Synopsis: The calm before the storms… Three waves will affect the region through Saturday night. The first wave will pass through the commonwealth on Wednesday, the second will push through on Thursday then finally the last one will affect the region on Saturday. The last two events look to be more of a wintry event, the last one still up in air, as the models are not in agreement.
Short-term: Looking at what the 15z GFS and NAM have to say and comparing it to current radar and metar data, the models are slow by 3 hours. Therefore we went with scattered showers during the day, as this quick system makes a drive through the region. Both models show precipitation increasing overnight, as the second wave makes its way up the Ohio River Valley. The low looks to be traveling south of the state. While this happens, the "540" line and the 0 degree 850 line will dive through the state. This will set up the chance of snow for Northern parts of the state. The SREF starts showing a 30% chance of snow for North Central by 15z, increases to 55% for 18z, and 100% for 21z and 0z. State College, Northern Susquehanna, and Northeast chances for snow increase by mid afternoon from around 30% to 100% for the evening. Then looking at snowfall probabilities from the SREF, it shows 100% for 1-4" of North Central for the afternoon and evening time frame, while the other three zones saw between 70 and 100% for the evening. Went with the following snowfall totals: North Central: up to 4", State College/NSQ/NE: up to 2".
Long-term: Friday will warm up to the 40's under mostly to partly sunny conditions, as we await the system to the south. A wave will be rolling through the Lower Mississippi Valley and Southeast, then will turn to the NE, as its shortwave becomes amplified by a trough becoming negative. This is where the uncertainty becomes very unclear. The EURO for the past several days, has this shortwave moving up the coast, having cyclogenesis occurring, and a big snowstorm will occur for the Central and Eastern PA. This solution has shifted a little to the east according to the 0z EURO run. While the polar opposite is the solution for the GFS. The GFS has been taking this storm right out to sea from the Southeast. But as of 0z the GFS has made a shift to the west, and now has a similar track (still east of the EURO). Going with more of a EURO solution as suggested by the HPC Model Diagnostic Discussion (http://www.hpc.ncep.noaa.gov/discussions/hpcdiscussions.php?disc=pmdhmd). Due to this, temperatures for Saturday are similar to EURO, still encompassing what the GFS has forecasted. This situation will likely change over the next several shifts, so this is still leaning on the side of caution that this could be a dud for Saturday. Sunday we clear out and mostly sunny skies rule the world.
Kept temperatures near previous shift, with the exception to NE and for Saturday.
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Tyler B. Roys
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