Scientific Forecaster Discussion
fxus61 kphi 240957
Area forecast discussion
National Weather Service Mount Holly New Jersey
557 am EDT Tue Oct 24 2017
a slow moving cold front will cross the area today and then move
offshore tonight. High pressure is expected to nose up from the
southwest and south for the second half of the work week. Another
cold front from the west is anticipated to arrive on Sunday. Low
pressure may develop along the boundary after it moves off the coast.
High pressure will build back over the area early next week.
Near term /until 6 PM this evening/...
npw Wind Advisory expanded for gusty se winds to near 40 kt
this morning as per observations 3-430am am. Have heard of
trees down in Delaware and pns/lsr's Post as reports arrive and
time to issue. Just had 54 kt at Ship John Shoal!
06z/24 NAM has trended back to some of the slower wetter
versions. I have to think the NAM is outperforming the other
models for this event...timing a big shot of wind early today
and also modeling the showers closer to the approaching front.
Bands of showers...some heavy developing newd into our area this
morning ahead of a progressive cold front with marginal
instability but considerable wind. Since the front probably
won't slow down much...rainfall amounts will be less. Still
1 to 2.5" amts in a few places with most areas less than 1
inch. Southeast winds gusty 35-45 mph this morning with isolated
higher gusts of 55 - 60 mph. Please see swody1 on svr and have
played it slight chc but if it occurs, damaging wind potential.
Just not getting much lightning at this time but that could
change...so no guarantees on outcome.
Rain ends from west to east faster than previous forecast.
Forecast basis was a 50 50 blend of the 00z/24 GFS/NAM MOS, and
the 230 am wpc quantitative precipitation forecast.
Short term /6 PM this evening through 6 am Wednesday/...
showers may still be lingering over Atlantic coastal sections
of New Jersey and Delaware at 6 PM but should move off the coast by 10 PM.
Partial clearing but not much wind as it turns light west to
northwest. Dense fog patches may form in the residual moist
boundary layer though the MOS guidance doesn't have it...and I
dont think the MOS and sref handle shallow moist fog situations
Depending on the low temps between 11 PM and 1 am we may have a
record warm min. If you were just using this mornings mins...the
temps are running 20 to 25 degrees above normal. But tonight is
when we will know if we have a near miss or not.
Forecast basis was a 50 50 blend of the 00z/24 GFS/NAM MOS, and
the 230 am wpc quantitative precipitation forecast which pretty much ends all rain except for
the E parts of NJ/de.
Long term /Wednesday through Monday/...
the last of the showers associated with the low/front from
Tuesday will be exiting off the coast Wed morning. Fair weather
and more seasonable temperatures are expected from Wed thru
Saturday. Temperatures on Thu will be a little below normal,
something that hasn't happened much this October.
Another trough will be developing across the plains and
deepening while heading towards our area. Another slow moving
front and low pressure moving along it offers the possibility
for more rains late this weekend and into Monday. We have slgt
ch pops for Sat night attm, in case the system arrives a bit
earlier, the trend is to make the system arrive a bit later, so
these pops may be removed later today. Temperatures will be near
normal Sunday, then again drop back below normal for the last
few days of the month. There is the possibility for some heavy
rains across the area, with the ample moisture that will be
arriving across the region. Pay attention to future forecasts
for more details.
Aviation /10z Tuesday through Saturday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Early this morning prior to 12z...gusty se winds 28-38 kt.
Isolated g 48kt possible. MVFR cigs with brief IFR conds in
showers spreading newd. Isolated tstm possible.
Today...variable conds from VFR to IFR in showers with isolated
tstms during the morning-midday. A tstm this morning or midday
may produce an isolated southerly wind gust to 45 to 50 kt but
for now the prob too low to mention in most taf locations. Low level wind shear
automatically added to the tafs this morning where algorithm
generated appropriate. Otherwise gusty se winds 28-38 kt 12-14z
diminish thereafter inland and become south to southwest during
the afternoon from west to east as conditions improve to VFR in
any remaining showers. Winds may stay strong at kacy til 17z.
Improvement in cigs/vsby may not reach Acy til about 21-23z.
Please see tafs for details.
Tonight...VFR except sub VFR vcnty kacy improving. However, IFR
conds in patchy fog may develop at the taf sites for a time
toward 06z/25. Light wind turning west to northwest.
Wednesday through Saturday...mainly VFR.
glw everywhere now with ending times from west to east this
afternoon. Then eventually back to Small Craft Advisory tonight, once the push
of gale force gusts subsides.
Glw for 2 to 4 hours of gusts 35-45kt between 08z-14z for Delaware
Bay and 09z-17z New Jersey and Delaware Atlantic coasts, possibly lingering nnj
coast til near 00z.
Tonight...a Small Craft Advisory will eventually replace the glw
for our ocean waters. We are expecting a south wind around 20
knots becoming west and diminishing around 10 knots. Gusts
around 30 knots are possible on Tuesday evening on our ocean
waters. Wave heights are anticipated to be 6 to 9 feet on our
ocean waters in the evening then slowly subside.
Wednesday through Thursday morning...a Small Craft Advisory
will continue on the ocean thru noon Thursday. Sct showers Wed
morning, then fair weather expected.
Thursday afternoon through Saturday night...no marine headlines
are anticipated. Fair weather thru Sat, then slgt chc for
showers Sat night.
hydro: storm total rainfall thru tonight, generally .5 to 1.5"
with in excess of 2 inches possible, most favored over New Jersey or Delaware.
Leaf-clogged drains will enhance the possibility of ponding of
water on roadways. New 06z/24 NAM does impressive redevelopment
this aftn in New Jersey.
vulnerable record high minimums today the 24th:
Allentown 58 1975
Atlantic City 63 2001
Philadelphia 63 1900
We will know on this by 05z/25...later tonight.
the shore areas of northeast Maryland will experience some minor
tidal flooding with the upcoming high tide. A coastal flood
advisory has been issued until noon today.
PA...Wind Advisory until 11 am EDT this morning for paz070-071-
Wind Advisory until 8 am EDT this morning for paz054-055-
New Jersey...Wind Advisory until 11 am EDT this morning for njz008>010-012-
Wind Advisory until 1 PM EDT this afternoon for njz013-014-
Wind Advisory until 8 am EDT this morning for njz001-007.
Delaware...Wind Advisory until 11 am EDT this morning for dez001.
Wind Advisory until 1 PM EDT this afternoon for dez002>004.
Maryland...Wind Advisory until 9 am EDT this morning for mdz008-012-015-
Coastal flood advisory until noon EDT today for mdz008-012-015-
Marine...Gale Warning until 7 PM EDT this evening for anz450>453.
Gale Warning until 4 PM EDT this afternoon for anz454-455.
Gale Warning until 2 PM EDT this afternoon for anz430-431.