Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 271718

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1218 PM CDT FRI MAY 27 2016

Issued at 1217 PM CDT Fri May 27 2016

Updated to include 18Z aviation discussion below.


.SHORT TERM...(Today and tonight)
Issued at 333 AM CDT Fri May 27 2016

The short term concern remains the extent of shower/thunder threat
today and tonight and cloud trends.

Water vapor imagery currently showing remnants of Iowa convection
lifting north in southerly flow aloft over the central conus.
Radar has been showing some isolated activity trying to develop in
weak theta-e advection over the area, We do expect coverage to
increase during the morning..similar to trend of the Hopwrf mean
as the wave lifts out to the north. We will continue the trend of
likely pop as it moves through. There should be some break in the
overall coverage of any showers into the afternoon from the
south...and this should linger into the evening. Cloud cover is
expected to remain much of the day as moisture continues to stream
north. This should limit heating somewhat and help keep
temperatures into the low-mid 70s and keep the severe weather
threat low for the cwa.

The upper trough to the southwest is forecast to lift northeast
later tonight and should begin to generate more widespread activity
mainly late tonight.  We will increase pops once again after 06z
sat...into central MN by 12z. QPF forecast should range around three
tenths of an inch to the west and up to three-quarters of an inch to
the east through tonight.

.LONG TERM...(Saturday through Thursday)
Issued at 333 AM CDT Fri May 27 2016

The long term period will begin with a significant closed upper
low/short wave lifting slowly northeastward across the forecast
area. This feature has been well advertised and remains in great
agreement between the various deterministic solutions. Hence,
showers are likely with thunderstorms developing during the
afternoon and continuing for a time Saturday evening. Rain amounts
from a half to three-quarters of an inch are likely as well. A
concern on Saturday is a potential bust with the high
temperatures. 850mb temperatures are only in the 12 to 14 deg C
range. With a very moist column, it may be hard to get past the
upper 60s to lower 70s from west to east. Therefore, trimmed back
the highs into the lower to middle 70s which still may be on the
warm side but it does leave some room in case the showers are not
as widespread as forecast and some breaks in the clouds occur.

This wave will exit the area on Sunday with weak surface ridging
and height rises aloft. The day may be pretty much dry. The fly-
in-the-ointment is the instability that develops across the area
during the afternoon with SBCAPE from 1000-1500 j/kg along with
the best LI from -4 to -6. A small disturbance is seen in the
westerly flow that may trigger a few afternoon showers and
thunderstorms. On Memorial Day, the instability is farther south
along the IA border. Pushed pops a little more to the south with a
dry forecast from the Twin Cities on northward.

Another strong wave will impact the region from Tuesday through
Wednesday with another slug of rainfall. This feature comes at us
from the Pacific Northwest. The ECMWF is faster and deeper with
this feature over that of the GFS. The GEM sides more with the GFS
on this one. Rain amounts from 1 to 1.5 inches are possible,
especially from south central Minnesota through the Twin Cities
and west central Wisconsin. The month of May and the start of
June will end/begin on a wet note.

A drying trend will occur in the wake of this feature with deeper
northerly flow aloft developing due to an expanding ridge across
the western United States. Sunday and Monday will be the warmest
days with highs from the upper 70s to lower 80s.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1217 PM CDT Fri May 27 2016

MVFR and some IFR will predominate through he period as the
surface trough lingers over the area and a few weak shortwaves
move through. Main windows for poor conditions look to be this
afternoon, with some improvement from late afternoon into this
evening, then again late tonight and Saturday morning. Stuck
fairly close to timing of LAMP guidance, but in general did not go
quite as pessimistic with the specifics. Thunder is a possibility,
but doesn`t look sufficiently likely to include at this point,
especially with the better chances for that looking like they`d
occur with the precipitation late tonight/Saturday morning.

KMSP...Have reasonable confidence in the overall forecast and
timing, but do believe it`s possible that conditions could be a
bit worse with both ceiling and visibility in the 09Z-15Z time
period, so subsequent forecasts may need to adjust.

Saturday night...MVFR ceilings possible. Northwest wind 5 to 10
Sunday...VFR, but brief MVFR possible with a chance of showers and
thunderstorms. West wind 5 to 15 knots.
Sunday night and Monday...VFR. Variable wind less than 10 knots.
Monday night and Tuesday...MVFR ceilings and visibilities expected
with a chance of showers and thunderstorms. Southeast wind 10 to
15 knots.


.MPX Watches/Warnings/Advisories...


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