757
FXUS21 KWNC 181856
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT September 18 2024

SYNOPSIS: Model solutions indicate increasing tropical convection and the
potential for tropical cyclone (TC) development over the western Caribbean,
resulting in an enhanced potential for heavy precipitation for portions of the
Southeast U.S. Mid-level low pressure over the Aleutian Islands and a series of
surface low pressure systems bring the potential for episodic heavy
precipitation to southeastern Alaska.

HAZARDS

Moderate risk of heavy precipitation for Florida, coastal Alabama, and portions
of southern Georgia, Thu-Sat, Sep 26-28.

Slight risk of heavy precipitation for Florida, and coastal Southeast U.S. and
Mid-Atlantic, Thu-Mon, Sep 26-30.

Slight risk of heavy precipitation for portions of southeastern Alaska,
Thu-Mon, Sep 26-30.

Slight risk of high winds for Florida, coastal Alabama, and portions of
southern Georgia, Thu-Sat, Sep 26-28.

DETAILED SUMMARY

FOR SATURDAY SEPTEMBER 21 - WEDNESDAY SEPTEMBER 25:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR THURSDAY SEPTEMBER 26 - WEDNESDAY OCTOBER 02: The highlight for the week-2
hazards outlook continues to be the potential for TC activity in the western
Caribbean. Unfortunately, ensemble spread remains quite high and it is still
very difficult to determine where and when any potential TC might develop, and
where one would go upon formation. Despite this uncertainty, model solutions
have been, and continue to be consistent in depicting copious precipitation
over portions of the Southeast U.S. during week-2. The GEFS and ECMWF
Probabilistic Extremes Tools (PETs) continue to indicate at least a 20%
probability of 3-day precipitation exceeding the 85th percentile and at least 1
inch for much of the Southeast U.S. for much of the forecast period. The ECMWF
is especially bullish, extending 3-day 1 inch totals all the way up the Eastern
Seaboard and higher probabilities of exceeding the 85th percentile for the
Southeast U.S., as well as highlighting the potential for over 2 inches for
portions of Florida and adjacent states early in week-2. Therefore a moderate
risk of heavy precipitation is posted for Florida, coastal Alabama, and
portions of southern Georgia for Sep 26-28, and a larger slight risk of heavy
precipitation is posted from roughly New Orleans, then along the Southeast U.S.
and Mid-Atlantic to the Outer Banks for Sep 26-30. A slight risk of high winds
is also highlighted for Florida, coastal Alabama, and southern Georgia for Sep
26-28.



There is good consensus among multiple model ensembles with regard to an
amplified mid-level trough over the Aleutian Islands in place at the start of
week-2 and a series of surface low pressure systems moving into the
southeastern Alaska coast, bringing periods of heavy precipitation with them.
This is supported by the ECMWF and GEFS PETs, which indicate the potential for
3-day precipitation totals to exceed 3 inches for portions of the panhandle of
Alaska for much of week-2. Uncertainty increases later in the forecast period
so for now a slight risk of heavy precipitation is posted for the southern
coast and Panhandle of Alaska for Sep 26-30, and this situation will be closely
monitored in the coming days. While there is the possibility of increased winds
associated with these systems, this appears to be mainly a maritime concern for
now as hazardous criteria are not anticipated to be met over land.

FORECASTER: Danny Barandiaran

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