Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1154 PM CDT Wednesday Jul 23 2014
Short term...(this evening through thursday)
issued at 309 PM CDT Wednesday Jul 23 2014
Near normal temperatures and a mostly dry forecast is still expected
in the short term with the exception of thunderstorm potential
from west central to south central Minnesota tomorrow morning.
The regional radar scope is quiet this afternoon with all the
convective activity either tied to the cold front across the
eastern Great Lakes...Ohio River valley and middle Mississippi River or
on the east side of the upper ridge embedded in the anticyclonically
rotating moisture plume and thickness diffluence in Kansas and NE. The
surface high is building across the area this afternoon...but this
high should weaken and slide east tonight. The low level jet quickly
strengthens this evening over the High Plains and the result will be
Theta-E advection into the eastern Dakotas and far western Minnesota by
sunrise tomorrow morning. The 23.12z NAM/GFS/Gem and most of the
available cam guidance from last night and this morning want to
drive any convection that forms on the nose of the low level jet south with
time and weaken the activity before it penetrates too far into
Minnesota. This would mean most of the area would remain dry
tomorrow /at least during the daylight hours/. The 23.00z European model (ecmwf) was a
bit of an outlier with the western extent of the precipitation during the
day tomorrow...the 23.12z is a little slower than its 00z
counterpart but it would still suggest chance-to-likely probability of precipitation in west
central Minnesota between 18-00z.
Long term...(thursday night through wednesday)
issued at 309 PM CDT Wednesday Jul 23 2014
The main theme for the extended period is a change from an unsettled
pattern at the beginning...to a more late Summer type pattern
with drier and cooler than normal weather scenario by next week.
Thursday night/early Friday morning will remain problematic in
terms of where the nocturnal low level jet will develop and veer during the
morning hours...which will translate to higher probability of precipitation and quantitative precipitation forecast amts in
the region. Current models indicate that the nose of the low level jet will
develop somewhere in southern Minnesota/northern Iowa Thursday
evening...with winds veering more west/west-southwest by Friday
morning...changing the maximum convergence in the low levels
across Iowa by Friday morning. Best chance/S of rainfall will occur
during this time frame...especially where the best convergence
along this low level jet remains.
After Friday morning...a surface trough will move across Minnesota/western WI
leading to some afternoon/evening shra/tsra. Best chance/S will occur late
Saturday/Sunday as the main upper low that is currently moving
into the Pacific northwest this afternoon...moves along the Canadian border
tracking some upper level energy eastward along this fast moving
west to east flow aloft Fri/Sat.
Once this feature along the Canadian border moves east of Minnesota and
begins to dig south/southeast across the eastern U.S. Our weather will turn
cooler than normal. In addition...N/NW flow aloft will mean a
drier pattern with most of the action along the Gulf Coast states
and eastern U.S.
This transition to a cooler pattern will likely continue through the
beginning of August as a strong upper ridge anomaly is currently
advertise in the extended models building off the eastern coast of
Aviation...(for the 06z tafs through 06z Thursday night)
issued at 1141 PM CDT Wednesday Jul 23 2014
Few problems expected in the near term as high pressure maintains
control of the weather across the upper Midwest through the
morning hours. The only issue may be fog development in the prone
areas especially to the east where winds will be lighter toward
daybreak. Otherwise...showers will be approaching western
Minnesota in the morning after a strong low level jet develops overnight
across the Dakotas. Still expect these showers to be diminishing
so not confident in actually seeing rain at a specific location
such as rwf...so removed the chance there. Then...a more robust
chance of precipitation comes late Thursday night which is
indicated at msp and rwf. Msp mainly because of the extra 6 hour
window. Light winds tonight will continue turning east and nearly
south through tomorrow.
Kmsp...main focus will be the thunderstorms expected in the
overnight period Thursday into Friday. Otherwise VFR conditions
expected with little changes from the previous forecast.
/Outlook for kmsp/
Thursday night...VFR. Chance MVFR conds west/ thunderstorms and rain overnight. Winds southeast at
Friday...VFR. Chance thunderstorms and rain. Winds south-southeast at 5-10kts.
Sat...VFR. Winds west at 10kts.