Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 230843
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
343 AM CDT Sun Apr 23 2017

.SHORT TERM...(Today and tonight)
Issued at 315 AM CDT Sun Apr 23 2017

Today and tonight...Surface analysis early this morning shows a
slowly southward-sagging cold front entering northern portions of
Todd/Morrison counties (far northern peaks of the WFO MPX coverage
area) and continuing to extend nearly due E-W. The front bisects two
high pressure centers, one over the TX/OK panhandles and the other
over northern Manitoba province. Upper level flow is nearly zonal,
meaning that the front is not expected to make much more southward
progress than where it currently is. A stark difference is expected
on either side of the front, with cool northeasterly flow along and
north of the front and warm southwesterly flow south of the front.
This will create quite the temperature gradient from the northern
tier of counties to central-southern portions of the coverage area
today. While much of the coverage area starts in the lower-middle
40s early this morning, highs will range from the lower 50s in far
northern portions of the area to the lower 70s for much of the
coverage area south of the I-94 corridor. Clouds will be restricted
to near and north of where the front settles. Drier air is found not
much to the north of the front and this will help impede efforts for
precipitation to actually reach the ground. Stronger lift is located
further north with deeper moisture from H7 upwards, so better
potential for precipitation will be north of the MPX coverage area.
As such, aside from a few potential rounds of sprinkles in the far
northern counties, have kept the entire coverage area dry today. The
front will make little progress southward tonight while a developing
area of low pressure over eastern WY shifts into the Dakotas. Due to
the abundance of drier air in advance of this low, its associated
precipitation shield is expected to remain to the W of the coverage
area through tonight, though only shortly after 12z can
precipitation be expected to develop in far western MN. With clouds
on the increase tonight, this will help blanket the warm
temperatures experienced from today and keep mild temperatures in
place for lows early Monday morning. Lows will essentially range
from around 40 far north and east to around 50s in far south and
west plus the Twin Cities metro.

.LONG TERM...(Monday through Saturday)
Issued at 315 AM CDT Sun Apr 23 2017

The longer term concerns are overall timing of short wave energy
lifting northeast across the cwa through Wednesday. Then the
models drive significant energy south over the western conus
developing a large trough and generating cyclogenesis late in the
period.

Initially there is good agreement with the development of low
pressure over eastern South Dakota Monday afternoon and across
southern Minnesota Monday night. There is some thunder potential
especially over the west Monday afternoon and into the he evening
into eastern MN Monday evening as the system moves through.
Instability is marginal...but some low end SREF thunder
probabilities do move east during this period. We will mention
slight chance thunder for now.

This system exits to the east and the next wave lifts into the
region. This wave is a bit deeper and does develop stronger
forcing over the eastern cwa mainly Tuesday afternoon/Tuesday
night. There is strong Fgen associated with the trough as it
lifts northeast. Pwats increase to 0.75 to 1 inch so there good be
some heavier rain during this period as well. We currently have
0.50 to 0.70 inch totals over the eastern cwa which may have to be
increased in later updates.

This system exits Wednesday...with much colder air moving in
behind the trough. If there remains any significant moisture there
could be a rain changing to snow shower scenario with perhaps
some minor accumulation`s tuesday night over a small part of the
northern cwa. Highs Wednesday will struggle to warm through the
40s.

Cooler and dry conditions move in Thursday and lingers through
most of Friday. There may even be a little sunshine during this
period. Temperatures should moderate some...but will remain below
normal.

The deterministic models continue to develop a deep upper trough
over the western conus late in the period. Timing is a continued
problem with overall movement/development of the surface low as
the system moves east. At the moment...it appears the weekend is
in jeopardy with the ECMWF bringing in the system a bit slower
than the GFS. We will hold onto some modest PoPs for the moment
and monitor later model forecasts for future timing.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1038 PM CDT Sat Apr 22 2017

Reasoning remains similar to the 00Z forecast issuance. The main
uncertainty will be with the frontal boundary dropping south into
the area overnight into Sunday, and exactly how far south it will
progress. This will impact both wind directions and cloud cover,
and given some upstream observations it now appears that some MVFR
ceilings could occur at the northern sites for a period of time
Sunday morning, so included that at KAXN. Trends will need to be
monitored overnight and Sunday morning, and it`s likely that some
modifications will be needed, although the majority of the area is
still expected to remain VFR through the period.

KMSP...Primary uncertainty remains wind direction and timing of
changes through the day on Sunday. Wind speeds still mainly look
to be less than 10 kt, but could cause some tricky windows of time
as things shift around on Sunday to eventually settle into more of
an East to Southeast direction.

/OUTLOOK FOR KMSP/
Monday...VFR, MVFR possible late. South wind 15 to 25 kt.
Monday night...MVFR, IFR possible late. Chance of rain. South
wind 10 to 15 kt becoming west.
Tuesday...MVFR, IFR possible. Rain likely. Northwest wind 5 to 15
kt becoming north 10 to 20 kt.
Tuesday night...MVFR, IFR possible. Rain likely early. North wind
10 to 20 kt.
Wednesday...MVFR, mainly early. Chance of rain. North wind 10 to
20 kt.


&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&

$$

SHORT TERM...JPC
LONG TERM...DWE
AVIATION...


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