Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 250612
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
112 AM CDT WED MAY 25 2016

.SHORT TERM...(This evening through Wednesday)
Issued at 305 PM CDT Tue May 24 2016

Finally seeing some isolated showers and storms popping across west
central Minnesota this afternoon...where an impressive 3000 J/KG
of Most Unstable CAPE and Lifted Indices around -6C are being
analyzed. Despite the presence of impressive instability, there
appears to be an absence of any strong lifting/forcing mechanism,
with low/mid level ridging building in from the west. Therefore,
while spotty storm development will likely continue to occur with
the afternoon heating, expect the severe threat is very
low/marginal.

Dewpoints stay elevated in the 50s to lower 60s tonight as we await
the arrival of more widespread convection from the southwest.
Conditions will remain rather muggy, with lows in the mid 50s to
lower 60s and little wind. This will also create the potential for
some fog development, primarily over east central MN and west
central WI where less cloud cover and lighter winds are projected.

Wednesday looks to be nearly a slam dunk for precipitation given the
progged support from a shortwave trough, favorable upper level jet
dynamics, and impressive low level moisture transport. By daybreak
Wednesday, expect to see the complex of showers and thunderstorms
having reached west/south central MN, then spreading toward the
MN/WI border by noon. We look to dry out over west/south central MN
by Wednesday afternoon. If we see some clearing, thunderstorm
redevelopment could mean severe storms, with the triple point
located just to the west in central South Dakota, a warm front
stretching into MN, and a trailing shortwave pushing into the
Dakotas. Large hail and damaging winds would be the primary
concerns, although the wind profiles and frontal boundary would also
suggest a tornado threat.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 305 PM CDT Tue May 24 2016

A warm and unstable pattern will prevail through the long term as
the local area is sandwiched between a trough of low pressure in the
west and a ridge of high pressure in the east.

Model agreement was pretty good today between the gfs and ecmwf. The
most significant period for showers and thunderstorms is from friday
night through Saturday night when a strong wave aloft moves
northward across the upper mississippi valley. widespread rain
amounts of an inch to an inch and a half are possible. this wave
will come into southern California on Wednesday and reach Colorado by
Friday morning then begin the trek northeast through the upcoming
weekend.

Weak ridging in the wake of this wave may yield a drier forecast for
Sunday over what we currently have. This will certainly be fined
tuned over the next several days as the entire holiday weekend will
not be a total washout. Some weaker waves will traverse the region
from Memorial Day through Tuesday, leading to more chances for
precipitation, but rain amounts with these look to be lighter and
less widespread.

In the meantime, the beginning of the long term (Wednesday night)
will see showers and thunderstorms moving north and east of the
forecast area as a wave exits the region. This will leave the
forecast area dry for a good part of Thursday before showers and
thunderstorms begin to sprout late Thursday night and Friday.

Both high and low temperatures will average around 10 degrees above
normal through the period. This is more representative of late June
weather.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 112 AM CDT Wed May 25 2016

SW flow aloft means energy helping generate TSRA from SODAK down
through KS will be heading this way through the night. Confidence
is increasing in a NW to SE oriented band of SHRA/TSRA moving
across MN during the morning and into WI during the afternoon.
Used a combination of the HRRR/RAP/NAM to time this activity in
to TAFs, which resulted in delaying precip onset from what the 00z
TAFs had by an hour or two. Behind this initial wave, uncertainty
in the forecast is high. There will be a lot of mid level drying
and subsidence in the wake of this mornings wave. Current thinking
is this drying and subsidence will limit storm redevelopment in
the afternoon, with extensive cloud cover limiting destabilization
and potential for seeing more SHRA/TSRA from the afternoon into
Wednesday night. Main concern with what these TAFs is they may
not be capturing the potential for a few hours of MVFR cigs in
the wake of the rain when looking at RH in the 925-850mb layer off
the RAP/NAM. Would like to see better MVFR ceiling probs in the
SREF and more clouds in that level forecast on the HRRR though
before getting too carried away with that.

KMSP...Although still a good deal of variability in the CAMS with
how widespread TSRA will be with the band moving up this morning,
there is good agreement on the 16z to 19z period being most likely
for seeing TSRA, so hit this period with a prevailing TSRA
group. After that, really don`t see much potential for SHRA/TSRA
the rest of the period.

/OUTLOOK FOR KMSP/
Thu...Mainly VFR. Chc TSRA/MVFR. Wind S to SW 5 kts.
Fri...Mainly VFR. Chc TSRA/MVFR. Wind SE 5 kts.
Sat...MVFR. TSRA/MVFR Likely. Wind SSE 5 kts.


&&

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

$$

SHORT TERM...LS
LONG TERM...RAH
AVIATION...MPG



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