Dothan Area Weather Discussion Dec 16

Near Term [Rest Of Today Into Tonight]...

The Large Scale Longwave Pattern Remains Relatively Amplified Yet
Progressive. This Is Highlighted By Ridging Over Wrn States, Broad
Trough Ewd To Ern Seaboard And H5 Ridge Ridge Now Shunted Offshore Into Wrn Atlc. Within The Troughing Centered From Rockies Across Great Plains, A Series Of Shortwaves Will Continue To Translate Rapidly Ewd Shifting Trough Ewd And Serve As Focus Of Weather.

Each Of These Shortwaves Will Eject Newd And Weaken As They Try To Phase Together To Sharpen Trough. One Shortwave Is Progged To Reach Cntrl Il, Another To Wrn Tn, Another To Srn High Plains By Sundown And Yet Another That Races Newd Over Al And Begins To Interact With The Frontal System And Deep Layer Moisture. High Clouds Ahead Of Trough/Shortwave Streaming Across Gulf Region.

At The Surface, Low Over Great Lakes With Trailing Cold Front Ssw
To Low Near Memphis Then Quasi-Stnry Across Ar And Se Tx With A Line Of Showers And Thunderstorms Within Area Of H85 Convergence From Ern Tn Swwd Into Sern Tx. Marine Warm Front Observed From Se Tx Ene Across Al/Fl Panhandle. This Cold Front Has Shunted High Pressure Center Into The Extreme Wrn Atlc With Veering Winds And Higher Dew Points That Allowed Dense Fog This Morning To Linger Areawide.

Tonight, The Trough Will Weaken, Still The Combination Of A Strong
Sub-Tropical Jet S/E Of Upper Trough Combined With Passing
Shortwaves Embedded In Jet Will Reamplify Trough Providing Stronger Lift Into Lwr Ms Valley With Increasing Onshore Gulf Flow
Overspreading Ewd And Eroding Local High.

All This Should Bring An Increase In Shallow Isentropic Induced Showers And Possibly A Few Tstms Will Begin Over The Gulf Assocd With Lifting Warm Front And Move Inland Ahead Of A Larger Area Of More Widespread Convection Moving In From The Nw Assocd With Approaching Trough/Shortwave/Cold Front.

Will Go With 60-0% Nw-Se Pop Gradient. All Vsby Guidance Imply Areas Of A Dense And Locally Widespread Fog Mix Of Radiation And Advection Fog. This Reflected In Grids And A Dense Fog Advisory May Be Needed Tonight.

Short Term [Monday Through Wednesday]...

The Progressive Longwave Trough Will Continue Across Ern States And Amplify Further On Monday As A Series Of Impulses/Vort Max Moving Newd Across Oh Valley And Se States With Its Attendant Height Falls.This Will Develop Cyclogenesis Early With Low Lifting Newd Across Oh Valley Then Pa And Into Ne States With Trailing Cold Front Initially Moving Slowly Then Racing Across Ne Gulf Region During The Aftn And Eve As A Series Of Shortwaves Race Newd Over Ern Conus.

The Pop Will Increase Monday To About 70% At Dothan & Albany, 60% At Tallahassee, And Only 40% At Cross City.

The Storm Prediction Center Has Outlooked Al/Ga Portions Of Our
Forecast Area In A "Slight Risk" (15% Probability Of A Severe Storm
Within 25 Miles Of A Point, 5% For The Rest Of Our Area).

Strong Mid Tropospheric Winds Of 60-70 Kt And A Marginally Unstable Airmass (Sbcape Around 500 J/Kg) And Increasing Dew Points In The Pre-Frontal Warm Sector Favor At Least Some Storm Organization.

However, Models, Especially Nam And Ecmwf Suggest A Gradual Decrease In Coverage And Intensity Of Convective Band Ahead Of Cold Front As It Moves Ewd And The Stronger Forcing Moves Towards Oh Valley. Amount Of Cloud Cover Could Be A Determinative Factor In Instability.

The Lack Of Phasing Among The Multiple Short Waves Creating A
Marginal Thermodynamic Environment That Seems To Be Preventing This Setup From Being A More Significant Event For Our Area, As The Main 500 Mb Short Wave Will Be Up In The Ohio Valley As It Goes
Negatively Tilted Monday Afternoon.

Additionally, The Forecast 850 Mb Jet Is Not Forecast To Be That Impressive For This Time Of Year (Only 40-45 Kt), And Its Core Will Be Just North Of Our Forecast Area. The Fairly Unidirectional, Deep Southwest Wind Field And Unimpressive 0-1 Km Shear Magnitudes Suggest That Our Main Severe Threat Will Be Isolated Damaging Straight Line Wind Gusts In Isolated Bowing Segments Along The Convective Bands, Similar To What We Observed Last Week With The Frontal System Just To Our North.

The Tornado Threat Appears Low, And Would Be Limited To Brief,
Relatively Weak "Spin-Ups" At The Ends Of Stronger Bowing Segments.

Beginning Mon Night, Flow Aloft Quickly Becomes Zonal As Trough
Exits Into Atlc. In Wake Of Front, Surface High Builds Into The Central Gulf On Tues Then Moves Rapidly Ewd Tues Night To Reach Coast On Wed Ahead Of Next System. Rain Chances Will Diminish
Monday Night (20-30%) As The Cold Front Exits.

Long Term [Wednesday Night Through Saturday]...

Model Guidance Continues To Have Difficulty Resolving Various Long
Term Forecast Issues During The Latter Portion Of The Period As
Would Be Expected In Such A Fast Moving Pattern Across The Conus.

The Period Begins With High Pressure Across The Region Quickly
Sliding Eastward And A Strong Frontal System Approaching Wednesday Night.

The Models Are Actually In Decent Agreement Here With Respect
To Timing. It Looks Like Another Cold Front Will Surge Through The
Region On Thursday Bringing A Good Chance For Showers And
Thunderstorms.

Kinematic Fields Are Strong Out Ahead Of The System But Instability Will Once Again Be In Doubt Given The Limited Period Of Return Flow Ahead Of The System. The 16/00z Gfs And Euro Do Generate Some Non-Zero Areas Of Surface-Based Instability Ahead Of The Frontal Boundary So The Severe Weather Potential - While Still Uncertain - Cannot Be Ruled Out Yet.

Beyond Thursday, The Forecast Continues To Be Highly Variable. While Cooler And Drier Air Will Move In Behind The Front, How Cold It Gets And For How Long Continues To Change With Each Model Cycle. This Batch Of Guidance Keeps The Bulk Of The Cold Air Wrapped Up To The North Closer To The Core Of The Mid Level Trough Across The Eastern Seaboard And With The Fast Moving Pattern, Shifts A Ridge Across The Central Conus Eastward By Saturday, Resulting In A Quick Moderating Trend To Temperatures. Given The Current Pattern And The Lack Of Any Strong Signals Favoring A Significant Cold Intrusion Into The South, Will Trend The Forecast Warmer At The End Of The Long Term Period.

Needless To Say Beyond Thursday, The Long Term Forecast Is Much
Lower Confidence Than Usual Given All The Run To Run Model
Variability.

Aviation...

Conditions Remain Unsettled With Mostly Mvfr Holding At Western
Terminals With Deteriorating Conditions Expected At All Sites This
Evening.

Fog Will Be The Main Contributor To Reduced Visibilities Tonight With Kdhn Seeing Reduced Visibilities The Earliest.

All Sites Are Expected To Drop Down To Lifr For At Least A Short Period Tonight.

Although Visibilities Should Increase Around Mid Morning... Showers And Thunderstorms Will Be Moving In From West To East Late Tonight And Tomorrow Which Will Maintain Mvfr And Brief Ifr Restrictions Monday.

Marine...

Winds Will Veer And Gradually Increase Somewhat Into Tonight Ahead
Of An Approaching Cold Front.

Expect Sea Fog To Develop Nearshore Especially Ern Most Waters.

All Of The Nwp Guidance Has Backed Off A Bit On Their Wind Speed Forecasts Near And Behind The Cold Front, And Headline Conditions Appear Unlikely Monday Night Thru Wednesday.

In The Wake Of The Front, Winds And Seas Will Rapidly Increase To Scec Levels Wed Night Into Thurs Then To Advisory Levels Thurs Into Fri.

Fire Wx...

Conditions Will Remain Too Moist For Fire Weather Concerns Through Mid Week With A Good Chance Of Wetting Rains Across The Area.

Hydrology...

Area Rivers Continue Well Below Action Stage, And This Will Likely
Continue This Week With Storm Total Qpf Values Being Mostly Under An Inch With Mondays Cold Front.

Preliminary Point Temps/Pops...

Tallahassee 63 74 54 73 40 / 30 60 30 10 10
Panama City 64 72 60 71 50 / 40 60 20 0 10
Dothan 62 72 52 69 42 / 50 70 20 0 10
Albany 61 73 54 69 40 / 50 70 20 0 10
Valdosta 61 74 57 71 41 / 30 60 30 10 10
Cross City 60 75 60 73 40 / 10 40 30 10 10
Apalachicola 65 73 61 71 52 / 20 50 30 10 10

Tae Watches/Warnings/Advisories...

Fl...None.
Ga...None.
Al...None.
Gm...None.


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