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FXUS61 KCAR 110310 AFDCAR

Area Forecast Discussion National Weather Service Caribou ME 1010 PM EST Sun Dec 10 2023

SYNOPSIS
Intensifying low pressure tracks across Maine Monday and will draw a cold front across the region Monday evening. High pressure builds Monday night into Tuesday. A cold front moves through Wednesday. High pressure builds south of the waters Thursday.

NEAR TERM /THROUGH MONDAY NIGHT/
10pm update...The storm track for Monday continues to ease southward and eastward with 00Z analysis and guidance. This means less wind worries for locations such as Bangor and interior Downeast. The worst of the wind appears to be most likely in coastal Washington County. As the threat of high winds decreases, the other side of the pendulum swings towards snow in the North Woods. However, the more southward track is driving down precipitation and it looks like max snowfall will fall shy of 10 inches except in higher terrain above 1500ft elevation. Nonetheless, the strong winds following the end of precip remain a worry...with regard to trees loaded with heavy, wet snow. Areas west of Rt 11 in Aroostook County will have the most snow. Locations such as Caribou and Presque Isle may pick up a quick inch or two on the backside...which will create travel headaches as temperatures plummet.

While temperatures will not be as warm as previously thought on Monday, heavy rainfall remains a big concern with rapid runoff over the partially frozen ground. With the southward shift in the low track, the max corridor of rain appears to easing slightly south of I-95. However, this corridor is still susceptible to 3 to 4 inches of rain and possibly 5 or more.
This provides a good likelihood of some urban and small stream flooding issues to include the Bangor and Ellsworth areas. Most of the precip should be over by early afternoon.

In terms of winds, the more southerly low track will create strong stability except in Hancock and Washington counties. The powerful winds aloft appear likely to stay trapped above the inversion for the Bangor area and all areas north of a line from Brewer and Orrington towards Danforth.

Powerful Storm Impacts Maine Tonight into Monday Evening...

Setup...Strong storm system we've been advertising still on track to begin impacting Maine tonight. Overall, setup is quite dynamic, with a slow-moving frontal boundary setting up over the forecast area oriented SW/NE tonight. Then with the support of a strong 500mb shortwave and upper level jet, a surface low rapidly intensifies as it moves NE along the front and over the area Monday. Lots of moisture to work with from the Gulf of Mexico, with very high precipitable water values along/east of the front. The FGEN forcing will increase along that boundary increasing rainfall rates along with a southerly wind component aiding in upslope enhancement.

Models...Uncertainty continues to exist this evening with where the boundary sets up across our FA. It will extend SW to NE across the area. 12z GFS, Canadian and NAM trended a little more southeast with the boundary extending from Midcoast Maine to just South of Hodgdon to Danforth area. ECMWF continues to be a little more NW with the boundary versus the overall trend. AI models show a continued slightly more easterly trend with the boundary. Opted to go with a trend being your friend as a forecaster and slightly shifted the boundary. This will play into adjustments to the precip type and winds seen below.

Rain/Flooding...Combination of melting snowpack, partially frozen grounds and very heady rainfall poses a threat for flooding across much of the CWA. Strong frontal forcing along the boundary across our CWA will strengthen tonight and be the focal point for heavy rainfall rates. PWATs are climbing to 0.75-1.00 inch above climatological normals. Heavy rain will be possible in nearly the entire FA tonight into Monday AM. We will see precip type changes in the North Woods which will be mentioned below. Given the less than likely chance of dew points being >40F in Northern Piscataquis opted to remove this zone from the Flood Watch otherwise the Flood Watch remains in place for Eastern Aroostook, Central Highlands to Downeast coast from late tonight through Tuesday AM. Additional hydrological concerns are addressed in the hydro section below.

Wind...Tonight ahead of low pressure tracking NE towards Maine a 925mb low-level jet will increase to 80-95kt and push into the Maine coast by morning. This will extend from the Midcoast into Downeast Maine and will likely penetrate inland across interior Downeast. The boundary will play a crucial role since if you are on the cold air side of the front winds will be very light due to winds remaining aloft of the inversion. Portions of the Central Highlands southeast of I-95 towards the Downeast coast will have a good shot at mixing a large portion of the LLJ down to the surface. Forecast soundings show the LLJ below the steep inversion around 900mb with 50-70kt winds below the inversion.
This will result in winds gusting 40-50mph SE of I-95 in the southern portions of Aroostook County into far eastern portions of Penobscot against the border with Hancock county. Hancock and Washington county have the best shot at gusting 55-65mph north of Route 1 with areas along the shore south of Route 1 having the best chance at gusting up to 70mph. Right at the immediate coastline and on top of Cadillac cannot rule out slightly higher gusts. Highest confidence in 70mph gusts will be in coastal Washington County with moderate-high confidence for coastal Hancock county. Inland the gusts confidence is moderate due to uncertainty with the boundary
For now
opted to keep the Wind Advisory and High Wind Warning in place as is.

Snow...This has been another tricky part of this forecast with the continued trend east in the models setting us up for potential of dynamical cooling to increase snow chances. At this time opted to take the low on that SSW to NNE path through Maine from Midcoast to approx Danforth area. Historical analysis for events in Maine suggest more snowfall across the North Woods to Route 11 area in Northern Penobscot and Aroostook County.
Additionally, this favors some more snow into Eastern Aroostook to the New Brunswick border. Forecast soundings indicate strong dynamical cooling on the NW side as FGEN forcing moves in aloft.
Tonight, along the Quebec border expect rainfall to change to snow after midnight into Monday AM pushing eastward. Cannot rule out some brief sleet and/or freezing rain as cold air works under the warm air aloft till the cooling changes ptype to snow.
Snowfall rates possibly will reach 1-2 inches per hour as temperatures fall below freezing across the North Woods into western St. John Valley from Fort Kent westward into Monday.
Snow will be wet and heavy as the column is isothermal. Winds will be light intially but as the low tracks NE through Maine the pressure gradient induced W-NW winds will gust up 30-40mph in spots. This poses the risk of power outages from Fort Kent westward along Route 161 into Allagash. Given the increased snow going with totals of 6-9 inches with isolated higher amounts opted to upgrade N Somerset and NW Aroostook to Winter Storm Warning for heavy mixed precipitation. Issued a Winter Weather Advisory for mixed precipitation in N. Piscataquis county.
Lastly, by midday into late afternoon cannot rule out snow reaching Route 11 to Mapleton, Washburn, Presque Isle and Caribou areas and these locations may pick up a few inches of snow that may require a winter headline but opted to wait for now with the flood risk first.

Additional threats...Coastal flooding is expected to be mainly a wave runup issue around the 9AM high tide on Monday. See the coastal flood section below. Lastly, temperatures late Monday into Monday evening as the storm departs NE expect rapid temperature fall. This may result in refreeze of untreated surfaces with potentially a flash freeze if the winds don't dry surfaces up first.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/
Fair and with avg to slgtly below avg hi temps can be xpctd Tue behind Mon's storm with dmnshg WNW winds. Warm advcn begins quickly by Tue Eve ahead of an Alberta clipper s/wv with anti- diurnal ovrngt temp trends. Isold to sct sn shwr PoPs are xpctd across Nrn areas ahead to just behind the cold frontal passage passage late Tue Ngt into erly Wed Morn with little in the way of accumulation. Brisk NW winds return for the FA behind the cold front for Wed Aftn and Wed Ngt with little in the way of radiational cooling Wed Ngt even for protected NW vlys. Outside of isold narrow St Lawrence sn shwr streamers across the N, dry conditions are xpctd with below avg temps with semi- arctic air behind the front.

LONG TERM /THURSDAY THROUGH SUNDAY/
Recent CPC 6-10 day outlooks confirmed by Tdys latest 12z long range models have been consistent in advertising Nrn anomalous component of flow alf ovr Nrn New Eng with abv avg 500mb hts for the long range. This implies msly dry conditions for this ptn of the fcst. After chilly, brisk conditions on Thu, temps look to modify by Fri before another clipper s/wv brings somewhat colder conditions on Sat, with the cold frontal passage late Fri Ngt looking dry at this tm. The next chc of any rn/sn shwrs for the FA with the next Alberta clipper s/wv with be Sun Ngt into Mon with little if any in of measurable precip. Temps look to be be abv avg from Fri thru Sun attm.

AVIATION /03Z MONDAY THROUGH FRIDAY/
NEAR TERM: MVFR at BHB, IFR/LIFR elsewhere. LLWS at northern terms early. IFR/LIFR tonight for all sites. LLWS likely at southern terms tonight into tomorrow. IFR/LIFR due to vsby/cigs in rain, heavy at times. RA becomes SN from 16-20z at FVE, CAR, PQI tomorrow with SN possible at HUL by 22z. RA before 18z at southern terms becomes -SHRA. LLWS comes to an end by late day.
Surface winds light and variable at northern terms through 06z becoming N 5-15kt. Winds at northern terms shift NW after 18z tomorrow becoming 10-20kt with gusts up to 30kt. Southern terms S winds 10-20kt tonight with gusts up to 35kt becoming S 20-35kt tomorrow with gusts up to 50kt at BGR and 60kt at BHB. Winds shift W-NW after 20z tomorrow and decrease to 15-25kt.

SHORT TO LONG TERM: Tue - Thu...Msly VFR clgs with intermittent MVFR clgs with isold sn shwrs Nrn TAF sites spcly Wed until Thu Morn. Lgt to mdt SW winds becmg NW Wed Aftn and contg into Thu.

Thu Ngt - Fri...Low VFR clgs Nrn TAF sites to unlmtd VFR Downeast sites. Lgt to mdt W to SW winds.

MARINE
NEAR TERM: Storm Warning remains in effect 1AM to 7PM Monday for dangerous wind gusts across the coastal waters. Southerly gales rapidly develop this evening becoming storms overnight. Winds gusting up to 60kt with a few gusts up to 65kt possible especially over eastern waters. Winds will drop to gusts up to 40kt Monday afternoon as winds shift W. Southerly swells rapidly increase tonight 7-15ft by daybreak with a period of 7-8 seconds. Swells become 18-22ft over the coastal waters out 25nm.
Intra-coastal waters will see 10-16ft. Tomorrow's wave period will be 11-12 seconds. Waves will begin to subside after winds shift W-NW.

SHORT TO LONG TERM: Winds and seas will msly be at or abv SCA thresholds thru Fri, with strong SCAs possible Tue Ngt into Wed Morn with SW winds and again Wed Ngt into Thu Morn with NW winds with possible gale force wind gusts for this second pd. Winds and seas will drop below SCA lvls by the weekend. Kept with blended wv model guidance for this update. Long pd swells of 10-12 sec pds will msly compose wvs with a secondary 5 to 8 sec shorter fetch group.

HYDROLOGY
Melting snowpack and heavy rainfall to pose a hydrologic threat across a large portion of Eastern and Northern Maine. Ice is present on some of the rivers but will not be that big of a concern. There is frazil and pancake ice that has frozen in place on the St. John and Aroostook River basins along with other smaller creeks and streams across much of the CWA. We saw significant compaction and melting of the snowpack across Maine today. Frost depth here at NWS Caribou is 3 inches and is generally 1 to 4 inches across the CWA. In this snow remaining we generally see 0.5 to 1.0 inches of SWE that is likely to melt tonight with this event.

The combination of heaviest rainfall, SWE melting and the partially frozen grounds corresponds to a flood threat on small creeks and streams. The Piscataquis River which is prone to rapid rises and has a complex terrain in the basin is likely to experience minor flooding. The Northeast River Forecast Center is predicting the Piscataquis at Dover-Foxcroft to rise to Minor Flood Stage on Monday. In addition, large rivers will experience rises Monday into Tuesday AM before cresting which could send some locations into action stage. Not expecting flooding at this time, however highly isolated issues may occur as rivers approach bankfull. Lastly, urban and poor drainage flooding is possible with excessive rainfall and potentially clogged drains.

TIDES/COASTAL FLOODING
The high tide near 9AM Monday morning represents the biggest risk for any coastal flooding and wave runup issues. There are two mitigating factors. First, it is not a particularly high astronomical tide. Second, peak surge is about 4 to 5 hours after the high tide based on current projections. In this scenario, wave runup becomes the primary concern. Seas approaching 10-16 ft could deposit rocks on roads exposed to the open ocean. That includes Mount Desert Island locations such as Seawall Road and coastal roads on the Schoodic Peninsula. Do not anticipate needing any coastal flood warnings, as this looks like either a coastal flood statement or advisory scenario.

CAR WATCHES/WARNINGS/ADVISORIES
ME...Winter Storm Warning from 1 AM to 7 PM EST Monday for MEZ001- 003.
Flood Watch from 1 AM EST Monday through Tuesday morning for MEZ002-005-006-010-011-015>017-029>032.
Winter Weather Advisory from 3 AM to 7 PM EST Monday for MEZ004.
Wind Advisory from 1 AM to 7 PM EST Monday for MEZ006-011-015.
High Wind Warning from 1 AM to 7 PM EST Monday for MEZ016-017- 029-030-032.
MARINE...Storm Warning from 1 AM to 7 PM EST Monday for ANZ050>052.

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Bonsecours
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Sun -- 02:54 AM EST     4.22 meters High Tide
Sun -- 04:43 AM EST     Moonrise
Sun -- 07:16 AM EST     Sunrise
Sun -- 09:13 AM EST     1.20 meters Low Tide
Sun -- 02:01 PM EST     Moonset
Sun -- 03:07 PM EST     4.85 meters High Tide
Sun -- 03:51 PM EST     Sunset
Sun -- 09:54 PM EST     0.72 meters Low Tide
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Bonsecours, Quebec, Tide feet

St-Jean-Port-Joli
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Sun -- 02:45 AM EST     4.48 meters High Tide
Sun -- 04:42 AM EST     Moonrise
Sun -- 07:16 AM EST     Sunrise
Sun -- 08:49 AM EST     1.11 meters Low Tide
Sun -- 02:00 PM EST     Moonset
Sun -- 02:55 PM EST     5.14 meters High Tide
Sun -- 03:50 PM EST     Sunset
Sun -- 09:26 PM EST     0.85 meters Low Tide
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St-Jean-Port-Joli, Quebec, Tide feet

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