Area Forecast Discussion
Issued by NWS State College, PA

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301 FXUS61 KCTP 240107 AFDCTP Area Forecast Discussion National Weather Service State College PA 907 PM EDT Mon Oct 23 2017 .SYNOPSIS... A strong frontal system will push colder air into the region tonight into Tuesday. A second shot of cold air is expected this weekend. Overall most of the coming 6-8 days the region will be in a mean trough thus cooler weather will be the norm for awhile. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Regional radar at 00Z showing band of rain lifting into southwest Pa along axis of anomalous southerly low level jet/PWATs preceding potent shortwave lifting into the Grt Lks. Mesoscale guidance continues to indicate most of the rain will come with this north-south band during the late evening hours over the western half of the forecast area and during early Tuesday morning across the eastern half of the forecast area. Latest guidance indicates increasing low level instability late tonight ahead of vort max lifting north from Virginia in conjunction with 850 winds in the 60-70kt range. Noticed numerous severe wx warnings across southwest Virginia early this evening and suspect this threat of severe weather will lift into eastern Pa late tonight. Per collaboration with neighboring offices, have covered much of the region with a wind advisory late tonight. Bufkit soundings support gradient wgusts in the 20-30kt range, but any strong convective cores could easily bring 50 mph winds to the surface. The v-winds are about 4 to 5 sigma above normal ahead and along the frontal boundary. Most areas will have a good 1-3 hour window with the rain with ensemble mean QPF ranging between 0.5 and 1 inch. In the HRRR and the GEFS this has a classic NCFRB look so most of the rain will be close to the frontal boundary. Rapidly improving indicated across the western half of the forecast area late tonight behind the line with partial clearing. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... Improving day weatherwise as the front pushes farther to our east. After 15Z the GEFS has no QPF in our CWA. It will be a cold advection day with potential for some self- destruct cumulus in the mountains. Strong westerly winds at 850 hPa should easily mix down behind the front. So gusty winds likely. The coldest air does not filter in until Wednesday but Tuesday will be the start of a cooler period. Enjoy would could be one of the warmest day for some time to come. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... Surface ridging indicated over central Pa by med range guidance late Tuesday through Friday, indicating dry weather for most of the forecast area. The exception will be late Wed, when passage of shortwave could produce a few showers across the northwest mountains. Ensemble mean 925/850 temps are slightly below normal Wed/Thu, likely translating to max temps from the upper 40s over the Alleghenies, to the upper 50s across the southeast counties. This cooler stretch will be short lived as heights and 850 temps rise quickly into next weekend. Another chance for precipitation will arrive at the end of the period when a cold front is anticipated next Sunday, bringing rain to much of the CWA, while colder air and a few waves of low pressure riding NNW along the front brings the chance of a light to moderate, and elevation dependent snow event. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/... Rain streaming northward into Pennsylvania ahead of a strong cold front approaching from the west. Significant winds with low level jet forecast to strengthen over the region between now and 06z/08z...before shifting to the east. With 850 mb winds forecast to be in the 50 to 70 knot range overnight, and increasing instability, expect surface winds to regularly gust between 20 and 30 kt...and between 40 and 50 kts in the vicinity of the CFROPA. Could also see some isolated thunder in convection especially over southern and southeastern areas. These strong wind fields also introduce high potential for LLWS pre and during FROPA. Showers and rain will increase in coverage and intensity overnight, again peaking with the CFROPA. As mentioned previously, could see some isolated TSRA with the front. Windshift behind the front will be subtle...shifting from the SSE to the SSW. Most notable will likely be the noticeable drop off of strongest wind gusts behind the front. Ceilings will mainly be in the MVFR range overnight, but a narrower corridor of IFR ceilings expected to accompany the front. Visibilities may be restricted in areas of heavier rain, but should mainly remain in the VFR/MVFR range. Tuesday will be breezy behind the cold front, with improving conditions as the front swings east. More scattered showers developing in mountains in the afternoon. Conditions generally back to VFR after about 14-16Z. Outlook... Wed-Thu...Mainly VFR, but scattered showers and ceiling restrictions in the western and northern mountains. Fri...Mainly VFR. Fri Night-Sat...Another approaching cold front with chance of showers. && .CLIMATE... Through 10/22/17, the average monthly temperatures at Harrisburg and Williamsport are 63.8F and 61.8F. When compared to the maximum 1-month mean avg. temperature for previous Octobers, both would rank as the warmest on record. Computing a daily avg. temperature when only taking into account the first 22 days of the month and comparing to the previous Octobers, the rankings are #2 at IPT and #3 at MDT. && .CTP WATCHES/WARNINGS/ADVISORIES... Wind Advisory from 1 AM to 8 AM EDT Tuesday for PAZ028-036-037- 041-042-046-049>053-056>059-063>066. Wind Advisory until 4 AM EDT Tuesday for PAZ004>006-010>012- 017>019-026-027-035-045. && $$ SYNOPSIS...Fitzgerald/Lambert NEAR TERM...Fitzgerald SHORT TERM...Grumm LONG TERM...Lambert/Gartner AVIATION...Grumm/Jung CLIMATE...

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