Browse Tag

17

Winter Storm Threat: February 17-18 (Only/Final Call)

A nail-biter between warming low-to-mid level air and marginal temperatures/wet bulbs at the surface. At least the Sun won’t be fighting most people during most of this event from D.C. northeastward.

Biggest uncertainty lies with snowfall rates, especially in areas that have marginal wet bulb temperatures at or above freezing (i.e. anywhere south of the Frederick, MD to Philadelphia line, generally speaking). That wet bulb freezing line has also been creeping further north than what I had anticipated when looking at the setup over the past few days. We’ll see it the wet bulb temperature or the snow/sleet rates win.

Winter Storm Threat: February 16-17 (Final Call)

Cut back on totals in central and eastern Pennsylvania a little bit, and tweaked 8-12″ contour ever so slightly. On the south end of things, I lowered the snow+sleet totals in North Carolina east of the Appalachians and into far southeastern Virginia. Still a solid 5-10″ event around the greater D.C. region.

20150216-17_MAsnow_final

Would have been interesting if people didn’t have Monday off… onset around D.C. is during the afternoon rush hour. At least we get to avoid that fiasco this time around. Should end near or slightly before daybreak for most. Enjoy your fresh pow pow.

Winter Storm Threat: February 16-17 (Initial Call)

Holy crap, a decent storm around D.C. where the rain/snow/mix line won’t be a concern! It’s a miracle.

So the biggest question at this point is QPF. There are some really juiced-up forecast models, and some not so much. Either way, snow ratios start getting good around D.C. and points north… talking 15:1 or better (20:1 along/north of the Mason-Dixon?).

20150216-17_MAsnow_initial

Other questions include how far north the 1+” totals get, and how much snow/sleet occurs in North Carolina and southeastern Virginia before they change over to rain/freezing rain (yes, sleet is included in the snow totals in that region).

The 8-12″ band is a little ambitious, but I feel like the more aggressive play is the correct one at this point. I think a 50/50 blend between the wetter models and drier models results in something close to this, with ratios taken into consideration.

I’ll issue a quick final update tomorrow morning.

Winter Storm Threat: Mar 16-17 (Final Call)

Not much change from the last map… mostly some expansion of the 4-8″ contour over the mountains and cutting back totals a little bit on the parts of the fringes. I don’t trust how bullish the models are on the snow maps because it looks like temperatures may end up a bit warmer than the raw 2mt in the evening, taking the snow longer to start accumulating. Maybe the front-end stuff will be heavy enough to stick earlier, but I have my doubts.

20140316-17_MAsnowFinal

Still some wiggle room with this, but models are coming to a nice consensus regarding the track, which is pretty much where my snow map is now and was yesterday. There appears to be more upside potential than downside with this event in the 1-4″ areas and up in the mountains, especially if you trust the higher QPF model solutions.

Winter Storm Threat: Mar 16-17 (Initial Call)

With what is hopefully our last snow threat for the season in the greater D.C. area, there is still a fair amount of uncertainty with the ultimate track of the system in addition to how wet it is. Lower than normal confidence with this forecast, which favors the Euro more than the GFS.

20140316-17_MAsnowInitial

My forecast seems somewhat conservative compared to what some of the models are showing, so I imagine there is probably more upside potential than downside with this disturbance. This thing could still shift some 30-50 miles north or south, so don’t get too hung up with exactly where all the contour edges are at this point.

Winter Storm Threat: Jan 17 (Final Call)

A quick update before I head into work… shifted the forecast further south overall and tightened up the contouring in areas that have slightly higher confidence than the initial forecast.

This results in a virtual no-show north of DC aside from some flakes in the air to a dusting. Southern VA into northern NC will get rocked as the vort. max pushes through. There is a risk of this shifting even further south according to some of the hi-res models.

Winter Storm Threat: Jan 17 (Initial Call)

Here comes the first notable snow event for the southern Mid-Atlantic this winter! A powerful upper-level vort. max will push through the region tomorrow, bringing strong dynamics with it that will help create a period of moderate to heavy snowfall. The snow will start in the morning hours in the higher elevations and will work east through the afternoon and evening. The I-95 corridor will probably start off as rain in the morning. Some sleet could accompany the transition in the late morning and early afternoon, with the changeover to snow occurring around mid-afternoon on I-95 between DC and Richmond. This could lead to large traffic headaches during the afternoon rush hour.

Just in case some people might be thinking it, the current forecast is not favorable for thundersnow/thundersleet.