Area forecast discussion...updated
National Weather Service Twin Cities/Chanhassen Minnesota
738 PM CDT Tuesday Jun 18 2013
Short term...(this evening through wednesday)
issued at 408 PM CDT Tuesday Jun 18 2013
The extensive low cloud ceilings across east central and southeast
Minnesota as well as west central WI continue to lift and slowly break up
at middle afternoon. A continued trend to clear-scattered conditions is
expected once daytime heating subsides. A rather strong dew point
boundary has formed this afternoon across our far northern and
eastern County Warning Area. Dew points at 3 PM ranged from around 60 at
Cambridge...with 32 at Brainerd...Siren and Rice Lake. Really not
expecting the dry air to make its way much further south since the
surface high is over Upper Michigan and dropping slowly southeast. Surface winds
will also becoming light southeast as well. This leads to the potential for
some fog tonight across central Minnesota through west central WI where
wind speeds will be the lightest. Just patchy fog is expected at
this time.
Wednesday brings a return of instability into western and southern
Minnesota during the day. Most short range solutions show scattered shower
and thunderstorm activity by afternoon across about the western half
of Minnesota in the low level Theta-E gradient. Chance probability of precipitation were confined
to this area with dry weather indicated for the Twin Cities and
areas on east and south. Lows tonight dropping into the upper 40s
from Ladysmith to Augusta with middle to upper 50s across western
and southern Minnesota. Highs on Wednesday running from the middle 70s in
west central WI to the lower 80s near the South Dakota border.
Long term...(wednesday night through tuesday)
issued at 408 PM CDT Tuesday Jun 18 2013
Summer pattern will remain in place through the
weekend...with continuous chances for severe weather and flooding
rains. An upper level ridge currently over the High Plains of
Montana will slowly migrate eastward towards the Great Lakes
region...with an upper level low forecast to take its place over the
High Plains. This will set up southwest flow across the upper
Midwest. An area of surface low pressure will linger across the
eastern Dakotas...with moisture rich southerly flow persisting
across Minnesota and Wisconsin through the weekend. Several rounds
of showers and thunderstorms will form along a frontal boundary that
is forecast to oscillate across the County Warning Area. The European model (ecmwf) is farthest south
with is position generally along the Iowa/Minnesota border...while the Gem is
farther north along the I-94 corridor...and the GFS farther north
yet closer to the international border. The main differences are
likely due to the convective parametrization of the large scale
models. Current thinking is the GFS is not handling the convective
outflow boundary(s) southern reinforcement of the warm front...and
therefore leaned more heavily on the Gem/European model (ecmwf) solution. Precipitable water values
will be in the 1.50 to 2.00 inch range...which in near the 99th
percentile when compared with climatology. The anticyclonic flow at
300mb will support convective outflow...so a 72hr infrared loop ending on
Sunday should show plenty of deep convection developing across the
Dakotas...and tracking eastward during the overnight hours as the
low level jet veers with time. In fact use the low level jet seen in
both the h925 and h850 Plain View maps of pure wind...moisture
transport...and theta_e advection as the main diagnostic tool for
probability of precipitation. Severe weather is possible...with mainly a hail and wind
threat as most of the convection expected to be elevated at the nose
of the low level jet. Flooding is also possible with the GFS 18.12z
run showing 7 inches of run total rain through the extended period.
Even though the placement of this is likely incorrect...the fact the
models are producing this much rainfall is concerning.
Looking ahead...both the GFS and European model (ecmwf) transition to zonal flow for
next week...which should lift the precipitation into Canada and bring
seasonably hot and humid weather across the upper Mississippi River
valley region.
&&
Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 725 PM CDT Tuesday Jun 18 2013
VFR conditions expected through the period. Some fog could from
late tonight across central Minnesota into west central WI...but it will
likely be shallow and quite patchy. Kept a short visibility reduction in
for rnh and stc late tonight for the potential. A few showers or
storms may fire Wednesday afternoon across Minnesota...but potential is
too low to mention at this time. Winds will be light southeast
tonight...then strengthen and veer southerly Wednesday.
Kmsp...VFR conditions expected. Little weather impact expected through
most of Wednesday...but there is an outside chance of a late day storm.
Wind will increase southerly and could gust to nearly 20 knots
Wednesday.
/Outlook for kmsp/
Thursday...VFR. Chance of MVFR. Thunderstorms and rain likely. South-southeast winds 10 kts.
Friday...VFR. Chance of MVFR thunderstorms and rain. S winds 10-15 kts.
Sat...VFR. Chance of MVFR thunderstorms and rain. S winds 5-10 kts.
&&
Mpx watches/warnings/advisories...
Minnesota...none.
WI...none.
&&
$$
Short term...rah
long term...jrb
aviation...borghoff
