Weather Southern AL Outlook Sep 24 Afternoon

Area Forecast Discussion
National Weather Service Mobile Al
312 Pm Cdt Fri Sep 24 2010

Short Term (Tonight Through Monday Night)...A Clipper System Moves
Across Eastern Canada On Saturday And Brings A Trailing Cold
Front...Currently Pushing Southeastward Across Arkansas...Into The
Central Gulf Coast States Tonight. A Series Of Modest Shortwaves
Continues To Advance Northward Across The North Central Gulf And
Into The Area And Interacting With The Sea Breeze To Produce Mainly
Isolated Convection. Will Have Slight Chance Pops Across The Area
This Evening For Lingering Convection From The Sea Breeze...With
Small Pops Continuing Well Inland For Isolated Convection Along The
Front As It Nears The Forecast Area And Dry Over The Remainder Of
The Area As The Land Breeze Sets Up.

A Powerful Shortwave Associated With A 130+ 300 Mb Jet Dives Into The Northern Plains Meanwhile And Evolves Into A Cut Off Low Over The Eastern Plains By Saturday Night. A Strong Upper High Over The Western Atlantic Meanwhile Shifts Into The Central Atlantic With A Developing Deep Layer Southerly Flow Allowing For Deep Gulf Moisture With Precipitable Water Values Near 2 Inches To Advance Into The Coastal Counties Saturday Afternoon Tapering To Near 1.6 Inches Well Inland.

An Initially Weak Surface Wave Develops On The Frontal
Boundary Over The Central Mississippi/Alabama Border Saturday
Afternoon...Then Deepens Somewhat Through Sunday. Have Continued With Good Chance Pops For The Coastal Areas On Saturday Where The Sea Breeze And Best Deep Layer Moisture Will Be Present Tapering To Chance Pops Further Inland Where The Surface Wave Begins To Develop On The Frontal Boundary. Pops Saturday Night Are A Bit Tricky Depending On How Quickly The Surface Wave Strengthens But Have Decided To Go With Chance Pops Overall Considering That A Series Of Modest Shortwaves In The Southwesterly Flow Aloft Continue To Move Across The Area.

There Is Fair Agreement Among The Gfs And Ecmwf On
The Cut Off Low Moving To Near The Missouri Boot Heel Area By Sunday Night While The Surface Low Moves Eastward Into Central/Eastern Alabama With The Attendant Cold Front Moving About Two Thirds Through The Forecast Area. Sunday Continues To Look To Be The Best Chance For Rain For The Region As Precipitable Water Values Will Be Near 2 Inches Across Much Of The Area...And A Combination Of The Slow Moving Frontal Boundary And The Continuing Series Of Shortwaves Producing Scattered Convective Development...With Aggregate Coverage Supporting Low End Likely Pops For Much Of The Area On Sunday.

Will Have Pops Decreasing Westward Over The Area Sunday
Night As The Front And Drier Air Moves Through Much Of The Area.
There Is Fair Agreement Among The Gfs/Ecmwf On The Movement Of The Upper Low Monday Into Monday Night Generally Towards The Eastern Great Lakes With The Surface Low Lifting Quickly Off To The
Northeast And The Cold Front Continuing Eastward To Near The East
Coast. The Front Moves Slowly Through The Remainder Of The Area On Monday And Will Have Chance Pops Tapering Westward To Slight
Chance...Then Mostly Dry Monday Night Except For Small Pops Over The Eastern Most Counties.

The Risk For Severe Weather Through The Period Continues To Be Low As Instability Remains Generally Marginal
In A Moist Environment...With Capes 600-1000 J/Kg And Shear Remains
Low With 0-1 Km Helicities Mostly Below 50 M2/S2. Temperatures Will
Continue To Be About 6 Degrees Above Seasonable Levels On Saturday Then Trending To Near Seasonable Levels By Monday.

Long Term (Tuesday Through Friday)...Expect The Upper Low To Eject
Off To The Northeast With A Remaining Upper Trof Pattern Over The
Eastern States Which Then Weakens Through Wednesday. Initially
Cooler...Actually Seasonable...Temperatures On Tuesday Are Followed
By A Return To Above Seasonable Temperatures For The Remainder Of
The Long Term Period. Dry Weather Continues Through Wednesday
Night. Will Keep Small Pops For Thursday And Friday Although If A
Low Pressure System Develops As Advertised By The Gfs/Ecmwf And
Passes East Of The Area...Then The Area Will Remain Dry.

Aviation (18z Issuance)...Scattered Showers And Thunderstorms This
Afternoon Expected To Taper Off By About 9 Pm. Confidence On
Coverage And Location High Enough To Include Tempos In The Taf At
This Time And This Should Be Representative Of The Area. Cu Bases
Around 3-5 Kft Becoming 1-2 Kft In Convection. Vsby Near Zero In
Tsra With Heavy Rain.

Marine...A High Over Westlant Ridging Into The Area Will Retreat
Ahead Of An Approaching Front In The Ozarks. The Front Will Shudder
To A Stop North Of The Coast On Saturday Before Getting Underway
Again And Moving East Of The Marine Area By Monday. Southerly Flow
Ahead Of The Front Late In The Weekend Will Shift To The North
Behind It On Monday. Developed Seas 3 To 5 Feet At Times Even 6 Feet
Since Winds Later In The Period Are Reaching 15 To 20 Knots.

Fire Weather...No Concerns As Afternoon Relative Humidities Will
Remain Above Critical Levels As Deep Layer Moisture Increases Over
The Region Along With An Increasing Chance Of Showers And
Thunderstorms Through The Weekend.

Preliminary Point Temps/Pops...
Mobile 71 91 70 88 / 20 50 30 70
Pensacola 73 90 72 87 / 20 50 40 70
Destin 75 88 74 85 / 20 50 40 70
Evergreen 67 91 68 88 / 20 50 40 70
Waynesboro 66 89 66 85 / 20 40 40 70
Camden 67 92 67 86 / 20 40 50 70
Crestview 68 91 69 89 / 20 50 40 70

Mob Watches/Warnings/Advisories...

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