textproduct: State College

SYNOPSIS

A cold front will push through Central Pennsylvania today before stalling out of just south of the region late this week. A wave on the stalled front is likely to lift up the Ohio Valley and across Pennsylvania this weekend.

NEAR TERM /UNTIL 6 AM THIS MORNING/

Breezy and mild conditions prevailing overnight in the warm sector ahead of approaching cold front and active convection over the Ohio Valley early this morning. South-southeast winds are gusting 15-20kts in most locations as a deep surface low moves into the Ohio Valley. Winds will stay gusty overnight and through the day Thursday as a tight surface pressure gradient and 60-70kt LLVL jet crosses the region through 12z.

Potent line of storms over Ohio will slowly weaken as it moves into western PA before sunrise, and will watch their intensity closely as they approach our western zones. Expecting the line to weaken by the time it moves into the Alleghenies, but a few strong gusts may be possible over our western zones before sunrise, with small hail possible as well, before storms weaken.

Stability remains high over the east while llvl moisture from persistent southeast flow results in plenty of low clouds and fog blanketing the ridges. Some patchy DZ is also expected. Temps will remain steady or slowly rise through dawn, rising into the 50s almost everywhere and near 60F in the Laurels at sunrise.

SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY NIGHT/

The low pressure center with this storm will be around the srn tip of James Bay in mid-day, with a trailing cold front pushing into the NW in late AM (before noon). The showers/storms in the morning could still pack a punch, but the prob for SVR wind/hail is low. The low crud over the east will start to clear out, but likely be stubborn to leave. The stability will again thwart the chc for deep convection for much of the area during the daylight hours. However, the disorganized look to the convection in the aftn on the HREF guidance may be because of the wide spread in the members on where and when to pop convection and when the front moves in/thru. Will keep mentions of SHRA and TSRA in the forecast for all day in the south, but the nrn tier should stabilize as the front presses south in the aftn. A large cap is evident over the srn tier in the aftn up around 7-8kft, so it'll have to be strong forcing to overcome it. The front could do it.

Highest PoPs will come later Thursday night after the cold front has pushed into MD and perhaps into nrn VA. The overrunning will also have good/steep lapse rates and instability aloft over our srn tier. SPC SLGT risk SVR on Day2 is still painted over our srn half, probably more so for the daylight hours Thurs than the late night (early Fri AM). But, the cap and initial stability at the sfc are two negatives. Could be a similar situation to what we experienced earlier this week as storms failed to intensify anywhere except the far southern tier of PA.

Temps will get into the 70s for many places on Thursday, as 8H temps get into the mid teens C in the morning, even if they slide a little in the aftn. Clouds will hinder temperatures somewhat, but a gusty southwest wind should be effective at helping temperatures rebound well on Thursday afternoon. A big range will be found for mins Thurs night, near 40F N and upper 50s SE.

Latest EPS/GEFS indicate cooler and drier weather is likely Friday/Friday night across most of CPA as sfc high pressure migrates eastward from the Great Lakes through northern New England. The most likely area for rain on Friday is over the southern tier of CPA particularly the southwest mtns/Laurel Highlands on the eastern edge of the deep moisture plume extending eastward from the Ohio Valley and in close proximity to the wavy/pivoting q-stnry frontal zone near or just south of the MD line. Highs on Friday will generally be in the mid 50s to mid 60s with cloudy skies south and perhaps a few breaks in the clouds across the northern tier.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Waves of low pressure riding east/northeast along the stalled to lifting frontal boundary will result in periods of soaking rainfall (with some embedded convective elements) this weekend. Latest WPC/NBM QPF fcst projects the heaviest rain (0.50-1.50") over the western and northern Alleghenies with <=0.50" across the south central ridges into the lower Susquehanna Valley (where it is needed the most).

There is a broad consensus among the medium range operational and ensemble guidance that the primary cold front slides to the east of the area early next week as a strong surface high moves into the Central US and finally puts an end to the onslaught of rain across the Mississippi and Ohio Valleys. After the cold front sweeps through, anomalous upper level troughing will build into the northern Mid Atlantic and Northeast states next Monday- Wednesday. This pattern will be accompanied by high confidence in below normal temperatures and blustery conditions. The colder cyclonic/NW flow should also favor scattered rain/snow showers downwind of Lake Erie over the Allegheny Plateau.

There are some long range model signals that suggest upper level troughing will reload (with potential for a closed low to move deep into the southeast US) into the second half of next week. This pattern would favor a continuation of temps below the historical average for the second week of April. There may also be an opportunity for frost/freeze conditions as the spring growing season gets underway in the Lower Susquehanna Valley.

AVIATION /05Z THURSDAY THROUGH MONDAY/

A few rain showers continue to linger across the area as of the beginning of the 00Z TAF package. These showers should move out of the region within the next few hours. The resulting south- southeasterly flow will lead to increasing low- level moisture over much of Central PA. This will cause MVFR ceilings to develop almost everywhere tonight, with the potential exception of JST. RAP model soundings suggest that the low clouds would make it there, but the GLAMP and HREF show a less than 40% chance of MVFR ceilings developing. Given the uncertainty at that site we kept site borderline VFR overnight.

The other concern tonight will be LLWS as a 45 to 55 knot low- level jet moves in and surface wind gusts decrease. BFD will be the first airfield to see wind shear develop and the threat will spread southeastward through the late evening. The potential for LLWS will reach MDT and LNS in the 06-08Z timeframe.

A decaying line of convection will reach the central PA area during the pre-dawn hours Thursday morning. Instability will be limited the further east these storms move, however sites in the west such as JST/AOO/BFD could see damaging wind gusts and rumbles of thunder. As these storms reach eastern PA by late morning they'll likely be light or nothing more than drizzle. Reductions in visibility will still be possible over MDT and LNS. Latest HREF shows a break in precipitation before another round of convection initiates across the southern half of PA with the passage of the cold front. Guidance still is showing a wide spread of solutions as to the exact timing convection will initiate come Thursday afternoon.

Outlook...

Thu...MVFR poss in widespread rain showers. TSRA poss, mainly S. CFROPA aftn/eve.

Fri...MVFR cigs and visby expected, mainly S.

Sat...Widespread showers; impacts likely.

Sun...Widespread showers; impacts likely.

CTP WATCHES/WARNINGS/ADVISORIES

None.