Area Forecast Discussion
Issued by NWS Twin Cities, MN

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199
FXUS63 KMPX 190938
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
438 AM CDT Fri May 19 2017

.SHORT TERM...(Today and tonight)
Issued at 330 AM CDT Fri May 19 2017

The short term concern is the threat of showers lifting across
about the southern third of the cwa today...and then timing of
the next surge of rain showers later tonight. Also the frost
threat early this morning over the northeast cwa with attendant
headline.

Water vapor imagery is showing a potent short wave rotating the
broad upper southwest conus trough through central Nebraska and
Kansas this morning. Large are of convection through the mid
Mississippi River Valley with area of rain lifting into northern
Iowa. Various HIRES model solutions lift this into southern MN
during the morning. Categorical PoPs are warranted over south
south central MN for a time this morning. Further north, the dry
easterly flow will erode the rain area as it tries to move north.
The isentropic forecast indicates it saturation may work toward
the southern metro this afternoon. We will bring in slight chance
pops to near KMSP by late this afternoon, but we believe the dry
will win out over the central portion of the area today. Large
area of cirrostratus out ahead of the trough will keep mostly
cloudy conditions to the area today and will limit heating. It may
be difficult to warm into the lower 50s far south with the clouds
and expected rain.

Early this morning...we should maintain a fair amount of high
clouds over the cwa. This may limit real significant frost
formation over in much of the advisory area. Temepratures are
expected to drop through the mid and upper 30s...still cold enough
for frost. We will leave the frost headline through expiration at
8 am.

We may see a lull in overall development of rain showers into the
evening, but we do expect as the upper trough and surface low
lifts northeast into southern Iowa later tonight the rain
chances will increase rapidly in the 06z-12z Sat period across
much of the area.

.LONG TERM...(Saturday through Thursday)
Issued at 330 AM CDT Fri May 19 2017

Saturday through Monday...A well-organized mid-latitude cyclone
with an associated longwave trough nudging it along the way will
be placed over the central Plains into the mid-Mississippi River
Valley region by daybreak Saturday morning. Heightened isentropic
lift to the northwest of the low pressure center along with plenty
of deep moisture will be available to continue producing periods
of rain for much of the WFO MPX coverage area for much of the day
Saturday and Saturday night. Difficult to place any parts that
would not receive rain so PoPs in the categorical range are
maintained. QPFs may be a little on the conservative side given
PWATs over an inch so it would not be unreasonable to see rainfall
totals in some locations in the 1.0-1.5 inch range Saturday
through Saturday night. The low will take a track from northern MO
into far SW WI Saturday on its way to Lake Superior by daybreak
Sunday morning. This track keeps the warm sector (and any
potential for severe weather) off to the southeast of the WFO MPX
coverage area so for our area, we are looking at a solid rainfall
event. That said, there still may be some concerns for low-lying
and small stream water rises into and through the weekend. The
system will continue moving off to the northeast, moving into
southern Ontario province by daybreak Monday. Unseasonably cool
air wrapping around the system will maintain highs roughly 10-20
degrees below normal for the area. In addition, plenty of moisture
will still be in place for the expanding upper level low to
produce scattered rain showers Sunday night before exiting the
area by early Monday.

Monday night through Thursday...On the heels of the potent exiting
system Monday will be a weaker low pressure center with a trailing
cold front which looks to pass through this area Monday night
through Tuesday. With a more southerly flow in advance of this
cold front, more instability will be available in a modified warm
sector. In essence, the potential for isolated generalized
thunderstorms is there with this system but severe weather is not
expected due to the lack of multiple elements. Weak high pressure
will then follow for midweek, with only isolated showers possible
going into Thursday as another cold front slowly approaches from
the west. Temperatures will go on a warming trend as the week
progresses, with highs climbing back to around 70 by midweek.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1045 PM CDT Thu May 18 2017

Only change made to existing TAFs was to remove prob30s for -SHRA
at MSP and RWF. 00z NAM has come in similar to what we are seeing
with the RAP and HRRR that dry air locally will keep any rain
Friday south of the MPX terminal. Main surge of rain Friday night
looks to be coming after 06z.

KMSP...we may see MVFR cigs and -RA moving in right at the tail
end of the TAF, but with the dry air expected to be in place, felt
better about taking a slower route to the arrival of both this far
out.

/OUTLOOK FOR KMSP/
Sat...MVFR/RA with IFR possible. Wind E at 10G20kt.
Sun...MVFR. Chc -shra. Wind WNW at 15G25kt.
Mon...VFR. Chc MVFR/-shra. Wind NW at 5-10kt.


&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...Frost Advisory until 8 AM CDT this morning for WIZ014>016-025-
     027-028.

MN...Frost Advisory until 8 AM CDT this morning for MNZ043>045-052-
     053.

&&

$$

SHORT TERM...DWE
LONG TERM...JPC
AVIATION...MPG



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