405
FXUS63 KMPX 141938
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
238 PM CDT Wed Aug 14 2024

.KEY MESSAGES...

- Rain increases in coverage this evening, with the bulk of
accumulation falling from 7pm tonight through 7am tomorrow. Isolated
thunder possible, but storms not expected.

- Wrap around showers continue through Friday with dry weather
returning this weekend.

&&

.DISCUSSION...
Issued at 237 PM CDT Wed Aug 14 2024

Showers have been slow to develop today which coincides with what
CAMs were saying yesterday, as opposed to the much more aggressive
and widespread global models. The culprit is relatively weak forcing
as until now there has been limited shortwave energy within the
upper level wave developing the surface low over us, which has kept
widespread rain development out of the MPX area and confined to Iowa
and the Dakotas. This is expected to remain the case over the next
few hours as we await the nocturnal strengthening of the low level
jet to bolster the forcing and produce more widespread showers
across the area, which looks to arrive after 6-7pm this evening.
Forecast soundings continue to point towards little to no
instability potential, thus we are not expecting thunderstorms other
than the odd rumble of thunder in primarily southern Minnesota as
the jet strengthens this evening. The bulk of the precipitation is
expected to fall between 7pm to 7am while the jet is strongest, with
moisture rich air advecting northwards alongside the low level
convergence characteristic of a low level jet. The expected rain
amounts have decreased on the high end, with the expected range
being 1/2 to 1 inch give or take a 1/4 inch or so depending on where
some heavier showers set up overnight.

Continued showers are expected on and off throughout Thursday as the
upper level low occludes with the surface low spinning over the
northern half of the state, with the MPX coverage area with an area
of cold air advection aloft on top of relatively warm lower levels.
Additional accumulations will only range from a tenth to a quarter
inch through Thursday with additional hundredths from more isolated
cold air showers on Friday.

As the upper level low moves eastwards by mid to late Friday,
showers will exit with it as a broad upper level ridge builds over
the western CONUS with northwesterly flow alongside general
subsidence. Shower chances appear scarce in this setup although we
could get a few showers next week with potential shortwave energy
drifting through the area on the eastern side of the ridge.
Otherwise, expect similar temperatures to the previous couple of
weeks with mostly upper 70s to low 80s for highs and diurnal cumulus
being the majority of the cloud cover.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1205 PM CDT Wed Aug 14 2024

Most sites will initialize at VFR outside of SW MN sites (KRWF).
The main concern this period will be the rain this afternoon
through Thursday morning. Rain showers will gradually move
NE from SW MN into the Twin Cities and W WI by this evening. A
heavier, steady rain will begin after sunset. This will bring
the onset of low MVFR and IFR ceilings across the MN TAF sites
and WI sites Thursday morning. Continued -SHRA usage for
spottier coverage this afternoon and Tuesday morning and -RA for
steadier rain overnight. IFR is likely at all sites (outside of
EAU until later Tuesday AM) tonight. Lower confidence for any
TSRA tonight so I`ve opted to leave it out of the TAFs. We`ll
see rain begin to taper off Tuesday morning with a gradual
improvement of cig/vsbys by the end of the TAF period.

KMSP... VFR through mid-afternoon before lower VFR and MVFR cigs
settle in at MSP. Confidence remains high for rain to begin
later today and steadier, heavier rain tonight into Thursday
morning. Exact timing may vary by an hour or two either way of
the 18z MSP TAF given some discrepancies in the guidance. Start
time may trend from 22z to 23z-00z for instance. Low confidence
on TS/CB through 18z Thursday but opted for a PROB30 for
-TSRA/CB after 20z Thursday afternoon.

/OUTLOOK FOR KMSP/
FRI...VFR, chc MVFR/-SHRA. Wind NW 10-15 kts.
SAT...VFR. Wind NW 10 kts.
SUN...VFR. Wind NW 5-10 kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.

&&

$$

DISCUSSION...TDH
AVIATION...BPH