Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Twin Cities/Chanhassen Minnesota
1051 PM CDT Thursday Oct 30 2014
Short term...(this evening through friday)
issued at 252 PM CDT Thursday Oct 30 2014
Its a classic fall day across the region today with gray skies and
north winds that are starting to kick up this afternoon. There are
two surface lows...one over northern MO and the other over Lake Superior...
with a cold front just clearing Rochester and Eau Claire at 3 PM.
Behind this front there is a 1036mb high centered over the
Manitoba/Saskatchewan border. This high will build into western Minnesota as a
1039mb high by Friday morning. As the last several forecasts have
mentioned...this will bring in the coldest air of the season thus
far...with 850 mb temperatures falling to around -10c by 12z Friday. We are
seeing strong subsidence of both the dynamic /see large positive
Omega values/ and isentropic variety...which was resulting in a
break in the stratus deck that is already moving into NE nodak and
northwest Minnesota. This clearing will work across the mpx area overnight. Did
not change lows much tonight and was hesitant to go any lower than
what the existing forecast had for lows mainly because we have spent
most of the day slowing down the drying of dewpoints. Given the
slower arrival of the drier air...think the mav/met with their upper
teen lows for tonight in west central Minnesota are a bit overdone...though
still have lows forecast in the low 20s...with everyone expected to
drop into the 20s tonight.
Beside the clouds...the development of steep lapse rates in cold air advection as
resulted in a few sprinkles falling from time to time this
afternoon. However...those reports have been few and far
between...and for the most part haven't been hard enough to even
require the use of wind shield wipers. As a result...maintained
going forecast with just some isolated shower wording lingering
across eastern areas through the evening...basically on the leading edge
of the cold air advection and out ahead of the western tail of a shortwave that will be
working across the western Great Lakes.
For tomorrow...airmass coming in will be very dry...so we will have
clear skies. 1km mixed layer dewps are in the single digits on the
NAM/GFS...so would not be surprised if we see a few pockets have
dewps mix into the single digits during the afternoon. We will see
temperatures struggle for just 40 tomorrow...which is close to what
bias corrected highs look like. Favored the bias corrected numbers
as in this recent spell of drier weather we have run a bit of cool
bias for full sun days. There is a bright spot /beside the full
sunshine/ for the weather tomorrow and it is that the high pressure
will be more or less centered over the mpx County Warning Area. Will still see
breezy conditions in the morning over WI...but by the
afternoon...wind speeds will be back down under 10 miles per hour...so at least
we will not have to deal with the blustery winds after tonight.
Long term...(friday night through thursday)
issued at 252 PM CDT Thursday Oct 30 2014
Cold high pressure drops south and east across the area Friday night
through Saturday. This will promote light winds and cold
temperatures for the entire County Warning Area Saturday morning and over the far
eastern County Warning Area into Sunday morning. Should see first real widespread
had freeze then. The high drifts to the southeast Saturday allowing
falling surface pressure to work east across the Dakotas along with
an increasing pressure gradient into western Minnesota. This should
increase the wind mainly over the western half of the area for
Saturday. Some high clouds are expected to move east Friday night
and Saturday. This will determine the overall maximum temperature
The next system moves across the area Monday and Monday night. Doesnt
appear to be a significant precipitation producer as models suggest
much of the moisture will be shunted to the east and south with the
split flow nature to the upper wave moving through. Will continue
the chance pop trends for now and see if models come into better
agreement to the movement of this system.
With the passage of this trough...the upper flow pattern becomes
more progressive and more zonal across the Continental U.S.. this will allow
fast moving fronts to move through the area. The next one is
forecast to be move in around Wednesday. We should see temperatures
warm out ahead of the front with temperatures warming into the lower
50s across much of the area middle/late next week...which is trending
Aviation...(for the 06z tafs through 06z Friday night)
issued at 1051 PM CDT Thursday Oct 30 2014
Brisk northwest winds of 15-25 knots will persist for a few more hours
before slowly waning to 10-15 knots overnight and then to less
than 10 knots Friday afternoon as high pressure builds in.
Clearing has pushed through all of the taf sites with the
exception of Keau...but the back edge of the VFR clouds will be
through this site by 06z. However...more VFR cloudiness
(bkn035-045) over northeast Minnesota will slide south-southeast overnight and
Friday. This is reinforced by the NAM cumulus rule which is quite
negative for western WI Friday morning. Hence...krnh and Keau will
likely see bkn035-045 during the morning and early afternoon.
Kmsp...VFR through the period. Scattered-bkn045 passing through during
the morning. Gusty northwest winds to 25 knots through 09z then 12-14
knots through the morning with less than 10 knots for the
afternoon and evening.
/Outlook for kmsp/
Sat...VFR. Winds southeast 10-15 kts.
Sun...VFR. Winds south-southeast 14-18 kts.
Monday...VFR. Chance MVFR cigs/shra. Winds SW 6-10 kts.