Area forecast discussion...updated 
National Weather Service Gray ME 
753 am EST Tuesday Jan 27 2015 


Synopsis... 
strong low pressure will move northeastward to just south of 
Nantucket Massachusetts today. The low will linger around through 
Wednesday bringing a significant snowfall to our region. Another 
storm system will likely bring a general snowfall to the area on 
Friday. 


&& 


Near term /through tonight/... 
update...have adjusted pop to focus categorical along intense 
snowfall band. Bumped totals up beneath the band as it will be nearly 
stationary for the next several hours. Measuring will be nearly 
impossible...but top 10 snowfall appears within reach under this 
deformation band. Travel is going to be near if not impossible 
given the combination of snowfall rates and wind gusts producing 
whiteout conditions. 


Intense mesoscale deformation band has rotated fully 
onshore now. Snowfall rates of 2 to 4 inches per hour are occurring 
beneath this band. Have updated snowfall amounts in the previous and 
next 6 hour periods to get a more accurate up to date total 
accumulation grid to this hour. Again more focus is on the coast 
and immediate interior for higher snowfall amounts...while trimming 
the northern edge back. Snow is only now beginning to fall in the 
mountains...so at best could only have an inch or two accumulation through 
12z for these areas. 


Previous discussion...as mentioned in the previous update...00z 
model guidance has latched onto the idea of slightly weaker shortwave 
feature phasing with the initial storm system that exited the East 
Coast yesterday. This has allowed the system to slip further 
east...rather than a stronger capture and tug back to the west. 
GFS...CMC- regional...ECMWF...and NAM all have similar ideas 
regarding evolution for the rest of today. 


Snowfall... 


At this hour a very intense band of snowfall is more or less 
paralleling the coast...and slowly inching nwwd. Modeled quantitative precipitation forecast has 
been keying on the coast or just inland for several runs now. 
Tossing quantitative precipitation forecast aside and looking aloft...NAM...GFS...and European model (ecmwf) 
feature strong frontogenesis at 700 mb. Within this band of 
frontogenesis there is also a deformation maximum. The strongest 
bands of snowfall are favored just on the cool side of the 
deformation maximum...within the strongest frontogenesis. As of 
the 06-09z period this is verifying nicely. By 12z models suggest 
this signal pivots inland more...and becomes nearly stationary 
through 18z. During this time BUFKIT soundings for coastal locations 
briefly attempt to near moist absolutely unstable above 700 mb. Would 
not be surprised to see reports of thunder snow...but at the very 
least convective elements will help to increase snowfall rates to 2-4 
inches per hour at times. Have adjusted the highest snowfall amounts 
towards the coast some. The other factor to consider with snowfall 
amounts is very dry air in place and just north of the forecast area. 
Northerly winds will advect this air southward...eroding the northern edge of snowfall 
as we/ve seen for much of the night. That in combination with the 
eastward model shift will yield a much sharper snowfall gradient than 
originally forecast. For now only sightly lowered amounts in the 
north...but subsequent updates may Need More aggressive lowering of 
totals. 


Winds... 


27.00z ecwmf continued with the idea of rotating a potent low 
level jet northward across the forecast area today. At 900 mb it 
increased from its previous forecast to 80 kts. Given the deep 
cold air in place...mixing heights are quite high for a noreaster 
even with a large inversion in place. Even a fraction of this low 
level jet mixing down...especially during the heaviest 
snowfall...yields the potential for gusts above 50 kts near the 
coast. Given that winds are already gusting above 30 kts...this 
seems entirely reasonable. Increased wind forecast slightly from 
previous package. Wind potential decreases fairly quickly the 
further inland one GOES...but gusts around 25 to 30 kts will be 
possible. Based on BUFKIT soundings...best wind potential will 
occur from this morning through early afternoon. 


Temperatures... 


Cold high pressure to the north and northerly winds will ensure that temperatures 
remain fairly static through the day. Expect that much of the event 
will see snowfall in the teens and single digits. Strong system to 
our S and those northerly winds will also keep coastal front 
off shore...and any additional quantitative precipitation forecast enhancement off shore too. Cold 
temperatures and strong winds will also combine to produce bitterly cold 
wind chills. If stranded out in the storm...these conditions could 
produce a potentially life threatening situation. 


&& 


Short term /Wednesday/... 
low pressure occludes and upper low drifts across the area through Wednesday. 
This will continue -sn for much of the period...though intensity 
will be far less than that experienced today. An additional couple 
of inches of accumulations is possible. Temperatures will be on the cool 
side with gusty westerly winds. 


&& 


Long term /Wednesday night through Monday/... 
the models are in general agreement on the long wave pattern 
through early next week. However...significant differences exist 
with timing and strength of individual shortwaves leading to 
decreased confidence in sensible weather. The overall theme is 
western ridge and eastern trough for the Continental U.S....with an extended 
period of below normal temperatures and a chance for synoptic 
snows roughly every two days...with Friday - Friday night...Sunday 
night-Monday...the most likely time frames for our forecast area 
at moment. We begin the period on a quiet note under ridging 
surface and aloft Thursday. The next system arrives by Friday 
morning with a general snowfall ending Friday night. Behind this 
system...weak ridging follows for Saturday into Sunday. More 
uncertainty with the next system for Sunday night - Monday as the 
bulk of the precipitation shield may remain offshore. 


&& 


Aviation /13z Tuesday through Saturday/... 
short term...widespread IFR and LIFR is developing from southern New Hampshire to 
coastal ME at this hour. This trend will continue as heavy snowfall 
band slowly rotates northeastward. This will continue through early afternoon. 
Kleb and khie will be slower to see IFR conditions...possibly 
holding off until middle morning or later. Coastal terminals will 
see north-northeasterly wind gusts near 45 kts at times. Snowfall winds down by Tuesday 
evening...though precipitation lingers into Wednesday. Could see scattered IFR 
conditions will lingering shsn. 


Long term... 


Friday...MVFR in snow with local IFR conds pssbl. 
Northwest surface wind gusting to 25 knots. 


&& 


Marine... 
short term...storm warnings remain in effect for all 
waters...except for outer waters S of Cape Elizabeth. Here a 
period of 65 knots gusts appears likely...so have issued a hurricane 
force wind warning. Also moderate freezing spray is already 
occurring on the water based on buoy observations. Have issued a 
freezing spray advisory through Wednesday morning as a result. 


Long term... 


Thursday night - Sat...gale force winds are possible. 


&& 


Tides/coastal flooding... 
large...battering waves are building this morning right around 
high tide. This in combination with a two foot storm surge will 
allow Portland and Hampton to reach their flood stage. Winds will 
switch to the north this afternoon just prior to high 
tide...which may reduce the storm surge. 


Used the North Atlantic regional team wave runup matrices to 
forecast and warn for the two high tides today. The output shows 
wave action will allow for locally significant erosion as well as 
overwash at Fortunes Rocks...jennis...Camp Ellis and Ferry beaches 
in Maine and New Hampshire. 


Neracoos splash-over nomograms also showing significant issues at 
the time of high tide for the beaches south of Portland. 


&& 


Gyx watches/warnings/advisories... 
ME...Winter Storm Warning until 4 am EST Wednesday for mez007>009- 
012>014. 
Blizzard Warning until 4 am EST Wednesday for mez018>028. 
Coastal Flood Advisory until 6 PM EST this evening for 
mez025>028. 
Coastal Flood Warning until 6 PM EST this evening for mez023- 
024. 
New Hampshire...Winter Storm Warning until 4 am EST Wednesday for nhz002>009- 
011-015. 
Blizzard Warning until 4 am EST Wednesday for nhz010-012>014. 
Winter Weather Advisory until 4 am EST Wednesday for nhz001. 
Coastal Flood Warning until 6 PM EST this evening for nhz014. 
Marine...Storm Warning until 7 am EST Wednesday for anz150>153. 
Freezing spray advisory until 7 am EST Wednesday for 
anz150>154. 
Hurricane force wind warning until 3 PM EST this afternoon for 
anz154. 


&& 


$$ 


Near term...legro 



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