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Central PA Spring 2025


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A little late but below is the April Climate Summary for Chester County. April finished 1.9 degrees above our normal average temperature which is our 27th warmest April since records began in 1893. The top 10 warmest are avg temp (year)
57.3 (1921) / 57.2 (2017)/ 56.7 (1941) / 56.5 (1915) / 55.8 (2019) / 55.7 (1945) / 55.5 (1942) / 55.5 (1910) / 55.4 (1960) and 55.4 (2023)
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It's worth reading fellows. I'm excited about today and tonight.  I hope last night is an indicator of where storms may start training today.  

Area Forecast Discussion
National Weather Service State College PA
501 AM EDT Mon May 5 2025

.SYNOPSIS...
* Slow moving, training showers and PM thunderstorms will lead
  to localized heavy rainfall of 1 to 2+ inches with the
  potential for small stream and poor drainage flooding in a few
  locations across Central Pennsylvania and the Western Mtns.
 *Becoming drier late in the week with a trend toward below
  normal temperatures.

&&

.NEAR TERM /THROUGH TONIGHT/...
A quasi-stnry front stretched about 25 NM either side of
Interstate 80 (along its entire length through PA) has helped
to strengthen several narrow bands of showers overnight as they
drifted NNW over the boundary that provided some enhanced MESO-B
lift.

As we head through the late morring and into the afternoon hours,
the focus for the most numerous bands of convection and threat
for heaviest rain and localized severe weather will be across
the approx SW 1/2 of the CWA today as 2 separate mid/upper level
jet maxes/lobes of differential vort lift north across the
Western and Central Mtns. Slightly lower probs for severe
weather and training heavy SHRA/TSRA exist across the Middle
Susq Valley and Endless Mtns region NE of KIPT.

The first of the aforementioned kinematic features aloft will be
the enhanced lift/focus for the initial TSRA beneath the right
entrance region of a upper level speed max stretched from KPIT
to KCLE late this morning through early this afternoon, followed
by a link with meso-B uvvel beneath the left exit region of
another southerly jet segment drifting north across VA and the
MD Panhandle toward evening.

A distinct channel of enhanced (deep and somewhat thin) CAPE of
1000-1500 J/KG will exist between RT 219 in the Western Mtns
and RT 15 north through the Susq Valley.

Later shifts will need to keep a close eye on the evolution of
convection and training cells within this part of the CWA (which
covered by WPC`s MRGL risk of excessive rain), as PWAT values
will be just under 1.5 inches coinciding with soundings that
indicate a deep, moist, warm cloud layer up through 11-13 kft
agl leading to highly efficient rainfall production. A short-
fused Flood Watch may need to be collaborated/issued at some
point later this morning/afternoon.

Max temps will display a small range today (only about 5-6 deg
F) from the upper 60s to low 70s. A few spots throughout Scent
PA could see a 74 or 75F this afternoon.

SPC maintains a MRGL risk for stronger updrafts containing 1
inch hail and locally damaging wind gusts. As noted by earlier
shifts, although not outlooked for tornadoes, a brief, weak
tornado can not be ruled out given the low LCLs and sufficient
veering/moderately strong llvl speed shear within the wind
profile at low levels.

Convection may be slow to wane tonight, with both the NAM and
HRRR showing potential for narrow swaths of 1-2" of rain falling
from mature convective lines and clusters in just the 12 hour
period from 00z-12z Tue.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
Active weather will likely continue Tuesday/Tuesday evening as
the core of the upper low moves into western PA. This will push
the highest instability and greatest chance for severe weather
east into the Lower Susquehanna Valley.

The threat for severe weather appears to decrease Wednesday as
the slow moving upper low gradually fills in and the center
moves across the Eastern Third of the state in the afternoon,
with precip likely coming to an end across the bulk of Central
PA by Wed evening.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
By the latter half of the week, the upper low will be replaced
by a fairly potent upper trough as high pressure builds in at
the surface. Much lower PWATs (0.25 - 0.75") will usher in a
stretch of cooler and less-rainy conditions for the weekend.
Cool temps aloft will keep a chance for diurnal showers in the
forecast each afternoon, but ensemble mean rainfall for the
period is less than a quarter inch across the whole area.

High pressure amidst a cooler airmass will support a risk for
frost Friday and Saturday morning, especially west of I-99 and
north of I-80. The growing season is currently active for only
the counties along/east of I-99 and along/south of I-80, but as
we approach the median date of the first freeze for much of the
Laurel Highlands and northwest mountains (May 11th),
Frost/Freeze products may be needed there later this week.

After the brief cool snap Thursday night through Friday night,
ensembles favor a return to near normal temperatures with highs
in the 60s to 70s and lows in the 40s to 50s
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 Hrrr seams wonky and super over doning today's convective evaluation by basically covering 90% of the state in thunderstorms,  but dose eventually get around late in its range to something that looks slightly realistic posted below.  It eventually brings the line along the Mason Dixon into CPA. When I looked at it a few hours ago, it had  the idea of traing storms from Lancaster to Warren County starting around 4:30.

Screenshot_20250505_071835_Chrome.jpg

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We are only marginal in terms of risk today but here's is spc take on today. 

...Central Appalachians and Mid-Atlantic...
   Recent surface observations reveal a residual front/marine boundary
   draped from eastern VA into the eastern Carolinas. East of this
   boundary, richer low-level moisture in the form of low to mid-60s
   dewpoints is noted extending northward into southeast PA. Aloft, an
   embedded shortwave orbiting around the primary upper low is noted
   over the mid-MS River Valley in recent water-vapor imagery. This
   feature is expected to pivot into the Mid-Atlantic and central
   Appalachians through the afternoon/evening and will be favorably
   timed with the diurnal heating cycle. The combination of cold
   temperatures aloft in proximity to the upper low and rich low-level
   moisture will limit capping and promote thunderstorm initiation
   along the boundary by early afternoon from the DelMarVa region into
   NC. Further to the northwest, lift ahead of the embedded shortwave
   combined with cold mid-level temperatures should promote
   thunderstorm development across WV and OH by late afternoon. Across
   both regions, 1000-1500 J/kg MLCAPE and elongated, nearly straight
   hodographs should promote organized cells capable of large hail and
   damaging winds. Similar thermodynamic and kinematic environments
   were observed yesterday across the region, and yielded isolated to
   scattered strong to severe thunderstorms, including a couple of
   supercells
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A gloomy start to the new work week with some drizzle and showers across the area. The European and GFS have around 0.50" of rain by Wednesday morning...but higher amounts are possible if we see some thunderstorms tomorrow afternoon. High temperatures will be close to normal in the upper 60's to low 70's. We turn much chillier by the end of the week as Friday highs may struggle to escape the 50's for higher spots in the area.

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Been following this thread for a week, arrived from sofla saturday in nyc and heading to Hawley,PA today...will post anything of interest later today and tomorrow.  2-3 inches of rain is very different here than 2-3 inches in sofla, we are in a drought(typical right before the rainy season starts, we are almost there) but even in the rainy season, 3 inches in an afternoon doesnt really move the needle. 

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1 hour ago, jlauderdal said:

Been following this thread for a week, arrived from sofla saturday in nyc and heading to Hawley,PA today...will post anything of interest later today and tomorrow.  2-3 inches of rain is very different here than 2-3 inches in sofla, we are in a drought(typical right before the rainy season starts, we are almost there) but even in the rainy season, 3 inches in an afternoon doesnt really move the needle. 

Enjoy your time in PA! 

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