Heavy Rainfall in the Southern Plains and Mississippi Valley; Thunderstorms in Eastern Colorado on Thursday

A multiple day heavy rainfall event will begin to set up from the Southern Plains into the Mississippi Valley Thursday, peaking in intensity over the holiday weekend. Widely scattered thunderstorms are expected to develop across eastern Colorado Thursday afternoon and evening. Large hail will be the primary hazard. Read More >

889
FXZS60 NSTU 210112
AFDPPG

Area Forecast Discussion
National Weather Service Pago Pago AS
212 PM SST Wed May 20 2026

.DISCUSSION...
Heavy thunderstorm activity developed earlier this morning on the
far west side of Tutuila Island produced strong and gusty winds
with heavy downpours for a short time. These gusty winds prompted
a wind advisory for the west side of the island, only, as trees
were uprooted and tree branches breaking, loose items being blown
around with a hut roof blown off. The thunderstorms remained
active offshore to the north of the area throughout the day. These
conditions are also shown on the upper air observations (RAOB)
from this afternoon (21/00Z). The atmosphere remains unstable for
the rest of the day. On the latest satellite imageries, these are
embedded at the tail end of the trough linge that brought
torrential rainfall at the beginning of the week.

However, model data shows this trough migrating further east-
southeast by Thursday morning as a ridge builds from the
northeast. Once the trough passes the area, another broad high
pressure system to the southwest moves south of the area. This
high pressure system will bring fair weather conditions from
Thursday through at least Sunday. By Sunday night, model solutions
show a low pressure system move just south of the islands, turning
winds northeast and pulling in moisture from the north. This will
increase the potential for showers for the rest of the forecast
period.

Thus, expect scattered to numerous showers with possible
thunderstorms and variable winds for tonight. Scattered showers
with variable winds is expected for Thursday through the rest of
the week, with winds increasing to southeast at a gentle to
moderate breeze. Showers will likely increase to numerous with
light and variable winds thereafter.

&&

.Marine...
Seas have been gradually subsiding to lower heights within the
last 12 to 16 hours. Seas of 6 to 8 feet recorded at the PacIOOS
Aunu`u buoy is expected to continue on a downward trend tonight
through at least Thursday morning. However, model data show seas
slightly building to around 6 to 8 feet again by Thursday
afternoon and likely remaining through the end of the forecast
period. Thunderstorm activity within the area of responsibility
(AOR) can also elevate seas and surfs nearby. The elevated seas
may pose a threat to small crafts for this time frame. In the
meantime, no other significant swell is expected for this forecast
period, and ocean conditions will be monitored for any changes.

&&

.PPG WATCHES/WARNINGS/ADVISORIES...
NONE

&&

$$

JTAllen