Dothan Area Weather Afternoon Discussion Dec 15

Near Term [Tonight]...

The Large Scale Longwave Pattern Is Progressive Yet Rather
Amplified, Especially In The Nrn Stream.

This Is Highlighted By Mean From Canadian Prairies To Great Basin And Shortwave Traversing Belt Of Cyclonic Flow Within This Trough. The Lead And Potent Shortwave Shearing Out With Assocd 542dm Low Over Il This Afternoon While Second Shortwave Over Nv Rounding The Base Of Trough.

East Of Initial Shortwave Is H5 Ridge With Axis From E/Cntrl Gulf To Cntrl Great Lakes. H5 High And Elongated Ridge Remain Over Gulf Of
Mex Into Sw Ga. Satellite Imagery Shows That Lead Short Wave
Beginning To Flatten Downstream Ridge, But With Minimal Impact On
Our Local Weather.

Closer To Home, A Few Weak Shortwaves Moved East Of Local Area This Late Morning With Drier Air In Its Wake This Aftn Killing Off The Earlier Very Light Rain.

At Surface, Ridge Of High Pressure From Que Down Ern Seaboard
Continues To Dominate Local Region Bringing A Ne Flow To Ern
Counties, And More Onshore Flow Elsewhere. Eroding Coastal Trough Was Noted Offshore. Low Over Ia With Trailing Cold Front To Tx Coast. Where Ne Flow Prevailed, A Weak Wedge Promoted A Stratus Cloud Deck That Kept Some Of These Clouds Into The Aftn Making Temp Forecasts A Little Tricky.

During This Evening, Lead Nrn Stream Ia Shortwave Will Continue To
Move Newd To Mi And Weaken Considerably. Second Shortwave Will Pivot Ewd Reaching Nrn Az Then 4 Corners Into Tonight.

Yet Another Shortwave Will Move Ewd Across Nrn Baja This Eve Eventually Phasing With Az Shortwave Over Tx/Ok Panhandle Around Sunrise Sun. All This Will Serve To Further Depress Downstream Ridge And Shift It Off To The East With Flow Becoming More Swly.

At Surface, Low Will Move Rapidly Newd From Ia To Mn Around Sundown Then Into Nrn Wi Overnight With Trailing Cold Front Moving Slowly Sewd Becoming Quasi-Stnry From Oh Valley To E Tx.

Sw Portion May Even Drift Nwd Initially In Response To Upstream Development Aloft. Rapid Movement Of This Front Will Not Begin Until Later On Sunday When Phasing Shortwave Acts To Push It Ese. This Will Kick Ern Ridge Into Atlc.

Main Concern Overnight Is Fog.

Increasing Sw Flow Aloft And Se Flow Below Will Increase Local Moisture Leading To Small Dew Point Depressions. Veering Flow Will Lead To Warmer Temps. So...Local Fog Guidance Shows Very Good Chance Vsbys At Or Below One Mile Especially West Of Apalachicola River. Will Put Areas Of Dense Fog West Of River... Patchy Dense East Of River. Lows In The Mid To Upper 50s.

Short Term [Sunday Through Tuesday]...

The Vigorous Shortwaves Will Continue To Translates Ewd Across The Plains And Great Lakes Region Within The 500 Mb Flow. This Will Lead To The Development Of A Progressive Longwave Trough Over The N/Cntrl Plains On Monday And Into Ern States On Tues With Increasing Deep Layer Gulf Return Flow And Upper Divergence.

Lead Shortwave Will Approach Local Region Sun Aftn. Meanwhile Upstream Shortwaves, Will Generate Cyclogenesis Over Ok Panhandle Sun Morning With Low Advancing Newd To Oh River Valley On Monday Then Great Lakes Mon Night And Drag Cold Front Ese Across Our Area.

Initially Mid-Upper Flow Will Be Parallel To The Cold Front...Thus
Slowing Out Down But This Soon Changes And Front To Approach Our Area Early Mon With Assocd Moisture (Moderate Isentropic Lift)
Beginning To Impact Local Area Sun, Especially Nw Zones.

Pwats Will Have Increased At 00z Mon To 1.57 At Dhn And 1.25 Inches At Ktlh. Strong Sw Flow Ahead Of Front/Trough Will Likely Eliminate Chances Of Any Fog/Stratus Mon Morning.

In Wake Of Front, Drier Air On Nw To N Flow Will Advect Into The Region As Surface High Pressure Builds Into Nrn Gulf With Clearing Skies Expected Mon Night Or Early Tues From Nw-Se.

Pop Will Begin To Increase Sunday Afternoon Across Our Northwest
Zones (40-50% Nw Third) Down To Near Zero Se Big Bend. This Clearly Noted On Local Wrf. We Have Seen An End (For Now) To The Chilly Daytime Temperatures Of The Past Few Days, As We Expect Highs In The Lower To Mid 70s And Lows In The 50s.

60-20% Nw-Se Pop Gradient Sunday Night, 70-40% Mon And 20-40% Mon Night.

The Gfs, Nam, And Ecmwf All Forecast A Substantial Weakening
Trend Of The Convective Band (Qpf & Omega Fields) As It Moves Into
Our Forecast Area.

Local Confidence Tool With 5-7% Chance Of Severe Wx On Mon Mainly Wrn Most Counties.

Certainly At 18z Mon At Dhn, The Expected Mid Tropospheric Wind Speeds Near 70 Kt Is Impressive. Also, Forecast 03km Helicity Of 160 M/S, And 700-500 Mb Lapse Rates Around 6 C/Km Is Noteworthy.

However Ml Cape, Sb Cape, Li Of -2 Less Impressive So Low Cape But High Shear Environment Favored.

So With All The Nwp Guidance Forecasting A Weakening Trend Like This, It Appears Unlikely That We Will Get Widespread Severe Storms. The Main Threat From Any Severe Storms That Do Develop Would Be Marginally Damaging Straight Line Wind Gusts And/Or Hail And Mainly Wrn Most Counties.

Long Term [Tuesday Night Through Saturday]...

With, The Surface Ridge Behind Mondays Front Being More Pacific In
Origin, Much Cooler Weather Is Not Anticipated. In Fact Temperatures
Behind This Front Should Only Drop Back To Climatological Norms For Mid December.

The Fast Pattern Continues To Keep A System Moving Into The Region Every Couple Of Days With The Next System Expected Late Thursday Into Friday.

This System In Both The 15/00z Gfs And Euro Appear Quite Energetic With A Strong Wind Field Providing Plenty Of Shear.

The Fast-Paced Pattern However Will Limit The Period Of Return
Flow From The Gulf And Thus Only Limited Instability Is Anticipated
At This Present Time (As Is Typical For December/January Storm
Systems).

Will Still Show Thunderstorms In The Forecast But Only Time Will Tell If This System Will Present A Substantive Severe Threat. The Trend Thus Far This Fall/Winter Season Would Indicate That The Potential Would Be Quite Low.

Behind The Frontal Boundary, Guidance Indicates That A Much Colder
Airmass Will Be Incoming As Strong Northwesterly Flow Is Expected
Behind This System Bringing An Airmass From Central Canada (As
Opposed From The Pacific - Like The Monday Night Frontal Passage).

The Gfs-Based Statistical Guidance Seems Too Warm Here So Have
Adjusted The Forecast Values Down A Couple Of Categories With A
Light Freeze Appearing Possible On Saturday Morning.

Marine...

Winds Will Veer From East Later Today, To South On Sunday As A Cold Front Approaches From The Northwest.

Expect Scec Conds Wrn Leg Mon Aftn, With Borderline Advisory Conds Wrn Leg And Scec Conds Ern Leg Mon Night, Scec Conds Possible Ern Leg Tues Morning.

Aviation...[Through 18z Sunday]

Sunshine Is Helping To Scatter Out Conditions To Vfr At Most Sites This Afternoon. Only Kaby Remains Under A Mvfr Cloud Deck Which Will Likely Persist The Rest Of The Day.

Increasing Moisture Will Generate Widespread Ifr Conditions After Midnight Dropping To Lifr For Extended Periods Around Sunrise
Tomorrow Morning At Most Aerodromes.

Fire Weather...

Relative Humidity Is Expected To Remain Above Critical Levels
Through At Least Wednesday.

Hydrology...

Some Of The Local Rivers Have Risen Rather Sharply Over The Past Few Days In Response To The Widespread, Beneficial Rainfall From A Few Days Ago.

However, These Rivers Were Well Below Action Stage, So No Significant Impacts Are Expected.

Preliminary Point Temps/Pops...

Tallahassee 56 73 61 75 51 / 10 20 30 60 30
Panama City 60 72 64 73 54 / 10 30 30 50 30
Dothan 54 70 61 73 47 / 10 50 50 70 20
Albany 54 71 60 73 49 / 10 30 50 60 30
Valdosta 57 75 59 75 52 / 10 10 30 60 40
Cross City 57 76 57 76 55 / 10 10 10 40 40
Apalachicola 59 71 64 73 58 / 10 20 20 50 30

Tae Watches/Warnings/Advisories...

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


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