Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 202014

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
314 PM CDT Sun May 20 2018

.SHORT TERM...(This evening through Monday)
Issued at 303 PM CDT Sun May 20 2018

Very dry northeasterly flow associated with the area of high
pressure across central MN has done a good job of suppressing the
cloud cover to extreme southern MN. However, the shortwave to our
southwest is going to lift northeast and eventually the cloud
shield will lift northward tonight.

Modest forcing for ascent will lift north with the wave tonight, so
pops increase from south to north as time goes on.  The hi-res CAMs
continue to advertise the possibility of few to scattered showers,
but the uninspiring lift and moisture in addition to fighting off
the very dry antecedent airmass, did not warrant any higher than
about 30% PoPs.

The main shortwave will lift through during the day tomorrow, but
the story will remain the same.  Limited omega and instability in
the latest guidance led to lowering of the PoPs and removal of
thunder mention in the forecast for tomorrow. With the upper wave
moving through, expect highs to top out in the mid to upper 60s.

.LONG TERM...(Monday night through Sunday)
Issued at 303 PM CDT Sun May 20 2018

The main concerns in the long term are the system that could bring
showers and thunderstorms Tuesday night through Wednesday.
Otherwise, the main story in the long term is the return flow
bringing warmer temperatures back into the region. Of course, an
early look ahead to next weekend as well, which could bring some
activity to the region.

Not much has changed with the forecast for Tuesday night through
Wednesday other than to slow the onset of the precip chances
slightly. With this wave, there will be some instability to work
with with deeper moisture available, but the main jet stream is
going to continue to be locked up way to our north. Shear will be
lacking during this time so while it will be possible to get a
severe storm or two, don`t expect widespread issues.

The remainder of the week looks pretty quiet but the guidance is
showing a shortwave trough moving through next weekend. Confidence
isn`t too high being so far away but it`s interesting to see the
GFS and ECMWF both showing this wave moving through on Saturday,
potentially bringing rain through as well. Again, will see how
this evolves in the coming model runs over the next several days.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 123 PM CDT Sun May 20 2018

MVFR cigs will continue to sag south this afternoon as dry
northeast winds push them down toward Iowa. Tonight, as surface
ridge shifts east, these clouds will start building back northwest
toward eastern SD. MKT/RWF look to get back into these clouds late
tonight, but SREF probs for MVFR or lower cigs show probabilities
quickly decreasing during the day Monday as these clouds try to
spread northeast during the day, so have maintained VFR cigs
everywhere else. There will also be a couple of sources of rain to
watch. One is a wave down by Omaha which will be lifting north
overnight, lifting rain into western MN, so brought a -RA mention
to RWF, with a vcsh to AXN. Second wave is the one currently over
central Neb and will come across southern MN Monday afternoon,
this may spread rain into the Twin Cities, but models are pretty
sparse with precipitation.

KMSP...Kept cigs VFR, but MVFR cigs will be possible Monday
afternoon, though heights will remain above 2k feet. There will be
two chances for some -RA, the morning with the Omaha wave and
afternoon with the central Nebraska wave. The Omaha waves look to
pass west of MSP, while forcing in the afternoon looks pretty
weak, with the NAM and GFS both dry for MSP, though we`ll likely
see a few drops in the afternoon.

TUE...MVFR cigs early, then VFR. Wind SE 5 kts.
WED...VFR with chc SHRA/TSRA late. Wind SE 5-10 kts.
THU...VFR. Chc -tsra. Wind S 5-10 kts.




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