textproduct: State College

WHAT HAS CHANGED

* Minor changes to the previous fcst.

KEY MESSAGES

1) More storms expected for central PA Sunday afternoon and evening. Some likely severe.

2) Rare, SPC Day 6 outlook for SVR TSRA potential across much of PA on Thu 6/18

DISCUSSION

KEY MESSAGE 1: 1) More storms expected for central PA Sunday afternoon and evening. Some likely severe.

AFter a fair and dry day and night, the air will get muggier on Sunday, especially in the Lower Susq. Dewpoints 65-70F are expected by mid-afternoon. Upper trough crossing the Great Lakes will drive strong forcing across during the peak heating and early evening. SPC outlook for Sunday paints a risk of tornadoes across the SE, where hodographs are slightly curved and helicity exceeds 200. CAPE at LNS is not all that fat, but nears 1100J/kg in the mid-aftn with deep layer (0-6km) shear of 40KT. LCLs are low there, too. But, the rest of the CWA will probably realized less CAPE due to lower dewpoints. UNV CAPE almost non- existent, but shear just slightly higher. BFD has a significant cap overhead until mid-aftn, but the lift from the nearing front and falling heights work. Thus, there could be two areas of convection develop simultaneously (W and SE), then the western convection should slide east and impact some of the central zones. However, the instability does look limited in the central zones. SPC SLGT risk of svr tstms covers most of the CWA and the WPC ERO MRGL risk are also touches the wrn mtns. Some convection should hang on after sunset until a cold front pushes through (00Z NW - 04Z SE), but it should be out of the CWA around 11 PM. The main action will be out ahead of the front during peak heating.

KEY MESSAGE 2: Rare, SPC Day 6 outlook for SVR TSRA potential across much of PA on Thu 6/18

The nose of a very strong, 40+ KT swrly 850 mb jet 50+ KT at 700 mb (both being 3+ sigma on the standardized anomaly scale), the the right entrance region of a 100 KT 250 mb jet and PWATS around 1.5 inches (with the potential of a EML surging in from the west ahead of a strong sfc cold front) will bring the ideal synoptic setup for a severe weather outbreak here in the CWA. As always, even with the moisture, instability and shear present, such strong forcing could produces plenty of clouds and early day convection to stabilize the atmos and decrease the potential for significant afternoon severe weather. We'll be monitoring this potential closely as we head into the start of the new week.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Good VFR under almost clear skies and resonably light winds this afternoon under high pressure. However, an approaching cold front will usher in nominal mid to upper level clouds overnight, with preciptaiton possible in the far western airfields at the tail end of this forecast period.

High resolution short term models indicate a veil of higher clouds during the late evening which will result from upper level winds blowing the tops of midwest storms into our area. Expect a lowering of this cloud deck through the morning as precipitation marches eastward into northwest PA.

Showers and possibly -TSRA should arrive in KBFD around noon time - dropping conditions to MVFR. The majority of the precipitation will hold off for the remainder of the airfields until after this forecast period ends. An isolated shower is possible at KJST and KAOO however.

Outlook...

Sunday afternoon...MVFR to IFR in TSRA which may have significant wind gusts as a cold front passes.

Monday...Mostly VFR with isolated -SHRA possible.

Tuesday...Mostly VFR with isolated -SHRA/-TSRA possible.

Wednesday...-SHRA/-TSRA chances increase ahead of low pressure system.

CLIMATE

The high temperature on Friday at Harrisburg reached 94 degrees. This broke the old record of 92 degrees, last set in 2017.

CTP WATCHES/WARNINGS/ADVISORIES

None.