Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 200909

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

.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 Tuesday night)
Issued at 1045 PM CDT Mon Jun 19 2017

Line of SHRA/TSRA that moved across eastern North Dakota earlier
this evening has fallen apart across western Minnesota. However,
additional SHRA/TSRA continue to develop in eastern North Dakota
where a strong wave is moving across the area. Areal coverage
remains the main concern this morning, especially considering the
initial band of SHRA/TSRA that fell apart. So, timing remains good
after 7-8z in west central, 8-10z in central, and 9-11z in east
central Minnesota. West central Wisconsin will see the activity
between 10-13z. Although there is a good likelihood of heavier
rainfall developing during the pre dawn hours in east central
Minnesota, coverage remains questionable. Will continue with only
P6SM -SHRA VCTS during the time frame from northwest to southeast
across MPX forecast area. After 13-15z, VFR conditions and no
aviation concerns.


Timing remains on track for SHRA/TSRA to develop near the airport
between 9-11z, with possibly a period of moderate rainfall
depending upon storm intensity. After 14-15z, VFR conditions and
no aviation concerns.


Wed...VFR. Chc -TSRA in the Aftn/Evening. Wind S 10 kts.
Thu...VFR. Chc -TSRA in the Morning. Wind WNW 5-10 kts.
Fri...VFR. Wind NW 10 kts.




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