textproduct: State College

WHAT HAS CHANGED

* Kept adding to the PoPs for the area N of rte 22 for the next several hours. * Bumped up sky and PoPs a little for Tues in the far N.

KEY MESSAGES

1) Upper level low pressure near Toronto Ontario early today will drift northeast and diminish its influence on our cool temps and occasionally showery conditions through the midweek period with a gradual warmup in temperatures Tuesday through Thursday.

2) Showers and thunderstorms return Wed night or Thursday as a cold front approaches from the west.

DISCUSSION

KEY MESSAGE 1: Upper level low pressure near Toronto Ontario early today will drift northeast and diminish its influence on our cool temps and occasionally showery conditions through the midweek period with a gradual warmup in temperatures Tuesday through Thursday.

Update 230 PM...

Have seen the forecast play out as advertised thus far. Main change in this time frame was to bump up the sky and PoPs (10 pct) for Tues, too - but only for the N. Best day for the entire CWA looks like Wed with high pressure sliding east. Did add fog in for Tues night/Wed AM.

Previous discussion...

Left exit region of an upper level jetlet rounding the base of the upper trough combined with a CFA and sfc reflection in the form of a weak trough has led to areas of showers advecting into South-Central PA and the Lower and Mid Susq Valley early today (and even a few low- topped TSRA a few hours ago near and to the North of KIPT).

Expect a fair amount of morning sunshine across the bulk of Central PA after this current, embedded shortwave trough exits to the east and NE later this morning. However, unseasonably cool temps aloft (850 temps mainly +8 to +9C today) will lead to the sunshine taking on a self destruct form with plenty of MDT CU/Thickening strato cu developing /advecting ESE from the NW Mtns twd the central ridge and valley region. The next compact shortwave and mid/upper level speed max will rotate through a bit further to the north today, focusing the vast majority of any showers near and to the north of the RT 6 corridor in northern PA.

As noted in previous discussions and based on current high res ensembles and its members, it's unlikely that any precip will get south of I-80, but there will be plenty of clouds. Some showers will linger into the night and possibly early Tuesday before drier air works in as the upper trough departs.

Vertical mixing depth increasing to 4-6 kft after 14Z today will lead to a quick increase in the West to West-Southwest breeze with moderate gusts into the upper teens at times. There will be nearly a 20 deg delta in max temps from North to South today, with reading struggling to reach 60F across the highest terrain near and north of RT 6, while the Lower Susq Valley sees afternoon highs in the mid to upper 70s. These high temps will be 10-13F below normal across the Northern Tier counties and just a few degrees below normal in the Lower Susq Valley.

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KEY MESSAGE 2: Showers and thunderstorms return Wed night or Thursday as a cold front approaches from the west.

Return flow around the high will bring more moisture up through the Mid-Atlantic and into the Susq Valley late Wed night. This will touch off a few showers. A cold front will be approaching from the west at the same time. Diurnal heating will combine with upper energy to kick off numerous SHRA/TSRA on Thursday. The front probably won't fully pass thru the CWA until Friday morning. So, Thursday night (Lunar Eclipse time) probably won't be clearing enough for much of the CWA to be able to see it well. The west has the best chance to do so, but confidence is low in sky cover at this range.

AVIATION /18Z MONDAY THROUGH SATURDAY/

An upper level low over southwestern Ontario will keep a cyclonic flow of cool air across the Great Lakes into Tuesday.

Much of the time will be dry with VFR conditions. However lower CIGS will occur from time to time, mainly at BFD, but also at other spots late tonight. MDT and LNS the two TAF sites that are not expected to have lower CIGS late tonight.

Main chance for a shower today and Tuesday will be at BFD.

Outlook...

Wed...Patchy morning fog, otherwise mainly VFR conditions.

Thu...Chance of showers and storms again, mainly later Thursday.

Fri...Still a slight chance of a shower.

Sat...Clearing.

CTP WATCHES/WARNINGS/ADVISORIES

None.