Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 231134
AFDMPX

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

.UPDATE...
Issued at 622 AM CDT Sun Apr 23 2017

Updated to include 12z aviation discussion below.

&&

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

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 12Z TAFS through 12Z Monday morning)
Issued at 622 AM CDT Sun Apr 23 2017

The southward-sagging cold front will wobble over MN near KAXN-
KSTC, remaining to the north of the remaining TAF sites. This will
keep these northern 2 sites with mid-level ceilings through mid-
afternoon while the other 4 sites stick with passing upper level
cirrus. As the overnight progresses into daybreak tomorrow, high
level ceilings will fill in but any and all precipitation is
expected to remain in northern MN/WI. The proximity of the front
will make for a difficult wind forecast through the first half of
the TAF period. However, speeds will remain 10 knots or less,
diminishing the impact of the direction forecast. The only other
concern is a developing strong low level jet tomorrow morning.
This will likely produce strong winds in the 1-2 kft level. The
directional change will also be roughly 40-60 degrees from the
surface, potentially producing LLWS issues at the MN TAF sites.

KMSP...No significant issues through the first half of the TAF.
Going into tomorrow, high ceilings will develop by daybreak. LLWS
conditions also look to be an issue throughout the Monday morning
push. While surface winds will be southeasterly about 10kt,
southwest winds off the deck at around 40kt are expected.

/OUTLOOK FOR KMSP/
Mon night...MVFR with IFR possible late. Chance of rain. S wind
10-15 kt becoming W.
Tue...MVFR with IFR possible. Rain likely. NW wind 5-15 kt
becoming N 10-20 kt.
Tue night...MVFR with IFR possible. Rain likely early. N wind
10-20 kt.
Wed...MVFR, mainly early. Chance of rain. N wind 10-20 kt.

&&

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

$$

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



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