SPC May 23, 2020 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook
Day 1 Outlook Image

Day 1 Convective Outlook NWS Storm Prediction Center Norman OK
0255 PM CDT Sat May 23 2020 Valid 232000Z - 241200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF FAR EASTERN IA AND NORTHERN IL THROUGH THIS AFTERNOON... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER MUCH OF THE
PLAINS STATES... ...SUMMARY...
Scattered severe thunderstorms, some with tornadoes, will cross
parts of eastern Iowa, northern Illinois and southern Wisconsin
through this afternoon. Thunderstorms with very large hail and
severe wind will affect parts of the northern and southern Great
Plains through tonight. ...20z Update... Only minor changes have been made to the ongoing outlook. The Slight
and Marginal risks were adjusted westward across portions of the TX
Panhandle based on current location of the surface dryline. As of
2030z, the dryline extended southwestward from Beaver County OK to
Cochran County TX. The Slight risk was also extended a bit further
east across far western OK based on the latest HRRR and experimental
HRRRv4 runs. Very large hail and damaging wind gusts are the main
concern with storms in this area into tonight. See recent MCD 683
and 684 for more details. Elsewhere, the Marginal risk has been adjusted across the lower MS
valley to remove portions of LA/AR and add more of MS where isolated
strong to locally damaging wind gusts are possible ahead of a
northeastward shifting MCV. ..Leitman.. 05/23/2020 .PREV DISCUSSION... /ISSUED 1129 AM CDT Sat May 23 2020/ ...Northern IL and Vicinity...
An upper low is rotating eastward across IA this morning. The
latest surface analysis has a low near Des Moines, with the a cold
front extending southward into northern MO. Southeasterly low-level
winds to the east of the low across eastern IA and northern IL are
enhancing vertical shear and resulting in favorable hodograph
structures for rotating storms later today. Visible satellite
imagery shows considerable daytime heating is occurring over much of
this region, which combined with dewpoints in the 60s will yield
afternoon MLCAPE values of 1000-1500 J/kg. All of these parameters
lend to the potential for active severe weather later today. Current indications are that storms will form along/ahead of the
cold front and spread across the ENH risk area this afternoon. Discrete storm mode appears likely, resulting in multiple
supercells. A few tornadoes are expected, along with large hail and
damaging wind gusts. Activity should approach the Chicago/Milwaukee
areas this evening. ...TX...
A strong dryline is expected to form this afternoon across west TX,
with full daytime heating and dewpoints in the mid 60s expected to
the east of the boundary. Current indications are that the cap will
sufficiently weaken to allow scattered thunderstorms to form by
mid-late afternoon from the Panhandle southward into the eastern
Permian Basin. Low-level winds are not particularly strong, but
sufficient deep-layer shear and ample CAPE (MLCAPE of 3500+ J/kg)
will pose a risk of supercells capable of very large hail and
damaging winds. This activity will spread into central TX and
perhaps western OK tonight before weakening. ...Northern Plains...
Water vapor imagery shows an upper trough moving across the northern
Rockies. This feature will help to promote thunderstorm development
over eastern WY into the western Dakotas/NE and northeast CO by
mid-late afternoon. Multiple lines and clusters of storms will
affect this region through the evening, with a risk of large hail
and damaging winds over a relatively large area. The evolution of
the storms tonight is unclear, but the pattern would be favorable
for one or more bowing complexes maintaining intensity into parts of
central/eastern NE/SD. 

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