Area forecast discussion National Weather Service Buffalo New York 401 PM EDT Wednesday may 22 2013 Synopsis... a warm and humid airmass will remain in place through tonight with showers and thunderstorms forming. It will turn cooler tomorrow...and showers will become more widespread as a cold front passes through. A few of these showers may linger into early Friday...before drier air settles into the region for the weekend. && Near term /through Thursday/... this afternoon several clusters of showers and thunderstorms have blossomed just to our east...but over our region mainly clear skies prevail. This has allowed for temperatures to rise a few degrees warmer...and also increased the amount of instability. Visible satellite imagery shows a lake breeze off Lake Erie and with this southwest flow areas along the immediate Lake Shore and the Buffalo metropolitan area will likely remain dry through the afternoon hours. Inland some cumulus has blossomed this afternoon across wny and the north country. With the additional daytime instability we are still expecting showers and thunderstorms to Blossom this afternoon and evening. The greatest instability with lifted indice's of -7c and SBCAPE of 2500+ j/kg is over interior wny. The cumulus over wny is forming within this area of greatest instability will likely form showers and thunderstorms over The Finger lakes region and later the Eastern Lake Ontario region...where dewpoints are in the middle to upper 60s. Will highlight the highest probability of precipitation this late afternoon and this evening within this region. However thunderstorms are possible...especially on lake breeze and thunderstorm boundaries across the County Warning Area through the evening hours when additional convergent lift ahead of a 45 knot low level jet and moisture advection fuels showers and thunderstorms. With this...some storms could become severe with the unidirectional flow with damaging winds and hail the primary threat. Severe Thunderstorm Watch 212 will go through 11 PM tonight. For tonight as the low level moisture and lift ahead of the low level jet carries northward expect showers and thunderstorms to diminish through the early overnight...especially south of Lake Ontario. Lows tonight will remain in the 60s. For tomorrow an area of low pressure will lift north of Lake Ontario and drag a cold front across the western half of New York state. While instability will be less tomorrow additional lift along the cold front boundary should produce more widespread showers. Will mention thunder across The Finger lakes region where the greatest instability within the County Warning Area will be found...with sbcapes around 500 j/kg. Showers will likely continue after the cold front passage with the upper level cool pool still to the west. Cooler tomorrow with highs reaching the lower 70s. && Short term /Thursday night through Saturday night/... northern stream trough will be digging southeast through Ontario and the northern Great Lakes at the start of the period. Secondary cold front will be just off to our west Thursday evening...then pass across the area Thursday night. Widespread shower activity Thursday night and early Friday ahead of the front will taper off behind the frontal passage...with drier and much cooler air advecting into the region...as a broad and strong Canadian surface high builds southward through the Great Lakes and toward the East Coast. This will put an end to the precipitation threat for the beginning of the Holiday weekend. Mainly clear and cool conditions for Friday night and Saturday. Overnight lows Friday night falling into the middle 30s and lower 40s and highs Saturday in the lower to middle 60s. The gradient may stay up enough Friday night to keep the potential for frost to a minimum but a few locations may nudge toward the freezing mark. && Long term /Sunday through Wednesday/... cool Canadian high pressure will reside over the area through the period. This will result in a quiet weather pattern with no precipitation expected. The dry airmass in place will likely result in a wide diurnal range in temperatures. The coolest period looks to be Sunday and Monday with overnight lows falling into the middle 30s and lower 40s and highs in the lower to middle 60s. These temperatures would suggest some frost potential especially for the normally colder locations of the southern tier and areas east of Lake Ontario. It is likely that headlines will be needed at some point during this period. A gradual warming trend will then occur through middle week as the high shift slightly to the east allowing for a more southerly flow with highs reaching normal or slightly above normal by middle week with readings in the 70s. && Aviation /20z Wednesday through Monday/... at 18z VFR flight conditions were found across the region with a few showers and thunderstorms starting to Blossom across the lower Genesee Valley. Will carry thunderstorms across the Eastern Lake Ontario region...including the kart taf for this late evening and early overnight...with other locations just carry a vicinity thunderstorm. Some brief MVFR visibilities are possible within any storm. For tonight showers and thunderstorms will carry northward...with a low level jet of 35 to 40 knots across the region. Will carry low level wind shear overnight in the tafs. Tomorrow morning hours will likely be dry and overcast with showers becoming more likely later in morning and early afternoon as a cold front nears the region. At this time thunder looks to be limited along the cold front. Outlook... Thursday afternoon...scattered to numerous showers and possibly a thunderstorm with associated MVFR/IFR...otherwise VFR. Thursday night IFR/MVFR in showers. Friday...mainly VFR with a chance of showers. Saturday through Monday...VFR. && Marine... showers and thunderstorms this evening will diminish with the loss of daytime heating. An area of low pressure will cross just to the north of Lake Ontario tomorrow and drag a cold front across the lakes on Thursday. Colder air behind this frontal boundary will bring a slight increase in waves heights on both lakes...though waves will likely remain below 4 foot through Thursday night. Small crafts may be needed early Friday when wave heights peak...possibly at the 4 foot mark. && Buf watches/warnings/advisories... New York...none. Marine...none. && $$ Synopsis...Thomas near term...Thomas short term...tma long term...tma aviation...Thomas marine...Thomas