Thursday, March 12, 2009


SYNOPSIS: THU MAR 12 - 1:45 PM. The Sterling, VA latest Hazardous Weather Outlook (HWO) for portions of southern Maryland - central and southwestern Virginia suggest the weather is conjuring up some mischief to round out the week. At mid-morning today then again at 1134 AM the NWS made some adjustments to the outlook and area forecasts. Though they are holding off with accepting a northward trend in precip overnight, the reality may be different. Even if current forecasts hold, the likelihood increases that schools in southern Maryland may face surprise delays Friday morning. Even your local forecasts on the Weather Channel are beginning to insert "snow showers" for tomorrow from Baltimore on south. It may indeed be time to invoke the seldom-used LOW model: LOOK OUT WINDOW.

(1) Moisture from the stalling frontal boundary is over-running a 1040 mb High pressure at all critically analyzed levels of the atmosphere: 500mb, 700mb and 850mb. Embedded in the southwest to northeast flow are several shortwaves to cross the Mid-Atlantic overnight.

(2) Rules of climatology are not ruling the day as temps will remain nearly 10 degrees below normal. While the atmosphere over the metro areas remains dry from surface to 12,000 feet even the NWS admits rapid influx of moisture aloft in this cold regime will saturate the air. Relying on guidance and climate norms, without taking into account the trend in plain sight will make for a lot of surprised people Friday morning.

3) Latest NWS update states 1-2" of accumulating snow (or sleet/freezing rain) overnight in the following MD/VA counties: Charles, St. Mary's, Montgomery, Prince Georges, Loudon and even DC means there is a surprise risk of those schools being delayed on Friday. While the ground may be warm, remember this snow will fall at the point when temps are lowest overnight.

WHAT'S REALLY AT THE END OF THIS RAINBOW? If the current trend is any indication, forecasts regarding this snow/ice event across the Tennessee Valley are not going as planned. Just atake a look at the Water Vapor loop and be stunned at the moisture influx. I think we have a serious problem developing for the Mid-Atlantic that sneaking up on everyone right before their eyes. DID YOU CLICK ON THAT FIRST LINK OR JUST PASS OVER IT?

Uh, huh. Caught you there. Now, stop skimming. Go back and look at the RADAR. You see what I see? Tell me none of this makes it into the Mid-Atlantic, or that 12 hours of warm air advection into a cold dome is not enough to overcome low dewpoints. Now, take a look at the US Hazards projection made YESTERDAY (3-11-09) for the period starting TODAY. Umm, Hello Dolly? There's more going on than just "heavy rain." For all the hoopla about" lack of shortwaves" in the southern stream to prevent development of winter precipitation, reality must sure be biting about now. (Frequent readers and storm watchers know who I'm talking about and where this was said.) Winter Storm Warnings and Winter Weather Advisories cover eastern Arkansas and western Tennessee right now. As if that was planned. Just as peculiar is the northeastward creeping of that "pink stuff" on our Mid-Atlantic radar. Obviously most of that is "virga" which is precip falling but evaporating before ground level, but throw in 12 hours of that and you'll have frozen precip reaching the surface by daybreak.
10:15 AM: The game's a-foot (no pun intended). A heads up to all central and southern Maryland teachers, administrators, and especially MSA coordinators: Your best laid plans for tomorrow might be spooked as if it were Friday the 13th. (Oh, wait.. tomorrow is Friday the 13th.) Consider yourself duly advised.

No comments: