textproduct: Pittsburgh

WHAT HAS CHANGED

Increased coverage of passing showers and thunderstorms this afternoon. A Marginal Risk of severe weather has been introduced for Monday. High confidence still on soaking rainfall on Monday.

KEY MESSAGES

1) Scattered showers and storms Saturday afternoon

2) More widespread rain chances return Sunday night and Monday. There is high confidence in a soaking rainfall, but low confidence in the threat of flooding.

DISCUSSION

KEY MESSAGE 1... Expect troughing to linger across the area today. This coupled with strong surface heating, will allow scattered showers and thunderstorms to develop across the area today. Surface parameters suggest with a 500 to 750 J/KG SB CAPE and 500 J/KG DCAPE, some sub severe wind gusts seem more likely. In fact, model soundings suggest a 40 mph wind gust at best for this afternoon. In addition, heavy downpours are not likely to occur either as PWATs from mesoanalysis shows values of 0.8 to 0.9.

Conditions today will favor a more diurnal trend for convection today. Thus, showers and thunderstorms are expected to dissipate and come to an end by sunset or just after.

KEY MESSAGE 2... The mid-level ridge axis reaches the CWA around 00Z Monday, after which moisture surges northeastward into our region ahead of a surface low which will be riding up the Ohio Valley. Precipitable water likely surges into the 1.7 to 1.8 inch range by Monday, which reaches the 90th to 95th percentile of climatology. This, coupled with an east-west oriented warm front across the region, suggests rounds of moderate to heavy showers and thunderstorms are likely during the Sunday night to Monday period.

The NBM probs for rainfall show greater than 80% for 1 inch of rainfall from Sunday morning through Monday morning. The probs for 1.5 inches have gone down a bit from the previous run with roughly 40% to 50% with 2 inches showing 20% to 30%. This slight decrease due to the slightly southern track aligns with the slight being pulled out of the area and thus the area is only expected to be under a marginal outlook for Monday. It will depend on training storms and how much rain falls in a short period of time to be concerned for a potential flood threat.

The other impact for Monday will be a severe potential as a Marginal outlook was introduced for wind gusts. As the boundary sags south, the afternoon heating may be enough to spawn a few strong thunderstorms with the potential for damaging winds. However, morning showers and cloud cover could sabotage the amount of instability.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Scattered showers and a few thunderstorms have begun to develop across the region due to the weak shortwave passage. Cloud tops will struggle to cool below -10C to -15C given relatively weak buoyancy, so any lightning activity should remain fairly isolated with the highest confidence of this and precipitation coverage at FKL and DUJ. TEMPOs for TSRA were used here, while other terminals to the south have PROB30s for SHRA with low confidence in rain-induced restrictions. Any activity should end by sunset as the shortwave departs, with a VFR evening.

Some gusts of around 20 knots out the west during this afternoon. Localized areas of fog or lower stratus may develop Sunday morning as winds calm and clouds clear. Currently, MGW/LBE and FKL/DUJ have the best chance for this, however, they were omitted from the TAFs due to low confidence in its occurrence.

During the day on Sunday, skies will remain SCT through early afternoon when BKN ceilings move in ahead of the incoming system. CIG/VIS restrictions are likely Sunday night into Monday.

Outlook... Probabilities favor overnight Sunday into Monday for widespread showers (low probability thunderstorms) resulting in MVFR/IFR restrictions as a deeper trough/surface low combo travels through the Ohio River Valley region.

PBZ WATCHES/WARNINGS/ADVISORIES

PA...None. OH...None. WV...None.