Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 271108
AREA FORECAST DISCUSSION
National Weather Service Topeka KS
608 AM CDT FRI MAY 27 2016
.SHORT TERM...(Today and Tonight)
Issued at 344 AM CDT FRI MAY 27 2016
08Z water vapor imagery shows a closed low over eastern CO with a
shortwave rotating through the base of the low. Meanwhile at the
surface, a low pressure system was analyzed over west TX with
southerly low level flow persisting over the southern plains helping
to maintain a moist airmass over the forecast area.
The forecast for today and tonight is for more thunderstorms to
develop. Models seem to think that a weak impulse, possible an MCV
from the convection over north TX, could lift across eastern KS and
cause storms to initiate by the early afternoon. Then the models
show the upper low moving east with a negatively tilted shortwave
lifting over the area this evening and overnight. With decent
moisture and cooling mid level temps, models show moderate
instability developing by the early afternoon with CAPE values
around 2000 J/kg and not much in the way of inhibition to
convection. But 0-6km shear remains somewhat marginal and storm mode
may be multi cells once again. The overall severe weather risk will
depend on how much we heat up and so the most likely timing for
severe storms will probably be during the afternoon with the initial
storms. After that, overturning of the airmass may limit severe
potential during the overnight hours. The greatest hazard appears to
be continued flooding for additional heavy rainfall today. With many
rivers already flooding or forecast to flood, will extend the flash
flood watch through tonight. Have likely POPs going for the
afternoon and evening with the main uncertainty in the extent of the
thunderstorms. Temps May struggle to get into the upper 70s due to
cloud cover. Lows tonight are expected to be in the mid 50s and
around 60 due in part from rain cooled air.
.LONG TERM...(Saturday through Thursday)
Issued at 344 AM CDT FRI MAY 27 2016
Within the warm and moist airmass still in place, the upper trough
axis slowly lifts to the northeast through the day on Saturday.
Instability at the sfc once again increases from 2 to 4000 J/KG of
surface based CAPE area wide, however highest over east central
Kansas where dewpoints in the mid to upper 60s are likely. Given
that skies will clear out for a good portion of the afternoon, could
still see some scattered storms develop in the afternoon and
evening. These storms will be on the marginally severe side given
the effective shear parameters are not very high in the 20 to 30 kt
range. Flooding concerns are once again high on the list with an
additional one to two inches possible with this wave.
There may be a temporary clearing Sunday morning where we could see
patchy fog in areas that received rainfall the previous evening.
Given the scattered nature of the convection, did not feel confident
on where to place in the forecast, but it is something to watch.
Frontal boundary trailing the exiting waves drapes over the CWA by
Sunday afternoon while a shortwave trough lifts across the region.
The GFS is the most robust with the upper forcing and therefore
precip while the NAM and ECMWF trend more towards convection being
scattered. All guidance does center the heaviest rainfall south and
west of the area, but still could see some flooding concerns.
Sufficient instability with up to 30 kts of 0-6 km bulk shear could
allow for a few strong to severe storms. Large hail, damaging winds,
and flash flooding would be the main hazards for convection this
Upper pattern stays active next week as a shortwave trough enters
the Pacific Northwest, gradually phasing with the broad southwest
trough as it lifts towards the central plains. Guidance is in good
agreement with the placement of the system, however timing and
coverage of convection is uncertain given the warm and moist airmass
and limited organized lift aloft. Best chances for seeing perhaps a
few stronger storms and heavy rainfall look to be Tuesday-Wednesday
as the trough axis nears and a cold front provides focus for
organized convection. Cooler and drier air is becoming more
apparent by Thursday.
.AVIATION...(For the 12Z TAFS through 12Z Saturday Morning)
Issued at 608 AM CDT FRI MAY 27 2016
Confidence is low in the models low level RH progs given the
current VFR conditions. Have kept the forecast VFR through the day
since upstream obs also show VFR conditions. High res models
redevelop SCT TS by 19Z or 20Z. Have continued with VCTS and later
shifts can refine timing of TS through the morning.
Flash Flood Watch through Saturday morning for KSZ008>012-