textproduct: Caribou

WHAT HAS CHANGED

- Issued a Cold Weather Advisory valid until 10 AM Sunday

- Upgraded areas including and south of central Piscataquis, northern Penobscot, and southern Aroostook counties to Winter Storm Warnings. A Winter Storm Watch was issued for northern Piscataquis and central Aroostook counties. A Winter Storm Advisory was issued for northwest Aroostook and northern Somerset counties.

- Increased snow totals for the Sunday night through Monday night storm based on a slight northward shift of model guidance

KEY MESSAGES

1) A frigid air mass combined with breezy winds will result in very cold wind chills continuing through the remainder of this weekend

2) High confidence a significant winter storm will impact the region Sunday night through Monday night with the highest totals over Downeast Maine

3) Colder than average temperatures continue this week

DISCUSSION

KEY MESSAGE 1...A frigid air mass combined with breezy winds will result in very cold wind chills continuing through the remainder of this weekend

KEY MESSAGE 1 DESCRIPTION... As of mid-day today, temperatures are currently struggling to reach above 0 degrees and winds remain breezy resulting in very cold wind chills as low as -25 degrees over the north. Winds will start to relax this evening as high pressure to our west builds in and the pressure gradient over our area starts to decrease. However, the center of the high will still be just off to our west by Sunday morning resulting in a weak pressure gradient just over northern and eastern Maine. Current model guidance is expressing high confidence that there will be a light breeze overnight which should favor some modest low level mixing. This should prevent strong radiational cooling and temperatures bottoming out well below guidance, but it will mean wind chills remain well below zero, as low as -25 to -35 over the north and -15 to -25 over southern areas. Given that skies will be clear tonight some areas, especially valleys, still have the potential to experience some radiational cooling and thus have lowered temperatures in those places slightly.

KEY MESSAGE 2...High confidence a significant winter storm will impact the region Sunday night through Monday night with the highest totals over Downeast Maine

KEY MESSAGE 2 DESCRIPTION... A strong low pressure system is expected to redevelop off the mid-Atlantic coast Sunday afternoon and move northeast along the New England coast. The most recent model trends show the track of the storm slightly farther north and thus forecast snow totals were increased over much of the area, especially for northern Maine.

Snow should begin in central Maine, the Bangor region, and Bar Harbor Sunday evening based on the latest high resolution guidance trends, however, would not be surprised if the onset is delayed an hour or two due to ample residual low-level dry air from the high to our north that will take time to saturate. Snow spreads northeast Sunday night as the low approaches with flakes expected to be falling everywhere by just after midnight.

Currently expecting the heaviest snowfall to be in Downeast Maine between just before midnight through early Monday morning. Model soundings show very favorable profiles with nearly all of the saturated layer below 500mb in the dendritic growth zone. Combined with ample lift in the layer this should contribute to very high snow to liquid ratios exceeding 20 to 1 resulting in very efficient, fluffy snowfall.

There has been a slight northern shift in projected low track for the storm, as seen across nearly all ensemble spreads and was reflected with the newest run of the NBM. Though moderate to heavy snowfall remains on track for the Downeast region, with over a foot of snow likely in many areas, there is now increased uncertainty in snow amounts across the northern half of the CWA. If the QPF gradient on the northern edge of the storm is tight enough, storm totals in the north may only reach 2 to 4 inches. However, especially if the northern trend continues, however slight it may be, much more substantial QPF amounts may make their way into northern Aroostook and Piscataquis counties, such that totals make a run for closer to 8 or 9 inches. For this reason, a watch has been issued for northeast Aroostook and northern Piscataquis counties. Further north, even a continued northern trend will probably not be enough of a shift to bring warning level snow, so northern Somerset and northwest Aroostook counties now have an advisory hoisted.

Snow amounts Downeast, though confidence is high in warning level totals, do have some uncertainty in exact numbers. Aside from QPF, discussed above, the biggest complicating factor is that of snow to liquid ratios (SLRs). Forecast soundings from the GFS and NAM suggest very deep DGZ for areas Downeast, which could result in SLRs surpassing 25:1, and a very fluffy snow that may even at times top out over 30:1! That said, a LLJ will continue to build through Monday morning, and the increase to low to mid level winds will result in damage to crystal structure, lowering SLRs. With this forecast, stuck with around 20:1 ratios to continue to capture the fluffy snow character without catching onto any extreme case at this point.

KEY MESSAGE 3...

KEY MESSAGE 3 DESCRIPTION... With the arctic air mass still in place over the forecast area through the upcoming work week, temperatures are projected to run around 2 standard deviations below normal throughout the forecast area, with highs in the teens and lows in the single digits above zero Downeast and around zero across the north. With a sustained upper level trough overhead through the week, enough wind may exist such that wind chills make a run for advisory Tuesday and Wednesday nights.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Through Sunday...VFR. W/NW winds 10 to 15 kts with gusts up to 25 kts decrease to 5 to 10 kts tonight, becoming light and variable Sunday afternoon. LLWS possible beginning this evening and continuing through about midnight tonight.

Sunday night...Conditions deteriorate to IFR/LIFR in snow first at southern terminals late evening and at northern terminals around midnight. Light winds early becoming E/NE at 5 to 10 kts.

Monday through Monday Night...IFR conditions expected for southern terminals, and probable for northern terminals, through Monday due to snow. Conditions improve back towards MVFR Monday night. Potential for periods of blowing snow by KBHB/coastal terminals. Winds NE 5 to 15 kts, switching to the NW overnight. Gusts 20 to 25 kts.

Tuesday through Thursday...MVFR/VFR with W winds 5 to 10 kts, shifting NW on Thursday. Gusts to 20 kts possible each afternoon.

MARINE

Through Sunday night... Below SCA winds on the intracoastal waters by around midnight tonight and by early Sunday morning on the coastal waters. Gale conditions expected on all waters Sunday night with seas building to 6 to 8 ft. Moderate freezing spray expected through about mid day Sunday with light/moderate freezing spray expected Sunday night.

Gale conditions will likely continue through Tuesday morning before finally tapering below 35 kts on the coastal waters. Intracoastals will have gusts 25 to 35 kts through this time. Seas 6 to 10 ft with the snow storm Monday through Monday night. Gusts 25 to 30 kts likely to continue through the middle of the week on the coastal waters. Light freezing spray on Monday becomes moderate Monday night through Tuesday night. Freezing spray remains possible through the middle of the week.

CAR WATCHES/WARNINGS/ADVISORIES

ME...Cold Weather Advisory until 10 AM EST Sunday for MEZ001>006- 010-011-015>017-031-032. Winter Weather Advisory from 7 PM Sunday to 3 AM EST Tuesday for MEZ001-003. Winter Storm Watch from Sunday evening through late Monday night for MEZ002-004. Winter Storm Warning from 7 PM Sunday to 3 AM EST Tuesday for MEZ005-006-010-011-015>017-029>032. MARINE...Small Craft Advisory until 7 AM EST Sunday for ANZ050-051. Freezing Spray Advisory until 11 AM EST Sunday for ANZ050>052. Gale Watch from late Sunday night through Tuesday morning for ANZ050-051. Small Craft Advisory until 1 AM EST Sunday for ANZ052. Gale Watch from late Sunday night through Monday evening for ANZ052.