Area forecast discussion National Weather Service State College PA 723 am EDT Thursday Jun 20 2013 Synopsis... an upper level ridge of high pressure will bring very warm and humid weather to central Pennsylvania through early next week. A few isolated showers and thunderstorms will be possible in the summertime pattern. A cold front pushing southward from the Great Lakes region should bring the next chance for widespread showers and thunderstorms by next Wednesday or Thursday. && Near term /through tonight/... a chilly morning is in progress across central PA...the result of high pressure and associated cool/dry air mass. 08z surface observation show some of the normally colder valleys have fallen to the l40s. As occurred yesterday am...expect the cool temperatures and relatively Warm River/stream waters to result in patchy valley fog in the deep valleys north of I-80. As surface high slips off the New Jersey coast...a return south-southeast flow should draw low level moisture northward along the east slopes of the Appalachians. The increased moisture should result in a fair amount of cumulus by afternoon across the central mountains the latest NAM/RUC and hi-res WRF depict isolated showers developing in vicinity of the Laurel mountains and S-central ridges within narrow axis of instability extending northward along The Spine of the central Appalachians. Although areal coverage probably doesn/T warrant an explicit mention in the forecast...will increase probability of precipitation to around 10 percent during the late afternoon and evening to account for possible isolated shra/tsra. Under pt-mosunny skies...temperatures today should be several degree warmer than Wednesday based on sref 800 mb temperatures warming around 2c. Given lack of any lg scale forcing...any isolated evening rain showers/thunderstorms and rain across the central counties should die out after sunset. For the rest of the night...only concern may be some patchy fog. Lightest wind and best potential of fog appears to be across the West Mountains && Short term /Friday through Saturday night/... an anomalous 500mb ridge will take up residence over the region during the short term period...downstream of a closed low rotating northeastward from the northern rockies into south-central Canada. This will mark the start of a very warm/humid stretch of weather for the local area - which is arriving on schedule with the official start of astronomical Summer on Friday /see climate section/. Appreciable rainfall will be hard to come by in this late-summertime pattern...with model data showing an almost daily chance of diurnal convection. Capping inversion/warm 700mb temperatures and overall lack of forcing should keep airmass convection to minimal covering. Consensus of model data focuses precipitation to the north of central PA - along west- east frontal zone located on the southern edge of the westerlies extending from the northern plains southeastward through the Great Lakes into the northeast states. Overall expect above normal Max/mins...little to no rainfall and some fog in the mornings. && Long term /Sunday through Wednesday/... the very warm and humid conds will continue from late in the weekend through early next week...along with the daily chance for afternoon shower or thunderstorm. Global model and ensemble data show the upper level ridge retrograding /movg westward/ into The Four Corners during the second half of next week. This should allow shortwave energy to enter the Great Lakes region and push a cold front southward across the region around day 7-8. The 20/00z gefs and ecens show a western ridge/eastern trough 500mb configuration heading into the second half of next week. && Aviation /11z Thursday through Monday/... low level moisture working into southern PA early this am...as high pressure passes off the New Jersey coast and winds shift to the south-southeast. Lns reporting a 400ft ceiling at 11z. However...strong June sun angle should cause low level moisture to mix out by around 13z based on latest near term model data. Elsewhere...patchy fog has developed in the Deep River valleys of the alleghenies. However...no airfields are likely to be affected. High pressure passing off the New Jersey coast should supply VFR conds and light winds to the area later today. However...can/T rule out an isolated PM thunderstorms and rain developing along The Spine of the Appalachians from jst and aoo north through unv. Outlook... Friday...patchy am fog possible West Mountains Sat...no sig weather expected. Sun-Mon...isolated PM thunderstorms and rain impacts possible. && Climate... astronomical Summer begins at 104 am EDT on Friday June 21st. && Ctp watches/warnings/advisories... none. && $$ Synopsis...steinbugl near term...steinbugl short term...steinbugl long term...steinbugl aviation...Fitzgerald climate...