ACUS11 KWNS 221514
SWOMCD
SPC MCD 221513=20
NDZ000-MTZ000-221915-

Mesoscale Discussion 2274
NWS Storm Prediction Center Norman OK
0913 AM CST Sun Dec 22 2024

Areas affected...Northwest to central North Dakota into far
northeast Montana

Concerning...Freezing rain=20

Valid 221513Z - 221915Z

SUMMARY...Light to moderate freezing rain (with rates possibly as
high as 0.1 inch/hour) is expected to begin across far northeast
Montana and into northwest North Dakota by early afternoon.

DISCUSSION...Regional radar mosaics show light to moderate
precipitation overspreading much of eastern MT, gradually moving
east into ND within the left-exit region of a modest mid-level jet.
12 UTC soundings from GGW and BIS show a pronounced 8-9 C warm nose
between 900 to 850 mb with sub-freezing temperatures at the surface
(including an impressive 22 C inversion on the BIS sounding). While
some modulation of the low-level inversion is expected through early
afternoon via wet-bulb cooling within the warm nose and downward
mixing of warmer air near the surface, forecast guidance and recent
surface obs suggest that most locations across northwest to central
ND will maintain favorable low-level thermal profiles for freezing
rain through much of the day.=20

Live web cams from Williston and Dickinson, ND show little in the
way of ongoing precipitation as of 15 UTC, suggesting that the
initial wave of light precipitation currently moving over western ND
is mainly saturating a dry 850-500 mb layer. This gradual saturation
will promote steadier precipitation through early/mid-afternoon as
additional showers migrate east from MT in tandem with the upper
wave/jet. As such, the potential for freezing rain is expected to
increase heading into the afternoon hours. Morning guidance suggests
freezing rain rates up to 0.03 inch/hour are likely, but more
aggressive solutions (notably the HRRR) hint that higher rates up to
0.1 inch/hour are possible (though not probable given relatively
weak mesoscale forcing for ascent).

..Moore.. 12/22/2024

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!7G0prS2MT35m4m4176Xt7zyKej38V6KoXDQyLuPB7hMX7HaveS4kvaB0uOfb7dHrqWKtLsKhY= rddUqmoKatrH54L_88$ for graphic product...

ATTN...WFO...BIS...GGW...

LAT...LON 48530222 47930087 47690052 47470038 47010035 46830046
46730079 46740107 46870167 47170261 47440340 47540373
47720412 48060434 48440428 48580419 48730381 48760310
48530222=20


=3D =3D =3D
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