textproduct: State College

SYNOPSIS

A ridge of high pressure extending from near Montreal south through the Susquehanna Valley will maintain dry weather with light wind today into Friday,

Light rain will spread into the state from the west Friday night and periods of rain of varying intensity will follow for Saturday and Sunday.

The rain could start as some light freezing rain early Saturday throughout portions of the Central and Northern Mountains and to a lesser degree across the Middle Susquehanna Valley.

NEAR TERM /UNTIL 6 PM THIS EVENING/

A minor uptick in Northwest winds 3-5 kft AGL in the wake of a weak trough and beneath the thermally direct subsiding branch (left entrance region) of a 65 KT east/west jet max just south of the Mason/Dixon Line was helping to erode the persistent and quite extensive stratus/stratocu deck across Southern PA.

Loop of Nighttime Microphysics Imagery show that the southern edge of this cloud area has drifted north to near the RT 22/322 corridor in Scent PA at 0930Z. Expect this northward erosion of the cloud to continue through the mid morning hours (with some sunshine likely across Scent PA between 13-17z before a higher based strato cu area drifts NE over that part of the Fcst Area and winds/Vertical Mixing in the BLYR weakens this afternoon.

Per the latest HREF and NBM guidance, cloud cover should slowly decrease across the far East and far Western parts if the CWA this afternoon, but likely stay at least BKN in coverage across Much of the Central third of the state through this afternoon.

There won't be much of a range in high temperatures today, mainly upper 30s to lower 40s.

SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/

Tonight could be a few to several degrees cooler than recent nights should we get some significant gaps of clearing for several hours tonight. The ridge of high pressure from the Champlain Valley to Eastern PA will drift slowly to the east, bringing the greatest chance for clearing to the east of the Susq Valley and also near and to the west of the RT 219 corridor.

Min temps early Friday will be similar or a few deg F lower than today (Thursday). Lows will range from the Upper teens (across the Mtns North and East of KIPT, to the mid and upper 20s across the SW 1/2 of the CWA.

Friday looks dry, with similar high temperatures to Thursday.

The leading edge of the showers move into the region by Saturday morning.

There is a low probability for a bit of light freezing rain early Saturday, mainly north and east of the office here. Will cover this nuisance potential via the Hazardous Weather Outlook and Social Media.

LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/

PoPs trend higher again Sat night into Sun as a deeper low moves up towards the Great Lakes. This disturbance will have ample moisture, with the bulk of model guidance outlining PWATs in the 1.00-1.50" range on Sunday. By ways of sounding climatology at KPIT for December 29th, this will push PWAT values closer to the 90% percentile for this time of year. Roughly 50% of NBM members bring more than 1.50" of rain to the eastern half of PA in the Sun-Mon timeframe. WPC does highlight central and eastern PA with a Marginal Risk (level 1/4) for Excessive Rainfall, but overall this will be a beneficial rain especially for parts of eastern PA still impacted by severe (D2) drought.

A brief period of dry conditions is noted in the ensemble plumes across portions of the Susquehanna Valley region later Monday evening and into Tuesday morning before a developing East Coast low brings an influx of moisture and renewed chances for rainfall area wide late Tuesday into Wednesday. There remains some uncertainty in this timeframe, so have stuck closer to NBM model guidance for this forecast cycle, with PoPs highest Tue night into Wed. At this time rain looks like the dominant ptype, but snow could mix in across the north.

Temperatures throughout the long-term period will be well above climatological averages, with MaxTs peaking 15-20F above average on Sunday. Cloud cover continuing throughout the overnight hours will also promote MinTs well above climatological averages with MinTs by Sunday morning and Monday morning ~20F above average with some locations approaching records for highest MinTs based on the current forecast. MinTs will remain well above average Tuesday and Wednesday mornings, trending 10-15F above climatological averages.

AVIATION /11Z THURSDAY THROUGH MONDAY/

Low stratus have stubbornly stuck around through much of the evening. Anywhere that has not seen the cloud deck clear is still in MVFR and will remain under low CIGs until the stratus deck clears out later today. Elsewhere VFR conditions will remain predominant across the region.

Gradual improvement is expecting at all airfields during the daylight hours on Thursday. Central and western TAF sites will likely be last to transition to VFR, between 14-18z. Winds will remain light and variable with high pressure overhead.

Outlook...

Thu...No sig wx.

Fri...Rain moves into western PA late evening.

Sat-Sun...Rain continues moving in from the west and continues into Sunday with areas of low cigs and LLWS likely.

Mon...Rain chances decrease west-to-east late with lingering rain possible.

CLIMATE

Climatology of State College, PA is for just 25% chc of 1+" of snow to be on the ground Christmas morning (the common measure of a "White Christmas").

CTP WATCHES/WARNINGS/ADVISORIES

None.