textproduct: State College

WHAT HAS CHANGED

* Posted fog advisory for the NW * Lowered max temps significantly in the east for Friday

KEY MESSAGES

1) Periods of much-needed rain expected from Wednesday through the first weekend of March; wet pattern favored into next week with above-normal rainfall likely.

2) Significant springtime warming pattern ramps up from late week into the second week of March. However, temps may be lower than guidance on Friday, especially in eastern PA.

3) Fog is expected to get worse and expand into more of the CWA by sunrise.

DISCUSSION

KEY MESSAGE 1: Periods of much-needed rain expected from Wednesday through the first weekend of March; wet pattern favored into next week with above-normal rainfall likely.

On the heels of one of the driest winter seasons on record (see climate section), periods of much needed rainfall are expected from Wednesday through the first weekend of March. The wet pattern is favored to last into the second week of March based on the latest CPC 6-10/8-14 day precip outlooks. Surges of Pacific and Gulf moisture interacting with wavy or slow moving frontal zones is projected to deliver total rainfall amounts between 1 and 3 inches across CPA through next Monday.

KEY MESSAGE 2: Significant springtime warming pattern ramps up from late week into the second week of March. However, temps may be lower than guidance on Friday, especially in eastern PA.

Persistent and amplified Southeast U.S./Atlantic centered upper ridging will promote a significant springtime warming trend from late week into the second week of March. Fcst max and min temperatures will be 15-30 degrees above the historical average Sat-Tue and may challenge daily records. Fri is a big if on temps - mainly in the east. Deep easterly flow behind an expected backdoor (moving down from the NE) cold front could keep us much cooler than guidance. This has been a concern/forecast challenge for a few days, and after collaboration with our neighbors we've made a move to lower forecast max temps 4-6F over the east. We should get milder (hot) on Sat with good SWrly flow pushing the front back to the NE.

KEY MESSAGE 3: Fog is expected to get worse and expand into more of the CWA by sunrise.

Moisture is increasing while temps cool a bit overnight, and is an excellent setup for fog to get dense again by morning. The fog in the NW has already become dense, and HREF/HRRR/SREF progs all show a very high probability of low visibility. MAV/MET guidance also keep visby down at BFD thru 15Z. A little skeptical that the 1/4SM or less fog will last that long, but it's a certainty for the next 8 hrs at least. Later shift will probably have to expand the advy, but not enough confidence to post for anyone else just yet. They just improved a bit, anyway.

AVIATION /03Z WEDNESDAY THROUGH SUNDAY/

IFR/LIFR conditions are occurring across most of central Pennsylvania this evening, driven primarily by low cloud ceilings as mild, moist air moves over moist/cool air near the surface. LIFR cloud ceilings and IFR/LIFR visibilities due to fog are expected regionwide overnight.

Minimal improvements are expected at KJST tomorrow as a stout inversion and upsloping winds keep cloud ceilings low. Improvements to IFR are possible later in the morning at KAOO/KUNV/KMDT/KLNS as daylight could help to raise cloud ceilings through diurnal mixing, though continued moisture advection looks to prevent further improvements. Across the Northern Tier, airports such as KBFD and KIPT are expected to rebound to VFR by the afternoon as a brief shift to northwesterly flow aloft brings drier air overhead. Nevertheless, moisture advection will return later in the evening across northern PA, with clouds returning late in the day.

Otherwise, rain showers will taper off north-to-south during the overnight hours as dry mid-level air filters in from the north, with another round of rain showers possible across southern PA later tomorrow morning and into the afternoon. A PROB30 was added to KJST, KMDT, and KLNS during that timeframe to signal at this possibility, with timing determined by a blend of the HRRR, NAM 3km, and HREF. Rain showers are also possible at KAOO during that period, though lower certainty in timing and coverage precludes a PROB30 at this time.

Lastly, a 40 to 50 kt southwesterly LLJ is moving over Pennsylvania this evening, with LLWS mentions added at KJST, KAOO, and KUNV due to this jet.

Outlook...

Thu...Restrictions likely with widespread rain associated with a warm front.

Fri...Stationary front across the region. Restrictions possible, especially across central/eastern airfields.

Sat...Restrictions remain possible, especially in the north and east. VFR most likely from KJST south and west, where winds could get gusty in the warm sector. Afternoon/evening showers likely with cold FROPA.

Sun...Trending towards VFR.

CTP WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until 9 AM EST Wednesday for PAZ004-005.