Winter/Spring Potential Flood Outlook For Northern And Eastern Maine - 04/14/2022

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WINTER/SPRING FLOOD POTENTIAL OUTLOOK

NATIONAL WEATHER SERVICE CARIBOU ME

1053 AM EDT Thu Apr 14 2022

SPRING FLOOD POTENTIAL OUTLOOK FOR NORTHERN...CENTRAL...AND

DOWNEAST MAINE

This is the ninth Winter/Spring Flood Potential Outlook for 2022,

issued by the National Weather Service in Caribou, Maine. This

outlook is for Northern, Central, and Downeast Maine for the one-

week period of April 14th to April 21st, 2022.

...Active Ice Jams on the Allagash & St. John Rivers...

The potential for Ice Jam flooding over the next week is above normal

across the St. John River basin. The Ice Jam flood potential has

ended on all other rivers in Eastern & Northern Maine.

...CLIMATOLOGICAL GUIDANCE...

April so far is running above normal for temperatures with varying

precipitation conditions. Frenchville is currently averaging a

temperature of 36.5 degrees which is 3.1 degrees above normal. So

far Frenchville has seen 0.62 inches of precipitation which is

0.27 inches below normal. In Caribou the average temperature so

far for April is 36.7 degrees which is 2.5 degrees above normal.

1.69 inches of precipitation has fallen which is 0.43 inches above

normal with much of this falling as rainfall. This month NWS

Caribou has only seen 1.1 inches of snowfall which is 4.2 inches

below normal. Millinocket`s average temperature so far is 41

degrees which is 4.7 degrees above normal. They have seen 1.42

inches of precipitation which is only 0.05 inches below normal.

Bangor`s average temperature so far for this month is 43.9 degrees

which is 4.8 degrees above normal. Bangor has seen 2.05 inches of

precipitation which is 0.52 inches above normal for the month to

date.

The North Atlantic Oscillation (NAO) has held in slightly

negative to near neutral phase into early April allowing for some

blocking in the vicinity of Greenland and colder air being forced

south from Canada into the northeastern United States. Medium

range climate guidance now suggests the NAO index switching to

slightly positive phase during the second half of April as upper

level blocking near Greenland shifts southeast into the open

Atlantic. This would limit the timing and scope of colder air

reaching the Northeast.

The Arctic Oscillation (AO) has been in its negative phase

favoring troughing across the northern CONUS. Medium range climate

guidance suggests that the Arctic Oscillation will vacillate into

positive and then perhaps neutral or negative phase again by late

month. This would indicate transient troughing in the northern

CONUS with some colder air that temporarily reaches the Northeast.

Meanwhile the Pacific North America (PNA) pattern...which has

been in a negative phase is forecast to turn more neutral. This

would tend to favor a less amplified and more zonal pattern

developing.

A La Nina pattern remains present at this time. A La Nina

generally favors a variable Pacific jet stream with ridging most

prevalent across the western and southeastern U.S. and troughing

found near the Great Lakes region. The latest sea surface

temperature departure as of 11 April 2022 was -0.9F in the Nino

3.4 region. The La Nina is currently forecast to continue through

June-August 2022 either continuing or trending closer to ENSO

neutral beyond August.

A variable jet stream pattern is expected the remainder of April

with modified air quickly advancing from west to east from the

Pacific west. Cold air intrusions are anticipated to occur but

generally be short lived. Frequent precipitation events are

anticipated mainly due to an active Pacific jet stream. Keep in

mind that cutoff low systems more frequently develop during the

spring months. These low systems are typically challenging to

pinpoint with some significant error possible in the timing and

location details of QPF amounts and temperature.

The official National Oceanic and Atmospheric Administration`s 6

to 14 day outlook from 19 to 25 April 2022 calls for chances for

near normal to below normal temperatures and above normal

precipitation to start. Medium range climate forecasts then begin

to favor near normal to below normal precipitation heading into

the last week of April along with moderating temperatures.

...OBSERVED SNOW DEPTH AND WATER EQUIVALENTS...

Snow depths across the St. John River basin varies between 15 to

30 inches of snow with some isolated deeper snow across the

headwaters in the North Woods. This remains normal snow depth with

snow water equivalent (SWE) readings 5 to 9 inches with isolated

SWE to 10 inches. The SWE in much of the St. John River Basin is

around normal. Snow densities show much of this snowpack is above

the 0.33 reading for indicating a ripe snowpack. A

ripe snowpack is a snowpack that can no longer absorb

rainfall and would result in loss of snow due to melting in a rain

event.

In the Aroostook River basin snowpack ranges between Trace to 10

inches with the Caribou NWS Office sitting lower at a Trace snow

depth. There are isolated higher amounts in the forest to 15

inches across the basin. Snow water equivalents running near

normal between Trace and 5 inches. Everywhere else is bare ground

including the Moosehead Region much of the snow is gone except in

the woods cannot rule out some 5-10 inch snow depths. The

exception to this is the higher terrain of Baxter State Park where

20-38 inches of snowpack still remains with likely 7 to 12 inches

of snow water equivalent. The snowpack has melted completely in

southern & central areas where now the concern is fire weather.

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

Soil moisture remains near normal to slightly above normal. The

frost continues to thaw across the north with areas now down to

2-8 inch frost depth with surface thawing 1-2 inches occurring.

Elsewhere absorption is occurring since the frost has thawed

completely. A look at groundwater levels, courtesy of the USGS,

showed normal levels across the state with above normal readings

in Eastern Washington County. Calais was indicating groundwater

level between the 90th percentile and the highest median reading

into mid April for its 38 year period of record. The North Woods

continues to see D0-D2 drought conditions. D1 & D2 exists in a

very tiny location of Northern Somerset county near the Quebec

border. D0 conditions remain in place across western Aroostook,

western Piscataquis and the rest of Somerset counties.

...RIVER AND ICE CONDITIONS...

River flows are running above normal across the North into the

Central Highlands and Interior Downeast. Rivers are returning to

normal flows in the coastal Downeast areas.

Currently, St. John River is free and clear at the headwaters

based on observations from the Maine Forest Service on April 13th.

There is sheet ice breaking up on the Big Black River that has

jammed up near the Blanchette Road in T14 R15. The river will

continue to see ice rot and break up and will eventually flush

into the St. John River. The St. John River is mostly ice free in

the headwaters as noted by pictures from the Maine Forest Service

on the Maibec Road crossing. There remains an Ice Jam on the St.

John between Allagash and St. Francis which is approximately 9

miles long. This jam is holding up approx 7 feet worth of water

upstream that is slowly falling given the decreasing runoff. There

is also an Ice Jam on the Allagash River between the Town Dump

and the confluence with the St. John. This jam is stuck and cannot

dislodge into the St. John River due to that ongoing jam. There

is also a small jam on the Little Black River which is causing

some backwater flooding in Allagash off the Walker Brook Road.

Beyond St. Francis to Madawaska there is generally an open river

with some areas of ice left but given the increased flow much of

the ice is clear. There is an Ice Jam near Lille/Grand Isle

town line that is causing minor flooding upstream from the

extreme eastern portion of Madawaska to Lille. Beyond Lille to

Hamlin there is mixed conditions to Van Buren then nearly full ice

cover downstream to Hamlin. This ice is decaying but the river

still remains nearly 100% covered.

All other rivers are ice free and running mostly above normal

flows for mid April with Downeast rivers running near average.

...IN CONCLUSION...

The flood potential over the next week is above normal across

Northern Maine mainly in the St. John, Allagash & Aroostook River

Basins. This is due to ongoing Ice Jams, melting snowpack with

predicted warm temperatures and rainfall that will likely cause

ice movement and increased flow. The flood potential due to Ice

Jams in the Aroostook basin & all other areas south is over for

the season. The potential for open water flooding in Central and

Southern Areas remains at normal or below normal given the current

river flows. The potential for open water flooding on the

Aroostook River is above normal given the above average flow and

remaining melt with rainfall in the forecast.

The next Winter/Spring Flood Outlook will be issued on Thursday,

April 21st unless conditions warrant an update.

$$

Sinko