Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 230359
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1059 PM CDT SUN MAY 22 2016

.UPDATE...
Issued at 1055 PM CDT Sun May 22 2016

Updated to include 06z aviation discussion below.

&&

.SHORT TERM...(This evening through Monday)
Issued at 252 PM CDT Sun May 22 2016

An abrupt change will occur across Minnesota and western Wisconsin
late tonight, and into Monday as moisture increases
significantly in the boundary layer, and aloft. Both PWATs and
moisture transport are above the 95 percentile, with some areas
around the 99 percentile late tonight and into early Monday. This
is based on climatology between 1979-2009. This basically means
that when thunderstorms develop, rainfall rates associated with
these thunderstorms will be locally high. I did add heavy rainfall
in the forecast late tonight for these conditions. Later forecast
can re-access if rainfall rates will continue to be high Monday
afternoon, and Monday night.

Used CAMS to access timing of thunderstorms tonight in western
Minnesota where the best chance of widespread/organized convection
is likely. Further to the east in eastern Minnesota, the initial
dry airmass may hinder the onset of thunderstorms until after
sunrise. As for severe thunderstorms, and the latest information
from SPC, a few strong to severe thunderstorms will be possible
Monday afternoon. The severity of the storms will be based on
recovery of morning thunderstorms and the amount of instability.
Several of the WRF models do depict strong updraft speeds, but not
necessarily strong updraft helicity Monday afternoon along the
cold front in western Minnesota. Otherwise, Monday will be more
humid with breezy conditions along and ahead of the cold front.

.LONG TERM...(Monday night through Sunday)
Issued at 252 PM CDT Sun May 22 2016

An active weather pattern will ensue during the long term as
southwest flow dominates aloft with short wave energy emanating
from a deep trough in the west while a ridge strengthens in the
east.

At this point, the best chances for showers and thunderstorms are
Monday night, Wednesday and then from late Friday through much
of the upcoming holiday weekend, associated with the short wave
energy. Unfortunately, the long term is littered with pops from
start to finish. The most widespread and perhaps heaviest rainfall
looks to be on Wednesday where a half inch to one inch is
expected. Overall, rainfall for the long term will likely total in
the two to locally three inch range.

Temperatures will continue above normal through the long term.
Tuesday will be the warmest day with highs from 80 to 85. Highs
thereafter will be more in the 75 to 80 degree range, which is
still some 5 to 10 degrees above normal. Lows will be in the
middle 50s to lower 60s through the period, which again is 5 to
10 degrees above normal.

As was the case yesterday, the focus for strong to severe storms
is Monday evening. More CAMS now cover this period and there are
two areas of interest. First, due to the incoming convection
late tonight and Monday morning, redevelopment late Monday
afternoon and evening will hinge on how quickly we can recover on
instability. A scenario seen in most of the CAMS today is for
convection to develop in two areas. The first is west central into
central MN toward evening. This is ahead of a surface trough and
also close to the right entrance region of the upper jet. A second
area develops during the evening from southeast MN through west
central WI. This area may be tapping some pretty good instability
due to the best heating during the late afternoon as well as where
the strongest low level wind field is in the evening. Hence, we
certainly can`t rule out a few strong to severe storms Monday
evening.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1055 PM CDT Sun May 22 2016

All sites to remain dry thru the early morning hours, then will
expect showers and thunderstorms to develop over far western MN
and gradually shift eastward through daybreak. Have tried to
address latest model thinking that there appears to be two
distinct periods of convection: one around daybreak into late
morning and a second late afternoon into the evening. There may be
some scattered SHRA activity between those two times and the
timing may well need to be adjusted in later TAF issuances.
However, at this point, confidence has increased to start
breaking things out with more detail. Am looking for thunderstorm
activity to bring flight conditions down to MVFR-IFR levels but
have capped ceilings within MVFR while visibility is a blend of
MVFR to IFR. Conditions do look to generally improve late Monday
evening. In addition, have included LLWS at all sites since
gridded TAFs and BUFKIT east indicate 45-50 knots of wind within
the lowest two thousand feet and a directional difference of
around 30 degrees.

KMSP...VFR is expected through the morning push as short-term
models have slowed the progression of the precipitation into
eastern MN. However, just beyond the morning push is when the
first round of convection is expected. The heavier round of
convection is expected for the evening push, roughly 20z-24z
Monday evening, and conditions for this round may well drop into
IFR (which is lower than current thinking). Breezy SSW winds to
continue overnight through tomorrow, plus there is the strong low
level winds overnight into daybreak.

/OUTLOOK FOR KMSP/
TUE...Mainly VFR. Chc TSRA/MVFR. Wind S 5 kts.
WED...Mainly VFR. Chc TSRA/MVFR. Wind light and variable.
THU...Mainly VFR. Chc TSRA/MVFR. Wind south-southwest 5 kts.

&&

.MPX Watches/Warnings/Advisories...
WI...None.
MN...None.
&&

$$

UPDATE...JPC
SHORT TERM...JLT
LONG TERM...RAH
AVIATION...JPC


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