Severe Weather Threat Day 1 Tue Dec 11

Synopsis...

A Progressive Shortwave Trough...Currently Located Off The British
Columbia Coast Per Water Vapor Imagery...Is Expected To Dig Ssewd
Reaching Inland Portions Of The Pacific Nw And Nrn Ca During The
Latter Half Of This Forecast Period. This Process Will Result In Downstream Height Rises And Zonal Flow Into The Plains.

Meanwhile... Swly Mid-Upper Level Winds Will Persist From The Gulf Of Mexico To The Ern Seaboard Today...As A Trough Shifts Ewd From The Plains To The Great Lakes/Oh Valley And Into E Tx/La By 12z Wed.

The Primary Area Expected To Have Sufficient Moisture/Instability
For Deep Convection/Tstm Threat Is Across Much Of The Fl Peninsula.

Central And Parts Of South Fl Peninsula...

A Srn Stream Midlevel Impulse...Currently Observed Moving Enewd
Across The Wrn Gulf Of Mexico /255 E Bro/ Per Satellite Imagery...Is
Forecast To Track Across The Central Fl Peninsula Between 15-20z.

Forcing For Ascent With This Midlevel Feature And Convergence Invof
Several Boundaries Today -

1. Convective Boundary Draped Ne-Sw Across Central Fl And
2. Sea And Lake Breezes - Will Likely Support Tstm Development By Mid-Late Morning And Persist Through The Afternoon.

Activity Attendant To The Gulf Of Mexico Impulse May Be Ongoing By The Start Of Day 1 And Move Inland Later In The Morning.

A Very Moist Air Mass Resides Across The Fl Peninsula With 00z Raobs Indicating Precipitable Water Values Aob 1.75 Inches. Swly Flow Will Maintain This Moisture Feed...Especially Across Central Fl.

Although Midlevel Lapse Rates Will Be Weak...The Rich Moisture And Surface Heating Will Contribute To Mucape Up To 1500-2000 J/Kg. Midlevel Swly Winds At 35-40 Kt Will Result In Deep Layer Shear Sufficient For Storm Organization And A Few Supercells Possible.

Damaging Wind Gusts Appear To Be The Greatest Threat...As Veered Low Level Winds In The Central Peninsula And Weak Low Level Winds In S Fl Will TendTo Limit The Tornado Threat.

Cloudiness Over S Fl During The First Part Of Today Will Be Remnant
From Tstms Ongoing Across This Region At This Time. This May Inhibit Sufficient Destabilization For Afternoon Tstm Formation Along A
Residual Outflow Boundary Left Over From Pre-Day 1 Activity.

If Greater Instability Develops Than Currently Forecast...Then The Rest Of S Fl May Need To Be Included In The Slight Risk Area.

However...At This Time...This Outlook Will Include 5 Percent Probability For Strong Wind Gusts S Of The Slight Risk.


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