Category: General Weather

Another cold front will move into the West Coast on Saturday allowing for some showers in the Pacific Northwest during the day and then will move south overnight providing showers to California and other portions of the Western United States. The highest rainfall totals over the next 3 days will be along the coastal regions, but total projections look to be with the 1 to 3 inch range. Some snow showers are possible especially overnight and in the higher elevations of the Rockies as the front moves ashore. Many higher elevations should see 1 to 3 inches with a possibility of more through early Tuesday morning. Once again, this is good news for drought-stricken regions that are nearby mountainous regions, which can accumulate snow, so that when warmer weather comes back and allows for melting, it will create more drinking water and some of the runoff may go back into the water table and begin to replenish some lakes and streams.

It is interesting to watch the model projections for energy associated with this cold front in the future. The southern jet stream, known as the subtropical jet, has gotten going over the last week along the border of the Gulf States with the Gulf Coast, so as this cold front dives south along the northern jet stream these two jet streams will combine, which is known as phasing. Often when upper level jet streams phase, a strong low pressure system can develop with the increased wind aloft helping it to intensify or cycle. This occurs with the low pressure system that is projected to develop just east of the Rockies early Wednesday through Friday.

Winds rotate counter-clockwise around low pressure systems which allows for cool northerly winds to come into the United States. Sometimes the cooler temperatures can mix with more moist air and create snowfall over lower elevations especially at night when cooler temperatures can also result. This is what may happen on the west side of this system mid to late week next week in the Northern Plains. It is still too early to show model projections, but any accumulation looks to be light in the lower elevations.

In addition to the active weather coming up over the United States, the tropics have gotten active again. This is especially true in the Atlantic, where two areas are being watched over the next 5 days for tropical development. The first is in the western Gulf of Mexico, which has a low probability of development over the next few days. A low pressure system around 300 miles southeast of Brownsville, Texas resides there and thunderstorms have become more concentrated near this low. During the day today, a cold front will come near it and the area of storms will merge with it. The other area of storms has a better chance of development. It is a large area of showers in an area from the northeastern Caribbean Sea through the Lesser Antilles and into the Atlantic. Some gradual development of this disturbance is possible by early next week, but regardless, heavy rains are possible over the Lesser Antilles, the Virgin Islands, Puerto Rico and Hispaniola over the next few days. Any development of this system will be slow over the next few days.

Another batch of heavy, flooding rain occurred in Texas on Friday as strong low level winds flowed in from the south. Those winds combined with moisture that were both above normal for that region helped to aide in the development of strong showers over the region. Furthermore, a strong upper level jet was centered in the right place, over Texas, for strong large scale lift signified by strong upper level divergence. At one point, up to 10 inches of rainfall occurred in 2 hours in an area south of Austin, Texas. Many roads and bodies of water flooded with plenty of rainfall in a short period of time.

With all of this rainfall, one would have to assume that the drought would at least be alleviated somewhat, but unfortunately there is still drought to be contended with in the Texas. Even still, in one week, the rainfall has lessened some of the drought with some areas reaching as high as 5 classes of drought improvement in eastern Texas. Since October 20, Texas has seen as much as 20 percent of the state added to the no drought category in the drought monitor. At the same time, Texas now has none of its area in the highest 2 categories of the drought monitor. Even the areas with a class 2 drought have dropped into single digits for a percentage of the state. It still appears that around 28 percent of Texas is in a class 1 drought according to the drought monitor.

Also, strong shear near a warm front in the area combined with the already moist environment, allowed for numerous tornadoes within storms that formed inland as opposed to staying near the coast like last week’s event. Because of the strength of the severe event, a tornado watch that lasted the entire day and a severe thunderstorm watch for western Texas were issued by the Storm Prediction Center. The severe thunderstorm watch for western Texas was for the southern portion of a strong squall line that formed a bow like feature in it signifying strong straight-line winds in that region.

This area of low pressure will then move east northeast as the upper level trough that helps to create the forcing for the area of low pressure moves in that direction. During that time, it will leave a swath of 2 to 6+ inches of rainfall from Louisiana to southern Virginia. On Saturday, the low pressure system will continue to deepen, becoming a cold-cored upper level low pressure system and will have its winds, shear and instability die down along its east-northeast path as it moves more inland than it was Friday and Saturday.

While the tropics in the Atlantic and Pacific remain quiet, the Indian Ocean is active. A storm named Chapala is located 475 miles south-southwest of Masira Island near Yemen and is moving west at around 8 mph. Chapala has an 4.5 mile diameter pinhole eye and appears unaffected by nearby wind shear. Being steered by a ridge of high pressure just to its north, Chapala will make landfall over central Yemen as it tracks northwestward. It will then weaken as dry air and shear erode the system and interaction with land tears it apart.

As much as 10 or more inches of rain fell south of Dallas, Texas on Friday,  resulting in widespread flooding. This occurred as moisture was able to be pulled inland from the Gulf of Mexico along a low level jet that had a strength that was at times 2 to 3 standard deviations above normal. Also, surface moist convergence resided within an area that contained plentiful amounts of moisture in the form of precipitable water that was 2 to 3 standard deviations above normal. This all took place over the same area for most of the day. Additionally a cold front approached from the north and thunderstorm chances rose to the north of the area of convergence. As that cold front approached from the north, upper level divergence occurred in the right entrance region of the upper level jet allowing for large-scale upward motion. Consequently many cells were able to back-build and resided in the same place for long periods of time allowing for an over-saturation of the ground in those places and standing water for flooding.

Moving forward, model projections have plenty more flooding moisture coming into the Southern Plains, but it should remain further south this time. Major Hurricane Patricia, which rapidly weakened, but was above Hurricane status just before reaching landfall in Mexico, will have an effect on the Southern Plains. Patricia’s remnants will get drawn into the aforementioned jet stream and will add moisture to the rainfall along the southern shores of Texas. The upper level jet and its dynamics move away from the region, so the bulk of the precipitation will now be a result of the remnant low pressure system from Patricia. Precipitable waters will be up to 3 to 4 standard deviations above normal, which is higher than what was in North Texas. But, while the storm should have heavier rainfall rates with strong low level winds bringing more moisture in from the Gulf, a short time for precipitation occurrence will happen as the low pressure system moves away quicker than the stalled out boundary in North Texas. A severe weather threat also exists with increased shear paired with the strong moisture content. Generally, tornadoes occur in the right front quadrant of a low pressure system depending on the direction of movement because that is where the apex of the low level jet tends to be. So, a northward movement would allow tornadoes to occur in the northeast side of the low pressure system. The strong rain should be out of Texas by Monday morning. As the storm continues along, it will continue losing tropical characteristics and will move to the northeast and affect regions from the Gulf-bordering States to the Northeast through the middle of next week as the energy and moisture from Patricia combines with another trough to the north and swings to the north and east.

Speaking of previous tropical cyclone Patricia, there are only two named storms, including Patricia, from the Central Pacific to the Atlantic Ocean. As of late Saturday afternoon the remnants of Patricia were located about 45 miles southwest of Monterrey, Mexico. A low pressure system over southern Texas is also developing, but is expected to be non-tropical even with the remnants of Patricia being absorbed into it. The main threats continue to flooding and mud slides in Mexico and flooding and severe weather in Texas.

After a relatively warm summer and early autumn, some of the coldest air so far this season will sweep southward from Canada over the next several days.

A cold front will drop southward across the Plains and the Great Lakes on Thursday with a large high pressure area building in southward behind it. Scattered showers are expected ahead of the front, but they will be mainly light. The bigger story will be gusty northwest winds behind the front ushering the cooler air into the region. Frost Advisories and Freeze Watches have already been posted for Friday morning across portions of Nebraska, Kansas, and eastern Colorado, and more will likely be issued.

As the front marches eastward Thursday night and Friday showers will spread into the Northeast while the cold air pours into the Midwest. Rain could mix with some wet snow before ending across portions of northern Minnesota and the Upper Peninsula of Michigan. As high pressure builds in, skies will clear out across parts of the area and winds will diminish, allowing temperatures to drop into 20s and 30s across much of the Midwest. While a frost or freeze has occurred across northern parts of the region already, in southern areas, this will lead to an end of the growing season.

By Friday night the front will push offshore, but an upper-level low pressure area will settle into the region. This will likely trigger additional showers across parts of the Eastern Great Lakes and northern New England. Most of these will be light once again, but with colder air settling in, some wet snow could mix in, especially in the higher elevations of northern New England. Little, if any, accumulation is expected, except at the higher peaks. With the upper-level system nearby, Saturday will be a breezy and cool day across much of the region under partly sunny skies. As this system moves into southeastern Canada, high pressure will build into the Great Lakes, allowing skies to clear out. This may result in frost and/or freezing conditions across most of the Ohio Valley, the Appalachians, and interior Northeast, ending the growing season across much of the region.

By Sunday, high pressure slides eastward, allowing for a sunny but cool day across most of the Northeast. The exception will be across northern New England. With the upper-level low still nearby, rain and snow showers will continue across the higher elevations of Vermont and New Hampshire, as well as much of northern and western Maine. Accumulation of 1 to 3 inches are expected, with some heavier amounts possible in extreme northern Maine. Skies should become clear across most of the region Sunday night, and with diminishing winds, temperatures will drop quickly at night. A widespread frost and/or freeze is expected across much of New England, mainly away from the coastal plain. Temperatures may only drop into the middle 30s in the urban areas, but most of the suburbs will likely drop into the 20s to lower 30s by Monday morning.

As the high slides offshore, southwest to west winds will allow warmer air to move back in, with high temperatures bouncing back into the 60s and lower 70s by the middle of next week.

A low pressure system will move through the Northern Plains this weekend and into Monday with strong gusty winds. Sustained winds strong as 30 to 40 mph with gusts up to 50 mph  or more are possible into Monday in places such as Jamestown, North Dakota. One other factor that could help to exacerbate this even further is the fact that some areas, especially to the north, may see some rain from the low pressure system. Often winds get briefly stronger in rain as even stronger winds aloft would get brought down to the surface. Winds should die down in the Northern Plains late Monday into Monday night as the low pressure system and attendant cold front leaves the area.

It was a chilly weekend across the Northeast as Frost Advisories were issued over Southern New England Saturday night as dry air poured into the region behind Friday’s cold front. With the cold and dry air in place, radiational cooling allowed low to drop into 30s in many areas. Radiation cooling occurs where warmer air can escape readily into the upper atmosphere and cool more completely than if there were clouds around. Of course the urban heat island effect, elevation, proximity to warmer land masses like the ocean and soil type play a huge role helping to regulate how cold temperatures get.  For eastern areas of Massachusetts and eastern areas of New York, that recorded frost, this is right around the normal date for their first frost, which is around October 11-20. Western Massachusetts areas are only a day or two late with their first frost normally from October 1-10. Overall though, it is well on target with the average first frost. Temperatures should be on a warming trend ahead of Tuesday’s cold front.

In the tropics, the Atlantic region does not have any areas that are being monitored for tropical development, but the Pacific Ocean has Tropical Storm Nora. It crossed from the Eastern Pacific into the Central Pacific Saturday evening. Nora currently has maximum sustained winds around 65 mph. Satellite images showed a developing eye wall aloft. In the early part of its forecast, as it continues its westerly track, shear will remain low and warm waters around the storm will allow for further strengthening. By Tuesday, the westward trek of the storm will be changed to more northerly as a high pressure system to the north begins to break down and an area of low pressure approaches from the west. The northerly track would start to occur well east of the Hawaiian Islands. As Nora begins its turn north on Tuesday, an area of low pressure will also allow vertical shear to increase so a decrease in strength may occur after Monday and along its northerly track. The other area being monitored is currently centered about 600 miles south of Acapulco, Mexico. Environmental conditions are expected to be conducive for slow development and a tropical depression is likely to form late this week as it continues along its westward track.