Quantitative Precipitation Forecast Issued by NWS
000
FOUS30 KWBC 130017
QPFERD
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
817 PM EDT Tue Mar 12 2024
Day 1
Valid 16Z Tue Mar 12 2024 - 12Z Wed Mar 13 2024
...01Z Outlook Update...
A few thunderstorms have developed near/just east of the Kansas
City, MO area. Both models and observations suggest that the
orientation of the convection could favor localized spots of
backbuilding within the moist/instability axis across
western/northern Missouri for a few hours tonight, boosting local
rain rates into the 1 inch/hr range on a localized/spotty basis.
Flash flood potential should remain low (less than 5% coverage),
and no areal delineations are added to the outlook.
Cook
Day 2
Valid 12Z Wed Mar 13 2024 - 12Z Thu Mar 14 2024
...A MARGINAL RISK OF EXCESSIVE RAINFALL IS IN EFFECT ACROSS
PORTIONS OF THE CENTRAL PLAINS AND MID-MISSISSIPPI VALLEY...
Sharpening trough out west will aid in the development of a lee
surface low within the front range of the Rockies on Wednesday,
strengthening through the period with accompanying 85H and 7H low
pressures ejecting eastward into the plains. A warm front will
develop ahead of the surface reflection across the central plains
and Mid-Mississippi Valley, lifting north through the afternoon
time frame. A surge of elevated theta-E`s will occur south of the
warm front with Gulf moisture advecting north thanks to prominent
southerly flow ahead of the surface low to the west. Instability
fields across guidance have become more robust over the past 24
hrs, along with the addition of the latest CAMs guidance at range
in agreement with the global deterministic. Mid-level shortwave
ejecting from the southwest within the difluent pattern aloft will
help trigger a round of convection across portions of the plains
within the confines of the warm front generally positioned over
eastern KS into western MO, advancing northward towards the NE/IA
border as the boundary continues its northward propagation.
Locally heavy rainfall in excess of 1"/hr is becoming more likely
with the latest 12z HREF probability fields signaling a stripe of
up to 30% probability for exceeding the above interval during the
Wednesday evening time frame, along with a 20-30% signal for at
least 2"/3-hrs positioned over southeastern NE into northwest MO.
This is generally along the warm front where hi-res deterministic
has been most bullish in the general placement of the boundary and
areal thunderstorm coverage during the initial development
tomorrow evening.
As we head through the overnight into Thursday AM, there`s some
discrepancies on the handling of the maturing 85H low as it ejects
eastward through KS. The trend has been for a strengthening of the
subsequent 85H low in-of central and northern KS which would
provide ample support for a band of heavy rainfall to the north of
the closed circulation within the developing CCB axis. Convective
risks will be much lower due to the lack of sufficient buoyancy
more co-located downstream along and south of the warm front.
However, the ample moisture available within a broad expanse of 2+
deviations above normal PWATs signifies another local QPF maximum
somewhere within the northern periphery of the low-level
circulation. As of now, the prime candidate is likely within
eastern NE where some deterministic shows north of 1" QPF within a
6-12 hr window after 00z Thursday, even some deterministic
eclipsing 2" over the time frame of note. Latest ECMWF ML model
output is also fairly consistent in showing a secondary QPF
bullseye within the aforementioned zone, capable of localized
flood potential within any small towns or urban corridors near
Omaha/Lincoln. As of now, have added a MRGL risk encompassing the
Quad state area across northeast KS, northern MO, central and
southern IA, as well as eastern NE. Recent drought will likely
limit some significant impacts within the above corridor, but hard
soils from the lack of precip this winter and the threat of
training within generated cold pools in the convective area of
interest may lead to isolated flash flood returns, especially in
any storms that exceed 1.5"/hr or greater.
Kleebauer
Day 3
Valid 12Z Thu Mar 14 2024 - 12Z Fri Mar 15 2024
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE LOWER ARKANSAS VALLEY INTO THE LOWER MISSISSIPPI VALLEY...
...20z Update...
The primary changes to the D3 ERO were for an expansion of the
MRGL risk into the central Midwest and Mid-Mississippi Valley
where trends in guidance and ML algorithms have increased the
convective coverage and potential heavy rain threat into the above
areas. There will be a long west to east QPF signature stretching
from the north-central plains through the Midwest, including the
northern half of IL through WI/MI as the surface low ejects
eastward and the primary ascent pattern shifts in tandem. A broad
zone of 0.75-1.5" of precip will be possible within the northern
axis of QPF with locally higher totals over IL thanks to lingering
instability brought by a tongue of higher theta-E`s located south
of the prevailing warm front bisecting the region. There was
enough consensus to include the mid-Mississippi Valley up through
IL for a MRGL risk with the convective pattern anticipated
downstream within the warm sector.
The primary zone of impact still remains over the Lower
Mississippi Valley into east TX where a sagging cold front will
act as a focal point for convective development and subsequent
training thanks to flow aloft running parallel to the boundary,
along with a strong convergence pattern within a zone of
appreciable instability. Rainfall totals on the order of 1-2" will
be common within much of AR down into northern LA and east TX with
local totals exceeding 3" plausible given the latest deterministic
and NBM probabilistic output within the upper quartile range of
outcomes. There is still some discrepancy within the deterministic
suite on where exactly the front will be located which will play a
significant role in where the heaviest corridor of rain will
occur. Based on the latest ECMWF ML guidance and CIPS analogs,
there`s some merit to the threat being a bit further south than
where some guidance (GFS/CMC) is focused with a stronger bias for
a cold front in the expected pattern evolution to press further
south. The highest threat for impacts is likely within central and
southern AR into northern LA which includes a significant portion
of the urbanized corridors within the states above. For that, have
adjusted the SLGT risk a bit further south, along with the MRGL to
account for the historical trends and latest bias-corrected QPF
footprint.
Kleebauer
...Previous Discussion...
The low level southerly flow is expected to strengthen
significantly late Thursday into early Friday across the eastern
portions of the Southern Plains into the Lower Arkansas and Lower
Mississippi Valleys downstream of the strengthening closed low
over the Southern Great Basin, PW values expected to rise to 2 to
2.5+ standard deviations above the mean in this increasing PW
axis. Overall favorable large scale conditions, strong frontal
convergence, well defined upper difluence, in this anomalous PW
axis will support increasing convection late Thursday into the
early hours of Friday along and ahead of the strong front pushing
southeast through the Southern Plains into the Lower Arkansas
Valley. There continues to be north-south model spread with
respect to where the max convective qpf axis will set up. The NAM
is the farthest north, EC, EC mean and CMC, the farthest south and
the GFS, GEFS mean and UKMET in between. The slight risk was
drawn to encompass the current model spread, with only some minor
changes from the previous outlook for this period. The slight
risk is across areas that have had below average precip over the
past few weeks and subsequently relative high FFG values. The
heaviest precip totals over the past few weeks and the most
saturated soils area well to the southeast of the slight risk area
across portions of the South and Southeast. Given this and the
continued spread in the max qpf axis, the risk was kept at slight
for the time being. The biggest change to the previous outlook
was to trim the north end of the marginal risk to the south from
northern Illinois to southern Missouri/far southern Illinois.
Model consensus is for mostly moderate precip amount here, across
a region where soils are not saturated.
Oravec
Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt
$$