated with it comes ashore into the Carolinas and then meanders northward. It appears that the moisture associated with the system coming from the southeastern states will be drawn northward in a corridor up the appalachians, but no farther west. As such...have pops going to likely in the northern mountains of WV Sunday afternoon. The moist corridor shifts east of the area late Sunday and Sunday night, as the midwest shortwave turns eastward and moves across the Great Lakes Sunday night, and then the northeastern states on Monday. This brings us back into the diurnal thunderstorm mode for Monday, and, as drier low level air arrives from the west in the wake of the upper level shortwave trough, the late day thunderstorm chance on Monday should be limited mainly to the mountains, which will then quickly die down with the sunset. Guidance continues to trend downward for highs on Sunday given the moist corridor giving rise to plenty of clouds. Otherwise temperatures were reasonable in light of the latest guidance, with little if any change needed. && .LONG TERM /TUESDAY THROUGH FRIDAY/... Upper level ridging rebuilds over the central Appalachians and middle Atlantic seaboard in the wake of the exiting shortwave trough. This leads to a dog day summer pattern for the middle portion of the short work week, with diurnally driven thunderstorms tending to favor the mountains per elevated heat source. Models begin to diverge on the strength and timing of the ridge, which is stronger and peaks later, on Thursday, in the GFS solution, while weaker and peaking on Wednesday in the ECMWF solution. This model divergence continues on Friday, as the ECMWF rolls an upper level low across southern Canada during the week, which then pushes a cold front through the area on Friday. The GFS has divorced itself from this solution, instead shearing out the southern Canadian low, and dropping another southeastward through the plains states toward the lower Mississippi valley. The forecast does not bite on the left turn taken by the GFS, and instead picks up on an increasing chance for showers and thunderstorms Thursday into Friday, before turning slightly drier and cooler late Friday and Friday night. Temperatures close to central guidance with little change through day 6, and then the trend toward slightly lower values. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... Isold convection through about 03Z...with brief heavy downpours...and brief mvfr/ifr conditions in vicinity of storms. After 03Z...MVFR valley fog developing late...generally after 06Z...particularly in areas that received rainfall during the day. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z SUNDAY... FORECAST CONFIDENCE: Medium to high. ALTERNATE SCENARIOS: Fog may or may impact terminals, but went with it for most sites given general clearing sky trend. 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 SAT 05/28/16 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 H M M M 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 M M M 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 00Z SUNDAY... No widespread IFR conditions expected. && .HYDROLOGY... The river gauge...and forecast the South Side Bridge in downtown Charleston has not be reading correctly. The NWS hydrologist is working to correct this problem. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...TRM/JW NEAR TERM...JW SHORT TERM...TRM LONG TERM...TRM AVIATION...JW HYDROLOGY... is the U.S. government's official web portal to all federal, state and local government web resources and services.