WEATHERAmerica Newsletter, Saturday, May 31, 2008 at 6:35 P.M. CT

by LarryCosgrove | May 31, 2008 at 04:06 pm

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WEATHER HAZARDS (During The Next 24 Hours)

SEVERE WEATHER OUTLOOK
(potential for tornadoes, damaging winds, and large hail within the next 24 hours)
ISOLATED Severe Thunderstorms
(Microbursts, Large Hail, Isolated Tornadoes)
E WA....E OR....ID....W MT....S BC

SCATTERED Severe Thunderstorms
(Microbursts, Large Hail, Isolated Tornadoes)
KS....MO....NE OK....N AR....TN....N MS....N AL....N GA....N SC....W NC....W VA
WV....S OH....E KY

Some Thunderstorms May APPROACH Severe Limits
FL Peninsula....Coastal GA, SC, NC

Some Thunderstorms May APPROACH Severe Limits
W ON

Some Thunderstorms May APPROACH Severe Limits
S QC....N NY....N VT....N NH....ME....NB

HEAVY RAINFALL OUTLOOK
(potential for an inch or more total rainfall within the next 24 hours)

Isolated Locations In
E WA....E OR....ID....W MT....S BC
(QPF 1 - 2")

Scattered Locations In
KS....MO....NE OK....N AR....TN....N MS....N AL....N GA....N SC....W NC....W VA
WV....S OH....E KY
(QPF 1 - 5")

Isolated Locations In
FL Peninsula....Coastal GA, SC, NC
(QPF 1 - 2")

Isolated Locations In
W ON
(QPF 1 - 2")

Isolated Locations In
S QC....N NY....N VT....N NH....ME....NB
(QPF 1 - 2")

EXCESSIVE HEAT OUTLOOK
(potential for maximum temperature to exceed 95 deg F within the next 24 hours)

Scattered Locations In
S CA....S NV....AZ....UT....C, S WY....NE Panhandle....W KS....CO....NM....TX....LA
S AR

SHORT RANGE OUTLOOK
(Through The Next 72 Hours)

More Severe Weather Concerns For The Upper Midwest, Great Lakes

As it turns out, severe weather season has a long way to go. The repetitive pattern of strong shortwaves in the polar westerlies riding over a hot and dry Sonoran heat ridge and a tropical moisture inflow shows no signs of abating. There are indications that the convective belt will shift north, as is customary in June. But with several impulses visible on MTSAT and GOES WEST imagery, the risk of supercells with tornadoes and damaging hail (along with flooding rain) will be just as horrific as what has been noted further south during the spring.

While intense thunderstorms are probable at various points around the U.S. and Canada on Sunday, the system progressing through the Upper Midwest into the Great Lakes on Monday and Tuesday is the "real beast". Tapping into a very moist, unstable flow of air from the Gulf of Mexico as well as creating excellent triple point convergence about its surface reflection, the incoming feature will present both the threat for discreet supercells as well as a derecho formation (which can be seen in the 700MB UVV panel shown here) that may affect much of Lower MI....N OH....ON Peninsula....W NY....W PA. Events such as these are capable of generating strong linear wind bursts, in addition to hail and twisters.

Extreme Heat Builds Over South Central U.S.

The Sonoran heat ridge has become a major player in sensible weather for the southern half of the nation, with occasional entries to the north, west and east. During the next 72 hours the axis of cT and mT values will tend to expand into California and then to the Southeast. The worst effects of the anticyclone will be in the lower Great Plains. There, in a belt from KS to TX, readings in excess of 100 deg F will be increasingly common in the near term, and in the days ahead.

Pacific Northwest Faces More Storms, Cool Intrusions From Gulf of Alaska

The series of disturbances moving across the northern Pacific Ocean is forecast to continue to target the northern tier of the U.S., beginning with WA and OR before continuing on toward the Upper Midwest and Northeast. While the convective output of these impulses will not be as impressive in the Columbia and Willamette Valleys, showers and thunderstorms can be expected through the next two weeks in the northwestern states and BC, with cool or cold temperatures influenced by elevation.

MEDIUM RANGE OUTLOOK
(Four To Ten Days From Now)

Tropical Storm Arthur Over The Northwestern Caribbean Sea

A weak Tropical Storm Arthur formed just east of Belize this afternoon, the first named storm of the tropical cyclone season (which actually begins on Sunday). Arthur is mainly a concern due to heavy rains. As the circulation progresses across the Yucatan Peninsula into the Bay of Campeche and Gulf of Mexico, a steady stream of deep moisture from the equatorial regions will sit and spin over southern Mexico and much of Central America. Arthur may present a problem for energy interests and then the Gulf Coast during the medium range. As the Sonoran heat ridge shifts westward and a weakness opens up over the Deep South, Arthur could reform and then get stuck along the coastline between New Orleans LA and Panama City FL. Water temperatures along the probable track of the disturbance are favorable for warm-core cyclogenesis as near as 250 miles from the Interstate 10 corridor. And with weak steering currents in play, the possibility of an extended heavy rain and severe thunderstorms event somewhere in the Cotton Belt remains viable.

Searing Heat For Southern Half Of Nation, But....

Even with the subtropical high shifting westward, the presence of a resurgent Bermuda High will likely allow a warming trend over the eastern half of the nation, below the Interstate 80 corridor. By Day 10, the heat ridge may actually take the "Great Smokies" position before breaking down ahead of a new and powerful disturbance from the western states.

....Another Storm, Cold Intrusion Appears Over The Pacific Northwest

The potential for an unusually cold surge of air from the Gulf of Alaska (beneath a blocking ridge in northwestern Canada) has been well advertised in the longer range numerical models, and looks to verify during the medium range. Temperatures in the Pacific Northwest and (later) over the northern Great Plains may reach record lows during the 6-10 day time frame. Another complication of the cPk intrusion will be another severe weather outbreak in much of the Great Plains, Midwest and finally the Northeast between June 8 and 10.

EXTENDED PERIOD FORECAST
(Between Day 11 And Day 15)

Short-Lived Hot Spell In Corn Belt, Mid-Atlantic Regions....
While the Bermuda High will be present for perhaps four days (June 8 - 11), the strong shortwave moving into the Pacific Northwest will suppress the anticyclone in the extended period. The 90 deg F isotherm may climb as far north as an Interstate 90 arc (Chicago IL to Boston MA) on June 9 and 10, only to vanish behind powerful thunderstorms and a cooling breeze out of Canada.

....While Searing Heat Tightens Its Grip Over Intermountain Region, Great Plains
The cycle of reformation will take the vast network of ridging across the southern states back toward the Sonoran position in the 11-15 day time frame. This alignment implies that the hottest temperatures during the middle of June will be found from California to the lower Mississippi Valley. Keep in mind that a high pressure area in this position will cut down on precipitation potential over the southwest and south central U.S., while stimulating the potential for severe weather from the Upper Midwest into Appalachia.

Prepared by Meteorologist LARRY COSGROVE on
Saturday, May 31, 2008 at 6:35 P.M. CT

Disclaimer:

The previous statements are my opinions only, and should not be construed as definitive fact. Links provided on this newsletter are not affiliated with WEATHERAmerica and the publisher is not responsible for content posted or associated with those sites.

Copyright 2008 by Larry Cosgrove

All rights reserved.

This publication may not be reproduced or redistributed in whole or in part without the expressed written consent of the author.

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