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Area Forecast Discussion (AFD)

Issued by Caribou, ME (CAR)

FXUS61 KCAR 201658

Area Forecast Discussion
National Weather Service Caribou ME
1258 PM EDT Sat Apr 20 2019

A stationary front will slowly lift back northward as a warm 
front across the region today into tonight. The region will 
remain in a very moist air mass this weekend and into early next
week. Low pressure will approach from the southwest on Monday.


1230pm update...The stationary boundary remains just south of
Bangor eastward towards north central Washington County with 
temp and dew point gradients of around 20F. Although the bulk 
of the rainfall has fallen, there is another round of heavier
showers approaching from New Hampshire that will be funneled 
along the frontal boundary later this afternoon towards Bangor 
and northern Washington County. There will be some elevated mid
level instability but confidence is not high enough to add 
thunderstorms at this time and . The boundary lifts north 
tonight and lows will occur in the evening with steady or rising
temperatures and fog as the night progresses. There are signs 
of elevated instability tonight too, but it appears that 
isolated thunder would be the worst outcome. The entire area 
will be in the warm sector on Sunday, but an onshore flow and 
some continued showers will make for a chilly day on the coast. 
The warm spot will be in NW Aroostook where 70F is possible for 
the first time since early last October. The forecast challenge 
is whether the inversion can be broken in locations such as 
Caribou, Houlton and Bangor and temperatures can rise above 
current expectations.

Previous Discussion...
Moderate to locally heavy rain across the whole area today as 
warm, moist air from the southwest overrides cool low level 
northeast flow. Surface cold front slid just a bit further south
than expected, and as of 4am is just south of Bangor. Expect 
the front to begin to inch back north as a warm front today and 
then surge north tonight through the whole area, with steady or 
slowly rising temperatures. Areas of fog another hazard. Rain 
will be more intermittent tonight than today and favoring 
eastern portions of the forecast area. See hydrology discussion 
for more on the flooding threat.


Rainfall will be less organized across the Rgn Sun and Sun ngt 
as sct rn shwrs with all of the FA in semi-warm sector 
conditions. Areas of morn fog will lift across the area by 
midday, xcpt alg the very coast where patchy fog will persist 
even into the aftn with areas of fog returning on land late Sun
ngt into Mon morn.

Another weak sfc low associated with the remnants of the SE U.S,
upper low will likely spread more organized rnfl upwards to 0.25
to 0.50 inches back into spcly the SE hlf of the FA Mon contg 
into Mon eve with cooler air movg back into the area Mon ngt as 
steadier rnfl moves E of the FA, leaving late ngt sct rn and 
higher trrn NW rn-sn shwrs.


Longer range Models are only in fair agreement with the
evolution of wx systems for the mid to late week. Most models do
agree that low pres from a s/wv complex alf from S Cntrl Can and
the Nrn great lks could bring the Rgn the next chc of precip
late Tue ngt til Wed eve, but differ on the tmg and placement of
the best dynamics. This system will be colder, bringing the
potential of wet snfl durg morn and ovrngt hrs with stronger
dynamics, but we are not committed to mention any sig snfl attm
given model spread of outcomes. We do go with max PoPs in the
likely range. After a break on Thu thru Fri morn, another low
pres system from the midwest could bring additional precip msly
in the form of rn to the rgn late Fri into Fri ngt, but there is
less certainty with this system, which appears at odds with
CPC's 6-10 precip outlook which favored increased probs of drier
conditions attm.


NEAR TERM: Widespread rain and low clouds today and tonight.
Generally IFR or LIFR. Low level wind shear an issue at most TAF

SHORT TO LONG TERM: Mainly MVFR clgs with areas of IFR clgs and
vsbys with more organized rnfl, msly ovr Downeast sites on Mon
and then all sites late Tue ngt into Wed.


NEAR TERM: Moist southerly flow with areas of fog over the
waters. Small craft winds today ease somewhat into tonight,
though seas remain above 5 feet into tonight.

SHORT TO LONG TERM: A lengthy pd of SCA seas will linger thru
Sun and even into Sun ngt before seas subside below 5 ft on Mon
and cont so thru Tue. Otherwise, patchy to areas of marine fog 
will cont to at least Mon morn as moist sub trop air comes into 
contact with the cold Gulf of ME ssta's. Went with blended 
WW3/NWPS guidance for fcst wv hts thru these ptns of the fcst.


This weekend marks one of the most potentially eventful hydro 
events in years that covers much of the forecast area. The 
combination of remaining deep snowpack in northern zones and the
clash with a very warm and humid air mass on the backside of a 
Bermuda High will put a lot of water in the rivers. A stationary
front will mark the boundary of the clash across the state 
into Saturday and bring three separate hydro concerns. First is
remaining ice jams on the Aroostook and Saint John Rivers. The 
second concern is urban and small stream flooding due the 
combination of heavy rain and snow melt into Saturday. The last
concern will be the response of main stem rivers Sunday into 

In terms of the ice jams, a Flood Warning remains in effect 
today along a portion of the Aroostook River. The gauge at 
Washburn is reading nearly 17 feet as of early this morning and
is right on the border between minor and moderate flood stage. 
The gauge will continue to show fluctuations and Aroostook 
Emergency Management reported that Gardner Creek Road near 
Washburn remain closed due to an ice jam that extends from 
upstream of the Washburn bridge towards Crouseville. Emergency 
Management is also watching the Parsons Road between Washburn 
and Presque Isle. We are watching ice jams on the Saint John 
near Saint Francis, Frenchville and Van Buren, but have no need 
to issue warnings at this time. Most or all ice jam issues 
should be resolved by later this weekend as rivers continue to 

A point Flood Warning also remains in effect for the 
Mattawamkeag above Mattawamkeag until further notice. The river 
is near 14 feet early this morning and is expected to slowly 
rise to 16 feet by early Tuesday morning. At 14 feet, flooding 
begins along the Bancroft Road between Wytopitlock and Danforth.

Snow melt and rainfall could cause minor flooding road issues 
These types of issues will be exacerbated by locally heavy 
rainfall today for small streams. The Flood Watch is now in 
effect through Monday evening. The combination of rainfall of 
1.5 to 3 inches of rain along with significant snowmelt in areas
that still have snow on the ground will lead to significant 
rises on larger streams Saturday and Saturday night...and on 
main stem rivers Sunday into early next week. There is 
confidence that smaller streams will flood. There is also high 
confidence that some areas will experience minor to moderate 
flooding. Confidence is not as high as to whether any areas will
experience major flooding, but it is a possibility. There are 
uncertainties in terms of the exact remaining SWE that will 
empty into rivers. According to dam operators, storage capacity 
in the Penobscot watershed is favorable and that will help 
mitigate potential main stem issues.


ME...Flood Watch through Monday evening for MEZ001>006-010-011-015-
MARINE...Small Craft Advisory until 6 PM EDT this evening for 



Near Term...Foisy
Short Term...VJN
Long Term...VJN