Area Forecast Discussion
Issued by NWS Twin Cities, MN
FXUS63 KMPX 280502 AAB
Area Forecast Discussion...UPDATED
National Weather Service Twin Cities/Chanhassen MN
1202 AM CDT THU JUL 28 2016
.SHORT TERM...(This evening through Thursday)
Issued at 335 PM CDT Wed Jul 27 2016
Showers and thunderstorms will end this evening as the upper
level wave driving the storms moves southeast. Another weak wave
will follow in its tracks and lead to an inverted surface trough
and potential for a few showers and thunderstorms across southeast
Minnesota on Thursday. Skies will be mostly cloudy to start the
day Thursday morning, but should see clearing skies toward
Early afternoon water vapor imagery together with 500 mb height and
wind showed an upper level wave across the Upper Mississippi River
Valley. Forced ascent ahead of this wave together with low level
warm air advection in a region of 1000 to 1500 J/kg, resulted in
convection across eastern MN and west central WI. PWATs on the order
of 1.5 to 1.7 inches together with a nearly moist adiabatic
profile led to efficient rainfall rates on the order of 3 to 4
inches per hour. Curved hodographs and directional deep layer
shear were favorable for supercells, and a few storms managed to
take on this supercell structure and produce severe weather. As
the evening goes on, the severe weather threat will completely
diminish, but the heavy rain threat will persist.
Looking ahead...the mid levels will dry out as the wave passes by,
but low level moisture will linger so should see low stratus
overnight with the overcast skies expected to persist through the
morning before dissipating from north to south Thursday afternoon.
This will hold back high temps in the mid-70s across the region.
.LONG TERM...(Thursday night through Wednesday)
Issued at 335 PM CDT Wed Jul 27 2016
The main concern in the extended period is the strength of the
upper ridge building next week and whether this pattern holds or
buckles as a fairly strong upper low moves across southern Canada.
Chances of precipitation past Thursday afternoon, and through the
weekend remain very low due to a dry east-northeast flow in the
low levels. Eventually winds will shift to the southeast and
bring the heat and humidity back across the Upper Midwest next
Models continue to support a long wave trough dropping
southward across the Pacific Northwest this weekend. This will
allow for the upper ridge to build through the Rockies and into
the Upper Midwest by Monday/Tuesday. 50H anomalous remain above
normal for early next week, but 70H temperatures are not as
extreme then they were during the excessive heat time period last
week. However, dew points will rise back into the 70s which means
heat indices will increase above 90-100 degrees. I would not be
surprised to see another heat advisory or warning next week. As
for the lower 70H temperatures, the chances of precipitation have
increased as the cap will be less. Although the strength of the
upper ridge breaks down slightly across the northern tier of the
country late next week, there remains some uncertainty on this
pattern change. Will continue to advertise highs in the 80s, to
lower 90s next week, but temperatures could reach the mid to upper
90s if this ridge holds on longer.
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1201 AM CDT THU JUL 28 2016
An upper low will slowly head southeast across WI through the
period with an inverted trough stretching northwest into east
central MN and west central WI. This should facilitate frequent
periods of MVFR/IFR cigs in these areas through at least early
Thursday afternoon, with some improvement possible late as drier
air moves in from the north. Scattered showers will persist in
this area through Thursday. STC will be on the western edge of
these cigs. AXN/RWF will likely remain VFR through the period.
KMSP...MVFR cigs finally firmly in place with IFR cigs not too
far to the north. Cigs will lower to IFR shortly after 06z. Visibility
should be unrestricted with 15-25 kt winds just above the surface.
/OUTLOOK FOR KMSP/
Fri...Chc MVFR early. Winds E 5 kts.
Sat...VFR. Winds SE 5 kts.
Sun...VFR. Winds SE 5-10 kts.