* Relatively Dry Pattern for April into Next Week *

11:00am Thursday, April 17:
The first 15 days of April averaged 3 degrees above normal--the first above-average two-week period since the latter part of December. Of course, Tuesday's sharp cold front ushered in a brief shot of unseasonably cold air...and a light Onion Snow Tuesday night in parts of southern and eastern LanCo. Wednesday's high temps struggled to reach the mid 40s--a remarkably chilly day considering that the current sun angle is the same as late August! Fortunately, a rather zonal jet stream pattern means that any cold shot will be short lived. Consequently, a moderating trend begins today and it will lead to a return of mild conditions in the coming days. In general, I expect the second half of April will continue in a similar fashion to the first half of the month with mild days outnumbering cold days.

Looking ahead to the weekend, high pressure now over New England will slowly retreat off the coast. Daily high temps should increase a few degrees day over day, and thus be back to normal levels (low to mid 60s) for the weekend. The only slight flies in the ointment are weak easterly flow that may result in some morning clouds on Friday and/or Saturday and a weak upper-level disturbance passing through with some clouds Friday night. Otherwise, it looks like a decent weekend with dry conditions, cool mornings, and mild afternoons.

A Pacific disturbance passing nearby next Tuesday will bring the next threat of showers. While a chilly north wind may develop behind this system, I do NOT expect a cold shot of the same caliber as this week's. Zonal flow will then quickly turn flow out of the southwest, and so we have a good chance of temps returning to the 70s for a day or two later next week. Overall, it looks like an uncommonly nice pattern for April with a relative lack of April Showers.

2:00pm Monday, April 14:
Today is the fourth consecutive day with temps in the 70s--something we haven't experienced since the first week of October--and so it feels like a long-awaited reward after the coldest winter in 20 years. Unfortunately, April warm spells almost never last, and accordingly the current warm stretch is on its final day.

A slow-moving cold front will cross our area early Tuesday afternoon. Ahead of the front tonight and early Tuesday will remain quite mild with temps in the 60s, despite the arrival of showers overnight. Periods of rain Tuesday may turn briefly heavy as the cold front moves through Lancaster between 2 and 4pm. The passage of the front will be quite notable as winds shift from the south to out of the west and temperature drop upwards of 20 degrees is just a few hours. So while midday temps will still be in the low to mid 60s, late afternoon temps will be in the 40s and evening temps in the 30s! Rain will taper off Tuesday evening, perhaps with a few wet snowflakes mixing in at spots.

Tuesday night into Wednesday will be windy and as unseasonably cold as today is unseasonably warm. Despite lots of sunshine on Wednesday, highs will struggle to reach the upper 40s to near 50--that's about 15 degrees below normal. Overnight lows will dip into the mid 20s in outlying areas to near 32 in the city, so a frost/freeze is likely in many location, especially Thursday morning. Thursday will be less extreme with high temps rebounding into the mid to upper 50s.

A look ahead to weekend...I see a return of more zonal flow and near-average temperatures. A couple of passing disturbances may bring a few showers sometime Saturday and Monday/Tuesday, although neither system looks particularly strong at this time. Temperature-wise, I expect conditions to vacillate within 5 or 6 degrees of average. Therefore, I don't see a near-term return of highs in the upper 70s nor in the upper 40s. All in all, we've settled into a fairly typical early Spring weather pattern.

Issued: 4-17-14 (Horst)