Browse Tag

February

Winter Storm Threat: February 8-10 (Only/Final Call)

This storm has a complicated setup. You have multiple surface lows within a broader upper-level trough, marginal surface temperatures, and large discrepancies in QPF placement between the models.

Temperatures along and east of I-95 are the most uncertain, which are expected to be in the low-to-mid 30s through most of the event. Areas north and west of I-95 will start above freezing, and will cool to at or below freezing depending on how strong the snowfall rates are tonight.

Snowfall rates will be one of the most important factors in determining which areas see 4-8 inches, and which areas get 1-4 inches. The best rates are likely to be along the Maryland/Pennsylvania border into southern New Jersey.

20160208-09_MAsnow_final

The intensity of the initial coastal low, the secondary coastal low development, the strength of the low over the Great Lakes, and the timing of the strengthening and weakening of these lows are wreaking havoc on the QPF output on the various models.

I tried my best to offer a realistic compromise between the differences in QPF, while also accounting for the surface temperature and snowfall rate issues. I could definitely see a tighter gradient between accumulation amounts than what I have on the map.

Winter Storm Threat: February 26-27 (Only/Final Call)

It’s time for the southern folks to finally cash in this season. Some spots in North Carolina and southeastern Virginia are expected to get as much snow as they typically get in a year, so this should be a fun storm for them. I battled a bit in the placement of the 1″ and 2″ contours on the north edge of things, as there is a wide range of solutions in that department still. The rain/snow line across North Carolina is another big hurdle, but it seems the warm nose will be around 850mb, which made sorting it out on the models easier.

20150226-27_MAsnow_final

I expect a couple of 12+” reports out of this in North Carolina and southeastern Virginia. The northern edge of the 1-2+” has equal risks of busting high/low.

Winter Storm Threat: February 21-22 (Only/Final Call)

Lots of uncertainty with this system. How much precip. falls as snow before the changeover, timing of the changeover, rates during the daytime hours, etc. The only thing that’s not really in question will be the surface temperatures at the start of the storm. Cold, cold, cold.

20150221-22_MAsnow_final

Models overall show a little more potential to get higher totals than lower totals east of the Appalachians.

My brain is done. k bye.

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 2014-2015 (DJF) Forecast

I like to keep my seasonal forecasting short and sweet, so here it is:

Reasoning:
– Latest model guidance and ENSO trends suggest DJF will likely be a weak El Nino.
– +PDO to support ridging in the western U.S. and troughing over the Midwest/eastern U.S.
– +AMO could help keep the Southeast milder (read: less cold).
– -QBO will allow for a greater chance for blocking in the Atlantic (-AO/-NAO) as well as stratospheric warming events. This would promote colder temperatures in the eastern half of the country.
– Drought conditions in the West will promote warmer and drier conditions there.

Risks:
– The western U.S. could go warmer given favorable +PDO and long term drought.
– If -NAO/-AO becomes the main forcing mechanism for the U.S. weather pattern, it could bring colder air into the Midwest, Mid-Atlantic and Southeast while providing warm and wet risks in New England.
– If a moderate Nino develops, a stronger subtropical jet associated with it could allow for wetter conditions across the southern U.S. and Mid-Atlantic.

A note on my track record… I have been about 50/50 with long-range forecast skill since I started in 2010. There are many others out there with more long-range knowledge, reasoning and a better understanding of how the atmosphere works on a longer timescale. That said, nearly every forecast I have seen so far favors a warmer West and cooler East, so I’m not exactly breaking the mold with this forecast. It looks like we’re all in the same boat with this one. The only thing left to see is if we can sail to victory or go down with the ship in defeat.

As always, the forecast anomalies are based off the latest 30-year normals (1981-2010).

Winter Storm Threat: Feb 14-15 (Final Call)

A trough will traverse the Ohio Valley today and will start to take on a negative tilt as it reaches the East Coast, with a nice vort max developing over the Carolinas that will allow for a rapid strengthening of the surface low once it moves off the coast. Cold air aloft and the upper-level dynamics will be fairly supportive of snow, but somewhat-limited moisture and a warm boundary layer (despite the snowpack) will prevent a bigger snowfall within the forecast region.

20140214-15_MAsnowFinal

Risks are more towards the lower side across the region with this system, though there is some upside potential near the coast if the low can strengthen faster. A little event to top off this snowy period before temperatures jump well above normal next week.