.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/...
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Shortwave energy and overrunning will continue tonight as the upper-level low continues to shear apart and track east. The surface low will track through the Gulf Coast States before transferring its energy to a coastal low off the North and South Carolina Coast by morning. The mid-level forcing will be stronger, which is evident in most guidance, so a steadier snow is expected across the entire area. There may be just enough warm air to mix in aloft for snow to mix with sleet and freezing rain overnight across portions of central Virginia. Also, rain/sleet may also mix in across extreme southern Maryland (southern St Marys County). Otherwise, snow is expected across other locations. Coastal low pressure will move offshore Sunday, but the sheared upper-level system will pass through our area late Sunday into Sunday night. A steady snow associated with the coastal low will continue into Sunday morning before gradually tapering off to light snow and flurries during the afternoon. However, another period of steadier snow is possible late Sunday into Sunday night as the upper-level low passes through the area. The best chance for snow appears to be near and to the south/west of the Potomac River. Additional accumulations should be light, but it may be enough to cause additional problems on untreated surfaces. As for headlines, did upgrade the advisory to a warning for the northern Shenandoah Valley and the Washington Metropolitan area. Am concerned that east-west oriented banding may cause locally higher amounts across these areas. Frontogenetical forcing increases as the low passes by to the south late tonight into Sunday morning, and looking at the 00z nam bufkit, did notice the Eqivalent Potential Temperatures nearly neutral with height for a period between 06 and 12z along with slightly negative EPV and Frontogenetical forcing that lines up, suggesting that CSI banding is possible. For the mid-morning update, did not yet make any headline changes or forecast changes. That having been said, guidance continues to trend heavier, so it is quite possible an additional upgrade of headlines and forecast totals could be in the offing. Latest NAM and SREF are QUITE snowy (notably snowier than our forecast), but would like to see a bit more support to them before making adjustments. Still also want to point out that there is still uncertainty regarding the placement and location of any banding precipitation and also with the track of the low. Any slight change in either direction will have an impact on snowfall totals. Having that been said, there will be impact from snow across the entire CWA tonight into Sunday. High pressure will return later Sunday night through Monday, bringing dry and seasonably chilly conditions.
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