Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

000 
FXUS61 KGYX 231645 AAA
AFDGYX

Area Forecast Discussion...UPDATED
National Weather Service Gray ME
1145 AM EST Tue Jan 23 2018

.SYNOPSIS...
Low pressure will move east across southern New Hampshire and
coastal Maine today, spreading steadier rain across the region
ahead of it. Temperatures will still be near or below freezing
especially in interior sections, so some icing is expected.
Temperatures will warm behind a warm front over southern New
Hampshire and coastal Maine during the day today. As the low
moves east this evening it will drag a cold front through the
area with cooler temperatures expected for the rest of the week
as high pressure builds in.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Update...Main precip shield has arrived...and some heavy precip
rates are possible for the next couple of hours. This is
evidenced by some automated reporting stations recording 0.25
inches per hour...and cold convective cloud tops appearing on IR
satellite. Temps remain below freezing...so the bulk of this
will fall as freezing rain. One benefit to the heavy rates is
that some of this may run off before freezing as it comes down
hard. I have extended some of the winter wx advisories for a few
hours to cover some freezing rain while temps slowly tick up
towards 32. The winter wx advisory for Knox and coastal Waldo
has been cancelled as temps have warmed well into the 30s and
low 40s. 

ORIGINAL DISCUSSION... Steadier precipitation has moved east 
into eastern Maine early this morning, with just some light 
freezing drizzle left in its wake. The next round of steadier 
precipitation is visible on regional radar imagery and should 
begin arriving in New Hampshire around 6AM and spread eastward 
through the morning. With cold air locked in place east of the 
mountains, this precipitation will begin as freezing rain for 
much of the area. One notable exception is northwest New 
Hampshire where downsloping conditions have kept temperatures 
above freezing most of the night (currently 39 at Whitefield). 
As surface low pressure forms and tracks east across southern 
New Hampshire, expect a warm front to lift northward ahead of 
it. This front will likely push north into southern to central 
New Hampshire as well as onshore in coastal Maine, with the low 
tracking eastward along it. To the north of the front it will 
stay cold, though temperatures may warm to near freezing within 
the dammed area as the steadier rain arrives. To the south of 
the front, temperatures will warm dramatically into the 40s to 
perhaps low 50s.

Current Advisory headlines cover the expected threats today
fairly well, with the timing still lining up well. Interior
areas will hang on to the freezing rain threat into the
afternoon while coastal and southern areas warm up earlier.
Behind the warm front along the coast there could be some strong
wind gusts with the greatest threat along the Midcoast where the
Wind Advisory is in effect.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
As low pressure moves across the area it will drag a cold front
across along with it. Winds will shift to the west behind it and
expect precipitation to come to an end. Within the cold air
dammed areas, temperatures behind the front will warm up, while
other areas will see a gradual cooling with temperatures falling
below freezing again Wednesday morning. Only minor warm up
expected on Wednesday with cold air continuing to pour in. Winds
may gust to 25 or 35 MPH as this cold air moves in. Will see
some lingering snow showers mainly in the mountains, but these
may spread east out of the mountains during the afternoon.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
The main concern for the long term portion of the forecast will 
be the system affecting New England next Saturday into Monday. 
Before that though, we will see a warming trend. At the surface,
high pressure will translate east from the central CONUS 
Thursday and Friday before sliding offshore. Ensemble mean 850mb
temps go from near -20C Thursday to around 0C by Saturday 
morning as a warm frontal boundary will be pushing into the 
region by late Friday night/Saturday morning. Southerly flow 
will transport in modified subtropical air. 

The operational Euro as well as the Canadian are slower with the 
weekend system and in better agreement with both the ECMWF 
ensemble system and also the GEFS members than the operational 
GFS. A slower eastward progression could mean more mixed 
precipitation initially and possibly the development of a 
coastal storm as the system would have more time to organize and
deepen. This event could also have quite a bit of QPF with it, 
and this combined with warmer temperatures initially may once 
again bring a concern for ice jams and river flooding. On the 
backside of the system cooler air would begin to filter in with 
a cold frontal passage Monday, changing all precipitation to 
snow. Have edged closer to these ideas/the Euro solution for 
the extended forecast, however confidence is not high in any 
solution at this time. 

Temperatures look to stay below freezing through Saturday
morning when the warm air advection arrives. Highs will be well
above normal for the weekend in the upper 30s to near 50 before
dropping again behind the cold front early next week.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Short Term...IFR conditions expected most of the day today with
light freezing drizzle in the morning, becoming steadier as
the morning goes on. Temperatures warm above freezing in
southern and western New Hampshire as well as coastal Maine this
morning, while interior areas may see the freezing rain last
into the afternoon. A cold front moves across the area this
evening, bringing an end to the precipitation and a return to
VFR conditions for most areas outside the mountains.

Long Term...We'll see variable cloudiness initially Wednesday
evening into Thursday for the mountains very VFR conditions
develop. Elsewhere VFR will prevail through Friday with lowering
ceilings and precipitation developing on Saturday in rain and
snow.

&&

.MARINE...
Short Term...Southerly flow ahead of low pressure moving across
northern New England today will likely reach gale force for much
of the coastal waters. A cold front crosses the area this
evening, bringing the southerly gales to an end as winds shift
to the west. Cold advection on Wednesday will allow winds to
strengthen again to 30 or possibly 35 KT.

Long Term...Marginal SCA seas over the far eastern waters will
drop late Wednesday night into Thursday morning...however winds
will remain gusty through Friday morning. Higher seas and near
gales will return Saturday in gusty SW flow.

&&

.HYDROLOGY...
With expected rainfall today the additional run off into area
rivers largely affected by ice may lead to additional ice
movement or ice jams. Any ice jams that form or move may lead to
minor flooding. The Flood Watch covers the areas where this
threat is greatest.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Flood Watch through late tonight for MEZ012-018>028.
     Winter Weather Advisory until 6 PM EST this evening for 
     MEZ007>009-012>014-018>022.
     Winter Weather Advisory until 2 PM EST this afternoon for 
     MEZ023>026.
     Wind Advisory until 9 PM EST this evening for MEZ027-028.
NH...Flood Watch through late tonight for NHZ003>015.
     Winter Weather Advisory until 6 PM EST this evening for NHZ001-
     002-004-006.
     Winter Weather Advisory until 2 PM EST this afternoon for 
     NHZ003-005-007>015.
MARINE...Small Craft Advisory until 11 PM EST this evening for ANZ153.
     Gale Warning until 11 PM EST this evening for ANZ150>152-154.

National Weather Service Glossary of Abbreviations