Western Maine Hydrologic Outlook Statement - 01/08/2021

Hydrologic Outlook

MEC001-005-007-011-013-015-017-023-025-027-031-NHC001-003-005-007-

009-011-013-015-017-019-151245- Hydrologic Outlook

National Weather Service Gray ME

731 AM EST Fri Jan 8 2021

...WINTER/SPRING FLOOD POTENTIAL OUTLOOK...

The flood potential is below normal for western Maine and New

Hampshire.

The threat of flooding due to ice jams is below normal.

This is the first in a series of regularly scheduled flood potential

outlooks that are issued during the winter and spring seasons. 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.

...CLIMATOLOGICAL GUIDANCE...

November temperatures were 4 to 6 degrees above normal and this

warmth continued into early December. The rest of December featured

large swings in temperatures with significant early season snowfall

followed by a warm rain system towards the end of the month. This

rain system depleted the early season snowpack and caused

widespread river flooding across western Maine and New Hampshire

with rivers still running above normal. December ended with

temperatures running 2 to 6 degrees above normal with above normal

precipitation.

After a modest snow and mixed precipitation event to start

January there has been a notable pattern shift with the storm

track suppressed well to our south. This shift in the storm track

can be attributed to a strong upper level ridge and blocking to

our north thanks to a negative North Atlantic Oscillation (NAO).

This dry pattern is expected to continue through mid-January with

storminess suppressed to our south. Generally, in negative NAO

patterns temperatures are favored to run below normal, but medium

range guidance indicates that temperatures will run near to above

normal. There are signs that by mid-January the blocking

associated with the negative NAO will shift further northward,

which would allow the storm track to shift closer to northern New

England and more active weather going into the second half of the

month.

The Climate Prediction Center`s 6 to 10 day outlook calls for

above normal temperatures and below normal precipitation. The 8 to

14 day outlook calls for temperatures to be above normal with

near normal precipitation.

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

...NEW HAMPSHIRE...

Snow depths across New Hampshire are mostly 10 inches or less with

bare ground near the seacoast. Only across the high elevations in

northern New Hampshire do snow depths exceed 1 foot. Snow depths

are below to much below normal across all areas of New Hampshire.

An inch or less of water equivalent is contained in the snow pack

across areas below 1000 feet. Above 1000 feet...snow water

equivalents increase marginally between 1 and 3 inches. Snow water

equivalents are below to much below normal across all areas of

New Hampshire.

...WESTERN MAINE...

Snow depths across western Maine are below 5 inches near the

coast with bare ground in extreme southern Maine. Across the

interior snow depths are mostly under 10 inches and the only

locations with depths that exceed a foot are locally confined to

elevations above 1000 feet. Snow depths are below normal across

all of western Maine.

Snow water equivalent is well below normal for the time of year

and ranges from little if any in southern York county to 1 to 2

inches near the Canadian border.

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

Although New Hampshire and western Maine were experiencing

drought conditions through the Fall of 2020...above normal

precipitation in November and December have led to significant

improvement in drought conditions. Soil moisture anomaly maps from

January 6 indicate near normal soil moisture across Maine and

slightly below normal soil moisture across extreme western Maine

through much of New hampshire. The latest Palmer Drought Severity

Index from 2 January 2021 shows near normal conditions across New

Hampshire and western Maine. The Palmer Index looks at conditions

over the range of weeks to months.

Reservoirs in the Androscoggin River basin are 75.3 percent full

which is 15.8 percent above normal. Reservoirs in the Kennebec

River basin are 77.1 percent full which is 20.2 percent above

normal.

Lake Winnipesaukee in New Hampshire is running just slightly above

normal for early January.

Groundwater levels courtesy of the USGS are mostly in the normal

range with the exception of below normal being in Northern New

Hampshire.

...RIVER AND ICE CONDITIONS...

River flows across New Hampshire are near to above normal and

above to well above normal across Maine. In fact...flows at the

head waters of the Kennebec River basin are at record high flow

levels.

The very warm start to winter combined with the rain at the end of

December has led to much of the ice in place to be flushed out.

...IN CONCLUSION...

Based on the above information flood potential is below normal

across western Maine and New Hampshire. River flows will continue

to run above normal, but with the lack of precipitation expected

and the snowpack will limit the potential for flooding.

The threat of flooding due to ice jams is below normal. Most of

the river ice was flushed out during the rain and thaw events of

late December.

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.

The next Winter/Spring Flood Potential Outlook will be issued on

Friday 22 January 2021.

$$

DS