Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 210548 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 1248 AM EST Wed Feb 21 2018 .SYNOPSIS... After another mild night, a cold front crosses the Middle Ohio Valley Wednesday. The front stalls or wavers through the end of the week, with significant rainfall possible into the weekend. && .NEAR TERM /THROUGH TONIGHT/...
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As of 1245 AM Wednesday... A mild morning expected today, with southerly flow ahead of an approaching cold front. The cold front will move through from west to east this afternoon and evening. The surface front eventually outruns its mid and upper level support, so have 80-90 POPs through the middle Ohio River Valley early to mid afternoon, and then gradually decrease POPs along the front as it moves eastward into and through the mountains late this afternoon. Did include isolated to scattered thunder, with the best chance across the Tri-state and Tug Valley. Also included a non-diurnal trend for temperatures as the front and showers move through this afternoon. The front weakens and eventually stalls out this evening before another wave approaches from the west and the boundary starts moving northward/reforming across southern forecast area. This wave will bring another round of precipitation, mainly along and NW of the front -- so have 90-100 POPs in the Ohio River Valley with generally chance POPs across the mountains. Expect a decent spread in temperatures tonight, with lows in the upper 30s across the NW, and lows near 60 across the SE.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
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As of 245 PM Monday... Being on the cool side of the front, Thursday will be cooler especially toward the North with high temperatures near 50 in SE Ohio and warmer conditions in the 60`s in southern WV and SW VA. The heaviest bout of rainfall will move through the Mid-Ohio valley and northern WV Thursday morning, coincident with an area of healthy synoptic lift in the right entrance region of a strong jet. PWAT nearing 1.4" and strong equivalent potential temperature convergence indicates this enhancement would generate moderate rainfall rates with this wave. Total precipitation through this period will near an inch at the highest in the Tristate area of WV/KY/OH waning to less than 0.5" in SE WV and SW VA. Friday, the front lifts back northward increasing afternoon temperatures back into the 70`s in the lowlands. Destabilization will occur with afternoon heating with SFC based CAPE reaching up around 500 J/kg, so have opted to include the possibility for thunder with any warm front/warm sector shower activity. In spite of strong winds aloft lending decent sheer, lack of instability and a water-logged profile aloft doesn`t leave much in the way of strong updraft development. So, there is low severe potential. rain showers continue through Friday night with the same frontal boundary draped across the northern tier of zones. Given uncertainty in the location of the axis of heaviest precipitation, have opted to leave flood threat in the HWO for now.
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&& .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 315 PM Monday... Multiple waves not unlike the prior (Thu AM) move across the the frontal boundary through the weekend - specifically, Saturday evening and Sunday morning, meaning this time frame will have to be refined and paid special attention to for possible flooding concerns. High moisture availability remains while strong eastern Canadian jets continue to generate large scale ascent and induce surface waves along the front. Highest precipitation amounts will again fall in the northwestern half of the CWA across SE Ohio and northern West Virginia near the frontal boundary. Quite aggressive models like the GFS peg as much 4+" of rain from Friday through Sunday, however the conservative blended approach yields an axis of 2-3" or so up through the Ohio Valley and northern WV. This seems realistic for widespread amounts across this heaviest axis but storm training will bear watching as we approach the event itself armed with higher resolution forecast information. By the weekend, soils will already be saturated, so hydrological systems will be quite prone to flooding. Although there is not the confidence in flooding on specific small-scale basins given location uncertainty, heavy rain in the Mid to Upper Ohio River basin as a whole could lead to another flood of the Ohio River. While not forecast at this time, probabilistic forecasts like those found at weather.gov/erh/mmefs indicate a strong possibility given recent model trends. A break in the pattern shows late Sunday as an upper-level trough rotates through the Great Lakes region, pushing the front past the mountains and out to the East Coast. High pressure quickly builds in behind to dry out the region. A small handful of models quickly brings another trough/front pair through Monday night/Tuesday, so have kept PoPs from the blend of models for this period to indicate this chance. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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As of 1245 AM Wednesday... VFR conditions are expected into today. A cold front, with showers along and behind it will bring MVFR to possibly IFR this afternoon into tonight. Also included some VCTS at across the south. MVFR to IFR is expected tonight in stratus and rain. Southerly winds this morning will become W to NW with the frontal passage, and more northerly overnight. Debated putting low level wind shear in TAFs, but with some flow remaining at the surface opted to keep it out for now. Will monitor this and may need to amened to add it eventually. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z THURSDAY... FORECAST CONFIDENCE: High. ALTERNATE SCENARIOS: Restrictions along and behind the front could vary. 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 WED 02/21/18 UTC 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14 EST 1HRLY 22 23 00 01 02 03 04 05 06 07 08 09 CRW CONSISTENCY H H H H H H H H H H H M HTS CONSISTENCY H H H H H H H H H H H M BKW CONSISTENCY H H H H H H H H H H H M EKN CONSISTENCY H H H H H H H H H H H M PKB CONSISTENCY H H H H H H H H H H H M CKB CONSISTENCY H H H H H H H H H H H M AFTER 06Z THURSDAY... IFR possible in showers late Wednesday night into Thursday.
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&& .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...MZ/MC NEAR TERM...MZ SHORT TERM...MC LONG TERM...MC AVIATION...MZ

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