Area Forecast Discussion

WHAT HAS CHANGED

Adjusted thunderstorm timing for today, pushing arrival times back by a few hours. Also adjusted thunderstorm chances for Friday the cold front has been forecast to speed up, limiting storm chances north of the Southern Tier.

KEY MESSAGES

1) High heat and humidity continues today, lasting into Friday. The weekend will be cooler but temperatures will remain above normal.

2) Multiple systems will traverse the area, kicking off scattered thunderstorms across the region today and Friday. Some of these storms could be severe, with damaging winds and hail as the main threats. Saturday will remain dry but another cold front on Sunday will bring a return of showers and storms in the afternoon and evening.

3) A broad upper level trough will bring cooler, more normal temperatures to start next week with a few periods of light rain possible.

DISCUSSION

KEY MESSAGE 1...

Temperatures have climbed into the mid 80s for most, and are expected to reach the upper 80s to low 90s by mid afternoon. With dewpoints in the upper 60s to low 70s, heat indices will reach the 90s for most. Valley locations across the Southern Tier and Finger Lakes will see values climb above 95F, which prompted the issuance of a Heat Advisory for these areas until 8pm tonight.

Temps and dewpoints will remain high tonight, falling into the mid to upper 60s and mid 60s, respectively.

Friday will be warm once again, but a cold front is expected to move into the area in the late morning hours, which will limit heating potential across the Finger Lakes and Mohawk Valley. They may see a brief period of upper 80s before the cold front moves through and drops temps back into the low 80s. Areas along and south of the Southern Tier could see temps reach the mid 80s to low 90s during the afternoon hours ahead of the cold front. With dewpoints in the mid to upper 60s, heat indices will climb back into the 90s. Confidence is not high enough to issue a Heat Advisory for tomorrow afternoon for these areas as questions still remain with the timing and speed of the front moving through and if early rainfall limits heating potential.

Behind the front, drier and cooler air will move in with highs in the low to mid 80s on Saturday with dewpoints in the 50s. A ridge on Sunday will push temperatures back into the mid to upper 80s before another cold front pushes through during the afternoon hours.

KEY MESSAGE 2...

The aforementioned heat and humidity will be the fuel that drives thunderstorm development today and Friday.

A shortwave trough is currently moving across northern OH, kicking off showers and storms over WPA and WNY. A cap currently remains over our area, but is expected to erode by 3pm. As the shortwave kicks eastward, it will provide the broad lift that, combined with MLCAPE values between 1500-2000 j/kg, will kick off scattered cellular thunderstorms moving into the area by the mid afternoon hours. As the axis of the shortwave moves into the area, the storms should transition into multi cell or linear segments as they progress across the area late this afternoon and evening. The main threat with the storms is expected to be damaging winds and small hail. PWATs in the 1.75-2.0in range indicate heavy downpours with isolated flash flooding possible, especially across portions of the Finger Lakes and Mohawk Valley that saw heavy rain yesterday. Storms should hit the I-81 corridor between 7 and 8pm and exit to the east by 10pm.

Friday will see another round of thunderstorms as a cold front pushes into the area from the west. Guidance has sped up the arrival of this cold front, now expected to push into our western areas by the late morning hours. This will limit CAPE values north of the Southern Tier. Vertical wind shear looks to be lacking ahead of and along the front as well, with values only approaching 20kts or so. With the severe storm ingredients somewhat misaligned, severe storms north of the Southern Tier currently look to be isolated at this time. A few storms may be able to become severe if they can tap into a localized area that has higher CAPE values and moisture, allowing strong downbursts to occur when the updrafts cannot hold the rain any longer. The best chance for severe weather looks to be along and east of the I-81 corridor as CAPE values should be the highest here and mid-level winds are forecast to increase, allowing for better storm organization and stronger winds to develop. Main severe weather impacts expected are damaging winds and hail. Rain should move east of the area by the evening, bringing a cooler, dry night.

Dry weather remains through Saturday and into Sunday as a ridge moves overhead. A trough approaches Sunday afternoon with an associated cold front that should kick off scattered showers and storms across the area during the afternoon and evening hours. Some of these storms could be severe.

KEY MESSAGE 3...

Near normal temperatures will return to start next week as a broad trough sits over the northern portion of the country. This will bring a period of beautiful weather with highs in the 70s and dewpoints in the upper 40s to low 50s. Rain returns by mid week as the trough axis swings through the eastern US.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

Conditions will remain VFR throughout most of the afternoon and evening, though showers and thunderstorms are expected. Some storms may become strong to severe with strong wind gusts, higher than what is mentioned in the TAFs. While tempo groups were used for the best estimated timing for storms, some amendments will likely be needed once storms develop. Guidance keep storms south of RME, so confidence was too low to include thunder there. Restrictions will be possible with showers/storms, especially if they pass directly over a terminal.

Once the showers move out, conditions may be briefly VFR. Fog will be possible at all terminals tonight but confidence is low at SYR and RME where skies may take longer to clear out. Given the added moisture from the rain and winds being light, any clearing will likely result in fog. IFR to LIFR fog is expected at ITH, ELM and potentially RME, though cannot be ruled out at other terminals. Timing of when the fog lifts is uncertain but conditions should gradually improve after 12z though some MVFR ceilings are expected to stick around at RME and SYR through the end of this TAF period.

Winds will be breezy this afternoon with some gusts up to 15 kts. As mentioned, stronger winds may be observed in showers and storms. Tonight, winds become calm before picking back up to 5 to 10 kts by Friday afternoon.

Outlook:

Friday Night...Mainly VFR; fog and restrictions late overnight.

Saturday...Mainly VFR

Sunday...Showers and thunderstorms with associated restrictions possible.

Sunday night through Monday...Mainly VFR; early morning fog and restrictions possible.

Tuesday...Low chance for afternoon showers and thunderstorms and associated restrictions.

BGM WATCHES / WARNINGS / ADVISORIES

PA...None. NY...Heat Advisory until 8 PM EDT this evening for NYZ015>018- 022>025-055-056.