WET WEATHER CONTINUES ALONG THE GULF COAST -- A large precipitation shield moved very slowly across the Gulf Coast. Because of the lack of significant movement, several locations received more than two inches of rain on Tuesday. As of late Tuesday night, this arc-shaped area was spread over much of Alabama and Mississippi, as well as portions of Georgia, the Florida Panhandle and Louisiana. The precipitation, to include rain and imbedded thunderstorms, was associated with a nearly stationary low pressure sytem that was located along the Louisiana coast just to the west of the Mississippi Delta.
A persistent southerly, onshore wind to the east of the surface low necessitated posting of coastal flood advisories from Destin, FL to Pascagoula, MS. This low pressure system and accompanying precipitation shield are expected to drift slowly to the northeast on Wednesday morning
PLEASANT WEATHER ACROSS THE SOUTHEAST -- High pressure remained a fixture over the Carolina coast on Tuesday. As a result of the clear skies and weak winds near the center of high pressure, as well near seasonal temperatures, the Southeast experienced pleasant spring weather. Little movement of this high pressure cell is anticipated by Wednesday.
A WARMING ACROSS THE PLAINS -- An elongated low pressure system situated along a frontal zone over the western Dakotas helped spread warm air across the Plains and the upper Midwest on Tuesday. This frontal zone running from the Great Lakes to southern Nevada separated warm air to the south and east of the front from colder air to the north and west.
A warm front extended east-northeastward from the surface low center to northern Lake Michigan. This front marked the leading edge of warm air that was streaming northward on strong southwesterly winds. A strong pressure gradient between the high pressure cell over the Middle Atlantic states and the low in the Dakotas, as indicated by the relatively tight packing of the isobars on the surface analyses, produced the strong southwesterly winds. Winds gusted to at least 50 mph across the region. Rochester, MN had a 46 mph gust. In addition to this warm air advection, adiabatic compression and warming of the air in the downslope flow across the Plains from the higher terrain of the Rockies contributed to this warming. Afternoon high temperatures reached the 70s and 80s across the Plains and Midwest, at least 20 degrees above the 30 year climatological average high temperatures for the date. Many stations across the upper Mississippi Valley and western Great Lakes reported temperatures that were an unseasonable 60 degrees well into the nighttime hours.
A cold front extended southwestward from the low pressure center. Colder air was located to the north and west across the northern Rockies. Light snow fell across the Bitterroots of western Montana.
The low pressure system and accompanying fronts are forecast to move eastward across the Plains, with the center of the low expected over eastern South Dakota by sunrise on Wednesday. As the cold front passes, slightly cooler temperatures should result across the Plains.
As the system moves eastward, more moisture should be ingested into the system, increasing the chance of precipitation. Strong thunderstorms could develop to the south of the front from the Rockies to the Midwest on Wednesday. A slight risk of severe thunderstorms is possible across Nebraska.
WET WEATHER IN THE PACIFIC NORTHWEST -- Widespread precipitation in the form of low-elevation rain and higher-elevation snow continued over western Oregon and northern California on Tuesday. A weak low pressure system was situated along the central Oregon Coast as of late Tuesday night. In addition to the precipitation, chilly weather was found across California and the Pacific Northwest. On Tuesday morning the overnight low temperature at Redding, CA fell to 32 degrees, tying a low temperature record for the date. On Tuesday afternoon, a cooperative observer station at Shelter Cove, along the northern California coast (south of Eureka) had a daily high temperature of only 46 degrees, setting a low maximum record
Large ocean swell that reached heights of 20 feet, in addition to strong winds, produced heavy surf conditions along the California coast on Tuesday. As a result, heavy surf advisories remained in effect from Point Arena to Point Piedras Blancas through Wednesday.
The inclement weather is expected to continue into Wednesday, as the weak low pressure center moves inland into eastern Oregon. A large shield of precipitation is forecast to spread across Washington, Oregon and northern California into the Great Basin.
The high of 87 degrees at Safford, AZ tied the record high temperature for the date.
TEMPERATURE EXTREMES ACROSS THE LOWER 48 -- On Tuesday, the lowest temperature reported in the continental U.S. was 16 degrees at Klamath Falls, OR. Tuesday's high was 91 degrees at Coolidge, AZ.
ALASKAN WEATHER -- A large ridge of high pressure with a center located over the Arctic Ocean north of Wrangel Island extended southeastward across northern Alaska into northwest Canada. As a result, cloud-free skies were found across many areas of Alaska to include much of the North Slope, the central and eastern interior, the Copper River Basin, the north Gulf coast and the southeast.
A storm system approached southwest Alaska from the Bering Sea, with the primary low pressure center situated over Bristol Bay as of late Tuesday afternoon. This low was connected to a secondary low located near the Kodiak Island by an occluded front. Cloudy skies were reported over a region that stretched from the western Aleutians to south central Alaska and north into the Yukon-Kuskokwim Delta. Clouds were also reported across northwest Alaska and the Seward Peninsula. Light snow fell at Barrow, Dillingham, Homer and Seward. Windy conditions accompanied the storm system in southwest Alaska. Cold Bay had gusts to 44 mph, while Dutch Harbor experienced 33 mph gusts.
The lowest overnight temperature in the state as of Tuesday was 44 degrees below zero at Umiat. The state high by midafternoon was 50 degrees at Klawok.
HAWAIIAN WEATHER -- A large ridge of high pressure was located within a thousand miles to the north-northeast of Honolulu on Tuesday afternoon. The presence of this high helped produced gusty trade winds and trade showers especially on the windward sides of the islands. A weakening of the trade winds, along with fewer showers, is expected as the high weakens during the second half of the week. Gale warnings for winds with speeds ranging between 39 to 54 mph were posted for all inter-island channels. Small craft advisories remained in effect for coastal waters.
THE BLUE MOON --The moon is at full phase today, Wednesday 31 March 1999 at 2249Z (or 5:49 PM EST and 4:49 PM CST). Since this full moon represents the second full moon of the month of March, it is called a "Blue Moon", an event that occurs every several years . More unusually, this month is the second time this year when a "blue moon" has occurred, since this past January also had two full moons. The occurrence of two months with blue moons in the single calendar year occurs once every 19 years. Apparently, the expression "blue moon" refers to the relative rarity of the event, and not to the bluish color of the lunar disk caused by haze that occasionally is observed following a large series of forest fires. An article in the May 1999 issue of the popular magazine Sky & Telescope investigates the background for the term.
In addition, today's full moon is the "Paschal full moon" represents the first full moon after the vernal equinox and defines the religious feasts of Passover and Easter, which also occur this weekend. For further details, please consult the optional Monday's Supplemental Summary Information .
WIND OBSERVATIONS -- For a look at how the horizontal wind direction changes as you go up in the lower troposphere, see the Wednesday optional Supplemental Information on the Ekman spiral.
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.