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
posted by Advackia at 9:31 PM
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