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New Day 1 Outlook >
WPC Day 1 Excessive Rainfall Outlook Valid Through 12Z Today
Risk of 1 to 6 hour rainfall exceeding flash flood guidance at a point
Updated: 0819 UTC Fri Jul 19, 2024
Valid: 12 UTC Jul 19, 2024 - 12 UTC Jul 20, 2024
Day 1 Excessive Rainfall Forecast
Forecast Discussion
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
826 PM EDT Thu Jul 18 2024
Day 1
Valid 01Z Fri Jul 19 2024 - 12Z Fri Jul 19 2024


01Z Update...

A cold front pushing south and east will continue to
provide the focus for showers and thunderstorms capable of
producing some intense rainfall rates and some instances of
excessive rainfall...especially from the Carolinas towards the
middle Gulf coast for a few more hours. The Slight risk area which
had been located over northwest Louisiana was expanded to cover
on- going convection farther east in the immediate to short term
and expanded west to cover the signal for a risk of excessive
rainfall to the east as shown by the HREF probabilities from 18Z
and from the deterministic QPF from the HRRR.

Across the western United States...saw little reason to make more
than cosmetic changes based on short-term radar and satellite


...Southern Mid-Atlantic & South...

16Z update... Convection is expected to bring up in coverage and
intensity around 17-18Z for southeast Virginia and eastern North
Carolina. Refer to Mesoscale Precipitation Discussion #648 for
further details on the flooding potential. Very minor adjustments
were made to the Marginal and Slight Risks across the Mid-Atlantic


A cold front will advance southeastward into the Mid-Atlantic
region today while the western portion slows across the southern
Plains. Along and ahead of this boundary will remain a focus for
deep moisture (PWATs > 2 inches in some places of the Mid-
Atlantic, Southeast and Gulf Coast states. The greatest threat for
heavy rainfall appears to be with and ahead of the front along
pre-frontal convergence axes from southeastern Virginia into
eastern North Carolina. In addition to the anomalous moisture and
low level convergent axes, upper levels will be favorable within
the right entrance region of a jet positioned east of an upper
trough axis advancing eastward through the Great Lakes, with an
area of upper level diffluence forecast over the eastern Mid-
Atlantic region due to the presence of a ridge off of the Southeast
coast. For the 24 hour period ending 12Z Friday, 00Z HREF guidance
supports EAS probabilities for 3 inches of 30 percent between
Albemarle and Pamlico Sounds along with standard probabilities for
8 inches of 30-40 percent in the same location. While this is
typically a less flash-flood prone region, these probability values
are not super common and could be highlighting the potential for
locally significant rainfall totals somewhere from southeastern
Virginia into eastern North Carolina.

...Eastern Texas into Western Louisiana...

16Z update... The Marginal Risk was expanded westward to cover
portions of the Texas Hill Country were there is an active Flood


A second and relatively small Slight Risk was maintained for
locations near the Arklatex and southward along the Sabine River to
account for locally greater potential for heavy rain. Upper level
diffluence will be maximized here and greater coverage of
thunderstorms are during the afternoon/overnight near/south of an
850 mb low located near the Arklatex. Individual members of the 00Z
HREF and RRFS indicate localized QPF maxima of 4 to 6+ inches.

...Southwest to the Southern Rockies...

16Z update... The latest guidance has shown small reductions in
QPF amounts across portions of Colorado that lead to a very small
trimming of the Marginal's northern boundary in southwest and
central Colorado. The best potential for excessive rainfall
persists for central New Mexico and south-central Colorado.


Another day of monsoonal convection is expected for
the southern Rockies into the Southwest as the center of the mid-
level ridge shifts slightly west from the Four Corners region
through Friday morning. The overall pattern, available moisture and
instability are expected to remain largely unchanged from
Wednesday, resulting in similar threats for heavy rainfall and
flash flooding across the region. Rainfall accumulations of 1-2
inches in less than an hour and localized maxima of 2-3 inches are
expected with a focus across the Rockies where low level moisture
flux will be maximized.


Day 1 threat area:

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