Severe Weather Threat thru May 9

Fri May 2 Convective Outlook
Storm Prediction Center Norman Ok
No Svr Tstm Areas Forecast...

Thunderstorms Will Be Possible Across Portions Of Florida...As Well
As Parts Of The Northern And Central Plains Westward Through The
Northern Rockies And Parts Of Oregon.

Severe Thunderstorms Are Not Expected.

Upper-Air Pattern Through Remainder Of Period Will Continue To
Feature Slowly Progressive...Positively Tilted Synoptic-Scale Trough
From Nrn Mex To Upper Great Lakes.

Srn Portion Will Be Shunted Ewd Across Arklatex And Central/S Tx By Embedded Shortwave Troughs Currently Over Ok...And Over Big Bend Region Of W Tx.

Srn Extension Of Troughing Should Reach Swrn Al...Sern Ms...And Nwrn Gulf By 12z.

Meanwhile...Low-Amplitude But Well-Defined Shortwave Trough --
Apparent In Moisture-Channel Imagery Invof Nd/Mn Border -- Will Move
Sewd Across Lm And Lower Mi To Lh And Swrn Ont.

At Sfc...Cold Front Extends From Atlc High Seas E Of Mid-Atlc Region ...Sswwd Across Fl Where It Temporarily Has Become Quasistationary...Then Swwd Across Central Gulf.

Front Is Expected To Undergo Net Swd Drift This Period...Before Accelerating Sewd Down Peninsula As Srn-Stream Shortwave Apchs.

Farther Nw...Reinforcement And Sewd Movement Of Sfc Anticyclone Behind Nrn-Stream Shortwave Trough Will Contribute To Frontogenesis Along Or Just Ne Of Sfc Trough Extending From Sern Bc To Neb Panhandle.

Three Areas Of Gen Tstm Potential Are Presented...Each Of Which Are
Strongly Tied To Diurnal Cycles And Should Wane Considerably After
Dusk.

Fl Peninsula...

Scattered To Widely Scattered Tstms Should Form With A Few Stg Gusts Possible...But No Organized Svr Threat.

Although Synoptic Front Will Remain Farther N While Drifting S...Zone Of Relatively Maximized Boundary-Layer Lift Will Migrate Swd Through Combination Of Outflow Effects And Development Of Diurnal Trough/Confluence Line To Its S.

Lift May Be Augmented Further S Of Front By Sea-Breeze/Outflow/Differential-Heating Boundaries.

Any Of These May Focus Tstm Initiation...Primarily From Around Noontime Through Early Evening When Buoyancy Will Be Maximized And Cinh Is Relatively Weak.

1500-2500 J/Kg Mlcape Is Possible In Most Persistently Heated Areas ...Amidst 25-35 Kt Effective Shear Magnitudes.

As Such...Main Mode Should Be Multicellular/Clustered...With Isolated Stg Downdrafts Possible.

Attm Unconditional Svr Potential Appears Too Small...Brief And Unorganized To Draw Aoa 5% Wind Or Hail Probabilities.

Nrn/Central Rockies And Adjoining High Plains...

Isolated To Widely Scattered...High-Based Tstms Are Possible Invof
Frontogenetic Corridor And Sfc Trough.

Fcst Soundings Show Inverted-V Thermodynamic Profile... Characterized By Steep Low-Level Thermal Lapse Rates And Nearly Constant Mixing-Ratio Dew Point Profiles In Deep/Well-Mixed Subcloud Layer.

However...Above That...Buoyancy Appears Mrgl With Mlcape Less Than 250 J/Kg In Most Areas. As Such...Stg Gusts Are Possible But Svr-Wind Risk Appears Too Low-Conditional For Mrgl/5% Probabilities.

Nern Ore And Vicinity...

Tstm Potential Appears Most Mrgl Here...But At Least Isolated
Development Appears Possible In Central/Nern Ore This Aftn...Moving
Enewd Across Region.

Main Limiting Factor For Greater Coverage/Intensity Will Be Lack Of Stronger Moisture...Which In Tandem With Sub-Optimal Midlevel Lapse Rates...Yields Fcst Mlcape Less Than 100 J/Kg In Most Areas.

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Sat May 3 Convective Outlook
Storm Prediction Center Norman Ok
No Svr Tstm Areas Forecast...

Thunderstorms Will Be Possible Across Parts Of Florida...The Lower
Great Lakes...And The Northern Plains Vicinity On Saturday.

Severe Weather Is Not Expected.

The Large-Scale Upper Pattern Is Progged To Trend Increasingly Zonal This Period...As A Trough Crosses The Ern U.S. And Shifts Offshore Into The Western Atlantic Leaving Behind A Much Lower-Amplitude Flow Field Upstream Across The Conus.

At The Surface...A Cold Front Lingering Over The Fl Peninsula Will
Progress Swd With Time...Clearing The Srn Reaches Of The State
Overnight As The Aforementioned Upper System Advances.

Diurnally Driven Showers And A Few Thunderstorms Will Be Possible
Across Fl Generally S Of The Front...With Other/Isolated Convection
Expected Over The Lower Great Lakes Region...And Within A
Warm-Advection Zone Progged To Set Up During The Second Half Of The Period Across The Nrn Plains Vicinity.

In All Areas...Severe Weather Is Not Expected.

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Sun May 4 Convective Outlook
Storm Prediction Center Norman Ok
No Svr Tstm Areas Forecast...

Showers And A Few Thunderstorms Will Be Possible In A Zone Extending From The Northern Intermountain Region Southeastward Across The Northern Plains And Into The Midwest.

Afternoon Showers And Isolated Thunderstorms Will Also Be Possible Across Portions Of South Florida...As Well As Portions Of Northern New England.

The Zonal Upper Flow Field Evolving Across The U.S. Will Continue
Through Day 3...With Fast/Generally Wly Flow Across The Nrn Half Of
The Country And Weaker Flow Over The Srn States.

At The Surface...A Wavy W-E Baroclinic Zone Is Progged To Sharpen
From The Rockies Ewd Across The Plains...The Oh Valley...And Into
The Mid-Atlantic Vicinity...Drifting Slowly Swd With Time -- Particularly E Of The Rockies.

Areas Of Scattered Showers And Isolated Thunderstorms Can Be
Expected From The Mt Vicinity Sewd Across The Nrn Plains And Into
The Midwest...Near And N Of The Aforementioned Cold Front.

Diurnal Convection Is Also Possible Across S Fl...As Well As Over Nrn New England As A Small Upper Low Crosses This Region -- Though In None Of These Areas Is Severe Weather Expected.

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May 5-9 Convective Outlook
Storm Prediction Center Norman Ok

An Intrusion Of Cool Continental Air Into/Across The Gulf Of Mexico
-- Ongoing Attm -- Will Greatly Limit Severe Weather Potential For
The Next Several Days.

As The Surface High Settles Into The Gulf And Then Lingers There Through At Least The First Portion Of The Forecast Period /I.E. Early Next Week/...Potential For Moisture Return Nwd Into The Central U.S. Will Be Greatly Hindered.

As A Wrn U.S. Upper Trough Evolves/Deepens Through Early Next
Week...Severe Risk Will Remain Low.

However...With High-Plains Low Pressure Evolving Ahead Of The Trough Thus Supporting Widespread Sly Low-Level Flow Into The Central Conus...Steadily Modifying Gulf Air Will Continue Being Advected Nwd Through Midweek.

By The Wed-Fri Time Period /Days 6-8/...Increasingly Widespread Moderate Cape Should Be Available Across A Large Portion Of The Central Third Of The Country...Thus Supporting An Increase In Severe Potential.

With That Being Said However...Major Model Differences Persist With
Respect To Evolution Of Wrn U.S. Upper Troughing.

While The Gfs Advances A Large Trough -- Comprised Of Phased Nrn- And Srn-Stream Systems -- Ewd Into The Plains Through The Latter Half Of The Period...The Ecmwf Depicts A Similarly-Timed Nrn Stream Trough Advance Into The Nrn Plains But A Stationary -- Or Even Retrograding -- Srn-Stream Portion Of The Trough.

With Substantial Variations Also Therefore Manifest In The Surface Pattern Across The Plains Vicinity...Temporally And Spatially Delineating Risk Areas Remains Difficult Attm.

However...As Uncertainty Diminishes With Time And Risk Areas Become More Clear...Expect Severe Weather Probability Areas To Be Introduced In Later Forecasts Across Portions Of The Plains States And Vicinity.


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