Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 180536
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1236 AM CDT Mon Mar 18 2024

.KEY MESSAGES...

- Elevated fire weather conditions will persist through the
  middle of the work week (especially on Tuesday).

- Strong winds return Tuesday, with NW gusts up to 40 mph
  possible.

- Confidence is increasing in the potential for accumulating
  snow across the region Thursday.

&&

.DISCUSSION...
Issued at 254 PM CDT Sun Mar 17 2024

Lucky or not, Winter has returned to the Upper Midwest to close the
weekend. Air temperatures have struggled to break out of the 20s
thanks to persistent northwest flow and widespread stratus overhead.
12z MPX RAOB captured the stratus layer aligned within the DGZ
around 5k ft, which has combined with moderate low-level omega
forcing to squeeze out periodic flurries across the area. Lows will
dip into the teens tonight and wind chills are projected to slide
into the single digits by daybreak. Low clouds will gradually
decrease in coverage tonight into tomorrow, revealing some
sunshine for Monday. Despite this, temperatures are forecast to
remain below normal, in the mid to upper 30s, given the cold
airmass aloft. Minimum RH`s will fall between 20-25%, elevating
weather concerns.

Not much has changed with forecast expectations on Tuesday. A
shortwave originating over south central Canada is progged to drift
southeast into the north central CONUS within the expansive region
of broad northwesterly flow. The associated surface low is expected
to track from roughly northwest Minnesota towards central Wisconsin.
A baroclinic zone will develop west of the surface low, with a
thermal nose set to drift east by way of warm air advection early
Tuesday. This will bring a notable one-day warm up, with highs back
above normal in the mid to upper 40s and low 50s. Surface winds will
turn northwesterly as the low passes to the east, with gusts near 40
mph due to the expected tight pressure gradient. Given the forecast
winds near advisory level, attention will also turn back to fire
weather concerns. The strong winds will combine with low minimum
RH`s and very dry fuels to increase the fire threat Tuesday
afternoon/evening. Cold advection will flip the temperature scenario
back to the cold side of things for Wednesday, with below normal
highs back in the low to mid 30s.

Active weather is set to return in the form of snow on Thursday. As
with any weather system 3-4 days out there is a level of uncertainty
that remains present, however the expected atmospheric scenario
will be favorable for potential accumulating snow. Guidance
advertises a dip in the 500 mb flow over Montana and the Dakotas
heading into Thursday, with an 850 mb shortwave set to eject east of
the Rockies. Warm air advection will increase ahead of the
shortwave, such that a notable mid-level thermal gradient will
develop across the Northern Plains. Forcing associated with the flow
of Pacific moisture and isentropic upglide will aid in the likely
development of a northwest to southeast oriented swath of
precipitation across the Upper Midwest, positioned to the north of
the 850 mb frontal boundary. Blended solutions place this swath of
snow right across central Minnesota, though there are still
north/south solutions on the table that will need to be resolved
before discussing snowfall amounts. QPF expectations remain somewhat
in flux, given significant differences among the Grand Ensemble
membership. The GEFS suite remains the wettest, with several members
in the 0.3"-0.5" range. The EPS and Canadian suites are drier, with
0.1"-0.3" of QPF available to work with. As with any
thermodynamically driven Winter event, there will be a frontogenic
component to the snowfall forecast (where enhanced banding of snow
may occur), however that precise axis will take several more
forecast runs to fine tune. To sum it all up, it appears
increasingly likely that snowflakes will fly and accumulate in some
fashion Thursday, which has been reflected in the latest PoPs from
the NBM (pushing 70% across central Minnesota). Specifics with
regards to snowfall amount, timing, intensity, and impacts will come
into a better picture in the coming days. Should the forecast
continue to trend in this direction, travel impacts will become
likely Thursday. Stay tuned!

As discussed by the midnight shift, Thursday continues to serve as a
prelude for what is to follow. Naturally, this is also the part of
the forecast where the specifics begin to fall off the table, but
guidance suggests next weekend bears watching for a more substantial
round of widespread precipitation and possible wintry weather. There
is good support across the ensembles that a deep trough will move
over the west coast next weekend, followed by the development of a
surface low pressure system in the Great Plains. Notable differences
in the track of the surface low exist, and will have further
implications on things like precipitation type and amount. Despite
the understandable challenges regarding many details, the big
picture idea is impressive and will require further updates
given such a strong signal this far out (NBM already features >
50-70% PoPs next Sunday!). While a large amount of uncertainty
does exist, the more active pattern that appears to be setting
up will benefit ongoing dry conditions. We`ll take what we can
get!

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1231 AM CDT Mon Mar 18 2024

Current TAF trends look good. Sites are going to spend much of
the night with BKN stratocu between 4k and 5k feet. These clouds
could produce some flurries, but no impact to visibility is
forecast. These clouds will clear out Monday morning, but be
replaced by a batch of mid level clouds Monday afternoon.
Tonight, we`ll lose gustiness, but we won`t have a period where
we lose the winds. We`ll see a sfc high shift to the east and
return flow set up across the region on Monday. Our winds will
be trending toward westerly and eventually WSW by Monday
afternoon. There will be potential for LLWS as a frontal
boundary pushes through Monday night.

KMSP...Given the forecast wind direction, cross winds will
begin appear in about 18 hours. Some gusts into the low 20s
will be possible with these cross-winds as well. We`ll have to
keep an eye on the possibility for a period of LLWS Monday
night after 04z.

/OUTLOOK FOR KMSP/
TUE...VFR. Wind NW 20G35kts.
WED...VFR. Winds NW 10-15G20kts.
THU...IFR/-SN likely. Some accumulation likely. Wind E 5-10 kts.
&&

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

&&

$$

DISCUSSION...Strus
AVIATION...BPH


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