Area Forecast Discussion
Issued by NWS Columbia, SC

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000 FXUS62 KCAE 261751 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 151 PM EDT Mon Jun 26 2017 .SYNOPSIS...
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A front will linger near the coast through Tuesday. Deeper moisture ahead of the front will remain east of the forecast area. Surface high pressure will extend through the region Wednesday with the front farther off the coast. Diminished relative humidity will be associated with this pattern. The ridge will be in the Atlantic late in the week and circulate increased moisture into the forecast area, leading to increasing chances of storms over the weekend.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Unseasonably cool and dry air continues to filter into the Southeast U.S. as Canadian surface high pressure moves toward the region. Lows are forecast to be in the upper to mid 60s and dew points in the upper 40s to mid 50s.
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&& .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
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Main concern during this time frame is the passing of an upper trough axis during Tuesday afternoon and evening. Deeper moisture remains well offshore with the old frontal boundary and the lack of moisture is the limiting factor for precipitation and limiting instability. The positively tilted trough axis should cross the forecast area around 00z with best PVA crossing the region during the afternoon hours and 500mb temperatures around -12C. Forecast soundings indicate a generally dry atmospheric column and an inverted-V signature with a shallow saturated layer between 700mb and 850mb depending on the model. Precipitable water values rise to just below 1.5 inches before the trough axis passes which may be sufficient enough with weak instability to support isolated/scattered showers mainly across the northern and eastern half of the forecast area during the 18z-00z time frame. Max temperatures will be slightly below normal ranging from the lower 80s northern Midlands to upper 80s southeastern Midlands and CSRA. Much drier air will move into the region behind the trough Tuesday night as high pressure builds in from the north and dewpoints fall into the 50s and precipitable water values drop below an inch. This will provide well below normal overnight lows, nearly 10 degrees below normal, in the upper 50s to lower 60s.
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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Spectacular weather expected across the forecast area for late June with a seasonably cool surface ridge in place Wednesday morning providing below normal temperatures and low humidity. Atmospheric moisture will remain low Wednesday with precipitable water values less than an inch providing mostly clear skies and little chance of precipitation. The upper level pattern transitions from nearly zonal 500mb flow early in the period to more southwesterly flow for the remainder of the extended forecast period with broad upper troughing across the northern portion of the country. The surface ridge will shift offshore Thursday and further away on Friday allowing a moist southerly flow to return over the forecast area with increasing dewpoints and humidity and precipitable water values pushing back to near 2 inches by Friday, tapping into the Gulf of Mexico. Generally expect an increase in diurnal convection Friday through the weekend with increasing moisture and possible weak shortwave energy enhancing convection Sat/Sun when highest PoPs are expected. An upper ridge tries to build into the southeastern states on Monday with the deepest atmospheric moisture shifting east of the forecast area which may lead to lower chances of convection but still will keep some rain in the forecast. Temperatures through the period will generally be near normal for highs in the upper 80s to lower 90s with slightly below normal low temperatures early in the period then becoming near normal.
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&& .AVIATION /18Z MONDAY THROUGH SATURDAY/...
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VFR conditions are expected at all TAF sites. EXTENDED AVIATION OUTLOOK...No significant impacts to aviation expected.
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&& .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$

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