RAH is still almost refusing to acknowledge the possibility of significant snow
Wintry precipitation is still likely this weekend and confidence in said occurrence is high, however the exact timing, amounts and p-types are still uncertain due to continued model differences and
thus low confidence. Best chances for wintry precipitation are still
along and north of the US-1 corridor.
Overview: A pair of upper level lows/troughs will develop on Saturday, one off the Southern Rockies/Desert Southwest and the other over the Northern High Plains/SW Canada. The former will shift eastward then east-northeastward through the ARKLATEX and into the TN Valley while the latter will dive south-southeastward, deepening
over the Plains/Midwest. The southern stream low will become absorbed into the stronger northern stream low over the MS/TN Valley Monday/Monday night as it continues its southward dive toward the
Gulf. Expect strong moisture advection into the Gulf Coast states and Southeast US ahead of the system Saturday and Sunday. Cold, high pressure will dominate at the surface over the Great Lakes region, ridging into western/central NC through the period in a CAD setup.
Meanwhile, a surface low will develop along the Gulf Coast on Saturday in response to the upper level system. The surface low is
expected to move along the Gulf Coast, through the panhandle of FL and northeast along the Carolina coast, while the wedge remains in place over northwestern portions of the area. As a result, there will be a very strong pressure gradient from west to east across NC on Sunday/Sunday night. Even the slightest shift in track, timing, temperature, etc. will result in significant impacts to the
forecast.
Timing: The latest medium-range models suggest precipitation will likely move into central NC very slowly from the south-southwest late Saturday or Saturday night. The ECMWF continues to be a tad
slower than the GFS, though the timing has come into significantly better agreement from 24 hours ago.
P-type: As mentioned above, a lot of uncertainty still remains with respect to wintry precipitation, as any small change/difference in timing, temperature, thermal profile, etc. will impact the p-type. As past events would suggest, a purely snow event is not likely as there is usually a mix of wintry p-types. Expect precipitation to
start as rain across the far south and southwest, though chances are looking decent for a mix of rain/snow across the northwest half of
central NC when precipitation moves in overnight. A mix of p-types, especially over the northwest half of central NC, is likely overnight as temperatures fall, while the southeast could remain
rain for the duration. Expect several p-type changes throughout the
event, especially along and north of US-1, with snow, sleet and freezing rain all possibilities. Regardless of p-type, liquid equivalents could range from one to two inches. Will hold of on getting too cute with any snow amounts at this time given the degree of uncertainty and how the varying p-types would impact accumulations.
Temperatures: Highs on Sunday expected to top out in the low to mid 40s while Sunday will be much colder in the NW, with highs topping out around freezing while the SE should reach into mid 40s again.
Lows both Saturday and Sunday nights will be similar, upper 20s to
mid 30s Saturday night and low 30s to around 40 degrees Sundayb night. Monday highs in the upper 30s to mid 40s expected at this time. -KC
Monday night through Wednesday: Medium range model guidance in
general agreement depicting a deep upper level low traversing the SE U.S., initiating yet another deepening sfc wave just offshore of SC/southern NC. The string dynamics associated with the upper level low and the potential for the sfc wave to sling moisture back into central NC. The models have trended a little farther south with the system and attendant precipitation. Thus, expect a chance of rain or rain/snow mixed primarily focused across the southern counties Monday night. If the system drifts just a little farther north, could see a threat for snow across the northern counties with some light accumulation possible. Min temperatures generally in the 20s to the lower 30s.
The upper level system and associated coastal low will sweep quickly eastward and offshore Tuesday with improving weather conditions into mid week. If there is any residual snow/ice pack across the Piedmont, could see temperatures Tuesday night drop into the teens. Away from the snow/ice pack, expect overnight lows in the 20s. Afternoon highs will remain well below normal with high temperatures in the 40s expected, closer to 50 across the far south southeast by
mid week. -WSS
