Area forecast discussion
National Weather Service Mount Holly New Jersey
413 am EDT Friday may 24 2013
Synopsis...
a cold front will slowly cross the region today. A low pressure
system will develop on the front off the New Jersey coast and slowly
move northeast reaching the Canadian Maritimes on Sunday night. A
high pressure will then build east in its wake early next week. A
warm front is forecast to pass through the area on Wednesday. A
Bermuda type high pressure system should then start building into
the southeastern United States for the end of the work week.
&&
Near term /until 6 PM this evening/...
a cool, damp, dreary day is in store for much of the area today,
which will feel more like late fall instead of late Spring. A
frontal boundary will move across the area early this morning and
move offshore, before an area of low pressure develops along the
boundary just to our northeast by midday. Today will be one of those
days when the high temperature occurs early in morning, then behind
the frontal boundary, temperatures will slowly fall, or remain
nearly steady. We expect cloud cover to remain across the area for
most of the day, but if any breaks do occur and the sun comes out,
it could offset the dropping of the temperatures. Generally a
mav/met MOS blend was taken, with a non-diurnal hourly temperature
forecast.
Showers will remain possible across the area today as the cool
middle/upper trough continues to slide to the east. As low pressure
develops to our northeast along the frontal boundary, precipitation
will become more likely across our the northeastern part of our
forecast area. The airmass will be fairly stable behind the frontal
boundary, so we do not expect any thunderstorms today. Also, precipitable water
values are expected to continue to drop behind the front, so
precipitation would be expected to be mostly light, although there
could be a few brief periods of moderate rainfall.
Today will also be a rather breezy day. Once winds begin to gust
behind the front, speeds could easily reach 25-30 miles per hour with some
locally higher gusts.
&&
Short term /6 PM this evening through 6 am Saturday/...
the middle-upper low will slowly move across the area tonight, while
surface low pressure continues to slowly drift off the New England
coast. There will remain a fair amount of wrap-around moisture
across the area, especially across the northern half of the County Warning Area
overnight Thursday into Friday morning. Therefore, showers remain
possible overnight, with the greatest likelihood across the northern
zones.
Mav/met MOS guidance were fairly close for Thursday night/Friday
morning, so a blend was take for overnight lows.
Winds are expected to remain gusty through the night with gusts
25-30 mph, with some possibly locally higher gusts.
&&
Long term /Saturday through Thursday/...
the GFS initialization looked better than the WRF-nmmb overall. We
do like the way the former is handling the sharpening of the trough
in the Great Lakes, it looked correctly deeper than the WRF-nmmb
and pbly why the latter had a more progressive solution. Deep/dting
with the overall idea of the closing low not digging as much
(which is logical for late may), we leaned heavily in the gfs's
direction.
Thus on Saturday with respect to precipitation chances we were
slightly more optimistic. Last ngt's run both literally and
figuratively was the trough. We removed mention of precipitation chances far
southwest and lowered probability of precipitation central. We kept likely probability of precipitation Saturday
morning northeast as the GFS still showed some forecast middle level warm air advection
Saturday morning and an exiting trowal. The robust middle level qvec
convergence has drifted practically out of our County Warning Area by 12z Saturday.
The one aspect that has not changed though with Saturday is the
wind. The GFS especially remains fairly rambunctious about the
potential for advisory level wind gusts to occur. This is an odd
position because its normally the WRF-nmmb's milieu and the European model (ecmwf)
is assuming its usual more muted solution. The strongest winds are
coinciding where the precipitation and most cloudiness is forecast. So
while the sounding should be more adiabatic than typical under
those circumstances, it does cast some uncertainty. Farther to the
southwest the overall wind field is forecast to be lighter, but
mix to a higher level. All that being said, given that the trees
are in full Leaf out, one could possibly have advisory level wind
damage to weak trees and limbs without the wind criteria being met
given this looks to be a prolonged windy period. Its Worth a
mention in the severe weather potential statement. Stat guidance looks pretty close and looks
reasonable based on forecast 925mb temperatures.
We kept in a low chance early Saturday evening far northeast, but
the overall slightly northeast trend does not support keeping in
probability of precipitation any longer or farther to the southwest. The gradient will still
be present on Saturday night, so we are not expecting much
decoupling. We did not side with the lower stat guidance for this
reason.
The flow aloft on Sunday still has a slight cyclonic look to it
with short waves still passing through. True the model forecast
mean rh's are extremely low, but have more confidence in short
waves than rh's at this forecast point and thus slightly more
pessimistic with clouds than guidance with the convective temperature
forecast to be reached. We did lean toward the lower stat guidance for
maximum temperatures. Forecast 850mb and 925mb temperatures suggest being more
conservative and not sure if climatology is starting to exert too much
of an influence on maximum temperatures. While Sunday should also be windy,
the maximum wind gusts should be about 5 to 10 miles per hour lower.
Depending upon how quickly the high builds into our cwa, we might
have some frost issues far northwest. Otherwise a clear crisp night.
Monday still looking like the best of the three Holiday weekend days
with maximum temperatures recovering closer to climatology levels.
No big changes to the rest of the long term. We like the GFS
timing of warm frontal precipitation for Tuesday night as the European model (ecmwf) solution
has a look of convective feedback to it that it perpetuates from
the Midwest into our County Warning Area likely too fast and also too far south.
We keep the chance in for Wednesday. After that a Bermuda high
starts building westward again and we will go from the
refrigerator to the stove by the end of the week. More locations
than just reading may have a shot of reaching 90 degrees after
all is said and done with this air mass.
&&
Aviation /08z Friday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
A period of IFR conditions are expected to move across the taf sites
this morning as a frontal boundary moves across the area. The IFR
ceilings are expected to lift to MVFR later this morning and could
persist through the day. It is possible that if any sun comes out
and any heating and mixing does take place, that we could break out
to VFR late in the day. We do expect all sites to become VFR by
sunset or shortly afterward.
After the front moves through winds will become quite gusty through
remainder of the taf period.
Outlook...
Saturday...MVFR northeastern terminals and VFR elsewhere improving
to VFR all. North to northwest wind gusts could exceed 30 kts. Low
confidence on timing of improving conditions.
Saturday night through Monday...mostly VFR. Some gusty northwest winds
possible through Sunday. High confidence.
Tuesday...mainly VFR. Lower ceilings/visibilities possible at night with warm front and
precipitation. Moderate confidence.
&&
Marine...
Small Craft Advisory remains today and tonight for all of the
Atlantic coastal waters, and the Delaware Bay as winds are expected
to become quite gusty behind an approaching frontal boundary. We
started the advisory on the Delaware Bay a little sooner, as the
winds should begin gusting after the frontal passage which should be
later this morning.
Outlook...
we will issue a gale watch for Saturday and Saturday evening. There
is growing model consensus about the possibility of gale force
gusts. Lowest confidence is off the Delaware coast. Then a slow
decrease in winds to sub Small Craft Advisory conditions Saturday
overnight into Sunday. It might take as long as Sunday evening for
this to occur, especially on the ocean waters. After that we are
outlooking sub Small Craft Advisory conditions to occur for the
rest of the outlook period.
&&
Rip currents...
we continue to forecast a moderate risk of dangerous rip currents
along the coast of New Jersey and Delaware for today.
&&
Phi watches/warnings/advisories...
PA...none.
New Jersey...none.
Delaware...none.
Maryland...none.
Marine...gale watch from Saturday morning through Saturday evening for
anz430-431-450>455.
Small Craft Advisory until 8 am EDT Saturday for anz450>455.
Small Craft Advisory from 11 am this morning to 8 am EDT
Saturday for anz430-431.
&&
$$
Synopsis...gigi/nierenberg
near term...Robertson
short term...Robertson
long term...gigi
aviation...gigi/nierenberg/Robertson
marine...gigi/Robertson
rip currents...delisi/Robertson
