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Weather Outlook for Hawaii and Southern Nevada for April 17th, 2019



Hawaii Outlook


Synopsis

Light to moderate trades will continue through Wednesday, then become breezy through the second half of the week and upcoming weekend as a ridge of high pressure builds to the north. Clouds and showers will favor windward locations each day.


Discussion

The latest surface analysis showed a weakness within the ridge due to a cold front passing to the north. This weakness has led to light to moderate trades across the islands. The bulk of the late afternoon/evening showers were focusing over windward locations with minimal rainfall accumulations over most areas. Peak accumulations over the past six hours (through 7 PM HST) have been over the Big Island and Maui with values ranging from half of an inch to near an inch (peak was .90 inches at Kawainui Stream on the Big Island). Shower coverage may increase over windward areas overnight into early Wednesday morning due to a weak upper trough moving through.


The latest short-term guidance is lining up well the current pattern and supports light to moderate trades continuing Wednesday, then becoming breezy Thursday through the weekend as the ridge of high pressure builds to the north. The weak upper trough over the state will linger in the area through Wednesday night, which may translate to better windward shower coverage through the overnight and early morning hours. Guidance depicts rising upper heights by Thursday as the upper trough shifts east of the area. This combined with breezy trades and 1-1.3" (near to below average) precipitable water (PW) values will lead to a more stable and dry pattern, with no significant changes expected through the weekend. For the extended (early next week), guidance remains in decent agreement and depicts a mostly dry and stable pattern with breezy trades continuing.


Southern Nevada Outlook

Synopsis:

A warming trend will commence today through Friday as a large ridge of high pressure builds over the region. Temperatures by Friday and Saturday will average 10 to 15 degrees above seasonal normals. As increased troughing develops over the West on Saturday, widespread gusty winds will develop followed by cooler temperatures Sunday into early next week. Discussion: Through next Tuesday.


Low pressure system which brought widespread shower and thunderstorm activity to the region yesterday is now exiting to our east, currently centered over eastern Arizona. As it pushes into the Plains states today, strong ridging will build over the Southwest through Friday. This will result in a sharp warming trend, with daily highs climbing several degrees each day. By Friday afternoon, temperatures across the region will likely reach their warmest levels observed yet this spring. The first 90 degree day of the year still looks likely in Las Vegas on Friday, along with the first 100 degree day in Death Valley.

On Saturday, heights will begin to fall as broad troughing develops and a couple of weak short waves progress through the Great Basin. While these waves will not be particularly strong, they will work to increase surface gradients across the region and drag a weak cold front through on Sunday. Ahead of the front, widespread gusty southwest winds look likely, particularly along the I-15 corridor and favored downslope regions of the Spring Mountains and Sierra. It`s possible a few wind headlines may be needed for these winds later in the week. Temperatures on Saturday will remain warm in a well-mixed, prefrontal environment, but should cool a degree or two over values expected on Friday. As the cold front slides through the area Sunday morning, cooler temperatures are expected for Sunday along with northerly breezes. The cool off will be short-lived however as renewed ridging builds in next week with temperatures rising above normal once again.

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