QUIET WEATHER OVER MUCH OF THE NATION -- A large ridge of high pressure that was centered over the Mid-Mississippi Valley on Monday night was a dominating influence on the weather across a large portion of the country, extending essentially from the Eastern Seaboard to the Rockies. As a result, little precipitation was found except with a storm system across the Southwest. Little movement of this system is expected through Tuesday morning.
Earlier in the day, snow fell across the higher elevations of northeast Pennsylvania, southeastern New York State and southern New England as a storm system moved eastward over the Atlantic to the south of Nova Scotia. Some lingering cloudiness was all that remained by Monday evening. However, the pressure gradient between the high in the Midwest and the departed low produced strong northerly winds from New England south to the Southeastern States. Some wind gusts were as much as 30 mph. The northerly winds were also bringing cold air southward. The cold front marking the leading edge of the cooler air had moved southward to South Florida by Monday night.
With relatively clear skies and weak surface winds near the center of the high pressure cell, overnight radiative cooling should cause temperatures to tumble across the Ohio Valley. As a result, a frost advisory is in effect for eastern Kentucky for Monday night and Tuesday morning.
THE HEAT GOES ON -- Persistent high pressure across Florida has produced very dry conditions, with high fire danger. Sufficiently strong westerly winds have not permitted development of the afternoon sea breeze circulation regimes that carry humid Atlantic air in from the east and contribute to the shower and thunderstorm activity over the Peninsula.
With sunny skies and lack of surface moisture, record high temperatures were either tied or set on Monday across the Florida Peninsula at Orlando with 93 degrees, Dayton Beach and Hollywood (Treatment Plant) both with 92 degrees, Fort Lauderdale (Water Treatment Plant) and Miami Beach with 91 degrees. The record tying high temperature at Orlando marked the fourth consecutive day that a record was either tied or broken, while the high at Dayton Beach was the third day out of the last four were a record was tied or exceeded.
With passage of the cold front across much of Florida on Monday, the high temperatures across the Peninsula should not reach record levels on Tuesday, as winds turn more northerly and a cooler air mass pushes south.
A QUIET FRONTAL PASSAGE IN THE NORTHWEST -- A cold front trailing a low entering into British Columbia moved into interior sections of Washington State, Oregon and northern California on Monday. However, with the exception of some precipitation around Puget Sound, little precipitation accompanied the frontal passage. As this front continues to move eastward across the northern Rockies on Tuesday, some snow is expected across the mountains of western Montana.
WINTRY WEATHER ACROSS THE SOUTHWEST -- A storm system that was located over northern Arizona on Monday night continued to spread precipitation across areas of the Southwest on Monday night. Many locations along the Lower Colorado Valley from Southern California into Arizona received heavy rain and mountain snow. Earlier on Monday morning, parts of I-5 south of Bakersfield were closed because of the snow. Several locations in the San Bernardino Mountains received as much as 10 inches of snow.
Farther east, several severe thunderstorms developed on Monday night and moved across southeastern New Mexico and west Texas over the Big Bend National Park and the Permian Basin near Midland.
The surface low is forecast to move eastward on Tuesday, with the morning position near the Four Corners. The precipitation is expected to spread eastward, with light snow across the higher terrain of northern Arizona and southern Utah, as well as the San Juans of southern Colorado. A slight risk of severe thunderstorms should continue on Tuesday across much of west Texas, from the Panhandle south to the Rio Grande.
UPPER AIR -- The 500 mb chart for 00Z Tuesday showed that a cold pool of air remained over Southern California up through the mid-troposphere. A closed region of lower heights on the 500 mb constant pressure surface corresponded with a region of counterclockwise circulation of the winds at that level and the surface low pressure system over northern Arizona. A moderate ridge is found over the center of the country, while a trough in the height is situated off the East Coast. Northerly winds over New England circulate around the trough off the coast. This trough is associated with the departed storm system now located over the Atlantic southeast of Nova Scotia.
The 300 mb constant pressure surface at 00Z Tuesday also shows a similar topography, with height troughs on both coasts, separated by a weak ridge in the center of the country. A strong westerly jet with winds reaching 130 knots over the Ohio Valley extends across the mid-section of the country.
TEMPERATURE EXTREMES IN THE LOWER 48 -- The lowest temperature in the lower 48 states on Monday was 6 degrees at West Yellowstone, MT and Monday's highest temperature was 94 degrees at Orlando, FL.
ALASKAN WEATHER -- Several low pressure systems over southern Alaska maintained clouds over a large portion of the state on Monday afternoon. One low pressure center was located to the south of Prince William Sound. Another low was centered within 200 miles southwest of Cold Bay, while a third low was situated over Adak in the Aleutians. A fourth low pressure system was situated over the Seward Peninsula. However, most of the precipitation occurred along the Panhandle in the southeast as onshore southwesterly winds brought moist air onshore. Sitka, Annette and Juneau each had more than 0.15 inch of precipitation since the start of Monday.
The statewide lowest overnight temperature reported on Monday was 20 degrees below zero at Wainwright. The highest Alaska temperature as of midafternoon was 44 degrees at Skagway.
HAWAIIAN WEATHER -- An upper level trough has helped produce unstable atmospheric conditions over the islands on Monday, leading to heavy showers and some isolated thunderstorms over the windward and mountainous areas of Maui and the Big Island. These showers are expected to decrease on Tuesday. The ridge of high pressure located to the northeast of Hawaii should continue to weaken. As a result, the strong and gusty trade winds began to weaken and the gale warnings that had been effect the entire weekend for the channels to the east of Molokai were canceled by sunrise on Monday morning. However, moderate trade winds are expected to continue due to an east-west oriented ridge of high pressure farther to the north. Small craft advisories remain in the effect for state waters.
On Sunday, Hilo experienced record cool and wet weather. A daily record 3.51 inches of rain fell and the high temperature for the day was only 68 degrees, which not only was a daily record lowest maximum temperature for the date, but also for the month of April. The all-time record lowest maximum temperature for Hilo was 67 degrees set on 7 March 1952.
WINTER STORMS --- A winter storm is a widespread set of weather conditions with winter-type precipitation - snow, ice pellets or freezing rain - often accompanied by strong winds and cold temperatures. They may form any time from late autumn through spring and affect, not just the northern states, but everywhere from the West to the Gulf Coast. They can range from a minor annoyance to the "Storm of the Century" that paralyzed the Gulf and East Coast in March 1993. In 1997, 141 deaths across the United States and territories were attributed to winter weather (84 winter storms, 6 ice storms, 51 cold-related deaths). The 90 deaths due to winter storms (snow and blizzards) and ice storms were second that year to the 118 lives lost due to floods. Winter storms also caused 573 injuries, second only to tornadoes (1,033 injuries).
For a description of the terminology used in the official statements issued by the National Weather Service to inform the public of adverse winter weather conditions, please read the Tuesday optional electronic Supplemental Information.
From the files of the Aviation Weather Center, Kansas City, MO and Intellicast
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Prepared by Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 1999, The American Meteorological Society.