Squall today, cold tomorrow.
1:45 PM 2/18 - UPDATED TIMING OF SNOW SQUALL ARRIVAL IN THE MID-ATLANTIC
Arctic front traverses eastern Mid-Atlantic between 4 PM and 7 PM, bringing another round of rapid snowfall near the PM commute, accumulating 1-2" in some areas by 7 PM.
Liquid map for Wed 2/18 shows precip amounts will be light, but ratios will allow for fluffier snow. Similar to Saturday 2/14, roads may become quickly snow-covered and visibility could reduce to one-quarter mile in brief heavy snow squalls during the PM commute.
5:30 AM 2/18 BASIC SUMMARY FOR BUSY PEOPLE*
- WED 2/18 - AM temps in near zero to teens throughout the region rise to around 30 F in urban and waterfront areas, holding in low 20s in rural and northern locations. A WINTER WEATHER ADVISORY & WIND CHILL ADVISORY in effect for the Baltimore/Washington metro region from 2 PM to 9 PM tonight per Sterling NWS.
- THU 2/19 - Much colder, highs dropping back to the teens under clearing skies.
- FRI 2/20 - Super cold, AM lows below zero for many, highs barely hitting 10 F.
- WEEKEND - Snow showers possible on Saturday ahead of a developing Low in the Gulf coast. Sunday uncertain, possible light snow north and rain/snow mix in south
- NEXT WEEK - Continued cold with new indications of another potentially significant winter weather event for the period Feb 22-23 from the Tennessee Valley to the Mid-Atlantic and Northeast. However, precise details precipitation, intensity and timing are not clear this early in the forecasting process.
*Experimental variation of a long dormant tagline on this site from 2005 when it was known as "Basic Weather For Busy People."
"I want the truth!"
- Lt. Daniel Kaffee played by Tom Cruise, questioning Col. Jessup, played by Jack Nicholson, in the 1992 film A Few Good Men
3:30 AM 2/17 (Forecaster Mike & the Winter Stormcast Team) Is the truth better even if it's bad news, or can we rest in a little bliss for a while? That would be nice, but the weather pattern probably won't let us. As a deep freeze settles in ahead of a new Arctic front, we look ahead to the next few weeks. Some harsh realities are in store for us as an entire winter's worth of cold has been saved up for the final two weeks of February 2015.
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| Temperature Probabilities compared to normal for February 22-26 - Climate Prediction Center |
NOT OVER YET! As indicated above in the map by the Climate Prediction Center, the eastern United States is still seeing greater than 70% probabilities of below normal temperatures for the period Feb 22-26. Those sick of the cold and snow are not out of the woods just yet. This stubborn cold pattern will continue plowing the Eastern United States with cold wave after cold wave until early March. The first concern is a potentially record breaking blast of arctic air slated for Wednesday-Friday.
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| 0z 2/17 High-Resolution NAM model: Surface Temperature at 7AM Thursday (left), Simulated Radar at 4PM Wednesday (right) from PSU's e-wall. |
HERE WE GO AGAIN? The period from Tuesday afternoon through Thursday morning may play out similarly to last Friday through Sunday.
- Another Arctic cold front is on the way, set to arrive Wednesday evening. We are again watching the potential for some snow squalls to push through Wednesday evening like what we saw on Saturday, as illustrated in the model graphic above.
- However, Wednesday's snow squalls should not be quite as severe as Saturday's if they do occur. Saturday (2/14) had a little bit more warmth and moisture out ahead to work with, whereas the front arrive Wednesday (2/18) will be running into a colder and drier airmass.
- Behind this, we expect a new round of intensely cold Arctic air. The NAM model for Thursday morning shows temperatures back into the single digits across much of Central MD. But unfortunately, that's not all.
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| GFS Model Forecast 500mb Heights and Vorticity for Thursday 2/19 (left) and 500mb Heights on 1/6/14 (right) |
LOOK FAMILIAR? The pattern in the upper atmosphere for the second half of this work week resembles the upper level pattern from early January 2014. A huge dip in the jet stream is allowing a flow of cold air straight from northern Canada into the eastern United States. Only this time, the flow is heading straight into the east, rather than the Midwest and Plains as it was in January 2014.
"Thickness" is an effective measure of how cold the atmosphere is at a certain level. Basic gas laws tell us that as air warms, it expands. A warm atmosphere will be thicker than a cold atmosphere at the same pressure. When the air is warm, the air will thicken, and thus increase the distance between the 1000mb surface and the 500mb surface. Model projections for late this week show some of the lowest thickness values ever seen in the climatology moving into our region. This is indicative of a potentially record breaking cold air-mass.
GROUND TRUTH There are a number of factors that go into determining if the overall atmospheric configuration will actually translate to record breaking cold. Some are very precise, small changes, but can have big impacts on temperature. For example, clear skies allow the heat to escape the atmosphere, cooling temperatures. Snow cover better reflects energy back to space. Light winds prevent mixing of the layers of the atmosphere and allow the surface to cool rapidly whereas strong winds prevent this.
Surface temperature modeled by several global models even shows the major cities dipping below 0ºF late this week, but several also did for Sunday-Monday and we did not due to wind and clouds. This week will be extremely cold once again regardless of if temperatures are in below 0ºF or in the single digits. Please review some safety precautions on how to prevent pipes from bursting. Dress warmly, drive safely, the usual cold weather tips.
HOPE SPRINGS ETERNAL? Our Long Range Team is monitoring the potential for an abrupt end to winter this season, soon after we cross into March. It is possible that the super-ridge over the western United States that has been driving the weather pattern over North America since February 2013 may start to break down during the first or second week of March. Hoping for some warmth? Stay tuned for more details when our Long Range Team will post a new report outlining our next set of ideas on this!
(Forecaster Mike)