BBS: TELESC.NET.BR
Assunto: MESO: Nws Weather Prediction Center College Park Md
De: COD Weather Processor
Data: Mon, 18 May 2026 00:59:07 +0000
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AWUS01 KWNH 180059
FFGMPD
WIZ000-MNZ000-IAZ000-180600-
Mesoscale Precipitation Discussion 0180
NWS Weather Prediction Center College Park MD
857 PM EDT Sun May 17 2026
Areas affected...Northern Iowa...Southern Minnesota...Parts of
Northwest Wisconsin...
Concerning...Heavy rainfall...Flash flooding possible
Valid 180100Z - 180600Z
SUMMARY...Increasing convective coverage and increasing moisture
flux into expanding convective clusters/small MCS features support
potential for repeating and spots of 2-4". Localized flash
flooding remains possible through the early overnight period.
DISCUSSION...GOES-E WV suite depict broad long-wave trough across
the Inter-mountain West with broad southwesterly flow downstream
across the Plains. At the apex an expanding convective complex
shows strong diffluent outflow pattern at the right entrance to
strengthening jet streak aloft providing broad scale ascent as
well as strengthening of a broad south-southwest LLJ. At the
surface the northern surface low/apex of a tight and deep inverted
surface trough is crossing out of SE SDAK into MN while drawing a
well defined warm front northward. CIRA LPW and RAP analysis
notes that core of western Gulf moisture is finally arriving
northward along and east of the advancing cold front that extends
from the surface low back across eastern NEB. The cluster in SW
MN has a very long history of severe and strong isallobaric
backing influence to maximize moisture flux pulled along and north
of the surface front, supporting intense but short-term rainfall
rates near 1.5-2"/hr mostly falling in 15-30 minutes. However,
given the stronger LLJ and isentropic ascent, downstream
convection is filling along and northeast where convergence is
maximized. Deep layer steering flow will allow for some repeating
of the cores to increase intense rainfall duration over 1-2 hours
allowing for localized totals to reach 2-3" values.=20
In addition, a second complex north of a secondary low across NE
NEB has seen a similar rapid cooling of the cirrus canopy with
numerous overshooting tops; deeper moisture pool has also
broadened the downdrafts width as the line matures into a larger
linear convective complex. While there is a general eastward
propagation, RADAR and satellite trends suggest there is also a
potential to repeat/track through similar areas of the northern
cluster across portions of S MN/N IA. Recent WoFS runs helps to
confirm this as mean and 90th percentile qpf suggest 2.5-5"
maximum swath is possible. This provides some confidence that
spots of 2-4" are becoming increasingly possible through the early
overnight period.=20
While NASA SPoRT 0-40cm soil moisture fields show drought is solid
with ratios running from 25% in NW IA to near 40% in south-central
MN toward the Twin Cities, the FFG values suggest 1hr rates of
1.5"/hr and less than 2.5"/3hr could result in flash flooding. If
that is the case, incidents of flash flooding are possible, but
given the overall drought conditions would be looking to smaller
localized incident or two where rates can reach closer to
1.75-2"/hr, where infiltration would be reduced from the shear
amount too fast. So given the overall pattern/trends, flash
flooding continues to be considered possible across the MPD area
of concern tonight.
Gallina
...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!6z3vCw4cBcd06sL2vpD6Yb8HccNxiHhZwedU4szunbouCqvjgG3v_xalByDNTvfqKBz2=
SOYEEzqR1bhyP_Oz3PWcFVo$ for graphic product...
ATTN...WFO...ARX...DMX...FSD...MPX...
ATTN...RFC...KRF...MSR...NWC...
LAT...LON 45259218 44609139 43359219 42549394 42299574=20
42559638 43409586 44359487 45209331=20
=3D =3D =3D
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