SPC AC 100550

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1250 AM CDT Sat Oct 10 2020

   Valid 111200Z - 121200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE NORTHERN/CENTRAL PLAINS INTO THE UPPER MIDWEST...

   ...SUMMARY...
   Isolated strong to severe thunderstorms may occur Sunday across
   parts of the northern/central Plains into the Upper Midwest, with
   marginally severe thunderstorms also possible across parts of the
   Southeast.

   ...Northern/Central Plains into the Upper Midwest...
   A large-scale upper trough over western Canada and the northern
   Rockies will move eastward Sunday into central Canada, the
   northern/central Plains, and Upper Midwest. This upper trough should
   acquire a negative tilt by Sunday evening, while strong low to
   mid-level south-southwesterly winds overspread these regions. At the
   surface, a cold front will sweep eastward across the Dakotas and NE
   Sunday afternoon/evening, and continue into the Upper Midwest Sunday
   night. An EML will likely suppress convective development along the
   front through much of the day until it encounters mid 50s to perhaps
   lower 60s surface dewpoints late Sunday afternoon across far eastern
   SD, southwestern MN, and vicinity. The steep mid-level lapse rates
   present with the EML combined with modest low-level moisture return
   ahead of the front should support a narrow corridor of around
   500-1000 J/kg of MLCAPE by peak afternoon heating.

   Strong forcing for ascent associated with the approaching upper
   trough will likely encourage convective initiation by late Sunday
   afternoon into the evening along the eastward-advancing cold front.
   30-40 kt of effective bulk shear will foster organized updrafts,
   with the steep mid-level lapse rates perhaps supporting some large
   hail with initial convective development. The severe wind threat
   should increase by Sunday evening into parts of MN and
   western/central IA as storms congeal along the cold front and
   quickly grow upscale into a fast moving line. This squall line
   should gradually weaken with eastward extent across the Upper
   Midwest Sunday night as it outpaces the already modest low-level
   moisture return and weak instability. But, it may still pose an
   isolated strong/gusty wind risk until the instability becomes too
   meager to support surface-based storms. How far east this gusty wind
   potential will last Sunday night remains uncertain, so have expanded
   the Marginal Risk eastward into more of southeastern MN and
   central/eastern IA. Latest guidance also suggests that there is less
   potential for low-level moisture return into northern MN, so severe
   probabilities have been reduced across this area. 

   ...Southeast...
   The remnants of Delta are forecast by the National Hurricane Center
   to move northeastward from the TN Valley towards the upper OH Valley
   on Sunday. The surface low is forecast to remain rather weak through
   the period, although a warm front should also advance slowly
   northward across the Carolinas through Sunday evening. Around 30-35
   kt of mid-level southwesterly flow should be present across parts of
   eastern GA into SC/NC in association with Delta's remnant mid-level
   circulation. NAM forecast soundings across these areas show enough
   veering/strengthening of the wind profile in low/mid levels to
   support modest storm organization. Around 500-1500 J/kg of MLCAPE
   should also be present along/south of the warm front as low-level
   moisture gradually increases and surface temperatures warm through
   the day. Even so, mid-level lapse rates will remain poor, which
   should temper updraft strength to some extent. Regardless, given the
   marginal deep-layer shear and sufficient instability forecast,
   isolated strong to damaging winds appear possible with any storms
   that form either along an eastward-advancing surface trough or the
   warm front. A brief tornado also cannot be ruled out, primarily near
   the warm front Sunday afternoon/evening, where low-level flow is
   forecast to be slightly stronger compared to locations farther
   south.

   ..Gleason.. 10/10/2020

   CLICK TO GET WUUS02 PTSDY2 PRODUCT

   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z