Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
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069 FXUS62 KCAE 270744 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 344 AM EDT Mon May 27 2024 .SYNOPSIS... A cold front will move through the area tonight. Scattered strong thunderstorms are expected ahead of the front today with temperatures remaining above normal. More seasonable temperatures and drier conditions are expected behind the front through mid to late week as a high pressure area builds in from the upper Mississippi Valley. && .NEAR TERM /THROUGH TONIGHT/... The focus for today remains centered around the MCS moving through the TN Valley at this time and its potential impact on the environment later this morning into early afternoon before another round of convection is expected as a cold front approaches from the west. The ongoing MCS is forecast to cross the mtns during the predawn hours and gradually decay as it moves into the Midlands, but it should be noted that the hi-res guidance has struggled with the timing of this feature with even the updating HRRR still lagging behind the actual speed of it. This means the MCS could move into our area earlier and dissipate earlier which may allow for the atmosphere to recover more and destabilize. Hi-res CAM guidance shows generally scattered convection developing with locations being a bit different but a focus in the CSRA early afternoon. Convection is likely to initiate on whatever outflow boundary is left behind from the decaying morning convection and possible differential heating boundary created by debris clouds, so even 12 hours out there is limited confidence in where and when convection will initiate. However, the environment should be rich in moisture with ensemble PWATs around 130-150 percent of normal with values around 1.6-1.8 inches this afternoon ahead of the approaching front. This may support an isolated flood threat if there is training of storms. Forecast soundings indicate a bit of a capping inversion albeit weak, and increasing upper support in the form of shortwave energy should help convection develop during the afternoon in an increasingly unstable environment, assuming the morning MCS does not disrupt this process. Hi-res guidance suggests MLCAPE values over 1000 J/kg with 25-30 knots of deep layer shear supporting scattered convection that may try to organize a bit. SPC continues to outlook the forecast area in a slight risk for day with damaging wind gusts as the primary threat. Convection should shift eastward and dissipate over our area by 03z as 850mb winds shift more west to northwesterly as the trough axis shifts over the region with the cold front pushing through the region late tonight. Temperatures today are challenging and dependent on how much cloud cover exists through the day but will continue to advertise another warm day with highs ranging from the mid 80s western Midlands and upper CSRA to the lower 90s in the eastern Midlands. Overnight lows expected to range from the mid 60s west to around 70 east as the cooler and drier air behind the front reaches the western Midlands during the predawn hours. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... A drier atmosphere moves in behind the departing front for Tuesday and Tuesday night with slight height rises and zonal flow aloft. The upper level trough to our north will remain quasistationary, however a lack of forcing and PW values falling below 1" by midday should keep things dry. Highs Tuesday afternoon will still be in the upper 80s to low 90s with little in the way of cloud cover. Overnight lows will be more seasonable in the low to mid 60s. Little change in our sensible weather for Wednesday, except for some additional drying with PW values closer to 0.6"-0.7". Highs a few degrees cooler than Tuesday in the mid to upper 80s with nighttime lows in the low 60s. && .LONG TERM /THURSDAY THROUGH SUNDAY/... Broad upper trough generally remains to our north mid to late week as multiple disturbances rotate through the flow. The first discrepancy comes Thursday with the GFS bringing a shortwave through the southern stream and bringing a few showers to the CSRA while the EC remains dry. Friday, a weak but generally dry front will push through the area from the north. Behind that, high pressure will build in from the west as upper ridging replaces the trough that will finally move offshore for the weekend. Boundary layer flow becomes a bit more onshore by Sunday with some indication that moisture flux will be increasing. However, the GEFS mean keeps PW values around 0.75" through Sunday, with some increase toward about 1" Sunday night. Given some uncertainties late in the forecast period, kept close to NBM guidance which keeps us dry through Saturday before bringing in a slight chance of showers/storms on Sunday. Dewpoints remain in the 50s in the extended period while temperatures will be in the low to mid 80s Thursday and Friday, which is near to or slightly below normal for late May. A few more degrees of warming follow for the weekend with high pressure ridging down the eastern seaboard. Overnight temperatures also get a reprieve with lows in the upper 50s and low 60s during this time. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... VFR conditions generally expected through the 24 hr forecast period with the exception of restrictions in scattered convection. Satellite showing mostly clear skies across the region early this morning but a convective complex is moving into the TN Valley and will approach our area after sunrise bringing increasing clouds and possible showers or thunderstorms if it holds together over the mountains with limited confidence. 25-30 knot low level jet is keeping surface winds up around 5 to 7 knots out of the south through daybreak then winds increase to around 10 knots and become gusty late morning through the afternoon as a cold front approaches by this evening. It is unclear whether or not the convection arriving after sunrise will hold together but there is high confidence in increasing clouds mid morning with this feature and possibly some MVFR cigs at AGS/DNL so included a tempo group to cover that from 11z-15z. Another round of convection is expected this afternoon ahead of the approaching cold front but there is uncertainty given how the morning decaying convection impacts the environment to support afternoon convection, which appears to be scattered at this time, therefore carried VCSH for now until confidence increases for impacts at the terminals. Winds should diminish with sunset to around 5 knots from the southwest. The boundary layer remains well mixed overnight so fog is not expected. EXTENDED AVIATION OUTLOOK...Restrictions possible Monday evening in scattered thunderstorms as a cold front moves through the area. Otherwise, significant restrictions not expected. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...None. GA...None. && $$