Area forecast discussion
National Weather Service Grand Forks ND
306 PM CDT Wednesday Jun 19 2013
Short term...(this evening through Thursday night)
issued at 306 PM CDT Wednesday Jun 19 2013
Main issue throughout the period will be chances and strength of
convection.
WV loop and upper air analysis have the Main Ridge over the
northern plains...although there are some weak embedded shortwaves
moving through the Dakotas under the ridge axis. Southeasterly
winds have developed over the southern and western County Warning Area along the
front side of a surface trough extending from southern Alberta into
western South Dakota. Many of the models have convection moving into our
southern counties tonight along the shortwave currently moving
through South Dakota. There has been some decent cumulus developing to our south
and west. Models have been overestimating surface moisture
though...particularly the GFS and NAM which have dew points this
afternoon in the middle 60s and they have been in the 50s in reality.
Think there will be some scattered thunderstorm activity tonight
as that weak shortwave comes out. However...with very weak shear
do not think there will be much in the way of severe.
Another weak shortwave trough will be lifting into the northern
plains tomorrow. Much of the development tomorrow will depend on
exactly how convection tonight plays out. Think there should be
enough clearing for destabilization. With continued southeasterly
winds there should be better moisture...although the NAM and GFS
have near 70 dew points and are probably overestimating. Will
continue to keep high probability of precipitation and with the possibility of 2000 j/kg
of cape there could be some activity that becomes severe Thursday
afternoon. The convection will continue to move eastward through
the Minnesota counties through Thursday night so kept probability of precipitation high.
Long term...(friday through wednesday)
issued at 306 PM CDT Wednesday Jun 19 2013
The chances for convection continue through Friday and Saturday
as southwesterly flow aloft continues along with minor shortwaves.
It is difficult to pinpoint such small scale features this far
out. However...most of the models seem to be latching onto a more
significant shortwave coming through Friday night and Saturday.
Thus...kept probability of precipitation a bit higher during that period than during the
day on Friday where there could be a bit of a lull in activity
although completely dry is not guaranteed. Temperatures will continue to
be warm with highs in the upper 70s to 80s and lows in the 60s.
Saturday night-Wednesday...
an active weather pattern will continue across the northern plains
during this period. The 12z GFS/European model (ecmwf) are in general agreement in
lifting the main trough towards the southern Canadian prairies on
Sunday...while the Gem is much farther south. By Monday...the
operational models suggest a more zonal flow pattern
developing...with the European model (ecmwf) showing the forecast area on the
periphery of a developing middle/upper level ridge across the High
Plains by the middle of next week. Temperatures will continue to
remain near or a bit above normal...with highs in the 70s and
80s...and lows in the 50s and 60s.
Maintained some probability of precipitation through most periods...as confidence is low on
timing precipitation chances during any given period. At this point the
best rain chances appear to be with the passage of the upper trough
Sat night into Sunday. Thereafter...the timing of embedded shortwave
troughs in the quasi-zonal flow and the location of low-level
boundaries/greater moisture transport will determine where/when
better rain chances will be.
&&
Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 1249 PM CDT Wednesday Jun 19 2013
High cirrus and some cumulus will affect taf sites through
the afternoon...with all sites remaining VFR. Isolated/scattered showers/storms
are possible this afternoon and tonight...but with low chances of
any given site seeing rain...will not include in tafs. Winds will
generally be southerly around 10kts this afternoon...before
gradually becoming more southeasterly this evening as low pressure
develops over the northern rockies. Winds may become light/variable
this evening...especially towards kbji. Showers/thunderstorms may
begin to increase towards the end of the period...but will not
include yet in the tafs due to uncertainty in timing.
&&
Fgf watches/warnings/advisories...
ND...none.
Minnesota...none.
&&
$$
Short term...Jr
long term...Jr/makowski
aviation...makowski
