Monday is Patriot's Day in Boston, MA in commemoration of the events there in 1775 that ultimately led to the Revolutionary War.
WEATHER OVER THE WEEKEND -- Following the stormy end to last week, the just concluded weekend was relatively quiet across much of the country, at least in terms of major storm systems or wide-spread severe weather. The storm over the Great Lakes that was responsible for the severe weather, to include killer tornadoes across the Southeast, continued to move eastward and weaken on Friday and Saturday. By late Saturday night, essentially all vestiges of this storm's low pressure center had disappeared over the eastern Great Lakes. Even during its latter stages, this storm helped drag unseasonably cold air across the western Great Lakes and upper Mississippi Valley. Northwesterly winds gusted to 50 mph at various locations on the western side of the low. Some locations across Iowa had as much as two inches of snow on Friday. Rain was found farther east. Oklahoma City received a trace of snow, a record for the date.
Across the West, a large ridge of high pressure had become entrenched in the Great Basin. Along the east flank of the high, numerous record low temperatures were found from the Great Basin eastward across the east slopes of the Rockies and into the Plains as a combination of clear skies produced radiative cooling and northerly winds brought cold air southward. Some subfreezing temperatures were found across southern Texas, such as a record 31 degrees at San Angelo on Friday morning. The record low of 19 degrees at Grand Junction, CO was not only a record for the date, but a record low for so late in the season. Some locations in Texas, such as Beaumont, set record low maximum temperatures, as little heating took place during Friday afternoon. A similar situation was found Saturday as many record low temperatures, included some that were below freezing across the Texas Hill Country, such as Austin, where the minimum was 31 degrees, the latest freeze ever for the capital city. Victoria, TX had a 38 degree reading, the latest time in spring that the temperature fell below 40 degrees. On Sunday morning, several locations across south Texas and Louisiana had record low temperatures. In addition, the relatively dry conditions, as indicated by very low dewpoints, permitted record lows to fall across the Florida Panhandle and several locations across Georgia and the Carolinas.
On the west flank of the ridge, the offshore flow together with sinking air produced another day of record high temperatures again on Friday along the West Coast. Record high temperatures were set as far north as Seattle, where the 81 degree high represented the first time that 80 degrees was reached this year. Los Angeles had a record high of 90 degrees. On Saturday and Sunday record high temperatures were also set across southern California, while farther north the ridge was no longer sufficiently strong to maintain the records.
Many locations across the Florida Peninsula continued to experience wildfires associated with the drought. On Friday, a 23,000 acre wildfire at Port St. Lucie destroyed more than 40 homes. While rains on Saturday helped in certain areas, by Sunday more than 70,000 acres of southern Florida burned, to include portions of the Everglades. The dense smoke forced closing of I-75 east of Naples, a section also known as Alligator Alley.
Unseasonably warm weather continued over the weekend as a 94 degree record high was set at Friday at West Palm Beach and several record highs were set on Saturday to include a 90 degree reading at Miami and Hollywood.
High temperatures on Sunday across the Eastern half of the nation were well below the average highs for this time of year. Many locations had temperatures that were as much as 15 degrees below the average highs. Across the Rockies and the Far West, afternoon high temperatures were as much as 15 degrees above the average highs.
WEATHER FOR STARTING THE NEW WEEK -- The weather across most of the contiguous US was relatively tranquil late Sunday night, with no major storm systems. A weak low pressure system was moving southeastward across the eastern Dakotas. This Alberta-Clipper-like system had a warm front that extended to the south into western Iowa and a cold front that trailed westward into the Wyoming where the front turns into a stationary front that continues to the northwest through Montana to another low in northwestern Alberta. Light rain associated with the weak low in the Dakotas stretched across Minnesota. This system should continue to the southeast, reaching south central Iowa on Monday morning. Light rainshowers are expected across the Upper Mississippi Valley and western Great Lakes.
A weak trough line, marked by light precipitation was moving through the eastern Great Lakes and the Ohio Valley. Light rain is expected to continue across the region into Monday morning.
One other area of precipitation found in the country on Sunday night was located over eastern Washington State and the northern Idaho Panhandle. Showers are expected to continue across the northern Rockies and the high Plains of Montana east of the Divide through Monday morning as a weak wave of low pressure is anticipated to form along the stationary front along the US-Canadian border. A cold front that was located several hundred miles off the Washington State coast may produce some light rain along the coast early Monday.
Elsewhere, high pressure contributed to relatively cloud-free skies. A large ridge of high pressure was located over the Gulf Coast. Unfortunately, this region continues under drought conditions and little rain is expected in the near future. The rain showers and thunderstorms that accompanied the cold front have moved into the Florida Straits south of Florida.
Another sprawling ridge of high pressure remained centered over the Great Basin and southern Rockies. Little change is expected in the position or the intensity of this system into Monday. Unseasonably warm conditions are expected along the West Coast under sunny skies on Monday.
UPPER AIR -- Both the 500 mb and 300 mb charts for 00Z Monday reveal a wave pattern in the mid to upper tropospheric flow that has a ridge in the West and a trough in the East. This pattern is associated with the warm lower troposphere in the West and a cool near-surface pool of air to the east. As a result, the westerly winds arriving along the West Coast are deflected slightly to the north, moving around the northern crest of the ridge of higher heights in the respective constant pressure surfaces that is located over the northern Rockies. To the east of the mountains, a northwesterly flow is found over the Plains at both 500 and 300 mb levels. The winds turn easterly as they reach the southern base of the trough of lower heights located over the Great Lakes and the Ohio Valley. East of the trough, winds show a slight turning toward a east-northeastward direction.
TEMPERATURE EXTREMES IN THE COTERMINOUS U.S. -- The lowest temperature on Sunday was 18 degrees at Gallup, NM and Gunnison, CO, while Sunday's highest temperature was 101 degrees at Thermal, CA.
ALASKAN WEATHER -- A storm system with multiple low pressure centers located over the Gulf of Alaska spread clouds along a frontal band that stretched across coastal regions of southern Alaska from the Aleutians to the Panhandle. Precipitation fell mainly in the form of rain around Kodiak, Prince William Sound and the Panhandle. Mixed rain and snow fell at Cold Bay. Another storm along the Arctic Coast with a trailing cold front that stretched southwestward to the Seward Peninsula was responsible for snow at Kotzebue, and with winds gusting to 40 mph, blowing snow at Gamble and Tin City. Weak low pressure over the Bering Sea produced snow at Adak.
Weak high pressure that extended westward from Canada produced clear skies across eastern interior portions of the state. As a result of the sunny skies and weak winds, afternoon temperatures were unseasonably warm over the Tanana Valley and other areas in interior Alaska. Yakutat reach a record tying high of 57 degrees on Saturday. On Sunday record high temperatures were either tied or set at Eielson AFB (68 degrees), Fairbanks (65 degrees), Big Delta (62 degrees), Northway (57 degrees), Tanana (56 degrees) and Denali Park (55 degrees).
The lowest overnight temperature as of Sunday in the state was 9 degrees below zero at Point Hope. By midafternoon, the highest statewide temperatures was 68 degrees at Eielson AFB.
HAWAIIAN WEATHER -- A band of showers that was once part of an old front moved across the islands on Saturday and Sunday. An increase in the trade winds is expected from Sunday night into Monday as a ridge of high pressure builds to the north of Hawaii. Brief trade showers should fall, but mainly overnight and during the morning.
BECOMING AWARE -- During this coming week of 18 - 24 April, Minnesota, North Dakota, South Dakota, Wisconsin in the NWS Central Region along with Maryland and the District of Columbia in the Eastern Region will conduct their Severe/Hazardous Weather Awareness Week. In Wisconsin the week is also known as Tornado & Severe Weather Awareness Week. These weeks are usually scheduled before the onset of the severe weather season in that particular state. If you live in any of these states, you should take time to become familiar with the various public affairs announcements issued by your local National Weather Service Office. In upcoming weeks, other states will observe Severe Weather Awareness weeks.
SEVERE WEATHER TERMINOLOGY -- For a description of the terminology used in the official statements issued by the National Weather Service to inform the public of severe local storms, please read Monday's optional 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.