Archive for June, 2013
Storms are fairly concentrated in two places tonight, including Morgan County in North Alabama and Greene and Hale Counties in West Central Alabama.
Showers have weakened over Walker County.
The storms over Morgan County are near the vortex of the upper level disturbance that has triggered the showers today. It is moving to the northeast.
The showers and storms will continue to go downhill and should be gone in the next couple of hours.
Isolated showers are forming across western Alabama this afternoon ahead of a southeastward diving upper disturbance that is near Memphis at this hour. They extend northward along a curved line into Central Tennessee west of Nashville.
The heaviest shower was just northeast of Jasper in Walker County, moving east toward Arkadelphia. No lightning yet, but it probably isn’t far away.
Showers are increasing quickly over Pickens County, extending into northwestern Tuscaloosa County. The main cells are north of Aliceville, northeast of Carrollton and between Gordo and Reform. Movement is toward the east. Will probably see lightning and thunder in the Tuscaloosa area within the hour.
Showers will continue to develop and some of them will grow into storms as we go through the afternoon hours. They may linger a little linger than usual this evening thanks to the parent disturbance.
As we sail into afternoon here in Central Alabama, here is a quick look at the Alabama weather situation.
Yesterday’s cold front lies across southeastern Alabama with a surface low tracking along it southwest of Atlanta. The front isn’t going to go much further to the south though. Another weak surface low was east of New Orleans, pushing to the east northeast slowly as well. The front will have a hard time making it to the coast. That’s a tough nut to crack in the summer in the South.
The front was triggering widespread showers and storms from the Northeast U.S. across eastern North Carolina and into northern Florida. Severe severe thunderstorm and flash flood warnings have been issued, including a couple in northeastern Florida. There is even a tornado warning right now west of Wilmington NC.
The upper air charts are dominated by an impressive upper level high centered near Las Vegas, with an equally impressive trough covering the east third of the nation, anchored by a big upper low near Indianapolis. We are feeling the influence of this trough and will for the next couple of days. It is responsible for the front to our southeast and the axis of drier air that has pushed southeast of I-59.
With mostly clear skies this morning north of the front, temperatures have warmed nicely into the middle 80s across the I-20/59 corridor. We are starting to see just a tad of instability behind the axis of driest air and a cumulus field was developing across North Central Alabama. Some high clouds were being blown off the thunderstorm activity to the south around I-20.
A very impressive upper level disturbance was clearly evident on water vapor satellite imagery, approaching the Memphis area, and diving southeast. It has some better moisture with it, and a very nice cumulus field has developed. This feature will starting triggering scattered showers and storms as it moves southeastward across northern Mississippi and northern Alabama later today and this evening. The chance you will see rain is still only about 20 percent though. Highs will top out in the upper 80s. Lows tonight will be in the upper 60s.
The upper trough will be a fixture for much of the week ahead, retrograding back to the west a bit by the end of the week. We stay in a broad southwesterly flow aloft from our position ahead of the trough. This means plenty of mugginess and a slightly elevated chance of mainly afternoon and evening thunderstorms each day. Rain chances will ramp up from today’s 20 percent, to around 30-40 percent Monday and Tuesday, to around 40-60 percent each day through the holiday weekend. High temperatures will be held back from normal levels just a bit, averaging in the middle 80s ealry in the week, but closer to 80F through the rest of the week and weekend.
Pretty pleasant for the first week of July, if you don’t mind a few showers.
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The main forecast challenge for today is to determine exactly where the dividing line is between the drier air that moved into Central Alabama yesterday and the more moisture rich air where showers become likely. The sounding at the Shelby County Airport from last night is certainly dry but surface dew points show the dew point boundary to be between Birmingham and Alexander City. I’m going to continue with a dry forecast for Central Alabama with showers most likely to occur generally south of Clanton across the southern half of Alabama. The main rationale for this is the continued digging of the upper trough before it begins to retrograde plus the forecasts of precipitable water.
A dense fog advisory was posted for parts of Central Alabama in a swath running east to west between Birmingham and Troy. The fog should burn off around 9 am.
As the upper trough does begin to retrograde Monday into Tuesday, the precipitable water (PW) values for Central Alabama begin to climb which puts scattered showers back into the forecast. PW values should continue to climb into mid-week which should increase showers in number and coverage. MOS guidance values for probabilities rise into the 50 to 65 percent range for Wednesday and Thursday which seems pretty reasonable. The main driving force will be diurnal heating.
July 3rd and 4th could be fairly wet with showers and thunderstorms likely with highs 86 to 89, still not bad temperatures for the early portion of July when the 30-year average high for Birmingham sits at 90 degrees.
The upper trough continues to weaken as we head into the end of the week as the upper ridge to our east, the Bermuda High, noses into the Southeast. This will keep us in fairly deep moisture as heights rise and temperatures climb back toward the 90 degree mark.
Tropics remain quiet with one area in the western Caribbean being watched. For now, however, the upper wind flow across the Caribbean is strongly out of the west, so there is not likely to be any tropical storm formation for the next several days.
Across the nation, heat is the big news for the western US. Bill made an excellent post on the records late yesterday afternoon. The ridge in the west is expected to stay in place for the foreseeable future. Even with the somewhat anomalous pattern, severe weather risk is fairly low.
The GFS continues to maintain a somewhat troughy look to the upper air pattern through about the 11th of July, but after that the upper ridge builds back into the Central Plains and Ohio Valley returning us to a more summer-ish look to the flow.
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The western United States is sizzling under a huge 594 dkm upper level high pressure system.
Lots of records fell on Friday, and even more today. Here is a representative listing of daily records for 6/29:
123F at Needles CA (June record)
122F at Palm Springs/Thermal CA
121F at Indio CA
118F at Las Vegas NWS (since establishment in 1996)
115F at Phantom Ranch AZ
115F at Las Vegas (MCarran – official station)
112F at Kingman AZ (second straight 110+ day; first time ever in June).
110F at Laredo
109F at Victoria TX (All time June high temp record).
108F at Austin – Camp Mabry. 106F on Friday was also a record.
108F at Del Rio.
108F at San Antonio. (New record for June).
107F at Houston – Intercontinental. (New record for June).
107F at Austin – Bergstrom. 105F on Friday also a record.
107F at Corpus Christi. Just shy of the 109F all time record high.
107f at Sacramento.
106F at College Station
106F at Harlingen
105F at Houston Hobby. (New record for June).
105F at Winslow AZ
105F at Longview TX (Tied record)
105F at Salt Lake City (Tied all time June record)
104F at McAllen
102F at Brownsville
102F at Lufkin TX (tied record)
102F at Reno
92F at Mountain View, CA (Home of Google!)
89F at South Lake Tahoe
Seems ridiculous, but the 73F at Crescent City CA today was also a record for the date.
And equally ridiculous, the 58F at Astoria< OR this morning was a record warm minimum.
A quick look at the surface analysis shows the frontal boundary continues to drop south across the state today. The front was roughly along the Interstate 20 corridor across the state. It will continue to head south overnight and will actually bring a bit of drier air in behind it. That should translate into less humidity and slightly more comfortable evenings and mornings for the next couple of days.
Looking at the latest satellite image, most of north Alabama is seeing mostly sunny skies that have allowed most areas to have a very nice Saturday across those portions of the state. The thicker and taller clouds associated with the thunderstorms that continue to push south is quite evident along the Interstate 85 corridor and the Interstate 65 corridor south of Montgomery. The thick, white clouds will push south out ahead of the frontal boundary.
The radar has been fairly active across portions of our southern counties this afternoon. The showers and storms that developed continue a southward progression. Nearly all the convection is along and south of Interstate 85 and U.S. 80. The one exception is a thunderstorm over northern Chambers and southern Randolph Counties. None of these storms have been severe today, but are producing gusty winds, intense rain and frequent lightning. The rest of north Alabama has seen abundant sunshine with mostly sunny skies. It should be a great looking evening as most locations will remain dry. Today looks as though it was the better day of the weekend as storms tomorrow will go from more isolated to scattered. Rain chances will increase as we head into the first week of July.