Area Forecast Discussion
Issued by NWS Twin Cities, MN

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
FXUS63 KMPX 222041

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
341 PM CDT FRI JUL 22 2016

.SHORT TERM...(This evening through Saturday)
Issued at 335 PM CDT Fri Jul 22 2016

Only concern this evening is a few isolated thunderstorms near the
Iowa/Minnesota border as the front (dry line...) has stalled. There
is also some thunderstorms in northeast South Dakota, but these
should follow the moisture gradient to the south-southeast across
southeast South Dakota and into far southwest Minnesota. However,
there is some uncertainty on when the stalled front moves back
northward overnight. So, a few thunderstorms may develop from
outflow boundaries from the storms in eastern South Dakota into
west central, and southwest Minnesota before midnight.

The main increase in precipitation coverage will occur late
tonight as the front finally lifts northward and the low level
jet increases along the strengthening theta-e gradient. This
should begin in southwest-south central Minnesota and expand
northward during the pre dawn hours. Although, typically the low
level jet lessens in the morning, which leads to an overall
decrease in thunderstorm activity, this may not be the case.
Another scenario could be the continued development of convection
forming northward during the morning as the theta-e gradient
tightens. In addition, this highly induced theta-e gradient/warm
front scenario will likely be the focus for more convection
during the afternoon in central Minnesota. This is also where the
best potential of back-building thunderstorms, and high rainfall
rates will increase the flash flood threat. Therefore, a flash
flood watch has been issued for this reason.

Models have indicated that 6 hour precipitation totals could
reach 1 to 2 inches in the watch area between 18z Saturday - 06z
Sunday. If you combine the added affects of isolated rainfall
rates of 1-2 inches per hour, you could estimate totals of 4-6
inches in the watch area before it tapers off sometime Saturday
night. Later forecast shifts can redefine the area of concern once
thunderstorms develop overnight.

.LONG TERM...(Saturday night through Friday)
Issued at 315 PM CDT Fri Jul 22 2016

The long term trends continue to show a possible heavy rain event
across the eastern cwa into Saturday night with the passage of
the upper trough and cold front. Several cams suggesting two
convective events...ongoing over the eastern cwa by 00z Sunday and
any possible redevelopment over the west during the evening with
the passage of the front. SREF 3hr calibrated severe thunderstorm
forecast shows a good likelihood of at least scattered severe
with the system. We like the HRRR exp and NMM-wrf as far as
evolution of the event. Heavy rain will remain a factor as the PW`s increase to near 2 inches ahead of the front.

The system exits the area Sunday morning with a couple of dry
days expected. The next system arrives toward Tuesday and the GFS
and ECMWF show the chance of showers and storms continue through
the end of the week. Model discrepancy/timing differences of
embedded short waves is strong enough to leave the more broad
brush approach to the the precipitation forecast at this time.
Overall...temperatures are expected to trend cooler by late in
the period as the middle conus ridge does appear to break down
more bringing in cooler Canadian air.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1230 PM CDT Fri Jul 22 2016

No aviation issues for this afternoon with any thunderstorms that
develop will be south of MPX taf sites. A light east to southeast
wind will continue through tonight, with increasing southeast
wind Saturday morning. Thunderstorms will be possible during the
last 6 hours of the taf period.


No aviation concerns through Saturday morning, or before 12z.
Thunderstorms will be possible late Saturday morning, and likely
by Saturday afternoon. Light east/southeast wind through tonight
will increase Saturday morning with a few gusts above 18 knots
Saturday afternoon.


Sun...VFR. Winds NW 10-15 kt.
Mon...VFR. Winds NW 5-10 kt.
Tue...VFR. Thunderstorms Possible. Light & Variable Wind.


.MPX Watches/Warnings/Advisories...
WI...Excessive Heat Warning until 7 PM CDT this evening for WIZ024-

     Flash Flood Watch from Saturday afternoon through Sunday morning
     for WIZ014>016.

MN...Excessive Heat Warning until 7 PM CDT this evening for MNZ054-

     Flash Flood Watch from Saturday afternoon through Sunday morning
     for MNZ043>045-050-052-053.



AVIATION...JLT is the U.S. government's official web portal to all federal, state and local government web resources and services.