Area Forecast Discussion
Issued by NWS Twin Cities, MN

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KMPX 251737
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1237 PM CDT Thu Apr 25 2019

.SHORT TERM...(Today through Friday)
Issued at 432 AM CDT Thu Apr 25 2019

Primary concerns in the short term are lingering precipitation
over the south this morning then falling RH values and gusty winds
in the west this afternoon into early evening (which result in
some fire weather concerns). Frontal boundary is currently through
about half of the forecast area (bisecting it from northeast to
southwest) per latest MSAS analysis and surface observations. Much
of the observed precipitation is post-frontal and being forced by
the compact shortwave trough evident in water vapor imagery over
the eastern Dakotas. Things will quickly move east this morning,
with precipitation ending from west to east by mid to late
morning. There is some lingering elevated instability over the
area per SPC mesoanalysis MUCAPE, which is helping to produce some
embedded heavier precipitation near and south of the Minnesota
River valley.

Once the aforementioned activity departs, attention turns toward
clearing skies, deep mixing, and plummeting RH values across
western and central Minnesota. Forecast soundings from the RAP and
NAM suggest potential mixing to around 700 mb by mid to late
afternoon, which would produce RH values in the teens. Didn`t go
quite as low as mixed dewpoints would suggest, but went
sufficiently low to bring forecast RHs down to near 20 percent
across much of the western and north central portion of the area
this afternoon into early evening. Winds are expected to pick up
more substantially behind a secondary front/trough mid to late
afternoon, and the best overlap of stronger winds and low RH
values look to be over the west central portion of the forecast
area, so focused the fire weather concerns in that area for now.
However, if RH values wind up lower and/or winds pick up sooner
than expected (or over a larger area) then that may need
adjustment. High pressure will build in from the west later
tonight and remain in control through Friday, with winds dropping
off later this evening and becoming light and variable on Friday.

.LONG TERM...(Friday night through Wednesday)
Issued at 432 AM CDT Thu Apr 25 2019

Main topic of interest in the long term continues to be the potent
system impacting the area on Saturday, with widespread rainfall
expected along with the possibility for a narrow band of
accumulating snow in the region of heaviest precipitation. A
compact shortwave will approach the area overnight Friday, with
guidance taking the surface low on a more southerly track from the
central plains through central Iowa during the day on Saturday.
Impressive dynamics overall with this system with plenty of
curvature aloft to go along with strong mid-level warm advection
and frontogenesis. A widespread shield of precipitation is
expected to develop to the north of the surface along this lift,
with a narrow but intense band of precipitation expected to
develop near the region of greatest frontogenesis. Plenty of
moisture will be present with this system and 0.5-1 inch of
precipitation looks possible from central Minnesota south, with
amounts over an inch across far-southern Minnesota. While models
agree on the overall picture of this event, there is still
discrepancies on the placement and strength of this band, which
all will play a role in our possible precipitation types. While
colder Canadian air will filter down with this system and keep
temperatures limited to the 30s and 40s Saturday, it does not
appear to be cold enough to support widespread snow on its own.
However, ascent looks to be strong enough in the strongest band of
precipitation Saturday morning and afternoon to dynamically cool
the atmosphere enough for a narrow band of snowfall to occur. The
NAM is the strongest, and thus coldest, solution and generates a
rather widespread area of snow but appears to be an outlier at
this time. Trending closer to the ECMWF/CMC/GFS solutions would
give a scenario where we see likely see rain to the north and
south of the main precipitation axis where forcing is weaker, and
a narrow band of snowfall where the strongest ascent and heaviest
precipitation are located. Confidence remains low on just how much
snowfall we`ll see given the fine-scale forcing that models have
difficulty resolving at this range, as well as on whether snowfall
rates can overcome the late April Sun for anything to accumulate
on the ground. For now, the best chance for possibly a few inches
of slushy accumulation looks to be across southern Minnesota, with
better chances further east into southeast Minnesota and southern
Wisconsin.

Precipitation will wrap up Saturday evening as the low departs to
the east, with a brief dry spell expected Sunday as high pressure
passes over the region. There continues to be low confidence in
the details for the forecast next week, as models diverge on
handling the active jetstream oscillating over the northern US.
The active weather pattern looks likely to continue, but models
disagree on the timing of each successive system. At least a few
occasions of precipitation along with below normal temperatures
appear likely.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1213 PM CDT Thu Apr 25 2019

Mid to high level cloud cover will continue clearing to the
southeast this afternoon with mostly clear skies expected through
tomorrow morning. Northwest winds will remain brisk through this
afternoon, gusting to near 25 kts. Winds will remain near 10 kts
overnight before increasing again during the mid-morning tomorrow.

KMSP... VFR conditions are expected to continue.

/OUTLOOK FOR KMSP/
Friday night...VFR. Northwest wind less than 10 kt becoming east.
Saturday...MVFR expected, IFR possible with a chance of rain and
snow. East wind around 10 kt becoming northeast 10 to 20 kt.
Saturday night...VFR. Northeast wind 5 to 15 kt becoming variable
around 5 kt.
Sunday...VFR. Southeast wind 5 to 15 kt.
Sunday night...MVFR possible late with a chance of rain.
Southeast wind 5 to 10 kt.
Monday...MVFR possible with a chance of rain. Southeast wind 10
to 15 kt becoming west.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Red Flag Warning until 8 PM CDT this evening for MNZ041-047-048-
     054>056-064.

&&

$$

UPDATE...
SHORT TERM...
LONG TERM...ETA
AVIATION...AMK


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.