Experienced forecasters know that there is a transition interval where the forecast goes from the extended range — generally from 3 days out to 7 days — — into the short-range which is from 6 / 12 hours out to 48 or 60 hours. ( 2.5 days). This transition -when we move from the extended-range into the short range in the forecast process can cause significant jumps in the various weather models. We have seen that a number of times this winter especially in the Middle Atlantic region and that trend seems to be continuing with this new event coming up here for Wednesday night into Thursday, AND .Thursday night into Friday.
First it is clear that the European model has been consistently running way too wet and cold with too much snow all winter and has been especially true this winter in the middle Atlantic. Several days out it has shown these significant if not major snowstorms in Maryland Delaware West Virginia and Virginia — even into northern North Carolina — only to see these events fall apart . Beyond day 3 the European model is the best weather model in the world but once we get within 48 hours of the event it is just an ordinary model and it has problems like every other model out there.
The vast majority of the data overnight into early this morning clearly shows a weakening event. and as a result this FIRST CALL snow map is vastly different from what I issued at FIRST GUESS. But that is why we called the FIRST GUESS. Sometimes the transition from the extended-range into the short-range is not this jarring but clearly that is not the case this season. There have been a number of events which looked really good at day 3.. Day 4 Day 5 and Day 6 but once we get within 48 hours or 36 hours before the event things have changed dramatically.
This appears to be the case with this event .
WHAT HAS CHANGED ?
First is that the cold air is not coming as far south as the earlier models were showing.
The only model that continues to show the cold air — that is to say an air mass cold enough to support a rapid change over to snow — reaching as far south as RTE 460 in southern VA is the European model. The model continues to show more snow than any other model out there, more overall actual precipitation and colder temperatures. Which results in a lot more snow for all of VA WVA MD and DEL .
The early morning GFS and NAM models along with a lot of other data which I will not bore you with are vastly different.
The first burst of snow comes in from Ohio into West Virginia western Maryland and Northwest Virginia by this evening. There are periods of light to moderate snow in northern Virginia… most of western and central Maryland into south central Pennsylvania overnight which changes to sleet in the northern Shenandoah Valley
Then during Thursday morning there is a break in the action where nothing really is happening in Maryland Delaware West Virginia or Virginia. This is a HUGE CHAMHE
Thursday afternoon rain develops in eastern Tennessee , western North Carolina and southwest Virginia. The rain spreads into most of Virginia and eastern portions of West Virginia by Thursday afternoon then into central and Northern Virginia transitioning over to sleet and snow in the evening hours North of Highway 460 in Southern Virginia.
ANOTHER MAJOR CHANGE is this 2nd round of precipitation is significantly lighter when compared to what the previous models were showing on Monday and Tuesday. In those earlier model runs the moderate snow continued across most of central and northern Virginia Maryland and Delaware open till 8 to 10 am Friday morning.
The new data shows the precipitation ending much sooner than that especially in central Virginia and the central portions of the Shenandoah Valley. Light snow continues in northern Virginia DC Baltimore and central Maryland until Friday around 10 am. . And after that the whole thing is done.
The data does continue to show a significant sleet storm and or freezing rain developing in most of Virginia Maryland and Delaware on Saturday morning and continuing off and on throughout the day. The data does show significant amounts of freezing rain and ice across the southern half of Virginia away from Hampton Roads and as far west as Roanoke and down to the North Carolina border . But that is assuming that this event on Saturday does not fall apart like everything else has this winter in the lower Middle Atlantic region
wed night thursday am, 1st part
then thursday am to midday NOTHING is happening… this is very different from earlier models
MUCH SHORTER DURATION OF SNOW IN CENTRAL VA THURSDAY NIGHT INTO FRIDAY AM WHICH ENDS BY 1AM INSTEAD OF 7AM,
