Winter/Spring Flood Potential Outlook For Northern And Eastern Maine - 01/19/2023

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WINTER/SPRING FLOOD POTENTIAL OUTLOOK

NATIONAL WEATHER SERVICE CARIBOU ME

230 PM EST Thu Jan 19 2023

...WINTER/SPRING FLOOD POTENTIAL OUTLOOK FOR NORTHERN, CENTRAL,

AND DOWNEAST MAINE...

This is the second Winter/Spring Flood Potential Outlook for

2023, issued by the National Weather Service in Caribou, Maine.

This outlook is for Northern, Central, and Downeast Maine for the

two- week period of January 19th to February 2nd, 2023.

The potential for ice jam flooding is normal across the St. John &

Aroostook basins. The potential for ice jam flooding is below

normal across the Piscataquis, Penobscot, St. Croix and Downeast

Coastal basins. The potential for open water flooding area wide

over the next two weeks is below normal.

...CLIMATOLOGICAL GUIDANCE...

The first half of January 2023 has mostly been characterized by a

continuation of milder than normal temperatures...above normal

precipitation and above normal snowfall north with below normal

snowfall in southern areas. Temperatures have averaged 6F to 11F

above normal during the first two weeks of January with any cold

outbreaks being very temporary.

Melted liquid equivalent precipitation departures were generally

near normal up to 2 inches above normal during the first half of

January. Snow total departures were below normal in most southern

areas during the first half of January except +5.9 inches above

normal at Caribou Maine through January 17th and +5.8 inches above

normal at Fort Kent.

Looking ahead...there still does not currently appear to be signs

for any extended below normal cold across the Northeast. A La

Nina pattern remains with colder than normal average temperatures

noted in the eastern Pacific Ocean. An active Pacific Jet Stream

is usually associated with the La Nina.

The latest Oceanic Nino Index (ONI) in the Nino 3.4 region is

around -0.7C sea surface temperature (SST) anomaly. However, sea

surface temperature anomalies have been showing positive (warming)

changes particularly across the eastern Pacific region during the

past month. According to the CPC Probabilistic outlook...the most

likely scenario is for a gradual transition from La Nina to

Neutral El Nino Southern Oscillation (ENSO) phase from February to

April 2023.

The Pacific North American (PNA) which has been in negative phase

is forecast to become positive for a time in late January before

returning to neutral by early February. This would allow for more

ridging to develop across the far western U.S. with a shift of

the trough axis into central parts of U.S.

The North Atlantic Oscillation (NAO) index has been slightly

positive (Approx +0.5SD) allowing for the jet stream to generally

remain progressive with any arctic air being transitory and

mostly remaining north in Canada. The current NAO forecast phase

shows some change to perhaps turning more neutral or slightly

negative with time. This could in turn allow time for more

secondary coastal low development or low track development further

south of the basins depending on the timing and phasing of jet

stream energy.

Overall this slight shift in the jet stream pattern still points

to transitory troughing...temporary cold and still frequent

chances for precipitation due to an active jet stream. However we

are heading now into the coldest time of the year climatologically

and we should be able to build more snowpack.

There is expected to be two perhaps three low systems with deep

moisture tracking across the area January 19-20...January 23 and

maybe January 25-26. Currently Multi-Model Ensemble Forecasts

(MMEFS) are indicating chances for some action level rises mainly

across the southern basins where the better chance for more liquid

precipitation is expected with the first low system. Beyond then

there is some uncertainty with precipitation types and amounts

pending low tracks.

The official NOAA 6 to 10 and 8 to 14 day outlooks from 24

January to 01 February 2023 are in general agreement indicating

best chances for above normal temperatures and above normal

precipitation transitioning to near normal temperatures and near

normal precipitation.

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

The Maine Cooperative Snow Survey second survey was this week

showing a rather dismal snowpack across Downeast Maine but huge

improvements across Northern Maine. Snow water equivalents are

close to normal across northern areas and 50-75 percent of normal

or less in the Downeast coastal plain to Southern Highlands.

Coastal areas from Bangor to Calais were generally reporting 1-4

inch snow depths. Snow water equivalents mostly vary from 0.75 to

1.50 inches with some water loading due to the recent mixed

precipitation event with some melt.

Snow depths along the foothills further inland mostly vary from 3

to 9 inches and snow water equivalents range from 1.50 to 2.50

inches. Heading across western mountains and across northern Maine

snow depths range from 8 to 16 inches with some locally higher

totals 20 to 25 inches across the Saint John Valley region

northwest of Caribou. Locally higher amounts 1 to 2+ feet were

found across the high peaks in the central and western highlands.

Chimney Pond near Mount Katahdin recently reported a 34 inch snow

depth. Snow water equivalents generally range from 2.50 to 4.50

inches locally more across the peaks. The highest snow water

equivalents were found along the Big Black River at Clayton

Lake...Allagash River...Fish River at Fort Kent...Aroostook River

at Washburn and the Piscataquis River at Dover-Foxcroft.

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

Frozen grounds generally 2-5 inches across the area combined with

no melt has allowed for no changes in soil moisture conditions.

Near surface soil moisture anomalies show nearly all of Eastern &

Northern Maine having above to well above normal soil moisture.

The latest Palmer Drought Severity Index Map from January 14, 2023

shows the Downeast Abnormally Wet, Greater Bangor is Extremely

Wet and much of the remaining areas are Severely to Extremely Wet.

There is below normal soil moisture across the far North Woods

along the Quebec border. The Palmer Index looks at conditions over

the span of weeks to months.

Taking a look at groundwater monitoring wells across the region

courtesy of the United States Geological Survey (USGS), we see

much of the groundwater level observing sites are extremely high

for early January. Much of the reporting sites are Much Above

Normal in the >95th percentile range with Millinocket reporting

90-95th percentile.

Lastly, given the very slow discharge of the rivers we are

looking at still very high river storages. We focus on the

observations we get for the Penobscot River basin. The Penobscot

total storage as of January 16, 2023 was 79.4% full which is 41.1%

above the long term average.

...RIVER AND ICE CONDITIONS...

As of January 18th every river, stream and creek with USGS gages

in Eastern & Northern Maine are reporting greater than 90th

percentile daily discharge values that aren`t impacted by ice

currently. This means every measured waterway is running above

normal. Overall, this means we have way above normal water in the

rivers for January.

Along the Saint John headwaters there is a mix of open water and

thickening sheet ice. Significant ice was found between Allagash

to the Saint Francis Fort Kent line. Ice thicknesses were

generally 2 to 5 inches with locally thicker chunks of ice from 10

to 15 inches.

Along the Allagash river there is a mix of water and ice with

more significant ice from the town to the confluence of the Saint

John River. Ice thicknesses here were ranging from 4 to 8 inches.

The Aroostook river is frozen between Millinocket Lake to

Masardis with a few small leads. Ice thicknesses near Masardis

were 4 to 8 inches. Between Wade and Presque Isle through Washburn

ice thicknesses are estimated 5 to 7 inches.

A significant ice Jam existed from Tinker Dam upstream 12 river

miles along the Aroostook river to Caribou Maine and water levels

have dropped significantly in this region. Ice thicknesses in this

region are estimated at 10 to 15 inches with locally thicker

chunks of ice to 2 feet.

Along the Piscataquis river there are frozen sections along the

headwaters.

The eastern branch of the Penobscot river has some frozen sections

near Grindstone extending 2 to 3 miles upstream. Significant

frazil ice was reported between Eddington and Bangor.

...IN CONCLUSION...

The potential for flooding due to ice jams is normal across

northern Maine with high flows currently occurring and significant

hummocked ice, with the risk for more flooding if ice jams

develop. Elsewhere, the flood potential is below normal given low

ice activity and high flows.

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

February 2nd.

$$

Sinko