Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 192036

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
336 PM CDT MON SEP 19 2016

.SHORT TERM...(This evening through Tuesday)
Issued at 330 PM CDT Mon Sep 19 2016

We will spend the short term portion of the forecast on the southern
edge of a 120kt jet streak up along the international border. This
will continue to send mid level impulses our direction. One came
through this morning and is already working through southern
Wisconsin. The next is working across Wyoming and will be working
into western MN late tonight. This will bring another reinforcing
shot of mid level clouds for Tuesday, and like today we will see
some high based showers. The HRRR shows light rain moving into
western MN around 12z, with the NAM/NMM/ARW showing this band
lifting northeast across central MN through the morning on a push of
isentropic forcing on the 305/310k surfaces. We did add some chance
pops from western into central MN Tuesday morning for that. By the
afternoon, 925-850 moisture transport starts to increase in SW MN as
the LLJ begins its strengthen. Though the heavier precip and bulk of
the thunderstorms are expected Tuesday night, the GFS/ECWMF are
kicking off some light QPF on the nose of the LLJ by Tuesday
afternoon. For now, maintained a dry forecast there as moisture
depth looks lacking, with deep moisture arriving for the start of
the long term period.

Across central MN, we have seen dewpoints mix out into the upper
30s/lower 40s this afternoon, and with winds remaining light tonight
with skies being clear, we should see temperatures drop off pretty
quick. Dropped lows in central MN into western WI down into the 40s.
This dry air also looks to keep fog at bay, unless you are by a warm
body of water. For Highs tomorrow, airmass is similar to what we
have today, so it will be another pleasant day with highs in the

.LONG TERM...(Tuesday night through Monday)
Issued at 330 PM CDT Mon Sep 19 2016

Heavy rainfall and possible flooding remain the primary weather
threats Tuesday night into Thursday. Wednesday and Wednesday
night still look to be the higher risk periods. Coverage area
also looks to be in the vicinity of the warm front/stationary
frontal boundary across southern MN into WI.

Models suggest surface warm front lifting into far southern
Minnesota later Tuesday night decent moisture return with the
25-35kt LLJ. This should be strong enough to generate
thunderstorms into southern MN and high pops were retained. Some
risk of large hail with thunderstorm development Tuesday night with
steep mid level lapse rates and modest instability/shear. Heavy
rainfall is also a threat...but areal coverage may not be that
widespread...affecting mainly south central MN.
Nevertheless...PW`s increase with the warm front so if training of
storms develops...heavy rain will be a threat.

The better chance of more widespread heavy rainfall looks to be
Wednesday into Thursday with PW`s enriched with some tropical
moisture from then Tropical Depression Paine. This increases PW`s
to at least the 90th percentile. So WPC`s outlook of increased
risk of excessive rain looks good during this period. Held off on
watch at the moment to better determine overall coverage area that
will be affected. Still looks like widespread 1 to 3 inches of
rain with locally higher amounts possible...especially if training
along the front develops across southern MN.

The front is still forecast to drop southeast as the upper trough
moves through. THis should leave an overall lull in the rain
threat until mainly Later Friday into Saturday night. A more
amplified pattern is suggested with the models with the next
frontal passage forecast to move through Saturday night into
Sunday night. This system looks this should limit
overall heavy rain/flood threat.

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 111 PM CDT Mon Sep 19 2016

Cold front has just cleared EAU and precip will be going with. Outside
of a few mid level clouds, skies will be skc until late tonight
when wave currently over Wyoming brings another batch of mid levelclouds
in Tuesday morning. Some indications we may have another batch of
light rain/sprinkles as well, though moisture looks even higher
up than what we saw today.

KMSP...Wind direction will be tough to pin down the first couple
of hours, but the light winds will settle to SW this evening and
becoming increasingly southeastern during the day Tuesday.

Wed...MVFR/Chc IFR. TSRA likely. E wind 5-15 kts.
Thu...MVFR/IFR. Chc of TSRA. NE wind 5-10 kts.
Fri...MVFR/IFR. Chc TSRA. E wind 7-10 kts.


.MPX Watches/Warnings/Advisories...


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