Area Forecast Discussion
Issued by NWS Charleston, WV

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280 FXUS61 KRLX 211844 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 244 PM EDT Fri Apr 21 2017 .SYNOPSIS... Cold front sags south through this afternoon then lifts back north late Friday night/Saturday. System exits Sunday night/Monday. Dry early next week. && .NEAR TERM /THROUGH SATURDAY/...
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As of 240 PM Friday... Line of convection working across the southern coalfields. Storm environment showing weak shear and instability in a broad convergent zone ahead of main front. The front will help continue to kick line off to the south and east for the remainder of the afternoon and into in Saturday. We may see a slight uptick in intensity this afternoon in max daytime heating but severe is not expected at this time. Front never makes it too far south as vigorous sfc to mid level wave approaches. Models still showing a fair spread in where best dynamics and qpf set up, with the GFS trending to more southward solution, with lesser amounts of qpf on saturday. The NAM further to the north with both the initial and secondary waves. Hanging our near term forecast more in line with the GFS solution for the time being and will hold off on any headlines, which probably would be more appropriate just outside the period on Saturday, if needed. For temps, used a model blend.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
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As of 420 AM Friday... This will be a wet period, as low pressure tracks south of the area. It is progged to move from northern Arkansas Saturday morning eastward, across Tennessee Saturday, and then more slowly across the Carolinas Saturday night through Monday night, as it occludes and becomes stacked through the mid and upper levels by Monday morning. Models show 4 to more than six inches rainfall over the central Appalachians through Monday morning, which makes sense given an upper level low tracking slowly south of there. The GFS was the one showing in excessive of six inches, and the outlier there. Otherwise, the models are converging on a solution of three to three and a half inches for roughly the southern third of the forecast area, and at least two inches for the southeast half. The latter is dependent on the exact track of the system and the sharpness / consistency of the northern edge of the heavier rainfall, which comes in several waves. Highlighted the HWO for potentially excessive rainfall through this weekend, and have heavy rain in the grids where PoPs are categorical, roughly the southeast half Saturday and Saturday night. There is a gradual shift southeastward in the rainfall Sunday through Monday, as the system gradually pulls away from the area. Question is how long low level moisture lingers in the southeast half of the area on Monday, and whether low clouds / fog become an issue in the light and variable flow in the wake of the wet system Monday night. Temperatures close to central guidance, except went a little lower Sunday afternoon, which should not be much warmer than Saturday. This wet weekend will also feature highs much lower than recent days and, in fact, break a string of 13 consecutive days with highs in the 70s and 80s at Charleston.
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&& .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 420 AM Friday... Weak high pressure crosses Tuesday. A cold front approaches Wednesday, but then retreats northward, as a warm front Wednesday night, as its driving upper level trough lifts out, and upper level ridging builds. This opens the door to warmer weather, even a summer preview, toward the end of the work week. Central guidance temperatures accepted, climbing well above normal by Friday. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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As of 240 PM Friday... Seeing convection on a line from KCKB to just south of KHTS, in areas south and east this afternoon. Generally VFR in place to the northwest of the front. Cold front remains in general vicinity through TAF period as a atmospheric wave arrives from the west. Atmospheric column will see a moisture increase overnight into Saturday for a period of MVFR and IFR conditions late overnight and into Saturday. Painted general IFR conditions after 10Z for most sites and we probably will not see much daytime recovery on Saturday as stratus and showers remain in the vicinity. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z SATURDAY... FORECAST CONFIDENCE: Medium. ALTERNATE SCENARIOS: More widespread mvfr and ifr conditions may occur than currently forecast. 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 18 19 20 21 22 23 00 01 02 03 04 05 EDT 1HRLY 14 15 16 17 18 19 20 21 22 23 00 01 CRW CONSISTENCY M H H H H H H H H H H M HTS CONSISTENCY H H H H H H H H H H H L BKW CONSISTENCY M M H M H M H H H H H M EKN CONSISTENCY H M H H H H H H H H H L PKB CONSISTENCY H H H H H H H H H H H M CKB CONSISTENCY M H H H H H H H H H H L AFTER 18Z SATURDAY... IFR possible into Sunday with another wave of low pressure.
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&& .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...KMC/TRM/SL NEAR TERM...KMC/SL SHORT TERM...TRM LONG TERM...TRM AVIATION...KMC/SL

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