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Tim from Springfield (IL)

Severe/Heavy Rain possibilities 8/16-8/18/19

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Just as soon as parts of central Illinois continue to recover from Monday night's severe weather (and the heavy rain last Sunday-Monday in parts of the sub), August severe weather returns tomorrow (Friday).  Today's Day 2 shows most of the action in the Plains, but the slight risk extends into to the Metro East and the SPI area.  And a hatched area across mid-MO to STL:


...Central Plains into the Middle MS Valley...
   Showers and thunderstorms (remnant from an overnight MCS across KS)
   will likely be ongoing early Friday morning across central/southern
   MO. Outflow from these storms (which will likely extend back into
   central KS) will act as the effective front separating the warm and
   moist conditions across southern KS/MO/IL and the southern Plains
   from the cooler conditions across northern KS/MO and the remainder
   of the central Plains and middle MS Valley. This front is expected
   to act as the primary corridor for thunderstorm development,
   although two different forcing mechanisms appear possible.

   The first potential impetus for convective initiation is convergence
   along the front amidst diurnal destabilization. However, given the
   relatively warm layer between 850 and 700 mb and lack of stronger
   large-scale forcing for ascent, there is some question whether
   storms will be able to develop along the front during the late
   afternoon/early evening. If storms do develop, very strong buoyancy
   will contribute to strong updrafts capable of large hail and strong
   wind gusts. The lack of stronger vertical shear suggest storms
   should quickly become outflow dominant. Given the presence of a
   surface boundary, a brief tornado or two is also possible.

   The second impetus for convective initiation near the front is the
   low-level jet, which is expected to strengthen across the TX
   Panhandle, western OK, and southern KS Friday evening. Warm-air
   advection into the frontal zone is expected to result in the
   development of elevated thunderstorms from east-central KS, central
   MO, and far west-central IL. Mid-level flow will be stronger here
   and the potential exist for more organized storms capable of large
   hail. Isolated very large hail (i.e. diameter greater than 2") is

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The Day 3 for Saturday hints that most of the action will be in the Dakotas and Nebraska, but marginal extends to Chicago and Milwaukee.  With a Slight Risk eventually not ruled out:



..Central Plains...
   A more nebulous surface pattern will exist south of I-80 over the
   Plains with only a weak surface trough over the High Plains, and an
   expansive area of moisture and instability. A moist and unstable air
   mass will exist over NE, KS, OK, MO, and IL, with possible early day
   storms from KS into IL. The strongest heating will occur over TX,
   western OK and into southern KS, and this will be an area for
   scattered afternoon storms as the capping is eroded. Other storms
   are possible along any outflow boundaries from earlier convection,
   but predictability is low this far in advance. While isolated to
   scattered strong to severe storms capable of wind or hail are
   possible, have opted to defer Slight Risk delineation to later
   outlooks when predictability is greater.
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ILX not ruling out storms extending into Sunday, and the possbility of heavy rain again too in parts of the CWA:


Area Forecast Discussion
National Weather Service Lincoln IL
352 PM CDT Thu Aug 15 2019

Issued at 345 PM CDT Thu Aug 15 2019

Dry and pleasant conditions will continue through this evening
across central and southeast Illinois with partly to mostly cloudy
skies. Then more unsettled weather is expected to move into the
area overnight into this weekend as a couple disturbances track
into Illinois from the central plains. Ample cloud cover will
keep moderate temperatures again on Friday, then more sunshine
during this weekend into early next weekend, will warm temperatures
to above normal levels along with more humid conditions.


.SHORT TERM...(This evening through Friday)
ISSUED AT 345 PM CDT Thu Aug 15 2019

Weak 1015 mb surface high pressure ridge extending from Lake Huron
and Lake Michigan down across IL was providing another dry day
for central and southeast IL with partly to mostly cloudy skies
this afternoon. Temps at 330 pm were in the upper 70s and lower
80s while dewpoints were in the upper 50s from Peoria nw and low
to mid 60s se of Peoria. Scattered to broken cumulus clouds over
IL at mid afternoon while thicker cirrus clouds were spreading
east into parts of northern and western CWA at mid afternoon.
These clouds were from MCS over nw MO/SW IA, far se NE and far ne
KS. Consensus of CAMs take this MCS ESE across central MO and into
central/sw IL overnight with increasing chances of showers and
thunderstorms over much of CWA during overnight, and lingering
into mid Friday morning. More redevelopment of scattered
thunderstorms possible late Fri afternoon into Friday evening
especially over central and southern CWA. SPC day2 outlook has
marginal risk of severe storms over much of CWA, with a slight
risk of severe thunderstorms sw CWA including Schuyler, Sangamon
and Christian counties sw. The risk of severe storms now appears
stronger during the late afternoon into mid evening over sw CWA if
redevelopment does occur in this area due to more unstable
conditions. There is a marginal risk of excessive rainfall for Fri
into Fri night over much of central IL, while slight risk is in sw
IL. Lows overnight mostly in the lower 60s with some mid 60s in
west central IL. Highs Friday similar to today, around 80 central
il and 80-85F in southeast IL.


.LONG TERM...(Friday night through Thursday)
ISSUED AT 345 PM CDT Thu Aug 15 2019

Another MCS possible to affect parts of CWA during Friday night
into Sat morning and have increase pops to address this
possibly as model consensus have trended higher with qpf/pops
then. SPC day3 outlook has marginal risk of severe thunderstorms
Saturday along and north of I-72 while a marginal to slight risk
of excessive rainfall too over much of area. Convection chances to
become more isolated Sat afternoon, then models show another MCS
to affect IA/WI/northern MO and into parts of central and northern
IL during Sat night into Sunday morning. Excessive rainfall again
possible but shifting further north over IL and may be a few
strong thunderstorms too. Highs Sat in the 80s, warmest in
southern CWA. Highs Sunday in the upper 80s to around 90F with
heat indices Sunday afternoon in the mid to upper 90s, approaching
100F in southeast IL.

Very warm and humid conditions look to continue from Mon thru Wed
and a bit cooler on Thu. Mid/upper level ridge expands form the sw
States toward IL early next week and also shifts the higher
chances of showers/thunderstorms further north and east. Have dry
conditions Sunday night thru Monday night, then slight chances of
convection on Tue. Have 20-30% pops Tue night and Wed with a
disturbance and weak front moving se thru area.


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New D1 outlook has Slight across most of southern IL, but the main focus will be outside the sub in C/W MO and E KS, where there's a hatched for hail:


Tomorrow's D2 has a Slight reaching western IL:


 Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0100 AM CDT Fri Aug 16 2019

   Valid 171200Z - 181200Z


[ . . . ]

...Dakotas and northern NE into IA and IL...
   Substantial height falls will occur over the Dakotas during the day
   with increasing deep-layer shear. Storms will form relatively early
   along the cold front over the western Dakotas, and will increase in
   intensity as they encounter a destabilizing air mass to the east.
   Damaging winds and hail will be possible. Models suggest storms will
   make it into western MN by late evening, but likely weaker.

   ...KS into MO...
   Storms are forecast to be ongoing from eastern KS into MO Saturday
   morning, possibly in the form of an MCS on the nose of the low-level
   jet. Damaging winds will be possible initially, but a weakening
   trend is expected after about 18Z.

   Behind this initial activity, strong heating of a moist air mass,
   beneath cool temperatures aloft will lead to strong to perhaps
   extreme instability, with MLCAPE values in excess of 3500-4000 J/kg
   over parts of KS, northwest MO, and into NE. There is spread between
   the models regarding where afternoon and evening convection will
   initiate, and this may depend on modifying outflow boundaries. At
   this time, the greatest probability of initiation appears to be
   across the KS/MO/NE/IA quad-state area. Supercells will be possible
   initially, with all modes of severe. An MCS is likely to evolve out
   of this activity by evening as it continues east toward IL.

   While significant severe is possible given the parameter space, will
   defer potential "sig" severe delineation to later outlooks when
   predictability is greater.

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The storm diminished in intensity as it hit Indy metro with highest winds off the ground and not reaching the surface.  State fair goers were advised to shelter in place inside buildings until the storm passed.  Beautiful fiery red sunset here now.

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!.78 since Friday here in my tippy bucket. The radar estimates only have one inch over me. They show a 1.5 stripe just south of me though. The convective nature must have given me a tad bit more.

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