Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
834 am EST Thursday Feb 11 2016
high pressure will build eastward into the region today and then
move through the region tonight. An Arctic cold frontal boundary
will then move through the area Friday night. By Sunday, another
area of high pressure will build southward into the region as low
pressure forms across the southern United States by Monday. This
area of low pressure will then track up the East Coast Tuesday into
Near term /through tonight/...
730 am estf: updated for the snow band in southeast PA into SW New Jersey. Its
putting down a dusting that is causing some travel difficulty. A
Nowcast is posted as well updated snowmap and forecasts for this
morning. No model has this..N part ..in part les band trailing
into our area. If we see visibility 1 Michigan or less we will upgrade to an
Special Weather Statement. Our radar continues in vcp31 to better see the finer details,
plus its low top and very low water content.
From the middle shift below...
For a relatively quiet weather day, still have three main stories to
talk about for the today period.
Snow...as mentioned by the previous shift, low to middle level lapse
rates will be quite steep across the Poconos and northern New Jersey through
at least middle day. In addition, the middle and upper level short wave
trough will be crossing the region through this time. These factors
are conducive for scattered snow showers, or maybe even a fast
moving snow squall, across the northern half of our region. With
persistent dry air advection, moisture is limited. So even though
snow/liquid ratios could be above normal thanks to the very cold air
in place, still expect snow accumulations to remain below one inch.
Winds...a tight pressure gradient will remain over the region
through at least 18z before it starts to decrease as the surface low
lifts further away from our region. Thus, expect windy conditions
through the day. At this point though, Wind Advisory conditions
(sustained winds of at least 31 miles per hour for at least one hour or gusts
of 46 mph) are not anticipated, since the tightest pressure gradient
will be early in the day before the mixing layer gets very deep.
Having said that though, the GFS does show that the sustained
criteria could be reached for locations adjacent to the Delaware Bay,
since the direction is a favored direction for the funneling effect
over the Bay. In addition, VAD wind profiles show that 40 knots winds are
about 4000 to 5000 feet mean sea level. If the mixing layer gets deep enough,
some of that could mix down for the highest terrain in the Poconos
and northwest New Jersey. For now though, confidence is low that it will be
reached so will not issue an advisory at this time.
Cold...today begins the cold stretch which we are expecting to
continue into the weekend. While today will probably be the warmest
of the next 4 days, the region should stay below freezing, and
portions of the Poconos and northwest New Jersey may not get out of the teens.
This will be 15 to 20 degrees below normal. Given the windy
conditions, wind chill values across the region will only top out in
the teens at best.
Short term /Friday/...
high begins to build in, and consequently winds diminish, and clouds
will dissipate. As a result, should see considerable radiational
cooling, with lows in the single digits and teens and wind chill
values in the single digits above and below zero.
Long term /Friday night through Wednesday/...
our updated briefing package at midday will include more information
on the upcoming dangerous cold, including a possible wind chill
watch for Sat night which is already a high confidence likelihood.
The extended will feature both the prospects for the coldest air
of the season centered on Sunday morning and a strengthening low
pressure system tracking up the East Coast early next week.
Friday and saturday: high pressure will move through the region on
Friday. This high pressure system will give way to another Arctic
cold front Friday night. The cold front should provide enough
lift and moisture for some scattered snow showers to develop.
These may produce some light accumulations of under an inch.
Behind the front, it will be a very cold and windy period with
some additional snow showers and/or flurries in association with
the northwest flow off of the eastern Great Lakes. The favored regions to
see snow showers are in the high terrain areas of eastern PA and
northwest New Jersey. BUFKIT analysis yields the potential for 30-40 miles per hour gusts
Saturday afternoon across the region with the GFS being the most
aggressive with the gust potential. The strong cold air advection will not allow
temperatures to rise much during the day.
Saturday night through Sunday night: another potent area of Arctic
high pressure will build into the region with the coldest shot of
air of the season so far. Modeling has been holding steady on the
idea that 850 mb temperatures look to dive below -25c. Will
nudge temperatures a couple of degrees cooler than most ensemble
guidance through the weekend due to the degree of the cold air
being modeled. Strong northwest wind gusts, though not as strong
as on Saturday will continue in the wake of the departing system.
The cold and wind will result in wind chills from -10 to -30 below
zero Saturday night and Sunday morning. Please to make sure to
prepare for the cold weather that is coming. Preparations include
checking pipes and making sure your vehicle is in good working
condition. Low temperatures Sunday morning will likely near or
below zero as well. Please refer to the climate section on record
Presidents day through Tuesday night: high pressure will gradually
move east of the region and will give way to a storm system that is
currently modeled to form across the southern United States and
intensify as it moves up the East Coast. The 00z 2/11 operational
models have narrowed the goal posts of possible tracks from
earlier model runs. This also matches or is just east of the 12z
2/10 European model (ecmwf) ensemble mean track. This track GOES from south central
Alabama/Georgia northeast to the Carolina coastline then due north up the
East Coast into southern New England. Two main features are
present to track with regards to models or respective ensembles
changing the forecast track of this system in future runs. This
first is a leading shortwave which moves into the the Ohio Valley
on Monday and the second is the degree of middle- level height rises
that occur ahead of the storm system. A stronger shortwave would
tend to push the overall trough with this storm further east.
While a weaker shortwave would allow for higher middle- level height
rises leading to a further west track of the low. Right now the
favored track would result in snow changing to rain across most of
the region with the highest chances for precipitation Monday night
and Tuesday. It will likely be windy as well with the
strengthening low pressure system tracking near the region.
Wednesday: the region should gradually begin to clear out as
another high pressure system builds eastward toward the region.
Some uncertainty though as 2/11 00z European model (ecmwf) brings another system
into the region by this period.
Aviation /14z Thursday through Monday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Today...VFR scattered-broken at or above 4000 feet. Brief IFR conds in snow showers
possible in a few locations...probably kpne by 1330z. West wind
gusts increasing to 30 knots by 15 or 16z. Isolated 35 knots possible.
Tonight...VFR scattered-broken clouds at or above 4000 feet during the evening
becoming clear. Gusty west-northwest winds 20-30 knots slowly diminishing during
Friday night and saturday: mainly VFR, possible MVFR restrictions
in scattered snow showers. Northwest winds increasing Saturday
from 15-25 knots with gusts up to 40 knots Saturday afternoon.
Saturday night and Sunday...VFR conditions expected. Northwest winds
10 to 25 knots.
Monday...VFR conditions for most of the day then becoming MVFR and
IFR by evening with rain and snow.
gales in progress and glw continues as posted. An Small Craft Advisory will be
needed for much if not all of the over night hours once the gales
Light freezing spray is occurring and continues to be expected on
the Bay as well as the near coastal waters.
Our afternoon marine products will headline a new high confidence gale
watch for the period roughly 4 am Saturday through 8 am Sunday.
So while, seas and winds will start out fairly light on Friday.
However, a quick ramp up is expected after the passage of an
Arctic cold frontal boundary Friday night. Northwest winds will
increase and reach gale force by Saturday and continue gale force
through Saturday night. Confidence for gales on Saturday is
very high. Seas will rise to between 5 and 7 feet for a period as
well on Saturday. Seas and winds are expected to decrease on
Sunday. Wave heights will likely start increasing again by Monday
night in response to a developing low pressure system to our
near record cold is expected for portions of our area Sunday
morning and by far the coldest air of the season so far.
Anticipating temperatures throughout our forecast area within several
degrees of zero (wind is the equalizer) anytime from midnight
through 8 am Sunday except colder kmpo (near -12f). This has been
advertised by the GFS/European model (ecmwf) 2m temperatures cyclically since at least the
00z/7 operational cycles. Therefore, best chance for record
equaling or exceeding for Valentines day the 14th would be kabe,
kttn, kphl and kmpo.
Snow cover may help a bit I-95 northwestward...and we'll see
where we are with snow cover by Thursday evening. New dustings
appear on the way through Friday night.
As an added note here... guidance in part is being climatology biased
higher than what the oncoming GFS/European model (ecmwf) literal airmass and 2m
temperatures are indicating for Sunday morning. Temperatures Sunday morning in
the urban areas should be about 25 colder than normal. That means
guidance temperatures for phl of 5 and 6 degrees appear too warm...especially
with a normal Philadelphia low on Sunday of 28.
Record low Max's can only occur for this event on Sunday the
14th, if then.
Site 2015-16 coldest so far record low Feb. 14th ----rer low maximum
Abe 8 -1 in 1979 14-1979
Acy 10 -6 in 1979 13-1979
Phl 12 +2 in 1979 14-1979
Ilg 12 -4 in 1979 13-1979
Ridge 10 -4 in 1983
Ttn 9 0 in 1916
Ged 13 -7 in 1979
Mpo -1 -12 in 1970
So, this will be wind driven cold with many areas experiencing
wind chill values of 15 to 25 below zero...possibly 30 below in
the hills and mountains of northwest New Jersey and northeast
Marine...Gale Warning until 1 am EST Friday for anz450>455.
Gale Warning until 11 PM EST this evening for anz430-431.