Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
412 AM EDT Sun Oct 02 2022

Day 1
Valid 12Z Sun Oct 02 2022 - 12Z Mon Oct 03 2022

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS
OF SOUTHERN UTAH AND SOUTHWESTERN COLORADO...

...Four Corners Region...

An upper-level trough will be slowly tracking across the West
while multiple shortwaves traverse the base of the trough. These
impulses along with sufficient forcing, diurnal heating and PW
values upwards of 2 inches will support and maintain showers and
thunderstorms across much of the Four Corners region and into
western Colorado and southern Wyoming. Some of the CAMs are
showing rainfall rates around 0.50+ inch/hr, particularly over
central/southern Utah and into Colorado and with areal averages of
1+ inches as well. The Slight Risk that was already in effect to
encompass vulnerable terrain of southern Utah into far
southwestern Colorado was expanded farther to the west and
southwest across southern Utah to reflect the latest QPF trends.

...Mid-Atlantic...

A frontal system will continue to track east from the Mid-Atlantic
region during this period; however it will continue to be a focus
for lingering showers and thunderstorms over this region, with
higher amounts possible across portions of Virginia, Maryland, New
Jersey, and Delaware. The QPF gradient is expected to sharpen as
high pressure settles into the Northeast and allows a steady
easterly flow.   Some the 12Z guidance members show heavy amounts
developing along this axis of strong onshore flow and ascent but
there is also a fair amount of model spread to lower the
confidence with regard to if and where this swath of heavy rain
may occur. The Marginal Risk area was maintained with minimal
adjustments to reflect the latest WPC forecast.

Campbell


Day 2
Valid 12Z Mon Oct 03 2022 - 12Z Tue Oct 04 2022

...THERE ARE MARGINAL RISKS FOR EXCESSIVE RAINFALL ACROSS THE
MID-ATLANTIC COASTAL REGION AND ACROSS THE SOUTHWEST INTO THE
CENTRAL HIGH PLAINS...

...Southwest to the Central Plains...

The area of focus will have shifted to the south and east during
this period. As the upper trough axis continues to shift slowly
east, fairly anomalous moisture will accompany the associated
frontal band as it sags south and east across the Southwest.
Multiple rounds of showers and thunderstorms are expected to fire
up over the Southwest and Rockies region, tracking or part of the
area that received moderate to heavy rainfall during the day 1
period. QPF amounts may be as high was 1 to 2 inches and when
combined with the previous day's storms may warrant an eventual
upgrade across portions of the region. At this time, the Marginal
continued to highlight the areas with the elevated threat for
excessive rainfall. Adjustments were made near the Four Corners
state border area and further west to cover the terrain wast of
Phoenix.

...Mid-Atlantic...

Showers and thunderstorms will continue to linger across eastern
portions of the Mid-Atlantic region, with heavy rains possible
along the immediate coast. Given the potential for multiple days
of rain and wet antecedent soil conditions, a Marginal Risk area
was maintained along the coast from the Delmarva to southern New
Jersey.

Campbell

Day 3
Valid 12Z Tue Oct 04 2022 - 12Z Wed Oct 05 2022

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHWEST AND THE CENTRAL HIGH PLAINS...

The cold front will push east and south into the Southern and and
Central Plains while the trailing portions remains over southern
Arizona and New Mexico. There will still be abundant moisture
streaming northward into the system, so convection is expected to
persist and maintain across much of New Mexico and into the High
Plains. The threat for moderate to heavy rain will remain elevated
therefore a Marginal Risk area spans from southeast Arizona to
southern Nebraska.

Campbell


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt