Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 210337

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1037 PM CDT Tue Jun 20 2017

.UPDATE...For 06z Aviation discussion below


.SHORT TERM...(Today and tonight)
Issued at 355 AM CDT Tue Jun 20 2017

Surface analysis early this morning shows a weak quasi-stationary
front extending from central MT eastward into west-central MN with
weak high pressure to the north and south of this front. Also
analyzed in Canada is a surface low to the east of Hudson Bay with
a southwestward trailing surface trough from this low to the
northern tip of Lake Superior. This surface low is underneath a
well-defined upper level low, rotating over Quebec province and
showing up nicely on IR and WV satellite imagery. A couple of
shortwave trough disturbances are riding the western periphery of
this low, which is interacting with a swath of deeper moisture to
produce rain showers gliding southeast on KMPX radar. The bulk of
the precipitation is near and north of the I-94 corridor and these
showers will continue to press southeastward during the remainder
of the overnight hours on into daybreak. Not looking for much as
far as rainfall, generally a tenth of an inch or less, and with
meager support near the surface through the mid-levels, trying to
get convection going will be a difficult prospect. Have maintained
isolated thunderstorm wording but confidence is rather low that
thunderstorms will develop. The showers will push off to the east
and be out of the WFO MPX coverage area by midday, allowing the
northern high pressure area to prevail. Skies will steadily clear
out, making for mostly clear conditions by this evening and
lasting through much of the early morning hours Wednesday. With
the aforementioned surface front dropping to the south and
remaining there through tonight, temperatures will continue to run
seasonably cool. Highs today will only reach the low- mid 70s
followed by lows tonight in the upper 40s to mid 50s.

.LONG TERM...(Wednesday through Monday)
Issued at 355 AM CDT Tue Jun 20 2017

The long term concerns are the convective threat developing
Wednesday/Wednesday night and the continuation of the below normal
temperature regime through the period.

Overall...deterministic models in good agreement in driving a
cold front through the cwa Wednesday night and into Iowa for
Thursday. There is a slight risk for severe convection developing
across about the southern half of the cwa mainly for Wednesday
night period. We should see some elevated thunder work east across
South Dakota Tuesday night and work east across southern MN
Wednesday. The mid level cap works into southwest MN during the
day Wednesday and should preclude any convection through 00z.
Further east...the region remains on the northeast edge of the cap
and there is some indication this could continue into Wednesday
afternoon farther to the east. We maintained the chance pops for
this scenario for now. Severe parameters increase with deep layer
shear increases to 50kts with the impulse/waa pattern Wednesday
morning. There could be at least some hail with this activity. The
main concern would be potential development along the boundary
moves into southwest MN by Wednesday evening. The cap is forecast
to erode by early evening with at least scattered severe
convection a good bet. Very unstable airmass in place with MUCAPE
forecast around 2000 J/kg... bulk shear around 50kts and best LIs
around minus 6. Large hail and damaging winds will be the main
threats. We may see a fair amount of clouds out ahead of the front
in the waa regime and may limit destabilization somewhat. We
expect at least some mid 80s over the southwest Wednesday
afternoon...and could be higher if sunshine remains prevalent.

Timing of the boundary brings it through the area Wednesday night
dropping into Iowa through bout 12z Thursday. Severe threat will
follow this front. Along with the severe weather...with PW`s
rising over 1.5 inches...locally heavy rain will be a threat is
something organized develops. The low level jet does strengthen
into the night/50kts/ and most models are indicating southeast MN
the main focus for heavier rainfall potential.

Will maintain a small chance of showers into Thursday evening
with the proximity of the Iowa front to far southern MN. Broad
northwest flow develops for the remainder of the long term...with
temperatures to remain below normal through the period. Timing of
any short waves moving through this northwest flow will give some
periodic chances for showers/isolated thunder. The best chance
for this would be later Friday into Saturday. Another chance for
more organized showers/thunder arrives later Tuesday with another
cold frontal system.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1038 PM CDT Tue Jun 20 2017

Benign weather is expected to start the period, and other than
the potential for some light fog in west central WI, no
restrictions are expected overnight. Mid/high clouds will be on
the increase Wednesday, with widely scattered showers possibly
spreading eastward across the area (while decaying) during the
morning. The more widespread activity with thunder potential as
well will arrive after 00z Thursday, when ceilings will likely
become bkn-ovc low-end VFR. Winds shift to south/southeast on
Wednesday morning, with gusts up to 20 knots possible during the

High confidence in VFR through sunrise Wednesday. Could see a few
showers Wednesday morning, but the more organized activity (with
the potential for thunder) is expected to hold off until Wednesday

Thu...Mainly VFR. Slight chc -TSRA/MVFR. Wind WNW 5-10 kts.
Fri...VFR. Wind NW 10 kts.
Sat...Mainly VFR. Slight chc -TSRA/MVFR. Wind NW 5-10 kts.




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