Sunrise 6:15 AM   Sunset 8:23 PM Moonrise 3:50 AM   Moonset 4:42 PM

  Print   HELP   Reset   Save   Recall

FXUS61 KPBZ 050036 AFDPBZ

Area Forecast Discussion National Weather Service Pittsburgh PA 836 PM EDT Sat May 4 2024

SYNOPSIS
Intermittent rain and a few storms are possible through the weekend. With clouds and rain, temperatures will be cooler today, but will rebound Sunday as a southerly flow returns. A brief break in the rain is possible Monday.

NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES:

- Showers continue through the overnight.
-------------------------------------------------------------------

The east coast ridge has moved very little. We will continue to rest on the western side of the ridge where a shortwave will continue to drift northward into the evening.

Deep moisture will continue to flow northward on the backside of the ridge axis keeping in plenty of clouds and the risk for showers through the evening. For the most part, rainfall should be on the light side. There are some deterministic models that suggest a 1.40 PWAT leading to the 99th percentile in dealing with climo PWATs. That said, the NBM only gives roughly 20% probability of > 0.75 inches from through 2am tonight. Clouds, showers and a cool easterly flow will keep temperatures slightly below normal today. Expect thunderstorms to dissipate by 10pm but the shower potential is expected to persist through tonight.
This will keep warmer temps around for the low.

SHORT TERM /SUNDAY THROUGH MONDAY/
KEY MESSAGES:

- Unsettled pattern remains with rain chances continuing on Sunday. Thunder possible on Sunday.
- Temperatures push back above normal Sunday and Monday.

-------------------------------------------------------------------

East coast ridge will flatten and drift eastward on Sunday. The shortwaves riding northward on the western flank of the ridge will also shift to the east. Shower coverage looks to dissipate Sunday morning. A weak cold front will slowly cross Ohio Sunday. Models are hinting that scattered storms could develop ahead of the front Sunday afternoon. The air mass during the afternoon is certainly conditional and with any breaks in cloud cover or WAA at the surface will be enough for convective development. In fact, PWATS another day being in the 1.20 to 1.40 range with skinny CAPE will make for a heavy rainfall threat. However, there are some dry layers in the model soundings with DCAPE values between 400 J/Kg and 600J/Kg may lead to a few strong storms with downburst potential. Temperatures will warm on Sunday as the low-level flow veers to the southwest ahead of the front which may be enough to kick start the event tomorrow afternoon.

Ensembles have been consistent in showing a shortwave trough over the Middle Ohio Valley approaching, but weakening, on Monday as it interacts with a weak ridge over our region. A south-to-north gradient in PoP values still seems appropriate for the Monday/Monday night period. The pattern does continue to coincide with development each day with day time heating.

LONG TERM /MONDAY NIGHT THROUGH SATURDAY/
KEY MESSAGES:

- Rain chances continue next week but more uncertainty lends to lower confidence.
- Temperatures favored to remain above normal.
-------------------------------------------------------------------

Uncertainty still reigns after Monday. Most guidance depicts a ridge centered over the Great Lakes at 12Z Tuesday, along with a deep closed upper low in or near the Dakotas. The upper low appears likely to fill during the midweek period, and as it does so, shortwaves rotating around it appear to flatten out the ridge as it moves across the Upper Ohio Valley, finally eroding it almost completely in the northeast CONUS. Some strength and timing issues remain with the details of this process, which in turn could impact precipitation amounts and timing.

Nevertheless, a warm front is likely to cross on Tuesday as the ridge progresses eastward. This will lead to the persistence of a warm and moist airmass, with precipitable water values at or above the 90th percentile in the climatology. Along with the previously mentioned shortwave activity, this will keep an active weather pattern in place for our region, with decent daily precipitation chances through Friday. Deep-layer shear will increase as well behind the departing ridge, so severe weather chances will need to be monitored as well. According to CSU machine-learning guidance and NBM CWASP probabilities, Wednesday and Thursday may be the days to watch.

Rain chances then continue to show additional activity on Friday with the post frontal trough passing across the area.
There is little confidence on this occurrence though.

AVIATION /01Z SUNDAY THROUGH THURSDAY/
Weak embedded shortwaves within broad southwest flow on the west side of a ridge axis will continue to promote waves of showers with low probability lightning through 15z Sunday. Coverage and storm intensity will vary through that time, but it remains hard to define the exact timing of the heavier rains and more widespread coverage. Position of the region generally to the NE of a weak surface low feature means area cigs will remain or fall through the overnight hours, resulting in widespread MVFR/IFR restrictions.

Modest height arises ahead of a more clearly defined wave combined with diurnal heating will lift area cigs after 15z and promote a brief lull in convective activity. Late day passage of that shortwave and associated weak surface cold front will create scattered thunderstorm coverage mainly after 21z.

Outlook
A moist boundary layer behind the frontal passage and evening thunderstorms Sunday night likely will lead to widespread MVFR/IFR restrictions. Some improvements are expected Monday with influence of high pressure to the north, but shortwave movement across the TN River Valley may maintain some restriction/precipitation chances for southern terminals.

The rest of the week will remain active with varying periods of precipitation and restrictions amid low pressure passage.

PBZ WATCHES/WARNINGS/ADVISORIES
PA...None.
OH...None.
WV...None.

Full Color Weather Map

Link to Loop


Other links: GEOS-West     Contential US     Full GOES-East

Pittsburgh, PA,