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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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James Spann should be back Monday morning with the next edition of the Weather Xtreme Video. Check back with the Blog frequently for the latest updates on the ever changing and somewhat challenging weather for Central Aalbama. Godspeed.