Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
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653 FXUS61 KPBZ 200749 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 349 AM EDT Thu Jun 20 2024 .SYNOPSIS... A dangerous heat wave will impact the region this week. A Heat Advisory and Excessive Heat Warning are in effect through Saturday. This event is highly unusual for our region and could be worse than the 1994 heat wave. Isolated afternoon thunderstorms may pose a damaging wind threat. && .NEAR TERM /THROUGH FRIDAY/... KEY MESSAGES: - Excessive Heat Warning for the urban areas of western PA; Heat Advisory continues elsewhere. - A marginal risk of strong to severe thunderstorms this afternoon/evening and also Friday afternoon/evening. ------------------------------------------------------------------- Expect localized patches of fog through dawn. Low temps will once again be in the lower 70s in many areas, allowing for little relief from the heat overnight. Less upper cloud coverage on today and Friday will allow for highs to reach back into the low to mid 90s and a 60-70% chance of >95 degrees, highest in the urban areas and valleys. With dew points still in the upper 60s/low 70s, heat index values will remain around or above 100 degrees. 50-70% chance of lows >70 will continue to provide little relief from the heat at night. Considering heat effects will be cumulative, late week looks compoundingly dangerous. The early season event, and temperatures increasing slightly each day, will exacerbate any existing heat issues. Potential impacts include heightened heat-related illnesses and power grid issues with increased demand. It is strongly encouraged to know where cooling shelters are located and stay hydrated. There may be little relief at night. Make a list of friends and family to check on and help them prepare. Prolonged exposure to excessive heat was the primary cause of weather-related fatalities in 2023. For our region, this heat wave may be compared to our worse than June of 1994. Please see the Climate section below for more numerical details on the kinds of records that may be in jeopardy. Weak upper waves on the northern periphery of the 596-598 dm ridge, along with a lake breeze, may again allow for some pop up thunderstorms in the afternoon both days. Best chances for today will be Pittsburgh and north. With instability topping out at roughly 1500 J/Kg MU CAPE and roughly 1000 J/Kg of DCAPE, once again, the heat in place will make the environment favorable again for scattered storms to have a downburst potential. Thus, the SPC has issued a Marginal Risk. The same holds true for Friday afternoon and evening with similar parameters in place. There does stand the potential to have greater instability in place given the weak influx of moisture. The other concern is that while the Thursday convection has a bit more low level flow, the activity on Friday is under even weaker flow and may pose the risk for a flooding threat. && .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... KEY MESSAGES: - Dangerous heat continues through the end of the week with little relief at night. - Excessive Heat Warning and Heat Advisory remain in effect. - Chance of thunderstorms in the afternoon. ------------------------------------------------------------------- The upper ridge will begin to retrograde on Saturday but still hold strong enough for one more day providing a continuation of the dangerous heat, and perhaps the hottest day. Ensemble 850 mb temperatures still remain in the 22-24C range and even the NBM 10th percentile suggests low to mid 90s. Highs will climb by a few degrees into Saturday with probabilities indicating Saturday may be the hottest. Some records may be challenged. Due to the compounding effects, continued heat indices at and above 100 degrees, and the WPC heat risk tool showing major to extreme impacts, the heat headlines have been extended through Saturday. That said, some subtle weaknesses in the flow as the ridge axis pulls south and allow for isolated to scattered afternoon convection to throw wrinkles in the heat, but predictability in coverage and location is low probability. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... KEY MESSAGES: - Relief from the heat favored with a passing trough over the Great Lakes Sunday into Monday. - A weaker ridge builds in after Monday. ------------------------------------------------------------------- Come Sunday into Monday, the ridge retrogrades with ensemble clusters showing respectable agreement on an upper trough pushing down through the Great Lakes and 500 mb heights decreasing up to 10 dm by Monday. Surface high pressure migrates off to the east ahead of low pressure associated with the upper trough that drags to our north, but some timing differences with it lend lower confidence. Ensemble precipitation chances increase overnight Sunday into Monday as a cold front may drag through during that timeframe. Upper ridging is then favored to build back in by mid week with highs again potentially increasing to above 90 degrees, but heights don`t look quite as extreme as this week. && .AVIATION /08Z THURSDAY THROUGH MONDAY/... Light/calm wind is expected overnight. Fog will be possible primarily at FKL where evening storms boosted boundary layer moisture. Light winds continue on Thursday, becoming more variable into the afternoon. Afternoon storms are expected to initiate on the lake/land boundary and possibly allow enough outflow to initiate convection north of KPIT. PROB30s were included for the most susceptible ports (BVI,FKL,DUJ) for now. It is possible that these mentions expand. Any storms will be capable of downbursts with elevated instability and dry air. Fog will again be possible Thursday night, mainly in areas that receive afternoon/evening rain. .Outlook... Modest probability for VFR and dry weather through the week with upper ridging, save any isolated afternoon thunderstorm chances. Restrictions with rain may return late this weekend with a cold front. && .CLIMATE... The area has the potential to break various heat-related records. There is low probability that climate sites approach the highest temperatures recorded in the 21st century: Pittsburgh, PA: 98F (7/7/2012) Wheeling, WV: 98F (7/7/2012) Morgantown, WV: 101F (7/7/2012) New Philadelphia, OH: 101F (7/7/2012) Zanesville, OH: 101F (7/7/2012) DuBois, PA: 101F (7/22/2011) There is a modest probability many June all-time temperature records may be at stake: PIT: 98F (1988) HLG: 100F (1933) MGW: 99F (1893) PHD: 99F (1988) ZZV: 101F (1988,1934) DUJ: 92F (1969) *RECORD TIED ON 6/18/24* Daily high maximum (left) and high minimum (right) temperature records are at stake for: Thursday, June 20th Pittsburgh, PA: 95F (1994) 78F (1924) Wheeling, WV: 97F (1933) 70F (1924) Morgantown, WV: 99F (1893) 75F (1924) New Philadelphia, OH: 95F (1994) 71F (2009) Zanesville, OH: 98F (1934) 75F (1924) DuBois, PA: 89F (1991) 66F (1996) Friday, June 21st Pittsburgh, PA: 95F (1933) 73F (1934) Wheeling, WV: 99F (1933) 69F (2016) Morgantown, WV: 95F (1953) 72F (1988) New Philadelphia, OH: 94F (1994) 72F (2016) Zanesville, OH: 97F (1988) 72F (1997) DuBois, PA: 89F (1991) 68F (1988) Saturday, June 22nd Pittsburgh, PA: 98F (1988) 75F (1988) Wheeling, WV: 95F (1923) 72F (2011) Morgantown, WV: 96F (1923,1988)73F (1988) New Philadelphia, OH: 97F (1988) 71F (1997) Zanesville, OH: 99F (1988) 71F (1997) DuBois, PA: 91F (2022) 68F (2022) && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...Heat Advisory until 8 PM EDT Saturday for PAZ007>009-013-015- 016-022-031-074-076>078. Excessive Heat Warning until 8 PM EDT Saturday for PAZ014-020- 021-029-073-075. OH...Heat Advisory until 8 PM EDT Saturday for OHZ039>041-048>050- 057>059-068-069. WV...Heat Advisory until 8 PM EDT Saturday for WVZ001>004-012-021- 509>511. && $$ SYNOPSIS...MLB/Shallenberger NEAR TERM...Shallenberger SHORT TERM...MLB/Shallenberger LONG TERM...MLB/Shallenberger AVIATION...Rackley/Milcarek CLIMATE...SKH/CM