NWS Forecast Discussion

FXUS63 KMPX 220357 AAB

Area Forecast Discussion...UPDATED
National Weather Service Twin Cities/Chanhassen MN
1057 PM CDT Sun Apr 21 2019

.SHORT TERM...(This evening through Monday night)
Issued at 251 PM CDT Sun Apr 21 2019

Early this afternoon, a nearly stationary frontal boundary lied from
southwest, to east central Minnesota, and into west central
Wisconsin. South of this boundary, temperatures have risen into the
70s, with a few 80s in south central Minnesota. Surface dew points
have also pooled along this boundary. Moisture pooling is especially
noted in an elevated layer (ACCAS reported at the Twin Cities
airport today) which has allowed for afternoon ML CAPE values
between 500-1000 j/kg in far southern Minnesota. There is also a
very strong cap in place so we need a trigger to initiate any

Satellite imagery supports an elevated PV anomaly across western
Iowa, moving northeast this afternoon. Models have been trying to
develop precipitation along this elevated PV anomaly late this
afternoon along the Iowa border. However, it hasn`t been consistent
enough to keep anymore than isolated/scattered showers/thunderstorms
this evening as this PV feature moves through the region. Most
likely the best forcing and moisture advection will occur along and
north of this front later this evening, and especially after
midnight. Based on elevated instability, mid-level forcing and
moisture pooling, a widespread area of showers and thunderstorms
will develop. It will most likely be focused from central Minnesota,
east of Long Prairie, to northern Wisconsin. The frontal boundary
will sagged south to the Iowa border later tonight, but a surface
wave, and associated low pressure system, will likely hold this
front along the Iowa border, east of Fairmont, through Monday

Once the main short wave, upper level system moves out into the
Plains tonight, and into Monday, the precipitation will begin to
focus along the strong thermal boundary northwest of the surface low
as it tracks across northern Iowa, into western Wisconsin.

Heaviest rainfall tonight will focus north of the Twin Cities, to
Ladysmith Wisconsin. I wouldn`t be surprised to see isolated two
inch amounts before morning if some of the convective cells train
over the same areas. The heaviest rainfall will begin to drift
southeast Monday morning, with most of the precipitation ending by
the late afternoon/early evening. Only west central Wisconsin will
see residual precipitation after midnight Monday.

Due to the persistent cloud cover and likely widespread
precipitation, temperatures tomorrow will hold nearly steady, with
only areas of west central Minnesota rising into the 50s as sunshine
develops late.

.LONG TERM...(Tuesday through Sunday)
Issued at 251 PM CDT Sun Apr 21 2019

Much of the later period looks fairly benign with slightly west-
northwest oriental zonal flow across the northern CONUS. However,
toward the end of the week and into the weekend the upper pattern
looks to significantly amplify with troughing developing to our
west and one or multiple systems of interest working into the
region. The model guidance diverges quite a bit after midweek, so
it`s too early to have to much confidence in the specifics beyond
Thursday, but suffice to say that next weekend looks potentially
active across much of the region. The only item of note prior to
then is a frontal boundary that pushes through Wednesday. There
isn`t great moisture return ahead of it, so it looks to move
through mainly dry. However, a second shortwave moves in behind it
and the guidance shows reasonable agreement in some post frontal
precipitation Wednesday night into early Thursday, particularly
over the southern portion of the area. Handled that possibility
with chance PoPs, while saving some higher PoPs (derived from
model consensus) for the weekend system(s).


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1057 PM CDT Sun Apr 21 2019

VFR conditions continue late this evening. Showers and
thunderstorms are beginning to develop across western and central
MN, which will continue overnight. A heavier round may develop
Monday morning from SC to EC MN. IFR cigs are possible Monday
before rapid clearing moves in Monday evening.

KMSP...The best chance for showers and storms will be from 07-11Z
tonight, then after 15Z Mon. The rain should end late tomorrow
afternoon with quick clearing later Monday evening.

Tue....VFR Wind N 5-10 kts.
Wed...VFR. Wind SW 10-15 kts.
Thu...VFR. Chc -SHRA. Wind NW 5-10 kts.





NWS MPX Office Area Forecast Discussion

Script by Ken True @Saratoga-Weather.org