Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 221028

Area Forecast Discussion
National Weather Service Salt Lake City UT
428 AM MDT Mon Apr 22 2019

.SYNOPSIS...A low pressure system over southwest Utah will drift
south into Arizona later today. High pressure aloft will build in
behind the exiting low pressure beginning tonight. This high
pressure will remain across the Great Basin through the middle of
the week.


.SHORT TERM (Until 00z Friday)...The upper low currently centered
over southwest Utah will continue to work south into western
Arizona later today. Building in behind the exiting upper low will
be high pressure aloft nosing into the western/northern Great
Basin beginning late this afternoon and evening. This high
pressure will expand across much of the western CONUS for the
middle of the week.

Warm advection wrap around in the northern flank of the upper low
extends across southwest Wyoming through far northern Utah early
this morning. This thermally-driven lift has been gradually
weakening overnight, with only residual light precip across
southwest Wyoming and far northern Utah at this time. Precip
remains convective near the Utah/Nevada border, though this
activity will likely rotate west into Nevada over the next couple
of hours.

One other area of active convection exists in the eastern flank
of the upper low across south-central through east-central Utah.
The driving force for this convection is likely a vorticity lobe
rotating north around the upper low. Not anticipating any further
strengthening or expansion in areal coverage of the convection as
the dynamic and thermal forcing are weak, as is the upper
divergence in the absence of any significant jet support.

The deformation axis associated with the exiting upper low will
align southwest through northeast across Utah this afternoon.
Increasing instability along with abundant moisture will allow
convection to expand along the deformation late this morning and
afternoon. This convection will dissipate quickly this evening as
the upper low continues south and with the loss of daytime

High pressure aloft building into the area from the west will
bring mostly dry and increasingly warm conditions to the forecast
area through Thursday.

.LONG TERM (After 00Z Friday)...Globals more in line regarding
the future presence of short wave energy crossing the northern
Rockies region beginning Friday night, each delving a bit further
south in latitude thereafter through the weekend (than in days
previous). Although still remaining north in the northern Rockies,
passage of these waves thereafter through the weekend does look to
lower heights in the north, with a slight cyclonic nature of the
flow aloft aiding to pin the ridge further south of the area. Ample
moisture and diurnal instability within this cyclonic flow looks to
promote daily convection in the north, though the south looks to
remain more stable/dry tied closer to the remnant ridge. Have
maintained generally chance/slight chance PoPs each day through the
weekend in the northern third as such, and with a slight diurnal
trend in likelihood.

Coincident with this will be a closed low slowly churning east off
the SoCal coast, a feature that looks to become absorbed and
translated inland within the northern branch flow early next week.
Model inconsistencies in how this absorption evolves vary in detail
(and resultant timing), but the big picture points towards a
maintenance of unsettled conditions early next week as well. Its a
continuation of spring, but remaining mild if not a bit above normal
at its coolest.


.AVIATION...Light and variable winds currently in place at the KSLC
terminal are expected to become a prevailing northwest by 16z this
morning. Periodic cigs AOB 6000ft AGL remain possible through that
time, but prevailing cigs above that level are expected. Future
shower development today is expected to remain south/east of the
terminal, but will likely impact the southern/eastern gates during
the peak heating hours today.





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