Scientific Forecaster Discussion
fxus61 kgyx 141658
Area forecast discussion
National Weather Service Gray ME
1158 am EST Thu Nov 14 2019
high pressure will crest over New England tonight with dry
conditions and very cold air over the region. Conditions remain
generally dry through Thursday with only light snow showers
possible. While Friday looks warmer, it is short-lived with an
outbreak of Arctic- sourced air behind a cold front late in the
day. Below normal temperatures stick around through the weekend
with a warm trend and return of active weather next week.
Near term /until 7 PM this evening/...
update...return flow in full swing now and ocean effect clouds
are pushing onshore mainly from iwi newd. Radar is showing some
fair echoes at the moment...and forecast soundings indicate some
possible seeder-feeder mechanisms in play...so I increased pop
for the midcoast with some very light accumulation possible.
Also looking at some low orographic clouds across the mtns with
similar seeder-feeder process helping to produce some light snow
showers in those zones as well.
near record low temperatures will start the day
around sunrise under light winds.
High pressure will continue to exit the region this morning,
allowing clouds to advance, lower and thicken with time.
Thereafter, warm air advection and cyclonic flow aloft in the
form of a weak upper level trough will allow for a few scattered
snow showers over northern areas as the atmosphere slowly
saturates with time. A developing southwesterly flow may also
bring in some cu and mainly isolated snow showers to the
midcoast during the afternoon. This will be in the form of low
level moisture coming in off the Gulf of Maine.
With cloud cover limiting solar radiation after a frigid night,
expect afternoon highs to be limited to the mid 20s north to the
mid 30s south.
Short term /7 PM this evening through 6 PM Friday/...
scattered snow showers will continue over northern and eastern
areas tonight as an upper level trough passes north of the
00z model guidance suggests a prefrontal trough will pass over
the region Friday morning. This sets the stage for the passage
of an Arctic front late in the day Friday or Friday evening.
Snow showers and scattered snow squalls may occur in the
mountains with this feature. Flurries may reach southern areas
during the evening hours. More details are below with the long
term portion of the forecast.
Ahead of this front temperatures will still be below normal, but
milder than much of the work week.
Long term /Friday night through Wednesday/...
the extended forecast starts with a frigidly cold, dry airmass
and temperatures running several degrees below normal this
weekend, then the cold pattern abates next week with a return to
more active albeit uncertain weather.
Friday night, the trough axis driving the cold front at the
surface crosses with strong cold advection in its wake leading
to a period of gusty winds and possible snow squalls. Raw BUFKIT
soundings suggest wind gusts in the neighborhood of 30+ kts are
quite possible following fropa, but this will depend on low-
level thermal profiles, I.E. Extent of cold air intrusion and
depth of the mixed layer after sunset. Larger scale models are
remain a bit conservative with gusts Friday night, meanwhile
smaller scale models and ensembles including the NAM/sref
solutions are pulling in scattered stronger gusts. For now, will
trend the forecast in the upward direction with wind gusts 20+
kts until confidence grows.
In spite of dry air quickly intruding aloft, strong cold
advection and nwrly winds will be optimal to eke out available
low/mid-level moisture, producing snow showers and perhaps
squalls at least over the upslopes. Considering even more
conservative solutions produce Froude and snow squall parameter
values greater than 1, I feel comfortable bringing a brief
period of slight chance to low-chance pops across the higher
terrain and into central/midcoast Maine Friday evening.
The low levels dry out overnight as surface high pressure quickly
moves in with winds quickly tapering down by early Saturday.
Clear skies Saturday into Saturday night will lead to a good
night of radiational cooling across the area, at least
initially. High clouds coming in late in the night could
complicate matters however so stuck within the confines of
guidance, albeit near the lower bound.
Meanwhile in the active upper levels, a low aloft cuts off over
the southeast Continental U.S. This weekend. Then, a jet aloft surges down the
Front Range of The Rockies and High Plains, amplifying the
synoptic pattern and see-sawing the cut off low neward along the
Atlantic coast by Sunday. The progressive nature of the western
trough ought to keep the coastal low and associated deep
moisture just beyond the benchmark, crossing to the southeast
sometime Monday. One impact of the coastal low is advecting
warmer air aloft from the south, allowing 850mb temps to come
above freezing for the first time in several days.
The forecast for sensible conditions at the surface is quite complex
after this point with low confidence overall heading into the middle
of the week. None the less an active upper air pattern will track
disturbances over the area next week with possible coastal low
development yet again when the larger western trough reaches the
East Coast by mid-week. Thermal profiles are of even lower
confidence - so went with straight rain/snow/mix for ptype next
week with daily chances for showers.
Aviation /18z Thursday through Tuesday/...
short term...VFR conditions this morning will gradually be
replaced with MVFR and localized IFR conditions in low clouds
this afternoon, mainly across the north and along the midcoast
region. These low clouds will linger in most areas through
Long term...brief period of MVFR ceiling/IFR visible in shsn across the
north and perhaps into central Maine Friday night. Otherwise,
VFR under mostly sunny skies this weekend with gusty northwest winds
Friday night diminishing Saturday, turning northerly Sunday with
increasing clouds by Sunday evening. Nerly and possible onshore
flow develops Sunday night and Monday as a coastal low moves
neward just beyond the benchmark. This could produce restricted
ceilings at terminals over southern ME and New Hampshire. Forecast
confidence drops off a bit next week, however generally active
pattern keeps periodic chances for rain and snow showers with
associated restrictions for the foreseeable future.
short term...winds steadily increase through Friday and scas
have been issued as the southwesterly gradient increases with
time late in the work week.
Long term...gales possible Friday evening into the overnight
period after cold front passage with strong northwest flow. Have held
off on headline issuance for now until confidence in timing and
strength increases. Late Sunday into Monday, the pressure
gradient tightens substantially over the Gulf of Maine with
easterly fetch lending to building seas. Modeled guidance
currently brings 10 ft or greater waves into the waters by mid-
Monday, decreasing that evening. Afterward, periods of Small Craft Advisory with
systems ebbing and flowing for the better part of next week.
Generally low confidence exists for that time period.
Marine...Small Craft Advisory from 6 am to 6 PM EST Friday for anz153.
Small Craft Advisory from 3 PM this afternoon to 6 PM EST
Friday for anz150-152-154.
Small Craft Advisory from 1 am to 6 PM EST Friday for anz151.