801
FGUS71 KGYX 141200
ESFGYX
MEC001-005-007-011-013-015-017-023-025-027-031-NHC001-003-005-007-
009-011-013-015-017-019-151200-

Winter/Spring Flood Potential Outlook
National Weather Service Gray ME
800 AM EDT Thu Mar 14 2024

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

The flood potential outlook for New Hampshire and Western
Maine is above normal in the mountains. Elsewhere, the flood risk
is normal as meager snowpack is counterbalanced by limited runoff
storage. The potential for flooding due to ice jams is done for
the season.

This is the sixth in a series of regularly scheduled flood
potential outlooks that are issued during the winter and
spring seasons highlighting the flood potential during the next
two-week period. This issuance represents the flood risk between
March 14 through March 28th for New Hampshire and western Maine.

...OBSERVED SNOW DEPTH AND WATER EQUIVALENT

The snow depth and snow water equivalents were well below normal
for the time of year. The two-week change in snow conditions has
been a loss for all but the mountains where repeated snow showers
added depth. Elsewhere, the snowpack has shown compression and
melt.

In New Hampshire the snow depths ranged no snow in the southern
and coastal locations, up to 6 inches north of the Lakes Region.
Snow cover and deeper snow depths are mainly concentrated across the
White Mountain region in northern parts of the state. Snow water
equivalents are below normal across most of the state except closer
to normal across the peaks of the White Mountains.From the White
Mountains to the Canadian border the snow was more robust
averaging 1 to 2 feet, upwards of 3 feet in the mountains. The
stored water in the snowpack was generally less than 1 inch in the
lower elevations, and 2 to 4 inches in the north country, and
upwards of 8 inches above 2000 feet.

In Western Maine the snowpack was limited to the foothills
northward. Below normal snow water equivalents are found across the state
except slightly closer to normal across western portions approaching
the White Mountain region of New Hampshire. In the foothills and
valleys the snow is mainly prevalent in the wooded areas and up to
12 inches deep. The stored water ranged form 0.5 to 3 inches.
From the Mountains to the Canadian Border the snow was more
continuous and ranged from 1 to 2 feet deep, highest above 2000
feet. The stored water ranged from 3 to 6 inches with locally
higher amounts.

The snow condition was compressed with high densities. A recent
rain on snow event caused melt and ripening even in the mountains
with densities around 30% or higher. The snow temperatures were
warming and primed to melt over the next two weeks. Looking ahead
the forecasts favors gradual melt the next two weeks with limited
opportunities for growth.

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

Frost Depth ranged from 5 inches in the mountains to 12 inches
across the region. Areas without a snowpack observed topsoil
thawing with water release. The groundwater remains well above
normal with additional recharge over the last few weeks as thawing
increased. 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. The
Androscoggin and Kennebec reservoirs have approximately 15-36%
less capacity than normal. Storage remains high in the Connecticut
and Merrimack watersheds where USACE reservoirs had only used
0-3% capacity. Lake Winnipesaukee...New Hampshire`s largest
lakerecently dropped from maximum recorded levels to near
seasonal normals due to continued drawdowns in February.

...RIVER AND ICE CONDITIONS...

The ice threat has ended for the season.

CLIMATOLOGY AND  TEMPERATURE AND PRECIPITATION OUTLOOKS

Very warm conditions have existed since December. By the end of
February, the winter-to-date temperatures were running in the top
5 warmest with temperatures running 4 to 8 degrees above normal.
March began unseasonably mild and wetter than normal across most
of the area with average temperature departures through the 10th
ranged from +7 to +10F above normal. The precipitation departures
through the 10th generally ranged from 2.00 to 4.00+ inches above
normal thanks to successive low systems which arrived on the
2nd-3rd...5th-7th and 9th-10th.

The winter was defined by the limited number of cold arctic air
intrusion events resulting in a paltry snowpack. Precipitation was
heavy in December and the first half of January, lessened in
February, and rebounded in March. By mid March the snowpack was
running well below normal with little to no snow south of the
foothills.

A moderate El Nino remains with observed sea surface temperature
(SST) anomalies +1.4C in the Nino 3.4 region. The El Nino has
gradually weakened with the most recent three month average Oceanic
Nino Index (ONI) +1.8C from December 2023 through February 2024.
The El Nino is forecast to remain through March-May 2024 and then
transition to ENSO-neutral conditions during April-June 2024. Late
this summer a transition to La Nina conditions is forecast. The
CPC 6-10 and 8-14 day outlooks March 19-26 generally agree with
average temperatures leaning normal short term to above normal
long term and precipitation near normal short term leaning wetter
than normal long term.

...IN CONCLUSION...

Based on the above meteorological and hydrological information,
short term flood risk above normal in the mountains and near
normal elsewhere. Groundwater levels are well above normal and
storage capacity for runoff is limited. The potential for rapid
runoff remains elevated until the seasonal green-up is underway.
The addition of snowmelt in the mountains makes the risk higher in
those areas. 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.

These outlooks will be issued every two weeks until the end of the
snow melt season, and will assess the potential for flooding
based on a number of factors. The next Spring Flood Outlook will
be issued on Thursday, March 28th.

$$
...OBSERVED SNOW DEPTH AND WATER EQUIVALENT

The snow depth and snow water equivalent was well below normal for
the time of year. The two-week change in snow conditions has been
a loss for all but the mountains where repeated snow showers
added depth. Elsewhere the snowpack has shown compression and
melt.

In New Hampshire the snow depths ranged from little if any snow in
the southern and coastal locations, up to 6 inches north of the
Lakes Region. From the White Mountains to the Canadian border the
snow was more robust averaging 1 to 2 feet, upwards of 3 feet in
the mountains. The stored water in the snowpack was generally less
than 1 inch in the lower elevations, and 2 to 4 inches in the
north country, and upwards of 6 inches above 2000 feet.

In Western Maine the snowpack was limited to the foothills
northward. In the foothills and valleys the snow is mainly
prevalent in the wooded areas and up to 12 inches deep. The stored
water ranged form 0.5 to 3 inches. From the Mountains to the
Canadian Border the snow was more continuous and ranged from 1 to
2 feet deep, highest above 2000 feet. The stored water ranged from
3 to 6 inches with locally higher amounts.

The snow condition was compressed with high densities. A recent rain
on snow event caused melt and ripening even in the mountains with
densities around 30% or higher. The snow temperatures were
warming and primed to melt over the next two weeks. Looking ahead
the forecasts favors gradual melt the next two weeks with limited
opportunities for growth.

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

Frost Depth ranged from 5 inches in the mountains to 12 inches across
the region. Areas without a snowpack observed topsoil thawing
with water release. The groundwater remains well above normal with
additional recharge over the last few weeks as thawing increased.
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. The Androscoggin
and Kennebec reservoirs have approximately 15-36% less capacity
than normal. Storage remains high in the Connecticut and Merrimack
watersheds where USACE reservoirs had only used 0-3% capacity.
Lake Winnipesaukee...New Hampshire`s largest lakerecently dropped
from maximum recorded levels to near seasonal normals due to
continued drawdowns in February.

...RIVER AND ICE CONDITIONS...

The ice threat has ended for the season.

CLIMATOLOGY AND  TEMPERATURE AND PRECIPITATION OUTLOOKS

Very warm conditions have existed since December. By the end of
February, the winter-to-date temperatures were running in the top
5 warmest with temperatures running 4 to 8 degrees above normal.
The winter was defined by the limited number of cold arctic air
intrusion events resulting in a paltry snowpack. Precipitation was
heavy in December and the first half of January, lessened in
February, and rebounded in March. By mid March the snowpack was
running well below normal with little to no snow south of the
foothills.

The weather pattern over the next couple of weeks looks to transition
into more spring-like conditions with above average temperatures
and increased precipitation opportunities. The time of year makes
it more than likely that the precipitation type will be a rain-
snow mix or rain. Temperatures are expected to continue above
normal into the spring thaw as El Nino remains dominant.

...IN CONCLUSION...

Based on the above meteorological and hydrological information,
the short term flood risk is above normal in the mountains and
near normal elsewhere. Groundwater levels are well above normal
and storage capacity for runoff is limited. The potential for
rapid runoff remains elevated until the seasonal green-up is
underway. The addition of snowmelt in the mountains makes the risk
higher in those areas. 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.

These outlooks will be issued every two weeks until the end of
the snow melt season, and will assess the potential for flooding
based on a number of factors. The next Spring Flood Outlook will
be issued on Thursday, March 28th.


$$