Text Products for ESF Issued by GYX

Flood Potential Outlook
Issued by NWS Portland, ME
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Winter/Spring Flood Potential Outlook
National Weather Service Gray ME
314 PM EDT Thu Apr 18 2024

...FINAL SPRING FLOOD POTENTIAL OUTLOOK FOR NEW HAMPSHIRE AND
WESTERN MAINE...

The flood potential outlook for New Hampshire and Western Maine
is above normal through late April despite little to no residual
snowpack. Ground conditions are exceptionally wet across the
region with limited runoff storage. The risk will remain elevated
until the seasonal green-up is fully underway, which has already
started in parts of southern New Hampshire and Maine.

This is the ninth and final issuance in a series of regularly
scheduled flood potential outlooks highlighting the flood
potential during the next two-week period. This issuance
represents the flood risk through the rest of April for New
Hampshire and western Maine.

...OBSERVED SNOW DEPTH AND WATER EQUIVALENT...

The snowpack has melted out for all but the higher elevations and
north facing slopes of the mountains. The snow depth goes from
bare ground in the valleys to 1 to 3 feet above 2,000 feet. The
snowpack in these regions are ripe with high densities, and a snow
water equivalent of 2 to 5 inches.

...SOIL MOISTURE AND WATER SUPPLY CONDITIONS...

Exceptionally moist ground conditions, high streamflows, and high
reservoir and lake levels suggest very limited storage for storm
runoff. Soils in areas without snow have thawed with water release
showing up in groundwater wells. The groundwater levels remain
much above normal with additional recharge over the last few weeks
as thawing spread northward. Streamflow levels courtesy of the
USGS were running above to well above normal due to a recent rain
on snow event.

Runoff storage capacity remained below normal for the time of
year with high lake levels for most of the region. Kennebec River
Basin storage in Maine was 94 percent full which was 86 percent
above normal. The nearby Androscoggin River storage was 92 percent
full which was 47 percent above normal. Lake Winnipesaukee...New
Hampshire`s largest lake...increased to 0.95 feet above normal as
of 15 April 2024. The lake is at its full level despite almost
continuous releases.

...RIVER AND ICE CONDITIONS...

The ice threat has ended for the season.

...CLIMATOLOGY AND TEMPERATURE AND PRECIPITATION OUTLOOKS...

El Nino has continued to weaken with neutral ENSO conditions
expected through June. The active trend looks to shift into the
central U.S., giving New England a period of drier than normal
conditions through late April. The official National Weather
Service 6 to 14 day Outlook for 24-30 April 2024 leans likely
above normal temperatures and near normal to below normal
precipitation. These conditions favor continued melt in the
mountains with limited opportunities for heavy precipitation
events. That being said, until green-up has begun the region will
remain vulnerable to excessive runoff.

...IN CONCLUSION...

Based on the above meteorological and hydrological information,
the short term flood risk is above normal. The potential for rapid
runoff remains elevated until the seasonal green-up is fully
underway. Groundwater levels are well above normal and storage
capacity for runoff is limited. The coverage of snow is limited to
the higher elevations and is not expected to be sufficient to
significantly contribute to mainstem river flooding. Flash
flooding and small stream flooding in the mountains will remain a
concern until all of the snow has melted. It is important to note
that major flooding does not occur from snowmelt alone. Rainfall,
how much and in how short a period of time, is the most important
factor in determining the severity of flooding.

This is the final issuance of the Spring Flood Outlook for the
2024 season.

$$

Jamison
National Weather Service Weather Forecast Office
