NASA - National Aeronautics and Space Administration

Forecast Based on

• on satellite
• current surface observations
• 00 UTC ETA
• 00 UTC NGM
• 09 UTC MAPS/RUC
• MRF
• 12z ECWMF

Synopsis

A very low amplitude ridge is analyzed over Montana and eastern Wyoming with a trough
to the east over the Mississippi Valley. The satellite loop shows these features. The
water vapor imagery shows a distinct dry slot across the Gulf. A shortwave is located
at 45N, 130W. High pressure is over the eastern Rockies. A fairly weak gradient has
formed over the midwest with the winds out of the north at 10-15 kts.

Prog Discussion

As the Pacific northwest shortwave moves on shore and through the Rockies, the upper
level ridge will flatten entirely. By 36 hours, a ridge starts to build at 135W. As
the ridge amplifies, a trough forms over the Great Basin with several shortwaves embedded
in the flow. Both the ETA and NGM form a surface east of the Rockies. The ETA forms
a surface low in TX panhandle while the NGM puts it over NE/MO. This type of pattern
will lead to strong southerly winds laden with Gulf moisture. Kansas and Oklahoma could
see some showers late Saturday night.

48 hour Forecast:

12z 26 Apr - 00Z 27 Apr: Mostly sunny. Maybe some high clouds. Highs upper 60s.
Winds light (10 kts) from the northwest.

00Z 27 Apr - 12Z 27 Apr: Increasing clouds. Lows in the low to mid 40s. Winds
out of the southwest 10-20 kts.

12z 27 Apr - 12Z 28 Apr: Breezy and mostly cloudy. High around 70. North wind
15 to 25 kts and gusty.

12z 28 Apr - 12Z 29 Apr: Good chance for showers. Lows in the mid 40s. Highs in
the mid to upper 60s.

For the long range outlook, both the MRF and the ECMWF are depicting an omega block
pattern over the eastern Pacific and west coast. A trough sets up over the Mississippi
Valley which leaves the midwest on the backside of the trough. The latest ECMWF run
goes out to May 1 and the MRF run out to May 6. Both models show the omega block
lasting through to the end of these forecast periods.

Walker and Mace