textproduct: State College

WHAT HAS CHANGED

Minor changes changes to the cloud cover forecast for the rest of the day.

KEY MESSAGES

1) Pleasant/dry pattern with comfortably low daytime humidity will last through today before humidity gradually climbs on Sunday.

2) Turning more humid and unsettled early next week with the highest probability for showers and thunderstorms Monday afternoon and evening and again on Tuesday.

DISCUSSION

KEY MESSAGE 1: Pleasant/dry pattern with comfortably low daytime humidity will last through today before humidity gradually climbs on Sunday.

Broad, low-level streamline convergence with its N/S axis near the RT 219 corridor in Western PA was leading to an expanding area of Strato Cu clouds based mainly between 3-4.5 kft agl. A few light showers have also been observed in this area this morning.

As upper level diffluence slightly increases from the west this afternoon and a few embedded flat shortwaves move overhead, there will be isolated to scattered showers with MU CAPE only 500 J/kg or less. Will leave the isolated afternoon TSRA in for now to the west of RT 219, but would be surprised to see any in that part of our CWA based on the amount of morning cloud cover and TDs still only in the 50s to around 60F.

Surface convergence becomes more focused over the eastern half of the forecast area for tomorrow. Slightly higher dew points will allow for instability to be a little higher than it is today, possibly approaching 1000 J/kg in a few locations. Though upper level forcing looks to be weak, we would expect to see at least a few showers and thunderstorms develop during the afternoon.

KEY MESSAGE 2: Turning more humid and unsettled early next week with the highest probability for showers and thunderstorms Monday afternoon and evening and again on Tuesday.

Minor modifications for this period that will be highlighted by a warm front moving across western PA Monday afternoon/evening, followed by a rather potent/digging mid/upper level shortwave, that will support a sub-995 mb sfc low over the Lower Glakes and Western NY Tuesday afternoon and evening. Latest model runs have trended several hours or so slower compared to runs 24 hours ago.

The timing of the favorable lift associated with the thermally indirect, left front quad of the 80+ KT jet max moving across the Ohio Valley, WVA and southern PA Tuesday afternoon and evening will help to enhance a low level lee trough and convection along it. Scattered strong to severe TSRA are likely Tue afternoon and evening over at least the eastern half of the CWA with a second line of TSRA likely along the cold front across NW PA Tuesday afternoon.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

An area of MVFR (cigs) sits over the western half of the state with a sharp dividing line right down the middle to SKC or FEW over the east. This inverted trough of moisture may result in an isolated -SHRA this afternoon, but little if any has shown up in a METAR as of yet. Left the mention of VCSH in the begining hours of the forecast for the elevated airfields across the western highlands.

This general trend continues into Sunday with a slight uptick in instability. This may result in an isolated -TSRA over the western half of the state again but coverage would be sparse.

Good VFR will last through the forecast period across the eastern half of the state, with VFR to MVFR in a transition from east to west. There is a lower than average confidence (10-20%) of patchy BR or FG overnight over the west and higher elevations. Hinted at this with a drop in non-restrictive clouds and visibility later tonight. Winds will remain at or below 5KTS through the period.

Outlook...

Mon-Wed...Restrictions likely in afternoon -SHRA /-TSRA.

CLIMATE

Cooler than average temperatures across the region led to multiple record low temperatures being broken for July 23rd and July 24th across central Pennsylvania.

On July 23rd:

* Altoona set a record low temperature of 47 degrees, breaking the previous record of 50 degrees set back in 1981.

* Bradford tied a record low temperature of 38 degrees which was previously set in 1981.

* Johnstown tied a record low temperature of 49 degrees which was previously set in 1983.

On July 24th:

* Altoona set a record low temperature of 47 degrees, breaking the previous record of 50 degrees set back in 1957.

* Bradford set a record low temperature of 41 degrees, breaking the previous record of 44 degrees set back in 1993.

CTP WATCHES/WARNINGS/ADVISORIES

None.