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000 
FXUS61 KPHI 270145
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
945 PM EDT Thu Apr 26 2018

.SYNOPSIS...
An area of low pressure will move northward across the Mid 
Atlantic region Friday, before combining with another low as it 
moves across New England Saturday. A cold front is expected 
Saturday, with additional surface troughs Sunday into Monday. 
High pressure across the Great Lakes and Ohio Valley Sunday will
build to our south Monday, before shifting offshore of the 
Carolinas Monday night where it remains through Wednesday of 
next week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...

As of mid/late evening, an upper low continues to progress
eastward across the southern Appalachians. High to mid-level
clouds and moisture are spreading rapidly northeast ahead of it
over the mid-Atlantic region. However precip remains well to our
southwest over SW VA, and is not expected to reach upper
Delmarva until near sunrise. Clouds overspreading the area
before that should limit overnight cooling, and so overnight
mins have been adjusted upward slightly for most areas.
Otherwise no changes to the current forecast. 

Previous discussion below:
Low pressure located in northern Maine early this afternoon 
will continue to move northeastward and away from our region. 
Weak high pressure will influence our weather tonight. Another 
area of low pressure approaching from the south is forecast to 
move into Virginia toward daybreak.

We are anticipating dry weather for the first half of the night
with just some cirrus overhead. The wind should become light 
and variable.

There will be an increase in mid level clouds from the 
southwest late tonight. Light rain is expected to reach 
northeastern Maryland, Delaware, and parts of southeastern 
Pennsylvania and southern New Jersey very late tonight.

Low temperatures in our region are forecast to range mainly 
from the middle 40s to the lower 50s.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
A mid level trough is forecast to lift northeastward over our 
region between about mid morning and mid afternoon. An area of 
rain is expected to precede the trough axis. We should see rain 
through most of the morning, with the rain tapering off in the 
afternoon from southwest to northeast. Most locations in our 
forecast area are expected to receive between a quarter and a 
half inch of rainfall.

The surface low is expected to progress slowly northeastward 
across the upper Delmarva and southern New Jersey on Friday. The
track makes for a tricky temperature forecast. We've averaged 
things out a bit. However, it is likely that some of our maximum
temperatures along and to the northwest of the Interstate 95 
Corridor may be a little high, and forecast readings may be a 
little low on parts of the coastal plain. We will adjust things 
when and if the trends in the track become more clear.

A light east to northeast wind is expected to develop on Friday
morning, with the wind becoming southerly to the east and south
of the surface low's center.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
After some possible showers this weekend, and extended period 
of dry weather is expected into next week, along with warming 
temperatures.

Low pressure that moves across the area during the day Friday 
will continue to lift to our north and while another low 
pressure moves across the Great Lakes. This low will move into 
New England through Saturday, pulling a cold front across the 
east coast before both lows combine into one. There will be a 
small chance of showers across the northern third of the area 
early Friday night, but most shower activity is expected to be
finished by evening time. The best chance of showers will be 
during the day Saturday as the aforementioned cold front moves 
across the area. The front will move offshore by Saturday 
evening and all associated showers will move offshore with the 
front, leaving a dry forecast overnight.

On Sunday high pressure will be moving across the Tennessee 
River Valley, before shifting across the southern Applachians 
and offshore of the Carolinas Monday. Meanwhile, low pressure 
will remain across northern New England and eastern Canada. This
will keep our area under the influence of a west to northwest 
flow, with a couple of weak surface troughs moving across the 
area. Most of the area will remain dry with the passage of the 
surface troughs. However, an area of enhanced low-mid level 
lapse rates and moisture will slide across the far northern 
parts of the area during each afternoon, which could lead to 
some isolated showers, mainly across northeast Pennsylvania and 
northern New Jersey. Gusty conditions could develop both Sunday 
and Monday with winds gusting 20-30 mph at times.

The high will remain to our south Tuesday into Wednesday, 
keeping dry conditions in the forecast. Winds could remain gusty
at times, but likely not as gusty as Sunday or Monday; 
generally 15-25 mph.

Late in the week a cold front may begin moving toward the area 
from the west. Right now it looks like the front will not make 
it into the area Thursday, keeping dry weather in the forecast. 
Friday looks like the earliest for it to reach our area.

After an up and down forecast to the temperatures Saturday and 
Sunday, a warming trend will begin Monday and continue through 
the upcoming week. Temperatures in the low to mid 80s are 
forecast for at Wednesday into Thursday.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, 
KILG, KMIV, KACY and surrounding areas.

Tonight...Mainly VFR with light rain arriving from the 
southwest between 09z and 12z. West wind 5 to 10 knots becoming 
light and variable.

Friday...Conditions dropping to MVFR and IFR in rain between 
12z and 15z. East to northeast wind 5 to 10 knots. Some 
improvement is possible late in the day.

OUTLOOK... 

Friday night...MVFR conditions possible early in the evening 
with scattered showers, becoming VFR later in the evening and 
overnight.

Saturday...Mostly VFR. A chance of showers which may 
temporarily lower conditions. 

Saturday night-Tuesday...VFR. Gusty west to northwest winds 
20-25 knots Sunday and Monday. Gusty west to southwest winds 
15-20 knots Tuesday.

&&

.MARINE...
Weak high pressure is forecast to influence our weather tonight
and weak low pressure should pass across our region from 
southwest to northeast on Friday. Wind speeds are expected to 
remain less than 15 knots with gusts not exceeding 20 knots.

A southeasterly swell is anticipated to continue along the 
coast. Wave heights on our ocean waters are forecast to favor 
the 4 to 6 foot range. As a result, the Small Craft Advisory has
been extended for our ocean waters to include both tonight and 
Friday. It has been changed to a Small Craft Advisory for 
Hazardous Seas since wind gusts of 25 knots or greater seem 
unlikely.

OUTLOOK... 

Friday night...Elevated seas may linger into Friday night.

Saturday-Saturday night...Conditions expected to remain below 
advisory levels. 

Sunday-Monday...Winds may approach Small Craft Advisory levels 
on Sunday.

Monday night-Tuesday...Conditions expected to remain below 
advisory levels.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory for hazardous seas until 6 PM EDT Friday 
     for ANZ450>455.

&&

$$
Synopsis...Robertson
Near Term...AMC/Iovino

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