000 
fxus61 kphi 281445 
afdphi 


Area forecast discussion 
National Weather Service Mount Holly New Jersey 
1045 am EDT Fri Apr 28 2017 


Synopsis... 
a cold front will wash out as it moves to our south this 
morning. A backdoor cold front will move across the area 
Saturday into Saturday night. This front will remain near the 
Delmarva and southern New Jersey on Sunday, then return as a 
warm front on Sunday night. Another cold front is expected on 
Monday night as an area of low pressure moves into the Great 
Lakes region. This low will drift northeast through southeast 
Canada through Thursday, with a couple of weak surface troughs 
moving across the area Tuesday and Wednesday. An area of low 
pressure may affect the mid Atlantic region late next week. 


&& 


Near term /until 6 PM this evening/... 
few changes, other than a few temperature adjustments, needed 
to the ongoing forecast. Mostly sunny conditions expected and 
temperatures climbing into the low 80s. Readings near the shore 
may only climb into the mid/upper 70s. Winds will be mostly 5 to 
10 mph from the west or northwest. 


&& 


Short term /6 PM this evening through 6 am Saturday/... 
a few showers and thunderstorms may move in to portions of New Jersey 
and southeast PA as a surface trough digs south through the region as 
it is filling and weakening. Once again it looks like there 
should be some meager elevated instability - enough to support 
some thunderstorms across the region. 


Lows will likely be near the morning dew point temperatures - 
generally in the upper 50s to upper 60s. However, winds are 
expected to shift from south southeasterly to southwesterly 
after midnight. This subtle wind shift combined with increasing 
mid level clouds may be enough to inhibit any fog development 
overnight. 


&& 


Long term /Saturday through Thursday/... 
a backdoor cold front will move into the area on Saturday and 
sink southward through Saturday night. High temperatures 
Saturday could be quite warm, but will be highly dependent on 
how fast the front moves through the area. If it waits until the 
late afternoon or evening, temperatures will be able to warm 
quite significantly. However, if the front moves through 
quicker, high temperatures may not be as high as currently 
forecast. This would be more likely across portions of northeast 
Pennsylvania and northern New Jersey where the front may cross 
sooner. A couple of short wave/vorticity impulses are forecast 
to move across the area Saturday through Saturday night, so 
there will be a chance for isolated/scattered showers and 
thunderstorms. If enough instability builds on Saturday, a few 
storms could become strong with gusty winds. But there could be 
a strong enough cap to prevent much activity until late in the 
day or evening. 


The front will likely stall across the Delmarva and southern 
New Jersey during the day Sunday. With the front near the area, 
this could help create some additional lift to interact with any 
short wave/vorticity impulses that move across the area and 
create some scattered showers. Sunday's highs are forecast to be 
markedly cooler than Saturday, about 15 degrees cooler for many 
areas. 


The front will not stay stalled out for very long as it is 
expected to lift back northward as a warm front Sunday 
night/Monday morning. As the front lifts across the area, there 
will be a chance of showers Sunday night into Monday morning. 
Temperatures Monday will warm once again as we enter into the 
warm sector ahead of the approaching cold front and return flow 
sets up. There could also be some showers and thunderstorms 
developing during the day Monday ahead of the approaching cold 
front. 


However, the best chance for showers and thunderstorms is for 
Monday night as the cold front moves across the area. Being we 
should enter into the warm sector during the day, we should warm 
quite nicely, and in turn some instability should build ahead 
of the front. Therefore there will be a chance of thunderstorms 
Monday afternoon and Monday night. 


The front will move offshore by Tuesday morning, as an area of 
low pressure moves through the Great Lakes region. This low will 
drift through southeast Canada through Thursday, with a couple 
of weak surface troughs possibly moving across our area Tuesday 
and Wednesday. There is a slight chance of showers across 
northeast Pennsylvania and northern New Jersey during each day, 
but chances are low at this time. 


By Thursday into Friday, an area of low pressure is forecast to 
move up the East Coast and potentially bring a period of steady 
rainfall to the area. There is some timing and placement 
differences, which is typical this far out, but they do agree on 
Thursday into Friday as the likely period. 


&& 


Aviation /15z Friday through Tuesday/... 
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg, 
kmiv, kacy and surrounding areas. 


Shallow ground fog has developed at some of the taf sites 
(specifically kilg, kabe, kttn, and kpne). Given how shallow 
this fog is, do not expect it to last long, only through 12z or 
shortly thereafter. Once the fog dissipates, VFR conditions are 
expected through at least 06z. There is a chance for showers 
and thunderstorms, primarily after 06z tonight and primarily for 
kttn and kabe. MVFR conditions will be possible with any 
showers or thunderstorms. Additionally, some more fog may 
develop near 12z. 


Though the cold front hasn't passed through many of the taf 
sites yet, expect winds to be mostly northwesterly by 12z or 
shortly thereafter. Wind speeds at the surface are generally 
expected to be light through the taf period. Earlier low level 
wind shear has dissipated. 


Outlook... 
Saturday...becoming VFR during the morning, then a chance of 
showers during the afternoon. Conditions may temporarily be 
reduced with any showers. Gusty westerly winds 15-20 knots. 


Saturday night-Sunday night...low clouds and fog may develop 
overnight Saturday and continue into Sunday night leading to 
reduced conditions. Small chance of showers and thunderstorms. 
Conditions may temporarily be reduced with any showers. 


Monday...low conditions in the morning, becoming VFR during the 
day. A chance of showers thunderstorms during the day. Lower 
conditions possible during the day with any showers or storms, 
more likely lower conditions overnight. Gusty southwest winds 
around 25 knots. 


Monday night...MVFR ceilings possibly developing. Showers and 
thunderstorms likely overnight Monday could briefly lead to IFR 
conditions. 


Tuesday...VFR conditions. Gusty southwest-west winds 25-30 
knots. 


&& 


Marine... 
seas are slowly starting to drop near 5 feet. Once seas drop 
further this morning, winds and seas are expected to remain 
below Small Craft Advisory criteria through the remainder of today and tonight. 


Outlook... 
Saturday-Sunday night...seas may approach 5 feet at times, and 
winds may gust near 20 knots, but conditions expected to remain 
below advisory levels. 


Monday-Tuesday...winds likely to gust 25-30 knots, and seas 
likely to exceed 5 feet as well leading to Small Craft Advisory 
conditions. 


&& 


Climate... 
**record or number 2 warmest April on record expected** 


Presuming our forecast temps these last 4 days of April are 
accurate, we are assured of a top 2 warmest April on record in 
much of our forecast area. Sunday is probably the critical day 
for determining record or not. 


Below: April projected within the top April average temps, the 
normal for April and the period of record (por). 


This includes todays high and low temperatures through 4 PM. 




Phl normal 54.0 por 1874 


59.4 1994 
59.4 2017? Projected tied warmest ever 
58.5 1921 
58.4 2010 
57.9 1941 


Abe normal 49.9 por 1922 


56.8 projecting record 
56.4 1941 
54.7 1994 


Acy normal 51.7 por 1874 


57.2 projecting record 
56.3 2010 
56.1 2011 


&& 


Phi watches/warnings/advisories... 
PA...none. 
New Jersey...none. 
Delaware...none. 
Maryland...none. 
Marine...none. 


&& 


$$ 
Synopsis...Robertson 
near term...po 
short term...Johnson 



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