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    Day 2 Outlook >
Jun 21, 2024 2000 UTC Day 1 Convective Outlook
Updated: Fri Jun 21 19:59:29 UTC 2024 (Print Version | 20240621 2000Z Day 1 shapefile | 20240621 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
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 Forecast Discussion
   SPC AC 211959

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0259 PM CDT Fri Jun 21 2024

   Valid 212000Z - 221200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE NORTHERN
   HIGH PLAINS TO THE UPPER MISSISSIPPI VALLEY...THE FOUR CORNERS
   REGION...AND SOUTHERN NEW ENGLAND...

   ...SUMMARY...
   Scattered strong to severe storms are expected from parts the upper
   Mississippi Valley into the northern High Plains, and into the Four
   Corners vicinity. A few strong storms may occur from parts of the
   Lower Great Lakes to southern New England.

   ...Discussion...
   Only two notable changes were made to the previous convective
   outlook.  Otherwise the previous forecast thinking remains on track.

   1) Have increased severe-wind probabilities to 15 percent and a
   categorical Slight Risk over southern portions of New England. 
   Despite modest deep-layer westerly flow, steep 0-3 km lapse rates
   (7.5 to 8.5 deg C/km) and around 2 inches PW have yielded an
   environment that will favor multicells sporadically capable of
   strong to locally severe gusts (50-65 mph) and wind damage.  A
   linear cluster near the NY/MA/CT border will likely push eastward
   over the next 2-4 hours and reach the CT/RI coast, and this area has
   been highlighted with recently issued Severe Thunderstorm Watch
   #444.

   2) Included southwest NE in Slight-Risk equivalent severe wind
   probabilities based on the latest satellite/observational trends. 
   Storms that potentially develop over the next few hours within
   southwest NE may yield a severe-wind hazard given the steep lapse
   rate environment.

   ..Smith.. 06/21/2024

   .PREV DISCUSSION... /ISSUED 1052 AM CDT Fri Jun 21 2024/

   ...Four Corners into WY...
   Water vapor imagery shows a well-defined upper trough over NV, with
   an associated 40+kt mid-level speed max tracking from northern AZ
   into UT/CO.  Beneath this strengthening wind field and large-scale
   ascent, considerable low-level moisture is present today with
   dewpoints in the 50s across much eastern UT/western CO and southwest
   WY.  Pockets of strong daytime heating will lead to scattered
   afternoon thunderstorms.  Vertical shear profiles will promote
   supercell storm structures capable of hail and damaging winds for
   several hours this afternoon and evening.

   ...MT/WY...
   Several weak shortwave troughs are noted this morning moving
   east-northeastward across the northern Rockies.  These features,
   combined with persistent easterly low-level winds across
   central/eastern MT will result in scattered afternoon thunderstorm
   development.  Relatively isolated supercells are expected over MT,
   with more convective coverage farther south into eastern WY and
   western SD/NE.  Storms will be capable of large hail and damaging
   winds, along with the possibility of a tornado or two (mainly over
   parts of MT).  

   ...Central Plains...
   A well-defined surface boundary extends across northern NE into
   southern MN.  Considerable heating to the south of this boundary,
   along with strengthening southerly low-level winds/convergence by
   late afternoon, will result in scattered thunderstorms in vicinity
   of the front.  Sufficient flow aloft and ample CAPE will promote a
   risk of a few severe storms capable of damaging winds and hail.

   ...Lower MI...
   Pockets of strong heating will lead to scattered afternoon
   thunderstorms over parts of central and southern Lower MI.  This
   area is along the southern fringe of stronger westerlies, with 25-30
   knots of flow at 500mb.  This might be sufficient for a few strong
   storms capable of gusty winds and hail.

   ...NY/PA/Southern New England...
   Hot and humid conditions are expected today across much of PA/NY and
   southern New England, with dewpoints in the 70s and temperatures
   well into the 80s and 90s.  Mid level lapse rates are rather weak,
   so MLCAPE values will be <2000 J/kg.  Given relatively weak winds
   aloft, thunderstorm organization is expected to be marginal. 
   Nevertheless, a few strong storms capable of locally gusty/damaging
   winds are possible through the afternoon.  Please refer to MCD #1352
   for further details.

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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z

        
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