Forecast Summary for Sunday Afternoon (3-2-14) through Tuesday (3-4-14) (Brent/Raleigh)

Winter Weather Advisory for the Triangle in effect from noon to midnight Monday.

UPDATE 6:30 PM for Monday 3-3: This is a difficult time of year for which to forecast any kind of winter weather, especially at this latitude. 

Precipitation appears likely at this time due to several different lift mechanisms moving in to allow for cloud development. The front is still forecast to be right around the NC/VA border at daybreak. Changeover from rain to freezing rain then to sleet still expected to occur around midday into early afternoon for the Triangle N to S. The northern counties of the Piedmont and Coastal Plain will see the longest duration of freezing rain and sleet. These areas will also see the greatest accumulations of sleet, freezing rain and snow. Sleet/snow combined accumulations in the northern counties could reach an inch with lesser amounts south.

Complicating factors: 

1) With a very springlike day reaching into the lower 70s Sunday and given that we had mostly full sun, the soil surface has warmed considerably. If sleet/snow falls with less intensity than expected, then precipitation will melt rapidly. 

2) If cold air moving in (advection) is not as strong as anticipated, then rain/sleet mix will have a longer duration thus cutting down on accumulation totals.

3) The middle layers of the atmosphere dry out around 3-4pm lessening precipitation intensity. Also, if cold air is not as intense as expected, then the Triangle may see an extended period of freezing rain/drizzle rather than sleet. 

It will be important to monitor road and traffic conditions before travelling.
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This forecast is subject to change this evening. I will update it accordingly.

Difficult forecast for this late winter storm affecting Central NC. 

Sunday afternoon into Sunday night: With a surface ridge moving offshore and an arctic cold front approaching from the NNW, Central NC will get squeezed between these two systems, causing SW winds to increase throughout the afternoon. Expect highs well into the 60s with breezy conditions. Tonight: winds will die down some as clouds lower and thicken. Very mild overnight with lows around 50. The arctic front should be around the NC/VA border by 5am Monday. 

Monday: Throughout the morning, very cold air and precipitation will move south (also known as a backdoor coldfront) over the NC/VA border, arriving in the triangle late morning into the afternoon. Precipitation may begin as rain and as the front surges southward will likely change over to freezing rain then progress into several hours of sleet for the area. As warm air aloft cools to near freezing, sleet may mix with or even briefly change over to snow. This will be of short duration as midlevel drying is forecast to move in, thus cutting off moisture supply in the area where snowflakes form.

Monday night: travel conditions will be hazardous. The northeast piedmont and coastal plain may experience lingering precipitation mostly in the form of freezing rain and freezing drizzle. Given the exceptionally cold air in the lower levels of the atmosphere, some snow columns/needles/grains may form, especially east of the triangle. Thus, lingering p-type may be freezing drizzle and snow. Lows will be in the teens.

Tuesday and Tuesday night: Sunny with highs in the low 40s. Lows in the 20s.