WPC Met Watch |
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Mesoscale Precipitation Discussion: #0840 (2018) |
(Issued at 1258 AM EDT Sat Sep 15 2018
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MPD Selection |
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Mesoscale Precipitation Discussion 0840
NWS Weather Prediction Center College Park MD
1258 AM EDT Sat Sep 15 2018
Areas affected...north-central to northeastern MN
Concerning...Heavy rainfall...Flash flooding possible
Valid 150456Z - 151010Z
Summary...Flash flooding will be possible across portions of
northeastern MN through 10Z. Rainfall rates of 1-2 in/hr may lead
to 2-4 inch totals through early morning.
Discussion...Regional radar imagery as of 0430Z showed scattered
convection ongoing across north-central MN, with an average cell
movement off toward the east-northeast at 20-30 kt. These storms
were driven by warm advection and were elevated in nature,
occurring north of a stationary front extending from western Lake
Superior to a surface low in eastern SD. While KDLH dual-pol
rainfall estimates peaked in the 2-3 in/hr range as of 0430Z, some
hail contamination was likely occurring with ground truth
reporting rates between 1-2 in/hr. A gradient in MUCAPE was shown
in 00Z RAOB data between MPX (2599 J/kg and INL (0 J/kg), with the
convection presently occurring within the 1000-1500 J/kg MUCAPE
range, consistent with the SPC mesoanalysis page. 850 mb flow from
the south-southwest was estimated to be 20-30 kt over western MN,
with the KFSD VAD wind showing about 25 kt, and this flow pumping
in precipitable water values near 1.5 inches into north-central
MN. 850-300 mb mean flow parallels the stationary front draped
across the region which is allowing periods of training cores of
heavy rain.
Short term forecasts from the RAP support some increase in MUCAPE
across far northeastern MN with continued low level moisture flux
from the south through 10Z, out ahead of a subtle 700 mb shortwave
observed in VAD wind plots over western ND. Given ample moisture
and favorable flow orientation with respect to the
quasi-stationary front, training is expected to continue over
north-central to northeastern MN through 10Z with an additional
2-4 inches of rain possible. Portions of the area show Flash Flood
Guidance values of 2-3 inches in 3 hours, so some exceedance is
possible.
Otto
ATTN...WFO...DLH...FGF...
ATTN...RFC...NCRFC...
LAT...LON 48439258 48229007 47569018 46739188 46509414
46659505 46949539 47279540 48059445
Last Updated: 1258 AM EDT Sat Sep 15 2018
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