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10-Day Outlook: Flashback to Winter...

Josh Larson @ 9:00 AM

Today's Forecast

Today's forecast calls for partly to mostly sunny and breezy conditions with highs near 55. Clouds will be on the increase as the day wears on. For the overnight hours, expect mostly cloudy skies and temperatures falling to the mid 30s. A light mix of rain and wet snow may develop towards dawn Friday.

Pattern Overview

Anyone who's lived through a March in Washington, DC should have known that the unseasonable warmth which we experienced over the past week simply couldn't last. In fact, it is beginning to appear to me that the 70s and 80s might just be a blip of extreme warmth in a month that featured a cold start and is likely to feature a cold finish.

Most model guidance suggests that below normal temperatures (on the order of 5-10+ degrees) are likely to hold for at least the next week to ten days, and might continue thereafter, though the end of the month. Though we're current running +5.9 degrees above average for the month, I suspect that by March 31 our departures may be near, or even slightly below, normal.

What's the reason for this rapid turn around back to much more wintry-like conditions? The blocking pattern which locked the cold air into the region during late February and early March has re-developed over Canada. In addition, the NAO is poised to return to "negative," which also supports cold air over our area. There are also some suggestions that a return to a more active storm track may allow for one or more areas of low pressure to travel east towards our region next week...

Image above: The CPC's SuperEnsemble model demonstrating the return of (#1) blocking over Canada by this weekend and, (#2) negative height anomalies (cold air) over the Northeast.

The next 5 days (Mar 16-20)

Forecast highs/lows: 49/31 (normal = 56/38)
Forecast precip: near normal

After today's highs in the mid 50s, expect less pleasant conditions on Friday: we may see a light mix of a little rain and wet snow during the early morning hours; no accumulation is expected in the immediate areas, but the far north and west suburbs might just eek out a coating on grassy areas. Overcast skies, with breezy conditions, will linger through much of the day, with highs only in the mid 40s. Clearing and colder overnight, with lows in the mid to upper 20s. Saturday and Sunday will feature nearly identical conditions: mostly sunny skies, a light breeze and highs in the upper 40s, with overnight lows in the mid to upper 20s. For Monday, expect more of the same, with plenty of sunshine and highs near 50.

The next 5 days (Mar 21-25)

Forecast highs/lows: 48/32 (normal = 58/39)
Forecast precip: above normal

Now for the tougher part of the forecast -- the following five days. Model guidance suggests, with relatively high confidence, that a complex, major area of low pressure will trek towards the east coast during the Tuesday-Wednesday period. Precipitation type is uncertain at this point; however, as noted in previous posts, climatology now disfavors (accumulating) snow for the immediate area. (See Snow Lover's Crystal Ball below.) At any rate, it appears that highs both Tuesday and Wednesday may not make it out of the 30s (depending on cloud cover and precipitation) with overnight lows in the upper 20s to lower 30s! Temperatures will moderate somewhat to the mid 40s by Thursday, with overnight lows in the 20s. Further moderation in temperatures is expected by the start of next weekend, when highs will approach 50 (still below average), with lows mostly in the 30s.

Snow Lover's Crystal Ball

Chance of Accumulating Snow: Tues, March 21
Probability: 20%
Potential Impact:

Commentary: There is relatively high model agreement that a major area of low pressure will trek from the central US towards our area during Tuesday and Wednesday of next week. It appears likely that we'll see some form of precipitation out of this system, though timing (overnight versus daytime) will likely be the key to whether we see frozen precipitation. Models do disagree, however, on the extent and magnitude of cold air, so rain, snow, or ice (or some combination) are all possible. My own gut feeling is that this may be a rain to snow scenario. Only time will tell...

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