March Rainfall Records Doused; Damaging Freeze Possible in Northeast

More severe weather is in store for Thursday and Friday after tornadoes hopscotched near and east of Tulsa on Wednesday and flooding rains inundated other areas. A damage survey was underway in northeast Oklahoma on Thursday morning in the wake of the tornadoes, which caused at least seven injuries and damaged a number of structures. One of the twisters was visible from Tulsa International Airport (see video here, from Twitter user Brandyn). In its roundup of severe weather reports from Wednesday, NOAA’s Storm Prediction Center (SPC) listed four preliminary tornado reports from the storm near Tulsa, along with two other reports from southeast Kansas and southeast Arkansas.

The greatest threat for severe weather Thursday afternoon and evening is across northern Mississippi, northwest Alabama, and western Tennessee, where the 11:30 am CDT outlook from SPC is calling for an enhanced risk of severe weather (Figure 1). An outflow boundary from previous storms is stretched east-west across northern MS and AL. As upper-level energy approaches, this boundary will serve to enhance vertical wind shear, and a strong tornado or two could develop in supercells that form near the boundary. The upper-level trough and associated cold front will slide across the central Gulf Coast on Friday, leading to a continued risk of severe weather in that area--primarily high winds and large hail, together with heavy rain. Severe storms are also possible northward along the cold front to the mid-Atlantic, particularly in the Piedmont of Virginia and North Carolina if temperatures warm enough there on Friday.


Figure 1. The convective outlooks issued by NOAA’s Storm Prediction Center late Wednesday morning, March 30, 2016, included an enhanced risk area for Wednesday centered on northern Mississippi and a slight risk for Thursday near the central Gulf Coast.


Figure 2. A tornado touches down in the vicinity of Tulsa, OK, on Wednesday, March 30, 2016. Image credit: AP Photo/Larry Papke.

Wettest March on record for Memphis, Little Rock
Today’s rains will serve as a capstone to a March that already ranks among the wettest on record for states bordering the lower Mississippi River. As of midnight Wednesday night, Memphis, TN, was sitting at 13.78” for the month. This already beats the previous March record of 13.04” from the region’s devastating spring of 1927, which brought the worst river flood in our nation’s history. Memphis records go back to 1872. In Little Rock, AR, an even 4.00” on Wednesday led to widespread flooding across the area. Little Rock has now racked up its wettest March by far since records began in 1875, with 12.22” this month beating out 10.43” (1897). Both Memphis and Little Rock will have added to their March totals before the day and month are done; Memphis will go up by at least 2.00” based on rains that had already fallen by midday Thursday.


Figure 3. Temperatures projected from this morning’s 12Z Thursday run of the GFS model for 12Z (7:00 am CDT) Tuesday, April 5, 2016. Image credit: Levi Cowan, tropicaltidbits.com.

Widespread freeze damage possible next week across East
Early April may bring a cruel surprise to many trees and shrubs that popped into premature bloom over the last several weeks across the Northeast. It finally dipped below freezing on Wednesday morning in Baltimore and in areas just west of I-95. However, from New York southward, it’s still been nearly a month since most of the urban corridor has seen a hard freeze. In New York and Philadelphia, the last temperature below 32°F was back on March 5, although Central Park touched 32° on March 20 and 21. During the 1981-2010 climatological period, the average date for the final reading of 31°F or colder in Central Park was on March 13. Making matters worse--though it seemed pleasant enough at the time--was the spell of record-smashing mid-March warmth that sent temperatures into the low 80s in parts of New York and New England.

The lack of snow cover over the Northeast has allowed soil temperatures to warm as well, which hastens the budding and blooming of trees. The mildness has advanced New Jersey’s growing season by several weeks, state climatologist David Robinson (Rutgers University) told AgWeb. Plum and peach trees in the Lehigh Valley of Pennsylvania were already in bloom this week. In Washington, D.C., the famed yoshino cherry blossoms of the Tidal Basin hit peak bloom on March 25, almost two weeks before the April 4 average and earlier than in all recent years, with the notable exceptions of 2012 (March 20) and 1990 (March 15).


Figure 4. Temperatures across the entire nation except for the Pacific Northwest coast were well above average for the period March 1 – 29, 2016. Image credit: NOAA/NWS/CPC.


Several rounds of cold weather are on tap for the mid-Atlantic and Northeast over the next few days. Temperatures may dip to near freezing from D.C. northward on Sunday morning, with colder readings well into the 20s possible across much of the area by midweek (see Figure 3 above), and perhaps again by next weekend. Although these readings are 20°F to 30°F below average, they’re unlikely to set very many record lows: the latest 32°F temperatures on record are April 29 in Washington, May 11 in Baltimore and Philadelphia, and May 6 in Central Park. However, the impacts of the coming cooldown may be more akin to getting a freeze in mid- to late April, given the advanced state of plant growth over the region. The situation brings to mind the disastrous freeze of April 11-12, 2012, which followed the unprecedented Great Warm Wave of March. That freeze, together with frosts later that month, devastated already-blooming fruit trees across the Midwest and Northeast. In Michigan, the apple crop was virtually wiped out.

WU weather historian Christopher Burt has a new blog post summarizing where California stands in terms of snowpack and precipitation after a not-quite-miraculous March.

Bob Henson


Figure 5. Dogwood blossoms on Wednesday, March 30, 2016, in Danville, VA. Image credit: wunderphotographer WeatherWise.