NWS IND:
.CLIMATE...
Issued at 231 PM EDT Fri Mar 29 2024
The eclipse is now 10 days away, and we`re starting to pick up on a
few long range signals. At 10 days out, there is still a lot of
ambiguity and uncertainty in the forecast, but given a few
consistent signals, a few assertions can be made.
Let`s start off with the 2-4 day outlook and how it will impact
April 8th. As mentioned previously, a deep trough is developing over
the Eastern Pacific, and will pass through the Midwest early next
week. The associated low pressure system is expected to reach the
Mid-Atlantic region late next week, and should subsequently rapidly
deepen as it interacts with increased coastal moisture. A upper
level system over Canada is also expected to merge, further
amplifying the East Coast trough/low.
Given a strongly negative NAO and PNA, synoptic scale influence
should dictate the pattern, and the rapidly deepening low pressure
system should "bottle-up" the upstream waves. This can be visualized
by a relatively tight Mountain-West ridge in the GEFS 500mb height
spaghetti plot around 140-200 hours from initialization. Many
ensembles are subsequently picking up on a Rex block type pattern
over the CONUS next weekend as we approach eclipse day. As stated,
there is still some uncertainty on where this blocking pattern will
be positioned, but typically, long range models are too progressive
with Rex blocks, leading to the current belief that downstream
ridging will be present over the Ohio Valley by eclipse day. It`s
difficult to downscale this synoptic pattern into a specific cloud
forecast for April 8th, but we will continue to monitor pattern
signals/consistency and update as needed.