FOUS30 KWBC 200718
QPFERD
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
217 AM EST Mon Feb 20 2023

Day 1
Valid 12Z Mon Feb 20 2023 - 12Z Tue Feb 21 2023

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Gallina


Day 2
Valid 12Z Mon Feb 20 2023 - 12Z Tue Feb 21 2023

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Gallina


Day 3
Valid 12Z Tue Feb 21 2023 - 12Z Wed Feb 22 2023

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM NORTHEAST
MISSOURI TO NORTHERN INDIANA...

...Midwest from Northern Missouri to Southern MI/Northern Ohio....
A strong dampening shortwave races out of the desert southwest
accelerating through the Southern Plains into the Ohio
Valley/Great Lakes driven by the digging northern stream kicker
wave and nose of expected 170kt jet streak across the Central
Plains by the end of the period. This will spur very strong
cyclogenesis across the Central High Plains into the Missouri
Valley accelerating the low level jet with highly anomalous
moisture flux across the broad warm sector. At the start of the
period (22.12z) the sharpening warm front should extend from near
Kansas City across central MO toward the Ohio River, broad
20-25kts of sfc to boundary layer warm advection should drive the
warm front northward throughout the day. As the low takes shape
by early afternoon, very strong moisture flux convergence near and
downstream of the surface cyclone combined with weak available
instability should allow for focused convective development across
becoming more scattered in nature further downstream across
IL/IN/OH given weaker low level flow and instability. Isallobaric
wind flow should back the strengthening low level flow while the
LLJ strengthens to over 50-60kts advecting deeper moisture with
total PWat values over 1.5" perhaps even up to 1.6" as ECENS and
GEFS ensemble show 3.5 to 4 standard anomaly values across the
Mississippi River valley for the low level moisture flux
parameter. Solid northeasterly flow north of the front should
sharpen and steepen the warm front and with directional
convergence should further expand convection across W IL toward
Chicagoland by evening hours. With the backed flow due to the
strong pressure falls, the convergence axis will broaden generally
parallel with the motion of the cyclone and deeper layer steering
flow. This will allow for favorable training profiles. While
cell motions will be very fast, limiting rainfall duration...the
length of this convergence axis should support and axis of 2-3"
with isolated pockets of higher totals possible.

Soil conditions are anomalously dry per NASA SPoRT relative soil
moisture fields through 40cm depth nearly 30-40% which is in the
1st to 5th percentile. Given the rates and hard, dormant ground
conditions much of the rainfall at this intensity is probable to
run off there is good confidence that the short duration should
result in scattered incidents of excessive rainfall and possible
flash flooding and as such, have maintained the Slight Risk of
Excessive Rainfall from the Day 4 period into the short range.=20
Global models seem to have honed in on a axis from north to
northeast MO across Western IL toward Northwest IND, peak
rains/rates and duration should be over north-central IL and may
glance the southern portions of Chicagoland, though a trend
southward with time could not be ruled out given limited
instability would be greater in this direction.

Other considerations are proximity to the sharpening cold air,
perhaps supporting a broad streak of freezing rain conditions
north of the frontal zone across southern WI/northern IL into the
Lower Peninsula of MI, as such the bounding Marginal Risk area to
the north is a bit tight and more uncertain given ice formation.=20
As the cyclone races into the Great Lakes, the LLJ will veer and
become less orthogonal for the ascent pattern across NE IND into
Northern Ohio, but should still be high enough to suggest still
some isolated flooding concerns to expand the Marginal as far east
as the PA/OH border.=20


...Southern Plains, Ozarks to the Lower Ohio River Valley...
Strong height-falls associated with the shortwave will drive the
associated cold front quickly through the Central Plains.=20
Greatest potential for intense rainfall rates may occur with quick
imitation and slow initial cell motions across northeast TX,
eastern OK and southeast KS before the cold front presses too
quickly for prolonged duration for extreme rainfall totals. As
such a broad Marginal Risk of Excessive Rainfall remains
highlighted across Northern Texas through much of central MO
including western AR and eastern OK. Orthogonal moisture flux
into the Boston and Ouachita ranges of AR may allow for earlier
shallow cell development ahead of the main line suggesting a bit
higher risk for enhanced rainfall totals, but there is not
sufficient evidence consistency to delineate a higher risk
category at this time, but will continue to monitor trend
especially as the event enters the Hi-Res CAM window.=20

Gallina



Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-0XMDVLuHI0BZoeYszWYdglwI3o4clmpZ4SxR2oGIqA4= QNWnTQUnsGWqzptZwu8Rsz40q0JOZEG5V581t224t8gzNlI$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-0XMDVLuHI0BZoeYszWYdglwI3o4clmpZ4SxR2oGIqA4= QNWnTQUnsGWqzptZwu8Rsz40q0JOZEG5V581t2245qIKDus$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-0XMDVLuHI0BZoeYszWYdglwI3o4clmpZ4SxR2oGIqA4= QNWnTQUnsGWqzptZwu8Rsz40q0JOZEG5V581t224_YLwAOk$=20


$$



=3D =3D =3D
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