textproduct: State College

WHAT HAS CHANGED

* Near-term temperature and dew point adjustments. * Conditional threat for tornadoes expanded to cover all of south-central Pennsylvania.

KEY MESSAGES

1) Spring-like conditions continues through Wednesday.

2) Numerous showers and scattered thunderstorms tomorrow. Some storms may be severe with damaging winds along with the possibility of a few tornadoes.

3) Settling into a cooler and windy pattern for the end of the week and weekend.

DISCUSSION

KEY MESSAGE 1: Spring-like conditions continues through Wednesday.

As heights continue to build over the eastern US into Wednesday, temps in central PA may challenge daily records as they surge +20-30 degrees above the historical average. With highs in the upper 60s-70s and lows in the 50s (Tue night), it will feel more like an average day in mid-May than mid-March. Record-breaking temperatures on Tuesday have already been observed as of 3PM across the region, with more information on those records coming with the 5PM evening climate report. Recent forecast continues to outline record-breaking warmth potential tonight and for high temperatures on Wednesday. See the climate section for more information on possible records.

New...

A few showers formed on the higher elevations across the southeast late this afternoon, given the intense heating and the lee side trough. Winds at the office from the north and light now, given this feature. Activity should weaken as the sun sets.

Earlier info. below.

Isolated to scattered showers/thundershowers are possible this afternoon and evening during the peak of diurnal heating, with increased sfc moisture and modest lapse rates aloft creating just enough instability for convection. Showers across NW PA have already been observed with better instability/shear slightly north of the border; however, cannot rule out showers/thunderstorms in the near-term across Warren/McKean counties. Focus for shower activity this evening shifts closer to the central-third of the forecast area, based on recent HREF model guidance.

KEY MESSAGE 2: Numerous showers and scattered thunderstorms tomorrow. Some storms may be severe with damaging winds along with the possibility of a few tornadoes.

A cold front will sweep through Wednesday night into Thursday, as an upper trough approaches the region. Ahead of the front, numerous showers and some thunderstorms are anticipated during the daytime and evening on Wednesday. The SPC Day 2 (Wednesday) Slight Risk area continues to include practically all of central PA with minor changes to the afternoon update today, with changes limited to expanding the CIG1 hatching across the southern tier of Pennsylvania (see more below). The main uncertainty with respect to this threat continues to be instability with recent HREF model guidance indicating considerable cloudiness across much of the area (maybe SE PA sneaks out a couple breaks early) by sunrise Wednesday. Recent model guidance does continue to like the idea of some shower activity in the morning hours, which could further limit instability for the afternoon/evening hours. Probabilities of SBCAPE exceeding 500 J/kg in the most recent HREF have decreased some with recent guidance indicating a second corridor along I-81 and extending closer to the Harrisburg area; however, probabilities have even dropped in this corridor as well.

With winds of 40-50 kts in the lowest 3km of the atmosphere, it wouldn't take much to bring some damaging winds down the ground. In contrast with the system over this past weekend, there will be more shower activity during the day on Wednesday but also a more moist airmass in place before storms arrive, and no cool air damming signal over east central PA. Given the very strong low-level winds and Gulf moisture connection, the resultant 850 mb moisture flux is progged to be about as strong as it can be this time of year across western PA.

While damaging straight line winds will be the primary threat with Wednesday's convection, the SPC D2 outlook also includes CIG1 hatching over much of southern Pennsylvania, meaning the conditional probability of an EF2 tornado is greater than the climatological average. In other words, if tornadoes do develop in that area on Wed, they could be strong.

KEY MESSAGE 3: Settling into a cooler and windy pattern for the end of the week and weekend.

As the base of the trough and associated surface cold front cross PA, a sharp temperature drop in the wake of the cold front may result in any lingering postfrontal precip changing over to snow Wed night into Thu. Gusty winds will also accompany the system, with gusts of 30-40 kts behind the front early Thursday.

Trending toward the longwave pattern that we saw most of the winter, with cooler conditions on the east coast. Weather systems will be moving fast so a lot of day to day variation likely.

Periodic shortwaves in the prevailing upper level pattern will lead to chances for precipitation as well as strong winds every few days from this weekend into early next week. At this point, the storm track favors the primary corridor of precipitation passing north of the area. With overnight lows within a few degrees of the freezing mark forecasted, precipitation type will be largely dependent on what time of day it moves through. But as of this time, no significant systems or appreciable precipitation are expected.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

As noted above, a few showers formed late this afternoon across the higher elevations west of the MDT area, as intense heating help with the lee trough formation.

One change to the 00Z TAF package was to take out the late night activity, as we will be south of the warm front, and time of day.

The main change was to slow down the afternoon convection to later in the day, and add a tempo group for thunder and strong winds across the western sites toward late afternoon.

Turning colder by Thursday morning, some chance of snow showers across the mountains.

Outlook...

Thu-Fri...Windy and colder. Scattered rain and snow showers, with restrictions possible.

Sat...Remaining brisk, with restrictions in rain and snow showers most likely at KBFD and KJST.

Sun...Rain and snow showers possible across the northern half of PA. Restrictions possible.

CLIMATE

As of 530 PM, some new reccords.

Altoona temperature estimated at 75 for the high today, old record of 72 degrees set in 1986.

Bradford high of 70 broke the old record of 66 degrees set in 1986.

Williamsport high of 77 broke the old record of 71 degrees set in 1977.

Harrisburg high of 80 broke the old record of 79 degrees set in 2016.

Earlier info. below.

Near-record warmth is expected Tuesday into Wednesday across Pennsylvania with highs in the 60s & 70s and lows in the 50s.

RECORD TEMPERATURES TUE 3/10 WED 3/11 MAX T MIN T MAX T Altoona 72 (1986) 49 (1990) 74 (2025) Bradford 66 (1986) 49 (2021) 66 (2025) Harrisburg 79 (2016) 49 (1955) 76 (2021) State College 76 (2016) 52 (2016) 72 (1986) Williamsport 71 (1977) 50 (1898) 75 (2025)

CTP WATCHES/WARNINGS/ADVISORIES

None.