Area forecast discussion
National Weather Service Grand Forks ND
1155 PM CDT Sat may 25 2013
Update...
issued at 1155 PM CDT Sat may 25 2013
Water vapor loop indicated an upper level jet moving into western
South Dakota. Thunderstorms over south central ND have decreased a bit however
precipitation area continues to plod east. No changes to probability of precipitation this
update. Also no changes to temperatures for the rest of the night.
Update issued at 959 PM CDT Sat may 25 2013
MUCAPES were highest under highest precipitable water axis and trail
off to zero in the western zones.
Area radars showed strongest cells remain over south central ND and
were turning right toward best moisture feed. Otherwise precipitation
continues to March east into the forecast area. Tweaked probability of precipitation in the
west and south overnight...a little higher and farther east.
Satellite indicated plenty of clouds across the forecast area with
blow off from thunderstorms. Increased the overnight low a bit.
Update issued at 659 PM CDT Sat may 25 2013
Storms over central and southwest ND have generally weakened as they
move east. Will keep probability of precipitation going in the western zones tonight. Storms
were generally under the higher precipitable water axis and in the
700 Theta-E axis or the eastern gradient. Little change to this
update. Will check things for next update.
&&
Short term...(this evening through Sunday night)
issued at 320 PM CDT Sat may 25 2013
Forecast challenge concerns mainly rain chances and temperatures.
Models continue to trend to over doing quantitative precipitation forecast so far. Convection
persists across western into the central Dakotas just barely
crossing Missouri River. As short wave ridge over forecast area shifts
gradually east middle level flow becomes more SW with time. As a
result convection may be able to gradually propagate farther east.
Generally trended a slow eastward progression of probability of precipitation although
with main convergence to our west not sure how convection will
hold together so kept probability of precipitation low. Low level moisture flux
gradually increasing which will hold temperatures up.
Rain chances Sunday-Sunday night also in question as low level forcing
remains well to our west so again how far east can convection
propagate. Maintained current probability of precipitation but at this time not enough
confidence to increase. NE third of forecast area to remain rain free longest with
drier air in place. Similar to today cloud cover will have a big
impact on temperatures. Thermal profiles do not change much so
probably not a big change in temperatures. Models do maintain low
level moist layer although convective temperatures much higher.
Long term...(monday through saturday)
issued at 320 PM CDT Sat may 25 2013
As surface low pressure drifts gradually east will see better
chances for precipitation for the early start of the week. Column warms
along with increase in instability to T to be more prominent.
Depending on solar temperatures look closer to average.
Guidance in agreement with pronounced southwest flow aloft from the
Southern Plains to the upper Midwest. They also agree on a closed
low somewhere over the region by days 6/7. This is indicated by both
the operational models and GFS ensembles. The European model (ecmwf) is more vigorous
with the low with a Dakotas placement...while the GFS is more
progressive driving the circulation into Ontario by Saturday.
At the surface this should translate to an active period with
several convective episodes Tuesday night through Thursday...with
more of a light rain or showers regime for the end of the
week...perhaps slackening or ending by Saturday. Temperatures will
be near seasonal norms during the afternoons...above normal for the
cloudy overnights.
&&
Aviation...(for the 06z tafs through 06z Sunday night)
issued at 1155 PM CDT Sat may 25 2013
MVFR ceilings around 15 hundred feet has moved into the southwest zones
and lower ceilings should continue moving to the northwest. Fog
loop/surface observation indicated VFR ceilings of 5-7 thousand feet over east
central and southeast Minnesota. The VFR deck can no longer be seen on
satellite as thunderstorm blow off masks lower cloud deck.
Expect Minnesota VFR cloud deck to also move to the northwest into the
forecast area tonight and sun. So much of eastern ND should remain
in MVFR/IFR conditions while much of northwest Minnesota will remain under
VFR ceilings through sun. Expect MVFR/IFR ceilings to shift into Minnesota late Sun
afternoon and into the evening as moisture transports more northward.
&&
Fgf watches/warnings/advisories...
ND...Flash Flood Watch through Sunday afternoon for ndz008.
Minnesota...none.
&&
$$
Update...hoppes
short term...voelker
long term...Rogers/voelker
aviation...hoppes
