516
FXUS61 KCTP 171835
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
235 PM EDT Wed Jul 17 2024

.SYNOPSIS...
- A cold front will push through the state through tonight
  accompanied by another round of strong to severe thunderstorms
  that will be focused across Central and Eastern Pennsylvania.

 - High pressure will build in from the Great Lakes on Thursday
   and bring mainly fair weather with seasonable temperatures
   through the end of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Surface cold front pushing southeast from the Northwest
Mountains early this afternoon with numerous showers, isolated
thunder and bands of heavy downpours. So far, rafl staying
within the beneficial category, and is moving into areas that
desperately need the rain farther south.

Severe threat is focused over my extreme southeast counties at
mid afternoon where surface heating has primed the area and
convective temps were reached after 1 PM. Greatest chance for
severe weather is in the form of strong to locally damaging
straight line winds given very straight line hodographs,
moderate values of CAPE, and fairly weak LLVL speed shear.
DCAPE is a third lower than what we saw yesterday
afternoon/evening, but is still maximized over our southeast
counties. A MRGL outlook remains over the rest of central PA as
the front drops slowly southeastward through this evening, but
the expectation is for locally heavy rainfall to be the main
sensible wx concern, and is a welcome one for most.

Right entrance region of 110 kt upper jet stretched from NW
Ohio to Southern Quebec late this afternoon may still support a
few stronger storms across central and southeast parts of the
area, but again the focus seems to be more on hydro at this time
and relatively high FFG values for most (slightly lower over
parts of Adams/York/Lancaster which saw heavy downpours
Tuesday). PWs of nearly 2" in the SE could help feed very heavy
downpours, but fast storm motions and the high FFG (widespread
4.5"/3 hrs values) keep the threat for flash flooding low. The
MRGL risk in the Day2 ERO was collaborated with WPC, mainly in
order to keep continuity with previous forecasts.

The Heat Advisory for our SE zones remains in effect through
00z Thu with temps starting the day in the mid to upper 70s.
the lack of clouds through the overnight hours has led to some
patchy valley fog, but lack of rainfall today will be a tick in
the negative column.

The cold front slides through all but perhaps a few towns on
the MD border by 03-04Z Thursday. Thus, the SHRA should press
mainly or entirely to the S of the border well before sunrise.

Falling dewpoints should lead to a lower threat of fog, but the
temps drop right along with them. Will keep the mention of fog
from the wx grids at this point.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Thursday will mark the start of the beginning of a stretch of
fair and seasonable weather with lower humidity during the day
Thursday and all of Friday as high pressure builds from the
Great Lakes.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
On Saturday, there could still be enough moisture working into
the state from the south that a shower or two could develop over
the SE and/or ridge-and-valley region if the ridge tops can help
nudge the moisture high enough. It`s only worth a 20pct chc at
this point based both on coverage and probability. This is the
only mar in an otherwise stellar weekend forecast.

During the early part of the new week, the humidity levels will
creep back up as the deep upper low over ern Canada slides a
little more to the east and the Bermuda High pushes moisture
farther to the north and into the state. The stationary
boundary to our south may struggle to move northward, so we`ll
keep the increase in precip chances slow for the time being.

Overall, we will see muggy nights again by mid week and a
gradual increase in cloud cover and PoPs. By Wed, PoPs get close
to 70pct. Confidence is higher than normal in the extended
pattern. Of course, confidence is lower on the day- to- day
details. But, normal diurnal trends in convection have been
leaned on for most of the long range.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
MVFR cigs cover northwest and central PA at mid afternoon, and
are overspreading southeastern airfields this afternoon with sct
to nmrs rainshowers and isold ts. Afternoon showers and
thunderstorms will become more numerous and last into the
evening along and ahead of a cold front slowly pushing southeast
from the Great Lakes. Storms should decrease in coverage and
exit/dissipate over the south/eastern airspace between 03-06Z.
There is decent model signal for post- frontal upslope low MVFR
cigs particularly at KJST and potential IFR fog impacts at
KBFD/KIPT late tonight into early Thursday morning.

Outlook...

Thu...MVFR cigs psbl northwest 1/2; low VFR elsewhere.

Fri-Sun...AM valley fog. Otherwise, no sig wx/VFR.

&&

.CLIMATE...
The max temperature hit 100 degrees at Harrisburg yesterday
7/16. The last time KMDT hit 100 was back on July 19, 2020.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT this evening for PAZ036-056-057-
059-063>066.

&&

$$

SYNOPSIS...Lambert/DeVoir/Bowen
NEAR TERM...Lambert/DeVoir/Bowen
SHORT TERM...DeVoir/Dangelo/Bowen
LONG TERM...Dangelo
AVIATION...DeVoir
CLIMATE...Steinbugl