Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 162007

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
307 PM CDT Sun May 16 2021

.SHORT TERM...(This evening through Monday night)
Issued at 241 PM CDT Sun May 16 2021

Surface analysis this afternoon shows a rather nondescript pressure
pattern over the Upper Midwest as one quasi-stationary frontal
boundary remains over the Central Rockies extending eastward into the
Ohio River Valley with a second stalled frontal boundary draped
east-west over southern Canada. Aloft, a ridge axis is analyzed to
the lee of the Rockies from Saskatchewan Province southward to TX/OK
while a cutoff low remains over southern CA/NV.

The lingering surface trough exiting MN/WI had kept low stratus in
place over much of eastern MN into western WI through the first half
of the day today, with some patches of it still along the Mississippi
River in southern MN, but by and large the only cloud cover is
streaming high cirrus across the region. This is owing to
unimpressive low level features along with moisture riding over the
western ridge and across MN/WI. What`s left of the low stratus will
erode by sunset, while the stable atmosphere will promote tranquil
conditions overnight into Monday. With the additional low level
moisture over WI and winds dropping off overnight, patchy ground fog
can again be expected overnight but not expecting the coverage of
dense fog as was seen this morning. With the western ridge building
more over the north-central CONUS, this will continue to keep any
convection in check and promote mid-to-high level cloud cover across
the area. At the same time, the southwestern low will be starting to
undercut the ridge, shifting into the deep south and helping spawn a
low pressure center along the central CONUS stalled front. Going into
Monday night, additional moisture convergence with the front and
heightened isentropic lift in advance of the low in northern IA into
southern MN will spread isolated to scattered rain showers during the
nighttime hours Monday night near the I-90 corridor.

As for temperatures, fewer cloud cover complications will allow the
ongoing warming trend to continue. Highs on Monday will climb to
generally the 75-80 degree range. The same trend will be seen in low
temperatures, which will drop to the upper 40s to lower 50s tonight
followed by the 50-60 degree range tomorrow night. This is owing to
higher dewpoints being advected into the region (which, by the way,
will aid in having higher minimum RH values in the afternoons).

.LONG TERM...(Tuesday through Sunday)
Issued at 241 PM CDT Sun May 16 2021

Not much change in the forecast trends for from midweek on, with
warmer and more humid weather expected along with at least a few
rounds of showers and thunderstorms.

Upper level ridging will be well-established over the region by
Tuesday, but cloud cover streaming north of a system over the central
plains and mid-Mississippi valley will likely keep temperatures a
few degrees cooler compared to the rest of the week. Highs in the 70s
still appear likely though given the warm airmass in place. A few
showers can`t be ruled out across southern Minnesota, but the bulk of
the precipitation will remain close to the frontal boundaries set up
well-south of the area.

The flow aloft becomes more meridional, and thus more active, on
Wednesday as the ridge overhead pivots in response to a trough coming
onshore the pacific coast. This general upper air pattern persists
into the weekend, with a prolonged period of southerly flow ushering
in warmer and more humid air into the region. Highs in the upper 70s
to low 80s look likely along with muggier dewpoints in the 60s, both
of which will lead to noticeably more summer-like conditions.
Ensemble and deterministic guidance continue to highlight a few
disturbances passing overhead, any one of which could lead to areas
of showers and thunderstorms. PoPs remain fairly broad- brushed given
the lack of precision among members in resolving these features,
with at least mentionable chances of precipitation possible from
Wednesday through the weekend. The most likely period within this
range continues to be Wednesday night through Thursday when most
solutions gnarly depict a more organized area of showers and
thunderstorms. It`s still early to have solid confidence in potential
rainfall amounts for any one area, as this will depend on where each
individual disturbance tracks and how many rounds of precipitation
(especially thunderstorms)impact each. It looks likely that we`ll see
widespread rainfall amounts of at least 0.25-0.5", with perhaps
better chances for heavier amounts across northern Minnesota.
Excessive rainfall does not appear likely, despite the anomalously
high precipitable water values, as each potential disturbances
appears to be fairly short-lived and transient. Instability and shear
values trend upwards late in the week and over the weekend, which
could lead to better chances for organized thunderstorm complexes
along with locally heavy rainfall and/or strong to severe
thunderstorms. &&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1204 PM CDT Sun May 16 2021

Low stratus shield ever-so-slowly eroding over far eastern MN through
western WI but obs are indicating the steady increase in ceilings and
scattering out of sky coverage. Have maintained MVFR ceilings at KMSP
and the WI TAFs for a couple hours at the start of this TAF set then
they will join the remainder of the TAF sites in VFR. Overnight
ground fog looks likely again over the WI sites, with potential for
IFR at KEAU, so have included its mention. Otherwise, high clouds
will continue to stream across the area. Winds generally remain SE
with speeds under 10 kts.

KMSP...Ceilings now about 1700ft and will remain as such. Timing the
change from BKN to SCT looks to occur around 19z, potentially as late
as 20z. No additional problems expected thereafter and fog will
remain away from KMSP tonight.

Tue...Mainly VFR. Chance p.m. SHRA/TSRA/MVFR. Wind SE 10-15 kts.
Wed...SHRA/TSRA/MVFR likely, mainly p.m. Wind S 10 kts.
Thu...SHRA/TSRA/MVFR likely, mainly p.m. Wind S 10-15 kts.




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